- Email: [email protected]
Effect of glazing and rosemary (Rosmarinus officinalis) extract on preservation of mud shrimp (Solenocera melantho) during frozen storage
Accepted Manuscript Effect of glazing and rosemary (Rosmarinus officinalis) extract on preservation of mud shrimp (Solenocera melantho) during frozen storage Jing Shi, Yutian Lei, Huixing Shen, Hui Hong, Xunpei Yu, Beiwei Zhu, Yongkang Luo PII: DOI: Reference:
S0308-8146(18)31458-4 https://doi.org/10.1016/j.foodchem.2018.08.056 FOCH 23397
To appear in:
Food Chemistry
Received Date: Revised Date: Accepted Date:
25 February 2018 10 August 2018 13 August 2018
Please cite this article as: Shi, J., Lei, Y., Shen, H., Hong, H., Yu, X., Zhu, B., Luo, Y., Effect of glazing and rosemary (Rosmarinus officinalis) extract on preservation of mud shrimp (Solenocera melantho) during frozen storage, Food Chemistry (2018), doi: https://doi.org/10.1016/j.foodchem.2018.08.056
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Effect of glazing and rosemary (Rosmarinus officinalis) extract on preservation of mud shrimp (Solenocera melantho) during frozen storage
Jing Shia, Yutian Leib, Huixing Shenc, Hui Hongb, Xunpei Yud, Beiwei Zhua,e, Yongkang Luoa,b,*
a
Beijing Advanced Innovation Center for Food Nutrition and Human Health, China
Agricultural University, Yuanmingyuan West Road 2, Beijing 100193, China b
Beijing Laboratory for Food Quality and Safety, College of Food Science and
Nutritional Engineering, China Agricultural University, Beijing 100083, China c
College of Science, China Agricultural University, Beijing, 100083, China
d
Zhejiang Tianhe Aquatic Products Co., Ltd, Taizhou, 318000, China
e
School of Food Science and Technology, Dalian Polytechnic University, National
Engineering Research Center of Seafood, Dalian, 116034, China
*Corresponding Author. Tel./Fax: +86-10-62737385 E-mail: [email protected]; [email protected]
1
Abstract In this study, glazing with water and rosemary (Rosmarinus officinalis) extract were applied on frozen mud shrimp (Solenocera melantho) and stored at -20 °C for 24 weeks. Quality loss and protein and lipid changes of shrimp were evaluated by total volatile basis nitrogen (TVB-N), drip loss, moisture distribution, sulfhydryl content (SH), disulfide bond, intrinsic fluorescence intensity, lipid content, free fatty acids (FFA), peroxide value (PV), fluorescent compounds and sensory characteristics. Results showed that unglazed mud shrimp exhibited significant quality decline after 16 weeks of frozen storage. Glazing treatment significantly reduced quality loss, protein degradation, and lipid oxidative damage of shrimp during the 24 weeks of frozen storage, compared to the unglazed control sample. Glazing with rosemary extract was more effective in controlling quality changes in frozen mud shrimp with lower TVB-N, drip loss, PV, FFA and higher lipid content and sensory scores.
Key words: Mud shrimp; Rosemary extract; Glazing; Frozen storage; Protein changes; Lipid oxidation
1. Introduction Shrimp is one of the most popular seafood consumed in China and around the world. Normally, harvested sea shrimp is stored by freezing to minimize bacterial growth and loss of nutrition, because of its highly perishable properties (Yerlikaya, Gokoglu, & Topuz, 2010). However, protein denaturation, lipid oxidation, and 2
sublimation and recrystallization of ice crystals still occur during prolonged frozen storage, which results in deterioration of quality in shrimp, such as discoloration, off-flavors, rancidity, dehydration, and drip loss (Baron, KjÆrsgård, Jessen, & Jacobsen, 2007; Haghshenas, Hosseini, Nayebzadeh, Kakesh, Mahmoudzadeh, & Fonood, 2015). Previous study has reported that lipid hydrolysis and oxidation and protein denaturation occurred in seafood during frozen storage had an important influence on product acceptability (Tironi, Tomás, & Añón, 2010). To protect the quality of shrimp from the effects of dehydration and oxidation during frozen storage, the application of a layer of ice on the surface of frozen shrimp by dipping has been widely used (Mesarčová et al., 2013). The ice layer can act as a barrier to control moisture transfer and oxygen uptake in the surface of frozen foods (Solval, Espinoza Rodezno, Moncada, Bankston, & Sathivel, 2014). In addition, several kinds of glazing materials have been investigated to improve quality of frozen seafood products, such as protein hydrolysate (Taheri, 2015), muscle press juice (Cavonius & Undeland, 2017), essential oils (EmİR ÇOban, 2013), and natural compounds (Mesarčová et al., 2013). With the advantages of safety and antioxidative activity, natural compounds have attracted more attention and being extensively studied in seafood preservation (Mesarčová et al., 2013). Rosemary (Rosmarinus officinalis), a woody aromatic herb, has been recognized for both its use as food flavoring and antioxidant (Seabra, Damasceno, Andrade, Dantas, Soares, & Pedrosa, 2011). The high antioxidant activity of rosemary is primarily due to certain compounds, including phenolic diterpenes, 3
carnosic acid, carnosol, and rosmarinic acid (Rocío Teruel, Dolores Garrido, Espinosa Vicente, & Linares, 2015). Several studies have investigated the application of rosemary extract on quality control of aquatic products during storage. Sarabi, Keramat, and Kadivar (2017) reported that rosemary extract is more effective in controlling lipid oxidation in fried escolar (Lipidocybium flavobrunium) fish fillets compared with Butyrate hydroxyl toluene (BHT). Li, Hu, Li, Zhang, Zhu, and Li (2012) evaluated the coating effects of rosemary extract combined with chitosan on the storage quality of large yellow croaker (Pseudosciaena crocea). In shrimp, Seabra et al. (2011) reported that dehydrate rosemary could improve the quality of frozen peeled white shrimp (Litopenaeus vannamei). Cadun, Kışla, and Çaklı (2008) assessed the antioxidant activity of rosemary extract on marinated deep-water pink shrimp (Parapenaeus longirostris) and the results showed that rosemary extract helped to prolong the shelf-life of marinated shrimp. However, there are only few reports about the effect of rosemary on shrimp quality improving. The application of rosemary extract combined with glazing technique to control quality changes in shrimp during frozen storage have not been reported. The objective of this study was to evaluate rosemary (Rosmarinus officinalis) extract as a glazing material for mud shrimp (Solenocera melantho) preservation, especially its effects on quality changes, protein denaturation, and lipid oxidation during frozen storage. 2. Materials and methods 2.1 Preparation of glazing solution containing rosemary extract 4
Rosemary (Rosmarinus officinalis) extract was purchased as dry powders from Zhengzhou Wanbo chemical products Co., Ltd (Purity≥95%, Zhengzhou, Henan province, China). The glazing solution was prepared by dissolving rosemary extract (0.2%, w/w) in potable water, mixed thoroughly by a magnetic stirrer at room temperature. The water solution of rosemary extract was kept at 0 °C before used for glazing for shrimp. 2.2 Materials and samples Mud shrimp (Solenocera melantho) (11.555.11 g) were captured in the East China Sea, mixed with ice and transported to the laboratory immediately. Upon arrival, several shrimp samples were separated and analyzed as initial fresh shrimp (week 0). The remaining shrimp were washed, drained for 3 min, and put on stainless steel plates. The placed shrimp was frozen in a refrigerator at -40 °C for 24 h, to make the center of shrimp reached -20 °C rapidly. Then samples of frozen mud shrimp were removed from the refrigerator and divided randomly into three groups: the unglazed group (UG) was set as control, water-glazed (WG) group was glazed with potable water, and rosemary-glazed (RG) group was glazed with solution of rosemary. 2.3 Glazing of mud shrimp and frozen storage The frozen mud shrimp (approximately 150 g per batch) in the WG group and RG group were weighed (W1) and dipped into prepared water and 0.2% of rosemary solution (0 °C, 10~15 s), respectively. After dipping, the shrimp were drained for 1 min and weighed again (W2). The dipping times were adjusted to achieve a similar glazing percentage (15% ± 2%) in all batches of shrimp samples. The percentage of 5
glazing was calculated following Equation (1), where W1 and W2 indicate the weight of shrimp samples before and after glazing application. (1) Each batch of glazed (WG and RG groups) and unglazed (UG group) samples was packed in a polyvinyl chloride bags and stored at -20 °C for 24 weeks. Three bags of shrimp sample in each group were taken randomly for analysis at each sampling time. Before analysis, shrimp samples in bags were thawed in running water for 1~2 hours. The ice-glaze of glazed shrimp samples was removed gently during thawing process, in order to prevent shrimp samples from being immersed in melted water or solution of rosemary extract for so long time as to cause further quality changes. All determination was performed in triplicate. 2.4 Determination of total volatile basis nitrogen (TVB-N) and drip loss The TVB-N was determined using the method of semi-micro steam distillation according to the method of Xu, Liu, Wang, Hong, Yu, and Luo (2016). The drip loss was estimated using the method of Soares, Oliveira, and Vicente (2015) with some modifications. Each bags of thawed shrimp samples were taken out, blotted with filter paper and weighed the present weight. The drip loss of shrimp samples was calculated by the following equation (2), where W3 indicates the initial weight of shrimp samples without glazing and W4 indicates the weight of thawed shrimp samples. (2) 2.5 Low field nuclear magnetic resonance (LF-NMR) analysis LF-NMR measurements were performed using a Niumag Benchtop Pulsed NMR 6
Analyser PQ001 (Niumag Electric Corporation, Shanghai, China) with a resonance frequency of 23.0 Hz, according to the methods of Li, Jia, Zhang, Wang, et al. (2017) with some modifications. Briefly, shrimp samples were cut into cubes (1×1×1 cm) and placed in cylindrical glass tubes, and then inserted into the LF-NMR probe one by one.
The
transverse
relaxation
time,
T2,
was
measured
using
the
Carr-Purcell-Meiboom-Gill (CPMG) sequence with a τ-value of 120 μs. Data were acquired from 5000 echoes of 8 scan repetitions and analyzed by MultiExp Inv Analysis software from Niumag Electric Corporation. Three relaxation times (T 2b, T21, and T22) and the percentage of each corresponding relaxation component (P2b, P21, and P22) were obtained as outputs. 2.6 Determination of protein degradation and oxidation 2.6.1 Preparation of the myofibrillar protein Myofibrillar protein (MFP) was prepared according to the method of Kong et al. (2016) with some modifications. Two grams of minced shrimp was mixed with 15 ml of cold distilled water and homogenized for 1 min. The homogenate was extracted at 4 °C for 30 min and then centrifuged at 14000 g for 10 min. The washing step was repeated using the 15 ml of cold 0.3% NaCl (instead of water) to extract more water-soluble substances. Then, the precipitate was mixed with 30 ml of Tris-maleate buffer (0.6 M NaCl-20 mM Tris-maleate, pH 7.0) and homogenized for 10 s. The homogenate was skept at 4°C for 1 h to extract myofibrillar protein and then centrifuged at 14000 g and 4°C for 10 min. The supernatant was collected and washed with four volumes of cold distilled water. After centrifugation at 14000 g and 4°C for 7
5 min, the precipitate of MFP was obtained and dissolved in chilled 0.6 M NaCl. The protein concentration of the MFP solution was determined by Biuret assay (Wu, Wang, Luo, Hong, & Shen, 2014) and adjusted to 4 mg /ml. 2.6.2 Total sulfhydryl (SH) content Total sulfhydryl (SH) content was determined using 5, 5’-dithio-bis (2-nitrobenzoic acid) (DTNB) and following the method of Kong et al. (2016). Briefly, 0.5 ml of the MFP solution (4 mg/ml) was mixed with 4.5 ml 0.2 M of Tris-HCl buffer (8 M urea, 2% SDS, 10 mM EDTA, pH 8.0). Then, 4 ml of the mixture was added to 0.5 ml of 0.1% DTNB in 0.2 M of Tris-HCl buffer (pH 8.0) and incubated at 40 °C for 25 min. The absorbance was measured at 412 nm using a UV-2600 spectrophotometer (Unico Instrument Co., Ltd, Shanghai, China). The SH content was calculated from the absorbance using the molar extinction of 13600 M -1 · cm-1 and expressed as mol/105 g protein. 2.6.3 Disulfide bond content The disulfide bond content was determined using 2-nitro-5-thiosulfobenzoate (NTSB) and according to the method of Lu, Wang, and Luo (2017). A 0.5 mL of MFP solution (4 mg/ml) was mixed with 4.5 ml of 0.2 M Tris-HCl buffer (8 M urea, 1% SDS, 3 mM EDTA, pH 8.0). Then, 4 ml of the mixture was added to 0.5 ml of 10 mM NTSB in 0.2 M Tris-HCl buffer (8M urea, 3mM EDTA, 1% SDS, 0.1 M Na2SO3, pH 9.5) and incubated at 40 °C for 25 min. The absorbance was measured at 412 nm using a UV-2600 spectrophotometer. Disulfide bond content was calculated using the molar extinction of 13600 M-1 · cm-1 and expressed as mol/105 g protein. 8
2.6.4 Intrinsic fluorescence intensity (IFI) Intrinsic fluorescence was measured as described by Lina, Yanshun, Qixing, Wenshui, and Chunjiang (2013) with minor modification. Diluted MFP (0.05 mg/ml) in 0.6 M NaCl solution was scanned using a F97 fluorescence spectrophotometer. Intrinsic fluorescence spectroscopy was obtained between 300 and 400 nm at an excitation wavelength of 295 nm with a scanning speed of 1000 nm/min. The excitation and emission slit widths were 10 nm. 2.7 Determination of lipid oxidation 2.7.1 Lipid extraction The lipids were extracted according to the method described by Kong et al. (2016) with some modification. Briefly, 35 g minced shrimp meat was homogenized with 35 ml of chloroform and 70 ml of methanol for 2 min. After that, an additional 35 ml of chloroform and 35 ml of distilled water were added and the mixture was homogenized again for 30 s. Then, the homogenate was vacuum filtered and the residue was washed with 35 ml of chloroform. The filtrate was then transferred to a separating funnel and allowed to stand for several hours until divided completely. The organic phase was collected from the bottom of the funnel and dried under nitrogen. The obtained lipids were kept in a desiccator until (~ 12 h) further experiments. The total lipid content was expressed as g/100g sample. 2.7.2 Free fatty acid (FFA) Free fatty acid (FFA) content of lipid extract was determined according to the method of Sánchez-Alonso, Carmona, and Careche (2012). Lipid sample (0.05~0.1 g) 9
was dissolved in 5 ml of toluene and then treated with 1 ml of 5% (w/v) cupric acetate-pyridine reagent (pH 6.0). The mixture was vortex for 2 min and then centrifuged at 3000 rpm for 5 min at room temperature. The absorbance of the upper layer was measured at 715 nm, and the FFA content was expressed as g FFA/100 g lipid. 2.7.3 Peroxide value (PV) Peroxide value (PV) was measured according to the method of Soyer, Özalp, Dalmış, and Bilgin (2010) with some modification. The lipid sample (0.01-0.3g) was dissolved in 9.8 ml of chloroform-methanol (7:3, v/v) and mixed for 4 seconds. The mixture was added with 0.05 ml of 30% ammonium thiocyanate and mixed for 4 s. Then 0.05 ml of 3.5 g/l ferrous chloride in 10 M HCl was added and mixed again for 4 s. After 5 min standing at room temperature, the absorbance was measured at 500 nm using a UV-2600 spectrophotometer. The PV was expressed as milliequivalents (meq) of peroxide/kg lipid, and a reference curve was plotted using ferric chloride standard. 2.7.4 Fluorescent compounds (FC) Formation of fluorescent compounds (FC) was determined in the aqueous phase obtained during the lipid extraction and following the method described by Rodríguez, Cruz, Paseiro-Losada, and Aubourg (2012). Fluorescence formation was studied at an excitation/emission wavelength of 393/463 nm and 327/415 nm. The relative fluorescence (RF) was calculated as RF=F/Fst, where F is the fluorescence of sample measured at each excitation/emission maximum, and Fst is the fluorescence intensity 10
of quinine in sulphate solution (1 μg/ml, 0.05 M H2SO4) at the corresponding wavelength. The FC was expressed as the fluorescence ratio (FR) and the FR was calculated as the ratio between the two RF values: FR=RF393/463nm/RF327/415nm. 2.8 Sensory analysis Sensory analysis of shrimp samples was performed as described by Xu, Liu, Wang, Hong, and Luo (2017) with some modifications. An assessment sheet was previously developed by a six-member laboratory trained panel based on a six-point scale ranging from the best to the worst characteristics. After thawing, shrimp samples were evaluated with five parameters (color, odor, texture, morphology, and cooking test). For the cooking test, sensory assessment was based on the flavor, taste, and broth turbidity. Radar maps were made to visually represent the sensory analysis results of mud shrimp samples. 2.9 Statistical analysis Experimental data was analyzed by using Microsoft Office Excel 2010 software. The SPSS 18.0 for Windows was used to perform analysis of variance (ANOVA). Statistical significance was reported as a level of P < 0.05. 3. Results and discussion 3.1 Changes in TVB-N TVB-N has been used as a common and important parameter of the seafood quality because its increase is related to spoilage by bacteria and activity of endogenous enzymes (Yuan, Lv, Tang, Zhang, & Sun, 2016). The limit of TVB-N content in sea shrimp as acceptable for human consumption is usually 30 mg/100 g. Changes in 11
TVB-N values of shrimp samples during frozen storage are presented in Fig. 1a. The initial TVB-N value of fresh shrimp was 7.84 mg/100 g averagely. TVB-N of all shrimp samples increased slowly at the first 16 weeks of storage and then increased sharply. After 24 weeks of frozen storage, unglazed sample present a value of 28.48 mg/100 g, almost reaching the acceptable limit level of 30 mg/100 g, while water-glazed and rosemary-glazed samples increased to 24.08 and 19.23 mg/100 g, respectively. The increase in TVB-N values was significantly (P < 0.05) inhibited in water-glazed and rosemary-glazed shrimp compare with unglazed shrimp. In addition, the rosemary-glazed shrimp was observed to maintain the lowest TVB-N value during the whole frozen storage. The results suggested that glazing with water and rosemary extract could effectively control the increase in TVB-N of mud shrimp during frozen storage. He and Xiao (2016) also reported that using tangerine peel essential oils as glazing layer on fish preservation could lower the increase of TVB-N. It could be attribute to the treatment of natural extract that can effectively inhibited the degradation of macromolecular component containing nitrogen. 3.2 Changes in drip loss Drip loss has been reported to be a good indicator for frozen shrimp quality evaluation because an increment in drip loss has been shown to result in texture loss in thawing frozen tissue (Sundararajan, Prudente, Bankston, King, Wilson, & Sathivel, 2011). Fig. 1b shows the changes of drip loss of mud shrimp with different treatments during frozen storage. The drip loss for all of the studied shrimp samples was increased with the storage time, and unglazed shrimp showed the highest (P < 0.05) 12
drip loss during the whole storage, followed by the water-glazed and rosemary-glazed shrimp. After 24 weeks of storage, the drip loss of unglazed, water-glazed, and rosemary-glazed shrimp increased to 17.61%, 12.72%, and 11.27%, respectively. The results revealed that glazing and rosemary extract treatments significantly decreased drip loss of mud shrimp during frozen storage, which may be due to their protective effects on the protein and thus improving the water holding capacity (WHC). This agreed with the study from Sundararajan et al. (2011), who reported that glazing treatment with either water or green tea extract could significantly improve thaw yield and lower the drip loss in shrimp during frozen storage. 3.3 LF-NMR relaxation time (T2) and moisture distribution The continuous distribution analysis of T 2 showed three peaks represented three water components, that are as follows: T2b (<10 ms) represents bound water that tightly associated with macromolecules; T 21 (30-100 ms) refers to immobilized water, which is located in the myofibrillar network; T 22 (> 100 ms) is attributed to free water. The transverse T2 reflect the bonding force between water and muscle tissue and area of the peak represent the content of each water component (Li, Jia, Zhang, Li, et al., 2017). Changes of three relaxation times (T2b, T21, and T22) and percentage of each water component (P2b, P21, and P22) in mud shrimp cubes with different treatments during frozen storage are show in Table 1. The T21 was a major component (94.3-96.1% of total water) in shrimp samples with a relaxation time of 40.9-44.9 ms. T2b and T22 were minor water components (2.4-3.4% and 1.3-3.0% of total water, respectively) 13
with a relaxation time of 2.0-4.7 ms and 318.3-823.8 ms, respectively. It was noticed that the T2b and T22 of all shrimp samples increased significantly (P < 0.05) at the 24th week compared to the initial values, indicating the decreased bonding force of water in tissue. The proportion of free water (P22) of all shrimp samples decreased quickly (P < 0.05) during frozen storage because of the water loss. The immobilized water percentage (P21) increased during the first 8 weeks of storage and then decreased slightly. The initial increase in P21 might be caused by the free water loss, and the subsequent decrease in P21 indicated the reduced water holding capacity and drip loss of myofibrillar network during frozen storage. There were no significant differences in changes of relaxation times and water percentage among different treatments. 3.4 Protein degradation and oxidation 3.4.1 Changes in SH content Changes in the total sulfhydryl (SH) content of myofibrillar protein from mud shrimp are shown in Fig. 1c. The total SH of all shrimp samples decreased gradually with the prolonged frozen storage time. After 24 weeks of storage, the SH content in unglazed, water-glazed, and rosemary-glazed shrimp decreased by 44.91%, 31.95%, and 17.17%, respectively, compared to the initial value. The decrease in SH content is generally associated with protein oxidation caused by the formation of disulfide bond or disulfide interchanges (Benjakul, Visessanguan, Thongkaew, & Tanaka, 2003). There was no significant difference in SH content of three groups of shrimp samples during first 16 weeks of storage, and then the SH content of unglazed shrimp was significantly (P < 0.05) lower than that of glazed shrimp samples. These results 14
suggest that glazing of shrimp can slow SH content changes and protect the protein from oxidation as compared to the unglazed shrimp. Wu et al. (2014) and Xiong et al. (2009) reported that lowering frozen temperature to -30°C and -40°C and mixing with konjac glucomannan could significantly mitigate the decrease in the total SH content of myofibrillar protein from fishes during frozen storage. The current study results showed that glazing with whether water or rosemary extract had a significant cryoprotective effect on myofibrillar protein of mud shrimp during frozen storage at -20°C. 3.4.2 Changes in disulfide bond content The disulfide bond content of myofibrillar protein in all mud shrimp samples increased gradually during the first 16 weeks of frozen storage, and then decreased for up to 24th week (Fig. 1d). The formation of disulfide bond is generally due to the oxidation of sulfhydryl groups and conformational changes of myofibrillar protein (Benjakul et al., 2003). The decrease of disulfide bonds during the late stage of frozen storage was probably attributed to the degradation and fragmentation of cross-linked myosin heavy chain (MHC). Lu, Zhang, Li, and Luo (2017) reported the same changing trends of disulfide bond of myofibrillar protein in bighead carp (Aristichthys Nobilis) during frozen storage at -20°C. There was no significant difference in disulfide bond content of shrimp samples among three groups, indicating that the formation of disulfide bond might be less susceptible to the influence of different glazing treatments. 3.4.3 Intrinsic fluorescence intensity (IFI) 15
Tryptophan (Trp) is a kind of Aromatic amino acids which are present in the inner core of the native proteins, and their emergence indicates the extent of protein unfolding. Since myosin has Trp residues both in its rod and head regions, intrinsic fluorescence measurements are widely used as an exposure magnitude index of Trp and monitor the conformational changes of myofibrillar proteins (Qiu, Xia, & Jiang, 2014). Moreover, the intrinsic fluorescence is sensitive to the polarity of microenvironment and the transition of tertiary structures of protein (Lina et al., 2013). The fluorescence spectra of myofibrillar protein in mud shrimp from three treatments during frozen storage are shown in Fig. 2. The data demonstrated that fresh myofibrils excited at 295 nm had a broad band with a maximum at 335 nm and exhibited high fluorescence intensity. The IFI of myofibrillar protein in unglazed shrimp decreased sharply during the whole storage, while in glazed shrimp the IFI decreased mainly during the first 8 weeks. After 24 weeks of storage, the IFI in unglazed, water-glazed, and rosemary-glazed shrimp decreased by 32.60%, 11.81%, and 16.28%, respectively, compared to the initial value. The decrease in IFI is associated with the denaturation and exposure of indole side chain of Trp (Lefevre, Fauconneau, Thompson, & Gill, 2007). This indicated that prolonged frozen storage resulted in the exposure of buried Trp residues and tertiary structures changes of myofibrillar protein. A larger decrease in IFI was observed in unglazed shrimp compared with glazed samples, demonstrating that glazing treatment could protect the protein from denaturation and structural changes during frozen storage. 16
3.5 Lipid oxidation 3.5.1 Changes in lipid content Variations in the total lipid content of mud shrimp during frozen storage are presented in Fig. 3a. The initial lipid content of shrimp samples was 0.699 g/100 g. The lipid content of rosemary-glazed shrimp decreased slower than other shrimp samples and showed a higher level during most of the frozen storage. While in unglazed and water-glazed shrimp, the lipid content decreased rapidly during 16 weeks of storage and then increased. After 16 weeks of frozen storage, the lipid content of unglazed, water-glazed, and rosemary-glazed shrimps decreased to 0.337, 0.365, and 0.470 g/100 g, respectively. In general, there was no significant difference in lipid content of shrimp among the three treatments. The decrease in total lipid content may be due to lipid oxidation and selective lipolysis of triglyceride and phospholipids, which altered the chemical composition of shrimp muscle (Romotowska, Karlsdóttir, Gudjónsdóttir, Kristinsson, & Arason, 2016). Soyer et al. (2010) reported that phospholipid content in chicken meat were affected by prolonged frozen storage. 3.5.2 Changes in FFA The formation of free fatty acid (FFA) is measured to evaluate the degree of lipid hydrolysis. Since FFA is more prone to oxidation than esterified fatty acids, lipid hydrolysis is a major factor that affects lipid oxidation (de Abreu, Losada, Maroto, & Cruz, 2011). Changes in FAA of unglazed, water-glazed, and rosemary-glazed mud shrimp during frozen storage are shown in Fig. 3b. The FFA content in unglazed 17
shrimp was significantly (P < 0.05) higher than FFA content in glazed shrimps after 4 weeks of frozen storage. During the whole frozen storage, the FFA content of unglazed shrimp increased rapidly (P < 0.05) from an initial value of 3.67 to a high value of 7.37 g/100 g lipids, indicating the extensive hydrolysis of lipids. While for water-glazed and rosemary-glazed shrimp, the FFA content increased to 6.49 and 5.88 g/100 g lipids, respectively, after 24 weeks of storage. The data revealed that glazing treatment could be able to control the lipid hydrolysis development in shrimp during frozen storage. EmİR ÇOban (2013) also reported that glazing with essential oil could lower the FFA in rainbow trout (Oncorhynchus mykiss) fillet compared with the control during frozen storage. There was no significant difference in FFA content between water-glazed and rosemary-glazed shrimp except at the 24th week. 3.5.3 Changes in PV The peroxide value (PV) was employed to measure the formation of primary lipid oxidation products that determine the extent of lipid oxidation at the initial stages of oxidation. Changes in PV of all mud shrimp samples during frozen storage are shown in Fig. 3d. The PV in unglazed shrimp showed a marked increase (P < 0.05) from the initial value of 2.19 to 4.06 meq/kg after 16 weeks of storage and decreased thereafter to 1.27 meq/kg after 24 weeks of storage. In water-glazed and rosemary-glazed shrimp, PV value increased slowly during 20 weeks of storage, and then increased to 3.44 and 4.41 meq/kg at the end of storage. The increase in PV was probably due to the faster rate of peroxides formation than degradation of peroxides into secondary oxidation products. The degradation of peroxides and formation of secondary 18
oxidation products resulted in the subsequent decrease in PV (Soyer et al., 2010). The unglazed shrimp reached the highest formation rate of PV at the 16 th week, much earlier than glazed shrimp samples, indicating that glazing treatment could effectively slow down the primary oxidation process in mud shrimp during frozen storage. During the frozen storage, a slower formation of PV was observed in rosemary-glazed shrimp, which may be attributed to the antioxidant properties of rosemary extract. According to the results, it is concluded that glazing and rosemary extract treatments had significant effect on delaying lipid oxidation in frozen mud shrimp. Sarabi et al. (2017) and Özyurt et al. (2011) also reported the anti-oxidative effect of rosemary extract on coated fried Escolar fish fillets and sea bream (Sparus aurata) during frozen storage. 3.5.4 Formation of fluorescent compounds (FC) The formation of fluorescent compounds (FC) is due to the interaction between primary and secondary lipids oxidation products and nucleophilic molecules such as proteins. The FC was measured using their fluorescence properties (FR value) in aqueous phases from the lipid extraction. The changes in FR value of unglazed, water-glazed, and rosemary-glazed shrimp during frozen storage are shown in Fig. 3d. The FR value of all shrimp samples increased gradually during frozen storage and then decreased slightly at the end of storage. The FR value of unglazed shrimp was higher than that of glazed shrimp samples during frozen storage, and significant differences (P < 0.05) were found in FR value at 8th, 12th, and 24th weeks. The initial FR value of shrimp was 1.67, after 20 weeks of storage, FR value in unglazed, 19
water-glazed, and rosemary-glazed shrimp showed the highest value of 3.18, 2.71, and 2.89, respectively. There was no significant difference in FR value between water-glazed and rosemary-glazed shrimp during the frozen storage. It is reported that the increase in FC formation is in agreement with the primary and secondary lipid oxidation compounds formation (Rodríguez et al., 2012). The FR value of unglazed shrimp was significantly higher than that of glazed shrimp samples, indicating a higher fluorescent compound formation in unglazed shrimp. The results showed that glazing treatment could protect mud shrimp from lipid oxidation by controlling the formation of oxidation compounds during frozen storage. Similar trend of fluorescent compound development was reported by García-Soto, Miranda, Barros-Velázquez, and Aubourg (2015), who showed that soaking with sodium metabisulphite solutions could inhibit the increase of FR value significantly in crustacean lobster krill (Munida spp.) during frozen storage at -18°C. 3.6 Sensory analysis The sensory profiles of unglazed, water-glazed and rosemary-glazed mud shrimp after different periods of frozen storage are shown in Fig. 4. The initial sensory score of all parameters (color, odor, texture, morphology, and cooking test) in shrimp samples was close to 6 (data not shown). In the first 12 weeks of storage there were no significant differences among all shrimp samples. After 16 weeks, an obvious sensory decline in the shrimp was observed for all samples and the differences among three groups of samples were found to be statistically significant (P < 0.05). The shrimp were considered to be unacceptable for human consumption when the total 20
score of sensory evaluation less than 15. Unglazed and water-glazed shrimp samples were acceptable up to 16 and 20 weeks, and rosemary-glazed shrimp sample was acceptable during the whole 24 weeks of storage. The results indicated that rosemary-glazed sample could be retaining good quality characteristics in terms of sensory assessment during frozen storage, followed by water-glazed sample. These conclusions were also supported by the results of chemical quality analyses. Previous studies also reported that the rosemary extract-immersed shrimp and essential oils-glazed rainbow trout fillet showed slower decrease in sensory scores during storage, compared with the control sample (Cadun, Kışla, & Çaklı, 2008; EmİR ÇOban, 2013). 4. Conclusions Glazing treatment with either water or rosemary extract showed excellent performance in controlling the quality loss and protein and lipid changes of frozen mud shrimp. After 16 weeks of frozen storage, unglazed mud shrimp exhibited significant quality decline, such as sensory quality loss, protein degradation, and lipid oxidative damage. The glazed mud shrimp suffered less quality loss during the 24 weeks of frozen storage. In addition, glazing with rosemary extract appears to be more beneficial for long-term frozen storage, with lower TVB-N, drip loss, PV, FFA and higher lipid content and sensory scores. This study demonstrated the potential of rosemary extract as a natural glazing material for mud shrimp. Acknowledgments This research was funded by the Beijing Advanced Innovation Center for Food 21
Nutrition and Human Health (201502910110942) and National Science and Technology Ministry of China (2015BAD17B03). References Baron, C. P., KjÆrsgård, I. V. H., Jessen, F., & Jacobsen, C. (2007). Protein and lipid oxidation during frozen storage of rainbow trout (Oncorhynchus mykiss). Journal of Agricultural and Food Chemistry, 55(20), 8118-8125. Benjakul, S., Visessanguan, W., Thongkaew, C., & Tanaka, M. (2003). Comparative study on physicochemical changes of muscle proteins from some tropical fish during frozen storage. Food Research International, 36(8), 787-795. Cadun, A., Kışla, D., & Çaklı, Ş. (2008). Marination of deep-water pink shrimp with rosemary extract and the determination of its shelf-life. Food Chemistry, 109(1), 81-87. Cavonius, L. R., & Undeland, I. (2017). Glazing herring (Clupea harengus) fillets with herring muscle press juice: effect on lipid oxidation development during frozen storage. International Journal of Food Science & Technology, 52(5), 1229-1237. de Abreu, D. A. P., Losada, P. P., Maroto, J., & Cruz, J. M. (2011). Lipid damage during frozen storage of Atlantic halibut (Hippoglossus hippoglossus) in active packaging film containing antioxidants. Food Chemistry, 126(1), 315-320. EmİR ÇOban, Ö. (2013). Evaluation of essential oils as a glazing material for frozen rainbow trout (Oncorhynchus mykiss) fillet. Journal of Food Processing and Preservation, 37(5), 759-765. García-Soto, B., Miranda, J. M., Barros-Velázquez, J., & Aubourg, S. P. (2015). Quality changes during the frozen storage of the crustacean lobster krill (Munida spp.). European Journal 22
of Lipid Science and Technology, 117(4), 431-439. Haghshenas, M., Hosseini, H., Nayebzadeh, K., Kakesh, B. S., Mahmoudzadeh, M., & Fonood, R. K. (2015). Effect of beta glucan and carboxymethyl cellulose on lipid oxidation and fatty acid composition of pre-cooked shrimp nugget during storage. LWT - Food Science and Technology, 62(2), 1192-1197. He, Q., & Xiao, K. (2016). The effects of tangerine peel (Citri reticulatae pericarpium) essential oils as glazing layer on freshness preservation of bream (Megalobrama amblycephala) during superchilling storage. Food Control, 69(Supplement C), 339-345. Kong, C., Wang, H., Li, D., Zhang, Y., Pan, J., Zhu, B., & Luo, Y. (2016). Quality changes and predictive models of radial basis function neural networks for brined common carp (Cyprinus carpio) fillets during frozen storage. Food Chemistry, 201, 327-333. Lefevre, F., Fauconneau, B., Thompson, J. W., & Gill, T. A. (2007). Thermal denaturation and aggregation properties of atlantic salmon myofibrils and myosin from white and red muscles. Journal of Agricultural and Food Chemistry, 55(12), 4761-4770. Li, D., Jia, S., Zhang, L., Li, Q., Pan, J., Zhu, B., Prinyawiwatkul, W., & Luo, Y. (2017). Post-thawing quality changes of common carp (Cyprinus carpio) cubes treated by high voltage electrostatic field (HVEF) during chilled storage. Innovative Food Science & Emerging Technologies, 42(Supplement C), 25-32. Li, D., Jia, S., Zhang, L., Wang, Z., Pan, J., Zhu, B., & Luo, Y. (2017). Effect of using a high voltage electrostatic field on microbial communities, degradation of adenosine triphosphate, and water loss when thawing lightly-salted, frozen common carp (Cyprinus carpio). Journal of Food Engineering, 212(Supplement C), 226-233. 23
Li, T., Hu, W., Li, J., Zhang, X., Zhu, J., & Li, X. (2012). Coating effects of tea polyphenol and rosemary extract combined with chitosan on the storage quality of large yellow croaker (Pseudosciaena crocea). Food Control, 25(1), 101-106. Lina, R., Yanshun, X., Qixing, J., Wenshui, X., & Chunjiang, Q. (2013). Investigation on structural changes of myofibrillar proteins from Silver Carp (Hypophthalmichthys molitrix) during frozen storage. Food Science and Technology Research, 19(6), 1051-1059. Lu, H., Wang, H., & Luo, Y. (2017). Changes in protein oxidation, water-holding capacity, and texture of bighead carp (Aristichthys Nobilis) fillets under chilled and partial frozen storage. Journal of Aquatic Food Product Technology, 26(5), 566-577. Lu, H., Zhang, L., Li, Q., & Luo, Y. (2017). Comparison of gel properties and biochemical characteristics of myofibrillar protein from bighead carp (Aristichthys nobilis) affected by frozen storage and a hydroxyl radical-generation oxidizing system. Food Chemistry, 223(Supplement C), 96-103. Mesarčová, L., Marcinčák, S., Nagy, J., Popelka, P., Bača, M., Jevinová, P., & Marcinčáková, D. (2013). Effect of glaze and selected herbal extracts on lipid oxidation and sensory properties of frozen Atlantic herrings (Clupea harengus L.). Acta Alimentaria, 42(2), 236-244. Özyurt, G., Özkütük, A. S., & Polat, A. (2011). Capability of the rosemary (Rosmarinus officinalis) extract on the oxidative stability of cooked sea bream (Sparus aurata) during frozen storage. Journal für Verbraucherschutz und Lebensmittelsicherheit, 6(2), 167-174. Qiu, C., Xia, W., & Jiang, Q. (2014). Pressure-induced changes of silver carp 24
(Hypophthalmichthys molitrix) myofibrillar protein structure. European Food Research and Technology, 238(5), 753-761. Rocío Teruel, M., Dolores Garrido, M., Espinosa Vicente, M., & Linares, M. (2015). Effect of different format-solvent rosemary extracts (Rosmarinus officinalis) on frozen chicken nuggets quality. Food Chemistry, 172, 40-46. Rodríguez, A., Cruz, J. M., Paseiro-Losada, P., & Aubourg, S. P. (2012). Effect of a polyphenol–vacuum packaging on lipid deterioration during an 18-month frozen storage of coho salmon (Oncorhynchus kisutch). Food and Bioprocess Technology, 5(6), 2602-2611. Romotowska, P. E., Karlsdóttir, M. G., Gudjónsdóttir, M., Kristinsson, H. G., & Arason, S. (2016). Influence of feeding state and frozen storage temperature on the lipid stability of Atlantic mackerel (Scomber scombrus). International Journal of Food Science & Technology, 51(7), 1711-1720. Sánchez-Alonso, I., Carmona, P., & Careche, M. (2012). Vibrational spectroscopic analysis of hake (Merluccius merluccius L.) lipids during frozen storage. Food Chemistry, 132(1), 160-167. Sarabi, M., Keramat, J., & Kadivar, M. (2017). Antioxidant effect of rosemary extract and BHT on the quality of coated fried Escolar (Lipidocybium flavobrunium) fish fillets during frozen storage. International Food Research Journal, 24(2), 525-533. Seabra, L. M. J., Damasceno, K. S. F. S. C., Andrade, S. A. C., Dantas, M. M. G., Soares, N. K. M., & Pedrosa, L. F. C. (2011). Effect of rosemary on the quality characteristics of white shrimp (Litopenaeus vannamei). Journal of Food Quality, 34(5), 363-369. 25
Soares, N. M. F., Oliveira, M. S. G., & Vicente, A. A. (2015). Effects of glazing and chitosan-based coating application on frozen salmon preservation during six-month storage in industrial freezing chambers. LWT - Food Science and Technology, 61(2), 524-531. Solval, K. M., Espinoza Rodezno, L. A., Moncada, M., Bankston, J. D., & Sathivel, S. (2014). Evaluation of chitosan nanoparticles as a glazing material for cryogenically frozen shrimp. LWT - Food Science and Technology, 57(1), 172-180. Soyer, A., Özalp, B., Dalmış, Ü., & Bilgin, V. (2010). Effects of freezing temperature and duration of frozen storage on lipid and protein oxidation in chicken meat. Food Chemistry, 120(4), 1025-1030. Sundararajan, S., Prudente, A., Bankston, J. D., King, J. M., Wilson, P., & Sathivel, S. (2011). Evaluation of green tea extract as a glazing material for shrimp frozen by cryogenic freezing. Journal of Food Science, 76(7), E511-E518. Taheri, A. (2015). Antioxidative effect of rainbow sardine (Dussumieria acuta) protein hydrolysate on lipid and protein oxidation in Black Pomfret (Parastromateus niger) fillet by glazing. Journal of Aquatic Food Product Technology, 24(3), 241-258. Tironi, V. A., Tomás, M. C., & Añón, M. C. (2010). Quality loss during the frozen storage of sea salmon (Pseudopercis semifasciata). Effect of rosemary (Rosmarinus officinalis L.) extract. LWT - Food Science and Technology, 43(2), 263-272. Wu, H., Wang, Z., Luo, Y., Hong, H., & Shen, H. (2014). Quality changes and establishment of predictive models for Bighead Carp (Aristichthys nobilis) fillets during frozen storage. Food and Bioprocess Technology, 7(12), 3381-3389. 26
Xiong, G., Cheng, W., Ye, L., Du, X., Zhou, M., Lin, R., Geng, S., Chen, M., Corke, H., & Cai, Y.-Z. (2009). Effects of konjac glucomannan on physicochemical properties of myofibrillar protein and surimi gels from grass carp (Ctenopharyngodon idella). Food Chemistry, 116(2), 413-418. Xu, Z., Liu, X., Wang, H., Hong, H., & Luo, Y. (2017). Comparison between the Arrhenius model and the radial basis function neural network (RBFNN) model for predicting quality changes of frozen shrimp (Solenocera melantho). International Journal of Food Properties, 20(11), 2711-2723. Xu, Z., Liu, X., Wang, H., Hong, H., Yu, X., & Luo, Y. (2016). Establishment of the Arrhenius Model and the Radial Basis Function Neural Network (RBFNN) Model to predict quality of thawed shrimp (Solenocera melantho) stored at different temperatures. Journal of Food Processing and Preservation, 40(5), 882-892. Yerlikaya, P., Gokoglu, N., & Topuz, O. K. (2010). Use of natural plant extracts in batter coating of shrimp and their effects on the quality of shrimp during frozen storage. Journal of Food Processing and Preservation, 34(1), 127-138. Yuan, G., Lv, H., Tang, W., Zhang, X., & Sun, H. (2016). Effect of chitosan coating combined with pomegranate peel extract on the quality of Pacific white shrimp during iced storage. Food Control, 59(Supplement C), 818-823.
Figure captions Fig. 1. Changes in (a) TVB-N, (b) drip loss, (c) SH, and (d) disulfide bond of 27
unglazed, water-glazed, and rosemary-glazed mud shrimp during frozen storage at -20 °C. Fig. 2. Changes in the intrinsic fluorescence intensity (IFI) of myofibrillar proteins from (a) unglazed, (b) water-glazed, and (c) rosemary-glazed mud shrimp during frozen storage at -20 °C. Fig. 3. Changes in (a) lipid content, (b) FFA, (c) PV, and (d) fluorescent compound of unglazed, water-glazed, and rosemary-glazed mud shrimp during frozen storage at -20 °C. Fig. 4. Profiles of sensory analysis of unglazed, water-glazed, and rosemary-glazed mud shrimp after 4 weeks, 8 weeks, 12 weeks, 16 weeks, 20weeks, and 24 weeks of frozen storage at -20 °C.
28
TVB-N (mg/100 g)
30 25 20
b
Unglazed Water-glazed Rosemary-glazed
Drip loss (%)
a
15 10 5 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26
20 Unglazed 18 Water-glazed 16 Rosemary-glazed 14 12 10 8 6 4 2 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26
5
8
d
Unglazed Water-glazed Rosemary-glazed
disulfide bond content (mol/10 g protein)
9
Storage time (week)
7
5
c
SH content (mol/10 g protein)
Storage time (week)
6 5 4 3 2 0 2 4 6 8 10 12 14 16 18 20 22 24 26
5.0 4.5 4.0 3.5 3.0 2.5
Unglazed Water-glazed Rosemary-glazed
2.0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Storage time (week)
Storage time (week)
Fig. 1. Changes in (a) TVB-N, (b) drip loss, (c) SH, and (d) disulfide bonds of unglazed, water-glazed, and rosemary-glazed mud shrimp during frozen storage at -20 °C.
29
3500 fresh 8w 16w 24w
3000 2500 2000 1500 1000 500 0
320
340
360
380
b fluorescence intensity (FI)
fluorescence intensity (FI)
a
fluorescence intensity (FI)
fresh 8w 16w 24w
3000 2500 2000 1500 1000 500 0
400
Wavelength (nm)
c
3500
320
340
360
380
400
Wavelength (nm)
3500 fresh 8w 16w 24w
3000 2500 2000 1500 1000 500 0
320
340
360
380
400
Wavelength (nm)
Fig. 2. Changes in the intrinsic fluorescence intensity (IFI) of myofibrillar proteins from (a) unglazed, (b) water-glazed, and (c) rosemary-glazed mud shrimp during frozen storage at -20 °C.
30
Lipid content (g/100g)
0.8 0.7
Unglazed Water-glazed Rosemary-glazed
b
0.6 0.5 0.4 0.3 0.2 0.1 0 2 4 6 8 10 12 14 16 18 20 22 24 26
Free fatty acid (g/100 g lipids)
a
8 7 6 5 4 3 2 1
0 0 2 4 6 8 10 12 14 16 18 20 22 24 26
Storage time (week)
Unglazed 5.0 Water-glazed 4.5 Rosemary-glazed 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 2 4 6 8 10 12 14 16 18 20 22 24 26
Storage time (week)
d
4.0 3.5 3.0
FR value
PV (meq/kg)
c
Unglazed Water-glazed Rosemary-glazed
2.5 2.0 1.5 1.0 0.5
Unglazed Water-glazed Rosemary-glazed
0.0 0 2 4 6 8 10 12 14 16 18 20 22 24 26
Storage time (week)
Storage time (week)
Fig. 3. Changes in (a) lipid content, (b) FFA, (c) PV, and (d) fluorescent compounds of unglazed, water-glazed, and rosemary-glazed mud shrimp during frozen storage at -20 °C.
31
Fig. 4. Profiles of sensory analysis of unglazed, water-glazed, and rosemary-glazed mud shrimp after 4 weeks, 8 weeks, 12 weeks, 16 weeks, 20weeks, and 24 weeks of frozen storage at -20 °C.
32
Table 1. Changes of LF-NMR relaxation time (T2) and percentage of each relaxation component in mud shrimp during frozen storage (UG: Unglazed; WG: Water-glazed; RG: Rosemary-glazed).
Storage time (week) Parameters
T2b (ms)
T21 (ms)
T22 (ms)
P2b (%)
P21 (%)
P22 (%)
Treatment 0
8
16
24
UG
2.4±0.4Aa
2.5±0.4Aab
3.0±0.3Aa
4.7±0.8Ba
WG
2.4±0.4Aa
2.7±0.1ABa
2.2±0.7Aa
3.5±1.1Ba
RG
2.4±0.4Aa
2.2±0.3Ab
2.0±1.0Aa
3.7±1.3Ba
UG
44.9±3.0Aa
43.9±2.3ABa
42.2±2.7ABa
40.9±2.2Ba
WG
44.9±3.0Aa
42.8±1.2ABa
41.6±1.6Ba
41.4±2.3Bab
RG
44.9±3.0Aa
43.4±3.2Aa
42.8±2.5Aa
44.1±1.6Ab
UG
318.3±41.2Aa
674.9±120.0Ba
693.2±111.8Ba
648.6±203.9Ba
WG
318.3±41.2Aa
623.3±187.2Ba
484.2±92.0ABb
589.1±153.6Ba
RG
318.3±41.2Aa
823.8±182.8Ca
711.9±99.6BCa
589.8±167.6Ba
UG
2.7±0.3ABa
2.5±0.3Aa
3.0±0.4BCa
3.4±0.4Ca
WG
2.7±0.3ABa
2.4±0.1Ba
2.7±0.4ABa
3.1±0.6Ba
RG
2.7±0.3ABa
2.4±0.1Aa
3.2±0.4BCa
3.4±0.5Ca
UG
94.3±0.9Aa
96.0±0.3Ca
95.7±0.4BCa
95.1±0.5Ba
WG
94.3±0.9Aa
96.1±0.4Ba
95.8±0.7Ba
95.3±0.4Ba
RG
94.3±0.9Aa
96.0±0.2Ca
95.3±0.4Ba
95.3±0.1Ba
UG
3.0±0.8Aa
1.6±0.2Ba
1.3±0.1Ba
1.5±0.4Ba
WG
3.0±0.8Aa
1.5±0.3Ba
1.5±0.4Ba
1.7±0.3Ba
RG
3.0±0.8Aa
1.6±0.2Ba
1.6±0.4Ba
1.4±0.5Ba
The same capital letters on the same row represented that there was no significant difference between the values at different storage time (P > 0.05); The same lowercase letter on the same column represented that there was no significant difference between the values under different treatment (P > 0.05).
33
Highlights 1. First study to apply rosemary extract in glazing treatment on frozen mud shrimp. 2. Unglazed shrimp showed a significant decline in quality after 16 weeks of storage. 3. Glazing reduced loss of quality, and protein and lipid changes effectively in shrimp. 4. Rosemary extract can be used as a glazing material for preservation of mud shrimp.
34
S0308-8146(18)31458-4 https://doi.org/10.1016/j.foodchem.2018.08.056 FOCH 23397
To appear in:
Food Chemistry
Received Date: Revised Date: Accepted Date:
25 February 2018 10 August 2018 13 August 2018
Please cite this article as: Shi, J., Lei, Y., Shen, H., Hong, H., Yu, X., Zhu, B., Luo, Y., Effect of glazing and rosemary (Rosmarinus officinalis) extract on preservation of mud shrimp (Solenocera melantho) during frozen storage, Food Chemistry (2018), doi: https://doi.org/10.1016/j.foodchem.2018.08.056
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Effect of glazing and rosemary (Rosmarinus officinalis) extract on preservation of mud shrimp (Solenocera melantho) during frozen storage
Jing Shia, Yutian Leib, Huixing Shenc, Hui Hongb, Xunpei Yud, Beiwei Zhua,e, Yongkang Luoa,b,*
a
Beijing Advanced Innovation Center for Food Nutrition and Human Health, China
Agricultural University, Yuanmingyuan West Road 2, Beijing 100193, China b
Beijing Laboratory for Food Quality and Safety, College of Food Science and
Nutritional Engineering, China Agricultural University, Beijing 100083, China c
College of Science, China Agricultural University, Beijing, 100083, China
d
Zhejiang Tianhe Aquatic Products Co., Ltd, Taizhou, 318000, China
e
School of Food Science and Technology, Dalian Polytechnic University, National
Engineering Research Center of Seafood, Dalian, 116034, China
*Corresponding Author. Tel./Fax: +86-10-62737385 E-mail: [email protected]; [email protected]
1
Abstract In this study, glazing with water and rosemary (Rosmarinus officinalis) extract were applied on frozen mud shrimp (Solenocera melantho) and stored at -20 °C for 24 weeks. Quality loss and protein and lipid changes of shrimp were evaluated by total volatile basis nitrogen (TVB-N), drip loss, moisture distribution, sulfhydryl content (SH), disulfide bond, intrinsic fluorescence intensity, lipid content, free fatty acids (FFA), peroxide value (PV), fluorescent compounds and sensory characteristics. Results showed that unglazed mud shrimp exhibited significant quality decline after 16 weeks of frozen storage. Glazing treatment significantly reduced quality loss, protein degradation, and lipid oxidative damage of shrimp during the 24 weeks of frozen storage, compared to the unglazed control sample. Glazing with rosemary extract was more effective in controlling quality changes in frozen mud shrimp with lower TVB-N, drip loss, PV, FFA and higher lipid content and sensory scores.
Key words: Mud shrimp; Rosemary extract; Glazing; Frozen storage; Protein changes; Lipid oxidation
1. Introduction Shrimp is one of the most popular seafood consumed in China and around the world. Normally, harvested sea shrimp is stored by freezing to minimize bacterial growth and loss of nutrition, because of its highly perishable properties (Yerlikaya, Gokoglu, & Topuz, 2010). However, protein denaturation, lipid oxidation, and 2
sublimation and recrystallization of ice crystals still occur during prolonged frozen storage, which results in deterioration of quality in shrimp, such as discoloration, off-flavors, rancidity, dehydration, and drip loss (Baron, KjÆrsgård, Jessen, & Jacobsen, 2007; Haghshenas, Hosseini, Nayebzadeh, Kakesh, Mahmoudzadeh, & Fonood, 2015). Previous study has reported that lipid hydrolysis and oxidation and protein denaturation occurred in seafood during frozen storage had an important influence on product acceptability (Tironi, Tomás, & Añón, 2010). To protect the quality of shrimp from the effects of dehydration and oxidation during frozen storage, the application of a layer of ice on the surface of frozen shrimp by dipping has been widely used (Mesarčová et al., 2013). The ice layer can act as a barrier to control moisture transfer and oxygen uptake in the surface of frozen foods (Solval, Espinoza Rodezno, Moncada, Bankston, & Sathivel, 2014). In addition, several kinds of glazing materials have been investigated to improve quality of frozen seafood products, such as protein hydrolysate (Taheri, 2015), muscle press juice (Cavonius & Undeland, 2017), essential oils (EmİR ÇOban, 2013), and natural compounds (Mesarčová et al., 2013). With the advantages of safety and antioxidative activity, natural compounds have attracted more attention and being extensively studied in seafood preservation (Mesarčová et al., 2013). Rosemary (Rosmarinus officinalis), a woody aromatic herb, has been recognized for both its use as food flavoring and antioxidant (Seabra, Damasceno, Andrade, Dantas, Soares, & Pedrosa, 2011). The high antioxidant activity of rosemary is primarily due to certain compounds, including phenolic diterpenes, 3
carnosic acid, carnosol, and rosmarinic acid (Rocío Teruel, Dolores Garrido, Espinosa Vicente, & Linares, 2015). Several studies have investigated the application of rosemary extract on quality control of aquatic products during storage. Sarabi, Keramat, and Kadivar (2017) reported that rosemary extract is more effective in controlling lipid oxidation in fried escolar (Lipidocybium flavobrunium) fish fillets compared with Butyrate hydroxyl toluene (BHT). Li, Hu, Li, Zhang, Zhu, and Li (2012) evaluated the coating effects of rosemary extract combined with chitosan on the storage quality of large yellow croaker (Pseudosciaena crocea). In shrimp, Seabra et al. (2011) reported that dehydrate rosemary could improve the quality of frozen peeled white shrimp (Litopenaeus vannamei). Cadun, Kışla, and Çaklı (2008) assessed the antioxidant activity of rosemary extract on marinated deep-water pink shrimp (Parapenaeus longirostris) and the results showed that rosemary extract helped to prolong the shelf-life of marinated shrimp. However, there are only few reports about the effect of rosemary on shrimp quality improving. The application of rosemary extract combined with glazing technique to control quality changes in shrimp during frozen storage have not been reported. The objective of this study was to evaluate rosemary (Rosmarinus officinalis) extract as a glazing material for mud shrimp (Solenocera melantho) preservation, especially its effects on quality changes, protein denaturation, and lipid oxidation during frozen storage. 2. Materials and methods 2.1 Preparation of glazing solution containing rosemary extract 4
Rosemary (Rosmarinus officinalis) extract was purchased as dry powders from Zhengzhou Wanbo chemical products Co., Ltd (Purity≥95%, Zhengzhou, Henan province, China). The glazing solution was prepared by dissolving rosemary extract (0.2%, w/w) in potable water, mixed thoroughly by a magnetic stirrer at room temperature. The water solution of rosemary extract was kept at 0 °C before used for glazing for shrimp. 2.2 Materials and samples Mud shrimp (Solenocera melantho) (11.555.11 g) were captured in the East China Sea, mixed with ice and transported to the laboratory immediately. Upon arrival, several shrimp samples were separated and analyzed as initial fresh shrimp (week 0). The remaining shrimp were washed, drained for 3 min, and put on stainless steel plates. The placed shrimp was frozen in a refrigerator at -40 °C for 24 h, to make the center of shrimp reached -20 °C rapidly. Then samples of frozen mud shrimp were removed from the refrigerator and divided randomly into three groups: the unglazed group (UG) was set as control, water-glazed (WG) group was glazed with potable water, and rosemary-glazed (RG) group was glazed with solution of rosemary. 2.3 Glazing of mud shrimp and frozen storage The frozen mud shrimp (approximately 150 g per batch) in the WG group and RG group were weighed (W1) and dipped into prepared water and 0.2% of rosemary solution (0 °C, 10~15 s), respectively. After dipping, the shrimp were drained for 1 min and weighed again (W2). The dipping times were adjusted to achieve a similar glazing percentage (15% ± 2%) in all batches of shrimp samples. The percentage of 5
glazing was calculated following Equation (1), where W1 and W2 indicate the weight of shrimp samples before and after glazing application. (1) Each batch of glazed (WG and RG groups) and unglazed (UG group) samples was packed in a polyvinyl chloride bags and stored at -20 °C for 24 weeks. Three bags of shrimp sample in each group were taken randomly for analysis at each sampling time. Before analysis, shrimp samples in bags were thawed in running water for 1~2 hours. The ice-glaze of glazed shrimp samples was removed gently during thawing process, in order to prevent shrimp samples from being immersed in melted water or solution of rosemary extract for so long time as to cause further quality changes. All determination was performed in triplicate. 2.4 Determination of total volatile basis nitrogen (TVB-N) and drip loss The TVB-N was determined using the method of semi-micro steam distillation according to the method of Xu, Liu, Wang, Hong, Yu, and Luo (2016). The drip loss was estimated using the method of Soares, Oliveira, and Vicente (2015) with some modifications. Each bags of thawed shrimp samples were taken out, blotted with filter paper and weighed the present weight. The drip loss of shrimp samples was calculated by the following equation (2), where W3 indicates the initial weight of shrimp samples without glazing and W4 indicates the weight of thawed shrimp samples. (2) 2.5 Low field nuclear magnetic resonance (LF-NMR) analysis LF-NMR measurements were performed using a Niumag Benchtop Pulsed NMR 6
Analyser PQ001 (Niumag Electric Corporation, Shanghai, China) with a resonance frequency of 23.0 Hz, according to the methods of Li, Jia, Zhang, Wang, et al. (2017) with some modifications. Briefly, shrimp samples were cut into cubes (1×1×1 cm) and placed in cylindrical glass tubes, and then inserted into the LF-NMR probe one by one.
The
transverse
relaxation
time,
T2,
was
measured
using
the
Carr-Purcell-Meiboom-Gill (CPMG) sequence with a τ-value of 120 μs. Data were acquired from 5000 echoes of 8 scan repetitions and analyzed by MultiExp Inv Analysis software from Niumag Electric Corporation. Three relaxation times (T 2b, T21, and T22) and the percentage of each corresponding relaxation component (P2b, P21, and P22) were obtained as outputs. 2.6 Determination of protein degradation and oxidation 2.6.1 Preparation of the myofibrillar protein Myofibrillar protein (MFP) was prepared according to the method of Kong et al. (2016) with some modifications. Two grams of minced shrimp was mixed with 15 ml of cold distilled water and homogenized for 1 min. The homogenate was extracted at 4 °C for 30 min and then centrifuged at 14000 g for 10 min. The washing step was repeated using the 15 ml of cold 0.3% NaCl (instead of water) to extract more water-soluble substances. Then, the precipitate was mixed with 30 ml of Tris-maleate buffer (0.6 M NaCl-20 mM Tris-maleate, pH 7.0) and homogenized for 10 s. The homogenate was skept at 4°C for 1 h to extract myofibrillar protein and then centrifuged at 14000 g and 4°C for 10 min. The supernatant was collected and washed with four volumes of cold distilled water. After centrifugation at 14000 g and 4°C for 7
5 min, the precipitate of MFP was obtained and dissolved in chilled 0.6 M NaCl. The protein concentration of the MFP solution was determined by Biuret assay (Wu, Wang, Luo, Hong, & Shen, 2014) and adjusted to 4 mg /ml. 2.6.2 Total sulfhydryl (SH) content Total sulfhydryl (SH) content was determined using 5, 5’-dithio-bis (2-nitrobenzoic acid) (DTNB) and following the method of Kong et al. (2016). Briefly, 0.5 ml of the MFP solution (4 mg/ml) was mixed with 4.5 ml 0.2 M of Tris-HCl buffer (8 M urea, 2% SDS, 10 mM EDTA, pH 8.0). Then, 4 ml of the mixture was added to 0.5 ml of 0.1% DTNB in 0.2 M of Tris-HCl buffer (pH 8.0) and incubated at 40 °C for 25 min. The absorbance was measured at 412 nm using a UV-2600 spectrophotometer (Unico Instrument Co., Ltd, Shanghai, China). The SH content was calculated from the absorbance using the molar extinction of 13600 M -1 · cm-1 and expressed as mol/105 g protein. 2.6.3 Disulfide bond content The disulfide bond content was determined using 2-nitro-5-thiosulfobenzoate (NTSB) and according to the method of Lu, Wang, and Luo (2017). A 0.5 mL of MFP solution (4 mg/ml) was mixed with 4.5 ml of 0.2 M Tris-HCl buffer (8 M urea, 1% SDS, 3 mM EDTA, pH 8.0). Then, 4 ml of the mixture was added to 0.5 ml of 10 mM NTSB in 0.2 M Tris-HCl buffer (8M urea, 3mM EDTA, 1% SDS, 0.1 M Na2SO3, pH 9.5) and incubated at 40 °C for 25 min. The absorbance was measured at 412 nm using a UV-2600 spectrophotometer. Disulfide bond content was calculated using the molar extinction of 13600 M-1 · cm-1 and expressed as mol/105 g protein. 8
2.6.4 Intrinsic fluorescence intensity (IFI) Intrinsic fluorescence was measured as described by Lina, Yanshun, Qixing, Wenshui, and Chunjiang (2013) with minor modification. Diluted MFP (0.05 mg/ml) in 0.6 M NaCl solution was scanned using a F97 fluorescence spectrophotometer. Intrinsic fluorescence spectroscopy was obtained between 300 and 400 nm at an excitation wavelength of 295 nm with a scanning speed of 1000 nm/min. The excitation and emission slit widths were 10 nm. 2.7 Determination of lipid oxidation 2.7.1 Lipid extraction The lipids were extracted according to the method described by Kong et al. (2016) with some modification. Briefly, 35 g minced shrimp meat was homogenized with 35 ml of chloroform and 70 ml of methanol for 2 min. After that, an additional 35 ml of chloroform and 35 ml of distilled water were added and the mixture was homogenized again for 30 s. Then, the homogenate was vacuum filtered and the residue was washed with 35 ml of chloroform. The filtrate was then transferred to a separating funnel and allowed to stand for several hours until divided completely. The organic phase was collected from the bottom of the funnel and dried under nitrogen. The obtained lipids were kept in a desiccator until (~ 12 h) further experiments. The total lipid content was expressed as g/100g sample. 2.7.2 Free fatty acid (FFA) Free fatty acid (FFA) content of lipid extract was determined according to the method of Sánchez-Alonso, Carmona, and Careche (2012). Lipid sample (0.05~0.1 g) 9
was dissolved in 5 ml of toluene and then treated with 1 ml of 5% (w/v) cupric acetate-pyridine reagent (pH 6.0). The mixture was vortex for 2 min and then centrifuged at 3000 rpm for 5 min at room temperature. The absorbance of the upper layer was measured at 715 nm, and the FFA content was expressed as g FFA/100 g lipid. 2.7.3 Peroxide value (PV) Peroxide value (PV) was measured according to the method of Soyer, Özalp, Dalmış, and Bilgin (2010) with some modification. The lipid sample (0.01-0.3g) was dissolved in 9.8 ml of chloroform-methanol (7:3, v/v) and mixed for 4 seconds. The mixture was added with 0.05 ml of 30% ammonium thiocyanate and mixed for 4 s. Then 0.05 ml of 3.5 g/l ferrous chloride in 10 M HCl was added and mixed again for 4 s. After 5 min standing at room temperature, the absorbance was measured at 500 nm using a UV-2600 spectrophotometer. The PV was expressed as milliequivalents (meq) of peroxide/kg lipid, and a reference curve was plotted using ferric chloride standard. 2.7.4 Fluorescent compounds (FC) Formation of fluorescent compounds (FC) was determined in the aqueous phase obtained during the lipid extraction and following the method described by Rodríguez, Cruz, Paseiro-Losada, and Aubourg (2012). Fluorescence formation was studied at an excitation/emission wavelength of 393/463 nm and 327/415 nm. The relative fluorescence (RF) was calculated as RF=F/Fst, where F is the fluorescence of sample measured at each excitation/emission maximum, and Fst is the fluorescence intensity 10
of quinine in sulphate solution (1 μg/ml, 0.05 M H2SO4) at the corresponding wavelength. The FC was expressed as the fluorescence ratio (FR) and the FR was calculated as the ratio between the two RF values: FR=RF393/463nm/RF327/415nm. 2.8 Sensory analysis Sensory analysis of shrimp samples was performed as described by Xu, Liu, Wang, Hong, and Luo (2017) with some modifications. An assessment sheet was previously developed by a six-member laboratory trained panel based on a six-point scale ranging from the best to the worst characteristics. After thawing, shrimp samples were evaluated with five parameters (color, odor, texture, morphology, and cooking test). For the cooking test, sensory assessment was based on the flavor, taste, and broth turbidity. Radar maps were made to visually represent the sensory analysis results of mud shrimp samples. 2.9 Statistical analysis Experimental data was analyzed by using Microsoft Office Excel 2010 software. The SPSS 18.0 for Windows was used to perform analysis of variance (ANOVA). Statistical significance was reported as a level of P < 0.05. 3. Results and discussion 3.1 Changes in TVB-N TVB-N has been used as a common and important parameter of the seafood quality because its increase is related to spoilage by bacteria and activity of endogenous enzymes (Yuan, Lv, Tang, Zhang, & Sun, 2016). The limit of TVB-N content in sea shrimp as acceptable for human consumption is usually 30 mg/100 g. Changes in 11
TVB-N values of shrimp samples during frozen storage are presented in Fig. 1a. The initial TVB-N value of fresh shrimp was 7.84 mg/100 g averagely. TVB-N of all shrimp samples increased slowly at the first 16 weeks of storage and then increased sharply. After 24 weeks of frozen storage, unglazed sample present a value of 28.48 mg/100 g, almost reaching the acceptable limit level of 30 mg/100 g, while water-glazed and rosemary-glazed samples increased to 24.08 and 19.23 mg/100 g, respectively. The increase in TVB-N values was significantly (P < 0.05) inhibited in water-glazed and rosemary-glazed shrimp compare with unglazed shrimp. In addition, the rosemary-glazed shrimp was observed to maintain the lowest TVB-N value during the whole frozen storage. The results suggested that glazing with water and rosemary extract could effectively control the increase in TVB-N of mud shrimp during frozen storage. He and Xiao (2016) also reported that using tangerine peel essential oils as glazing layer on fish preservation could lower the increase of TVB-N. It could be attribute to the treatment of natural extract that can effectively inhibited the degradation of macromolecular component containing nitrogen. 3.2 Changes in drip loss Drip loss has been reported to be a good indicator for frozen shrimp quality evaluation because an increment in drip loss has been shown to result in texture loss in thawing frozen tissue (Sundararajan, Prudente, Bankston, King, Wilson, & Sathivel, 2011). Fig. 1b shows the changes of drip loss of mud shrimp with different treatments during frozen storage. The drip loss for all of the studied shrimp samples was increased with the storage time, and unglazed shrimp showed the highest (P < 0.05) 12
drip loss during the whole storage, followed by the water-glazed and rosemary-glazed shrimp. After 24 weeks of storage, the drip loss of unglazed, water-glazed, and rosemary-glazed shrimp increased to 17.61%, 12.72%, and 11.27%, respectively. The results revealed that glazing and rosemary extract treatments significantly decreased drip loss of mud shrimp during frozen storage, which may be due to their protective effects on the protein and thus improving the water holding capacity (WHC). This agreed with the study from Sundararajan et al. (2011), who reported that glazing treatment with either water or green tea extract could significantly improve thaw yield and lower the drip loss in shrimp during frozen storage. 3.3 LF-NMR relaxation time (T2) and moisture distribution The continuous distribution analysis of T 2 showed three peaks represented three water components, that are as follows: T2b (<10 ms) represents bound water that tightly associated with macromolecules; T 21 (30-100 ms) refers to immobilized water, which is located in the myofibrillar network; T 22 (> 100 ms) is attributed to free water. The transverse T2 reflect the bonding force between water and muscle tissue and area of the peak represent the content of each water component (Li, Jia, Zhang, Li, et al., 2017). Changes of three relaxation times (T2b, T21, and T22) and percentage of each water component (P2b, P21, and P22) in mud shrimp cubes with different treatments during frozen storage are show in Table 1. The T21 was a major component (94.3-96.1% of total water) in shrimp samples with a relaxation time of 40.9-44.9 ms. T2b and T22 were minor water components (2.4-3.4% and 1.3-3.0% of total water, respectively) 13
with a relaxation time of 2.0-4.7 ms and 318.3-823.8 ms, respectively. It was noticed that the T2b and T22 of all shrimp samples increased significantly (P < 0.05) at the 24th week compared to the initial values, indicating the decreased bonding force of water in tissue. The proportion of free water (P22) of all shrimp samples decreased quickly (P < 0.05) during frozen storage because of the water loss. The immobilized water percentage (P21) increased during the first 8 weeks of storage and then decreased slightly. The initial increase in P21 might be caused by the free water loss, and the subsequent decrease in P21 indicated the reduced water holding capacity and drip loss of myofibrillar network during frozen storage. There were no significant differences in changes of relaxation times and water percentage among different treatments. 3.4 Protein degradation and oxidation 3.4.1 Changes in SH content Changes in the total sulfhydryl (SH) content of myofibrillar protein from mud shrimp are shown in Fig. 1c. The total SH of all shrimp samples decreased gradually with the prolonged frozen storage time. After 24 weeks of storage, the SH content in unglazed, water-glazed, and rosemary-glazed shrimp decreased by 44.91%, 31.95%, and 17.17%, respectively, compared to the initial value. The decrease in SH content is generally associated with protein oxidation caused by the formation of disulfide bond or disulfide interchanges (Benjakul, Visessanguan, Thongkaew, & Tanaka, 2003). There was no significant difference in SH content of three groups of shrimp samples during first 16 weeks of storage, and then the SH content of unglazed shrimp was significantly (P < 0.05) lower than that of glazed shrimp samples. These results 14
suggest that glazing of shrimp can slow SH content changes and protect the protein from oxidation as compared to the unglazed shrimp. Wu et al. (2014) and Xiong et al. (2009) reported that lowering frozen temperature to -30°C and -40°C and mixing with konjac glucomannan could significantly mitigate the decrease in the total SH content of myofibrillar protein from fishes during frozen storage. The current study results showed that glazing with whether water or rosemary extract had a significant cryoprotective effect on myofibrillar protein of mud shrimp during frozen storage at -20°C. 3.4.2 Changes in disulfide bond content The disulfide bond content of myofibrillar protein in all mud shrimp samples increased gradually during the first 16 weeks of frozen storage, and then decreased for up to 24th week (Fig. 1d). The formation of disulfide bond is generally due to the oxidation of sulfhydryl groups and conformational changes of myofibrillar protein (Benjakul et al., 2003). The decrease of disulfide bonds during the late stage of frozen storage was probably attributed to the degradation and fragmentation of cross-linked myosin heavy chain (MHC). Lu, Zhang, Li, and Luo (2017) reported the same changing trends of disulfide bond of myofibrillar protein in bighead carp (Aristichthys Nobilis) during frozen storage at -20°C. There was no significant difference in disulfide bond content of shrimp samples among three groups, indicating that the formation of disulfide bond might be less susceptible to the influence of different glazing treatments. 3.4.3 Intrinsic fluorescence intensity (IFI) 15
Tryptophan (Trp) is a kind of Aromatic amino acids which are present in the inner core of the native proteins, and their emergence indicates the extent of protein unfolding. Since myosin has Trp residues both in its rod and head regions, intrinsic fluorescence measurements are widely used as an exposure magnitude index of Trp and monitor the conformational changes of myofibrillar proteins (Qiu, Xia, & Jiang, 2014). Moreover, the intrinsic fluorescence is sensitive to the polarity of microenvironment and the transition of tertiary structures of protein (Lina et al., 2013). The fluorescence spectra of myofibrillar protein in mud shrimp from three treatments during frozen storage are shown in Fig. 2. The data demonstrated that fresh myofibrils excited at 295 nm had a broad band with a maximum at 335 nm and exhibited high fluorescence intensity. The IFI of myofibrillar protein in unglazed shrimp decreased sharply during the whole storage, while in glazed shrimp the IFI decreased mainly during the first 8 weeks. After 24 weeks of storage, the IFI in unglazed, water-glazed, and rosemary-glazed shrimp decreased by 32.60%, 11.81%, and 16.28%, respectively, compared to the initial value. The decrease in IFI is associated with the denaturation and exposure of indole side chain of Trp (Lefevre, Fauconneau, Thompson, & Gill, 2007). This indicated that prolonged frozen storage resulted in the exposure of buried Trp residues and tertiary structures changes of myofibrillar protein. A larger decrease in IFI was observed in unglazed shrimp compared with glazed samples, demonstrating that glazing treatment could protect the protein from denaturation and structural changes during frozen storage. 16
3.5 Lipid oxidation 3.5.1 Changes in lipid content Variations in the total lipid content of mud shrimp during frozen storage are presented in Fig. 3a. The initial lipid content of shrimp samples was 0.699 g/100 g. The lipid content of rosemary-glazed shrimp decreased slower than other shrimp samples and showed a higher level during most of the frozen storage. While in unglazed and water-glazed shrimp, the lipid content decreased rapidly during 16 weeks of storage and then increased. After 16 weeks of frozen storage, the lipid content of unglazed, water-glazed, and rosemary-glazed shrimps decreased to 0.337, 0.365, and 0.470 g/100 g, respectively. In general, there was no significant difference in lipid content of shrimp among the three treatments. The decrease in total lipid content may be due to lipid oxidation and selective lipolysis of triglyceride and phospholipids, which altered the chemical composition of shrimp muscle (Romotowska, Karlsdóttir, Gudjónsdóttir, Kristinsson, & Arason, 2016). Soyer et al. (2010) reported that phospholipid content in chicken meat were affected by prolonged frozen storage. 3.5.2 Changes in FFA The formation of free fatty acid (FFA) is measured to evaluate the degree of lipid hydrolysis. Since FFA is more prone to oxidation than esterified fatty acids, lipid hydrolysis is a major factor that affects lipid oxidation (de Abreu, Losada, Maroto, & Cruz, 2011). Changes in FAA of unglazed, water-glazed, and rosemary-glazed mud shrimp during frozen storage are shown in Fig. 3b. The FFA content in unglazed 17
shrimp was significantly (P < 0.05) higher than FFA content in glazed shrimps after 4 weeks of frozen storage. During the whole frozen storage, the FFA content of unglazed shrimp increased rapidly (P < 0.05) from an initial value of 3.67 to a high value of 7.37 g/100 g lipids, indicating the extensive hydrolysis of lipids. While for water-glazed and rosemary-glazed shrimp, the FFA content increased to 6.49 and 5.88 g/100 g lipids, respectively, after 24 weeks of storage. The data revealed that glazing treatment could be able to control the lipid hydrolysis development in shrimp during frozen storage. EmİR ÇOban (2013) also reported that glazing with essential oil could lower the FFA in rainbow trout (Oncorhynchus mykiss) fillet compared with the control during frozen storage. There was no significant difference in FFA content between water-glazed and rosemary-glazed shrimp except at the 24th week. 3.5.3 Changes in PV The peroxide value (PV) was employed to measure the formation of primary lipid oxidation products that determine the extent of lipid oxidation at the initial stages of oxidation. Changes in PV of all mud shrimp samples during frozen storage are shown in Fig. 3d. The PV in unglazed shrimp showed a marked increase (P < 0.05) from the initial value of 2.19 to 4.06 meq/kg after 16 weeks of storage and decreased thereafter to 1.27 meq/kg after 24 weeks of storage. In water-glazed and rosemary-glazed shrimp, PV value increased slowly during 20 weeks of storage, and then increased to 3.44 and 4.41 meq/kg at the end of storage. The increase in PV was probably due to the faster rate of peroxides formation than degradation of peroxides into secondary oxidation products. The degradation of peroxides and formation of secondary 18
oxidation products resulted in the subsequent decrease in PV (Soyer et al., 2010). The unglazed shrimp reached the highest formation rate of PV at the 16 th week, much earlier than glazed shrimp samples, indicating that glazing treatment could effectively slow down the primary oxidation process in mud shrimp during frozen storage. During the frozen storage, a slower formation of PV was observed in rosemary-glazed shrimp, which may be attributed to the antioxidant properties of rosemary extract. According to the results, it is concluded that glazing and rosemary extract treatments had significant effect on delaying lipid oxidation in frozen mud shrimp. Sarabi et al. (2017) and Özyurt et al. (2011) also reported the anti-oxidative effect of rosemary extract on coated fried Escolar fish fillets and sea bream (Sparus aurata) during frozen storage. 3.5.4 Formation of fluorescent compounds (FC) The formation of fluorescent compounds (FC) is due to the interaction between primary and secondary lipids oxidation products and nucleophilic molecules such as proteins. The FC was measured using their fluorescence properties (FR value) in aqueous phases from the lipid extraction. The changes in FR value of unglazed, water-glazed, and rosemary-glazed shrimp during frozen storage are shown in Fig. 3d. The FR value of all shrimp samples increased gradually during frozen storage and then decreased slightly at the end of storage. The FR value of unglazed shrimp was higher than that of glazed shrimp samples during frozen storage, and significant differences (P < 0.05) were found in FR value at 8th, 12th, and 24th weeks. The initial FR value of shrimp was 1.67, after 20 weeks of storage, FR value in unglazed, 19
water-glazed, and rosemary-glazed shrimp showed the highest value of 3.18, 2.71, and 2.89, respectively. There was no significant difference in FR value between water-glazed and rosemary-glazed shrimp during the frozen storage. It is reported that the increase in FC formation is in agreement with the primary and secondary lipid oxidation compounds formation (Rodríguez et al., 2012). The FR value of unglazed shrimp was significantly higher than that of glazed shrimp samples, indicating a higher fluorescent compound formation in unglazed shrimp. The results showed that glazing treatment could protect mud shrimp from lipid oxidation by controlling the formation of oxidation compounds during frozen storage. Similar trend of fluorescent compound development was reported by García-Soto, Miranda, Barros-Velázquez, and Aubourg (2015), who showed that soaking with sodium metabisulphite solutions could inhibit the increase of FR value significantly in crustacean lobster krill (Munida spp.) during frozen storage at -18°C. 3.6 Sensory analysis The sensory profiles of unglazed, water-glazed and rosemary-glazed mud shrimp after different periods of frozen storage are shown in Fig. 4. The initial sensory score of all parameters (color, odor, texture, morphology, and cooking test) in shrimp samples was close to 6 (data not shown). In the first 12 weeks of storage there were no significant differences among all shrimp samples. After 16 weeks, an obvious sensory decline in the shrimp was observed for all samples and the differences among three groups of samples were found to be statistically significant (P < 0.05). The shrimp were considered to be unacceptable for human consumption when the total 20
score of sensory evaluation less than 15. Unglazed and water-glazed shrimp samples were acceptable up to 16 and 20 weeks, and rosemary-glazed shrimp sample was acceptable during the whole 24 weeks of storage. The results indicated that rosemary-glazed sample could be retaining good quality characteristics in terms of sensory assessment during frozen storage, followed by water-glazed sample. These conclusions were also supported by the results of chemical quality analyses. Previous studies also reported that the rosemary extract-immersed shrimp and essential oils-glazed rainbow trout fillet showed slower decrease in sensory scores during storage, compared with the control sample (Cadun, Kışla, & Çaklı, 2008; EmİR ÇOban, 2013). 4. Conclusions Glazing treatment with either water or rosemary extract showed excellent performance in controlling the quality loss and protein and lipid changes of frozen mud shrimp. After 16 weeks of frozen storage, unglazed mud shrimp exhibited significant quality decline, such as sensory quality loss, protein degradation, and lipid oxidative damage. The glazed mud shrimp suffered less quality loss during the 24 weeks of frozen storage. In addition, glazing with rosemary extract appears to be more beneficial for long-term frozen storage, with lower TVB-N, drip loss, PV, FFA and higher lipid content and sensory scores. This study demonstrated the potential of rosemary extract as a natural glazing material for mud shrimp. Acknowledgments This research was funded by the Beijing Advanced Innovation Center for Food 21
Nutrition and Human Health (201502910110942) and National Science and Technology Ministry of China (2015BAD17B03). References Baron, C. P., KjÆrsgård, I. V. H., Jessen, F., & Jacobsen, C. (2007). Protein and lipid oxidation during frozen storage of rainbow trout (Oncorhynchus mykiss). Journal of Agricultural and Food Chemistry, 55(20), 8118-8125. Benjakul, S., Visessanguan, W., Thongkaew, C., & Tanaka, M. (2003). Comparative study on physicochemical changes of muscle proteins from some tropical fish during frozen storage. Food Research International, 36(8), 787-795. Cadun, A., Kışla, D., & Çaklı, Ş. (2008). Marination of deep-water pink shrimp with rosemary extract and the determination of its shelf-life. Food Chemistry, 109(1), 81-87. Cavonius, L. R., & Undeland, I. (2017). Glazing herring (Clupea harengus) fillets with herring muscle press juice: effect on lipid oxidation development during frozen storage. International Journal of Food Science & Technology, 52(5), 1229-1237. de Abreu, D. A. P., Losada, P. P., Maroto, J., & Cruz, J. M. (2011). Lipid damage during frozen storage of Atlantic halibut (Hippoglossus hippoglossus) in active packaging film containing antioxidants. Food Chemistry, 126(1), 315-320. EmİR ÇOban, Ö. (2013). Evaluation of essential oils as a glazing material for frozen rainbow trout (Oncorhynchus mykiss) fillet. Journal of Food Processing and Preservation, 37(5), 759-765. García-Soto, B., Miranda, J. M., Barros-Velázquez, J., & Aubourg, S. P. (2015). Quality changes during the frozen storage of the crustacean lobster krill (Munida spp.). European Journal 22
of Lipid Science and Technology, 117(4), 431-439. Haghshenas, M., Hosseini, H., Nayebzadeh, K., Kakesh, B. S., Mahmoudzadeh, M., & Fonood, R. K. (2015). Effect of beta glucan and carboxymethyl cellulose on lipid oxidation and fatty acid composition of pre-cooked shrimp nugget during storage. LWT - Food Science and Technology, 62(2), 1192-1197. He, Q., & Xiao, K. (2016). The effects of tangerine peel (Citri reticulatae pericarpium) essential oils as glazing layer on freshness preservation of bream (Megalobrama amblycephala) during superchilling storage. Food Control, 69(Supplement C), 339-345. Kong, C., Wang, H., Li, D., Zhang, Y., Pan, J., Zhu, B., & Luo, Y. (2016). Quality changes and predictive models of radial basis function neural networks for brined common carp (Cyprinus carpio) fillets during frozen storage. Food Chemistry, 201, 327-333. Lefevre, F., Fauconneau, B., Thompson, J. W., & Gill, T. A. (2007). Thermal denaturation and aggregation properties of atlantic salmon myofibrils and myosin from white and red muscles. Journal of Agricultural and Food Chemistry, 55(12), 4761-4770. Li, D., Jia, S., Zhang, L., Li, Q., Pan, J., Zhu, B., Prinyawiwatkul, W., & Luo, Y. (2017). Post-thawing quality changes of common carp (Cyprinus carpio) cubes treated by high voltage electrostatic field (HVEF) during chilled storage. Innovative Food Science & Emerging Technologies, 42(Supplement C), 25-32. Li, D., Jia, S., Zhang, L., Wang, Z., Pan, J., Zhu, B., & Luo, Y. (2017). Effect of using a high voltage electrostatic field on microbial communities, degradation of adenosine triphosphate, and water loss when thawing lightly-salted, frozen common carp (Cyprinus carpio). Journal of Food Engineering, 212(Supplement C), 226-233. 23
Li, T., Hu, W., Li, J., Zhang, X., Zhu, J., & Li, X. (2012). Coating effects of tea polyphenol and rosemary extract combined with chitosan on the storage quality of large yellow croaker (Pseudosciaena crocea). Food Control, 25(1), 101-106. Lina, R., Yanshun, X., Qixing, J., Wenshui, X., & Chunjiang, Q. (2013). Investigation on structural changes of myofibrillar proteins from Silver Carp (Hypophthalmichthys molitrix) during frozen storage. Food Science and Technology Research, 19(6), 1051-1059. Lu, H., Wang, H., & Luo, Y. (2017). Changes in protein oxidation, water-holding capacity, and texture of bighead carp (Aristichthys Nobilis) fillets under chilled and partial frozen storage. Journal of Aquatic Food Product Technology, 26(5), 566-577. Lu, H., Zhang, L., Li, Q., & Luo, Y. (2017). Comparison of gel properties and biochemical characteristics of myofibrillar protein from bighead carp (Aristichthys nobilis) affected by frozen storage and a hydroxyl radical-generation oxidizing system. Food Chemistry, 223(Supplement C), 96-103. Mesarčová, L., Marcinčák, S., Nagy, J., Popelka, P., Bača, M., Jevinová, P., & Marcinčáková, D. (2013). Effect of glaze and selected herbal extracts on lipid oxidation and sensory properties of frozen Atlantic herrings (Clupea harengus L.). Acta Alimentaria, 42(2), 236-244. Özyurt, G., Özkütük, A. S., & Polat, A. (2011). Capability of the rosemary (Rosmarinus officinalis) extract on the oxidative stability of cooked sea bream (Sparus aurata) during frozen storage. Journal für Verbraucherschutz und Lebensmittelsicherheit, 6(2), 167-174. Qiu, C., Xia, W., & Jiang, Q. (2014). Pressure-induced changes of silver carp 24
(Hypophthalmichthys molitrix) myofibrillar protein structure. European Food Research and Technology, 238(5), 753-761. Rocío Teruel, M., Dolores Garrido, M., Espinosa Vicente, M., & Linares, M. (2015). Effect of different format-solvent rosemary extracts (Rosmarinus officinalis) on frozen chicken nuggets quality. Food Chemistry, 172, 40-46. Rodríguez, A., Cruz, J. M., Paseiro-Losada, P., & Aubourg, S. P. (2012). Effect of a polyphenol–vacuum packaging on lipid deterioration during an 18-month frozen storage of coho salmon (Oncorhynchus kisutch). Food and Bioprocess Technology, 5(6), 2602-2611. Romotowska, P. E., Karlsdóttir, M. G., Gudjónsdóttir, M., Kristinsson, H. G., & Arason, S. (2016). Influence of feeding state and frozen storage temperature on the lipid stability of Atlantic mackerel (Scomber scombrus). International Journal of Food Science & Technology, 51(7), 1711-1720. Sánchez-Alonso, I., Carmona, P., & Careche, M. (2012). Vibrational spectroscopic analysis of hake (Merluccius merluccius L.) lipids during frozen storage. Food Chemistry, 132(1), 160-167. Sarabi, M., Keramat, J., & Kadivar, M. (2017). Antioxidant effect of rosemary extract and BHT on the quality of coated fried Escolar (Lipidocybium flavobrunium) fish fillets during frozen storage. International Food Research Journal, 24(2), 525-533. Seabra, L. M. J., Damasceno, K. S. F. S. C., Andrade, S. A. C., Dantas, M. M. G., Soares, N. K. M., & Pedrosa, L. F. C. (2011). Effect of rosemary on the quality characteristics of white shrimp (Litopenaeus vannamei). Journal of Food Quality, 34(5), 363-369. 25
Soares, N. M. F., Oliveira, M. S. G., & Vicente, A. A. (2015). Effects of glazing and chitosan-based coating application on frozen salmon preservation during six-month storage in industrial freezing chambers. LWT - Food Science and Technology, 61(2), 524-531. Solval, K. M., Espinoza Rodezno, L. A., Moncada, M., Bankston, J. D., & Sathivel, S. (2014). Evaluation of chitosan nanoparticles as a glazing material for cryogenically frozen shrimp. LWT - Food Science and Technology, 57(1), 172-180. Soyer, A., Özalp, B., Dalmış, Ü., & Bilgin, V. (2010). Effects of freezing temperature and duration of frozen storage on lipid and protein oxidation in chicken meat. Food Chemistry, 120(4), 1025-1030. Sundararajan, S., Prudente, A., Bankston, J. D., King, J. M., Wilson, P., & Sathivel, S. (2011). Evaluation of green tea extract as a glazing material for shrimp frozen by cryogenic freezing. Journal of Food Science, 76(7), E511-E518. Taheri, A. (2015). Antioxidative effect of rainbow sardine (Dussumieria acuta) protein hydrolysate on lipid and protein oxidation in Black Pomfret (Parastromateus niger) fillet by glazing. Journal of Aquatic Food Product Technology, 24(3), 241-258. Tironi, V. A., Tomás, M. C., & Añón, M. C. (2010). Quality loss during the frozen storage of sea salmon (Pseudopercis semifasciata). Effect of rosemary (Rosmarinus officinalis L.) extract. LWT - Food Science and Technology, 43(2), 263-272. Wu, H., Wang, Z., Luo, Y., Hong, H., & Shen, H. (2014). Quality changes and establishment of predictive models for Bighead Carp (Aristichthys nobilis) fillets during frozen storage. Food and Bioprocess Technology, 7(12), 3381-3389. 26
Xiong, G., Cheng, W., Ye, L., Du, X., Zhou, M., Lin, R., Geng, S., Chen, M., Corke, H., & Cai, Y.-Z. (2009). Effects of konjac glucomannan on physicochemical properties of myofibrillar protein and surimi gels from grass carp (Ctenopharyngodon idella). Food Chemistry, 116(2), 413-418. Xu, Z., Liu, X., Wang, H., Hong, H., & Luo, Y. (2017). Comparison between the Arrhenius model and the radial basis function neural network (RBFNN) model for predicting quality changes of frozen shrimp (Solenocera melantho). International Journal of Food Properties, 20(11), 2711-2723. Xu, Z., Liu, X., Wang, H., Hong, H., Yu, X., & Luo, Y. (2016). Establishment of the Arrhenius Model and the Radial Basis Function Neural Network (RBFNN) Model to predict quality of thawed shrimp (Solenocera melantho) stored at different temperatures. Journal of Food Processing and Preservation, 40(5), 882-892. Yerlikaya, P., Gokoglu, N., & Topuz, O. K. (2010). Use of natural plant extracts in batter coating of shrimp and their effects on the quality of shrimp during frozen storage. Journal of Food Processing and Preservation, 34(1), 127-138. Yuan, G., Lv, H., Tang, W., Zhang, X., & Sun, H. (2016). Effect of chitosan coating combined with pomegranate peel extract on the quality of Pacific white shrimp during iced storage. Food Control, 59(Supplement C), 818-823.
Figure captions Fig. 1. Changes in (a) TVB-N, (b) drip loss, (c) SH, and (d) disulfide bond of 27
unglazed, water-glazed, and rosemary-glazed mud shrimp during frozen storage at -20 °C. Fig. 2. Changes in the intrinsic fluorescence intensity (IFI) of myofibrillar proteins from (a) unglazed, (b) water-glazed, and (c) rosemary-glazed mud shrimp during frozen storage at -20 °C. Fig. 3. Changes in (a) lipid content, (b) FFA, (c) PV, and (d) fluorescent compound of unglazed, water-glazed, and rosemary-glazed mud shrimp during frozen storage at -20 °C. Fig. 4. Profiles of sensory analysis of unglazed, water-glazed, and rosemary-glazed mud shrimp after 4 weeks, 8 weeks, 12 weeks, 16 weeks, 20weeks, and 24 weeks of frozen storage at -20 °C.
28
TVB-N (mg/100 g)
30 25 20
b
Unglazed Water-glazed Rosemary-glazed
Drip loss (%)
a
15 10 5 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26
20 Unglazed 18 Water-glazed 16 Rosemary-glazed 14 12 10 8 6 4 2 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26
5
8
d
Unglazed Water-glazed Rosemary-glazed
disulfide bond content (mol/10 g protein)
9
Storage time (week)
7
5
c
SH content (mol/10 g protein)
Storage time (week)
6 5 4 3 2 0 2 4 6 8 10 12 14 16 18 20 22 24 26
5.0 4.5 4.0 3.5 3.0 2.5
Unglazed Water-glazed Rosemary-glazed
2.0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Storage time (week)
Storage time (week)
Fig. 1. Changes in (a) TVB-N, (b) drip loss, (c) SH, and (d) disulfide bonds of unglazed, water-glazed, and rosemary-glazed mud shrimp during frozen storage at -20 °C.
29
3500 fresh 8w 16w 24w
3000 2500 2000 1500 1000 500 0
320
340
360
380
b fluorescence intensity (FI)
fluorescence intensity (FI)
a
fluorescence intensity (FI)
fresh 8w 16w 24w
3000 2500 2000 1500 1000 500 0
400
Wavelength (nm)
c
3500
320
340
360
380
400
Wavelength (nm)
3500 fresh 8w 16w 24w
3000 2500 2000 1500 1000 500 0
320
340
360
380
400
Wavelength (nm)
Fig. 2. Changes in the intrinsic fluorescence intensity (IFI) of myofibrillar proteins from (a) unglazed, (b) water-glazed, and (c) rosemary-glazed mud shrimp during frozen storage at -20 °C.
30
Lipid content (g/100g)
0.8 0.7
Unglazed Water-glazed Rosemary-glazed
b
0.6 0.5 0.4 0.3 0.2 0.1 0 2 4 6 8 10 12 14 16 18 20 22 24 26
Free fatty acid (g/100 g lipids)
a
8 7 6 5 4 3 2 1
0 0 2 4 6 8 10 12 14 16 18 20 22 24 26
Storage time (week)
Unglazed 5.0 Water-glazed 4.5 Rosemary-glazed 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 2 4 6 8 10 12 14 16 18 20 22 24 26
Storage time (week)
d
4.0 3.5 3.0
FR value
PV (meq/kg)
c
Unglazed Water-glazed Rosemary-glazed
2.5 2.0 1.5 1.0 0.5
Unglazed Water-glazed Rosemary-glazed
0.0 0 2 4 6 8 10 12 14 16 18 20 22 24 26
Storage time (week)
Storage time (week)
Fig. 3. Changes in (a) lipid content, (b) FFA, (c) PV, and (d) fluorescent compounds of unglazed, water-glazed, and rosemary-glazed mud shrimp during frozen storage at -20 °C.
31
Fig. 4. Profiles of sensory analysis of unglazed, water-glazed, and rosemary-glazed mud shrimp after 4 weeks, 8 weeks, 12 weeks, 16 weeks, 20weeks, and 24 weeks of frozen storage at -20 °C.
32
Table 1. Changes of LF-NMR relaxation time (T2) and percentage of each relaxation component in mud shrimp during frozen storage (UG: Unglazed; WG: Water-glazed; RG: Rosemary-glazed).
Storage time (week) Parameters
T2b (ms)
T21 (ms)
T22 (ms)
P2b (%)
P21 (%)
P22 (%)
Treatment 0
8
16
24
UG
2.4±0.4Aa
2.5±0.4Aab
3.0±0.3Aa
4.7±0.8Ba
WG
2.4±0.4Aa
2.7±0.1ABa
2.2±0.7Aa
3.5±1.1Ba
RG
2.4±0.4Aa
2.2±0.3Ab
2.0±1.0Aa
3.7±1.3Ba
UG
44.9±3.0Aa
43.9±2.3ABa
42.2±2.7ABa
40.9±2.2Ba
WG
44.9±3.0Aa
42.8±1.2ABa
41.6±1.6Ba
41.4±2.3Bab
RG
44.9±3.0Aa
43.4±3.2Aa
42.8±2.5Aa
44.1±1.6Ab
UG
318.3±41.2Aa
674.9±120.0Ba
693.2±111.8Ba
648.6±203.9Ba
WG
318.3±41.2Aa
623.3±187.2Ba
484.2±92.0ABb
589.1±153.6Ba
RG
318.3±41.2Aa
823.8±182.8Ca
711.9±99.6BCa
589.8±167.6Ba
UG
2.7±0.3ABa
2.5±0.3Aa
3.0±0.4BCa
3.4±0.4Ca
WG
2.7±0.3ABa
2.4±0.1Ba
2.7±0.4ABa
3.1±0.6Ba
RG
2.7±0.3ABa
2.4±0.1Aa
3.2±0.4BCa
3.4±0.5Ca
UG
94.3±0.9Aa
96.0±0.3Ca
95.7±0.4BCa
95.1±0.5Ba
WG
94.3±0.9Aa
96.1±0.4Ba
95.8±0.7Ba
95.3±0.4Ba
RG
94.3±0.9Aa
96.0±0.2Ca
95.3±0.4Ba
95.3±0.1Ba
UG
3.0±0.8Aa
1.6±0.2Ba
1.3±0.1Ba
1.5±0.4Ba
WG
3.0±0.8Aa
1.5±0.3Ba
1.5±0.4Ba
1.7±0.3Ba
RG
3.0±0.8Aa
1.6±0.2Ba
1.6±0.4Ba
1.4±0.5Ba
The same capital letters on the same row represented that there was no significant difference between the values at different storage time (P > 0.05); The same lowercase letter on the same column represented that there was no significant difference between the values under different treatment (P > 0.05).
33
Highlights 1. First study to apply rosemary extract in glazing treatment on frozen mud shrimp. 2. Unglazed shrimp showed a significant decline in quality after 16 weeks of storage. 3. Glazing reduced loss of quality, and protein and lipid changes effectively in shrimp. 4. Rosemary extract can be used as a glazing material for preservation of mud shrimp.
34