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Chicken processing by-product: A source of protein for fat uptake reduction in deep-fried chicken
Journal Pre-proof Chicken Processing By-Product: A Source of Protein for Fat Uptake Reduction in Deep-Fried Chicken
Daniel Ananey-Obiri, Lovie Matthews, Reza Tahergorabi PII:
S0268-005X(19)31460-2
DOI:
https://doi.org/10.1016/j.foodhyd.2019.105500
Reference:
FOOHYD 105500
To appear in:
Food Hydrocolloids
Received Date:
01 July 2019
Accepted Date:
06 November 2019
Please cite this article as: Daniel Ananey-Obiri, Lovie Matthews, Reza Tahergorabi, Chicken Processing By-Product: A Source of Protein for Fat Uptake Reduction in Deep-Fried Chicken, Food Hydrocolloids (2019), https://doi.org/10.1016/j.foodhyd.2019.105500
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. 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. © 2019 Published by Elsevier.
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Graphical abstract: Chicken Processing By-Product: A Source of Protein for Fat Uptake Reduction in Deep-Fried Chicken
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Chicken Processing By-Product: A Source of Protein for Fat Uptake Reduction in DeepFried Chicken
Daniel Ananey-Obiri, Lovie Matthews, and Reza Tahergorabi *
Food and Nutritional Sciences Program, North Carolina Agricultural and Technical State University, Greensboro, NC, USA
*All correspondence should be addressed to Dr. Reza Tahergorabi Tel: (336) 285-4865 E-mail address: [email protected]
Original manuscript Submitted to Food Hydrocolloids
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Abstract Chicken processing generates large quantities of by-products which can be used a source of protein for fat uptake reduction in fried chicken industry. This study investigated the use of edible coating prepared from chicken protein (CP) recovered using isoelectric precipitation/solubilization (ISP) from chicken drumstick processing by-products as a fat blocker in deep-fat fried chicken drumsticks samples. The samples were coated with edible coating at three different CP concentrations 5, 10, or 15% w/w and subsequently dipped in batter and breaded prior to deep frying. Deep-fat fried samples without edible coating served as control. The samples were deep-fried at 177oC for 3-4 min. Proximate composition, pH, texture, frying yield and sensory properties of the samples were tested. Total fat content of deep-fried samples with 15% coating showed the lowest amount of absorbed fat, about 60% less than the control. No difference was found between the color, pH and sensory properties of the coated and uncoated samples. However, uncoated samples were harder than coated samples. Also, samples coated with coating had higher moisture content and frying yield after frying, compared to uncoated samples. The development of low-fat fried foods using this approach would allow consumers to enjoy the taste and texture that is characteristic of fried food. At the same time, the food industry can reduce the environmental issues due to disposal of chicken processing by-products. The use of chicken proteins as an edible coating on fried chicken is novel and product friendly.
Keywords: chicken processing by-products; edible coating; deep-frying; low-fat food
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1. Introduction In the US, poultry processors transform 8.6 billion chicken to chicken products, annually (USDA, 2018). When chicken is mechanically processed for different products, large quantities of by-products are generated. Chicken processing by-products includes trimmings, meat-left-on bones, and skins which are discarded or used as low-value restructured food products. Meat industries are laden with the cost of disposing processing by-products; not to talk about the environmental concerns these by-products pose to the environment (Tahergorabi, Sivanandan & Jaczynski, 2011). Fried chicken industry is one of the sectors in food industry which uses large amount of processed chicken. As a result, it contributes to chicken processing by-products generation and subsequent consequences. Fried foods are very popular in the US and around the world due to their irresistible taste, desirable color, and crispy texture that are developed because of this method of cooking. However, the process of frying increases the total fat content of fried foods, consequently increasing the energy density of the foods (Echarte, Zulet, & Astiasaran, 2001; Sanchez-Muniz, 2006). Several findings have associated the consumption of fried foods with the development of cardiovascular diseases, obesity, and type-2 diabetes (Soriguer et al., 2003; Cahill et al., 2014). Estimated health care costs due to obesity, and related complications and comorbidities in the United States range from $147 billion to nearly $210 billion per year (Cawley, & Meyerhoefer, 2012). In addition, job absenteeism due to obesity costing approximately $4.3 billion annually (Cawley, Rizzo, & Haas, 2007) and with lower productivity while at work, costing employers $506 per obese worker per year (Gates, Succop, Brehm, Gillespie, & Sommers, 2008). Thus, due to consumers’ demand for healthier products,
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development of meat products with reduced fat content has been triggered (Das, Pawar, & Modi, 2013). According to Mellema (2003), the application of coating is a propitious route for decreasing fat-uptake since the surface properties of foods majorly contribute to fat-uptake. The use of hydrocolloids as edible coatings has been extensively explored (Izadi, Ojagh, Rahmanifarah, Shabanpour, & Sakhale, 2015). Polysaccharides such as cellulose, starch, gums have widely been explored as edible coating in deep-fat fried foods. Conversely, they have demonstrated poor barrier to moisture, thus, reducing juiciness and allowing for fat-uptake in deep fried foods. Lipid-based edible coatings have also demonstrated damaging effect on the appearance and gloss of the coated food (Hassan, Chatha, Hussain, Zia, & Akhtar, 2018). Proteins from both plant and animal sources have been used as edible coating for reducing fat content in deep-fat fried foods. Comparatively, protein-based edible coatings have been documented to reduce fat uptake in deep fat fried foods more than other hydrocolloids. Angor (2016) reported soy protein isolate (SPI) at four different concentrations (2, 6, 10 and 14%) to reduce fat-uptake more than carboxymethyl cellulose (MC) at equivalent concentrations in deep fried potato pellet chips. In another study, the use of SPI and whey protein isolate in edible coating reduced fat-uptake in deep fried cereal product to about 80 and 86%, respectively; whereas methyl cellulose (MC) resulted in 58% reduction in fat-uptake (Albert & Mittal, 2002). In addition, edible films and coatings made from proteins are the preferred among all the other biopolymers, due to their nutritional worth (Feng, Wu, Liu, Li, jiang et al., 2018). Yet, issues related to the allergenicity of some proteins such as soy, whey, egg albumen, and wheat have restricted their broad use (Zhao & Lin, 2007). Unlike the other proteins, there is paucity of
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literature on the use of proteins from animal source as edible coating. He, Franco, and Zhang, (2015) investigated fish protein hydrolysate (FPH) as an edible coating in deep-fat fried foods. Fish cakes coated with these proteins had significant fat reduction from 11% to about 1%. Grievous concerned with foods developed from FPH ingredients is off flavor and bitter taste associated with these foods (Kristinsson & Rasco, 2000; Dauksas, Slizyte, Rustad, & Storro, 2004). Stromal and myofibrillar proteins found in meat food proteins are used for making edible films and coatings (Tahergorabi, Hosseini, & Jaczynski, 2011). The film-forming and thermal gelation properties of proteins make them good materials for reducing fat absorption in deepfrying (Brannan, Mah, Schott, Yuan, Casher, Myers, Herrick, 2014). Films made from proteins can form bonds at different positions and offer high potential for forming numerous linkages. Myofibrillar proteins are able to form continuous matrix during drying due to their fully stretched and closely related structures arranged in parallel (do A. Sobral, dos Santos, & García,2005). Myosin a type of myofibrillar protein can also form a 3-dimensional network structure that prevents water escape when gels (Nakano, Ishioroshi, Samejima, & Yasui, 1979). In addition, animal products such as chicken provide almost three-fourths of the essential amino acids in food supply and contribute about 67% of the total protein, indicating a greater concentration of these vital nutrients such as vitamin B12, B6, riboflavin, niacin, phosphorus, and calcium (Link-swiler, 1982). No literature has exploited the use of chicken muscle protein as an edible coating for reducing fat-uptake in deep-fat fried foods. The objective of this study was to evaluate the potential of protein isolated from chicken processing by-products as an edible coating in reducing fat-uptake in deep-fat fried chicken drumsticks.
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2. Materials and Methods 2.1.
Chicken Collection and Preparation Fresh drumstick (skin-on bone-in) was purchased from a local grocery and they were cut
into pieces of 10 ± 1 g. The strips were kept in a refrigerator at 4oC immediately after the cutting process. 2.2.
Brine Washing of Minced Chicken Trimmings, skins-and-meat left on bone from chicken drumsticks, collectively
considered as by-products were ground uniformly using a meat grinder (LEM grinder, 5 Big Bite Grinder-0.35 HP, West Chester, OH, USA) with a hole diameter of 0.5 cm, and washed according to the method described by Tongnuanchan et. al, (2011), with slight modifications. The ground chicken drumstick was homogenized with 0.05M cold NaCl (2–4 °C) at a speed of 13,000 rpm for 2 min at 1:5 ratio (ground chicken drumstick – NaCl w: v) using a laboratory homogenizer (Homogenizer, OMNI International, Kenneswa, GA, USA) at a speed of 13,000 for 2 min. This was followed by centrifuging at 5000 x g for 20 min at 4oC, using a refrigerated centrifuge (Thermo Scientific, Model ST 16 Centrifuge Series, Asheville, NC, USA). The washing process was repeated twice. 2.3.
Protein Isolation Protein was isolated from the washed ground chicken according to the method described
by Tahergorabi et al., (2011b) (Fig. 1). Washed chicken meat was homogenized with deionized cold water (dd H2O) at 1:6 ratio (washed meat: water, w: v) using a laboratory homogenizer (Homogenizer, OMNI International, Kenneswa, GA, USA) set at speed five for 5 min. Ice cubes were used to control the temperature of the mixture at approximately 4 °C. Homogenization process was controlled at speed three in successive pH adjustment.
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A fraction of the homogenate, about 6 L was transferred into a beaker and the pH adjusted with 10 N NaOH to 11.50 ± 0.05 and held for 10 mins. The solution was centrifuged for 20 min at 5,000 x g and 4oC (Thermo Scientific, Model ST 16 Centrifuge Series, Asheville NC, USA). This resulted in three distinct layers; comprising of a top layer of oil, middle layer of chicken muscle protein solution, and a bottom layer of insoluble membranes, etc. The middle layer containing the chicken protein muscle was collected into a beaker and pH adjusted with 6 N HCl to 5.5 ± 0.05 to isoelectrically precipitate the protein. The solution was allowed to react for about 8-10 minutes. The solution was centrifuged for 20 min at 5,000 x g and 4oC (Thermo Scientific, Model ST 16 Centrifuge Series, Asheville NC, USA). This resulted in two layers: a top layerspent water, bottom layer-de-watered chicken protein. The dewatered protein was collected and referred to as chicken protein isolate (CPI). This protein was used in the preparation of the edible coating. Insert Fig. 1
2.4.
Quantitation of Protein in Isolate
The protein content of the CPI was determined using the Bradford protein assay (Bradford, 1976), with some modifications. This assay works on the principle of color change from brown to blue as the dye Coomassie Blue G250 binds to protein. Set of standards were prepared from Bovine serum albumin by dissolving it in a solution containing 0.1M NaOH and 3.5% NaCl. Also, 0.5 g of the CPI recovered with ISP was homogenized with 30 ml of 0.1M NaOH and 3.5% sodium chloride using a laboratory homogenizer (Homogenizer, OMNI International, Kennesaw, GA, USA). The resulting homogenate was centrifuged at 4000 x g at 4oC for 30 minutes, and the supernatant was collected and used for protein analysis. 20 µl of both the
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standards and the samples were plated into individual wells of a microplate in triplicates. 200µl of the Bradford reagent was added into wells containing the standards and samples. The plates were incubated at 37oC for 20 minutes and the absorbance read at 595 nm using a spectrophotometer 2.5.
Edible Coating Preparation Chicken protein isolate was formulated with water to form edible coating concentrations:
5, 10 and 15% (w/w) protein. Glycerol was also added as plasticizer at 0.4% (w/w) of the protein. The pH of the mixture was adjusted with 10 N NaOH to 11± 0.05 to solubilize the proteins. It was afterwards homogenized at 13,000 rpm for 1 min using a laboratory homogenizer (Homogenizer, OMNI International, Kenneswa, GA, USA). The pH was finally re-adjusted using 6 N HCl to approximately 7± 0.05. The edible coatings were kept refrigerated (4oC) for up to 12 hours before use. 2.6.
Preparation of Batter Batter formulation was based on Sahin, Sumnu, and Altunakar (2005), with slight
modification. It was formulated as follows; 48.7% (w/w) wheat flour (King Arthur Flour Company, Vermont, USA), 48.75% cornstarch (ACH Food Companies, Memphis, USA), 1.0% of (HPMC) (Methocel E15 Premium LV Hydroxypropyl Methylcellulose, Midland, USA), 1.0% salt (Morton, Chicago, USA), 0.5% baking powder (Rumford, Terre Haute, USA), and deionized water. The mixture was stirred, and standardization test conducted thereafter. The standardization of the batter was based on its viscosity, using a modified Stein Cup. A 4 inchdiameter funnel was used in place of the Stein Cup. The funnel was filled to the brim with the batter, and the viscosity of the batter was considered standard when all the batter drains through the hole in 11 seconds.
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2.7.
Chicken Samples Preparation for Frying The mass of each chicken strip was determined before and after the application of the
coating. Using a hand-held prong, chicken pieces were dipped in edible coating containing either 5%, 10%, or 15 % w/w protein after predusting, if coating was required. The samples were gently shaken to get rid of excess coating. They were accordingly dipped either in a batter. Lastly, the samples were gently rolled in breadcrumbs to allow for evenly breading. The weight of the breaded chicken samples was recorded before and after frying. 2.8.
Frying Process Chicken samples were fried at 177.7oC for 3-4 min in a deep fryer (Presto® Dual
ProFryTM/1800W, National Presto Industries Inc., WI., U.S.). Intermittently, the frying temperature was checked using data logging thermometer. Prongs were used to remove the fried chicken strips from the oil after the stipulated time. The samples were allowed to drip for few seconds. The fried chicken pieces were kept on white paper tissue and allowed to cool at ambient temperature with natural air. Analysis of the samples proceeded immediately after this process. 2.9.
Fat Analysis The lipid content was determined quantitatively by Soxhlet extraction method
(AOAC, 2010). About 3-4 g of the sample was measured into a disposable aluminum dish. The sample was dried in an oven for 1 ½ h at 125oC. The sample was cooled and transferred into an extraction thimble. The weight of an extraction flask was determined, and about 85mL of petroleum ether was then added to the flask. Extraction process was done for a minimum of 80 cycles in about 6 h. After the extraction process, the flask was heated over a water bath at 4262oC for few minutes. The flask was dried in an oven at 100oC -102oC for few minutes and cooled to room temperature. Fat content was calculated using the equation below:
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Fat content (%) =
Fat uptake (%) =
2.10.
Weight of flask and extracted fat (g) ― Weight of empty flask (g) × 100 weight of sample prior to extraction (g)
Fat content of sample after frying (g) ― Fat content of sample before frying(g) × 100 Fat content of sample prior to frying(g)
Moisture Analysis
Average moisture content of fried chicken strips was analyzed according to AOAC (2000). The samples were ground separately into fine particles in a laboratory grinder (LEM grinder, 5 Big Bite Grinder-0.35 HP, West Chester, OH, USA). About 1-3 g of the ground sample was transferred into an empty pre-weighed dish in a vacuum oven (Precision Scientific vacuum oven, model 19, Chicago, Il, USA). The samples were evenly spread with a spatula in the dish. Samples were left to dry at 105oC for 3 h. After this, the samples were cooled and weighed. The moisture content (MC) of each sample was calculated using the equation below: MC (%) =
2.11.
Weight of sample before drying (g) ― weight of sample after drying × 100 weight of sample before drying
Ash Content
The ash content of the fried samples was determined as follows. The weights of empty crucibles were taken and recorded (W1). In each crucible, 2 g of samples were added, and the total weight was recorded (W2). The crucible with the content were furnace (Thermo Fisher, Lindberg/ Blue M Moldatherm Box Furnace, Waltham, MA, USA) and heated at 550oC for 24 h in a furnace. The crucibles were removed, cooled to room temperature, and the weight of the crucible containing the ash was recorded (W1). The ash content was calculated as follows; Ash (%) =
(𝑊3 ― 𝑊1) (𝑊2 ― 𝑊1)
× 100%2.12. Frying yield
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The frying yield was determined by measuring the weight of the sample before and after frying, and it was calculated as follows: Frying yield (%) =
2.13.
weight of sample after frying (g) × 100% weight of sample before frying (g)
Color Determination
In each case, a piece of plastic wrap was put on the samples 5 min after frying, and color was determined. The color properties of the sample were measured using Minolta Chroma Meter CR-400 colorimeter (Minolta Camera Co. Ltd., Japan). The tristimulus color values L* (Lightness), a* (red) and b* (yellow) values were generated by the colorimeter to describe the color characteristics of the fried samples. The color readings were repeated thrice for each chicken sample, the mean values were reported. The colorimeter was calibrated before used. 2.14.
pH Determination
The pH of the samples was determined according to Alakhrash, Anyanwu, & Tahergorabi, (2016), but with slight modifications. Chicken sample (5 g) was homogenized (Homogenizer, OMNI International, Kenneswa, GA, USA) with 20ml of dd H2O at 13,000 for 1 min. A calibrated hand-held pH meter (OMNI International, Kenneswa, GA, USA) was used to measure the pH after it was calibrated. 2.15.
Texture analysis
The textural property of each fried sample was analyzed by puncture test using texture analyzer (Model TA-XT2, Texture Analyzer, Texture Technologies Corp., Scarsdale, NY, USA). The puncture test was done at 5 mm/s using a 1/8 spindle, with 15% penetrating thickness penetration of the crust. The height of the peak is measured as the hardness of the peak.
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2.16.
Sensory Evaluation
Sensory evaluation of fried chicken samples was conducted after approval was sought from institutional review board (IRB). Untrained panelists were recruited to evaluate the acceptability of the various treatments of fried chicken samples. Fresh fried chicken drumsticks were served to participants in a well-lit and ventilated room on coded white plates. They evaluated the samples based on their appearance, color, texture, and odor using 9 points hedonic scale. Participants ranked the fried products on a scale of 1 to 9 with 1= “dislike extremely and 9 = “Like extremely”. The responses on various attributes of the samples were analyzed statistically and mean values were reported. 2.17.
Statistical Analysis
The experiments were triplicated independently. The mean values were reported as results ± standard deviation (SD). Analysis of variance ANOVA (SAS, version 16.0, SAS 49 Institute Cary, North Carolina) was used to determine effects at a significance level of p<0.05. The mean differences among the treatments were compared using Tukey’s test. 3.
Results and Discussion
3.1. Fat-uptake Table 1 shows the fat-uptake of deep-fat fried chicken drumstick samples coated with different concentrations of CP and battered. The use of edible coating at the three different concentration levels reduced fat-uptake in the deep-fat fried samples. The fat-uptake reductions obtained in edible coated fried samples, except in 5% CP samples were significantly higher (P < 0.05) than the control samples. The edible coating at the three levels of protein concentration, 5% CP, 10% CP and 15% CP reduced fat-uptake to more than 35, 50 and 60%, compared to control
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samples, respectively. Evidently, as protein concentration increases in edible coating, fat absorption reduces in coated fried samples. The decrease in fat-uptake observed among samples coated with edible coating as opposed to control samples is due to the formation of complex network of films formed by the protein during frying. These networks are formed due the gelation of the myofibrillar proteins induced by heat. Chicken protein gelation comprises of several steps; starting from protein denaturation to irreversible aggregation of myosin head through the formation disulfide bond and helical-coil transition of the molecules’ tail, and a final step of forming a three-dimensional network (Lesiów & Xiong, 200; Ahhmed et al., 2009). One of the popular mechanisms that has been used to characterize fat-uptake during deep-frying is water replacement. During frying, the moisture in the food escape through pores and channels created in the food product. Subsequently, the voids and pores created due to the loss of moisture are filled with the oil (Ananey-Obiri, Matthews, Azahrani, Ibrahim, Galankis, Taherorabi, 2018). The complex network formed by the protein in the edible coating might have blocked the pores and cracks to prevent moisture escape and thus, subsequently preventing the oil absorption into the product during frying. The strength of the gel might have also been augmented by the use of ISP to recover the protein used in the edible coating, thus, reducing fat imbibition in the coated fried foods. Zhao et al (2017) demonstrated in their findings that proteins recovered using ISP produced strong gel. The fat-uptake reduction obtained in 10% CP samples was more than 50%. Compared to a previous study by Dragich and Krochta (2010) who obtained 30.68% fat-uptake reduction in wheat-flour-battered chicken strips coated with 10% whey protein denatured, the muscle protein produced a better result. Similarly, a study by Brannan and Pettit (2015)
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involving 10% whey protein as a postbreading dip reduced oil absorption by 37% in patties, which is almost equal to the reduction achieved with 5% CP samples in this study. The observed proportional reduction in fat content and fat-uptake among coated fried samples to protein concentration can be attributed to increasing aggregation and gelation of enough protein concentrations (Brannan et al., 2014). That is, the higher the protein concentration in the edible coating, the more complex network the molecules form to prevent fat from running into the food during frying. Mah and Brannan (2009) supported this assertion, by explaining that, the difference in the extent of the various concentrations as fat barriers is due the differences in protein molecules of the protein concentrations. The normal protein concentration for gelation to occur is 5 and 15% (Arntfield, Murray, & Ismond, 2007). 3.2. Moisture Moisture contents of coated and control deep fried samples are shown in Table 1. Moisture content is an important property of fried foods because it determines the characteristic qualities of the food. Edible coating containing 15% CP retained the highest amount of moisture in fried samples, but it was not significantly different (P > 0.05) from the other coated samples. Even though no significant difference in moisture content was observed among the various treatment, averagely, the highest moisture was retained in edible coated samples. That is, using edible coating retains moisture in deep-fat fried foods. Coating could form barriers that prevent moisture loss and subsequently reduce fat absorption (Singthong & Thongkaew, 2009). The network formed by the edible coating prevented the moisture from escaping, thus, retaining higher moisture content in coated samples than the uncoated sample (control). Although the moisture contents are not statistically different, they are numerically different. As seen in Table 1, the moisture content of the samples increased
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from 49% for control to 57% for samples coated with 15% edible coating. The complex network formed by the protein in the edible coating formed a film that covered the pores and channels created in the food during frying. This process reduces the incidence of moisture loss. The relatively lesser voids created in coated fried sample, unlike in the uncoated, reduced fat absorption during frying. 3.3. Ash Changes in ash content in coated and control samples as measured are displayed in Table 1. Though no significant changes (P > 0.05) in ash content was measured among the various treatments, the highest ash contents were obtained in coated deep-fat fried samples. Increasing protein concentration in the edible coating resultantly led to increasing ash content in deep fried coated samples. The use of edible coating increased the mineral content (calcium, phosphorus, sodium, potassium) and trace elements. The minerals increased with increasing protein concentration of the edible coating. Insert Table 1 3.4. Color The tristimulus color values of deep-fried chicken drumstick samples are shown in Table 2. No significant difference (P> 0.05) in L* values was observed among the various treatments. Interestingly, chicken samples coated with edible coating showed slight improvement (numerically) in L*, with 10% CP samples demonstrating higher L* values than control samples. Insert Table 2 3.5. Texture Meat product texture is an important quality determinant. Figure 2 displays the textural properties of coated and uncoated fried chicken samples. The texture of battered meat products is
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chiefly characterized by hardness, describing the qualities of the substrate, crunchiness, and the crust (Das et al., 2013). Puncture test is the recommended test for texture analysis of fried samples (Bourne, 2002). The puncture test revealed the hardness of the samples. Hardness is the defined as force that is needed to deform the sample at a certain distance (Brannan, 2007). Chicken samples coated with edible coating were commonly less hard than the controls. Similar to a study by Rayner, Ciolfi, Maves, Stedman, and Mittal (2000), deep-fried samples coated with 10% soy protein were softer than uncoated fried samples. Generally, edible coated fried samples had higher moisture content than the controls. Consumers’ favor soft and juicy interior battered and breaded deep-fat fried foods (Myers & Brannan, 2012). The softness of the coated samples may be due to their juiciness and mostly high moisture content (Izadi et al., 2015) and formation of softer crust in fried samples due to the edible coating. Also, in concert with this finding, lowfat sausage samples were reported by Carballo, Fernandez, Barreto, Solas, and Colmenero (1996) to be less hard and chewy than high-fat sausages. Differing fat contents in the fried meat products have been postulated to affect the tenderness of meat products. The tenderness of the coated samples might be due to lower cooking loss. Lower cooking loss has been established to influence the tenderness of fried meat (Küçüközet & Uslu, 2018). Insert Fig. 2 3.6. pH The pH values of deep-fat fried coated sample were unaffected by the edible coating prepared from chicken protein. The pH values of all edible coated treatments and controls ranged from 6.57-6.69 and 6.54-6.92, respectively. The use of edible coating did not alter the pH of the fried samples. Insert Fig. 3
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3.7. Frying Yield The dimensions of shrinkage and weight loss through the release of water are the main sources of consumer dissatisfaction (Young, Lyon, Searcy, & Wilson, 1987). Frying yield is inversely proportional to cooking loss. Cooking loss occurs when moisture is lost during the frying process. An average of approximately 82% frying yield was found in edible coated samples, which was higher than the control (Fig. 3). That is, the control experienced more cooking loss than the coated samples, averagely. It is understood by this result that, the use of edible coating in deep-fat foods prevents material loss. The highest number of frying yield was found in deep-fat fried drumsticks coated with 10% edible coating. The relatively lower cooking loss seen in edible coated fried chicken drumsticks could be attributed to the water retention ability of the coating (Karimi & Kenari, 2016), because of the formation of films by the proteins in the edible coatings. Also, these films formed by the edible coating acted as a guard to reduce loss of mass during frying. Insert Fig. 4 3.8. Sensory properties The scores received by all treatments in attributes are shown in Figure 5. Deep-fat fried chicken are patronized because of their desirable color, texture, odor, taste, etc. Therefore, the use of coating should not alter these desirable characteristics. All edible coated samples were scored between 5 and 8.33 (the highest score). There was no statistical difference (P > 0.05) between the control and edible coated samples on all attributes in sensory evaluation. The use of edible coating did not produce significant changes in the coated deep-fat fried samples. However, fried samples coated edible coating containing 15% CP received the highest score for appearance, 10% CP samples also received the highest score for color, when compared with controls.
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Insert Fig. 5 4.
Conclusions The use of edible coating prepared from chicken proteins reduced fat-uptake in deep-fat
fried chicken drumsticks. Samples coated with 15% w/w proteins had the lowest fat-uptake, more than 60% less fat than the control samples. 5% CP and 10% CP samples also resulted in 35 and 50% fat-uptake reductions compared to control samples, respectively. Further, the application of the edible coating on deep-fat fried foods has no deleterious effect on the pH, color, and textural properties of the product. This study shows that utilization of previously discarded raw materials and processing by-products may reduce pressure on food resources as well as diminish the waste and negative environmental impact associated with processing of meat products. There is also a potential to manufacture human food products from raw materials not previously perceived as fit for human consumption (e.g., Trimmings, skins-and-meat left on bone from chicken drumsticks, etc.). Thus, development of low-fat fried food using this approach may represent a more responsible use of natural resources and provides a novel and value-added consumer food product. At the same time, the development of deep-fried chicken samples that contain reduced calories from fat would allow consumers to enjoy the taste and texture that is characteristic of fried food. Acknowledgements This work was funded through the National Institute for Food and Agriculture of the United States Department of Agricultural, Project No. NC.X-311-5-18-170-1, in the Agricultural Research Program, North Carolina Agricultural and Technical State University.
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Technology, 46(1), 148-155. Tongnuanchan, P., Benjakul, S., Prodpran, T., & Songtipya, P. (2011). Characteristics of film based on protein isolate from red tilapia muscle with negligible yellow discoloration. International Journal of Biological Macromolecules, 48(5), 758–767. doi:10.1016/j.ijbiomac.2011.02.017 USDA, National Agricultural Statistics Service. Poultry Slaughter 2018 Summary. Access retrieved on April 2019. https://usda.library.cornell.edu/concern/publications/pg15bd88s Young, L. L., Lyon, C. E., Searcy, G. K., & Wilson, R. L. (1987). Influence of sodium tripolyphosphate and sodium chloride on moisture-retention and textural characteristics of chicken breast meat patties. Journal of Food Science, 52(3), 571–574. doi:10.1111/j.13652621.1987.tb06677.x Zhao, D., & Lin, Y. (2007). Innovations in the development and application of edible coatings for fresh and minimally processed fruits and vegetables: a review. Comp Rev Food Sci Food Saf, 6, 60–75. Zhao, X., Xing, T., Chen, X., Han, M. -y., Li, X., Xu, X. -l., & Zhou, G. -h. (2017). Precipitation and ultimate pH effect on chemical and gelation properties of protein prepared by isoelectric solubilization/precipitation process from pale, soft, exudative (PSE)-like chicken breast meat1. Poultry Science, 96(5), 1504–1512. doi:10.3382/ps/pew412
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Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
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Homogenization Trimmings, skin, meat-left-on-bone of chicken drumstick: water = 1: 6 (w: v) Isoelectric solubilization at pH 11.5 for 10 min Laboratory batch centrifugation 5,000 x g for 20 min at 4C Top layer chicken fat
Middle layer chicken muscle protein solution
Bottom layer insolubles (bones, skin, insoluble proteins, membrane lipids, etc.)
Isoelectric precipitation at pH 5.5 for 10 min Laboratory batch centrifugation 5,000 x g for 20 min at 4C Precipitate – chicken protein
Supernatant – process water
Edible coating preparation
5% w/w protein
10% w/w protein
15% w/w protein
Figure 1. A process flow diagram of isoelectric solubilization/precipitation method for recovering protein from chicken processing by-products and subsequent formulation of edible coating at different protein concentrations.
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6 a
Hardness (N)
5 4 ba 3
b
b
5% CP
10% CP
2 1 0 Control- No coating
15% CP
Treatments
Figure 2. Maximum peak puncture forces of deep-fat fried chicken drumsticks Data are given as mean values ± standard deviation. Different letters on the top of data bars indicate significant differences (Tukey’s Test, p<0.05) between mean values.
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7
a
a
a
a
Control- No coating
5% CP
10% CP
15% CP
6
pH
5 4 3 2 1 0
Treatments
Figure 3. Changes in pH values of deep-fat fried chicken drumsticks Data are given as mean values ± standard deviation. Different letters on the top of data bars indicate significant differences (Tukey’s Test, p<0.05) between mean values.
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86 a
ba
Frying yield (%)
84 ba 82 b 80 78 76 Control- No coating
5% CP CSB
10% CP CSB
15% CP CSB
Treatments
Figure 4. Frying yield of deep-fat fried chicken drumsticks Data are given as mean values ± standard deviation. Different letters on the top of data bars indicate significant differences (Tukey’s Test, p<0.05) between mean values.
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9
a
a a
a
8
Sensory score
7
a
a
a
a
a
a
a
a
a
a
a
6 5 4 3 2 1 Appearance
Texture
Odor
Attribute Control- No coating
5% CP
10% CP
15% CP
Figure 5. Sensory evaluation scores of attributes of deep-fat fried chicken drumsticks Data are given as mean values ± standard deviation. Different letters on the top of data bars indicate significant differences (Tukey’s Test, p<0.05) between mean values.
Color
a
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Chicken processing by-products can be used as a protein based edible coating. Edible coating with 15% protein reduced 60% fat-uptake reduction. Application of edible coating had no adverse effect on fried chicken quality.
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Table 1. Proximate Composition of Deep-Fat Fried Chicken Drumsticks
Experimental Treatments %
Control- No coating
5% CP
10% CP
15% CP
Fatuptake
4.73±0.46a
2.86±0.67ba
1.96±1.15b
1.77±1.34b
Fat content
14.12±00a
12.38±0.42ba
11.38±0.46b
10.54±1.54b
Moisture content
49.17±1.04b
51.67±1.53ba
50.67±0.58a
57.00±3.00ba
Ash
1.34±0.50a
1.39±0.54a
2.12±0.63a
2.14±0.76a
Data are given as mean values ± standard deviation. Different letters within the same row indicate significant differences (Tukey’s Test, p<0.05) between mean values.
Table 2. Color Changes of Deep-Fat Fried Chicken Drumsticks Experimental Treatments Control- No coating
5% CP
10% CP
15% CP
L*
45.20±1.47a
44.86±1.13a
47.09 ± 3.12a
45.60 ± 3.43a
a*
9.07±0.74a
8.46±0.56a
8.31±0.51a
8.06±1.26a
b*
10.30±1.68a
9.74±2.16a
12.03±3.36a
9.05±3.80a
Data are given as mean values ± standard deviation. Different letters within the same row indicate significant differences (Tukey’s Test, p<0.05) between mean values.
Daniel Ananey-Obiri, Lovie Matthews, Reza Tahergorabi PII:
S0268-005X(19)31460-2
DOI:
https://doi.org/10.1016/j.foodhyd.2019.105500
Reference:
FOOHYD 105500
To appear in:
Food Hydrocolloids
Received Date:
01 July 2019
Accepted Date:
06 November 2019
Please cite this article as: Daniel Ananey-Obiri, Lovie Matthews, Reza Tahergorabi, Chicken Processing By-Product: A Source of Protein for Fat Uptake Reduction in Deep-Fried Chicken, Food Hydrocolloids (2019), https://doi.org/10.1016/j.foodhyd.2019.105500
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. 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. © 2019 Published by Elsevier.
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Graphical abstract: Chicken Processing By-Product: A Source of Protein for Fat Uptake Reduction in Deep-Fried Chicken
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Chicken Processing By-Product: A Source of Protein for Fat Uptake Reduction in DeepFried Chicken
Daniel Ananey-Obiri, Lovie Matthews, and Reza Tahergorabi *
Food and Nutritional Sciences Program, North Carolina Agricultural and Technical State University, Greensboro, NC, USA
*All correspondence should be addressed to Dr. Reza Tahergorabi Tel: (336) 285-4865 E-mail address: [email protected]
Original manuscript Submitted to Food Hydrocolloids
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Abstract Chicken processing generates large quantities of by-products which can be used a source of protein for fat uptake reduction in fried chicken industry. This study investigated the use of edible coating prepared from chicken protein (CP) recovered using isoelectric precipitation/solubilization (ISP) from chicken drumstick processing by-products as a fat blocker in deep-fat fried chicken drumsticks samples. The samples were coated with edible coating at three different CP concentrations 5, 10, or 15% w/w and subsequently dipped in batter and breaded prior to deep frying. Deep-fat fried samples without edible coating served as control. The samples were deep-fried at 177oC for 3-4 min. Proximate composition, pH, texture, frying yield and sensory properties of the samples were tested. Total fat content of deep-fried samples with 15% coating showed the lowest amount of absorbed fat, about 60% less than the control. No difference was found between the color, pH and sensory properties of the coated and uncoated samples. However, uncoated samples were harder than coated samples. Also, samples coated with coating had higher moisture content and frying yield after frying, compared to uncoated samples. The development of low-fat fried foods using this approach would allow consumers to enjoy the taste and texture that is characteristic of fried food. At the same time, the food industry can reduce the environmental issues due to disposal of chicken processing by-products. The use of chicken proteins as an edible coating on fried chicken is novel and product friendly.
Keywords: chicken processing by-products; edible coating; deep-frying; low-fat food
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1. Introduction In the US, poultry processors transform 8.6 billion chicken to chicken products, annually (USDA, 2018). When chicken is mechanically processed for different products, large quantities of by-products are generated. Chicken processing by-products includes trimmings, meat-left-on bones, and skins which are discarded or used as low-value restructured food products. Meat industries are laden with the cost of disposing processing by-products; not to talk about the environmental concerns these by-products pose to the environment (Tahergorabi, Sivanandan & Jaczynski, 2011). Fried chicken industry is one of the sectors in food industry which uses large amount of processed chicken. As a result, it contributes to chicken processing by-products generation and subsequent consequences. Fried foods are very popular in the US and around the world due to their irresistible taste, desirable color, and crispy texture that are developed because of this method of cooking. However, the process of frying increases the total fat content of fried foods, consequently increasing the energy density of the foods (Echarte, Zulet, & Astiasaran, 2001; Sanchez-Muniz, 2006). Several findings have associated the consumption of fried foods with the development of cardiovascular diseases, obesity, and type-2 diabetes (Soriguer et al., 2003; Cahill et al., 2014). Estimated health care costs due to obesity, and related complications and comorbidities in the United States range from $147 billion to nearly $210 billion per year (Cawley, & Meyerhoefer, 2012). In addition, job absenteeism due to obesity costing approximately $4.3 billion annually (Cawley, Rizzo, & Haas, 2007) and with lower productivity while at work, costing employers $506 per obese worker per year (Gates, Succop, Brehm, Gillespie, & Sommers, 2008). Thus, due to consumers’ demand for healthier products,
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development of meat products with reduced fat content has been triggered (Das, Pawar, & Modi, 2013). According to Mellema (2003), the application of coating is a propitious route for decreasing fat-uptake since the surface properties of foods majorly contribute to fat-uptake. The use of hydrocolloids as edible coatings has been extensively explored (Izadi, Ojagh, Rahmanifarah, Shabanpour, & Sakhale, 2015). Polysaccharides such as cellulose, starch, gums have widely been explored as edible coating in deep-fat fried foods. Conversely, they have demonstrated poor barrier to moisture, thus, reducing juiciness and allowing for fat-uptake in deep fried foods. Lipid-based edible coatings have also demonstrated damaging effect on the appearance and gloss of the coated food (Hassan, Chatha, Hussain, Zia, & Akhtar, 2018). Proteins from both plant and animal sources have been used as edible coating for reducing fat content in deep-fat fried foods. Comparatively, protein-based edible coatings have been documented to reduce fat uptake in deep fat fried foods more than other hydrocolloids. Angor (2016) reported soy protein isolate (SPI) at four different concentrations (2, 6, 10 and 14%) to reduce fat-uptake more than carboxymethyl cellulose (MC) at equivalent concentrations in deep fried potato pellet chips. In another study, the use of SPI and whey protein isolate in edible coating reduced fat-uptake in deep fried cereal product to about 80 and 86%, respectively; whereas methyl cellulose (MC) resulted in 58% reduction in fat-uptake (Albert & Mittal, 2002). In addition, edible films and coatings made from proteins are the preferred among all the other biopolymers, due to their nutritional worth (Feng, Wu, Liu, Li, jiang et al., 2018). Yet, issues related to the allergenicity of some proteins such as soy, whey, egg albumen, and wheat have restricted their broad use (Zhao & Lin, 2007). Unlike the other proteins, there is paucity of
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literature on the use of proteins from animal source as edible coating. He, Franco, and Zhang, (2015) investigated fish protein hydrolysate (FPH) as an edible coating in deep-fat fried foods. Fish cakes coated with these proteins had significant fat reduction from 11% to about 1%. Grievous concerned with foods developed from FPH ingredients is off flavor and bitter taste associated with these foods (Kristinsson & Rasco, 2000; Dauksas, Slizyte, Rustad, & Storro, 2004). Stromal and myofibrillar proteins found in meat food proteins are used for making edible films and coatings (Tahergorabi, Hosseini, & Jaczynski, 2011). The film-forming and thermal gelation properties of proteins make them good materials for reducing fat absorption in deepfrying (Brannan, Mah, Schott, Yuan, Casher, Myers, Herrick, 2014). Films made from proteins can form bonds at different positions and offer high potential for forming numerous linkages. Myofibrillar proteins are able to form continuous matrix during drying due to their fully stretched and closely related structures arranged in parallel (do A. Sobral, dos Santos, & García,2005). Myosin a type of myofibrillar protein can also form a 3-dimensional network structure that prevents water escape when gels (Nakano, Ishioroshi, Samejima, & Yasui, 1979). In addition, animal products such as chicken provide almost three-fourths of the essential amino acids in food supply and contribute about 67% of the total protein, indicating a greater concentration of these vital nutrients such as vitamin B12, B6, riboflavin, niacin, phosphorus, and calcium (Link-swiler, 1982). No literature has exploited the use of chicken muscle protein as an edible coating for reducing fat-uptake in deep-fat fried foods. The objective of this study was to evaluate the potential of protein isolated from chicken processing by-products as an edible coating in reducing fat-uptake in deep-fat fried chicken drumsticks.
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2. Materials and Methods 2.1.
Chicken Collection and Preparation Fresh drumstick (skin-on bone-in) was purchased from a local grocery and they were cut
into pieces of 10 ± 1 g. The strips were kept in a refrigerator at 4oC immediately after the cutting process. 2.2.
Brine Washing of Minced Chicken Trimmings, skins-and-meat left on bone from chicken drumsticks, collectively
considered as by-products were ground uniformly using a meat grinder (LEM grinder, 5 Big Bite Grinder-0.35 HP, West Chester, OH, USA) with a hole diameter of 0.5 cm, and washed according to the method described by Tongnuanchan et. al, (2011), with slight modifications. The ground chicken drumstick was homogenized with 0.05M cold NaCl (2–4 °C) at a speed of 13,000 rpm for 2 min at 1:5 ratio (ground chicken drumstick – NaCl w: v) using a laboratory homogenizer (Homogenizer, OMNI International, Kenneswa, GA, USA) at a speed of 13,000 for 2 min. This was followed by centrifuging at 5000 x g for 20 min at 4oC, using a refrigerated centrifuge (Thermo Scientific, Model ST 16 Centrifuge Series, Asheville, NC, USA). The washing process was repeated twice. 2.3.
Protein Isolation Protein was isolated from the washed ground chicken according to the method described
by Tahergorabi et al., (2011b) (Fig. 1). Washed chicken meat was homogenized with deionized cold water (dd H2O) at 1:6 ratio (washed meat: water, w: v) using a laboratory homogenizer (Homogenizer, OMNI International, Kenneswa, GA, USA) set at speed five for 5 min. Ice cubes were used to control the temperature of the mixture at approximately 4 °C. Homogenization process was controlled at speed three in successive pH adjustment.
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A fraction of the homogenate, about 6 L was transferred into a beaker and the pH adjusted with 10 N NaOH to 11.50 ± 0.05 and held for 10 mins. The solution was centrifuged for 20 min at 5,000 x g and 4oC (Thermo Scientific, Model ST 16 Centrifuge Series, Asheville NC, USA). This resulted in three distinct layers; comprising of a top layer of oil, middle layer of chicken muscle protein solution, and a bottom layer of insoluble membranes, etc. The middle layer containing the chicken protein muscle was collected into a beaker and pH adjusted with 6 N HCl to 5.5 ± 0.05 to isoelectrically precipitate the protein. The solution was allowed to react for about 8-10 minutes. The solution was centrifuged for 20 min at 5,000 x g and 4oC (Thermo Scientific, Model ST 16 Centrifuge Series, Asheville NC, USA). This resulted in two layers: a top layerspent water, bottom layer-de-watered chicken protein. The dewatered protein was collected and referred to as chicken protein isolate (CPI). This protein was used in the preparation of the edible coating. Insert Fig. 1
2.4.
Quantitation of Protein in Isolate
The protein content of the CPI was determined using the Bradford protein assay (Bradford, 1976), with some modifications. This assay works on the principle of color change from brown to blue as the dye Coomassie Blue G250 binds to protein. Set of standards were prepared from Bovine serum albumin by dissolving it in a solution containing 0.1M NaOH and 3.5% NaCl. Also, 0.5 g of the CPI recovered with ISP was homogenized with 30 ml of 0.1M NaOH and 3.5% sodium chloride using a laboratory homogenizer (Homogenizer, OMNI International, Kennesaw, GA, USA). The resulting homogenate was centrifuged at 4000 x g at 4oC for 30 minutes, and the supernatant was collected and used for protein analysis. 20 µl of both the
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standards and the samples were plated into individual wells of a microplate in triplicates. 200µl of the Bradford reagent was added into wells containing the standards and samples. The plates were incubated at 37oC for 20 minutes and the absorbance read at 595 nm using a spectrophotometer 2.5.
Edible Coating Preparation Chicken protein isolate was formulated with water to form edible coating concentrations:
5, 10 and 15% (w/w) protein. Glycerol was also added as plasticizer at 0.4% (w/w) of the protein. The pH of the mixture was adjusted with 10 N NaOH to 11± 0.05 to solubilize the proteins. It was afterwards homogenized at 13,000 rpm for 1 min using a laboratory homogenizer (Homogenizer, OMNI International, Kenneswa, GA, USA). The pH was finally re-adjusted using 6 N HCl to approximately 7± 0.05. The edible coatings were kept refrigerated (4oC) for up to 12 hours before use. 2.6.
Preparation of Batter Batter formulation was based on Sahin, Sumnu, and Altunakar (2005), with slight
modification. It was formulated as follows; 48.7% (w/w) wheat flour (King Arthur Flour Company, Vermont, USA), 48.75% cornstarch (ACH Food Companies, Memphis, USA), 1.0% of (HPMC) (Methocel E15 Premium LV Hydroxypropyl Methylcellulose, Midland, USA), 1.0% salt (Morton, Chicago, USA), 0.5% baking powder (Rumford, Terre Haute, USA), and deionized water. The mixture was stirred, and standardization test conducted thereafter. The standardization of the batter was based on its viscosity, using a modified Stein Cup. A 4 inchdiameter funnel was used in place of the Stein Cup. The funnel was filled to the brim with the batter, and the viscosity of the batter was considered standard when all the batter drains through the hole in 11 seconds.
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2.7.
Chicken Samples Preparation for Frying The mass of each chicken strip was determined before and after the application of the
coating. Using a hand-held prong, chicken pieces were dipped in edible coating containing either 5%, 10%, or 15 % w/w protein after predusting, if coating was required. The samples were gently shaken to get rid of excess coating. They were accordingly dipped either in a batter. Lastly, the samples were gently rolled in breadcrumbs to allow for evenly breading. The weight of the breaded chicken samples was recorded before and after frying. 2.8.
Frying Process Chicken samples were fried at 177.7oC for 3-4 min in a deep fryer (Presto® Dual
ProFryTM/1800W, National Presto Industries Inc., WI., U.S.). Intermittently, the frying temperature was checked using data logging thermometer. Prongs were used to remove the fried chicken strips from the oil after the stipulated time. The samples were allowed to drip for few seconds. The fried chicken pieces were kept on white paper tissue and allowed to cool at ambient temperature with natural air. Analysis of the samples proceeded immediately after this process. 2.9.
Fat Analysis The lipid content was determined quantitatively by Soxhlet extraction method
(AOAC, 2010). About 3-4 g of the sample was measured into a disposable aluminum dish. The sample was dried in an oven for 1 ½ h at 125oC. The sample was cooled and transferred into an extraction thimble. The weight of an extraction flask was determined, and about 85mL of petroleum ether was then added to the flask. Extraction process was done for a minimum of 80 cycles in about 6 h. After the extraction process, the flask was heated over a water bath at 4262oC for few minutes. The flask was dried in an oven at 100oC -102oC for few minutes and cooled to room temperature. Fat content was calculated using the equation below:
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Fat content (%) =
Fat uptake (%) =
2.10.
Weight of flask and extracted fat (g) ― Weight of empty flask (g) × 100 weight of sample prior to extraction (g)
Fat content of sample after frying (g) ― Fat content of sample before frying(g) × 100 Fat content of sample prior to frying(g)
Moisture Analysis
Average moisture content of fried chicken strips was analyzed according to AOAC (2000). The samples were ground separately into fine particles in a laboratory grinder (LEM grinder, 5 Big Bite Grinder-0.35 HP, West Chester, OH, USA). About 1-3 g of the ground sample was transferred into an empty pre-weighed dish in a vacuum oven (Precision Scientific vacuum oven, model 19, Chicago, Il, USA). The samples were evenly spread with a spatula in the dish. Samples were left to dry at 105oC for 3 h. After this, the samples were cooled and weighed. The moisture content (MC) of each sample was calculated using the equation below: MC (%) =
2.11.
Weight of sample before drying (g) ― weight of sample after drying × 100 weight of sample before drying
Ash Content
The ash content of the fried samples was determined as follows. The weights of empty crucibles were taken and recorded (W1). In each crucible, 2 g of samples were added, and the total weight was recorded (W2). The crucible with the content were furnace (Thermo Fisher, Lindberg/ Blue M Moldatherm Box Furnace, Waltham, MA, USA) and heated at 550oC for 24 h in a furnace. The crucibles were removed, cooled to room temperature, and the weight of the crucible containing the ash was recorded (W1). The ash content was calculated as follows; Ash (%) =
(𝑊3 ― 𝑊1) (𝑊2 ― 𝑊1)
× 100%2.12. Frying yield
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The frying yield was determined by measuring the weight of the sample before and after frying, and it was calculated as follows: Frying yield (%) =
2.13.
weight of sample after frying (g) × 100% weight of sample before frying (g)
Color Determination
In each case, a piece of plastic wrap was put on the samples 5 min after frying, and color was determined. The color properties of the sample were measured using Minolta Chroma Meter CR-400 colorimeter (Minolta Camera Co. Ltd., Japan). The tristimulus color values L* (Lightness), a* (red) and b* (yellow) values were generated by the colorimeter to describe the color characteristics of the fried samples. The color readings were repeated thrice for each chicken sample, the mean values were reported. The colorimeter was calibrated before used. 2.14.
pH Determination
The pH of the samples was determined according to Alakhrash, Anyanwu, & Tahergorabi, (2016), but with slight modifications. Chicken sample (5 g) was homogenized (Homogenizer, OMNI International, Kenneswa, GA, USA) with 20ml of dd H2O at 13,000 for 1 min. A calibrated hand-held pH meter (OMNI International, Kenneswa, GA, USA) was used to measure the pH after it was calibrated. 2.15.
Texture analysis
The textural property of each fried sample was analyzed by puncture test using texture analyzer (Model TA-XT2, Texture Analyzer, Texture Technologies Corp., Scarsdale, NY, USA). The puncture test was done at 5 mm/s using a 1/8 spindle, with 15% penetrating thickness penetration of the crust. The height of the peak is measured as the hardness of the peak.
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2.16.
Sensory Evaluation
Sensory evaluation of fried chicken samples was conducted after approval was sought from institutional review board (IRB). Untrained panelists were recruited to evaluate the acceptability of the various treatments of fried chicken samples. Fresh fried chicken drumsticks were served to participants in a well-lit and ventilated room on coded white plates. They evaluated the samples based on their appearance, color, texture, and odor using 9 points hedonic scale. Participants ranked the fried products on a scale of 1 to 9 with 1= “dislike extremely and 9 = “Like extremely”. The responses on various attributes of the samples were analyzed statistically and mean values were reported. 2.17.
Statistical Analysis
The experiments were triplicated independently. The mean values were reported as results ± standard deviation (SD). Analysis of variance ANOVA (SAS, version 16.0, SAS 49 Institute Cary, North Carolina) was used to determine effects at a significance level of p<0.05. The mean differences among the treatments were compared using Tukey’s test. 3.
Results and Discussion
3.1. Fat-uptake Table 1 shows the fat-uptake of deep-fat fried chicken drumstick samples coated with different concentrations of CP and battered. The use of edible coating at the three different concentration levels reduced fat-uptake in the deep-fat fried samples. The fat-uptake reductions obtained in edible coated fried samples, except in 5% CP samples were significantly higher (P < 0.05) than the control samples. The edible coating at the three levels of protein concentration, 5% CP, 10% CP and 15% CP reduced fat-uptake to more than 35, 50 and 60%, compared to control
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samples, respectively. Evidently, as protein concentration increases in edible coating, fat absorption reduces in coated fried samples. The decrease in fat-uptake observed among samples coated with edible coating as opposed to control samples is due to the formation of complex network of films formed by the protein during frying. These networks are formed due the gelation of the myofibrillar proteins induced by heat. Chicken protein gelation comprises of several steps; starting from protein denaturation to irreversible aggregation of myosin head through the formation disulfide bond and helical-coil transition of the molecules’ tail, and a final step of forming a three-dimensional network (Lesiów & Xiong, 200; Ahhmed et al., 2009). One of the popular mechanisms that has been used to characterize fat-uptake during deep-frying is water replacement. During frying, the moisture in the food escape through pores and channels created in the food product. Subsequently, the voids and pores created due to the loss of moisture are filled with the oil (Ananey-Obiri, Matthews, Azahrani, Ibrahim, Galankis, Taherorabi, 2018). The complex network formed by the protein in the edible coating might have blocked the pores and cracks to prevent moisture escape and thus, subsequently preventing the oil absorption into the product during frying. The strength of the gel might have also been augmented by the use of ISP to recover the protein used in the edible coating, thus, reducing fat imbibition in the coated fried foods. Zhao et al (2017) demonstrated in their findings that proteins recovered using ISP produced strong gel. The fat-uptake reduction obtained in 10% CP samples was more than 50%. Compared to a previous study by Dragich and Krochta (2010) who obtained 30.68% fat-uptake reduction in wheat-flour-battered chicken strips coated with 10% whey protein denatured, the muscle protein produced a better result. Similarly, a study by Brannan and Pettit (2015)
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involving 10% whey protein as a postbreading dip reduced oil absorption by 37% in patties, which is almost equal to the reduction achieved with 5% CP samples in this study. The observed proportional reduction in fat content and fat-uptake among coated fried samples to protein concentration can be attributed to increasing aggregation and gelation of enough protein concentrations (Brannan et al., 2014). That is, the higher the protein concentration in the edible coating, the more complex network the molecules form to prevent fat from running into the food during frying. Mah and Brannan (2009) supported this assertion, by explaining that, the difference in the extent of the various concentrations as fat barriers is due the differences in protein molecules of the protein concentrations. The normal protein concentration for gelation to occur is 5 and 15% (Arntfield, Murray, & Ismond, 2007). 3.2. Moisture Moisture contents of coated and control deep fried samples are shown in Table 1. Moisture content is an important property of fried foods because it determines the characteristic qualities of the food. Edible coating containing 15% CP retained the highest amount of moisture in fried samples, but it was not significantly different (P > 0.05) from the other coated samples. Even though no significant difference in moisture content was observed among the various treatment, averagely, the highest moisture was retained in edible coated samples. That is, using edible coating retains moisture in deep-fat fried foods. Coating could form barriers that prevent moisture loss and subsequently reduce fat absorption (Singthong & Thongkaew, 2009). The network formed by the edible coating prevented the moisture from escaping, thus, retaining higher moisture content in coated samples than the uncoated sample (control). Although the moisture contents are not statistically different, they are numerically different. As seen in Table 1, the moisture content of the samples increased
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from 49% for control to 57% for samples coated with 15% edible coating. The complex network formed by the protein in the edible coating formed a film that covered the pores and channels created in the food during frying. This process reduces the incidence of moisture loss. The relatively lesser voids created in coated fried sample, unlike in the uncoated, reduced fat absorption during frying. 3.3. Ash Changes in ash content in coated and control samples as measured are displayed in Table 1. Though no significant changes (P > 0.05) in ash content was measured among the various treatments, the highest ash contents were obtained in coated deep-fat fried samples. Increasing protein concentration in the edible coating resultantly led to increasing ash content in deep fried coated samples. The use of edible coating increased the mineral content (calcium, phosphorus, sodium, potassium) and trace elements. The minerals increased with increasing protein concentration of the edible coating. Insert Table 1 3.4. Color The tristimulus color values of deep-fried chicken drumstick samples are shown in Table 2. No significant difference (P> 0.05) in L* values was observed among the various treatments. Interestingly, chicken samples coated with edible coating showed slight improvement (numerically) in L*, with 10% CP samples demonstrating higher L* values than control samples. Insert Table 2 3.5. Texture Meat product texture is an important quality determinant. Figure 2 displays the textural properties of coated and uncoated fried chicken samples. The texture of battered meat products is
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chiefly characterized by hardness, describing the qualities of the substrate, crunchiness, and the crust (Das et al., 2013). Puncture test is the recommended test for texture analysis of fried samples (Bourne, 2002). The puncture test revealed the hardness of the samples. Hardness is the defined as force that is needed to deform the sample at a certain distance (Brannan, 2007). Chicken samples coated with edible coating were commonly less hard than the controls. Similar to a study by Rayner, Ciolfi, Maves, Stedman, and Mittal (2000), deep-fried samples coated with 10% soy protein were softer than uncoated fried samples. Generally, edible coated fried samples had higher moisture content than the controls. Consumers’ favor soft and juicy interior battered and breaded deep-fat fried foods (Myers & Brannan, 2012). The softness of the coated samples may be due to their juiciness and mostly high moisture content (Izadi et al., 2015) and formation of softer crust in fried samples due to the edible coating. Also, in concert with this finding, lowfat sausage samples were reported by Carballo, Fernandez, Barreto, Solas, and Colmenero (1996) to be less hard and chewy than high-fat sausages. Differing fat contents in the fried meat products have been postulated to affect the tenderness of meat products. The tenderness of the coated samples might be due to lower cooking loss. Lower cooking loss has been established to influence the tenderness of fried meat (Küçüközet & Uslu, 2018). Insert Fig. 2 3.6. pH The pH values of deep-fat fried coated sample were unaffected by the edible coating prepared from chicken protein. The pH values of all edible coated treatments and controls ranged from 6.57-6.69 and 6.54-6.92, respectively. The use of edible coating did not alter the pH of the fried samples. Insert Fig. 3
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3.7. Frying Yield The dimensions of shrinkage and weight loss through the release of water are the main sources of consumer dissatisfaction (Young, Lyon, Searcy, & Wilson, 1987). Frying yield is inversely proportional to cooking loss. Cooking loss occurs when moisture is lost during the frying process. An average of approximately 82% frying yield was found in edible coated samples, which was higher than the control (Fig. 3). That is, the control experienced more cooking loss than the coated samples, averagely. It is understood by this result that, the use of edible coating in deep-fat foods prevents material loss. The highest number of frying yield was found in deep-fat fried drumsticks coated with 10% edible coating. The relatively lower cooking loss seen in edible coated fried chicken drumsticks could be attributed to the water retention ability of the coating (Karimi & Kenari, 2016), because of the formation of films by the proteins in the edible coatings. Also, these films formed by the edible coating acted as a guard to reduce loss of mass during frying. Insert Fig. 4 3.8. Sensory properties The scores received by all treatments in attributes are shown in Figure 5. Deep-fat fried chicken are patronized because of their desirable color, texture, odor, taste, etc. Therefore, the use of coating should not alter these desirable characteristics. All edible coated samples were scored between 5 and 8.33 (the highest score). There was no statistical difference (P > 0.05) between the control and edible coated samples on all attributes in sensory evaluation. The use of edible coating did not produce significant changes in the coated deep-fat fried samples. However, fried samples coated edible coating containing 15% CP received the highest score for appearance, 10% CP samples also received the highest score for color, when compared with controls.
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Insert Fig. 5 4.
Conclusions The use of edible coating prepared from chicken proteins reduced fat-uptake in deep-fat
fried chicken drumsticks. Samples coated with 15% w/w proteins had the lowest fat-uptake, more than 60% less fat than the control samples. 5% CP and 10% CP samples also resulted in 35 and 50% fat-uptake reductions compared to control samples, respectively. Further, the application of the edible coating on deep-fat fried foods has no deleterious effect on the pH, color, and textural properties of the product. This study shows that utilization of previously discarded raw materials and processing by-products may reduce pressure on food resources as well as diminish the waste and negative environmental impact associated with processing of meat products. There is also a potential to manufacture human food products from raw materials not previously perceived as fit for human consumption (e.g., Trimmings, skins-and-meat left on bone from chicken drumsticks, etc.). Thus, development of low-fat fried food using this approach may represent a more responsible use of natural resources and provides a novel and value-added consumer food product. At the same time, the development of deep-fried chicken samples that contain reduced calories from fat would allow consumers to enjoy the taste and texture that is characteristic of fried food. Acknowledgements This work was funded through the National Institute for Food and Agriculture of the United States Department of Agricultural, Project No. NC.X-311-5-18-170-1, in the Agricultural Research Program, North Carolina Agricultural and Technical State University.
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Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
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Homogenization Trimmings, skin, meat-left-on-bone of chicken drumstick: water = 1: 6 (w: v) Isoelectric solubilization at pH 11.5 for 10 min Laboratory batch centrifugation 5,000 x g for 20 min at 4C Top layer chicken fat
Middle layer chicken muscle protein solution
Bottom layer insolubles (bones, skin, insoluble proteins, membrane lipids, etc.)
Isoelectric precipitation at pH 5.5 for 10 min Laboratory batch centrifugation 5,000 x g for 20 min at 4C Precipitate – chicken protein
Supernatant – process water
Edible coating preparation
5% w/w protein
10% w/w protein
15% w/w protein
Figure 1. A process flow diagram of isoelectric solubilization/precipitation method for recovering protein from chicken processing by-products and subsequent formulation of edible coating at different protein concentrations.
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6 a
Hardness (N)
5 4 ba 3
b
b
5% CP
10% CP
2 1 0 Control- No coating
15% CP
Treatments
Figure 2. Maximum peak puncture forces of deep-fat fried chicken drumsticks Data are given as mean values ± standard deviation. Different letters on the top of data bars indicate significant differences (Tukey’s Test, p<0.05) between mean values.
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7
a
a
a
a
Control- No coating
5% CP
10% CP
15% CP
6
pH
5 4 3 2 1 0
Treatments
Figure 3. Changes in pH values of deep-fat fried chicken drumsticks Data are given as mean values ± standard deviation. Different letters on the top of data bars indicate significant differences (Tukey’s Test, p<0.05) between mean values.
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86 a
ba
Frying yield (%)
84 ba 82 b 80 78 76 Control- No coating
5% CP CSB
10% CP CSB
15% CP CSB
Treatments
Figure 4. Frying yield of deep-fat fried chicken drumsticks Data are given as mean values ± standard deviation. Different letters on the top of data bars indicate significant differences (Tukey’s Test, p<0.05) between mean values.
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9
a
a a
a
8
Sensory score
7
a
a
a
a
a
a
a
a
a
a
a
6 5 4 3 2 1 Appearance
Texture
Odor
Attribute Control- No coating
5% CP
10% CP
15% CP
Figure 5. Sensory evaluation scores of attributes of deep-fat fried chicken drumsticks Data are given as mean values ± standard deviation. Different letters on the top of data bars indicate significant differences (Tukey’s Test, p<0.05) between mean values.
Color
a
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Chicken processing by-products can be used as a protein based edible coating. Edible coating with 15% protein reduced 60% fat-uptake reduction. Application of edible coating had no adverse effect on fried chicken quality.
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Table 1. Proximate Composition of Deep-Fat Fried Chicken Drumsticks
Experimental Treatments %
Control- No coating
5% CP
10% CP
15% CP
Fatuptake
4.73±0.46a
2.86±0.67ba
1.96±1.15b
1.77±1.34b
Fat content
14.12±00a
12.38±0.42ba
11.38±0.46b
10.54±1.54b
Moisture content
49.17±1.04b
51.67±1.53ba
50.67±0.58a
57.00±3.00ba
Ash
1.34±0.50a
1.39±0.54a
2.12±0.63a
2.14±0.76a
Data are given as mean values ± standard deviation. Different letters within the same row indicate significant differences (Tukey’s Test, p<0.05) between mean values.
Table 2. Color Changes of Deep-Fat Fried Chicken Drumsticks Experimental Treatments Control- No coating
5% CP
10% CP
15% CP
L*
45.20±1.47a
44.86±1.13a
47.09 ± 3.12a
45.60 ± 3.43a
a*
9.07±0.74a
8.46±0.56a
8.31±0.51a
8.06±1.26a
b*
10.30±1.68a
9.74±2.16a
12.03±3.36a
9.05±3.80a
Data are given as mean values ± standard deviation. Different letters within the same row indicate significant differences (Tukey’s Test, p<0.05) between mean values.