Vitamins profile as an indicator of the quality of frozen Agaricus bisporus mushrooms

Accepted Manuscript Title: Vitamins profile as an indicator of the quality of frozen Agaricus bisporus mushrooms Author: Emilia Berna´s Gra˙zyna Jaworska PII: DOI: Reference:

S0889-1575(16)30021-7 http://dx.doi.org/doi:10.1016/j.jfca.2016.03.002 YJFCA 2696

To appear in: Received date: Revised date: Accepted date:

17-12-2015 8-2-2016 2-3-2016

Please cite this article as: Berna´s, Emilia., & Jaworska, Gra˙zyna., Vitamins profile as an indicator of the quality of frozen Agaricus bisporus mushrooms.Journal of Food Composition and Analysis http://dx.doi.org/10.1016/j.jfca.2016.03.002 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.

Vitamins profile as an indicator of the quality of frozen Agaricus bisporus mushrooms Emilia Bernaśa,*, Grażyna Jaworskab a

Department of Fruit, Vegetable and Mushroom Processing, University of Agriculture in

Krakow, 122 Balicka Street, 30-149 Krakow, Poland b

Department of Plant Food Technology and Crop Quality, University of Rzeszow, 1

Ćwiklińskiej Street, 35-601 Rzeszow, Poland

*Corresponding author. Tel./fax +48126624757. E-mail address: [email protected] (E. Bernaś).

Highlights  In mushrooms niacin was the most abundant vitamin, followed by riboflavin.  Pre-treatment and period of storage had the greatest effect on vitamins profile.  The greatest changes occurred between months 6 and 12 of storage.  The greatest losses were found in vitamin B1, L-ascorbic acid and α-tocopherol.  Freezing method affected only vitamin B3, higher levels were found in cryogenically frozen products.

ABSTRACT Fresh mushrooms have been known as a functional food, especially as a good source of vitamins from B-group. The work determined the effect of pre-treatment (blanching, vacuum soaking), method of freezing (air-blast and cryogenic), temperature (‒20 ºC, ‒30 ºC) and period (0, 6, 12 months) of frozen storage on the vitamins profile in white A. bisporus. Niacin and riboflavin were the most abundant vitamins in all mushroom products (154‒362 mg; 1.57‒5.06 mg/100 g dm, respectively). The greatest influence on the vitamins profile was pretreatment. The highest levels of vitamin B3 and L-ascorbic acid were found in blanched mushrooms, vitamin B6 in vacuum soaked, α-tocopherol and vitamin B1 in unblanched. The greatest losses occurred between the 6th and 12th month of storage, and therefore mushrooms should not be stored for longer than 6 months. After storage the greatest losses were found in vitamin B1, L-ascorbic acid and α-tocopherol. A. bisporus mushrooms contain small amounts of L-ascorbic acid and α-tocopherol, therefore the level of vitamin B1 may be regarded as a quality indicator. The freezing method affected only vitamin B3, with levels higher after

cryogenic than air-blast freezing. The storage temperature generally had no effect on vitamin levels.

Keywords: vitamins, HPLC, Agaricus bisporus, pre-treatment, freezing storage

1.

Introduction

Edible mushrooms are an underrated source of active biological constituents, particularly polysaccharides protein-sugar complexes, triterpenoids, phenols, vitamins and minerals (Cheung, 2010), and are rich in B and D vitamins (Furlani and Godoy, 2008; Phillips et al., 2010). The most abundant B vitamins in mushrooms are niacin and riboflavin. Niacin and riboflavin content are similar and are higher than that found in fresh chicken meat or fish (Kumar and Aalbersberg, 2006, Mattila et al., 2001), while amounts of vitamin D (ergocalciferol) in some species of wild mushrooms are similar to those found in oily fish (cholecalciferol) (Phillips et al., 2010). The most widely cultivated and consumed mushroom is the white-capped variety of Agaricus bisporus (button mushroom). Fresh Agaricus bisporus are extremely perishable and are therefore preserved to facilitate their marketability and deal with periods of oversupply. One of the best methods of preserving mushrooms with maximum nutrient retention is freezing. Pre-treatments are of crucial importance in freezing mushrooms (Bernaś and Jaworska, 2015; Coskuner and Ozdemir, 2000; Jaworska et al., 2008), particularly blanching, which is a basic requirement in mushroom preservation. Despite its benefits, blanching causes degradation of nutritional components, especially vitamins and minerals. Jaworska et al. (2008) showed that blanching, or impregnation and blanching mushrooms results in losses of water-soluble constituents, including vitamins B1 and B2. Rickman et al. (2007) found that, as in the case of mushrooms, blanching green peas and beans prior to freezing causes losses of thiamine and riboflavin. Apart from pre-treatments, mushroom quality can also be affected by the method of freezing and conditions of frozen storage. Blast freezing is the most widely used method, but in recent years there has been growing interest in cryogenic freezing. One indicator of food quality is nutritional value, including vitamin content. Vitamins are among the most labile of food components; therefore, changes in vitamin content may reflect the overall quality of a food. Vitamin levels in food products are affected by preliminary treatment, preservation and storage. All processes which involve the use of large amounts of water, such as blanching and boiling, can result in losses of water-soluble vitamins through 2

diffusion or leaching, with thiamine and L-ascorbic acid being the most susceptible (Gliszczyńska-Świgło et al., 2006; Nisha et al., 2004; Nisha et al. , 2005). The main causes of L-ascorbic acid loss are oxidation or leaching in an aqueous environment (Choe and Min, 2006). Oxidation occurs in neutral or alkaline environments and is catalysed by Cu or Fe ions, or by exposure to light. Vitamins A, E and B1 are also susceptible to oxidation, with vitamins A, B2 and B12 being the most sensitive to sunlight exposure. Bernhardt and Schlich (2006) showed that the type of raw material is a major factor determining the levels of lipophilic vitamins in boiled vegetables. The authors cited found that boiling fresh broccoli increased the availability of β-carotene and α-tocopherol, whereas boiling frozen broccoli had the opposite effect. Manzi et al. (2004) showed that thermal treatment and preservation had a beneficial effect on the assimilation of nutritional components in mushrooms. The aim of this work was to determine the effect of the freezing method and conditions of frozen storage on the profile of selected water- and fat-soluble vitamins in Agaricus bisporus mushrooms.

2.

Material and methods

2.1. Chemicals

All solventts were of HPLC analytical grade and were purchased from Chempur (Piekary Śląskie, Poland). Standards such as tocopherols, L-ascorbic acid and B-group vitamins were procured from Sigma Chemical Co. (St. Louis, MO). Triple distilled and HPLC purified water was employed for the entire study (Millipore Direct-Q 3UV; Millipore SAS, Molsheim, France).

2.2. Materials

The material examined consisted of fresh and frozen Agaricus bisporus (Lange) Sing. mushrooms subjected to various methods of pre-treatment prior to freezing. Frozen mushrooms were evaluated immediately after freezing and after 6 and 12 month of storage at ‒20 ºC and at ‒30 ºC. Fresh mushrooms were obtained from a grower in Radostowice, Poland. The mushrooms strain was: intermediate hybrid SP 251. Mushrooms were frozen two hours after harvest. Mushrooms were white in colour, with the veil connecting the pileus and stipe still intact and a cap diameter of 3‒5 cm. The freezing process comprised the following 3

stages: selection, preliminary treatment, freezing and frozen storage. The preliminary processing and freezing process were conducted under laboratory conditions, enabling the precise control of parameters at every stage of technological treatment. The quantities involved were consistent with a small-scale investigation, 20 kg of mushrooms being used to obtain each type of product examined. Preliminary treatment consisted of: cleaning and sorting; rinsing under running tap water; and slicing into approximately 7-mm strips. One part of the sliced mushrooms was frozen (product code: not blanched mushrooms), while the other part was subjected to two kinds of pre-treatment: 1. blanching in sodium metabisulfite (0.2 g/100 g) and citric acid (0.5 g/100 g) solution for 3 minutes at 96‒98 °C (product code: blanched mushrooms). 2. vacuum impregnation in sodium metabisulfite (0.2 g/100 g) and citric acid (0.5 g/100 g) solution for 15 minutes at room temperature (product code: vacuum impregnated mushrooms). Blanching was carried out in 10-litre stainless steel vessels, the proportion of mushrooms to blanching medium being 1:5 (w/w). After blanching the material was cooled in water and then drained on sieves. Vacuum impregnation was performed in a Heidolph (Schwabach, Germany) LABOROTA 4000 vacuum evaporator at room temperature (20‒22 ºC) for 15 min at a pressure of 0.025 MPa. Fresh mushrooms and mushrooms after blanching and vacuum impregnation were frozen in a single layer (thickness about 3 cm) by two methods: 1. air-blast, in a 3626-51 blast freezer (Feutron, Greiz, Germany) at ‒35 oC for 120 minutes in order to achieve a temperature of –20 ºC or ‒30 ºC at the thermal centre of the sample. 2. cryogenic in liquid nitrogen (boiling point = ‒196 ºC). Freezing was carried out in an open polystyrene vessel 3-cm thick, with a capacity of 20 L. After preliminary treatment, mushrooms were placed in metal sieves 170 mm in diameter (mesh size 8 mm) in layers of about 30 mm. The freezing process was as follows: preliminary cooling (suspended above liquid nitrogen): 240 s; actual freezing (impregnation in liquid nitrogen): 30 s; temperature equalisation (suspended above liquid nitrogen): 240 s. After freezing, mushrooms were placed in 0.5-L polyethylene containers. Products were stored for 6 and 12 months at –20 ºC and ‒30 ºC.

2.3. Methods

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Fresh Agaricus bisporus (sample code FR), and frozen products (directly after freezing and every six months during frozen storage) were subjected to analysis of the proximate chemical composition and levels of the selected water- and fat-soluble vitamins.

2.3.1 Proximate composition analysis

The proximate composition of fresh and frozen mushrooms was determined according to the AOAC (2005) method. The dry matter was estimated by drying at 105 ºC (930.04), the crude protein (N × 4.38) was estimated by the Kjeldahl method (978.04), the crude fat was determined by extracting a sample with diethyl ether in a Soxhlet apparatus (920.39) and the ash content was determined by incineration at 485 ºC (920.05). Total carbohydrates were calculated by difference, using the formula: total carbohydrates = (g dry weight) ‒ (g crude protein) ‒ (g crude fat) ‒ (g ash).

2.3.2. Vitamins analysis

Vitamin B1 (thiamine) and B2 (riboflavin) content was determined using HPLC (PN-EN 14122:2004/AC:2006; PN-EN 14152:2004/AC:2006). Thiamine and riboflavin were determined simultaneously using a Merck liquid chromatograph with fluorescence detector. Analysis was carried out on an Onyx Monolithic C18 column (100 × 4.6 mm) with Onyx Monolithic C18 Guard Cartridge (5 × 4.6 mm) (both Phenomenex, Torrance, USA), and was conducted at an excitation/ emission wavelength of 360/503 nm. Column temperature was 25 ºC. Water and acetonitrile were used as mobile phase in gradient elution (t = 0, w/ac = 88/12; t = 12 min, w/ac = 0/100) with a flow rate of 0.9 mL/min. Vitamin B3 (niacin) content was established according to the modified method described by Juraja et al. (2003), using a Merck liquid chromatograph with UV/Vis detector. Samples were subjected to alkaline hydrolysis by Ca(OH)2 at 121 °C for 2 h with sonification using a ultrasonic washer IS-14 (InterSonic, Olsztyn, Poland) 35kHz/20 ºC/15 min. The analysis was carried out on a LUNA C18 column (150 × 2.00 mm) with C18 Guard Cartridge AJO-4286 (4 × 2.00 mm) (both Phenomenex). Column temperature was 35 ºC. Niacin was determined at a wavelength of 220 nm. Isocratic elution with a flow rate of 0.1 mL/min. was performed using a solution of methanol and Pic-A reagent (tetrabutylammonium hydrogen sulfate) in water (1:99). The concentration of Pic-A was 0.005 M.

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Vitamin B6 content was determined using chromatography (EN 14164, 2008). The analysis was carried out on a Merck liquid chromatograph fitted with a fluorescence detector on a Phenosphere-Next C18 (150 × 4.60 mm) monolithic column with Onyx Monolithic C18 Guard Cartridge (5 × 4.6 mm) (both Phenomenex). Column temperature was 25 ºC. Isocratic elution with a flow rate of 0.9 mL/min. was performed using a solution of sulfuric acid (0.015 M) and trichloroacetic acid (TCA) of ≥99% purity (5 mM). Measurements were performed at excitation/emission wavelengths of 290/390 nm. L-Ascorbic acid content was determined using HPLC (EN 14130, 2003). Mushroom samples were diluted with 0.1 M metaphosphoric acid and centrifuged. The analysis was carried out on a Thermo Scientific Dionex Ultimate 3000 UPLC chromatograph with DAD detector. Samples were injected into an Onyx Monolithic C18 column (100 × 4.6 mm) with Onyx Monolithic C18 Guard Cartridge (5 × 4.6 mm) (both Phenomenex). Column temperature was 25 ºC. Elution was carried out using 0.1 M metaphosphoric acid at a flow rate of 1 mL/min. Measurements were performed at 254 nm. Tocopherols content was determined according to the modified method of Katsanidis and Addis (1999) using normal-phase HPLC. Tocopherols were extracted with hexane mixed with BHT. The analysis was carried out on a Merck liquid chromatograph with fluorescence detector. The sample was injected into a Luna NH2 column (250 × 4.6 mm) with Onyx Monolithic C18 Guard Cartridge (5 × 4.6 mm) (both Phenomenex). Column temperature was 30 ºC. Isocratic elution with a flow rate of 2.5 mL/min was carried out using a mixture of nhexane and 2-propanol (95:5). The wavelengths of excitation/emission were 290/330 nm. Vitamin E activity was calculated as α-tocopherol equivalents (α-TE) per 100 g of edible weight according to the equation: Vitamin E activity = 1 × α-tocopherol + 0.5 × β-tocopherol + 0.1 × γ-tocopherol + 0.03 × δ-tocopherol. β-Carotene and lycopene contents were analyzed by spectrophotometry using extracts prepared with acetone and hexane mixture (4:6) by sonification (Barros et al., 2008 a). Absorbance was measured at wavelengths 453, 505, 663 nm. The content of carotenoids (mg) in 100 mL of extract was calculated as follows: β-carotene = 0.216 × A663 – 0.304 × A505 + 0.452 × A453; lycopene = −0.0458 × A663 + 0.372 × A505 − 0.806 × A453.

2.4. Statistical analysis

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The results of the investigation were analyzed statistically using two-way analysis of variance (ANOVA) based on Duncan’s range test at p < 0.05. The Statistica 10.0 Pl (StatSoft) program was used for statistical calculations.

3.

Results and discussion

3.1. Proximate composition

Figure 1 shows the chemical composition of fresh and frozen mushrooms. Since the length of storage (0, 6 or 12 months) did not affect these values for frozen mushrooms, averages for all stages of storage are given for each type of pre-treatment. Fresh A. bisporus mushrooms with a dry weight of 7.59 g/100 g comprised: total carbohydrates (57.2%), crude protein (26.7%), ash (11.5%) and crude fat (4.6%). In comparison, Reis et al. (2012) determined substantially lower levels of crude protein, ash and crude fat, but higher total carbohydrate content in fresh A. bisporus with a slightly higher dry weight (8.73 g/100 g). Pre-treatment, freezing and frozen storage resulted in decreases in dry weight of 4‒39% and, in general, small changes in proximate chemical composition compared with the fresh product. Fernandes et al. (2014) found that freezing Macrolepiota procera (Scop.) Singer mushrooms resulted in decreases in dry weight (1%), total carbohydrates (10%) and fat (42%) and increases in protein (42%) and ash (3%). The type of pre-treatment applied to A. bisporus affected only dry weight and total carbohydrates. The highest dry weight was found in mushrooms blanched prior to freezing, and the lowest in vacuum soaked mushrooms. In the case of total carbohydrates, the opposite correlation was observed.

3.2.

Vitamins

The content of selected vitamins in fresh and frozen mushrooms is given in Figures 2 and 3, and in Tables 1 and 2. According to Bernaś et al. (2006) and Wang et al. (2014), edible mushrooms are a good source of vitamins, especially niacin, riboflavin and pyridoxine, with levels comparable to those found in vegetables. However, it should be emphasised that vitamin levels in mushrooms vary widely between species. For example, Caglarirmak (2007) noted that Lentinus edodes mushrooms contain more folic acid and less riboflavin than Pleurotus ostreatus or Pleurotus sajor-caju, while Mattila et al. (2001) found that Agaricus bisporus is a better source of thiamine than Lentinus edodes or Pleurotus ostreatus. 7

The most abundant B vitamin in fresh A. bisporus was niacin, followed by riboflavin, thiamine and vitamin B6 (Figs 2 and 3; Tables 1 and 2). All three forms of vitamin B6 were present, with pyridoxamine constituting 98.3%, pyridoxal 1.3% and pyridoxine 0.4%. Compared with the results of the present work, Furlani and Godoy (2008) determined onethird the level of thiamine and 30% less riboflavin in fresh A. bisporus. Mattila et al. (2001) also found less thiamine but virtally the same levels of riboflavin. Fresh mushrooms contained considerably more L-ascorbic acid than reported by Mattila et al. (2001), but only slightly more than found by Oms-Oliu et al. (2010). According to the literature (Barros et al., 2008a; Reis et al., 2012) levels of tocopherol in A. bisporus mushrooms range from 0.06 mg to 0.24 mg/100 g dry weight, appearing in all four forms (Reis et al. 2012) or only as α- and βtocopherol (Barros et al., 2008 a). According to Reis et al. (2012), the dominant form is δtocopherol, while according to Barros et al. (2008 b) it is β-tocopherol. A. bisporus mushrooms also contain 0.20 mg β-carotene and 0.09 mg lycopene. Compared with these data, the present authors found levels of tocopherol, β-carotene and lycopene which were, respectively, 3.17 mg, 2.85 mg and 1.70 mg higher. The only form of tocopherol found to be present was α-tocopherol, in considerably higher amounts than in the works cited above. These differences may have been due to using mushrooms of varying strain, size or maturity; Harada et al. (2004) found that growing conditions and strain had a significant effect on the chemical composition of Hypsizygus marmoreus mushrooms. Moreover, Reis et al. (2012) and Barros et al. (2008b) analysed mushrooms obtained from local supermarkets or from forests (wild mushrooms) and did not provide a detailed description of the mushrooms. Freezing resulted in significant decreases in the levels of all the vitamins analysed, with the exception of vitamin B3 (Table 1). Average losses ranged from 8 to 66%; the smallest changes affected β-carotene (15%) and lycopene (8%), while the greatest were in vitamin B1 (61%) and α-tocopherol (66%). Further losses were observed during frozen storage, these being generally greater between months 6 and 12 (7‒43%) than between months 0-6 (9‒32%). The individual vitamins undergoing the most significant changes compared with earlier stage of storage were vitamin B2, B6, β-carotene and lycopene, and, by the end of the storage period, vitamin B1. After 12 months of storage, losses of individual vitamins, compared with levels immediately after freezing, ranged from 16-58%. The greatest average changes were found in vitamins B1 (52%) and B2 (58%) and α-tocopherol (50%); moderate changes were noted in vitamins B3 (33%) and B6 (45%) and L-ascorbic acid (40%) while the smallest were in βcarotene (16%) and lycopene (18%). After one year of storage, thiamine content in frozen mushrooms was 4‒36% of that found in fresh mushrooms, riboflavin 27‒40%, niacin 8

26‒59%, pyridoxine 16‒61%, L-ascorbic acid 8‒24%, tocopherol 8‒24%, β-carotene 65‒80% and lycopene 68‒85%. (Figs 1 and 2). Only two forms of vitamin B6 were present in frozen mushrooms: pyridoxamine and pyridoxal, with pyridoxamine comprising 91‒98% of the total content. The increase in the proportion of pyridoxal in total vitamin B6 may well have been due to the transformation of one form of the vitamin into another. In comparison, Jaworska et al. (2008), and Bernaś and Jaworska (2015) reported much smaller losses of vitamins B1 and B2 (retaining 33‒62% and 58‒89% respectively of levels found in the raw material) in frozen A. bisporus after 8 months storage, having previously undergone various types of pretreatment. Only in the case of vitamin C were similar losses (64‒91%) found (Jaworska et al. 2008). In vegetables, on the other hand, vitamin loss resulting from freezing and frozen storage varies according to species. Czarnowska and Gujska (2012) found that losses of folate (5-methyltetrahydrofolate) in various vegetables after one year of frozen storage amounted to 90‒99% compared with the raw material; in cauliflower the greatest changes occurred in the first 3 months of storage, in peas, broccoli and spinach during the first 6 months, and in green and yellow beans after 9 months. According to Bernaś and Jaworska (2015), and Jaworska et al. (2008), pre-treatments prior to freezing have a very considerable effect on mushroom quality during long periods of frozen storage. Jaworska et al. (2008) maintain that impregnating A. bisporus before blanching has an adverse effect on levels of water-soluble constituents, such as thiamine and riboflavin. Therefore, a better alternative to traditional blanching in an aqueous environment may be microwave blanching. Bernaś and Jaworska (2015) showed that microwave blanching A. bisporus prior to freezing resulted in a frozen product containing 11‒20% more dry weight, ash and vitamins B1 and B2 than frozen mushrooms blanched in an aqueous environment prior to freezing. The results of the present work also indicate that pre-treatments have a considerable effect on vitamin levels, with significant differences between products found for levels of vitamin B1, B3, B6, L-ascorbic and α-tocopherol (Table 1). Levels of vitamin B3 and L-ascorbic acid were highest in blanched mushrooms, B6 in vacuum soaked mushrooms and vitamin B1 and α-tocopherol in unblanched mushrooms. Pre-treatments did not have a significant effect on the remaining vitamins analysed; nonetheless, the highest levels of βcarotene and lycopene were found in unblanched mushrooms, while vitamin B2 levels were highest after vacuum impregnation. When freezing mushrooms, attention should also be paid to the freezing method used, the most common being blast freezing at ‒35 °C (Bernaś and Jaworska, 2015; Czapski and Szudyga, 2000; Jaworska et al., 2008). However, good results can be obtained from cryogenic 9

freezing. According to Kondratowicz and Kowałko (2000), cryogenic freezing of mushrooms not only results in a higher quality product than blast freezing, particularly with regard to consistency and intensity of mushroom flavour and aroma, but also enables the period of frozen storage to be extended to 1 year. In contrast, Agnelli and Mascheroni (2002) noted that despite maintaining light colour in mushrooms, cryomechanical freezing caused losses of mushroom mass 33% greater than in the case of conventional air-blast freezing. In the present work, the freezing method was not a major factor in vitamin content; only in the case of vitamin B3 was there a significant difference between the products, levels being on average 29% higher in the cryogenically frozen product (Table 2). It should be added that the levels of vitamins B1, B2, B6, L-ascorbic acid, α-tocopherol and β-carotene were 2‒38% higher in the cryogenically frozen products, although the differences were not statistically significant. The temperature of frozen storage (‒20 ºC or ‒30 ºC) had no significant effect on the content of the vitamins selected (Table 2). However, frozen mushrooms stored at ‒30 ºC contained 7‒23% more vitamins B1, B3, B6, L-ascorbic acid and α-tocopherol, but 4% less lycopene than those stored at ‒20 ºC.

4.

Conclusion

In both fresh and frozen mushrooms, niacin was the most abundant vitamin, followed by riboflavin. Among the variable factors analysed, the type of pre-treatment and period of frozen storage had the greatest effect on levels of the vitamins analysed; the freezing method and storage temperature had little effect. The greatest losses occurred generally between the 6th and 12th months of storage, leading to the conclusion that for better vitamin retention, frozen A. bisporus should not be stored for longer than 6 months. The greatest losses found after storage were in vitamin B1, L-ascorbic acid and α-tocopherol. In view of the fact that mushrooms contain small amounts of L-ascorbic acid and α-tocopherol, the level of vitamin B1 may be regarded as a quality indicator in frozen A. bisporus.

Acknowledgements

This study was financed by the Polish Ministry of Education and Science under a research Project No. N N 312 241739.

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Mattila P., Könkö K., Eurola M., Pihlava J-M., Astola J., Vahteristo L., Hietaniemi V., Kumpulainen J., Valtonen M., & Piironen V. (2001). Contents of vitamins, mineral elements, and some phenolic compounds in cultivated mushrooms. Journal of Agricultural and Food Chemistry, 49(5), 2343-2348. Nisha, P., Singhal, R. S., & Pandit, A. B. (2004). A study on degradation kinetics of ascorbic acid in amla (Phyllanthus emblica L.) during cooking. International Journal of Food Science and Nutrition, 55, 415–422. Nisha, P., Singhal, R. S., & Pandit, A. B. (2005). Degradation kinetics of folic acid in cowpea (Vigna catjang L.) during cooking. International Journal of Food Science and Nutrition, 56, 389–397. Oms-Oliu, G., Aguilo-Aguayo, I., Martin-Belloso, O., & Soliva-Fortuny, R. (2010). Effects of pulsed light treatments on quality and antioxidant properties of fresh-cut mushrooms (Agaricus bisporus). Postharvest Biology and Technology, 56, 216-222. Phillips, K. M., Ruggio, D. M., Horst, R. L., Minor, B., Simon, R., Feeney, M. J., Byrdwell, W. C., & Haytowitz, D. B. (2010). Vitamin D and sterol composition of ten types of mushrooms from retail suppliers in the United States. Journal of Agriculture and Food Chemistry, 59, 7841–7853. PN-EN 14122:2004/AC:2006. (2006). Foodstuffs – Determination of vitamin B1 by HPLC. Polish Committee for Standardization. PN-EN 14152:2004/AC:2006. (2006). Foodstuffs – Determination of vitamin B2 by HPLC. Polish Committee for Standardization. Reis, F. S., Barros, L., Martins, A., & Ferreira, I. C. F. R. (2012). Chemical composition and nutritional value of the most widely appreciated cultivated mushrooms: An inter-species comparative study. Food and Chemical Toxicology, 50, 191-197. Rickman, J. C., Barrett, D. M., & Bruhn, C. M. (2007). Nutritional comparison of fresh, frozen and canned fruits and vegetables. Part 1. Vitamins C and B and phenolic compounds. Journal of the Science of Food and Agriculture, 87, 930–944. Wang, X.-M., Zhang, J., Wu, L.-H., Zhao, Y.-L., Li, T., Li, J.-Q., Wang, Y.-Z., & Liu, H.-G. (2014). A mini-review of chemical composition and nutritional value of edible wildgrown mushroom from China. Food Chemistry, 151, 279-285.

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Fig. 1 - The average dry matter content and participation in the individual components for fresh and frozen mushrooms at all stages of freezing storage (dry matter content = total carbohydrates + crude protein + crude fat + ash), g/100 g fresh matter.

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Fig. 2 - Content of selected vitamin form B-group in fresh and frozen A. bisporus mushrooms (nb - unblanched, b – blanched, vac – vacuum soaked).

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Fig. 3 - Content of selected antioxidants in fresh and frozen A. bisporus mushrooms (nb unblanched, b – blanched, vac – vacuum soaked).

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Table 1 - The average content of dry matter (in 100 g of fresh matter) and vitamins (in 100 g of dry matter) in fresh and frozen A. bisporus mushrooms (results are an average of the individual stages of analysis for the individual type of product).

0

6

12

7.59±0.03bD

6.17±1.07a

6.16±1.06a

6.17±1.08a

method of preliminary treatment vacuum unblanched blanched soaked 6.38±0.02A 7.29±0.02C 4.83±0.23B

B1 (mg)

1.24±0.03cB

0.48±0.16b

0.40±0.16b

0.23±0.11a

0.41±0.15B 0.26±0.22A

0.37±0.11AB

B2 (mg)

5.06±0.18dB

3.72±0.57c

3.28±0.53b

1.57±0.22a

2.47±0.85A 2.43±0.84A

3.16±1.28A

B3 (mg)

362±cC

229±71b

190±47ab

154±40b

165±59A

281±51B

169±46A

pyridoxine

3±1

nd

nd

nd

nd

nd

nd

pyridoxal

12±1aA

13±13a

17±10ab

27±25b

9±12A

28±16B

23±23AB

pyridoxamine

937±4dC

514±203c

389±143b

263±83a

322±184A

280±63A

489±152B

sum of all forms

953±3dC

527±202c

406±139b

290±96a

331±184A

308±51A

512±147B

L-ascorbic acid (mg)

80±1dB

57±6c

39±11a

34±17a

33±15A

38±5B

22±6A

α-tocopherol (mg)

3.17±0.04cC

1.08±0.48b

0.78±0.36a

0.54±0.17a

0.96±0.57B 0.69±0.13AB

0.57±0.21A

β-carotene (mg)

2.85±0.03dB

2.43±0.10c

2.18±0.12b

2.03±0.11a

2.21±0.24A 2.15±0.14A

2.16±0.18A

dry matter (g)

B6 (µg)

vitamin

fresh mushrooms

time of frozen storage (months)

1.70±0.02dB 1.56±0.10c 1.42±0.09b 1.28±0.07a 1.42±0.15A 1.35±0.13A 1.39±0.13A lycopene (mg) γ-, δ-, β- tocopherols were not detected; nd – not detected; means with different small letters (fresh mushrooms and time of frozen storage) or capital letters (fresh mushrooms and method of preliminary treatment) in a row represent significant differences at p < 0.05.

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Table 2 - The average content of dry matter (in 100 g of fresh matter) and vitamins (in 100 g of dry matter) in fresh and frozen A. bisporus mushrooms (results are an average of the individual stages of analysis for the individual type of product).

dry matter (g)

fresh mushrooms 7.59±0.03bB

method of freezing blast cryogenic 6.09±1.15a 6.24±0.96a

temperature of frozen storage ‒20 ºC ‒30 ºC 6.17±1.06A 6.15±1.08A

B1 (mg)

1.24±0.03bB

0.34±0.19a

0.35±0.16a

0.30±0.17A

0.32±0.16A

B2 (mg)

5.06±0.18bB

2.58±1.03a

2.79±1.06a

2.43±1.00A

2.43±0.96A

B3 (mg)

362±6cB

161±37a

207±65b

155±44A

190±44A

3±1

nd

nd

nd

nd

12±1aA

20±14a

21±23a

20±21A

24±19A

937±4bB

333±189a

394±137a

310±123A

342±143A

953±3bB

353±189a

415±132a

330±121A

366±143A

L-ascorbic acid (mg)

80±1bB

35±13a

36±16a

28±11A

32±9A

α-tocopherol

3.17±0.04bB

0.63±0.22a

0.87±0.51a

0.63±0.31A

0.68±0.30A

β-carotene (mg)

2.85±0.03bB

2.15±0.20a

2.19±0.17a

2.11±0.13A

2.10±0.15A

vitamin

pyridoxine B6 pyridoxal (µg) pyridoxamine sum of all forms

1.70±0.02bB 1.40±0.16a 1.37±0.12a 1.37±0.11A 1.32±0.10A lycopene (mg) β-, γ-, δ- tocopherols were not detected; nd – not detected; means with different small letters (fresh mushrooms and method of freezing ) or capital letters (fresh mushrooms and temperature of frozen storage) in row represent significant differences at p < 0.05.

18