تاثیر پوشش کیتوزان با درجات مختلف استیل‌زدایی در ماندگاری قارچ دکمه‌ای خوراکی (agaricus bisporus)

یکی از موثرترین روش ها برای افزایش طول مدت نگهداری قارچ خوراکی دکمه‌ ای، استفاده از پوشش های خوراکی است. در این مطالعه، تاثیر کیتوزان به عنوان یکی از پوشش های خوراکی، با درصدهای استیل‌زدایی متفاوت (70 تا 100 درصد) با سه غلظت‌های مختلف مورد بررسی قرار گرفت. تاثیرات پوشش کیتوزانی بر روی افت وزنی، رنگ قارچ و اندیس قهوه ای شدن، فعالیت آنزیمی، بافت و ترکیبات فنلی کل مطالعه شد. به این منظور قارچ ‌ها در محلول ‌های کیتوزان با غلظت‌ های 0.5، 1 و 2 درصد پوشش داده شدند و برای مدت 12 روز در دمای 4 درجه سانتی‌گراد نگهداری شدند. نتایج آزمون ‌ها حاکی از تاثیر مناسب پوشش ‌دهی کیتوزان بر نمونه های قارچ خوراکی بود، به طوری که میزان فنل کل در تیمار کیتوزان با درجه استیل‌زدایی70 درصد با غلظت یک درصد، در روز دوازدهم به (u g-1) 0.45 رسید، میزان آنزیم پراکسیداز در تیمار کیتوزان 70 درصد استیل‌زدایی شده با غلظت 0.5 درصد، (u g-1)  0.8 بود و میزان سفتی نمونه در تیمار کیتوزان با درجه استیل‌زدایی شده 70 درصد با غلظت 2 درصد، تنها به میزان 401 گرم کاهش پیدا کرد در صورتی که نمونه شاهد به میزان 3385.5 گرم، سفتی خود را از دست داد. در کنترل افت وزنی، تیمار 100 درصد استیل‌زدایی شده با غلظت 2 درصد بهترین نتیجه را نشان داد و تنها 1.11 درصد افت وزنی داشت. آنزیم پلی‌فنل اکسیداز در تیمار 90 درصد استیل‌زدایی شده با غلظت 2 درصد، در روز دوازدهم آزمایش به 0.67 (u g-1) رسید. تیمار کیتوزان با درجه استیل‌زدایی 100 درصد و 90 درصد در آزمون حسی، نتیجه بهتری از ارزیاب ها دریافت کرد. تیمار کیتوزان با درجه استیل‌زدایی 90 درصد و غلظت 0.5 درصد، عملکرد بسیار مناسبی نسبت به اندیس قهوه ای شدن نشان داد، به‌طوری که در روز دوازدهم آزمایش، اندیس قهوه‌ ای شدن نمونه به میزان 85.47 رسید.

effect of chitosan coating with different degrees of deacetylation on the shelf life of button mushroom (agaricus bisporus)

introductionwith the growth of the population and increasing demand for obtaining food and supplying the required food, the interest in the cultivation and consumption of edible mushrooms has increased. since 1990, the world has focused on the mushroom production industry. in recent years, mushrooms have become one of the most important food and medicinal sources. one of the largest species of edible mushroom is button mushroom (agaricus bisporus), which has high nutritional value due to the presence of fiber, carbohydrates, protein, amino acids, minerals, vitamins, etc., and also its antioxidant, anti-cancer, and anti-diabetic properties. this commodity has shown good health benefit for humans. the quality of button mushrooms is determined by their color, texture, and taste. color is the first characteristic that is perceived by consumers. browning is one of the main reasons for the loss of mushroom quality, which reduces the commercial value of mushrooms. edible coating is considered as the best method for maintaining quality of perishable foods, these coatings almost prevent the penetration of oxygen, depending on the type of coating used, and reduce the loss of moisture during storage. chitosan has functional characteristics such as antimicrobial and antioxidant properties. the purpose of this research was to find a suitable chitosan coating for button mushrooms that can maintain its characteristics such as color, texture hardness, and moisture during the storage period and increase the shelf life of  mushroom. materials and methodsto make chitosan solutions, first, each type of chitosan (70% deacetylated, 80% deacetylated, 90% deacetylated, and 100% deacetylated) was weighed in amounts of 0.5g, 1g, and 2g., then it was dissolved in 100 ml of 0.5% acetic acid  and stirred for 12 hours at a speed of 1000 rpm at room temperature to dissolve uniformly. after 12 hours, each sample was centrifuged for 15 minutes at 6000 rpm at 25°c to separate undissolved materials. mushrooms were prepared freshly harvested, washed with water, and then excess water was removed. after sorting and screening in terms of size and approximate weight, the mushrooms were added to 0.5%, 1%, and 2% chitosan solutions without being sliced and were immersed in the solution for one minute. the control sample was immersed in 0.5% acetic acid solution for one minute. after that, the mushrooms were air-dried at room temperature for one hour, and at the end, their excess water was removed with a tissue. the mushrooms were placed in 18*14 size polyethylene zip lock bags and stored in a refrigerator at 4°c. the effects of chitosan coating on weight loss, color and browning index, enzyme activity, texture, and total phenolic compounds of mushroom were studied. results and discussionthe spoilage of edible mushrooms happens in a short time, and the storage of mushrooms has become one of the most important challenges in mushroom marketing. coating edible mushrooms is one of the suitable methods to increase the shelf life of edible mushrooms. in this research, chitosan with four degrees of deacetylation and three different concentrations was used as a coating for button mushroom. the results indicated that coating the mushroom with chitosan could delay the occurrence of spoilage and change its color or texture. due to the very strong antimicrobial properties of chitosan, it is suggested to investigate the microbial load of edible button mushrooms ans other tissue factors of the mushroom, such as gumminess, adhesive properties and cohesieveness. conclusionthe spoilage of edible mushrooms happens in a short time, and the storage of mushrooms has become one of the most important things in mushroom production. coating edible mushrooms is one of the suitable methods to increase the shelf life of edible mushrooms. in this research, chitosan with four degrees of deacetylation and three different concentrations was used as a coating for button mushroom.