بررسی تاثیر پوشش‌دهی تخم‌مرغ با استفاده از بیوپلیمر نشاستهاسید اولئیک اصلاح شده با پرتو فرابنفش بر افزایش کیفیت و ماندگاری تخم‌مرغ

زمینه مطالعاتی: پوشش دهی تخم مرغ با هدف افزایش ماندگاری و کیفیت تخم مرغ در طی مدت انبارمانی محصول هدف: در میان مواد غذایی، تخم‌مرغ به علت داشتن میزان بالای پروتئین، اسید آمینه‌های ضروری و ویتامین‌های محلول در چربی از اهمیت ویژه‌ای برخوردار است. در تخم‌مرغ مقداری آب و گاز دی‌اکسید کربن وجود دارد که موجب حفظ کیفیت و تازگی تخم‌مرغ می‌شوند. این دو جزء، طی دوره نگهداری تخم‌مرغ، از منافذ موجود در پوسته خارج می‌شوند، به‌این‌ترتیب کیفیت تخم‌مرغ اُفت می‌کند. در این پژوهش به‌منظور جلوگیری از خروج آب و گاز دی‌اکسید کربن موجود در تخم‌مرغ، از روش پوشش‌دهی سطح تخم‌مرغ با محلول نشاستهاسید اولئیک در جهت افزایش کیفیت و ماندگاری آن استفاده شد. روش کار: در این پژوهش از 75 عدد تخم‌مرغ در قالب طرح کامل تصادفی با 5 گروه آزمایشی و هر گروه شامل 15 عدد تخم‌مرغ در مدت زمان هفت هفته مورد بررسی قرار گرفتند. تیمارهای آزمایشی شامل شاهد( تخم‌مرغ بدون پوشش)، تخم‌مرغ‌های پوشیده شده با محلول نشاستهاسید اولئیک اصلاح شده به کمک پرتوی فرابنفش (uvc) در بازه‌های زمانی 0، 30، 60 و 90 دقیقه بود. طی دوره نگهداری هفت هفته‌ای و در زمان‌های مشخص( هفته صفرم(بلافاصله بعد از پوشش‌دهی)، هفته اول، هفته سوم، هفته پنجم و هفته هفتم) تخم‌مرغ‌های پوشش‌دار و فاقد پوشش مورد ارزیابی کمی و کیفی قرار گرفتند. نتایج: ارزیابی کیفیت تخم‌مرغ براساس اندیس هاو و اندیس زرده نشان دادند که، در هفته هفتم دوره نگهداری برای تخم مرغ های پوشیده شده با نشاستهاسید اولئیک و نشاستهاسید اولئیک اصلاح شده با uvc به مدت 90 دقیقه بیشتر از این اندیس ها در تخم مرغ های فاقد پوشش در هفته اول بودند. نتیجه‌گیری نهایی: با استفاده از پوشش دهی تخم‌مرغ‌ با نشاستهاسید اولئیک و نشاستهاسید اولئیک اصلاح شده با uvc به مدت 90 دقیقه می توان ماندگاری تخم مرغ را تا بیش از دو برابر از حالت طبیعی افزایش داد.

Investigation into the shelf life extending of chicken eggs using UVC irradiated starcholeic acid coating solutions

> p >Introduction: The extension of the shelf life of chicken egg by the coating during the storage is the main purpose of this study. Chicken egg is one of the most important foods because of the high protein, essential amino acids and fatsoluble vitamins content. The freshness of chicken egg maintain by water and carbon dioxide. They emit to surrounding atmosphere through shellpores during the shelf life of the chicken egg. It leads to reducing the quality of chicken egg. The shelf life of chicken egg can be extended by preventing the emission of the gases using biopolymer coating. Starch is one of the best options to coating chicken egg. Starch is biobased, easy access and low price material. The presence of hydroxyl groups in the starch chains create hydrogen bonds between starch and water. As well as the considerable free space between the starch chains facilitate the movement of the water molecules through this space. The high permeability of starch to water vapor is an obstacle to achieving this aim. Nevertheless, virgin starch can be decreased water vapor permeability by increasing water transition distance. Furthermore, water vapor barrier properties might be intensified by hydrophobic materials i.e. lipids, into the formulation of solution coating. Oleic acid (OA) is a fatty acid that can reduce water vapor transition rate of the hydrophilic biobased materials. OA is a liquid fatty acid at room temperature. Hence, it is miscible with biobased material easier than saturated fatty acid without further heating treatment. The hydrophilicity and the permeability of starch to water vapor can be resolved using mixing with fatty acids. On the other hand UV irradiation as an inexpensive, easy to operate and environmentalfriendly (green) technology, to modify the biopolymers, has received increasing attention during recent years. However, other ionizing beams i.e. Gamma can improve some packaging properties of biopolymers. But there is a serious concern about its nuclear wastes. UV radiation induces the production of free radicals in aquatic solutions. The free radicals attack to starch chains. As a result, the injured chains possess a tremendous potential to produce crosslinks. Accordingly, it seems that the exposure of the aqueous film solution to UV ray can be used as a green process to modify the packaging properties of biopolymers. Material and methods: An aqueous dispersions of starch (5 wt%) was prepared and heated until its gelatinization (85°C for 90 min). Glycerol as plasticizer (40 wt% of dry base) was also added. Then the solution was stirred for 15 min. Oleic acid (OA) (1 wt% of dry base) mixed with Tween 80 as emulsifier (10 wt% of the OA). This solution was mixed and heated )50 ˚C for 10 min (Then, 10 ml of distilled water was added gradually to the solution, and homogenized by ultrasonic homogenizer (Dr. Hielscher, Teltow, Germany) for 7 min. The OA based emulsion was added to starch solution gradually and mixed for 10 min. after that the solution was homogenized again by ultrasonic homogenizer for 7 min. The solution mounted under three UVC lamps (8w, Phillips, Holland) at a distance of 5 cm. The solution was stirred during this time with using a magnetic stirrer. After 0, 30, 60, and 90 minutes, the UVC exposed solutions were applied to chicken egg coating. Results and discussion: Weight loss of eggs during storage is mainly caused by evaporation of water from the albumen through the porous shells. The weight loss increased during 7 weeks storage. The greatest water loss (11.83%) was observed in control (uncoated eggs). Coating the shell egg led to minimum weight loss. The results of Haugh index (HU) and Yolk index (YI) showed, however in all treatments HU and YI decreased. But this reduction was less than the control. Starcholeic acid, and modified starcholeic acid for 90 min by UVC showed the most HU and YI. The pH of albumen is an important factor in the quality of chicken egg. Moisture and carbon dioxide of the white evaporate through the pores and replace by air. Decreasing the CO2 content lead to increasing pH of the eggs. The properties of the albumen were affected by this phenomenon. The pH of albumen was increased in control, while in the coated eggs it was remained almost constant. The albumen of the coated eggs by starcholeic acid and modified starcholeic acid for 90 min by UVC have the least pH. Conclusion: Regard to the results starcholeic acid and modified starcholeic acid for 90 min by UVC were the best options to coating the egg shell and increasing the shelf life of the egg. It seems these coating can extend the shelf life of the egg more than two times.