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Research on Fresh-keeping and Quick-frozen Technology of Agaricus Bisporus

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Tutor: LiZuo
School: Henan Agricultural University
Course: Of Food Science
Keywords: Agaricus bisporus,Polyphenol oxidase,Color fixative,Blanching,Frozen
CLC: TS219
Type: Master's thesis
Year:  2011
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Abstract:
With the raw materials of bisporic mushroom in this paper,probed the important influence of enzymatic Browning on polyphenol oxidase (PPO) characteristics and the various physical-chemical properties change in fresh-keeping trials. And systematic studied the inhibition of frozen process in different dillenii on polyphenol oxidase(PPO) and best after dispensing,and optimizad the optimal temperature and the hot iron time in hot bleaching process. And determined the curve of different freeze under the way of freezing temperature and in different ways to freeze the microstructure and the effect of bisporic mushroom chemical characteristics under freezing temperature, the main conclusions are as follows:1, with catechol as the substrate,and nvestigated the part of characteristics of polyphenol oxidase under 420nm. Research showed that the optimal enzyme is 30¡æ, reaction temperature of heat are more sensitive, in 90¡æ,heating 80s the enzyme activity has basic inactivation; the optimal pH is 5.5, while in pH 450 ~ 5.5 ,the enzyme activity is stronger. In pH < 4.5 and pH > 5.5, enzyme activity was significantly lower, when pH acuities < 2 or pH>8, polyphenol oxidase have basic deactivation.Meanwhile ascorbic acid, citric acid, sodium chloride and EDTA making four inhibitors on bisporic mushroom polyphenol oxidase ,and with the increase of concentration inhibitory the effect enhanced. In inhibitors under the same concentration, the inhibition effect of Vc isbest.The inhibitory effect from strong to weak order is Vc > citric acid > citrate sodium > EDTA-Na.Therefore, making the bisporic mushroom in storage period, can use instantaneous heat, adjust pH, add inhibitors to inhibit or passivation methods oxidase ppo, reduce its Browning level, which will bring about the bisporic mushroom fresh-keeping processing, transportation, and has great significance.2, through the preservation ,we concluded that: The storagement is very short for fresh bisporic mushroom under normal temperature ,as storaged the extension of time fruitbody began to appear dehydrate contraction, skin and internal Browning, open umbrella feeble etc. Phenomenon, It would lost their edible value and commodity value under general storage than six days; 4¡ærefrigerator preservation can relative extend its storage time, but generally will not exceed 10 days, also can appear fruitbody internal Browning serious, mushroom table appear mildew spot and produce peculiar smell, lose edible value wait for a phenomenon.3, By selecting various inhibitor to protect color experiment, to study the influence in different inhibitors of bisporic mushroom polyphenol oxidase, the results showed that ascorbic acid, citric acid, sodium chloride are all represent better inhibition effect on PPO enzymatic activity, its optimal concentration range respectively is 0.1% ~ 0.3%, 0.3% ~ 0.5%, 6%~ 8%; Oxalic acid, ethylenediamine tetraacetate of enzyme activity also showed some suppression, but inhibition effect is not obvious, sodium dihydrogen phosphate and disodium phosphate on PPO enzymatic showed activation function, not suitable for PPO inhibitors.4, On the basis of single factor experiment, using the response surface method, through three levels of three factors of experiments, the quadratic regression ascorbic acid, citric acid and sodium chloride three factors in for example polyphenol oxidase (PPO) active influence; An optimization factor and test the regression mathematics model between factor; Determined the best protect color preservation complex match concentration for: ascorbic acid 0.24%, citric acid0.43% sodium chloride7.03% respectively.5, Through choice the different of temperature on iron bleaching to test the variation in different hot bleaching temperature polyphenol oxidase, the live of enzyme residue law from 0.5 ~ 2min, enzyme inactivation rate is relatively slow. From 2 ~ 4min enzyme inactivation rate can exceed has increased dramatically, after 4min ,90% enzyme is inactivation, some are almost all deactivation. So by single factor experiment we can draw the conclusion that :different temperatures can bisporic mushroom 4min, iron drift around can effectively restrain PPO enzymatic activity of bisporic mushroom, suppressing enzymatic Browning purpose, namely the best range of 3 ~ 5min, very hot bleaching time 85 to 95¡æ.6, in the process of optimization for the hot bleaching time and hot iron bleaching best drift temperature, applied the response surface method, the two factors of the quadratic regression test three level, studies the influence of hot temperature and hot bleaching time drift of two factors for bisporic mushroom polyphenol oxidase (PPO) active; An optimization factor and test the regression mathematics model between factor.Results indicated that the best hot temperature is 90¡æ, drift in the temperature of the best time for iron bleaching is 5min.7, Through the measured of quick frozen and slow frozen curve and the study of freezen on impactquality of bisporic mushroom ,we could draw that: the influence of quick frozen in inhibiting PPO activity and the cellular structure and the effect the texture characteristics significantly better than slow frozen. The reason is slow frozen through the largest long generated ice forming first, extracellular solution inland, the ice move outward form big ice crystals, has a lot of cell walls mechanical damage to cells, cause major damage, in the process of thawing juice loss more, fruitbody dehydrate contraction become soft, great influence on the cellular structure; Quick frozen through the biggest with short time, the formation of ice formed inside the cells is small, closely spaced ice crystals, undermine the role of mushroom cells lesser, defrost fruitbody dehydrate less, fruitbody harder because of the process, the mushroom hot bleaching somatic also has certain damage, but obviously superior to save the integrity of the cells in the slow frozen after iron bleaching. After protect color and hot for rapid freezing of drift can inhibit about 90% of PPO activity, and can kill apart of microorganisms, from a business perspective part to consider, quick-frozen process is better achieve purpose, anf has high commercial value for bisporic mushroom.
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