Study On Quick-frozen Technology Of Boletus Roseoflavus Hai B.Li & Hai L.Wei

In this study,Boletus roseoflavus Hai B.Li&Hai L.Wei was used as the object of study.For the existence of ordinary frozen products exists the following problems:the slow freezing speed,freezing uneven,the flow of soft rot juice,turn brown,rancidity and other issues after thawing.First of all,the enzyme activity and the change patten of the raw materials of quick frozen mushroom were studied.On this basis,the effects of high temperature instantaneous steam,microwave,hot water and so on,as well as the technology of high efficiency carbon dioxide spray freezing,and the fluidization of single freezing were studied.This paper discussed how to improve the quality and added value of traditional edible mushroom products.The whole process is as follows:raw material selection,weighing,cleaning.color fixing before fixing,freezing before freezing,frozen storage.The whole process of the research focuses on three process stages:color technology,fixing technology,quick freezing process.And Need to protect the color two times before the fixation and before the storage.In order to finish fixation completely,should turn over the surface in two times.The material was fresh Boletus roseoflavus in same maturity,and removed discoloration,insect pest,damage and other parts.Then gently rinsed clean with running water flow and reserved.In the process of color protection,the clean Boletus roseoflavus were delivered into the 0.5kg each.Different combinations of different color protection liquid immersion with 0.4 g/kg sodium pyrosulfite,0.1%D-sodium erythorbate,0.01%citric acid,NaCl solution,CaCl2 solution,and so on.There are three repetitions in each color protecting liquid.After repeated comparison,the best combination of color protecting liquid and soaking time were selected.The fixation process contained microwave,hot water and high temperature instantaneous steam three ways.Through the effect of each method on the enzyme activity and color difference,the optimal process was selected.It should be noted that each time it is immediately dropped into the liquid to cool after fixation(to prevent the formation of ice crystals),the mushroom body temperature down to 5 ? below.Then frozen them into the ordinary storage.The freezing process was studied using four freezing methods:tunnel freezing,ordinary cold storage freezing,liquid nitrogen freezing,and magnetic tunnel freezing.Through the quick frozen samples to detect the color difference,the drip loss,hardness,sensory evaluation of four indicators,single factor analysis and multiple comparisons,to select the best freezing technology.The results were as shown below:1.In the process of color protection,used 0.4 g/kg sodium metabisulfite + 0.1%VC + 0.01%citric acid as the color protection liquid solution with the soaking time of 1.5 min,the best effort could gain to better maintain the quality of Boletus roseoflavus.2.The fixation process contained microwave,boiling water and high temperature instantaneous steam three ways to treat the samples.Through the effect of each method on PPO,SOD enzyme activity,color difference,sensory evaluation,the optimal method of fixation was selected.The optimal and worse order to the three kinds of fixation ways were:microwave fixation>steam fixation>boiling water fixation.3.Quick freezing method has ordinary cold storage freezing,tunnel freezing,magnetic tunnel freezing and liquid monomer freezing(liquid nitrogen freezing).From the degree of color difference,discoloration of the Boletus roseoflavus in tunnel freezing is 15,which is better in quality than magnetic field tunnel freezing and liquid nitrogen freezing.From the hardness,microwave fixation can obtain better product quality in most freezing ways,but under the condition of liquid nitrogen monomer freezing.the hardness of non color without fixing is higher than that of color protection with microwave fixation.From the point of drip loss,combination of tunnel freezing without color protection and fixation and the microwave which in fixation of stream was optimal,and the drip loss was the lowest.From the sensory evaluation,the best was the tunnel freezing with 18.2 point.In general,Boletus quality varied in different combination of color protection and fixation methods in different freezing conditions.Therefore for different freezing modes corresponding need to optimal choice to freeze treatment to achieve the best effect on quality.This results also showed that there were significantly difference in effects of drip loss with different fixation treatments and freezing methods(up to 30%).The greater the drip loss,the worse the quality of the product,and the easier it is to melt and cause the product to become soft,rotten,and decayed.So the drip loss rate should be the main factor to affect the quality of Boletus,which should be considered in the frozen process design.