Study On The Effects Of Pre-treatment And Ultrasound-assisted Immersion-freezing On Enzymes And Nutrients Of Agaricus Bisporus

According to the problems such as browning , reduction of nutritions and loss of active components, occuring during the process of freezing edible mushrooms, we take some technologies, such as colour protecting, steam (high temperature– short time, HT-ST) blanching ,microwave and steam (high temperature– short time, HT-ST) combined blanching and ultrasound-assisted immersion-freezing, to promote the qualities of frozen edible products.Firstly,we have color protection research.On the basis of adding ascorbic acid and citric acid, we respectively put CaCl₂, EDTA - Na0₂, homocysteine, CaCl₂+N - acetyl - cysteine into it , by indicators,such as polyphenol oxidase PPO, soluble protein and Vc, structure– hardness and chromatism, we get the results. The results show that Treatment 5 which has 0.08% Vc + 0.04% CA +0.6% CaCl₂+ 0.1% N - acetyl - cysteine, can best maintain the quality of Agaricus bisporus.Secondly, after the single-factor experiments of steam blanching times, material quantities , steam pressures, orthogonal test was designed. With the comprehensive evaluation and analysis of effects of PPO inactivation and ascorbic acid content, the optimum condition was determined: steam blanching time 80 s , material quantity 200 g, steam blanching pressure 300 Pa, which got the highest evaluation score. Then we did a comparative study among the optimal results of steam (high temperature-shorttime) blanching, hot water blanching and single microwave blanching, which reflected that the way steam (high temperature-shorttime) blanching has advantages over PPO inactivation and keeping nutrinational qualities.Thirdly,after the single-factor experiments of microwave intensity, microwave processing times, steam intensities, steam treatment times, orthogonal test was designed. With the comprehensive evaluation and analysis of effects of PPO inactivation and ascorbic acid content, the optimum condition was determined: microwave intensity 5.656 w/g, microwave processing time 120 s, steam intensity 2.69 Pa/g, steam treatment time 80 s ,which got the highest evaluation score. Then we did a comparative study among the optimal results of combined with microwave and steam(HTST) blanching, results of hot water blanching, results of single microwave blanching and results of single steam (HTST)blanching, which reflected that the way of combined with microwave and steam(HTST) blanching has advantages.Finally, study the effects of ultrasound-assisted immersion-freezing on the freezing process of Agaricus bisporus. The single factor experiments of ultrasonic power and ultrasonic exposure times is investigated . Response surface methodology (RSM) is employed to optimize their addition levels in ultrasound-assisted immersion-freezing on the freezing process of Agaricus bisporus. The results show that the best conditions for ultrasonic power x₁ is 69.6 119.16 W, ultrasonic exposure time x₂ is 2.32 2.9895 min, in this area, Y₁ can reach the minimum, meanwhile Y₂ can achieve maximum.