Study On Browning Prevention Technology Of Apple Juice

Apple juice is rich in nutrients and is the main direction of apple processing.The brown substances produced by non-enzymatic browning during the production and storage of apple juice seriously affect the sensory quality,in order to keep the color value of fruit juice well,the factors affecting the color value of apple juice should be deeply analyzed.This experiment mainly studied the following four aspects:the effect of different varieties of apples on the browning of apple juice;the effect of different mechanical damage on the browning of apple juice;the effect of different inhibition treatment on the browning of apple juice;and the effect of different temperature and light on the concentration of apple juice during storage.The results are as follows:(1)The browning of apple juice after 28 days storage was determined for three kinds of apple juice,namely Red Fuji,Golden Delicious and Wang Lin.The order of browning of three kinds of apple juice is:Golden Delicious<Wang Lin<red Fuji.The yellow value(b*),soluble solids content and titratable acid content of Golden Delicious were significantly higher than those of Wang Lin and Red Fuji,and the browning degree and total phenol content of Golden Delicious apple juice were lower than those of Red Fuji and Wang Lin in the later storage period.(2)Using Golden Delicious apple as the experimental material,the apple juice of 100%good fruit,50%good fruit and 50%mechanical damage apple and 100%mechanical damage apple were studied.The effects of apple with different mechanical damage on Browning of apple juice after 42 d storage were studied.The causes of apple juice browning were analyzed by determining the content of soluble solids,color index(brightness value,redness value and yellowness value),browning degree(A420),pH value,amino nitrogen,reducing sugar content and total phenol content in apple juice during different storage periods.The results displayed that the decrease of amino nitrogen and total phenol content in 100%mechanical damaged apple juice was higher than that in 100%good apple juice and 50%good apple juice+50%mechanical damaged apple juice,indicating that Maillard reaction and oxidative polymerization of total phenol substances deepened the browning of apple juice during storage.The greater the proportion of mechanical damage to raw apples,the more the browning rate of apple juice will be increased,and the color value of apple juice will be lower.The proportion of raw materials for mechanical damage to apples should be controlled below 50%.(3)In order to study the method of inhibiting the browning of apple juice,apple juice made from Golden Delicious apple was used as the experimental material.The effects of citric acid,L-ascorbic acid,L-cysteine and blanching temperature on browning inhibition of apple juice were compared by single factor experiment.The response surface methodology was used to optimize the different inhibition methods.The conclusion showed that the optimum combination of inhibition methods for browning of apple juice stored for 42 days was:the optimum concentration of citric acid was 0.12%,the optimum blanching temperature was 90? the optimum concentration of L-cysteine was 0.15%.The inhibition rate of browning reached 93.22%.(4)Concentrated apple juice with 70.25%soluble solids was used as the experimental material to study the important substances related to non-enzymatic browning of apple juice during storage.It was concluded that the browning of concentrated apple juice was the most serious after 40 days storage at 37?,which indicated that high temperature had a greater impact on non-enzymatic browning during storage.It is suitable for apple juice concentrate at 4? during storage.Browning degree was positively correlated with 5-hydroxymethyl furfural content,and reducing sugar content decreased,increased and then decreased at three different storage temperatures.There was a negative correlation between browning degree and amino nitrogen and reducing sugar.The browning of concentrated apple juice was aggravated by light treatment.