Study On The Critical Factors For Quality Of Cloudy Apple Juice

This research was supported by the tenth five year's scheme of National key technology programme. The research was one part of project 'research and development of deep processing technology for agricultural product', and was about processing technology for cloudy apple juice.Critical factors that effect quality of cloudy apple juice, including maturity of raw apple, processing technic and storage condition, were studied in this research. This research can provide useful reference value for products processing and industry standard about cloudy apple juice processing.Apple with maturation and ripening were selected as raw apple for cloudy apple juice. Raw apple with ripening was more suitable for producing cloudy apple juice. When producing cloudy apple juice, apple juice was easier to brown by raw apple with ripening than by raw apple with maturation. PPO activity of apple juice by raw apple with ripening was inactive after 20S at temperature of 90 ℃. But to inactive PPO activity of apple juice by raw apple with maturation, it lasted 25S in the same temperature. Cloudy apple juice from raw apple with ripening was easier to be accepted by customers because of good color and turbidity, and was steadier to store.The following processing of cloudy apple juice was studied:To protect color of cloudy apple juice, 0.07% content of ascorbic acid was added to cloudy apple juice, and enzymatic browning was inhibited. 0.020% ascorbic acid and 0.075% sodium chloride content in cloudy apple juice was also satisfactory to inhibit enzymatic browning.Activity of PPO (Polyphenoloxidase) and PME (Pectin methylesterase) are two critical factors that effect quality of cloudy apple juice. The activity of the two enzymes should be inactive when processing apple juice. The optimum activity mensurational conditions were optimized.Temperature of 90 ℃ after 20S for PPO and 80℃ after 30S for PME heat-inactivation was satisfactory.After heat-inactivation, temperature of cloudy apple juice should be cooled to 40 ℃ to protect color and sense turbidity.Turbidity of apple juice decreased significantly and stablity of turbidity of apple juice improved greatly by centrifugal effect. Speed of 3000rpm lasting 15min by centrifugal effect was selected as processing parameter. Equation was modeled to evaluate relationship between transmittance of apple juice and centrifugal effect (including time and speed of centrifugal effect)..Cloudy apple juices was stored on temperature of 25℃, 4℃ and-18℃. Quality of cloudy apple juice stored on temperature of-18℃ was better than others after long time.