Changes of Soluble Sugars, Organic Acids and Respiration Rates of Not-from-concentrate Apple Juice in Different Processing Stages
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Abstract:
The changes of sugar and acid flavor substances and respiratory rate of Embden-Meyerhof-Parnas, Tricarboxylic Acid Cycle Pathway, Pentose Phosphate Pathway, Cytochrome Pathway and Alternative Pathway in samples of Non-From-Concentrate (NFC) apple juice processing including raw materials, juice extraction, enzyme inactivation, homogenization, ultrasound, sterilization, and canning were detected. Then, the key links affecting flavor quality and the approximate ways of flavor substance conversion during fruit juice processing were clarified and the basis for further optimizing the industrial production process of NFC apple juice processing was provided. The results showed that the flavor quality change during NFC apple juice processing could be divided into two stages: from raw material to the juice squeezing section and from the enzyme inactivation to canning. In the first stage, the contents of glucose and sorbitol were increased by 49.12% and 20.59% , respectively, the content of malic acid was increased by 8.06%, the content of oxalic acid was decreased by 7.01%, the respiratory rate of the TCAC pathway was increased by 0.64 times and CP was decreased by 0.85 times; In the second stage, the changes of fructose, glucose, malic acid and oxalic acid content and total soluble solid/titratable acidity were normally distributed, which were related to the changes of EMP, TCAC and AP respiration rate. Therefore, the effects of different processing stages on the sugar acid and acid flavor components and respiratory rate of the fruit juice are different. Heat treatment is the key link of controlling flavor quality during NFC apple juice processing. The central metabolic enzymatic reaction of the juice should be strengthened to optimize the flavor quality.
