Inhibitory Of Enzymatic Browning On HanFu Apple Juice And Its Volatile Aroma Composition Analysis

HanFu apple is an independent research, developed by Shenyang Agricultural University. Its perfect characteristics make it possible to be the best choice of apple juice when processing the raw materials. But it can easily happened enzymatic browning in apple juice during production process, and can seriously influence the sensory, nutrition and flavor in fruit juice. This paper, the research of polyphenol oxidase (PPO) in the HanFu apple juice, intended to find a way to inhibit fruit juice browning. To provides a theoretical support and reference for HanFu apple juice to improve production and its polularization. The main research contents and research results were as follows:1. HanFu apple juice PPO enzymatic properties shows that the optimum temperature is 30 ℃, the optimal extract of pH is 7.2. By rising the temperature can we control the activity of enzyme. By adding 5 single inhibitors, We can compared the color difference among kojic acid, L-cysteine, protein isolates and citric acid as well as the β-cyclodextrin in apple juice screening,in order to pick out three single most reasonable quality inhibitors:kojic acid, L-cysteine, protein isolated. The juice have a perfect inhibition concentration when the kojic acid concentration is respectively during the period of 0.1 to 0.2 g/mL, the concentration of L-cysteine is during 0.1 to 0.2 g/mL, concentration of the protein isolated is during the 0.2 to 0.3 g/mL. Then through the method of the response surface to optimizate the ratio of inhibitors, the optimal combination for kojic acid inhibitor content is 0.16%, content of L-cysteine is 0.13%, separation of the protein content is 0.25%. In this condition, the inhibition rate of apple juice can reach 78%(P< 0.05).2. By Analyzing the ultra-high pressure influence on HanFu apple juice, we concluded that when the pressure is close to 600 MPa so that it can minimize the number of colonies in the juice. Changes in pressure and holding time can not influence the pH of juice and total soluble solid type.400 MPa, after 25 min conditions can both inhibit the colour change of juice. Last, the condition of best inhibition effect of PPO activity in apple juice were the pressure of 400 MPa, the holding time is 10 min, temperature of 30 ℃ by the single factor test which use the pressure, the holding time and temperature as factors. Then using response surface method to optimize the best ultra-high pressure condition of inhibit PPO activity, the best ultra-high pressure condition was pressure maintain it for 7 min, container temperature is 28 ℃, the pressure of 506 MPa can effectively inhibit the activity of PPO, the inhibition rate was 64.86% (P< 0.05).3. Using GC-MS to detect the aroma components of the apple juice at before or after adding inhibitor and with the increasing placing time which the change were analyzed. Fresh apple juice were determined for 25 kinds of volatile aroma composition, total content of 1.338 μg/mL. With fresh apple juice to be placed in 12h at room temperature, there were 29 kinds of volatile aroma composition, total content of 1.197 μg/mL. With fresh apple juice to be placed in 12h at room temperature, volatile aroma composition of species in the apple juice will increase along with the increasing of mixing time. Howerver, the total content will decrease with the increase of the storage time. Aldehyde as the main aroma components in fresh juice, the types and content have reduced by more than half. Adding inhibitor of fresh apple juice were determined for 39 kinds of volatile aroma composition, total content of 1.077 μg/mL. As adding inhibitor of fresh apple juice when placed to 12h at room temperature, there were 25 kinds of volatile aroma composition, total content of 0.684 μg/mL. As adding inhibitor of fresh apple juice when placed to 12h at room temperature, the number of volatile aroma components in cold rich apple juice will decrease with the increasing of mixing time, content also will decrease with the increase of the storage time. Alcohol as the main aroma components in fresh juice, the types and content have reduced.