1, there are many reasons for fruit juice stratification: the problem of stabilizer collocation; Storage environment, temperature above 40 degrees or low temperature environment, such as ice crystals produced by freezing, will destroy the structural stability of the product; Considering the homogenization effect, if the homogenization effect is poor, it will also be layered; The problem of puree, ensuring the quality of puree, the meat content of puree berries, insoluble fiber; Solubility of turbidity agent, etc.

2. Causes of discoloration: Browning of juice refers to a phenomenon that the color of juice changes during processing and storage. This color change not only affects the appearance and flavor of juice, but also causes the loss of nutrients and even makes food go bad. For example, lysine, an essential amino acid for human body, is easily lost in Maillard reaction, which leads to the decrease of nutritional value of protein. Therefore, it is of great significance to seek the causes and solutions of browning. Browning includes enzymatic browning and non-enzymatic browning. Non-enzymatic browning includes Maillard reaction, phenolic oxidative discoloration, caramelization browning and ascorbic acid oxidative browning.

3. Causes of odor: packaging materials, microorganisms exceeding the standard, incomplete sterilization, etc.

Good problems should be discovered and solved through practice.

References:

1. Li Peng, Peng Hui, Zhang Tianzhen. Study on the effect of different inhibition conditions on the browning of pear juice [J]. Journal of Hebei Agricultural University, 1994,17 (1): 53-55;

2. Xiao Jiajie, Zheng Yaoqiu, Zhang Lifen, et al. Production technology of fruit juice and vegetable juice [M]. Beijing: Light Industry Press,1987.438+099-25;

3. Kou Liping, Liu Xinghua, Xue Huilan. Research status of red Fuji apple pulp browning [J]. Journal of Northwest A&F University, 200 1, 29: L4-146; .

4. Huang Jianwei; Zhang Hong; Properties of Polyphenol Oxidase in Tian Hongxian Apple [Journal Paper]-Food and Machinery 2001(03);

5. Lv Xinquan, Wu 1 Anti-oxidation, anti-browning and stability test of apple puree [J] 1 Food and Machinery, 2002, (4):12131;

6. Fei, Cai Baoyu, Xu Huachen, et al. 1 Effect of citrus juice components on its browning [J] 1 food industry,1999 (2): 810;

7. close, close, etc. 1 reaction mechanism of non-enzymatic browning of fruit juice and its influencing factors [J] 1 grain and oil processing and food machinery, 2002 (9): 46 ~ 4.