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Anti-tarnish measures for vegetable processing
The discoloration in vegetable processing mainly includes browning and chlorophyll changes. The discoloration has a serious impact on the quality and flavor of the processed products of the vegetables. First, browning to prevent browning in the processing of vegetables, can be divided into enzyme browning and non-enzymatic browning. 1 Enzyme browning prevention. One is blanching. The blanching temperature of vegetable raw materials is generally 95°C to 100°C, and the blanching time is generally 1 minute to 3 minutes. The specific time and temperature vary according to the variety of vegetables. The second is to add antioxidants. D-sodium erythorbate is a strong reducing agent that can effectively prevent browning in vegetable processing. The use concentration is generally 0.05% to 0.15%. The third is acid treatment. That is, use citric acid to adjust the pH to 6 or less. Can effectively reduce the activity of phenolic enzymes. The fourth is oxygen isolation. The pretreated raw material is subjected to vacuum treatment, or the vegetable raw material is immersed in water or dilute hydrochloric acid for oxygen isolation, and enzyme browning can also be effectively inhibited. 2 Prevention of non-enzymatic browning. Non-enzymatic browning is common in vegetable processing. The specific measures to prevent non-enzymatic browning are: to prevent excessive heat sterilization, suitable for 70 °C ~ 75 °C, cooling immediately after sterilization for 3 minutes to 5 minutes; pH value controlled within 6; storage temperature controlled at 10 °C ~ 15 °C It is appropriate. Second, to prevent changes in chlorophyll Chlorophyll is a natural pigment, is more sensitive to light and heat, acid and alkali. Therefore, it often fades or discolors during processing or storage, which has a great influence on the sensory quality of the finished product of vegetables. Chlorophyll protection: 1 alkali treatment. The vegetables are soaked in a 0.01% solution of dilute alkali such as sodium hydroxide for 20 minutes to 30 minutes. Chlorophyll produces chlorophyll, phytol, etc. The color is still bright green. However, this method does not keep green for a long time and can lead to serious loss of nutrients. 2 Replace the magnesium in chlorophyll with copper or zinc. Can choose to use copper acetate, zinc sulfate solution, the best concentration of 0.015%, pH value of 9, soak for 30 minutes. Produced copper and zinc derivatives can remain green for long periods of time. Copper has higher activity than zinc, and the substitution reaction speed is fast, but the residual amount of copper is limited by quality standards, while the safety of zinc is high, the protection of green is not bad, and the cost is also low. Zinc preparations can be given priority to protect vegetables Green.