The discoloration in vegetable processing mainly includ […]
The discoloration in vegetable processing mainly includes browning and chlorophyll changes. Discoloration has a serious impact on the quality and flavor of processed vegetables. The following Vegetable dryer machine manufacturer introduces anti-tarnish measures for vegetable processing:
First, the prevention of browning
Browning in the processing of vegetables can be divided into enzyme browning and non-enzymatic browning.
1. Prevention of enzyme browning.
One is blanching treatment. 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 depending on the variety of vegetables.
The second is to add antioxidants. Sodium erythorbate is a strong reducing agent, which can effectively prevent browning in vegetable processing. The concentration used is generally from 0.05% to 0.15%.
The third is acid treatment. That is, the pH is adjusted to below 6 with citric acid. It can effectively reduce the activity of phenolase. 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 the enzyme browning can also be effectively inhibited.
2. Prevention of non-enzymatic browning. Non-enzymatic browning is common in vegetable processing. Specific measures to prevent non-enzymatic browning include prevention of excessive heat sterilization, preferably 70 ° C ~ 75 ° C, sterilization immediately after 3 minutes ~ 5 minutes; pH control within 6; storage temperature controlled at 10 ° C ~ 15 ° C It is appropriate.
Second, to prevent changes in chlorophyll
Chlorophyll is a natural pigment that is sensitive to light heat, acid, and alkali. Therefore, it is often easy to fade or discolor during processing or storage, which has a great impact on the sensory quality of vegetable products.
1. Alkali treatment. Soak the vegetables in a dilute alkali solution such as 0.01% sodium hydroxide for 20 minutes to 30 minutes. The chlorophyll produces chlorophyllin, phytol, etc., and the color is still bright green. However, this method does not take too long a green time, which can lead to serious loss of nutrients.
2. Replace magnesium in chlorophyll with copper or zinc. Copper acetate or zinc sulfate solution can be used, the concentration is 0.015%, the pH is 9, and the solution is immersed for 30 minutes. The copper and zinc derivatives are formed to remain green for a long time. Copper has higher activity than zinc, and the substitution reaction rate is fast, but the residual amount of copper is limited by the quality standard, while the safety of zinc is high, the effect of green protection is not bad, and the cost is low. It is preferred to use zinc preparation to protect vegetables. Green