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 gf-machine  Vegetable dryer machine manufacturers have introduced anti-rust measures for vegetable processing:

One is to prevent browning
Browning in vegetable processing can be divided into enzyme browning and non-enzymatic browning.

1. Prevent enzyme browning.

One is blanching. The blanching temperature of the vegetable material is usually from 95 ° C to 100 ° C, and the blanching time is usually from 1 minute to 3 minutes. The exact time and temperature depend on the type of vegetables.

The second is the addition of antioxidants. Sodium erythorbate is a strong reducing agent that effectively prevents browning in vegetable processing. The concentration used is usually from 0.05% to 0.15%.

The third is acid treatment. That is, the pH was adjusted to below 6 with citric acid. It can effectively reduce the activity of phenolase. The fourth is oxygen isolation. Vacuum treatment of the pretreated raw materials or immersion of the plant raw materials in water or dilute hydrochloric acid for oxygen separation can also effectively inhibit the browning of the enzyme.

2. Prevention of non-enzymatic browning. Non-enzymatic browning is common in vegetable processing. Specific measures to prevent non-enzymatic browning include prevention of overheat sterilization, preferably 70 ° C ~ 75 ° C, 3 minutes ~ 5 minutes immediately after sterilization; pH control within 6; storage temperature controlled at 10 ° C ~ 15 ° C is suitable.

Second, prevent changes in chlorophyll

Chlorophyll is a natural pigment that is sensitive to light, acid and alkali. Therefore, it tends to fade or discolor during processing or storage, which has a great influence on the sensory quality of vegetable products.

Chlorophyll protection:

1. Alkali treatment. The vegetables are soaked in a dilute alkaline solution such as 0.01% sodium hydroxide for 20 minutes to 30 minutes. Chlorophyll produces chlorophyll, chlorophyll, etc., and the color is still bright green. However, this method does not take too long green time, which can lead to serious loss of nutrients.

2. Replace magnesium in chlorophyll with copper or zinc. A copper acetate or zinc sulfate solution can be used at a concentration of 0.015%, a pH of 9, and the solution is immersed for 30 minutes. 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, and the safety of zinc is high, the green protection effect is good, and the cost is low. It is preferred to use a zinc formulation to protect the vegetables. green