Why is garlic soaked in Labaqing?

China traditional food "Laba garlic" will produce green pigment in the production process. Many families in our country have the tradition of making "Laba garlic". In the twelfth lunar month, garlic is peeled, washed, peeled, poured with rice vinegar, sealed in a small jar and opened on New Year's Eve to make "Laba garlic" with pleasant green leaves and delicious garlic flavor. The production process of "Laba garlic" did not see the sun, and the green color produced was not chlorophyll, but garlic green pigment.

Whether it is traditional garlic products, such as Laba garlic, sugar garlic and so on. Or modern garlic products, such as garlic dry powder, garlic slices, garlic juice, garlic paste, garlic essential oil, etc. Garlic will inevitably turn green during processing. In order to control and reasonably apply garlic green pigment products, we must first understand the mechanism of garlic green change.

Through recent research, the research group found that the green pigment of Laba garlic is actually composed of an adult blue pigment and a postpartum yellow pigment. The conversion process of producing pigment is to produce allicin first, and then convert it into allicin, and the time of allicin production is very short, that is, to convert it into allicin. During garlic processing, it has been reported at home and abroad that garlic puree turns green, and the green pigment produced is not the common chlorophyll, which is the same as the traditional food "Laba Garlic" in China.

According to the analysis of substance change, sulfur-containing compounds such as thioaliphatic cysteine sulfoxide and thiopropenyl cysteine sulfoxide in garlic cells generate thiosulfites, propenyl thiosulfites and allyl thiosulfites under the action of garlic enzyme, which are the precursors of garlic pigment substances, and then make garlic green.

Low temperature is the condition to break the dormancy of garlic, activate alliinase and turn green. γ -glutamyl transpeptidase is necessary in the process of pigment formation. The formation of "Laba garlic" green pigment is similar to the onion turning red to some extent. Allyl and allyl sulfur oxide will turn green when they exist at the same time, propylene sulfur oxide exists, and allyl sulfur oxide will turn red when it does not exist.

Alliinase plays a catalytic role in garlic turning green. "Laba garlic" pickled with acetic acid can increase the permeability of cell membrane and make garlic green without destroying cell wall.

Allyl and allyl cysteine sulfoxide become pigment intermediates under the catalysis of alliinase, which further react with basic amino acids such as lysine and arginine with high content in garlic to generate pigment precursors, and finally react with unsaturated compounds in garlic to generate garlic green pigment.

It was also found that the sulfur content of the pigment extract was significantly higher than that of the common garlic extract, indicating that the pigment was a sulfur-containing non-chlorophyll compound, and the antioxidant activities of the two "Laba garlic" pigment extracts were higher than that of the common garlic extract. This shows that the processing of Laba garlic not only optimizes the flavor, but also optimizes the functional activity.

The research group further studied the influence of processing conditions of Laba garlic on green reaction. It was found that the stronger the activity of γ -glutamyl transpeptidase, the stronger the green reaction of garlic. Allicin thiosulfinate is the reaction substrate to produce green pigment. With the gradual increase of garlic green pigment, thiosulfinate gradually decreased. The formation of garlic pigment includes two reaction processes, namely enzymatic reaction process and non-enzymatic reaction process. Low pH (2-4) is suitable for non-enzymatic reaction, while high pH (> 5) is suitable for enzymatic reaction. Therefore, the ideal pH range should be the compromise between enzymatic reaction and non-enzymatic reaction, so the optimum acidity of garlic greening process is pH 5.

The study also found that the active function of green garlic extract is better than that of purified pigment, which indicates that the production of functional food of Laba garlic may have more research and development value than the processing of allicin capsules. However, it is still necessary to analyze the composition and formation mechanism of allicin.

The research group plans to continue to explore the further purification and structural identification of the pigment and the isomerization of allyl cysteine sulfoxide and allyl cysteine sulfoxide in the follow-up research.