Mechanism of the Greening Color Formation of "Laba" Garlic, a Traditional Homemade Chinese Food Product
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- 作者：Bing Bai ; Fang Chen ; Zhengfu Wang ; Xiaojun Liao ; Guanghua Zhao ; and Xiaosong Hu
- 刊名：Journal of Agricultural and Food Chemistry
- 出版年：2005
- 出版时间：September 7, 2005
- 年：2005
- 卷：53
- 期：18
- 页码：7103 - 7107
- 全文大小：84K
- 年卷期：v.53,no.18(September 7, 2005)
- ISSN：1520-5118
文摘
While green discoloration during garlic processing is of a major concern, this greening is desirableand required for the traditional homemade Chinese "Laba" garlic. To obtain insights into the mechanismof color formation, simulation of the greening of "Laba" garlic was carried out in the laboratory bysoaking aged garlic in 5% (v/v, pH 2.33) acetic acid solution. After 2 days, the garlic cloves turnedgreen. Up to 4 days, pigment(s) diffused from garlic cloves to the pickling solution. The solutionexhibits two maximal absorbances at ~440 and ~590 nm, corresponding to yellow and blue species,respectively, the combination of which creates the green coloration. With increasing time from 4 to25 days, the concentration of both yellow and blue species increases at nearly the same rate, whileafter 25 days, the concentration of the yellow species increases faster than that of the blue species.Interestingly, most thiosulfinates (~85%) in garlic cloves were converted within 4 days, suggestingthat thiosulfinate conversion is proportional to the formation of the pigments. Consistent with thisconclusion, alliinase and acetic acid were required for the color formation. UV-vis spectralmeasurements and pH results suggest that the color formation occurs by two kinds of processes:one enzymatic and the other nonenzymatic. Low pH (2.0-3.0) favors nonenzymatic reactions, whilehigh pH (6.0 or above) is conducive to enzymatic reactions. Thus, the ideal pH for the entire processof garlic greening is between 4.0 and 5.0, which is a compromise of the optimal pH of both theenzymatic and nonenzymatic reactions.Keywords: "Laba" garlic; thiosulfinates; greening; color formation; acetic acid; alliinase