Li Lei, Hu Dan, Jiang Ying, Chen Fang, Hu Xiaosong, Zhao Guanghua
College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, China.
J Agric Food Chem. 2008 Feb 13;56(3):941-5. doi: 10.1021/jf072470j. Epub 2008 Jan 19.
It was established that storage at low temperature (less than 10 degrees C) was required for garlic greening occurring either during processing or in the course of "Laba" garlic preparation while storage at high temperature (higher than 20 degrees C) inhibited its occurrence. However, the reason for this observation is unclear. To obtain insights into a tie connected between storage temperature and garlic greening, it was detected if the gamma-glutamyl transpeptidase (GGT) activity correlated with garlic greening because the activity of this enzyme is very sensitive to storage temperature. Results showed that garlic puree (which was prepared from fresh garlic) turned green upon addition of GGT but the color of garlic puree remained unchanged when either water or heat-treated GGT (which has no activity due to heat treatment) was used, a result giving a positive answer to the above proposal. Subsequently, to further clarify the relationship between the GGT activity and garlic greening, the GGT activity, the degree of garlic greening, and the concentration of total thiosulfinates in garlic bulbs were determined respectively after the garlic bulbs had been stored at 4 degrees C for up to 59 days followed by storage at 35 degrees C for up to 22 days. It was found that cold storage facilitated the GGT activity whereas warm storage inhibited the activity of this enzyme, just like the effect of storage temperature on greening, indicating that the increase of GGT activity could be a direct factor resulting in garlic greening. Consistent with this conclusion, the concentration of total thiosulfinates (the color developers) in garlic purees likewise exhibited a reversible change by moving garlic bulbs from one low storage temperature to a higher one; namely, it increased with increasing storage time during storage at 4 degrees C while decreasing as storage time increased during storage at 35 degrees C. The present study provided direct evidence that the GGT is involved in garlic greening.
已经确定，在加工过程中或“腊八蒜”制备过程中发生的大蒜绿化需要在低温（低于10摄氏度）下储存，而在高温（高于20摄氏度）下储存会抑制其发生。然而，这一观察结果的原因尚不清楚。为了深入了解储存温度与大蒜绿化之间的联系，检测了γ-谷氨酰转肽酶（GGT）活性是否与大蒜绿化相关，因为这种酶的活性对储存温度非常敏感。结果表明，由新鲜大蒜制备的蒜泥在添加GGT后变绿，但当使用水或热处理的GGT（由于热处理而无活性）时，蒜泥的颜色保持不变，这一结果对上述提议给出了肯定的答案。随后，为了进一步阐明GGT活性与大蒜绿化之间的关系，在大蒜鳞茎在4摄氏度下储存长达59天，然后在35摄氏度下储存长达22天后，分别测定了GGT活性、大蒜绿化程度和大蒜鳞茎中总硫代亚磺酸盐的浓度。发现冷藏促进了GGT活性，而暖藏抑制了这种酶的活性，就像储存温度对绿化的影响一样，表明GGT活性的增加可能是导致大蒜绿化的直接因素。与这一结论一致，将大蒜鳞茎从一个较低的储存温度转移到较高的储存温度时，蒜泥中总硫代亚磺酸盐（呈色剂）的浓度同样呈现出可逆变化；即，在4摄氏度储存期间，它随着储存时间的增加而增加，而在35摄氏度储存期间，随着储存时间的增加而减少。本研究提供了直接证据，证明GGT参与了大蒜绿化。
