Effects Of Tea Polyphenols On Quality Of Black Garlic And Production Of 5-HMF

Black garlic is a kind of garlic deep processing product made from fresh garlic processed under high temperature and high humidity conditions.Compared with fresh garlic,black garlic is more popular because of its sweet and sour taste,non-pungent taste and significantly increased biological activity.In the processing of black garlic,the Maillard reaction is closely related to the quality of black garlic,but the toxicity and pharmacology of the intermediate product 5-hydroxymethylfurfural（5-HMF）are controversial.Therefore,under the premise of ensuring the quality of black garlic,it is of great significance to study the method to control the accumulation of 5-HMF during the processing to ensure the safety of black garlic.In this study,Epicatechin（EC）,Epigallocatechin-3-gallate（EGCG）,Epigallocatechin（EGC）,and Epicatechin-3-gallate（ECG）were added to garlic paste,respectively.Black garlic was processed in liquid state under high temperature and high humidity conditions to explore its effect on the quality of black garlic and the generation of 5-HMF.On this basis,the effect of tea polyphenols on the quality of black garlic produced at different processing temperatures（70℃,80℃,90℃）,the formation of 5-HMF and its antioxidant activity were further explored.The main findings are as follows:（1）Effects of tea polyphenol treatment on quality and 5-HMF production of liquid processed black garlicAfter adding tea polyphenols to garlic,black garlic is processed in liquid state at 80°C.The content of tea polyphenols decreased with the prolongation of processing time.Compared with the control group,the black garlic added with tea polyphenols showed no significant change in the degree of browning,the content of reducing sugar and total phenols increased,and the content of 5-HMF decreased.Among them,the content of reducing sugar and total phenols in black garlic processed by adding EGCG in liquid state was the highest,and the content of 5-HMF was the lowest,which was reduced by 17% compared with the control group.Therefore,EGCG was used to treat garlic cloves,and the effect of EGCG on the processing quality of black garlic was further explored.（2）Effects of EGCG treatment on quality and 5-HMF production of black garlic processed in solid stateAfter the garlic cloves were treated with 5% EGCG solution,black garlic was processed at different processing temperatures（70℃,80℃,90℃）,and the effect of EGCG treatment on the quality of black garlic was explored.The results showed that EGCG treatment had no significant effect on Browning degree of black garlic.However,EGCG treatment significantly increased the contents of reducing sugar and total phenols,and decreased the accumulation of5-HMF in black garlic.When the temperature was too high（90℃）,black garlic had burnt taste and hard texture,and the content of 5-HMF was much higher than that at 70℃ and 80℃.Compared with 80℃,black garlic treated with EGCG for 24 h and processed at 70℃ for 27 d had higher reducing sugar and total phenolic content,lower 5-HMF content,better taste,and the best sensory quality evaluation.Therefore,the quality of mature black garlic was the best when processed at 70°C for 27 d after EGCG treatment for 24 h.（3）Effects of EGCG on the antioxidant activity of mature black garlicCompared with the blank group,the black garlic processed by EGCG treatment had significantly improved DPPH free radical scavenging ability,superoxide anion free radical scavenging ability and hydroxyl free radical scavenging ability,and the longer the EGCG treatment time was,the better the processed black garlic was.The antioxidant activity of garlic is stronger.When the quality of mature black garlic is the best（processed at 70°C for 27 d）,the black garlic processed after EGCG treatment for 24 h has the strongest antioxidant activity,and its DPPH free radical scavenging ability,superoxide anion free radical scavenging ability and hydroxyl radical scavenging ability The removal ability was 88.72%,81.55% and 80.47%,which were improved by 98.96%,150.54%,and 45.38%,respectively.Therefore,EGCG treatment could significantly enhance the antioxidant activity of mature black garlic.