| Fresh lettuce is popular because its stems and leaves are fresh,tender and refreshing and rich in various nutrients.However,due to its high water content,delicate texture,high respiratory metabolism and other reasons,it is easily affected by high temperature and other external conditions and its own factors,which makes the pickled lettuce not easy to preserve,resulting in a sudden drop in its commodity value and the rapid loss of nutrients.It is an important mechanism to remove the oxidative damage and senescence factor of fruit and vegetable in the fruit and vegetable.Therefore,it is an urgent problem how to control the aging of lettuce,keep the loss of nutrients in its body and prolong the storage period of postharvest storage by using non chemical safety means.In this paper,fresh pickled lettuce was used as the research object to study the effects of glucose and sugar analogue on the antioxidant activity of Postharvest lettuce.The main results were as follows:(1)The effects of 300 m M glucose solution on antioxidative substances(CAR,total phenol,total Huang Tong),antioxidant enzyme activity(SOD,POD,CAT,GR,DNAR)and antioxidant capacity during the storage of Postharvest lettuce were studied.The results showed that compared with the control,glucose treatment increased the content of antioxidants: the content of carotenoids increased by about 43% in second days,and the content of total phenol and total flavonoids increased by about 70% and 31% in the sixth day storage,and the activity of antioxidant enzymes,SOD,GR and DHAR,reached the peak of fourth days,higher than about 84%,88 respectively.% and 7.6%;the activity of POD and CAT increased by 35% and 67% to the sixth days respectively,and the difference was the greatest at this time.The comprehensive comparison of the three test results of antioxidant power(FRAP,ABTS and DPPH)showed that glucose treatment significantly maintained the antioxidant capacity of Postharvest lettuce.(2)The effects of 300 m M glucose solution and 300 m M mannitol solution on antioxidative substances(CAR,total phenol,total Huang Tong),antioxidant enzyme activity(SOD,POD,CAT,GR,DNAR)and antioxidant capacity during the storage of Postharvest lettuce were studied.The results showed that compared with the control,glucose and mannitol treatment increased the content of antioxidants: the content of carotenoids increased by about 22% and 27% in second days,and the total content of total phenol was about 42% and 49% in the sixth day storage,and the content of total flavonoids was increased by 42% and 49%,respectively,and the activity of SOD,GR and DHAR was increased.The fourth days reached the peak value,SOD activity was higher than about 92% and 94%,the activity of GR increased by 66% and 71% respectively,and the activity of DHAR was higher than 43% and 44%,respectively.The activity of POD was about 38%,48% and then up to the peak at second days,respectively,and the activity of CAT rose to the peak of sixth days,and higher than that of the control.97% and 109%,three kinds of determination results of antioxidant capacity(FRAP,ABTS and DPPH)showed that glucose treatment significantly improved the antioxidant capacity of Postharvest lettuce.(3)The effects of 300 m M glucose solution and 300 m M 3-O-methyl glucose solution on the antioxidative substances(CAR,total phenol,total Huang Tong),antioxidant enzyme activity(SOD,POD,CAT,GR,DNAR)and antioxidant capacity during the storage of Postharvest lettuce were investigated.The results showed that compared with the control,glucose treatment increased the content of antioxidants while methyl glucose treatment had no dominant effect.In the fourth day storage,the content of carotenoid content in glucose treated samples was about 25% higher than that of methyl glucose,which was about 34% higher than that of the control.The total phenol content of glucose treated samples was 1.7 times that of methyl glucose in sixth days of storage and 1.9 of the control.The content of total flavonoids was about 48% higher than that of methyl glucose by about 48% and about 31% higher than that of the control;glucose treatment improved the activity of antioxidant enzymes while methyl glucose treatment had no dominant effect.The activity of SOD,GR and DHAR reached the peak in fourth days.The SOD activity of glucose treated samples was 1.8 times that of methyl glucose and the control,and GR activity was about 34% higher than that of methyl glucose.By about 31%,the activity of DHAR was 1.4 times that of methyl glucose and control;the activity of POD was about 43% higher than that of methyl glucose in second days and about 50% higher than that of the control.The activity of CAT in fourth days was about 76% higher than that of methyl glucose and about 73% higher than that of the control.The comprehensive comparison of the three test results of antioxidant power(FRAP,ABTS,DPPH)showed that the glucose treatment was significantly improved the antioxidant capacity of lettuce,and methyl glucose had no significant effect. |
PDF Full Text Request