| In this study,the effect of cut and incubation on the antioxidant ability of kiwifruit(Actinidia chinensis)was investigated.Firstly,the cut and incubation of kiwifruit was carried out to explore the effect on total antioxidant activity,examines the main content of antioxidants and the change of antioxidant enzymes activity of kiwifruit during incubation.Secondly,the kinds and concentrations of color-protecting reagents were selected.Compared the hot air drying,microwave drying and combined drying on the total antioxidant activity and the main antioxidants.Thirdly,kiwifruit slices were optimized by response surface with microwave vacuum drying technology,compared the freeze drying,hot air drying and microwave vacuum drying on sensory quality,physical and chemical quality of the kiwifruit slices.The main results were as follows:1.The Actinidia chinensis was cut into 4 mm thick slices,incubating at 45℃ for 180 min can significantly increase the total antioxidant activity of Actinidia chinensis.Cutting and incubation process can induce O2·-and H2O2 content of Actinidia chinensis,O2·-content began to decline after incubating 60 min,H2O2 content increased with the extension of incubation time.The total phenolics content increased,soluble sugar content rose after falling firstly,AsA content decreased slowly at earlier stage of incubation,increased significantly after 90 min.The GSH content also showed a trend of increasing.SOD activity increased with the extension of incubation time,POD and CAT activity of Actinidia chinensis showed a trend of gradual decline,APX activity showed the peak value at 30 min of incubation,and then began to decline.2.The 1.00%of cysteine,0.50%of CaCl2,0.50%of NaCl and 0.50%of citric acid showed the better inhibitory effects on enzymatic browning of cut kiwifruit for inhibiting peroxidase(POD)and polyphenoloxidase(PPO)activity.The 0.50%of CaCl2 was optimal for keeping higher total antioxidant capacity(T-AOC),as well as total phenolics and ascorbic acid(AsA)content of cut kiwifruit.3.Drying with microwave and microwave-hot air increased T-AOC compared with hot air drying.Microwave dried kiwifruit slices exhibited higher total phenolics content and phenolic acids content,while hot air treatment maintained higher AsA and glutathione(GSH)content,indicating total phenolics played an important role for enhancing antioxidant capacity of microwave dried kiwifruit slices.4.Kiwifruit slices had good expansion effect,while microwave power had the range of the 10～20 W/g,in which microwave power 15 W/g puffing rate was the largest.When vacuum degree had the range of the 70～90 kPa,kiwifruit slices had expansion effect.When vacuum degree was 90 kPa,kiwifruit slices expansion effect was best.Optimized technology condition of kiwifruit slices drying was:microwave power 17 W/g,vacuum degree 89 kPa,in this condition,puffing rate of kiwifruit slices was the largest.5.Freeze drying,microwave vacuum drying and hot air drying were compared.Freeze dried kiwifruit slices could keep good shape and their surface color brightness were the highest.The kiwifruit slices after microwave vacuum drying had puffed tiny bubbles and their surface color brightness were higher than those using hot air drying.Kiwifruit slices after hot air drying had a certain degree of contraction in shape and their surface colors were rather dark.Freeze dried kiwifruit slices maintained the highest antioxidant capacity and the highest content of soluble sugar,Vc and GSH.Antioxidant capacity and GSH content,soluble sugar content of microwave vacuum dried kiwifruit slices were lower than those of freeze dried kiwifruit slices.But total phenol content of microwave vacuum dried kiwifruit slices was higher than that of freeze dried kiwifruit slices.Hot air dried kiwifruit slices antioxidant capacity was the lowest and their antioxidants such as soluble sugar,Vc content were much lower than those of freeze dried kiwifruit slices,but their total phenol content was higher than that of freeze dried kiwifruit slices. |
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