| Grapes are rich in nutrients and the health benefits of table grapes are due to the polyphenols.Grape polyphenols not only play an important role in plant growth,development,insect resistance and UV resistance,but also determine the nutritional quality of grape fruits.Grape polyphenols which have a strong antioxidant capacity exert anti-cancer,anti-aging and cardiovascular protection and other physiological functions.However,the postharvest storage and processing methods in grape fruit may have a significant impact on the functional composition of grapes.In addition,Alzheimer's diseases exert memory impairment and cognitive function,which become a serious threat to human health.Inflammation and oxidative stress damage account for the pathogenesis of Alzheimer's disease.The effect of grape diet intervention on the neuroprotective effect of Alzheimer's disease is not yet clear.It is of great significance to investigate the possible mechanism on the effect of grapes dietary interventions on AD neuroprotection,which is helpful to the development and application of grapes functional foods.In this paper,we carried out related researches on the different methods of grape postharvest storage,different modification methods of grape skin fiber,evaluation of digestion in vitro of grape skin fiber and neuroprotection of grape skin fiber diet on AD.The details of our study are as follows:the effect of different postharvest treatments and storage conditions on basic quality indexes,phenolic compounds and antioxidant ability in grape during storage;the effect of different modification techniques on the physico-chemical properties and functional components of grape skin;combined with the model of gastrointestinal tract digestion in vitro,the changes of phenolic content and antioxidant capacity in different stages of in vitro digestion of grape skin fiber before and after modification;the neuroprotective effect of grape skin fiber dietary intervention on AD mice and its possible mechanism were further studied;This paper provides a theoretical basis for the prevention and intervention of Alzheimer's disease in the future from the long-term dietary intervention and physical processing of modified grape skin.1.Effect of postharvest UV treatment on grape quality and phenolic metabolism of grape skin at room temperature.Effects of different doses?1.8,3.6,7.2 kJ/m2?and types of UV irradiation?UV-B or UV-C?on grape quality,phenolic compounds content,antioxidant capacity and phenolic metabolism biosynthesis genes were studied.1.8 or3.6 kJ/m2 UV-B or UV-C irradiation could effectively maintain the hardness of grape fruit.3.6 kJ/m2 UV-B or UV-C irradiation significantly promoted total phenolics,flavonoids,flavanols and anthocyanins content and improved the antioxidant capacity.Therefore,the best radiation dose of UV was 3.6 kJ/m2 in improving the quality of grape fruits,the phenolic content and antioxidant capacity during storage.In addition,compared with UV-B irradiation,UV-C irradiation significantly increased the content of gallic acid,catechin,quercetin and resveratrol,and increased the expression of PAL,CHS,F3H,LAR,ANS and STS genes.2.Effect of postharvest UV treatment on grape quality and phenolic metabolism of grape at cold temperature.On the basis of the previous observation,the dose of UV-B or UV-C treatment at 3.6 kJ/m2 was selected to further study the phenolic compounds content,the antioxidant capacity,as well as the expression of phenolic biosynthesizing genes.During the whole storage,UV-B or UV-C irradiation had no significant effect on the total soluble solids,titratable acid and pH of grapes.The phenolics content and antioxidant capacity of grape treated with UV-C irradiation were significantly higher than that of the control and UV-B irradiation.At the 14 d of storage,the monomeric phenolics content in grape skin significantly increased by UV-B or UV-C irradiation.In addition,the UV-C irradiation significantly increased the expression of phenolic biosynthetic genes.3.Effect of postharvest exogenous melatonin on grape quality at cold temperature storage.To explore the optimum concentration of melatonin treatment,grape fruit were treated with 0,5,50,100 and 500?mol/L melatonin and then stored at 4°C for 28 d.The results showed that application of melatonin was notably effective in maintaining firmness of grape.Melatonin treatment had no significant effect on TSS,TA and pH.Melatonin treatment significantly reduced the accumulation of hydrogen peroxide?H2O2?and malondialdehyde?MDA?,but increased the total phenolics and flavonoid contents,resulting in the higher antioxidant capacity.4.Effect of different modification process on the physicochemical properties and phenolic compounds content of grape skin fiber.In this paper,the freeze-dried grape skin fiber was used as raw material and modified by superfine grinding?SFG?and high hydrostatic pressure?HHP?technology in order to study the effect of different modification on physicochemical properties,basic components and morphological changes of grape skin fiber.After modification of grape skin fiber,the SDF content significant increased while the IDF content remarkably reduced.The swelling capacity,water holding capacity and oil holding capacity were significantly increased in HHP treated grape skin fiber.The average particle size of grape skin fiber after SFG and HHP treatment were sharply reduced.The structure of SFG treated grape skin fiber are small and uniform.The strong mechanical shear destroyed the porous and reticular structure,and the bulk of the three-dimensional structure of grape pomace becomes small particles.The grape skin fiber treated by the HHP turned to have more lamellar structure.The structure of this sample became more loose and had a large number of holes.The total phenolic content and antioxidant capacity of grape skin fiber modified by the HHP treatment were higher than those modified by the SFG treatment.5.Effect of in vitro digestion on phenolic compounds and antioxidant capacity of HHP treated grape skin fiber.Based on the in vitro digestion model,our research studied the total phenolic,flavonoids,flavanol and anthocyanins content and the antioxidant activity in different stage of HHP treated grape skin fiber.HHP processing increased the total phenolic,flavonoids,flavanol and anthocyanins content.The higher values of antioxidant activity were also observed in the ethanol extracts.Lower values of total phenolic,flavanol and anthocyanins content and higher values of flavonoids in vitro were observed compared with that of the ethanol extracts.The results were associated with the change of pH and the effect of digestive enzyme.The results of DPPH and ABTS showed that the alcohol extract group had the highest antioxidant activity,while the gastric digestion group had the least antioxidant capacity in vitro digestion,which may be related to the higher values of flavonoids in alcohol extract and intestinal digestion.6.Effects of dietary grape supplementation on improving cognitive deficits in APP/PS1 double transgenic mice.To investigate the effect of diet supplemented with HHP treated grape skin fiber on learning and memory,cortical and hippocampal APP processing,inflammatory factors and oxidative stress in APP/PS1 mice.The chronic grape-contained diets altered APP processing by increasing ADAM10 expression and reducing BACE1 and PS1 expression in the hippocampus and cerebral cortex.The levels of TNF-?and IL-1?were remarkably decreased by grape-contained diets.Further,there was a significant enhancement of SOD activities and a substantial reduction of MDA levels in the hippocampus of APP/PS1 mice treated with grape-contained diets.Our findings indicated that grape-contained diets are an effective neuroprotective method for AD therapy,which might be associated with altering APP processing,inhibiting inflammation responses,and enhancing antioxidant capacity.By comparing the improvement effect of grape skin fiber before and after modification,the HHP modified grape skin fiber has some advantages in improving cognitive deficits and reducing the inflammation levels. |
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