| Walnuts are widely grown all over the world,and our country is a big country in walnut cultivation.In-depth research on walnut staminate flower,a walnut by-product,can not only promote the comprehensive utilization of resources and reduce resource waste,but also increase the added value of walnuts and their by-products,extend the walnut processing industry chain,and have significant benefits for increasing farmers’ income and improving agricultural and rural economic development.important meaning.In this research,five walnut varieties mainly cultivated in Hebei Province,the staminate flowers of walnut in the first and bloom period are the research objects.On the basis of comparing the structure and morphology of walnut staminate flowers under different storage conditions,the composition differences of walnut staminate flowers between varieties and two harvest periods were discussed.In addition,in-depth study of the differences between the nutrient components and secondary metabolites of the walnut staminate flowers in the bloom stage treated by vacuum freeze drying,and scientific evaluation of walnut staminate flower in vitro antioxidant capacity and in vivo digestion process.At the same time,it was developed into walnut staminate flower tea and the brewing process was optimized.The main results are as follows:Ⅰ:Effects of pretreatment and storage on walnut staminate flowers after picking.The male flowering period of walnut is only 18 days,so the storage is the key to the utilization of walnut staminate flower.Room temperature,cold storage,blanching and color protector add blanching will lead to rapid browning of walnut staminate flowers.Based on the observation of the microstructure of walnut staminate flowers of stored by freeze-drying and vacuum freeze-drying,it was found that:Stored at-18℃,the tissue structure of walnut staminate flower was broken,the pollen grains were exposed,and the nutrients such as polyphenols and flavonoids in pollen were exposed to the environment,resulting in oxidative browning,which reduced the sensory and nutritional value of walnut staminate flowers.The tissue structure of walnut staminate flower treated by vacuum freeze drying technology is more intact and the browning rate is slow.Therefore,using vacuum freeze-drying technology to process walnut staminate flower is a better way to improve the storage period.Ⅱ:Comparison of the nutrient components and main secondary metabolites of walnut staminate flowers during the first and full bloom periods.In terms of basic nutrients,the contents of ash,fat.protein and cellulose in the full flowering stage were higher than those in the early flowering stage,for example,the ash content in the full flowering stage was higher than that in the early flowering stage(52.91～55.70mg/g).Under the influence of walnut quality,phenological phase and environmental conditions,there were some differences in nutritional components of among walnut staminate flower varieties at early flowering stage and full flowering stage(P<0.05).Different secondary metabolites have different changes in the bloom stage compared with the initial stage.The polyphenols change slightly,ranging from 2.69 to 13.96 mg/g,while the flavonoids change greatly,ranging from 8.34 to 59.06 mg/g,and the polysaccharide content decreases and changes.The range was only 0.08～1.05 mg/g.The content of polysaccharides is reduced,and the variation range is only 0.08～1.05 mg/g,and the content of saponins is significantly increased.The content of saponins in the bloom stage is 1.62 times that of the initial stage.Ⅲ:The contents of nutrient components and main secondary metabolites of walnut staminate flowers in full bloom stage were treated by vacuum freeze-drying.The correlation between amino acids and varieties was determined using the principal component analysis(PCA).Results show that the cellulose,protein,ash,fat and VC contents of walnut staminate flowers are 50.94-65.90 g/100g,19.28-25.12 g/100g,4.83-6.41 g/100g,0.95-2.61 g/100g and 5.21-21.35 mg/100g,respectively.Walnut staminate flowers are rich in minerals and has a potassium content as high as 26.55-37.22 mg/g.The contents of flavonoids and polyphenols in the secondary metabolites of walnut staminate flowers are 85.94-117.98 and 25.01-62.31 mg/g,respectively.Amongst specify,the contents of ellagic acid and juglone,which are recognised to have anticancer activity,are(78.2±21.69)and(63.48±16.34)mg/100g,respectively,and the contents of polysaccharides and saponins are 0.61-1.58 and 6.50-11.85 mg/g,respectively.The PCA shows that amino acids can distinguish the different varieties of walnut staminate flowers.Ⅳ:Comparison of free radical scavenging rate of flavonoid extracts from walnut staminate flowers.Except for the walnut staminate flowers of Lvling,there was little difference in antioxidant capacity in vitro among the other four kinds of walnut staminate flowers.The IC50 values of DPPH free radicals and total reducing power were 0.1 mg/ml and 0.46 mg/ml,respectively,while the IC50 values of hydroxyl radicals of five walnut staminate flowers were significantly different.At the same concentration,the walnut staminate flower of ShangSong 6 had the strongest scavenging ability of DPPH free radicals,and the walnut staminate flower of Liaoning 1 had the strongest scavenging ability and reducing ability of hydroxyl radical.Ⅴ:Effect of digestive juice on scavenging DPPH free radicals by flavonoids from walnut staminate flower.the flavonoid release from walnut staminate flowers gradually increased during the digestion process.Except for the walnut staminate flowers of Lvling,the scavenging capacity of DPPH free radicals is close to 100%after one hour of digestion in the gastric digestion stage,and tends to be stable after one to four hours;while the scavenging rate of DPPH free radicals will decrease in the digestion stage of the intestine.The DPPH free radical scavenging rate of the walnut staminate fl ower of Lvling in the process of gastric digestion is only(81.98±4.04)%,and its performance in the process of intestinal digestion is different from that of the other four types of walnut staminate flowers.The antioxidant capacity increases with the extension of digestion time.Ⅵ:Study on the brewing conditions of walnut staminate flower tea.The primary and secondary factors affecting the nutritional quality of walnut staminate flowers tea are temperature>time>tea-water ratio.The main dissolvable polyphenol content of walnut staminate flowers tea determined by this condition is 42.01 mg/g and the content of flavonoids.It is 68.16 mg/g,and the content of free amino acid is 67.14 mg/g.The error between the theoretical value and the actual value is small.The second mathematical model established by Design-Export software is used for optimization.The results are as follows,The equation obtained by fitting is:Polyphenols(mg/g)=40.75+4.74AA+0.19B+2.06C+0.045AB+0.84AC+1.52BC-2.99A22.60B2-3.90C2 Flavonoids(mg/g)=64.06+8.76A+0.59B+4.32C+0.87AB+2.4AC+2.07BC-3.36A2-4.03B2-7.36C2 Free amino acids(mg/g)=66.78+4.42A-1.51B+2.25C+l.01AB+0.58AC+0.54BC4.25A2-7.41B2-9.7C2Finally,the best brewing conditions obtained through optimization of the test software and verification test are:the temperature is 97℃,the time is 42 min,and the tea-water ratio is 1:100 g/mL. |
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