| Seabuckthorn is a deciduous shrub belonging to the genus acid thorn in the family Elaeagnus.The leaves are rich in nutrients,flavonoids and other functional factors.In 2013,seabuckthorn leaves were listed as a new resource food.Shanxi's wild small-fruit seabuckthorn natural forest area accounts for 70%of the country's wild seabuckthorn forest area,and it is an important collection of characteristic small-fruit seabuckthorn resources.This project conducted a resource survey of seabuckthorn leaves in four important wild seabuckthorn forest areas in Songjiagou,Youyu,Pangquangou and Gujiao,Shanxi.On this basis,the feasibility and key technology of seabuckthorn leaf tea production were studied.The resource survey includes the influence of growing area and picking time on the main chemical components of seabuckthorn leaves,especially the influence of physical and chemical indicators related to tea production,including the follows:1)through the comparative study of the physical and chemical indexes in Songjiagou,Youyu,Pangquangou and Gujiao seabuckthorn leaves in different areas of Shanxi,analyze the influence of the growth environment on the chemical composition of seabuckthorn leaves and the suitability of tea making;2)comparing the chemical composition of Songjiagou seabuckthorn leaves at different picking times from May to October,and the effect of picking time on the chemical composition of seabuckthorn leaves and the suitability of tea making was studied,the optimum time for picking was determined.Sea buckthorn leaves are not traditional tea raw materials.In this paper,key technology of sea buckthorn leaves tea production were studied,including:1)The effect of drying methods on the nutrients and quality of sea buckthorn leaves were studied,and the optimum drying method was determined;2)seabuckthorn probiotic tea were made from leaves through withering,washing,inoculating with yeast or lactic acid bacteria,and then the leaves were fermented.Physical and chemical indexes and sensory quality evaluation were measured.The suitable fermentation strains,fermentation time and fermentation parameters of seabuckthorn leaf probiotic tea were determined.The main research conclusions are as follows:1.18 physical and chemical indicators of natural small-fruit sea-buckthorn leaves were analyzed and compared in four regions,and the results showed that there was no significant differences in water content,ash,dietary fiber content and total antioxidant capacity in different regions.There are significant differences in several indicators related to tea production,including caffeine,water extract,and total free amino acid content between regions.The contents of heavy metals including Pd,Cr,As and Cd are far below the limits of the national standard and meet the safety requirements.Compared with traditional tea,the total dry matter,total free amino acid content,water extract,iron and calcium contents of seabuckthorn leaves are higher,with the average values in the range of 34.19%?42.42%,3.68%?5.39%,31.44%?39.04%,387mg/kg?769mg/kg and 5.03×10~3?12.3×10~3mg/kg,respectively.Meanwhile,the contents of tea polyphenols and manganese are lower,with the average values in the range of11.54%?13.04%and 58.40?70.40mg/kg,respectively.The phenol-ammonia ratio is between1.95 and 3.64,which is generally considered suitable for making green tea.Caffeine content(0.50%-1.04%)is one-tenth to one-fifth of conventional tea,which could be used as a high-quality raw material for low-caffeine tea or matcha products.2.The physical and chemical indexes of seabuckthorn leaves at different picking months from May to October in Songjiagou were analyzed.The results showed that the contents of chemical components of seabuckthorn leaves picked in August were higher.The contents of water,total ash,water-insoluble ash,water-soluble ash,protein,total dietary fiber,water-insoluble diet,water-soluble dietary fiber,extract,tea polyphenols,and flavonoids are61.87%,5.07%,2.50%,and 2.57%,24.41%,41.79%,38.40%,3.38%,37.23%,11.14%,4.45%,respectively.3.The effects of vacuum drying(NZ),microwave drying(NW),blast drying(NG)and natural drying(ZL)drying methods on the physical and chemical indexes and sensory quality of seabuckthorn leaves were studied.Studies have shown that after vacuum drying(NZ)treatment,the free amino acids,total antioxidant capacity and sensory evaluation scores are the highest,reaching 4.16%,456.05?mol/g and 81.91,respectively.Therefore,after comprehensively considering the evaluation of nutrient content and sensory quality,vacuum drying(NZ)can be selected.4.In this study,fresh sea-buckthorn leaves were withered,steamed,twisted and inoculated with different yeasts and lactic acid bacteria,and water extract,polyphenols,flavonoids,free amino acids,total antioxidant capacity and sensory evaluation were used to evaluated to screen suitable probiotic fermentation strains.(1)Three yeasts of Yantai fruit wine yeast(YWY)?Angel wine yeast(YWA)and Highly active dried yeast(YHD)were selected for seabuckthorn leaf fermentation.Results showed that compared with fresh leaves,grassy taste in seabuckthorn leaves after 1 day of yeast fermentation induced and the overall sensory quality of tea soup is improved.For YWY fermentation,the leaves have the best flavor after 2 days of fermentation,with the highest free amino acid content of 2.91%,while the highest total antioxidant capacity of 437?mol/g appeared on the third day of fermentation.(2)Four lactic acid bacteria,Lactobacillus plantarum(LP),Lactobacillus salivarius(LS),Bifidobacterium(A6)and Lactobacillus paracasei(L9)were selected for seabuckthorn leaves fermentation.Results showed that different lactic acid bacteria have different effects on the physical and chemical indicators of seabuckthorn leaves during the fermentation process.Among them,the contents of tea polyphenols,flavonoids and total antioxidant capacity of LP fermentation for 2 days were increased by 1.27 times,1.34 times and 1.27 times respectively.The comprehensive evaluation of the sensory quality of seabuckthorn probiotics tea is 81.6,which is the fermented product of LP for 2 days.(3)GC-MS was used to study the volatile components in seabuckthorn fresh leaves,probiotic fermented tea and seabuckthorn leaf hairs.The results showed that in the seabuckthorn leaf hairs and fermented tea,aromatic compounds increased significantly,which increased from 5 kinds of aromatic compounds in fresh seabuckthorn leaves to 17 kinds and15 kinds.Among them,fermented tea produced 14 kinds of new volatile substances with the aroma of tea.It is speculated that these 14 new volatile components have greatly improved the aroma of fermented tea. |
PDF Full Text Request