| Lycium ruthenicum(Murr.),belonging to the genus Lycium of the family Solanaceae,is widely distributed in western China.At present,the development and utilization of L.ruthenicum were very few,mostly for medicinal or drinking by mixing water.The theoretical research mainly involves the chemical components.But the research on the changes of bioactive components,antioxidant capacity and volatile components after fermentation are really few.In this paper.L.ruthenicum.was used as the main raw material to develop a compound beverage fermented by microorganisms.In order to provide a theoretical basis for further improving its resource utilization value.Through the systematic optimization of fermentation process,changes of bioactive components,organic acids,amino acids,volatile components and antioxidant activities during the fermentation were been analyzed.The main conclusions were as follows:1.Using lactic acid bacteria and saccharomyces to ferment the materials as L.ruthenicum.,red dates,and oolong tea.By using the complete renormalized design and the response surface methodology to optimize the fermentation conditions.With the SOD enzyme activity and the number of lactic acid bacteria and saccharomyces as indexes.To analyse the influence of solid-liquid ratio,inoculation volume and fermentation temperature to them.The results showed the optimum fermentation conditions were:solid-liquid ratio 1:5,inoculation volume 4%,fermentation temperature at 35℃.In that case,the result show that the SOD enzyme activity is 423 U/mg,the total number of lactic acid bacteria and saccharomyces is 2.19×109 CFU/mL.2.The changes of bioactive components such as total acid,polysaccharide,anthocyanin,flavonoids and organic acid of the fermented L.ruthenicum Murr.compound beverage were been analyzed.With the extension of fermentation,the total acid content increased from 23.75 g/kg to 49.65 g/kg.PH decreased from 4.63 to 3.79.Anthocyanin content increased from 47.1 mg/L to 124.0 mg/L.And the content of total flavonoids decreased from 116.04 mg/100g to 91.66 mg/100g during the first 4 days in fermentation,then rose to the highest 142.72 mg/100g on day 8.The polysaccharides were consumed and utilized by microorganisms,the content decreased from 7.23g/100g to 4.43g/100g,and stabilized after fermentation for 8-10 days.The organic acids were mainly malic acid,lactic acid,succinic acid,fumaric acid and gallic acid.The total amount of organic acids was significantly increased compared with that before fermentation.3.The changes of hydrolyzed amino acids and free amino acids were analyzed by HPLC.Hydrolyzed amino acids content in unfermented fresh juice was 41.805 mg/mL.In the uninoculated natural fermentation samples,the content decreased to 15.705 mg/mL.After inoculation,increased to 46.415 mg/mL,which was 11.02%higher than that before.The amino acids with the highest content were Asp and Pro,11.470 mg/mL and 6.822 mg/mL respectively,accounting for 24.71%and 14.70%of the total amino acids.At the same time,after inoculation and fermentation,the content of essential amino acids increased to 9.26 mg/mL,which was 9.10%higher than that before.The relative contents of Thr and Val were the highest,MF were 4.178 and 3.973,respectively.AAS values reached 4.484 and 3.688 respectively,which reached the nutritional adequacy standard compared with the amino acid model recommended by WHO/FAO.The main flavorful amino acids were the delicious Asp and Glu,the bitter Arg and the astringent Cys.Compared with the samples of fresh juice and natural fermentation,the fermented beverage had the most ideal amino acid ratio and protein nutritional value.Besides,DPPH free-radical scavenging activity,hydroxyl free-radical scavenging activity,reducing power and total phenol content were used as evaluation indexes to investigate the changes of antioxidant capacity during fermentation.It was found that the antioxidant activity increased gradually.DPPH scavenging rate increased from 62.66%to 92.75%,hydroxyl radical scavenging rate increased from 70.77%to 97.04%,reducing force increased from 1.23 to 2.07,and total phenol content increased from 1.261 g/mL to 2.300 g/mL.The results were 48.02%,37.12%,68.29%and 82.39%higher than that before fermented,respectively.4.The volatile components of the fermented L.ruthenicum Murr.compound beverage were analyzed by GC-MS.A total of 151 compounds were detected.89,84 and 73 substances were detected in the samples of fresh juice,natural and post-inoculation fermentation.In fresh juice,the content of alcohols and esters were 2.39%and 2.77%,respectively,which increased to 71.26%and 16.21%after post-inoculation.The contents of aldehydes,alkenes,ketones,phenols,benzene and other substances in unfermented juice were 7.3%,3.5%,13.46%,0.6%,60.6%and 2.99%.After the inoculation of beneficial bacteria,the inoculation was reduced to 0.16%,0.5%,0.08%,0.13%,1.5%and 0.07%,respectively.And the main flavoring substances in the beverage,such as alcohol,ester and acid,are significantly increased.Toxic and harmful substances and discordant odor are partially or completely degraded,making the aroma in the fermented L.ruthenicum Murr.compound beverage become rich and delightful. |
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