Exploring The Effect Of Probiotic Fermentation On The Quality Of Kiwifruit Juice Based On Multi-omics

Kiwifruit(Actinidia spp.)is rich in nutrients and has a unique flavor,which is highly favored by consumers.As a climacteric fruit,it is not suitable for long-term storage after the eating-ripe stage and is prone to rotting and deterioration.Thus,developing high-quality deeply processed kiwifruit products is an effective way to solve the decaying of fresh fruit and increase its added value.Probiotic fermentation,as a new food processing technology,can enhance the biological activity of food and endow it with unique flavor through the conversion of nutrients.In this study,‘Ruiyu’ kiwifruit juice was used as the research object,to select the most suitable fermentation strains for kiwifruit juice,clarify the mono-and mixed culture fermentation processes,and further compare the effects of different fermentation strategies on its sensory quality;the effects of different fermentation strategies on nutritional quality and functional characteristics of juice were explored,the dynamic changes of phytochemicals during fermentation were revealed,and the possible metabolic pathways of key metabolites were preliminarily predicted;the quality changes of juice stored at 4℃ were monitored and shelf life predictions were made.The main conclusions are as follows:(1)A quality evaluation model of fermented kiwifruit juice based on fermentation characteristics of strains,sensory quality and functional characteristics of juice was established by principal component analysis.Experiments determined that Lactobacillus brevis was the optimal strain for monoculture fermentation,which exhibited superior fermentation characteristics in the low p H kiwifruit juice substrate;when the composite ratio of L.plantarum and L.brevis was 1:2,the mixed fermentation kiwifruit juice obtained had the best fermentation characteristics and good sensory quality.(2)The sensory quality of mono-and mixed culture fermentation kiwifruit juice were comparatively studied using intelligent sensory and volatile metabolomics technologies.After fermentation,the concentrations of esters,ketones,alcohols and terpenoids in juice increased significantly,while the concentrations of aldehydes decreased significantly.For different fermentation strategies,mixed culture fermentation was superior to monoculture fermentation in terms of sensory quality,and promoted the production of more ketones and alcohols.While the production of esters and terpenoids was more strongly promoted by monoculture fermentation.Additionally,2,5-octanedione and 1-octen-3-ol were the characteristic aroma compounds of mixed fermented kiwifruit juice.(3)The dynamic changes of phytochemicals during the fermentation of kiwifruit juice were comprehensively revealed by plant-widely targeted metabolomics technology.Parallel to bacteria proliferation,a large number of bioactive compounds such as phenols,organic acids,free fatty acids and vitamins were produced by utilizing the existing sugars,acids,amino acids and nucleotides in the juice matrix,and some anti-nutritional factors were reduced,thereby improving the nutritional quality and functional characteristics of juice;luteolin-8-C-arabinoside and vanillic acid were characteristic products of mono-and mixed culture fermentation,respectively;some key metabolic pathways were preliminarily predicted,including the EMP pathway,PK pathway and organic acid metabolism pathway mainly composed of sugars and acids,the ADI pathway used to improve acid tolerance in lactic acid bacteria,and the phenylalanine/tyrosine metabolism pathway dominated by phenolic acids.(4)During the cold storage for 14 d,the juice samples maintained good probiotic activity and stable physicochemical properties and sensory quality;compared to unfermented juice,probiotic fermentation contributed to retaining and maintaining ascorbic acid,total phenols and antioxidant activity in the juice;the preliminary shelf life prediction was conducted based on whether ascorbic acid can be effectively supplemented,the results showed that fermented juice could be stored at 4℃ for 50 days,while unfermented juice could only be stored for 15 days.In summary,kiwifruit juice could be used as a good matrix for probiotic fermentation,and probiotic fermentation could effectively improve the sensory quality,nutritional quality and functional properties of kiwifruit juice.Meanwhile,fermented kiwifruit juice had good storage characteristics and could maintain high nutritional quality for a long time at 4°C.The research results provide a feasible idea for kiwifruit deep processing products and provide a theoretical basis and technical reference for the production and functional development of probiotic fermented kiwifruit juice.