Study On The Changes Of The Quality Of Vegetable Pulp Fermented By Lactobacillus During Processing And Storage

With the promotion of modern people's health concepts,people's dietary concepts have changed,they have pursued the“natural,green,nutritious,healthy,and safe”diet concepts.Fruit and vegetable beverages fermented by Lactobacillus are truly pure natural and healthy foods.Their nutritional value and flavor are in line with the development trend of modern beverages and consumer preferences.In recent years,scientific research workers have used lactic acid bacteria to ferment various types of fruits and vegetables and successfully developed some drinks.However,most of these studies are focused on process development and optimization.Research on the nutritional value and functionality of fermented fruits and vegetables is rare.In this paper,carrot,mango,and Sydney are used as the research object to study the physical and chemical indicators and nutritive characteristics of the fermented samples.The stability of the products during storage is analyzed.The specific research contents and conclusions are as follows:?1?The quality effect of lactic acid bacteria fermentation on carrot pulp:During the fermentation,the pH of carrot pulp gradually decreased,the acidity kept increasing,and the soluble solids content did not change significantly;the sucrose content gradually decreased,and the glucose and fructose first increased and then decreased;the change of the oxalic acid content was not obvious;the contents of citric acid,malic acid and acetic acid all showed a downward trend.A large amount of lactic acid was accumulated in the fermentation,and the content of isobutyric acid gradually increased;the total amount of amino acids in the sample after fermentation increased,and the composition of taste-changing amino acids changed;after fermentation,terpenoids were significantly reduced,ketones and esters were formed,and the flavor of carrot pulp was improved.The content of vitamin C in the sample after fermentation decreased slightly,the total amount of?-carotene and carotenoids decreased,the preservation rate was 78.57%and 78.55%;the content of flavonoids and total phenols increased significantly.ABTS+scavenging capacity of fermented pulp slurry was decreased;iron ion reduction ability,DPPH free radical scavenging ability and hydroxyl radical scavenging ability have improved.?2?Changes in the quality of fermented carrot pulp during storage:storage for 6months at normal temperature,the pH and acidity of the sample did not change substantially,the pH value slightly increased?P>0.05?,and the acidity decreased slightly?P>0.05?,soluble solids content has no significant change.During the storage of fermented carrot pulp,the sugar and organic acid content did not fluctuate,at the 6th month,the preservation rate of them remained high,97%and 93.5%,respectively.At the end of the storage,the preservation rate of crude protein reached 95%.The content of vitamin C showed a decreasing trend.The content of vitamin C decreased by 6.44mg/100 g at the 180th day,which was 38.3%lower than the initial storage period.?3?The quality effect of lactic acid bacteria fermentation on mango pulp:The pH value gradually decreased during the fermentation,the acidity kept increasing,and there was no significant change in soluble solids content after fermentation;sucrose,glucose and fructose all had a significant decrease after fermentation?P<0.05?;malic acid,citric acid and acetic acid content gradually decreased with the fermentation,lactic acid bacteria produced a large number of lactic acid,isobutyric acid content increased significantly?P<0.05?;total amino acids did not change significantly?P>0.05?;After the fermentation,the content of terpenes decreased,esters and alkanols increased,and the pungent odor of mango was improved.The vitamin C content decreased by 5.5%after fermentation,and the total amount of beta-carotene and carotenoids decreased by 0.3 mg/100 g and 0.62 mg/100 g respectively.The content of total flavonoids and polyphenols increased by 4.8%and 10.59%respectively after fermentation.The ferric ion-reducing ability of the sample after the fermentation increased by 0.74 mM FeSO₄,and the ABTS⁺-eliminating ability decreased by 0.04mM VE.Both DPPH-scavenging ability and hydroxyl-scavenging ability were improved.?4?The quality changes of fermented mango pulp during storage:The pH of the fermented mango pulp increased slightly after 180 days?P>0.05?,and the acidity decreased slightly?P>0.05?.After storage for 6 months Soluble solids content did not change significantly?P>0.05?.There was little change in sugar and organic acid content during the entire storage period,at the 6th month the preservation rates of the two were still high,which were 96.8%and 91.2%respectively.At the end of storage,the preservation rate of crude protein reached 93%.Vitamin C content showed a decreasing trend,and the content at the 6th month was 35%lower than the initial storage period.?5?The quality effect of lactic acid bacteria fermentation on sydney pulp:During the fermentation of sydney pulp,the pH value gradually decreased,the acidity kept increasing,and there was no significant change in soluble solids content after fermentation?P>0.05?;sucrose,glucose and fructose were consumed as substrates by lactic acid bacteria in the fermentation process;malic acid,citric acid and acetic acid content decreased after fermentation,large amounts of lactic acid were produced,and isobutyric acid content increased significantly?P<0.05?.The species of amino acids increased after the fermentation,the total content did not change significantly?P>0.05?;the volatile components increased significantly compared with that before fermentation;esters,alcohols,acids and ketones increased,and aroma substances were more abundant.The results showed that the content of vitamin C decreased after fermentation,the preservation rate was 88.6%,the total flavonoid content increased by 4.8%,and the content of polyphenols increased by 6.21%after fermentation.The ferric ion-reducing ability of the sample after fermentation increased by 1.38 mM FeSO₄ equivalents,and there was no significant change in ABTS⁺scavenging ability.Both DPPH radical scavenging ability and hydroxyl scavenging ability were enhanced.?6?Changes in the quality of fermented Sydney pulp during storage:the pH value increased slightly?P>0.05?,the acidity decreased slightly?P>0.05?,and the soluble solids content decreased slightly after storage for 180 days.The change is not significant.The sugar and organic acid content of the fermented sydney pulp remained high at the 6th month during storage,which was 97.2%and 89.5%respectively.At the end of the storage,the preservation rate of crude protein reached 95%.The content of vitamin C decreased by 37.1%at the 180th day compared with the initial storage period.