| China is the major producer of citrus fruit and the main production area of canned citrus.In the processing of canned citrus,strong acid and strong alkali are used to remove the segment membrane,resulting in large amounts of processing water with high COD and high viscosity,which is also rich in potential prebiotics such as pectin and flavonoids,causing serious pollution and waste of functional components after discharge.However,there is a lack of low-cost methods to achieve zero discharge of the processing water and full recovery of functional components.On the other hand,compound prebiotics with plant polysaccharides and polyphenols as main ingredients are becoming the focus of attention,but their synergistic effects are still lacking in research.The natural pectin and flavonoids in the processing water are good resources for the study of compound prebiotics of polysaccharides and polyphenols.In this study,the traditional segment membrane removal process was improved,so that the processing water can be directly consumed after mixing for beverage development.Then,the structure and composition of functional components(pectin and flavonoids)were clarified.Finally,in-vitro fermentation was employed to explore the prebiotic mechanism of pectin and flavonoid as compound prebiotics,providing a research basis for the development and application of personalized compound prebiotics.The main research contents and results are as follows:(1)Using mandarin,orange and Changshan Huyou as raw materials,the traditional HCl–Na OH segment membrane removal process was improved into a new segment membrane removal process of mixed acid(citric acid and HCl)and mixed alkali(Na OH and KOH).The processing water was recycled to enrich beneficial components,and electrolyte beverages were prepared from the processing water.After analyzing the composition,microbiological and sensory properties of beverages,the results showed that the new process could effectively remove the segment membrane of citrus and the drinks made from the processing water met the food safety standards.The second batch of processing water with appropriate viscosity and enriched beneficial components was more suitable for preparing electrolyte beverages.Among the three kinds of citrus,mandarin was the most suitable for the preparation of electrolyte beverages by the new process.The beverages made from it had the highest content of functional ingredients(pectin 0.29%,flavonoids 0.09%),the electrolyte content met the standard and the sensory evaluation score was the highest.In conclusion,the new segment membrane removal process could produce suitable processing water for electrolyte beverage development and realize zero discharge of the processing water and full recovery of functional components.(2)The structure of pectin and the composition of flavonoids in the acid and alkali processing water and corresponding beverages produced by the new segment membrane removal process were analyzed.The results showed that the pectin structure and flavonoid composition of mandarin and orange were more similar,while that of Changshan Huyou was significantly different: The pectin of mandarin and orange had more neutral sugar side chains and larger molecular weight,while Changshan Huyou was the opposite.The flavonoids in mandarin and orange were mainly hesperidin,narirutin and didymin,while those in Changshan Huyou were mainly naringin,neohesperidin and narirutin.In addition,the content and structure of pectin and the content of flavonoids in acid and alkali processing water were significantly different:the content of pectin in the acid processing water was lower,which might be related to the mild conditions of low temperature and organic acid treatment.Pectin from the acid processing water had less neutral sugar side chains,and the molecular weight was smaller but the RMS rotation radius was larger.The degree of esterification of pectin from acid processing water was higher,which might be related to the saponification reaction of methyl ester groups during alkali treatment.The content of flavonoids in the acid processing water was higher than that in the alkali water,which might be due to the extraction sequence of acid before alkali causing most of the flavonoids to be released in the acid processing water.In conclusion,different citrus varieties and acidalkali extraction methods significantly affected the content and structure of pectin and the content and composition of flavonoids.(3)Taking the main functional components(pectin and hesperidin)in beverages made from mandarin processing water as objects,through in vitro fermentation,the differences in the properties of the two when they were singly fermented and when they were compounded in different proportions were studied.Compared with the single fermentation,hesperidin reduced the consumption of pectin by inhibiting the growth of pectin-utilizing bacteria(Bacteroides、Eubacterium＿eligens＿group and Monoglobus)after compounding,while pectin increased the consumption of hesperidin by promoting the growth of hesperidin-utilizing bacteria(Eubacterium＿eligens＿group、Roseburia、Faecalibacterium and Subdoligranulum),and the inhibition/promotion effect was enhanced with the increase of hesperidin/pectin.Different from the fermentation with a single component,the findings of fermentation with both pectin and hesperidin were further analyzed.(1)The growth of beneficial bacteria such as Subdoligranulum、Roseburia and Faecalibacterium were promoted;(2)The growth of harmful bacteria such as Klebsiella、Escherichia-shigella and Lachnoclostridium were inhibited;(3)The abundance of disease-related metabolic pathways was reduced;(4)The production of hesperidin metabolites was increased,showing better bioavailability,higher and more diverse activities.Furthermore,among various proportions,the results of fermentation with equivalent pectin and hesperidin are also presented.(1)The production of short chain fatty acids was the highest;(2)The overall relative abundance of beneficial bacteria was the highest;(3)The overall relative abundance of harmful bacteria was the lowest;(4)The intestinal flora had the highest community richness and diversity.Therefore,the combination of pectin and hesperidin had a better prebiotic effect in vitro,and the effect was best when the two were combined at the ratio of 1:1. |
PDF Full Text Request