Study On The Selection Of Lemon Wine Fermentation Strains And Fermentation Technology

Citrus lemon（Citrus lemon（L）Burm.F.）is a citrus plant of Rutaceae,rich in nutrients.The lemon wine is fermented by lemon juice,which can retain the bioactive components in the lemon,increasing the additional value.However,lemon contains a large amount of citric acid,which makes it difficult for commercial Saccharomyces cerevisiae to ferment,limiting the industrial production of fermented lemon wine.In this study,a strain of Saccharomyces cerevisiae with acid resistance and a strain of non-Saccharomyces strain with acid-decreasing capacity was screened.The fermentation characteristics of Saccharomyces cerevisiae,the acid-reducing ability of non-Saccharomyces,and effect of different inoculation sequences of two yeast strains on the quality of lemon wine were investigated,providing the theoretical reference for the development of fermented lemon wine.The main results are as follows:（1）The S.cerevisiae strain（NM-8）with strong fermentation ability and acid resistance was isolated from the spontaneous fermentation broth of lemon.The physicochemical indicators,antioxidant activity,and volatile flavor of lemon wine fermented by NM-8 were studied.The results showed that the lemon wine fermented with NM-8 contained more sorbitol(0.96 g·L^-1),glycerin(4.44 g·L^-1),ascorbic acid(48.22 mg·L^-1),and total flavonoids(320.72 mg RE·L^-1),which displayed higher DPPH radical scavenging activity（66.3%）.Meanwhile,it showed that the lemon wine fermented with NM-8 had the most variety（78kinds）and the highest content(5150.41μg·L^-1)of flavor compounds,with the most prominent aroma,taste,and acceptability.These results revealed that the screened strain S.cerevisiae NM-8 isolated from lemon showed substantial advantages in the production of lemon wine.（2）The Saturnispora diversa（SD-59）with good acid-reducing ability was isolated from the fruit and orchard soil of lemon.The acid-reducing ability,citric acid tolerance,acid-reducing conditions and carbon source utilization in lemon juice were studied.The results showed that yeast SD-59 can grow in the medium with citric acid as the sole carbon source.Controlling citric acid within the range of 0～80 g·L^-1 could help to exert its acid-consuming performance.When inoculated with 1×10⁶ CFU·m L^-1 strain SD-59 and then cultured at 31℃,200 r·min^-1 for 60 hours,the total acid content of lemon juice decreased by97.9%.At this time,strain SD-59 had an acid-decreasing rate of 100.0%and 95.9%for malic acid and citric acid,respectively.（3）Using acid-decreasing yeast SD-59 and S.cerevisiae NM-8 as fermentation strains,lemon wine was fermented through sequential and simultaneous inoculation to study the effect of different inoculation sequences on the quality characteristics of final lemon wine.By controlling the inoculation ratio of yeast SD-59 to 1×10⁶ CFU·m L^-1 and S.cerevisiae NM-8 to1×10⁷ CFU·m L^-1,the lemon wine fermented by simultaneous inoculation contained higher total phenols(521.97 mg GAE·L^-1),total flavonoids(343.94 mg RE·L^-1),DPPH free radical scavenging activity（70.3%）and hydroxyl free radical scavenging activity（87.8%）,and the total amount of flavor compounds was the highest(17127.16μg·L^-1).The lemon wine obtained by inoculating strain SD-59 for 24 h and then inoculating S.cerevisiae showed a decrease of 29.1%and 2.4%in citric acid and malic acid content,respectively,and there were the most kinds of flavor compounds（77 kinds）,with a total amount of 12966.61μg·L^-1,and had a better sensory evaluation.