Novel Insights Into The Roles Of Lactiplantibacillus Plantarum Strains In Promoting The Aroma Quality Of Goji Berry Wine

Goji berry has high nutritional value,and is one of important economic forest resources with medicinal and food properties.Fermented wine is beneficial for extending the shelf life of goji berry and increasing the added value of the commodity.However,the formation mechanism of aroma compounds in fermented goji berry wine was rarely reported,which may help the development of goji berry wine.It has been studied that inoculation with Lactiplantibacillus plantarum strains has the potential to improve the aroma quality of fruit wines.Therefore,this study was conducted to improve the aroma quality of goji berry wine via the involvement of selected Lactiplantibacillus plantarum strains.With the application of sensory science and flavor chemistry,the volatile composition and aroma attributes formed by L.plantarum strains were evaluated.The key candidate genes of L.plantarum strains responsible for the production of volatile phenols were explored by genomics technology.The purpose of this study was to reveal the mechanism of Lactiplantibacillus plantarum strains in improving the aroma quality of goji berry wine,and to promote the high-quality development of goji berry wine industry.The following are main results.In this study,HS-SPME-GC-Orbitrap-MS was used to establish a method for the simultaneous determination of 13 lactones,11 volatile phenols,5 aldehydes and ketones,5 pyrazines and 4 furans in fruit wines.The method was validated in model wine,goji berry wine,blueberry wine and hawthorn wine.The results showed that the obtained limits of detection（LODs）for all target compounds ranged from0.0003-6.30μg/L,while the limits of quantification（LOQs）were between 0.001-21.00μg/L.The relative recoveries of all compounds in the three types of wine were between 80%and 120%and the relative standard deviations for precision were all less than 19.97%.In a word,this method meets the requirements for the quantification of trace aroma compounds existing in fruit wines.The key aroma compounds of goji berry wine were analyzed using LLE-SAFE-AEDA-GC-MS/O and OAV values.The ethyl esters（ethyl cinnamate,ethyl acetate,ethyl 2-methylpropanoate,ethyl 2-methylbutanoate,ethyl 3-methylbutanoate,ethyl hexanoate,ethyl lactate,ethyl octanoate,ethyl decanoate）,esters（isoamyl acetate,isoamyl lactate）,C₁₃-norisoprenoid（β-damascenone andβ-ionone）,volatile phenols（4-ethylguaiacol,eugenol,2,4-di-t-butylphenol）,alcohols（1-octen-3-ol,benzyl alcohol,phenylethyl alcohol and isopentyl alcohol）and other compounds（naphthalene,methionol,2-acetylpyrrole）contributed the main aroma attributes of goji berry wine.Two strains of L.plantarum 6409 and L.plantarum Lpgoji were selected to improve the aroma composition and organoleptic characteristics of goji berry wines.Different combinations of two strains positively influenced the organoleptic characteristics and aroma composition of goji berry wines.Compared to the L.plantarum fermentation-free goji berry wine,the involvement of L.plantarum strains conferred stronger“animal”,“goji berry”,“smoky”,“liquorice”and“yeast”into fermented goji berry wines.The inoculation of L.plantarum significantly reduced the contents of acetic acid by 14-60%.Besides,inoculation of strain L.plantarum 6409 significantly increased the OAV of 4-vinylphenol ranging from 3 to 45,and 4-vinylguaiacol varying from 94 to 239,while inoculation of L.plantarum Lpgoji alone or in combination with L.plantarum 6409 significantly increased the OAV of 4-ethylphenol ranging from30 to 207,4-ethylguaiacol from 1 to 3 4-methylguaiacol from 21 to 39 and produced4-propylguaiacol with OAV 51-109.The whole genomes of two strain L.plantarum 6409 and L.plantarum Lpgoji were sequenced using the second-generation sequencing.The PDC genes,6409GL000468 and LPgoji GL001952,as reported in the literature（lp＿3665）which are responsible for encoding phenolic acid decarboxylase,are found in L.plantarum 6409 and L.plantarum Lpgoji,respectively.The Vpr A genes,6409GL002057 and LPgoji GL002044,as reported in the literature（lp＿3665）which are responsible for encoding vinyl reductase are found in L.plantarum 6409 and L.plantarum Lpgoji,respectively.The Hcr B gene（lp＿1425,reported in literature）responsible for encoding the reduction of hydroxyl cinnamic acid are found in L.plantarum 6409（6409GL002912）and L.plantarum Lpgoji（LPgoji GL000201）.The gene LPgoji GL001648 is only screened in L.plantarum Lpgoji.This gene is presumed to regulate the reduction of vinyl phenols to ethyl phenols in goji berry wines fermented by L.plantarum Lpgoji.In conclusion,a general tool for the detection of trace aroma compounds in fruit wines was established in this study.The major aroma compounds of goji berry wine were identified.Inoculation of L.plantarum greatly improved the plain aroma profiles of goji berry wine due to the production of volatile phenols.A goji wine characterized as stronger“animal”,“goji berry”,“smoky”,“liquorice”and“yeast”was fermented with selected L.plantarum strains.The genes responsible for improving the aroma quality of goji wine were clarified.This current study will be helpful for the screening of appropriative lactic acid bacteria which are able to improve the aroma quality of goji berry wine.Scientifically,it evidences that selection of L.plantarum strains as a novel strategy would confer fermented goji berry wine to have better aroma profiles.