The process monitors of probiotic fermented sour cherry juice based on the HS-GC-IMS

In this study, the sour cherry juice was fermented by lactic acid bacteria (L. rhamnosus GG) and the volatile compounds were identified by both GC-IMS (gas chromatography-ion mobility spectrometry) and GC–MS (gas chromatogram-mass spectrum). Total 10 aldehydes,10 ketones, 10 esters, 8 alcohols, 8 acids, and another 6 compounds were identified in the fermented cherry juice. In addition, PCA (principal component analysis) was applied to differentiate various fermented cherry juice. The first two principal components can explain 80% of the total variables, with PC2 67% and PC1 13% respectively. Meanwhile, the variation of lactic acid bacteria number was measured during fermentation. The peak intensity variation of the 4 compounds was significantly correlated with changes of lactic acid bacteria number (P < 0.05), with the highest correlation coefficient of 0.97. The acetoin can be an indicator for monitoring number variation of lactic acid bacteria (L. rhamnosus GG) in fermented cherry juice and this study can provide a novel method of monitoring probiotic fruit juice fermentation.