Abstract:Cucurbita maxima pumpkin juice was fermented by Lactiplantibacillus plantarum PJ4-2, and theunfermented pumpkin juice was used as the control. The changes in physicochemical indexes, volatile flavor substances and sensory quality of the pumpkin juice after fermentation with L. plantarum PJ 4-2 were analyzed. The results showed that after a 12-h fermentation, the pH value of the pumpkin juice decreased to 4.52, the acidity increased to 10.70 mg/g, and the content of organic acid increased to 11.64 mg/g. A total of 40 volatile flavor compounds were identified from the unfermented and fermented pumpkin juices by headspace solid-phase microextraction and gas chromatography-mass spectrometry (HSSPME-GC-MS), including 11 aldehydes, 9 ketones, 11 alcohols, 4 olefins, 1 phenol, 1 ester, 1 acid and 2 other compounds. The concentration of volatile flavor substances increased by 67.60% after fermentation, and L. plantarum PJ 4-2 made an important contribution to the increase of pumpkin juice flavor. The odor activity value (OAV) analysis combined with the partial least squares discriminant analysis (PLS-DA) revealed that 2,3-butanedione (OAV=175.10, VIP=1.51) and 3-hydroxy- 2-butanone (OAV=10.18, VIP=1.40) were the potential characteristic markers for the aroma differences of pumpkin juice before and after fermentation, giving the fermented pumpkin juice a buttery aroma. The results showed that L. plantarum PJ4-2 had a good activity in pumpkin juice, and the resulting fermented pumpkin juice was rich in fruity aroma, had moderate sweetness and sourness, and gained higher overall acceptance, indicating that L. plantarum PJ4-2 was suitable for fermentation of pumpkin juice.
