Cucurbita maxima pumpkin juice was fermented by Lactiplantibacillus plantarum PJ4-2,and the unfermented 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(HS-SPME-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.
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