Improving the Flavor Quality of Fermented Pear Juice with Lactobacillus plantarum by Ultra-high Pressure Pretreatment
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Abstract:
This study aimed to explore the effects of ultra-high pressure pretreatment and pasteurization pretreatment on the proliferation and metabolism of Lactobacillus plantarum in pear juice as well as the flavor quality of fermented pear juice. The number of viable bacteria, pH value, total sugar and total acid content of pear juice during the fermentation process were determined. The changes in the volatile flavor compounds of the pear juice before and after fermentation were examined by static-headspace solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS), then sensory evaluation on the flavor of pear juice was carried out before and after fermentation. Compared with heat treatment, the ultra-high pressure pretreatment could better preserve the original flavor of pear juice and led to less irritation of sterilized pear juice. The effects of the two pretreatment methods on the volatile flavor compounds in fermented pear juice were significantly different (p<0.05). After the fermentation with Lactobacillus plantarum, the contents of volatile alcohols, esters, and alkanones in the fermented pear juice pretreated by ultra-high pressure increased by 36.47%, 95.43% and 80.00%, respectively, while the contents of volatile olefins and aldehydes decreased by 7.56% and 27.00%, respectively. Pasteurization pretreatment made the fermented pear juice having increased contents of volatile alcohols, esters, and olefins (by 63.83%, 25.67% and 17.82%, respectively), a decreased content of aldehydes (by 4.08%), and an increased content of alkanones (from 0 to 0.90 mg/L). Compared with the fermented pear juice pretreated by pasteurization, the fermented pear juice with an ultra-high pressure pretreatment had higher (p<0.01) contents of volatile alcohols, esters and olefins, and lower (p<0.05) contents of volatile aldehydes and alkanones. The ultra-high pressure pretreatment makes the fermented pear juice pretreated fresher.
