超高压前处理提升植物乳杆菌发酵梨汁的风味品质

本研究旨在探究超高压和巴氏杀菌前处理对植物乳杆菌在梨汁中增殖代谢情况以及对发酵梨汁风味品质的影响。对发酵过程中梨汁的活菌数、pH值及总糖总酸含量进行测定，利用静态-顶空固相微萃取（HS-SPME）和气质联用（GC-MS）分析梨汁发酵前后的挥发性风味化合物的变化，并对发酵前后的梨汁进行风味感官评价。相比于热处理，超高压前处理能更好地保持梨汁原有的风味，且杀菌梨汁的刺激性更小。两种前处理方式对发酵梨汁中挥发性风味物质的影响差异显著（p<0.05）,经植物乳杆菌发酵后，超高压前处理梨汁中挥发性醇、酯、烷酮的含量分别增加了36.47%、95.43%、80.00%，挥发性烯烃、醛的含量分别减少了7.56%、27.00%；巴氏杀菌前处理梨汁中挥发性醇、酯、烯烃的含量分别增加了63.83%、25.67%、17.82%，醛的含量减少了4.08%，烷酮从未检出增至0.90 mg/L。相比于巴氏杀菌前处理发酵梨汁，超高压前处理发酵梨汁中挥发性醇、酯和烯烃的含量均更高（p<0.01），而挥发性醛和烷酮的含量均更低（p<0.05），这使得超高压前处理发酵梨汁更具新鲜气息。

Improving the Flavor Quality of Fermented Pear Juice with Lactobacillus plantarum by Ultra-high Pressure Pretreatment

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.