Study On Pumpkin Pulp Fermented By Lactobacillus

Two kinds of pumpkin pulp prepared from the Miben and Dongsheng pumpkin were fermented by four kinds of lactobacillus strain. The pH value, total acid,reducing sugar and viable count were investigated during the fermentation.Lactobacillus helveticus and Lactobacillus rhamnose were screened out by sensory evaluation as the best strain, which were more suitable for fermentation of pumpkin pulp. The volatile flavor compounds of pumpkin pulp fermented by Lactobacillus helveticus and Lactobacillus rhamnose for 12 h, 24 h, 36 h and 48 h were measured by headspace solid-phase microextraction(HS-SPME) combined with gas chromatography-mass spectrometry(GC-MS) respectively. The main research results were as follows:(1) The effects of different strains on two kinds of pumpkin pulp were studied. It was showed that fermentation rate of Lactobacillus helveticus was superior to other three strains for the fermentation of pumpkin pulp; the number of viable count of Lactobacillus rhamnose was the highest in the all stains, above 109 cfu/mL.(2) Through the sensory evaluation of different lactic acid bacteria fermented pumpkin pulp, it was concluded that Lactobacillus helveticus and Lactobacillus rhamnose were better than Lactobacillus acidophilus and Leuconostoc mesenteroides for fermented pumpkin pulp.(3) The volatile components were studied in two kinds of pumpkin pulp. The two different pumpkin species showed significant differences in volatile organic compounds. The acids were not identified in Dongsheng pumpkin pulp. The aldehydes, esters content in Dongsheng pumpkin pulp were higher than that of Miben pumpkin pulp, but the alcohols, phenols and ketones content were lower than that of Miben pumpkin pulp.(4) The volatile components in two strains fermentation Miben pumpkin pulp were discussed. A total of 86 compounds were identified, mainly consisting of 15 aldehydes, 13 alcohols, 12 ketones, 10 esters, 10 acids, 6 aromatics, 12 alkanes, and24 volatiles were in common in two pumpkin pulps. Ketones were the main components in different fermentation stages. Compared with the pumpkin pulpfermented by Lactobacillus helveticus and Lactobacillus rhamnose, the eight kinds of fermentation pumpkin pulps had similar major aromatic compounds, but showed significant difference in trace amounts.(5) The volatile compounds in two strains fermentation Dongsheng pumpkin pulp were studied. A total of 116 compounds were detected, mainly including of 13 aldehydes, 23 alcohols, 12 ketones, 17 esters, 14 acids, 5 aromatics, 17 alkanes, of which 28 volatiles were in common in pumpkin pulp. The main volatile compounds were aldehydes in Lactobacillus helveticus fermented pumpkin pulp for 12 h, 24 h, and alcohols were the main volatiles in Lactobacillus helveticus fermented pumpkin pulp for 36 h, 48 h. The main volatile compounds were aldehydes, ketones in Lactobacillus rhamnose fermented pumpkin pulp for 12 h, 24 h, and ketones, alcohols were the main volatiles in Lactobacillus rhamnose fermented pumpkin pulp for 36 h, 48 h.