Study On The High Sugar Tolerant Baker's Yeast

In this paper, the fermentation performance traits of baker yeasts, screening of the strains with lower invertase content, as well as the fermentation technology for high sugar tolerant baker yeasts were studied. 12 baker yeasts(BY-1 BY-l2) were used for a group of fermentation performance tests. The results showed that there exhibited a non-negligible probability that the strains, which have less invertase content exhibit good performances in the tests of growing condition, latent time, and fermentation power in the media with high sugar concentration, including very sweet dough; while the strains with good adaptation to maltose show improved fermentation ability in lean dough. Through the tests, the train of BY-6, which had the least invertase content and good adaptation to maltose, was used for mutation with DES. The couple reaction of glucose oxidase- peroxidase-O-Dianisidine kinetic method was used to screen the mutants primarily, and the test of invertase content was used for precise screening. 4 mutants with dropped invertase content were got. Compared with BY-6, the invertase content of the mutant of M26 was dropped by 27.04%, and its maltose adaptation was improved. The 4 mutants all have high fermentation ability with both sweet and lean dough. M26 was used to study the fermentation technology of high sugar tolerant baker yeasts. The effects of raising the pH of fermenting liquor, adopting heat-shock culture, as well as salt feeding culture to the production of commercial high sugar tolerantbaker yeasts was studied. The results showed that during the feeding culture period of 16h, it is useful to raise the pH of fermenting liquor to 7.0 at 12th 13th h, adopt salt feeding culture(feeding salt at 20g/l) at 11th,,12th h, and heat-shock culture of 37t at 13th 14th h. Compared with original technology, the commercial baker yeasts thus got have improved fermentation ability with sweet dough.