Effect of lactose hydrolysis on the milk-fermenting properties of Lactobacillus delbrueckii ssp. bulgaricus 2038 and Streptococcus thermophilus 1131
| Autor: | Takefumi Ichimura, Eri Yamamoto, Reiko Watanabe, Katsunori Kimura, Tatsuya Ishida |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Streptococcus thermophilus
Formic acid medicine.medical_treatment Lactose law.invention 03 medical and health sciences Probiotic chemistry.chemical_compound Hydrolysis fluids and secretions Starter Bioreactors law Lactobacillus Genetics medicine Animals Food science 030304 developmental biology Lactase 0303 health sciences Lactobacillus delbrueckii biology Chemistry Probiotics 0402 animal and dairy science food and beverages 04 agricultural and veterinary sciences equipment and supplies biology.organism_classification Yogurt 040201 dairy & animal science Milk Fermentation bacteria Animal Science and Zoology Food Science |
| Zdroj: | Journal of dairy science. 104(2) |
| ISSN: | 1525-3198 |
| Popis: | Yogurt is a well-known nutritious and probiotic food and is traditionally fermented from milk using the symbiotic starter culture of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus. However, yogurt consumption may cause health problems in lactose-intolerant individuals, and the demand for lactose-free yogurt has been increasing. The standard method to prepare lactose-free yogurt is to hydrolyze milk by lactase; however, this process has been reported to influence the fermentation properties of starter strains. This study aimed to investigate the fermentation properties of an industrial starter culture of L. bulgaricus 2038 and S. thermophilus 1131 in lactose-hydrolyzed milk and to examine the metabolic changes induced by glucose utilization. We found that the cell number of L. bulgaricus 2038, exopolysaccharide concentration, and viscosity in the coculture of L. bulgaricus 2038 and S. thermophilus 1131 was significantly increased in lactose-hydrolyzed milk compared with that in unhydrolyzed milk. Although the cell number of S. thermophilus 1131 showed no difference, production of formic acid and reduction of dissolved oxygen were enhanced in lactose-hydrolyzed milk. Further, in lactose-hydrolyzed milk, S. thermophilus 1131 was found to have increased the expression of NADH oxidase, which is responsible for oxygen reduction. These results indicated that glucose utilization promoted S. thermophilus 1131 to rapidly reduce the dissolved oxygen amount and produce a high concentration of formic acid, presumably resulting in the increased cell number of L. bulgaricus 2038 in the coculture. Our study provides basic information on the metabolic changes in starter strains in lactose-hydrolyzed milk, and demonstrates that lactose-free yogurt with increased cell number of L. bulgaricus can be prepared without delay in fermentation and decrease in the cell number of S. thermophilus. |
| Databáze: | OpenAIRE |
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