Document Type : Complete scientific research article
Authors
1
MSc student, Department of Food Science and Technology, Faculty of Agriculture, University of Tabriz, Tabriz, Iran
2
Associate Professor, Department of Food Science and Technology, Faculty of Agriculture, University of Tabriz, Tabriz, Iran
3
Professor, Department of Food Science and Technology, Faculty of Agriculture, University of Tabriz, Tabriz, Iran
4
Associate Professor, Department of Food Science and Technology, Ahar Faculty of Agriculture and Natural Resources, University of Tabriz, Tabriz, Iran
Abstract
Background: Gamma-aminobutyric acid (GABA) as a bioactive compound has a wide range of biologica activities. Therefore, functional foods enriched with GABA have been widely considered by consumers. Whey is the most important waste product of the cheese-making industry and is considered a rich culture medium for probiotics. Among the various methods of GABA synthesis, GABA biosynthesis by fermentation using probiotics has been proposed as the simplest and safest method. Therefore, the aim of this study is to improve GABA production by Lactobacillus brevis NCL912 in whey enriched with different concentrations of glutamic acid.
Methods: After preparing the culture medium from whey powder, different concentrations of glutamic acid (0, 250, 500, 1000 mg L-1) were added to it. Then, a suspension of Lactobacillus brevis NCL912 strain (containing 108 CFU/g) was inoculated into the whey samples and placed in an incubator at 37°C, and the antioxidant activity, total phenol, GABA, and bacterial viability were examined at 24, 48, and 72 h.
Results: The results showed that with the passage of time, the antioxidant activity increased, but the total phenol and GABA levels increased up to 48 hours and then decreased up to 72 h .With the increase in the concentration of glutamic acid, the antioxidant activity and GABA levels both increased first and then decreased, but the total phenol level increased. The passage of time and the increase in the concentration of glutamic acid had no effect on survival. Based on the results, the lowest and highest levels of GABA were obtained for samples with concentrations of 0 mg L-1 -24 h (401 ± 1.1 mg L-1) and 1000 mg L-1 -72 h (591.3 ± 2.6 mg L-1). The results of the analysis of variance showed that the time factor had no significant effect on the level of GABA (P <0.05), but with the increase in the amount of glutamic acid, the level of GABA increased significantly (P ≥0.05). As the highest value was observed at a concentration of 1000 mg L-1. Based on the results of analysis of variance and comparison of means, no significant difference was observed in the overall comparison of samples in terms of antioxidant activity, total phenol, GABA, and viability (P < 0.05), but only in the sample treated with a concentration of 0 mg L-1 of glutamic acid after 24 h, the DPPH inhibition and viability were significant (P ≥ 0.05).
Conclusion: The results showed that the use of the respective strain in whey containing different concentrations of glutamic acid led to an increase in the amount of GABA. The samples also had better antioxidant activity, total phenols and shelf life. Therefore, whey can be used to prepare a probiotic fermented drink enriched with this bioactive compound.
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