Investigating the effect of pH, different concentrations of glutamate acid and salt on production in low-fat probiotic cheese.

BACKGROUND AND OBJECTIVES: Gamma-aminobutyric acid (GABA) is a non-protein amino acid produced by lactic acid bacteria. Among GABA-producing bacteria, lactic acid bacteria have received more attention due to their probiotic nature and properties such as inhibiting pathogenic bacteria, strengthening the immune system, and so on. MATERIALS AND METHODS: Investigation on the effect of three independent variables including pH (4.7, 4.9 and 5.1), glutamic acid (1, 2 and 3 mgg-1) and salt (2, 2.5 and 3%) on GABA production in low fat cheese by probiotic bacteria. RESULTS: By increasing the amount of glutamic acid and decreasing the pH from 5.1 to 4.7, the amount of GABA production in ultra-filtration cheese significantly increased on the 15th and 30th days of production (p≤0.05), while by increasing the amount of salt the production GABA decreased on the 15th and 30th days. Simultaneous optimal conditions to achieve maximum GABA production in cheese on the 15th and 30th production day was respectively 167.7917 mg/kg-1 and 220.125 mg/kg-1 using 3 mg/g glutamic acid, 2% salt at pH 4.7. CONCLUSION: The results showed that by identifying probiotic bacteria with the highest potential for GABA production and optimizing the culture medium, more GABA can be produced in food products and a positive step can be taken to produce pragmatic products and promote consumer health.

The physicochemical, texture hardness and sensorial properties of ultrafiltrated low-fat cheese containinggalactomannan and novagel gum.

BACKGROUND: Today’s demand for low-fat dairy products, especially cheeses with favorable qualitative properties such as high-fat cheese, has increased. The main goals of this research are to optimize the textural hardness properties of ultrafiltrated, low-fat cheese (7–9%), to investigate the possibility of its production with various concentrations of galactomannan and novagel (0.1–0.5%), and to assess the physicochemical, textural hardness and sensorial properties of the produced low-fat cheese in comparison with full-fat cheese. METHODS: The textural hardness of the cheeses was tested by a texture analyzer (Stable micro system TA.XT plus Texture, London, UK) equipped with a load cell of 5 kg. The pH values were measured using the      pH meter and acidity of the cheese samples according to AOAC standard no. 15004 (AOAC, 1995b). The moisture content and dry matter were measured according to AOAC standard number 920.124 (AOAC, 1995a) as well. The total protein was measured according to AOAC standard no. 991.20 (AOAC, 2005). The amounts of salt and ash were measured according to AOAC (1995a) standard no. 945.46 (AOAC, 1995b), respectively. RESULTS: The results show that the textural hardness properties and sensorial properties of the cheese treatment containing 9% fat, 0.5% galactomannan, and 0.3% novagel are very similar to selected control samples. Meanwhile, optimization of the textural properties of low-fat cheeses via the response-surface method shows that the treatment containing 9% fat, 0.32% novagel and 0.5% galactomannan fulfills the desirable properties of a full-fat cheese up to 100% desirability. CONCLUSIONS: The results of this research also show that by using galactomannan and novagel in the formulation of low-fat cheese, it can be produced with favorable texture textural hardness and sensorial properties close to full-fat cheese.

Optimization of gamma-aminobutyric acid production by probiotic bacteria through response surface methodology.

BACKGROUND AND OBJECTIVES: Gamma-aminobutyric acid (GABA) is a non-protein four-carbon amino acid that has many physiological properties, including reducing blood pressure, accelerating protein synthesis in the brain, and treatment of insomnia and depression. This amino acid is produced by a number of lactic acid bacteria, fungi and yeasts. The objective of the present study was to identify probiotic bacteria with the maximum ability to generate GABA and optimize the bacterial culture conditions having the highest potential for GABA production. MATERIALS AND METHODS: The potential of GABA production by Lactobacillus delbrueckii ssp. bulgaricus, Lactobacillus rhamnosus, Lactobacillus casei, Streptococcus thermophilus, Lactobacillus brevis and Lactococcus lactis ssp. lactis in the culture medium of MRS broth was assessed by High Performance Liquid Chromatography (HPLC). In order to increase the rate of GABA produced by the bacteria having the highest potential for GABA production, the conditions of the culture medium including pH (3.5 to 6.5) "temperature (25 to 45°C), time (12 to 96 h) and glutamic acid (GA) concentration (25 to 650 mmol) were optimized by the Box-Behnken's Response Surface Method (RSM). RESULTS: Lactobacillus brevis had the highest potential of GABA production (5960.8 mg/l). The effect of time and GA concentration was significant on the amount of GABA production. The best conditions of culture medium to achieve the highest amount of GABA production by Lactobacillus brevis (19960 mg/l) were temperature 34.09°C, pH 4.65, GA concentration 650 mmol and time 96 h. CONCLUSION: The results showed that by optimization of the culture medium conditions of probiotic bacteria we can produce more GABA in culture medium.