Fermented Goat Milk and Cow Milk Produced by Different Starters of Lactic Acid Bacteria: Quality Studies

Abstract

Lactic acid bacteria (LAB) is widely used as culture starters in dairy fermentation. The aim of this study was to investigate the quality of fermented goat milk and cow milk, as well as the viability of LAB in the same products. Fermentations were performed with pasteurized goat milk or cow milk added with skim milk (18% of solids) using three separately different starters; yoghurt starter (a combination of Streptococcus thermophilus FNCC-0040 and Lactobacillus bulgaricus FNCC-0041), single starter of Lactobacillus acidophilus FNCC-0029 and Lactobacillus casei FNCC-0051. Parameters observed were pH, acidity, nutritional quality including protein, fat and lactose content and product’s viscosity. Acidity, pH and viability of LAB were also monitored during storage at refrigerated temperature (4 °C) for 28 days. Results showed that the different LAB starters did not affect the pH, acidity, lactose and protein content. Differences on LAB starters affected fat content and viscosity. The highest score of viscosity (30.00 ± 7.02 Pa•s) was observed on products fermented by yoghurt starters, followed by products obtained using starter of L. acidophilus (17.7 ± 11.4) and L. casei (8.62 ± 0.35). Protein content, acidity, pH and viscosity were not significantly different between products obtained from goat milk and cow milk. Fat content in fermented goat milk was higher (5.03% ± 0.62%) than in fermented cow milk (3.52% ± 0.37%), however, lactose content was higher in fermented cow milk (5.16% ± 0.40%) than in fermented goat milk (4.53% ± 0.35%). Total LAB concentration in fermented cow milk during storage was 8.03 ± 0.52 log10 cfu/mL, while in fermented goat milk was 7.81 ± 0.67 log10 cfu/mL. There was a 10.83% decrease in LAB viability in fermented cow milk and 11.40% in fermented goat milk after 28 days of storage. In conclusion, quality of fermented milk is affected by the starters applied, raw milk source and storage period.