Abstract
The study aimed to determine the effect of starter cultures (kefir grains and natural kefir starter culture without grains) on Lacticaseibacillus rhamnosus GG (LGG) survival and on the quality characteristics of kefir. To this end, the viability of probiotic L. rhamnosus GG strain and the rheological properties and quality parameters of kefir beverages were tested during storage over 21 days at 4 °C. The final LGG counts were 7.71 and 7.55 log cfu/mL in natural kefir starter culture and kefir grain, respectively. When prepared with probiotic bacteria, the syneresis values of kefir prepared using natural kefir starter culture was significantly lower (p < 0.05) than that of kefir made using grains. However, the viscosity indices, hysteresis loop, and dynamic moduli were similar between kefir made with natural kefir starter culture and other kefir formulations (p > 0.05). Moreover, all samples showed shear-thinning behavior. The flavor scores for kefir prepared using natural kefir starter culture were significantly higher than for the other samples (p < 0.05), but overall acceptability was similar at the 10-day assessment across both starters (with and without grain) after the addition of probiotic bacteria (p > 0.05). Overall, the results indicate that natural kefir starter culture could be a potential probiotic carrier.
Highlights
Kefir is an acidic-alcoholic fermented dairy beverage with unique attributes such as a slightly sour and yeasty flavor, and a viscous and creamy density
The mean pH values were similar between kefir cultures with and without probiotic strain (p > 0.05) (Figure 2A), in accordance with results reported by Mitra and Ghosh [33], who observed a slight but insignificant decrease in pH values in kefir samples containing Lacticaseibacillus rhamnosus GG (LGG)
PH values of the kefir samples made with natural kefir starter culture and the added probiotic LGG strain were significantly different (p < 0.05)
Summary
Kefir is an acidic-alcoholic fermented dairy beverage with unique attributes such as a slightly sour and yeasty flavor, and a viscous and creamy density. Kefir has potential to carry probiotic bacteria [9]. It was recently shown that lactic acid bacteria (LAB) counts in kefir were higher from kefir grains than commercial kefir starter culture, suggesting that the commercial starter is not capable of promoting optimal LAB survival [10]. Some commercial kefir starter cultures are existent for industrial production, but they often contain limited yeast species [11]. Kefir can be manufactured from natural kefir starter culture, which is initially captured from kefir grains with the same microbial composition. Its use as a starter culture and potential LAB carrier for industrial applications is much easier than kefir grains
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