evaluation of physicochemical and microbial properties of hazelnut whey-based beverage fermented with kefir grain

the presence of unsaturated fatty acids and phytosterols in hazelnuts and hazelnut products, including hazelnut milk, are useful for health, especially for preventing cardiovascular disease. fermentation with probiotic microorganisms present in kefir grain increases the functional properties of the products. hazelnut milk is nutritious and can be used in drinks in addition to whey. the present study produced a novel kefir-like beverage using hazelnut and whey. the effects of fermentation, type of kefir grain, milk ratio and fermentation temperature on the antioxidant power, acidity, kefiran content, apparent viscosity and microflora composition were evaluated to determine the most appropriate functional and organoleptical properties. results showed that fermentation using kefir grains changed these properties in hazelnut milk; the amount of change increased as the kefir grain content increased. hazelnut milk fermented with 8% kefir grain at 25°c showed the highest functional properties, especially in antioxidant power and probiotic count. although the highest concentration of polysaccharide in the media was observed at 30°c, this temperature has a destructive effect on the kefir grain.