Investigation of in vitro antioxidant activities of Kefir and Boza

Traditional fermented products make up a significant portion of food potential particularly in underdeveloped and developing countries. There are more than 2000 fermented food products with a variety of features in the world. They are a significant part of human's diet and represent a large portion of the world's food variety.Production of traditional foods consumed in our country and in the world is carried out through a natural fermentation in which a microflora of bacteria and yeasts is active. It is well-known that lactic acid bacteria effective in natural fermentation have probiotic effects. This kind of fermented food are prepared through a series of processes in which a variety of raw foods kept in certain heat levels turn into more durable new products with the effects of certain microorganism. Traditional Turkish drinks, kefir and boza are examples of this kind of fermented products.Several in vivo studies have demonstrated that kefir and boza are antibacterial and have positive effects on gastrointestinal system due to probiotics they contain. However, studies investigating antioxidative features of these products are very limited.The purpose of this study is to determine the antioxidant capacity of kefir and boza which are traditional fermented products with positive effects on health. For thispurpose, antioxidative features of kefir and boza samples such as reducing power, ß-carotene bleaching test, chelating activity on Fe+2, total antioxidant activity, DPPH radical, ABTS?+ radical, superoxide radical scavenging activity, DMPD?+radical and NO radical scavenging activities were investigated and results were compared to some standard antioxidants (BHA, BHT, ascorbic acid, trolox, ?-tocopherol ve epicatechin). Results retrieved from this study showed that although kefir and boza demonstrated similar characteristics in several parameters, kefir, especially in low concentrations, demonstrated more total antioxidant activity than boza and many other standard antioxidants. On the other hand, nitric oxide radical scanvenging activity in boza was higher than kefir and similar to the standard antioxidants. Also, ß-carotene bleaching test observed in kefir and boza was similar to each other and to BHA used a standard antioxidant in the study.As a result, it is suggested that kefir and boza can be consumed as natural antioxidants due to their antioxidative features. Kefir and boza are important fermented products. Previous studies have shown that particularly kefir consumption strengthens immune system, reduces glucose and lipid levels in blood, balances blood pressure, and prevents pro-carcinogens to convert into carcinogens. Results of this study suggest that preventive effects of kefir and boza on health are closely related to the antioxidative activities they contain.Key words: antioxidant activity, fermented dairy products, functional food, kefir, boza, probiotics.