Production of Unique Naturally Immobilized Starter: A Fractional Factorial Design Approach Towards the Bioprocess Parameters Evaluation

Pure and/or mixed isolated microbial cultures, in the dairy sector known as starters, are widely used in the manufacture of numerous fermented (cultured) milk products as well as in butter and cheese making (Bylund, 1995). The starter is added to the sterilized milk-based fermentation media and allowed to grow under controlled and, if necessary, on-line regulated process conditions. During the fermentation, the pure or diversified microbial community produces organic substances which give the cultured milk products their characteristic organoleptic properties such as acidity (pH), flavour, aroma, colour and odour as well as consistency. According to the basic definition known from the literature, the probiotics are food products and nutritional supplements containing live microorganisms and other components of microbial cells that have an extremely beneficial impact on the citizen’s live and well-being of the host (Lahteenmaki & Ledeboer, 2006; Salminen et al., 1999). Therefore, it is not surprising that during the last few years, there has been a significantly increase in the worldwide sales of cultured products containing probiotic bacteria (Ostlie et al., 2005). One of the dairy cultured products is also kefir (known also as kephir, kiaphur, kefer knapon, kipi and kippi), i.e. unique self-carbonated viscous dairy beverage with small quantities of alcohol and can be made with any kind of animal milk, such as those of cows, goats, sheep, camels and buffalos as well as coconut, rice and soy milk (Abraham & De Antoni, 1999; Farnworth, 1999; Koroleva, 1988; Kwak et al., 1996; Loretan et al., 2003; Otles & Cagandi, 2003). Original kefir contains among others also numerous bioactive ingredients that give its unique health benefits, such as, for instance, strengthening immune system (Vinderola et al., 2005), antitumor activity (Liu et al., 2002), improving intestinal immunity (Thoreux & Schmucker, 2001), antimicrobial activity (Garrote et al., 2000; Rodriguez et al., 2005), regulation of cholesterol metabolism (Liu et al., 2006a), improving anti-allergic resistance (Liu et al., 2006b), improving sugars digestion (Hetzler & Clancy, 2003) and antioxidant activity (Liu et al., 2005). Those kefir’s health properties indicate that kefir may be an important, high quality and price-competitive targeted probiotic product. Several methods for kefir production, which use pure and isolated starters, can be found in the literature (Assadi et al., 2000; Beshkova et al., 2003; Fontan et al., 2006). Nevertheless, the real and original kefir can only be produced using traditional methods of adding kefir