The influence of added whey proteins concentrate on growth and activity of lactobacilli and streptococci during fermentation and storage of yoghurt and acidophilus milk

U ovom radu istražen je utjecaj dodatka koncentrata proteina sirutke (KPS) u mlijeko (u omjeru 20:80) na rast bakterijskih kultura (jogurtne kulture: Streptococcus salivarius subsp. thermophilus i Lactobacillus delbrueckii subsp. bulgaricus, te kulture za proizvodnju acidofila: Lactobacillus acidophilus) tijekom fermentacije, te na svojstva proizvoda tijekom čuvanja. Dodatkom KPS u mlijeko povećan je udio proteina na prosječno 4,63%, a suhe tvari na prosječno 13,02%. Fermentacija mlijeka do pH-vrijednosti oko 4,6 je dodatkom KPS produžena pri proizvodnji jogurta za prosječno 30 minuta, a pri proizvodnji acidofila za prosječno 44 minute. Istovremeno porast bakterija u proizvodima s KPS bio je veći (jogurta za prosječno 5,84%, a acidofila za prosječno 16,50%). Nisu uočene značajne razlike pri ocjeni senzorskih svojstava između uzoraka fermentiranih napitaka, iako je izmjerena viskoznost fermentiranih napitaka s KPS bila nešto manja, a pH-vrijednost nešto viša.In this work the influence of addition the whey protein concentrate (WPC) in milk (in proportion 20 : 80) on the growth of bacterial culture: (yoghurt culture: Streptococcus salivarius subs. thermophilus and Lactobacillus delbrueckii subs. bulgaricus, and the culture for production of acidophilus milk: Lactobacillus acidophilus) during fermentation, and on characteristics of products during storage, are investigated. By addition of WPC in milk, the quantity of proteins is increased to 4.63%, and total solids to 13.02%. The fermentation of milk to pH-value about 4.6 by addition of WPC is prolonged (at production of yoghurt on average 30 minutes, and at production of acidophilus milk on average 44 minutes). Simultaneously, increase of bacteria number in products with WPC was bigger (in yoghurt on the average 5.84%, and in acidophilus milk on the average 16.50%). The significant differences of sensory properties between fermented milk beverages were not observed although the viscosity of fermented milk beverages with WPC was slightly smaller but pH-value was slightly higher