Survivality of Lactobacillus Acidophilus & Bifidobacterium Bifidum and physico chemical properties of fermented ice cream made with cow milk, soybean extract and coconut milk individually and in combination / Fatemeh Aboulfazli

The present study investigated the effects of cow milk (W; control), soybean extract (S), coconut (C) and composite milks (combinations of coconut or cow milks with soybean extract) on the survival of Bifidobacterium bifidum (Bb-12; B) and Lactobacillus acidophilus (La-05; L) in ice cream and also on the physicochemical and organoleptic properties of bio-ice cream, both with and without fermentation step prior to the freezing of ice cream. The total free amino acids increased considerably in the presence of soybean extract or coconut milk compared to ice cream made with 100% cow milk (control). In comparison to cow milk ice cream, the survival of both probiotics in non fermented ice cream increased slightly in the presence of soybean or coconut extracts. The presence of vegetable extracts in ice creams enhanced the microbial metabolic activity (decreased time required for the pH to reduce 5.50 and colony forming unit). The effect of coconut milk on the microbial metabolic activity and colony forming unit was more pronounced than that by soybean extract. The survival of probiotic bacteria in frozen fermented ice creams after 90 days was higher for Bb-12 than for La-05. Ice creams containing coconut milk had a higher Bb-12 and La-05 survival than ice creams containing cow milk whereas the survival of both probiotics increased with increasing soybean extract content in composite milk ice creams. Simulated gastrointestinal studies demonstrated Bb-12 showing greater tolerance than La-05 to acidic (gastric juice; pH = 2.0) and alkaline conditions (small intestinal juice; 0.3% bile). For composite milk ice cream, the survival of Bb-12 and La-05 in both digestive juices was higher in ice creams containing cow milk than in ice creams containing coconut milk. Increasing soybean extract content in ice creams also increased both probiotics survival. All vegetables and composite milk non fermented ice creams showed a slower melting rate than control ice cream. Amongst ice creams with composite milk, those iv containing coconut milk had higher apparent viscosity and fat globule sizes than others. The presence of soybean extract in ice cream made with composite milk increased hysteresis, apparent viscosity and consistency index and decreased the amount of freezable water and the total consumer panelist acceptability. Fermented ice cream made with soybean extract or coconut milk and composite milks showed a slower melting rate than control ice cream. Ice creams containing cow milk had a higher melting rate and lower apparent viscosity than ice creams containing coconut milk, and also those containing La-05 had lower melting rate and higher apparent viscosity than ice creams containing Bb-12. Ice creams without soybean extract had lower apparent viscosity than ice creams containing soybean extract. In conclusion, the replacement of cow milk with vegetable extract markedly improved the physicochemical properties and survival of probiotics. Soybean extract had the strongest influence on increasing the values of the consistency index, apparent viscosity, hysteresis and survival of probiotics under gastric condition whereas coconut milk markedly enhanced the growth of probiotics and their survival during frozen storage.