Abstract
Dairy foods like yoghurt are the main types of food matrices supplemented with probiotic bacteria and they have a beneficial health effects among consumers. In this study, to evaluate the physico-chemical parameters and sensory attributers of probiotic added yoghurts using different concentrations (0%, 0.1%, 0.2%, 0.3% and 0.4%) of probiotic (Bifidobacterium spp). The samples were analyzed for physico-chemical, microbiological, and sensorial properties at a week interval during storage of four weeks. The results showed that, the quality parameters such as total solids, ash, fat, reducing sugar, total sugar, pH and titratable acidity did not show any significant difference (P>0.05) for all types of yoghurt at during the first day of storage . Syneresis was high in 0.4% probiotic added yoghurt (40.73±2.05%) and was lower in without probiotic yoghurt (37.70±1.32%). During the storage period, total solids, total sugar, reducing sugar, pH, and titratable acidity were (p < 0.05) varied among the different types of yoghurt sample. At the end of storage 0.4% probiotic added yoghurt showed higher average value of total solids (21.87±1.40%) and titratable acidity (0.67±0.04%), while yoghurt without probiotic showed higher values of reducing sugar (2.17±0.02%), total sugar (10.72±0.21%) and pH (4.38±0.01). At the end of storage, yoghurt without probiotic showed low value of total solids (15.80±1.93%) and yoghurt with 0.1% probiotic showed low value (0.62±0.02%) of titratable acidity yoghurt with 0.4 % probiotic showed low value of reducing sugar, total sugar and pH. During the storage period, dry matter, ash and titratable acidity increased with increasing concentration of probiotic in the yoghurt. Reducing sugar, total sugar and pH decreased with increasing concentration of probiotic. The high numbers of bacterial colony forming unit was showed during second of weeks of storage than fourth week of storage, which is lower than those without probiotic yoghurt. The sensory evaluation of the produced yogurts revealed the superiority of yogurts with 0.3% probiotic was highly preferred by consumers for their taste and overall acceptability comparison with the other types of yogurt. Finally, yogurts with 0.3% probiotic were more suitable for the consumption.
Highlights
Fermented milk products are products that can be produced via fermentation of lactose by lactic acid bacteria
The results showed that acidity tends to increase in all types of yoghurt during storage period
Sensory attributes like taste and overall acceptability were high in 0.3% probiotic added yoghurt while texture, colour and flavor were preferred by yoghurt made from without probiotic yoghurt
Summary
Fermented milk products are products that can be produced via fermentation of lactose by lactic acid bacteria. Fermented dairy products are usually produced by using lactic acid bacteria and yeasts (Ozer and Kirmaci, 2010). Cheeses have been used for incorporation of probiotic microorganisms, but they may offer a number of advantages compared with fermented milks (Minervini et al, 2012). Cheese has higher pH, more solid consistency, and relatively higher fat content compared with fermented milks such as yoghurt (Karimi et al, 2012). Incorporation of probiotics like Bifidobacterium spp is a common practice in yogurt manufacture to improve the beneficial effects to the human health. The objective of present study was to evaluate the effects of addition of probiotics (Bifidobacterium spp) on physico-chemical parameters and sensory attributes of yoghurt during the storage
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