Probiotic yoghurt with inulin-type fructans of different degrees of polymerization: physicochemical and microbiological characteristics and storage stability

Abstract

The effect of the addition of inulin-type fructans of different degrees of polymerization (DP) on the physicochemical and microbiological characteristics and storage stability (4°C for 28 days) of nonfat probiotic yoghurt was investigated. The yoghurts were prepared using traditional lactic culture (Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus) and Lactobacillus paracasei ssp. paracasei as probiotic. The formulations contained inulin- type fructans of DP: low (P95 oligofructose, DP 5), medium (ST inulin, DP 10) or high (HP inulin, DP 23) in a concentration of 2g 100g of milk-1, meeting the current Brazilian legislation and, thus their claim of functional properties could be utilized; and were compared to a Normal formulation (without inulin-type fructans addition). The addition of inulin-type fructans with different DP did not alter the L*, a* and b* color parameters, the syneresis and the viability of the probiotic culture in yoghurts. Yoghurts with inulin-type fructans of low DP were more acidic (lower pH values and higher values of acidity). The high DP inulin caused a reduction in the firmness of yoghurt. The products contained Lactobacillus paracasei ssp. paracasei at concentrations higher than that recommended to consider them as probiotic foods throughout the storage period. The refrigerated storage resulted in decreased pH and viability of the probiotic culture and increased acidity and syneresis of yoghurt, regardless of the use of inulin-type fructans. It can be concluded that the addition of inulin-type fructans of different DP does not adversely affect the physicochemical and microbiological characteristics of yoghurts and their stability to storage, thus, the selection of the type to be used depend on the purpose of the manufacturer and the intended use.