Abstract
The health benefits offered by probiotic fermented milks can be increased by adding native fruit pulps. Red fruits contain ellagic acid (EA) and ellagitannins, interesting substances due to their powerful antioxidant properties and other beneficial biological activities, such as cardio protective effects, selective growth inhibition of human pathogenic bacteria, a-amylase inhibition of angiotensin I converting enzyme, and proliferative activities against several different cancer cells. This study aimed to improve the physical properties of symbiotic yoghurts through their supplementation with a mixture of red berry pulps: strawberry, raspberry and “pitanga”. The simplex-centroid design was used for mixture modelling. The design included seven batches/trials: three supplemented with each type of fruit pulp, three corresponding to the binary mixtures and one supplemented with the combination of the three pulps. A control experiment was prepared without addition of fruit pulp. Processed milk bases were fermented at 42 °C until pH 4.7 by using a starter culture blend that consisted of Streptococcus thermophilus (TA040), Lactobacillus bulgaricus (LB340) and Lactobacillus acidophilus (LA140). Subsequently, milk base (80 %) was blended with a pulp preparation (20 %) and other ingredients according to the experimental design. Physico- chemical analyses, enumeration of viable bacteria, colour and rheological characteristics of the yoghurts were evaluated 36 h after preparation and 21 days after cold storage. Three regression models were adjusted to the results (linear, quadratic and cubic special). The results showed that the addition of a mixture of red fruit pulps affected pH and counts of probiotic bacteria, which slightly decrease during storage. Addition of the three red berry pulps simultaneously enhanced the colour and rheological properties of probiotic yoghurts when compared to the control. It was possible to estimate the optimum mixture compositions of the three fruit pulps that increase EA contents in probiotic yoghurts.
