Development of a probiotic beverage using breadfruit flour as a substrate
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The development of non-dairy probiotic beverages has been of great interest in recent years. The main driver for growth of lactose-free food is driven by the increased incidences of lactose intolerant individuals. The aim of this research was to develop a probiotic breadfruit substrate beverage and to examine how microbiological, physicochemical and sensory characteristics of the beverage changes with different fermentation conditions. In the preliminary study, the ability of Lactobacillus plantarum DPC206, Lactobacillus acidophilus and Lactobacillus casei and their mixed stains to grow in a breadfruit substrate media was investigated. Mixed strains of Lactobacillus acidophilus and Lactobacillus plantarum DPC206 yielded satisfactory probiotic value of over 7 log10 CFU/mL after 24 h fermentation with 5% breadfruit flour and 10% sugar. Preliminary results further showed that beverages containing Lactobacillus plantarum DPC206 or Lactobacillus acidophilus and Lactobacillus plantarum DPC206 were positively described in terms of sensory characteristics. However, beverage containing Lactobacillus casei presented undesirable flavour. Based on the results, Lactobacillus acidophilus and Lactobacillus plantarum DPC 206 were selected as starter culture for the optimization of fermented breadfruit substrate beverage. In the optimization of fermented beverage using Lactobacillus acidophilus and Lactobacillus plantarum DPC206, four different levels of breadfruit (2 to 7%), sucrose (5 to 15%), fermentation temperature (30 to 37℃) and inoculum concentration (1 to 3%), were investigated by applying the D-optimal mixture design. The effects of fermentation parameters on cell viability, pH, titratable acidity, sugar concentration and lactic acid in beverages were determined. Results using the D-optimal mixture design showed that sugar, inoculum concentration and proportion of breadfruit flour significantly influenced cell viability. The optimized values based on the contour plots generated were: 7% breadfruit flour, 1% inoculum, and 15% sugar after fermentation at 30℃ for 48 h. CFU of fermented beverage was positively correlated with sugar increase. Interactions between amount of sugar and proportion of breadfruit flour, as well as inoculum and proportion of breadfruit flour were negatively correlated with titratable acidity and lactic acid, respectively. Sensory evaluation was further carried out on six different breadfruit substrate beverages using projective mapping and measuring sensory acceptance. Results showed that the fermented breadfruit substrate beverage was characterized by a pale-yellow appearance, fruity flavour, and sweet and sour taste. The hedonic test was carried out liking of appearance, odour, flavour, aftertaste and overall liking. Liking was not significantly different (p > 0.05) for almost all samples except for the formulation 4, which contained 7% breadfruit, 3% inoculum, and 5% sugar, and were described as bitter and had the least acceptance. The most obvious finding to come out from this research is the development of a novel fermented breadfruit-based beverage with acceptable sensory characteristics and cell viability using a mixture strain of L. acidophilus and L. plantarum DPC 206.