Proximate composition, acceptability and stability of probiotic dairy yoghurt containing cooking banana/matooke puree and Lactobacillus rhamnosus yoba

Abstract

Cooking bananas/matooke are eaten in the unripe state but quickly ripen leading to postharvest losses. The purpose of this study was to develop fruit-based probiotic dairy yoghurt using ripe matooke and Lactobacillus rhamnosus yoba. Yoghurt mixtures containing varying proportions of matooke (0%, 5%, 7.5% and 10%) were fermented at room temperature for 32 hours. Acidity, pH and counts of Lactobacillus rhamnosus were determined during fermentation and storage (4°C for three weeks). Consumer acceptability was determined at weekly intervals. Lactobacillus rhamnosus counts increased from 7 – 9 log cfu.g-1 after 24 hours of fermentation. Banana accelerated the acidification rate with banana yoghurts attaining pH = 4.4 – 4.5 and acidity of 0.60 – 0.67% in 24 hours. The control took 32 hours to attain a pH = 4.5. Ripe cooking banana introduced a slight banana aroma but did not significantly (p > 0.05) affect consumer acceptability. Yoghurt containing 7.5% banana was most acceptable and contained: 148 kcal 100 g-1, 76.81% moisture, 12.37% carbohydrates, 6.18% protein, 3.35% fat, 0.77% ash and 1.04% calcium. Yoghurt with 7.5% banana was stable at 4°C for 21 days and maintained viable counts above the target of log 6 cfu.g-1 . This study showed that an acceptable fruit based probiotic yoghurt can be produced by adding ripe banana to the yoghurt mix.