Effects of Freeze-Dried Banana and Watermelon Peel Powders on Bile Salt Resistance, Growth Kinetics and Survival of Probiotic Bacteria

Abstract

Fruit peels have potential as prebiotic sources thanks to their bioactive compounds and dietary fiber contents. This study aimed to determine the effects of freeze-dried banana (BPP) and watermelon (WPP) peel powders on bile salt resistance, growth kinetics and survival of Lactobacillus acidophilus and Lactobacillus plantarum . In the presence of 0.5-1% bile salt, L. plantarum counts were 0.52-1.13 log CFU/mL higher in MRS broth added with 5% peel powder than that without peel powder. L. acidophilus population 2.47-2.79 log CFU/mL higher in MRS broth added with 5% peel powder than that without peel powder in the presence of 0.5% bile salt. Both peel powders did not affect the growth kinetics of L. acidophilus in milk. Conversely, growth of L. plantarum was promoted in milk supplemented with peel powders and yielded a shorter generation time (p<0.05). The maximum population density of L. plantarum in milk supplemented with BPP was approximately one log CFU/mL higher than in milk alone (p<0.05). L. acidophilus displayed better survival during storage at 4°C in milk added with peel powders. Therefore, BPP and WPP can be used as functional ingredients in probiotic foods.

Keywords: fruit, peel, probiotic, prebiotic, bile salt, growth