The impact of Kakadu Plum (Terminalia ferdinandiana) fruit powder and its pectic oligosaccharides on the growth, survival and antimicrobial activity of probiotic bacteria in milk

Prebiotics are essential for improving the growth and survival of probiotics in products, which leads to maintaining the balance of the gut microbiome for overall health. Therefore, the aim of this study was to develop a novel source of prebiotic from an Australian native fruit Terminalia ferdinandiana (Kakadu plum [KP]) and its pectic oligosaccharide (POS) extract by studying their prebiotic effect on growth, survival and milk acidification of six probiotic bacteria. Lactococcus lactis 537, Lactobacillus acidophilus ATCC 4356, Lactobacillus plantarum 299v, Lactobacillus rhamnosus GG, Lactobacillus reuteri ATCC 55730 and Lactobacillus casei ATCC 393 were cultured in skim milk containing 1% and 3% of KP, or 1% of POS derived from KP pectin or apple pectin. Based on the results, the stimulation effect of KP and KP POS on bacteria growth and acidification of milk was found to be species-dependent. A higher prebiotic potential was shown by 1% KP for most strains, while 3% KP significantly enhanced the antimicrobial activity of nisin-producing Lc. lactis 537 supernatant against Staphylococcus aureus. KP POS was more effective than KP in assisting probiotic survival during storage over 14 days at 4 °C and maintaining the pH value of milk of 6 or above during fermentation. Analysis of the monosaccharides and uronic acids of POS from KP revealed mostly glucose, fructose, galactose, arabinose and galacturonic acid. The KP and its POS could be classified as novel prebiotics which support improved growth, survival and antimicrobial activity of specific probiotic bacteria, and areas for future research are recommended. [Display omitted] •Kakadu plum (KP) and its POS could be effective prebiotics to enhance the growth, fermentation, survival in skim UHT milk for tested probiotics.•The stimulation effect of KP and KP POS on bacteria growth and acidification of milk was found to be species-dependent.•A higher prebiotic potential was shown by 1% w/v KP powder than by the other substrates.•The higher KP concentrations (3%) exhibited higher antimicrobial activities against the foodborne pathogens.