Storage stability and in vitro digestion of microencapsulated powder containing fermented noni juice and probiotics

Abstract

Microencapsulation of fermented noni juice (FNJ) with probiotics is a challenge due to the presence of antibacterial compounds, high levels of organic acids as well as the low pH of the juice. This study aimed to fortify FNJ with Lactobacillus plantarum P8 (LP) and Lactobacillus rhamnosus GG (LGG) using freeze drying, by exploring the possibility of retaining high cell survival rates in the dried powders after drying, during storage and with simulated gastrointestinal (SGI) digestion conditions. Two approaches were studied: 1) drying of the FNJ with bacterial cells simultaneously (powder A); and 2) drying of the FNJ and bacterial cells separately followed by grinding and mixing of the powders (powder B). Both approaches gave powders with high viability (≥9 log CFU/g) of microencapsulated LP and LGG. However, comparing both powder samples, the survival rates of LP and LGG in powder B was significantly higher. After a 7 wk storage at 4 °C, both bacterial strains in powder A showed significant reductions in their viabilities compared to in powder B. The SGI results showed significant lower viable cell counts for both bacteria strains in powder A. After SGI, the viability of bacterial cells in powder B was >7 log CFU/g, higher than the recommended minimal viable probiotics cell concentration according to the US FDA. Between the two strains, LP had a higher survival rate in pure FNJ and a better tolerance toward bile salts (1.2%, w/v). This research showed that fortification of FNJ with a suitable Lactobacillus could be achieved using freeze drying microencapsulation.