The potential of <I>Uapaca kirkiana</I> fruit jam for the delivery of <I>Lactobacillus rhamnosus</I> yoba as a probiotic food

Abstract

Probiotics are important in enhancing food quality, reducing incidences of diarrhoea and promoting good health. A fruit jam is an ideal food to deliver probiotics because it is easy to produce, a good source of sugar, and most rural population consume it. A probiotic jam was developed using an underutilised fruit, U. kirkiana, to benefit the resource-poor population in southern Africa. U. kirkiana fruit is found abundant in most semi-dry rural areas of Zimbabwe. Ripe U. kirkiana fruits were obtained from preferred domesticated trees by households residing in semi-dry rural areas of Zimbabwe. The fruits were pulped by removing seeds, mashing and sieving through an 800 μM sieve. Pectin content of the pulp was determined. A probiotic jam was developed using the formulation 55 % (wt/vol) pulp, 43 % (wt/vol) sugar, 1.5 % (wt/vol) pectin, and 0.5 % (wt/vol) citric acid. The fruit pulp was mixed with sugar in a stainless steel pot and cooked at 110 °C. Citric acid was added and stirred whilst cooking until it reached 55 oBrix. Pectin was added and the jam was continuously stirred until it reached 68 oBrix. The jam was inoculated with 0.25 % L. rhamnosus yoba and left to propagate for 24 hours, while bacterial growth was monitored. The physicochemical and functional properties (pH, total soluble solids, sugars, total titratable acidity, iron content, zinc content, and vitamin C), and L. rhamnosus yoba viability in the probiotic jam was analysed. The probiotic jam had vitamin C, total titratable acidity, total soluble solids, and moisture content of 0.34 ±0.02 mg /100 g FW, 2.2 ± 0.11 g / L FW, 68.5 ± 0.2 % FW, and 34.8 ± 1.2 % FW, respectively; iron and zinc content of 4.13 ± 0.52 mg /100 g FW and 0.36 ± 0.02 mg /100 g FW, respectively; high  fructose and sucrose content of 12.84 ± 0.21 g /100 g FW and 24.61 ± 0.12 g /100 g FW, respectively; and a total titratable acidity content of 2.2 g / L at day 0 (after production), 2.37 ± 0.01 g / L FW at day 4, and 2.48 ± 0.02 g / L FW at day 7 of storage (25 °C). The probiotic jam had 6.2 ± 0.2 Log CFU / mL viable cells on point of consumption. U. kirkiana fruit jam can potentially deliver live L. rhamnosus yoba cells as a probiotic food.

Key words: Probiotic food, vitamin C, fruit jam, L. rhamnosus yoba, pectin, U. kirkiana fruit, sub-Saharan Africa