Effect of Gum Producing Lactic Acid Bacteria from Palm Sap on the Quality Attributes of Yoghurt

The effect of gum-producing lactic acid bacteria (GP-LAB) from palm sap and their exopolysaccharides (EPSs) on the quality attributes of yoghurt were investigated. GP-LAB such as Lactobacillus plantarum, Leuconostoc lactis were used in a mono-or mixed –cultures, and their EPS as stabilizing agent for yoghurt production.Yoghurt (Y) formulations (A, Y+commercial starter culture; B, Y+lactobacillus plantarum; C, Y+leuconostoc lactis; D, Y+lactobacillus plantarum and leuconostoc lactis) were produced by reconstitution of whole skimmed milk while reference yoghurt (RY) was obtained from the market and stored at 4oC. Sensory, proximate, textural and rheological analyses of samples were determined. Microbial and physicochemical analysis was carried out every week for four weeks. Formulations RY and D were the most preferred while formulation A, B and C were not significantly different (p ˃ 0.05).  Formulation D had the least moisture (80.64 ± 0.11%), highest ash (2.19 ± 0.01%) and highest protein (6.48 ± 0.04%). Whereas, RY had the least ash, fat, protein and carbohydrate contents as well as the highest moisture (89.85 ± 0.37). RY and sample D (3.10 ± 0.00; 3.50 ± 0.71) had least % whey separation, highest firmness (20.50 ± 0.71; 21.50 ± 0.71) and cohesiveness (22.96 ± 0.07; 23.22 ± 0.05) respectively. In all shear rates, formulation D and RY had the highest and the least apparent viscosities respectively. Total viable count ranged from 1.3 - 3.8 × 107, 3.2 – 4.9 × 107, 2.5 – 5.5 × 107, 2.3 – 5.6 × 107and 1.3- 6.3 × 107cfu/ml on days 1, 7, 14, 21 and 28, respectively. At day 28, formulation D had the highest microbial count (6.3× 107cfu/ml) whereas RY had the least microbial population (1.3 × 107cfu/ml). The pH and titratable acid (TTA) (mg lactic acid/g) ranged (4.19 – 4.66; 0.88 – 1.41). In conclusion, formulation D competed favourably with the reference sample in all parameters determined. The combination of Lactobacillus plantarum and Leuconostoc lactis cultures as well as their gums improved the quality attributes of yoghurt. Practical Applications : Exopolysaccharide obtained from lactobacillus plantarum and leuconostoc lactic from palm sap in this study can find practical applications in food industry as food additive: a stabilizing agent (yoghurt), emulsifying agent (mayonnaise), biothickening agent (yoghurt), gluten replacers in cassava-wheat composite bread. EPS can be locally source for the purpose mentioned above and thus, eliminate dependence on importation foreign food additive.