Enzymatic Modification to Stabilize the Fermented Milk Drink, Doogh

Differences in Aroma Metabolite Profile, Microstructure, and Rheological Properties of Fermented Milk Using Different Cultures

Texture and flavour are the key attributes determining sensory quality and are highly affected by starter cultures. A selection of phenotypic strains is needed to create diverse texture and flavour to meet consumers' preferences. In this study, the use of five lactic acid bacteria strains in the production of fermented milk, along with the metabolite profiles, microstructure, and rheological properties of the fermented milk samples, was investigated. Our results showed that Lactobacillus helveticus (LH) and Streptococcus thermophilus (ST) had a stronger acidification during fermentation but resulted in products with a coarser protein network compared to Lactococcus lactis (BL1) and Leuconostoc mesenteroides (CL3). Milk fermented by LH had the highest viscosity and exopolysaccharide concentration, while milk fermented by ST had the highest concentration of diacetyl. Although Leuconostoc pseudomesenteroides (CL3ST) had a minimal acidification capability, it produced high levels of ethyl-derived compounds associated with sweet, fruity, and floral fragrances. The results demonstrated that LH and ST could be used as starter cultures targeting fermented milks with different viscosities, while BL1, CL3, and CL3ST are suitable as adjunct cultures to impact different acidic sharpness and flavour notes.

Production and characterization of synbiotic Doogh, a yogurt-based Iranian drink by gum arabic, ginger extract and B. bifidum

The objective of this study was to determine the effects of using ginger extract and gum arabic as a prebiotic on the viability of Bifidobacterium bifidum and physico chemical properties of Doogh (yogurt drink) during storage at 4 °C for 30 days. The results showed that by increasing the amounts of gum arabic to 0.5%, B. bifidum count increased significantly (P < 0.05), but further increasing of the gum arabic, had no significant effect on B. bifidum count (P > 0.05). By increasing the amounts of gum arabic, the viscosity of the Doogh samples was increased and phase separation was reduced significantly (P < 0.05). The Doogh sample containing 0.25% gum arabic and 0.25% ginger extract had the highest number of probiotic population. Results showed that addition of B. bifidum increased acid development (°D) in Doogh samples during storage. In addition, phase separation in Doogh enriched by gum arabic was slower compared to control sample and the samples containing ginger extract. Doogh samples containing 0.25-1% gum arabic alone showed acceptable stability during storage time at 4 °C. In general, Doogh sample containing 0.25% ginger extract and 0.5% gum arabic gained the highest overall acceptability score in comparison with the other samples.