Abstract:
Shelflife of currently available yoghurts in the market is relatively low. The present study
was done to develop set yoghurts with extended shelf life by incorporating a novel starter
culture, AiBi 22.50 LOW which contains Streptococcus
salivarius ssp., thermophiles, Lactobacillus delbrueckii ssp., bulgaricus and examined its
quality attributes while gaining a better insight into the relationship between, storage
temperature and the shelflife. A preliminary trial was conducted to determine the suitable
incorporation level of the culture. Yoghurts were prepared using two commercial starter
cultures, Yoflex and AiBi 22.50 LOW followed by incubation at 42°C until pH reached
4.6 and stored at storage temperatures of 4°C and 28°C. Four treatments (0.004%
Yoflex/4°C, 0.004% Yoflex/28°C, 0.005% AiBi/4°C and 0.005% AiBi/28°C) were
evaluated for pH, titratable acidity, texture profile, microbial count and keeping quality at
7 days interval for 42 days. Results further revealed that set yoghurt with the two cultures
was not significantly different in chemical composition. Although, at the initial stage of
storage, set yoghurts stored at 4°C with 0.005% AiBi culture had the highest pH value
(4.61) and the lowest acidity value (0.57). Yoflex & AiBi culture incorporated yoghurt
samples stored at 28°C had the lowest hardness compared with yoghurts stored at
4°C.0.005% AiBi culture sample had shown a decrement of pH values while an
increment of acidity at the period of 4°C storage compared to other treatments. The
hardness of yoghurt increased within the period of storage till 4th week. Further, all
microbial parameters (coliform, yeast & mold) were found to be below the standard levels
of SLS within the storage of six weeks. Set yoghurts having 0.005% AiBi culture which
was stored at 4°C exhibited higher mouth feel. Hence, 0.005% AiBi culture added
yoghurt stored at 4°C can be introduced as extended shelf life yoghurt with adequate
nutritional and sensory properties.
Keywords: Set yoghurt, Shelf life, Starter culture, Texture
