Sensory and microbiological evaluation of probiotic yoghurt made with different types of probiotic cultures starter Lactobacillus acidophilus LA-5® and Bifidobacterium animalis subsp. lactis BB-12®

The incorporation of probiotic bacteria into yoghurt is believed could increase its health benefits such as improving intestinal health, reducing the risk of type 2 diabetes mellitus and more. The objective of this study was to evaluate the sensory and microbiological characteristics of probiotic yoghurt (PY) made with 2 types of starter cultures namely direct vat set (DVS) cultures and heirloom (HC) cultures. Lactobacillus acidophilus LA5 ® and Bifidobacterium animalis subsp. lactis (BB-12® ) used in this study were obtained from Chr. Hansen. Conventional yoghurt (CY) was made with Lactobacillus delbrueckii subsp. bulgaricus (Lb) and Streptococcus thermophilus (St). As much as 2% of starter cultures were added into 10% skimmed milk suspension with 10% of sucrose. Lb:St ratio in CY was 1:1, whereas Lb:St:LA-5:BB-12 ratio in PY was 1:1:2:2. The mixture was incubated at 38°C for 6-8 hrs. Total lactic acid bacteria and bifidobacteria, as well as pH value, were determined at 0, 1st, 2nd, 3rd, 4th week of storage. The sensory properties of yoghurt were evaluated at the 0ᵗʰ week and the 4ᵗʰ week. The results showed that after 4 weeks of storage at 4°C, the total lactic acid bacteria were slightly decreased ranging from 0.26 log CFU/mL (DVS-PY) to 0.79 log CFU/mL (CY), while total bifidobacteria was slightly decreased from 0.40 to 0.58 log CFU/mL. The pH value of CY was significantly decreased after 4 weeks of storage, while the pH values of DVS-PY and HC-PY were not significantly different. The result from the Triangle test revealed that DVS-PY has similar sensory properties with CY whereas HC-PY has less thickness. In general, the sensory properties of CY and PY were slightly decreased after 4 weeks of storage at 4°C. In conclusion, incorporation of probiotic bacteria in yoghurt with DVS starter culture give better microbiological and sensory properties compared to HC starter culture.