Characteristics of yogurt manufactured using reconstituted yogurt cultured milk powder compared to yogurt powder
For the manufacture of commercial yogurt powder the yogurt has to go through drying process which substantially lowers the yogurt culture counts, so the potential health benefits of the yogurt culture bacteria are deminished or lost. Also, upon reconstitution, commercial yogurt powder does not taste like yogurt, it is sour and off flavored. The objective was to enumerate Streptococcus thermophilus and Lactobacillus bulgaricus of reconstituted yogurt cultured milk power and reconstituted commercial yogurt powder up to 8 weeks and to elucidate their physico-chemical and sensory characteristics. Commercial yogurt powder (CYP) was the control and yogurt cultured milk powder (YCMP) was the treatment. Freeze-dried yogurt starter culture (Lactobacillus bulgaricus and Streptococcus thermophilus at ratio 1:1) was added to milk powder at 107 cfu/g upon reconstitution. Microbial and physico-chemical characteristics of the reconstituted CYP and YCMP were analyzed daily for the first week and then weekly for a period of 8 weeks (at 1, 2, 3, 4, 5, 6, 7, 14, 21, 28, 35, 42, 49 and 56 days) after reconstitution. Three replications of each treatment were conducted. Sensory consumer testing of CYP and YCMP upon reconstitution was conducted with 100 consumers of yogurt. Data were analyzed by Proc GLM of Statistical Analysis System. YCMP had 5 log cfu/ml higher counts of Streptococcus thermopilus compared to the control (CYP) at 56 days. Also, Lactobacillus bulgaricuscounts of YCMP at 28 days was 6.55 log cfu/ml and at 56 days was 5.35 log cfu/ml while the CYP at 28 days onwards had no counts. YCMP also had significantly higher apparent viscosity, pH, appearance, sensory color, aroma, taste, thickness, overall liking, consumer acceptability and purchase intent compared to CYP. YCMP had better overall characteristics than CYP.
Keywords: yogurt, powder, reconsituted