Effect of Lactobacillus acidophilus and Lactobacillus plantarum on the quality of yogurt

Abstract

Abstract. Siddiq HAM, Hamid OIA. 2017. Effect of Lactobacillus acidophilus and Lactobacillus plantarum on the quality of yogurt. Bioteknologi 14: 25-31. The aim of this study was to evaluate the effect of adding different levels of culture starter and storage period to conventional yogurt culture. Eight liters of fresh cow milk were purchased from a dairy farm located at the College of Animal Production Science and Technology, Khartoum Sudan. The milk was pasteurized at 90°C for 30 minutes then cooled to 45°C. The pasteurized milk was then divided into four equal portions. Four treatments were carried out. The first treatment was the control sample, namely yogurt which was from conventional yogurt culture starter. In the second, third and fourth treatments, respectively, 50%, 75% and 100% of culture starter adjunct (Lactobacillus acidophilus and Lactobacillus plantarum) were added. The inoculated milk was incubated in all treatments at 43 °C for three hours. After complete coagulation, the yogurt samples were cooled by refrigeration with a temperature of 4°C. Chemical composition and sensory evaluation were carried out on the yogurt samples in all treatments at intervals of 1, 5 and 10 days. The results indicated that significant variations (P<0.05) were found in the fat %, acidity % and protein % while total solids and the ash % showed no significant difference (P>0.05) due to the culture starter adjunct addition. However, the storage period had significant difference (P<0.05) on the fat, protein, total solids, and acidity while the ash content was not affected by storage period. The sensory characteristics of the yogurt samples were found to be not affected significantly (P>0.05) by the storage period, except the texture and overall acceptability. The addition of starter cultures had significant variations on the color, flavor, texture, taste, and overall acceptability. The results revealed that the treatments with 50% and 75% showed higher sensory scores than others.