A comparative study of the quality of yoghurt marketed in Southern Sri Lanka by large scale manufacturers and by rural households

Abstract

Yoghurt is an end product of controlled lactic fermentation by thermophillic lactic acid bacteria namely Streptococcus thermophillus and Uactobacillus delbruekki ssp. bulgaricus. It is one of the most popular fermented milk products worldwide and come in a variety of textures, fat content, flavours etc. Apart from the commercial (C) dairies many small scale (SS) yoghurt producers are scattered through out the country and at present, yoghurt production is increasing as one of the major self employment ventures. However, the quality of the yoghurt marketed by different producers is different. Therefore, a study was conducted to compare the quality of yoghurt marketed by commercial dairies and small scale producers in Southern Province of Sri Lanka and to compare it with Sri Lanka Standards. The samples of yoghurts (from 2 batches) marketed by five C and five SS manufacturers were collected from retail shops in Matara District of Sri Lanka. Each time, three yoghurts from-One manufacturer was collected for physico-chemical and microbiological analysis; transported immediately to_the laboratory and kept in the refrigerator. Microbiological quality of the yoghurt samples were tested on the same day for coliforms, yeast and mould counts. Physico-chemical parameters such as pH, titratable acidity, MSNF%, fat% and protein% were also determined. Sensory evaluation was conducted for C and SS yoghurts by 30 panelists using 5 point hedonic scale. Complete Randomized Design was used and data were analyzed using SAS .(Ver. 6.12) and SPSS (Ver. 10.0) computer packages. Mean pH of the C yoghurts was 4.02+0.19 while in SS yoghurts 4.13+0.19 and were not significantly different (p>0.05). Titratable acidity% (C 1.0+0.13, SS 1.0+0.13), MSNF% (C 13.5+1.83, SS14.08+1.1) and fat% (C 3.15+0.09, SS 3.38+0.40) were also had no significant differences (p>0.05) and those values comply with Sri Lanka Standards. Further, CP% (C 3.57+0.0.69, SS 3.15±0.48) showed no significant difference (p>0.05). Coliforms were detected only in SS yoghurts. Yeast (C 0.62+0.03 log cfu/g, SS 3.5+0.37 log cfu/g) and mould (C 0.28+0.06 log cfu/g, SS 2.52+0.34 log cfu/g) counts were significantly higher (p