Effects of processing conditions on the quality of kindirmo made from whole cow milk and cow–soymilk mixtures - I

Six production batches (six treatments in each batch) of kindirmo were carried out in this research to study the effects of fermentation times (5h, 12h and 24h), milk type (whole cow milk and cow–soymilk mixture), starter culture type (kindirmo and DVI – Direct Vat Inoculum) and starter culture age (24h and 48h) and volume of inoculum (2% and 3%) on pH, titrable acidity and organoleptic acceptability of kindirmo from whole cow milk and cow–soymilk mixtures. The research design was a 2*3*2*3 with milk type being the main factor while the sub-factors were respectively starter culture type, inoculum volume and fermentation time. Laboratory analyses carried out were pH and titrable acidity while sensory evaluation was a seven-point Hedonic test for taste, colour, sweetness, texture, mouth-feel and general acceptability. There were also ranking tests on the samples. Means, Analyses of Variance (ANOVA) and Duncan Multiple Range Tests were the statistical tools of SPSS (Statistical Package for Social Sciences) used for data analyses. Results showed pH to be 3.70 – 5.70 while titrable acidity was 0.04 – 0.15 both indicating highly fermented to low fermentation. Ranges of scores for sensory parameters were flavour (3.1 – 6.3), colour (3.3 – 6.3), taste (3.1 – 6.1) and sweetness (2.8 – 6.5). Others were texture (2.0 – 6.1), mouth-feel (2.7 – 6.3) and general acceptability (2.9 – 6.5). ANOVA on the entire 36 kindirmo treatments (i.e. all the six batches jointly together) showed that all the processing conditions have significant effects on the titrable acidity, pH and all the sensory attributes of kindirmo (P ≤ 0.05). However, separate ANOVA for each production batch exclusively for each of these factors, showed that significant differences (P ≤ 0.05) occurred among the kindirmo for all the productions (batches) except in 3%-12h production where only pH, titrable acidity, colour, texture and mouth-feel significantly affected kindirmo quality, whereas flavour, taste, sweetness, general acceptability and ranking sensory factors had no significant effect on kindirmo quality (P ≤ 0.05). The highest reduction in pH (3.70) were observed in virtually all kindirmo of 3%-24h production, whereas the least reduction in pH were in kindirmo of treatments CD24 and SD24 for 2%-5h and 12%-5h productions. The titrable acidity values follow the same trend as in pH values. It was also found that 20% substitution of cow milk with soymilk in kindirmo production was quite acceptable by the consumers even by those who have never tasted soymilk in the past. The use of kindirmo as starter culture using the back-slop method is more efficient in fermentation than the use of commercial starter culture. This was most likely due to the fact that inoculation temperature of the starter culture was at room temperature rather than at 42 – 42OC which was the inoculation temperature for commercial starter cultures in yoghurt production. This shows that kindirmo is different from yoghurt and that the LAB present in kindirmo is less thermophilic than the Lactobacillus bulgaricus and Streptococcus thermophilus present in yogurt. Also the starter culture ages of between 24h and 48h had no significant difference (P ≥ 0.05) on kindirmo quality, except for leftover kindirmo of previous day’s productions, deliberate effort should not be made at producing starter culture of more than 24h old as at it is economically unwise.