Processing Kishk from Full Fat and Skimmed Yogurt by Traditional Methods and Studying the Effect of These Methods on its Conservation and Organoleptic Properties and Nutritional Value

Einas Al-Mghawesh
General Commission for Scientific Agricultural Research- Department of Food Technology,
Faculty of Agriculture,Damascus University,
2010

Abstract

The aim of this research  is  to  identify the  factors affecting the quality of Syrian Kishik  made from sheep yogurt, and buttermilk, and characterize this product  by:
(i) specifying the optimal conditions for Kishk processing.
(ii) identifying the chemical composition of Kishk (moisture, salinity, acidity, etc.).
(iii) starting from raw materials to final dried product.
(iv) studying the microbial changes in Kishk starting from raw materials (sheep yoghurt,  buttermilk, burghol) including fermentation stage and finally drying Kishk; and specifying the conditions which give this product his identity as a Syrian traditional product.
Fifteen homemade Kishk samples were collected. Chemical and microbiological tests were carried out for these samples.
Seventy-two samples of  Kishk  were made in laboratory  from sheep yoghurt and buttermilk using two different rates of burghol to the fermented medium 1:3 and 1:4 respectively. Three amounts of salt were added 12, 15 and 18 g. Fermentation of these samples lasted for 7 days in which the acidity test and the microbiological analysis were carried out during the first, third, fifth and seventh day of fermentation, then  the samples were left under sunshine to be dried for two different periods 3 and 4 weeks. Chemical and microbiological tests were also conducted for final product, organoleptic tests made by ten panelists, then a chemical and microbiological comparison between the homemade and laboratory-made samples were carried out.
The study showed significant effect of raw materials (yoghurt and buttermilk) and the rate of mixing with burghol on the dry mass, ash, fat, and protein content of the final product.
The 1:4 mix ratio was determined as the typical ratio. Sheep yoghurt was also recommended to be the best medium for manufacturing with 15 g amount of salt. The best result of drying period obtained with samples dried for 3 weeks.
The organoleptic tests showed that samples of high acidity and fat were favorable more than  other  samples.