Properties of salted yoghurt (concencrated yoghurt) made from cow's milks and the effects of storage

ABSTRACT MSc THESIS PROPERTIES OF SALTED YOGHURT (CONCENTRATED YOGHURT) MADE FROM COW'S AND GOAT'S MILKS AND THE EFFECTS OF STORAGE DILEK say DEPARTMENT OF FOOD ENGINEERING INSTITUTE OF NATURAL AND APPLIED SCIENCES UNIVERSITY OF ÇUKUROVA Supervisor: Assist. Prof. Dr. Nuray SAHAN Year: 200 1, Pages: 125 Jury : Assist. Prof. Dr. Nuray SAHAN Assist. Prof. Dr. Işıl VAR Assoc. Prof. Dr. Tamer KAYAALP In this study, the properties of Salted yoghurt (concentrated yoghurt) and the effects of types of milk, storage time and temperature and drainage of yoghurts were investigated. The salted yoghurts were made from drained and non-drained yoghurts which were prepared by using cow's and goat's milks. The salted yoghurts were stored at 4 and 20±1°C and the physical, chemical, microbiological and sensory properties were analysed at 0., 1., 2., 3., 4., 5. and 6 months of storage. The results showed that types of milk and draining had an significant effect on the pH, total volatile fatty acids and tyrosine (p<0.05), storage temperature had an effect on the acetaldehyde (p<0.05) and tyrosine (p<0.01) and storage time had an effect on pH (p<0.05), total volatile fatty acids, acetaldehyde and tyrosine (p<0.01) contents of yoghurts. The types of milk and storage temparature had no significant effect on the growth of, total aerob mezofilic bacteria, mould-yeast, spor forming bacteria, psychrotrop and coliform bacteria (p>0.05), the draining had an significant effect on the growth of mould-yeast and psychrotrop bacteria (p<0.05), the storage time had an significant effect on the growth of, total aerob mezofilic bacteria, mould-yeast, spor forming bacteria, psychrotrop and coliform bacteria in the salted yoghurt samples (p<0.01). Escherichia coli was not found in the salted yoghurt samples. The sensory properties of salted yoghurts were significantly affected by the types of milk, draining, storage time and temperature (p<0.01). KeyWords: Salted yoghurt (concentrated yoghurt), Storage temperature, Storage time, Cow's and goat's milk II