The effects of fortifying milk with Cu, Fe and Zn minerals on the production and texture of yoghurt

Author: E. Ocak ^* and Ş. Köse

Received 15 February 2010, accepted 22 April 2010.

Abstract

Minerals and trace elements are essential to the good functioning of the body and they have to be supplied by the food. The present study determined distribution of added Cu, Fe, and Zn to yoghurt. Cu, Fe and Zn solutions in different ratios were added to bovine milk and yoghurt. Yoghurt was drained to remove some whey by traditional cloth bag method. Cu, Fe, and Zn concentrations in strained yoghurt and whey were determined by atomic absorption spectrometry. While Cu, Fe, and Zn additions increased in milk, ratio of Cu remained in strained yoghurt (P<0.01), ratio of Fe remained in strained yoghurt (P<0.05) and whey (P<0.01) and ratio of Zn remained in whey (P<0.01) increased. Cu addition 0.2 mg l^-1 to yoghurt showed significantly (P<0.01) higher firmness and cohesiveness, while the firmness and cohesiveness values for 3.5 mg l^-1 addition of Zn were significantly lower than the other doses and metals (P<0.05) (P<0.01). However, addition of Fe to milk caused a general increase of firmness and cohesiveness of yoghurts. Presence of Cu and Zn in milk had an inhibitory effect on the fermenting activity of yoghurt starter culture. The incubation time was longer in fortifying yoghurt with Cu and Zn than the control yoghurts and the fortifying yoghurt with Fe.

Key words: Yoghurt, Cu, Fe, Zn, strained yoghurt, texture.