EFFECTS OF LACTOSE HYDROLYSIS AND MILK TYPE ON THE QUALITY OF LACTOSE-FREE YOGHURT

Abstract

The purpose of the work was to investigate the influence of different lactose hydrolysis processes, the contribution of the enzyme and the milk type on the characteristics of the obtained lactose-free yogurt. The analysis was performed on non-hydrolyzed yogurt (control sample), the pre-hydrolyzed yogurt (that was hydrolyzed before fermentation), and the co-hydrolyzed yogurt (concurrent addition of β-galactosidase and starter culture). According to the obtained results, at the end of the fermentation time, an advanced hydrolysis degree was reached (over 80%) both for yogurt samples obtained from pre-hydrolyzed milk and obtained by co-hydrolysis. The optimal method from the economic point of view is to obtain yogurt by co-hydrolysis. The sensory quality of the yogurt samples obtained from hydrolyzed milk by co-hydrolysis was characterized by a better flavor than the control sample, for yogurt from both types of milk. This may be due to the availability of a greater amount of glucose for the production of aromatic compounds, a sweeter taste than natural yogurt, with a light caramel flavor, a firm coagulum, a porcelain appearance, without whey removal. Cow's milk yogurt showed higher viscosity values to goat's milk yogurt for both pre-hydrolyzed and co-hydrolyzed milk. Lactose hydrolysis determined the reduction of the syneresis index of the yogurt compared to the control samples. The studies led to the development of lactose-free yogurt with improved sensory and rheological properties recommended for people with lactose intolerance.

Keywords

• co-hydrolysis
• pre-hydrolysis
• β-galactosidase
• fermentation
• lactose
• yogurt