The main sources of calcium intake in a diet are milk and dairy products, and dietary calcium absorption ranges from 10% to 40%. Approximately 32% of calcium is absorbed from milk and dairy products. An insufficient intake of calcium by the Polish population has stimulated the marketing of an increasing number of food products fortified with calcium, enriched fruit juices and dairy products in particular. In this study, yoghurts were  produced from 2% fat milk, thickened with 3% of milk powder, fortified with calcium compounds 800 Ca (mg kg-1 of milk) and pasteurized at the temperature of 72 ºC for 15 seconds. Fermentation with the yoghurt starter culture YC-X16 (Chr. Hansen) was performed at 45 °C for 4.5 hours, and then the fermented beverages were cooled down to 5 °C. The beverages were examined during the incubation for a change in yoghurt acidity directly after the addition of the starter, after 2 hours and after 4 hours of incubation. After 24 hours of cold storage, yoghurts were analyzed for syneresis, pH, texture and colour. The addition of calcium compounds to milk at a dose of 800 Ca (mg kg-1 of milk) determined pH and total acidity. Milk was soured the most by calcium D-gluconate, and neutralized the most by calcium bisglycinate. After 4 hours of fermentation, the acidity of yoghurt most similar to the control sample was found only in the yoghurt fortified with calcium chloride. However, after 24 hours of storage, the acidity and syneresis most similar to the control sample were determined in yoghurt with calcium citrate. Fortification with calcium chloride and calcium bisglycinate darkened the colour of yoghurts. The addition of a dose of 800 Ca (mg kg-1 of milk) in the form of lactate, chloride and citrate increased hardness and adhesiveness of yoghurts.

22.3.2017