YOGURT PRODUCTION WITH DIFFERENT STARTER CULTURES

This study aimed to evaluate different starter cultures for yogurt production. Mixture containing 500 mL whole milk, 25 g powdered milk and starter culture was inoculated in a thermostated bath at 45 °C/4.5 h without stirring. Two assays with different starter cultures were made: (1) lyophilized culture (200 mg); (2) natural yogurt (85 g). Samples of 10 mL were collected every 30 min to determinate pH and Dornic acidity (ºD), and the assays were performed in duplicate. At the end of the process using a TA.XT Plus texturometer the following parameters were evaluated: firmness, consistency and viscosity. It was possible to observe that there was a decrease in the pH value from 6.2±0.1 to 4.2±0.1 and 5.7±0.1 to 4.0±0.1 for assays with lyophilized culture and natural yogurt, respectively. The values at the end of fermentation are in agreement with what is recommended in the literature (4.0-4.4). At the end of the process the Dornic acidity was 90.5±0.9 ºD for the lyophilized culture and 100.23±0.8 ºD for the natural yogurt. These values were higher than those foreseen in the Brazilian legislation that recommends that the produced yogurt has 85-90 ºD. Texture parameters showed that assay (1) 30.9 g, 723.9 g s-1 and -22.0 g s-1 and assay (2) 31.9 g, 758.7 g s-1 and -74.2 g s-1 were obtained for the parameters of firmness, consistency and viscosity, respectively. It is concluded that yogurt can be produced with both starter cultures and that the natural yogurt assay was affected by the excessive processing time, causing high Dornic acidity and affecting the texture parameters.