Kinetic acidification and quality composition of yoghurt produced with soursop puree

Abstract

The growing demand for healthy yoghurt products necessitates the need to investigate the effect of process parameters and soursop puree to sugar concentration on the kinetic acidification, quality composition and sensory attributes of yoghurt. Taguchi design was used to interact incubation temperature (39–43 °C), pasteurization temperature (80–100 °C) and soursop puree to sugar ratio (0%, 50% and 75%) to produce nine yoghurt samples. The acidification kinetics of the yoghurt samples were estimated using maximum acidification rate, time required to achieve maximum acidification and time at which pH of 4.6 was reached. The proximate composition, mineral content (potassium, calcium and phosphorus), vitamin C, total phenolic content were the quality composition that were determined while the sensory attributes of the yoghurt samples were also evaluated. The maximum acidification rate, time required to achieve maximum acidification and time at which pH of 4.6 was reached were 0.0042 pH/min, 2 h and 3.5 h, respectively. This occurred when 75% of soursop puree to sugar ratio was used to produce yoghurt. The moisture content of the yoghurt samples decreases as the soursop to sugar ratio increases. The crude protein, crude fat, carbohydrate, fibre, vitamin C and total phenolic contents increases as the soursop to sugar ratio increases. The calcium content of the yoghurt samples ranges from 298.5 to 623.5 mg/l, 408.5 to 810.5 mg/l in potassium and 120–519 mg/l in phosphorous, respectively. This information could assist yoghurt producers to develop new yoghurt varieties with improved quality and sensory profile.