Effects of Processing Parameters on Physicochemical, Sensory Quality and Acceptability of Yoghurt from Milk of West African Dwarf Goat

Abstract

Pasteurization, incubation temperature and time are some of the important  processing parameters for the development of fermented dairy products with desired qualities. This study investigated the effect of processing parameters on some physicochemical attributes of yoghurt from milk of West African dwarf goat in order to obtain optimum process parameters and compared some sensory qualities and acceptability of the optimized yoghurt from goat and cow milk yoghurt as control. Response surface methodology (RSM) based on Box Behnken Design was used to optimize the processing parameters; pasteurization temperature (PT; 80 - 85 °C), incubation temperature (IT; 40 - 45 °C) and incubation time (ITm; 2.5 - 4.5 h); while pH, titrable acidity, total solids, fat, protein, viscosity were determined using standard laboratory procedures. Aroma, taste and mouth-feel were monitored for the sensory qualities. Data were analyzed using quadratic polynomial models and analysis of variance. The values for pH, titrable acidity, total solid, viscosity, fat and protein content of goat milk yoghurt ranged from 4.35 - 5.97, 0.57 - 3.70%, 13.54 - 32.64 mg/L, 130158 - 272712 mm2/s, 4.00 - 10.33% and 3.24 - 28.44%; respectively. Optimized WAD goat yoghurt had a sensory rating of 6.07 to 6.37, while cow yoghurt had a rating of 7.73 - 8.20. In conclusion, physicochemical properties of WAD goat milk yoghurt was significantly affected by pasteurization temperature, incubation temperature and time. The optimum processing parameters for WAD goat yoghurt are PT of 84.24^oC, IT of 44.22 ^oC and ITm of 3.8 h, optimized WAD goat milk yoghurt had a higher mean value for its protein content than cow milk yoghurt.

Keywords: Goat milk, cow milk, response surface methodology, lactic acid bacteria.