Fermentation is the process of utilizing nutrients anaerobically (DSouza & Killedar, 2006). Yogurt is a product of fermentation brought by adding Streptococcus thermophilus and Lactobacillus bulgaricus to ferment the milk and turn it into a thickened acidic food ( Lee & Lucey, 2010). These bacteria partially digest milk and produce lactic acids which makes it edible even to people who cannot tolerate milk (Cascio & Dinstel 2011).
The lactic acid decreases the pH of the milk and coagulates the milk proteins, giving it a semi-solid consistency and the ability to inhibit the growth of other microorganisms (Kahl, 2011). The primary goal of the study is to demonstrate the use of microorganisms in the food industry using yogurt as an example. Secondary to that, the study also aims to present a simple instruction on how to make a homemade yogurt using cultured bacteria found in commercial yogurt.
Heat treatment â†’ Cooling to Incubation Temperature â†’ Inoculation â†’ Fermentation â†’ Cooling â†’ Packaging Figure 1: General steps in the yogurt production.
Figure 1 summarizes the procedure in the production of yogurt. Heat treatment was done for 30 min at 85 C to ensure that the milk was free from unwanted microbes. After heating, the milk was cooled to temperature suitable for the growth of the starter bacteria which was around 40C 45C. Commercialized unflavored yogurt was used to serve as a starting culture. The milk was placed in an air-tight jar and was left undisturbed for at least 10 hours and the temperature was kept at 40C-45C.
The process in making yogurt involves fermentation. The bacteria are microaerophilic and thus, high concentration of oxygen could disrupt the process and affect the consistency of the resulting yogurt as well as its taste (Anonymous, n.d). Proper control of temperature must be observed to achieve the desired texture. If the temperature is very high, the bacteria could die and if it is too cold, the culture would grow slowly.