Yogurt Formation Lab.docx

Yogurt Formation Lab BE 3340 Dr. Sabliov Jonathan Thomas 5 February 2019

Introduction To make a variety of foods commonly eaten by consumers, lactic starter cultures, shown in Figure 1, are employed in food manufacturing. Lactic starter cultures are microorganisms that breakdown the milk sugar, lactose, and convert it into lactic acid, using the two components of sugars (glucose and galactose) as sources of energy. These lactic starter cultures are accessible to the public as they are sold in public stores. Figure 1: Lactic starter culture Objective The objective of this lab is to demonstrate general principles of bioprocess engineering, demonstrate the use of microorganisms in food processing by using yogurt as an example, compare a pedestrian production of yogurt to a commercial setting, and compare both productions to the Nepalese traditional clay pot method.

Materials The reagents needed for this experiment include: 2.5 g of starter culture, 0.5 L of whole milk, and 19.6 g of dry non-fat milk powder. The materials needed include: 1 beaker, 1 hot plate, a cold water bath, an incubator that can reach 42 oC,, 1 Mason jar (qt.), 1 thermometer (nonmercury), and 1 stirrer.

Methods The process, shown in Figure 2, first consisted of heating 0.5 L of whole milk and 19.6 g of dry non-fat milk powder to 85 oC and maintaining for 2 minutes. The first step of this process helps remove unwanted biological impurities and denature any enzymes that would hinder the fermentation process or cause problems in post fermentation processes. Temperature must be maintained at, or a little below, 85 oC for 2 minutes and stirring must be continuous to make sure scalding does not occur. The solution is then cooled down to 42-44 oC in an ice bath. Then, 2.5 g

of the starter culture would be added. Finally, the solution should be transferred to a Mason jar, sealed, and then incubated at 42 oC for 3 to 6 hours.

Figure 2: Flowchart Process of Homemade Yogurt Production

Results The yogurt, seen in Figure 3, had a look and smell close to the commercial equivalent, it smelled very bitter and had a thick consistency, and looked to be coagulated.

Figure 3: Yogurt after incubation

Discussion Table 1: Prices of Materials Material

Quantity

Total Cost (USD)

Cost per Unit Quantity (USD)

Starter Culture

30 g

28.50

0.95

Whole milk

3.78 L

10.74

2.84

Mason Jars

12 jars

10.92

0.91

Powdered milk

907 g

9.48

0.01

As seen in Table 1, the total price of materials and reagents is $59.64. The cost of making 0.5 L of yogurt from 0.5 L of whole milk, 2.5 g of starter culture, 19.6 g of dry non-fat milk powder, and 1 Mason jar is $4.90. 1 quart (about 1 L) of yogurt from Walmart costs $3.78. This displays that twice the volume of yogurt would cost less than making homemade yogurt. The smell of the homemade yogurt smelled similar to commercial Greek yogurt, minus the additional flavoring, and exhibited the same consistency as commercial Greek yogurt as well, as seen in Figure 3. The quality of the yogurt is determined by the strength of the starter culture and how well the milk solution was pasteurized and cooled. The homemade method of making yogurt differed the commercial method as the commercial is more efficient and automated. The commercial method allows for more product to be made in a shorter amount of time and augments the final product with post-fermentation processes, such as addition of flavorings and

Figure 4: Nepalese clay pot method

preservatives, and packaging and distribution. The main difference in the homemade method and the Nepalese clay pot method (shown in Figure 4), is instead of being placed in an incubator, the clay pot is usually kept under blankets

and heated in that manner. The clay pot traps moisture well and that is how the yogurt is incubated.

Conclusion A popular method of bioprocessing food is the addition of lactic starter cultures. The application of bioprocessing for food exponentially helps the food processing industry by clearly explaining what processes are needed and finding what conditions makes the entire process efficient. While applying bioprocessing methods to yogurt-making at home is informational and instructional, it is cost inefficient and can be detrimental for people’s health, especially if pasteurization methods aren’t correctly followed.