The overall goal of this protocol is to enable the production of nutritious and probiotic fermented milk and other probiotic fermented foods with the use of a starter culture using very basic equipment and techniques. In East Africa, one gram of a dried bacterial starter culture can be used to convert one liter of pasteurized milk, which has been cooled down to 45 degrees Celsius and transferred to a vacuum flask, into one liter of probiotic drinking yogurt. Afterwards, the yogurt can be used to start the production of 100 liters of probiotic yogurt in milk cans, which equals 400 plastic sashays of 250 milliliters drinking yogurt.
This method is a dynamite innovation for sustainable improvement of a nutrition and health status of malnourished people in resource-poor countries. Because they're people that can be exposed to many environmental risk factors that may cause infectious diseases with serious implications. The main advantage of this technique is that it is easy to apply, highly accessible to everybody, including people in resource-poor countries who benefit most from it.
Also, the process of fermentation creates a yogurt with added value as compared to milk. One of the implications of this technique extends towards prevention, relief, and curation of diarrhea. And that is still a major cause of death among children less than five years old.
Actually, it's the probiotic Lactobacillus rhamnosus strain present in this starter culture that has shown to be effective against diarrhea in a number of independent clinical trials. The method can be used for the production of a probiotic drink yogurt and also for the production of other types of fermented foods, for example, cereal, vegetable, fruit-based products, like our traditional obushera, uji, kwete, and mutandabota. Visual demonstration of this method offers enormous benefits because now we can efficiently teach and show it to our target group, which are mostly people in the remote areas in resource-poor countries, how they can apply it.
Demonstrating the quality tests of the milk as well as the microscopy of the yoba yogurt is done by Justyne Laba, a technician here at the Micropia Laboratory. To detect abnormalities or spoilage of the cow's milk by organoleptic testing, check the visual appearance and smell of the milk sample. For a clot-on-boiling test, hold a one tablespoon volume of the milk over a heat source until the milk begins to boil.
Then, remove the spoon from the heat, and assess the sample for clotting. For the lactometer test, fill a container with at least 15 centimeters of 30 degees Celsius milk, and place the lactometer into the milk. A reading of 28 or more indicates that the milk is of sufficient density without added water.
For the ethanol test, mix an equal volume of milk with an equal volume of 80%ethanol in distilled water. When the milk is clotting, the quality is not good, and it should not be used. To pasteurize fresh milk, first filter the milk through a boiling water-sterilized 0.1 to 0.5 millimeter pored instrument into a small pan.
Cover the pan with the lid, and place the pan in a slightly larger pan. Fill the larger pan with water up to two centimeters below the rim of the smaller pan, and heat the milk until it reaches 85 degrees Celsius as measured with a laboratory thermometer. Then, turn the heat source to low, and maintain the temperature of 85 degrees Celsius for 30 minutes.
At the end of the pasteurization, remove the pan of milk from the water without removing the lid. When the milk has cooled to 45 degrees Celsius, transfer the sample to a vacuum flask, and inoculate the milk with one gram of the appropriate starter culture. After 16 hours in the vacuum flask, confirm that the pH of the fermented milk is 4.4 or less.
As a control, the pH of the milk is checked first, which shows a value of 5.8 or higher. Next, the pH of the yogurt is checked showing a pH of 4.3. Agitate the milk for five to 10 minutes to obtain a smooth texture.
Then, transfer 10 milliliters of the fresh starter into each well of an ice cube tray, and store the starter at minus 18 degrees Celsius for up to three months. The frozen starter cultures can now be used for the production of fresh probiotic yogurt. Pasteurize the milk in a double boiler as demonstrated.
When the milk reaches 60 degrees Celsius, add sugar at the suggested concentration of 5%weight per volume. Stir well with a boiling water-sterilized mixing spoon. Then, continue heating the milk until it reaches 85 degrees Celsius as measured with a laboratory or kitchen thermometer.
When the milk has cooled to 45 degrees Celsius, inoculate the sample with one cube of frozen starter per liter, and transfer the milk to the appropriate number of vacuum flasks. Allow the milk to ferment until a pH has been reached of 4.3 or below. Then, agitate the fermented milk to achieve a smooth texture, and store the fermented milk at seven degrees Celsius for at least three hours before consumption or up to one month.
For fermentation at 37 degrees Celsius, the acidification profiles of fresh starter and fermented samples exhibit slight differences in the onset of the exponential acidification at approximately 30 minutes. Although, the final pH values of both types of culture are very similar after 16 hours. Here, typical pH values and titers of the propagated L.Rhamnosus and S.thermophilus strains for different fermented foods are shown.
High-performance liquid chromatography, in combination with a refractive index detector analysis of fermented and non-fermented milk indicates that the lactose levels in the milk decrease while lactic acid and galactose levels increase as a result of the metabolic activity of the starter culture. In this video, the presence of Lactobacillus and Streptococcus in fermented milk can be observed. Once the process is mastered, people can easily make yogurt overnight with only using basic things, like a starter culture, milk, a pan, and a source of heat.
When finishing the procedure, it's important to remember to enjoy the consumption of your results the following day. With this protocol, you can prepare the probiotic fermented foods, like the cereal-based kwete. Of course, it is depend on the availability of the local food ingredients, eating habits, and your preferences.
This technique enables people in resource-poor countries to improve their health and wealth by the local production and sales of probiotic yogurt drinks. After watching this video, you should have a good understanding of how to produce a nutritious and probiotic fermented milk by using a starter culture and very basic equipment. Don't forget that we work with fire and hot milk because of the pasteurization step.
So, be careful not to burn yourself.
