Mid of May I made experiments for the production of Yoba starter culture, out of freeze-dried culture. This starter culture will be used as “starting material” for the production of the Yoba drink. The procedure was carried out at the Life Dairy yoghurt factory in the small village Katete.
As personal preparation I wear my lab coat (which I brought from Switzerland), cleaned the working table, also with ethanol (70 %) and wore gloves. The spirit burner was used to ensure a sterile environment. Sterile water and petri dishes with MRS agar were prepared previously (see first experiment at Life Dairy). When these preparations were done, the production of Yoba starter culture can start.
The first step consisted in opening the glass ampoule containing the freeze-dried Yoba culture. Sounds simple, but the breaking of the glass ampoule caused problems. The small mark on the glass was done with a big saw (!) and consequently the glass broke completely in many small pieces. A new attempt and a new ampoule were needed and more carefully I could open the ampoule. The freeze-dried culture was dissolved in sterile water and transferred in a bigger tube. Subsequently this solution was inoculated on MRS agar petri dishes. After an incubation of 6 days at room temperature, colonies were visible on the petri dishes (picture 1). The next step was to make a subculture in pasteurized milk. For this purpose the workers of the factory filtered fresh milk and boiled it at least for 15 min at approx. 95 °C (pasteurization). After the cooling down, 1.5 % of glucose was added. The tubes containing the pasteurized milk supplemented with glucose was inoculated with culture on the petri dish and incubated at room temperature for 24 h, without shaking. Picture 2 shows the tubes before (left) and after (right) shaking at the end of the incubation. The viscosity was observed and the pH was measured and compared with the neg. control (only milk). A higher viscosity and a pH around 5 (picture 3) are indications that the Yoba culture has grown. As a last step, aliquots of the Yoba starter culture were made, transported to my guesthouse in Mukono and kept frozen at -18 °C.
The first Yoba starter culture was hence produced! 🙂