by: Muchtadi D,Sutiyoso H, Suliantari, Fardiaz S, Rahayu WP
Department of Food Science and Technology, Bogor Agricultural University
The molds used in this study were Rhizopus sp. and Mucor sp., while the yeasts used were Rhizopus sp, C. utilis, C. solani, S. cerevisiae and Endomycopsis sp. Gamma irradiation (60Co) was conducted to C. utilis and C. solani, at doses of 0, 10, 20, 30 and 40 krad with irradiation rate of 61.64174 krad/hour. Molds were irradiated using ultraviolet light. As the mineral and nitrogen sources for the microorganisms, (NH4)2SO4, (NH.)2HPO and MgSO4.7H2O were used in the form of solution to soak peeled cassava tubers before being fermented. Growth stimulation effect for the yeasts was observed from treatment of gamma irradiation at dose of 10 krad. “Ragi tape” prepared using these yeasts and non-UV-irradiated molds in combination with the utilization of mineral (nitrogen) sources, significantly increased the protein content of “tape ketela”. The “tape ketela” obtained using those treatments had a protein content of 6.43% (dry basis) compared to 2.91% (db) for the control. However, it had a lower reducing sugar content, i.e. 11.43% (db) compared to 31.76% for the control. The viability of the yeasts and molds in “ragi tape” during storage in a refrigerator as well as at room temperature is found good until four weeks of storage.
Keywords: gamma irradiation, yeast, tape, fermentation
Presented at A Technical Document, Issued by The International Atomic Energy Agency, Vienna, 1990