Researchers : O.C. Emata, I.G. Sarmago and Ma. C.R. Moreno

ABSTRACT

SUBSTUDY 1: Effects of cooling, freezing, and blast freezing on the quality of raw cow’s milk. Emata, O.C. & M.C.R. Moreno.
The objective of the study was to compare the chemical, foaming, microbiological, and sensory qualities of cooled, frozen, and blast frozen raw cow’s milk. Raw cow’s milk was subjected to different storage conditions and treatments before analyses. Milk samples were cooled at 4°C for 24 hr (T1), frozen at 0°C for 24 hr and thawed at 4°C for 48 hr (T2), and blast frozen at -40°C for 10 hr and thawed at 4°C for 72 hr (T3). Fat, protein, solids-not-fat, and density were significantly different among treatments while moisture, total solids, titratable acidity, and pH did not
significantly differ. There were no significant differences in the foam value and foam volume between cooled and blast frozen raw milk. Foam dissipation was not significantly different among the treatments. The aerobic count was significantly lower in blast frozen raw milk. Coliform and Escherichia coli counts were not significantly different among the treatments. Sensory characteristics did not significantly differ among treatments except for flavor whereas frozen milk was significantly higher. In conclusion, freezing and blast freezing of raw milk has no negative effect on the chemical, foaming, microbiological, and sensory qualities of raw cow’s milk.
SUBSTUDY 2: Non-fat kefir production using kefir starter culture in cooled, frozen, and blast frozen cow’s milk. Emata, O.C., M.C.R. Moreno & I.G. Sarmago.
Kefir is a viscous, fermented, and carbonated dairy beverage produced from the association of lactic acid bacteria, acetic acid bacteria, and yeast of the kefir starter culture inoculated in milk. Commercial production of this beverage uses kefir starter culture due to difficulty in maintenance of kefir grains. Hence, the objective of the study was to compare the physicochemical qualities of kefir produced from inoculation of kefir starter culture in pasteurized and non-fat cooled (T1), frozen (T2), and blast frozen (T3) cow’s milk. Moisture, total solids, titratable acidity, and viscosity were significantly different among treatments. Results showed that kefir made from frozen and blast frozen milk had significantly lower moisture content and higher total solids content compared to kefir made from cooled milk. Kefir made from blast frozen milk did not significantly differ in titratable acidity from the two treatments. Kefir made from frozen and blast frozen milk were found to be significantly higher in viscosity. High total solids, efficiency of lactic acid production, and viscosity are some indicators of a high-quality kefir. Thus, utilization of frozen and blast frozen cow’s milk are suitable in kefir production.
SUBSTUDY 3: Production of half-and-half cream and light whipping cream using cooled, frozen, and blast frozen cow’s milk. Emata, O.C. & M.C.R. Moreno.
The objective of the study was to compare the physicochemical qualities of half-and-half and whipping creams made from cooled, frozen, and blast frozen cow’s milk. Raw cow’s milk was subjected to different cooling, freezing, and thawing conditions prior to cream processing. Half- and-half and light whipping creams were both produced from cooled (T1), frozen (T2), and blast frozen (T3) cow’s milk. Fat, moisture, total solids, titratable acidity, pH, and viscosity were significantly different among half- and-half cream treatments. All physicochemical components excluding fat did not significantly differ between half-and-half creams made from cooled
and blast frozen cow’s milk. On the other hand, titratable acidity was the only physicochemical component that was significantly different among light whipping cream treatments. However, all values were within the typical ranges for light whipping cream composition. In conclusion, the results indicate that cooled, frozen, and blast frozen cow’s milk were suitable for both half-and-half and light whipping cream productions.