Sensory Changes in Umami Taste of Inosine 5'-Monophosphate Solution after Heating

Discrimination in umami taste of inosine 5′-monophosphate (IMP) solution caused by thermal degradation was investigated by sensory evaluation. The difference threshold of umami taste of 0.005% IMP solution in the presence of 0.05% monosodium glutamate (MSG) was 0.002%. The difference threshold of a 0.005% IMP solution decreased by about one half when heated at 95°C for 15 h. Inosine, one of the main products of the thermal degradation of IMP, had a bitter taste. The detection threshold of inosine varied widely among panelists. Heating a 0.005% IMP solution at 95°C for 15 h formed inosine at about one tenth of its lowest detection threshold.     

IgG Antibody from Hen Egg Yolks: Purification by Ethanol Fractionation

A procedure was developed for large-scale preparation of IgG antibodies from egg yolks. The supernatant from egg yolks was obtained after an initial 9–fold dilution with water. The lipids in the supernatant were then almost completely eliminated from the water-soluble protein fraction containing the antibody, by precipitation with 60% ethanol and filtration. Yolk antibody was purified from the lipid-free water-soluble protein fraction by ethanol fractionation at final concentration 30% (pH unadjusted), and again at 25% (pH 7.4). The purified fraction was composed of >99% pure IgG. Recovery of antibody was calculated as 40%.     

Thermal Degradation of Flavor Enhancers, Inosine 5'-monophosphate, and Guanosine 5'-monophosphate in Aqueous Solution

The mechanism of thermal degradation of inosine 5′-monophosphate (IMP) and guanosine (GMP) was investigated kinetically in aqueous solution as a function of pH and temperature. The degradation of IMP and GMP followed first order kinetics. The rate constants were considerably affected by pH and temperature. The half-life times at 100°C were: IMP, 8.7 hr (pH 4.0), 13.1 hr (pH 7.0), 46.2 hr (pH 9.0); GMP, 6.4 hr (pH 4.0), 8.2 hr (pH 7.0), 38.5 hr (pH 9.0). These times were shortened to about one-third by raising the temperature 10°C. The predominant degradation products were nucleosides and phosphoric acid, indicating that the main reaction of the thermal degradation was the hydrolysis of the phosphoric ester bond in the nucleotides.     

Proximate and Amino Acid Composition of the Roe and Muscle of Selected Marine Species

Crude protein, total lipid, water, cholesterol, and amino acid com-position of the roe of eighteen Pacific marine species were determined and compared with those of muscle from the same marine species. Crude protein and total lipid were higher in roe than in muscle, while water was lower. Cholesterol in roe was generally tenfold higher than that of muscle but only around one-fourth that of hen egg yolk. Glutamic acid, leucine, and aspartic acid were generally found to be the major components of roe. Leucine and proline content were significantly greater in roe than in muscle. On the whole, roe was well balanced with the essential amino acid and had a good E/NE ratio and may be considered a food source of high-quality protein.