吉田 充

In this study, the genome sequences of two Basidiomycetous yeasts, Tremella yokohamensis and Tremella fuciformis , which have very similar morphological characteristics, were determined. The genomic sequence data obtained will be useful for understanding the taxonomy and metabolic-related genes of basidiomycete yeasts.

Wild boar meat containing radioactive cesium (Cs) of approximately 1000 Bq/kg (134Cs+137Cs) was processed into bacon, sausage, and ham. In order to understand the concentration and quantity change of radioactive Cs, processing factor (Pf) and food processing retention factor (Fr) were calculated. The radioactive Cs quantity in the meat did not reduce during smoking. The dehydration-related meat mass reduction during smoking without decrease of radioactive Cs led to Cs condensation in the bacon compared with the raw rib meat before processing, resulting in a Pf of 1.18. Soaking in liquid, such as pickling in liquid and desalting or boiling in water, effectively removed radioactive Cs by leakage into water. Therefore, the Fr value of the boiled ham produced from a loin meat block through the above-described three liquid-soaking processes was 0.27. The Pf value of the boiled ham was 0.30 due to the meat block mass reduction after boiling as the result of dehydration along with the protein thermal denaturation-related muscle tissue shrinkage. The steamed ham Fr value was 0.53 since the removal of the radioactive Cs was less efficient by steaming than by boiling. The Pf value of the steamed ham was 0.54, almost the same as the Fr value, as the mass decrease rate was the same as the radioactive Cs decrease rate by steaming. The Fr and the Pf values of the boiled sausage, of which processing did not include soaking in the pickling liquid, were 0.64 and 0.62, respectively. The steaming of the sausage meat did not remove radioactive Cs during the dehydration-related mass reduction leading to Fr and Pf values of 1.01 and 1.17, respectively. As the result of this study, processing to boiled ham was the most effective measure for reducing both radioactive Cs quantity and concentration in raw meat. Processing to bacon and steamed sausage showed no Cs quantity reduction with the moisture loss resulting in Cs condensation compared to the raw material.

In this study, we investigated the possibility of the geographical origin discrimination between Japanese and Mexican kabocha pumpkin using δ13C and δ18O in lyophilized raw flesh. Kabocha harvested in Hokkaido, the major kabocha production area in Japan, could be discriminated against not only that grown in Mexico but also that in New Zealand. However, seasoning after cooking or processing affected the δ13C and the δ18O values. Crude fiber extraction eliminated the effect of seasonings and enabled the adoption of the δ13C and δ18O values in crude fiber for the geographical origin verification of kabocha even after cooking and processing. The usage of δ13C and the δ18O in crude fiber would extend the application possibilities of stable isotope analysis in the geographical origin determination of various cooked and processed vegetables and fruits as well as raw materials.