Baker's yeast is exposed to various environmental stresses during its production and bread making. To clarify genes crucial for tolerance to these stresses, we performed genome-wide screenings of mutants that showed sensitivity or tolerance to stresses using a complete collection of deletion mutant strains of Saccharomyces cerevisiae. These screenings revealed genes crucial for tolerance to each stress. It is important to note that genes involved in the vacuolar acidification were indispensable for tolerance to multiple stresses. We applied the results of the screenings to select target genes for molecular breeding of stress-tolerant yeasts. Using so-called self-cloning technique, the target gene was disrupted or overexpressed in a derivative of an industrial baker's yeast strain. Results of the genetic modification suggested that this strategy was appropriate for breeding of stress-tolerant yeasts.

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Pearled barley kernels are usually cooked with rice in Japan. Their discoloration during and after cooking is one of the problems to promote barley consumption as a staple food. When cooked barley kernels were incubated, their a* values increased with time, which was influenced by water content of kernels. To evaluate a browning of cooked barley kernels, pearled barley kernels (10 varieties and 6 lines) were heated in mineral water at 105°C for 1 hour and further incubated at 70°C for 24 hours in a test tube. The a* value of the flour was measured after lyophilized and pulverized, and the increase in a* value during incubation after cooking (Δa*) was used as an indicator of the browning. The contents of flavanols in barley kernels decreased during incubation after cooking, as the Δa* increased. Prodelphinidin B3 decreased faster than procyanidin B3 and (+)-catechin. Varieties with high flavanol content in pearled kernels showed high flavanol content in cooked kernels (r=0.986) and large flavanol loss during incubation after cooking (r=0.921), when flavanol contents were determined by p-dimethylaminocinnamaldehyde (DMACA) method. The browning of cooked kernels was significantly correlated with the flavanol content in pearled kernels (r=0.716) as well as the flavanol loss during incubation after cooking (r=0.838). The browning of cooked kernels was slightly observed in proanthocyanidin-free lines. These results indicate that flavanols are the major factor to cause the browning of cooked barley kernels.

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Commercial thickeners are used to thicken thin liquids like water to reduce the risk of aspiration and dehydration of dysphagic patients. Attention has been often paid to rheological properties of thickened fluids, but the effects that adding thickeners has on taste have not been well-documented. We here evaluated taste of thickened liquids by sensory evaluation with special panels and by a taste sensor. We measured the intensity changes, when two kinds of xanthan gum-based thickeners (”TM” and “TR”) were added to various solvents including green tea and five types of standard single taste components. Standard solvents contain either one of the following compounds in water ; sodium chrolide, sucrose, epigallocatechin gallate, L-sodium glutamate, citric acid or L-tryptophan. TM had lower effects on the response pattern of seven electrodes in the taste sensor for five taste components. Regarding the effect of TR on taste intensity change, directional properties of increase and decrease were correlated well for five taste components between sensory evaluation and taste sensor evaluation. The effect of TM also matched between the two evaluation methods except for the direction of the saltiness change. The effect of TM on the green tea was lower than that of TR by both sensory evaluation and taste sensor evaluation. These results suggest that the measurement with the taste sensor is a useful index to evaluate the effect of various thickeners on the taste of foods and that the two evaluation methods could complement each other and enhance the accuracy of taste evaluation.

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Identification of tea cultivar was examined by amplified DNA fragment length polymorphism (AFLP) using black tea as a sample. The black teas used in this study were individually processed from 7 tea cultivars (Karabeni, Benifuki, Izumi, Z-1, Hatsumomiji, Benihikari, Benihomare). In addition, commercially used 7 Darjeeling teas, 3 Assam teas, 3 Kenya teas, and 3 Java teas as black tea on the market and 31 Japanese green tea cultivars were also used for comparison examination. AFLP comparison analysis indicated that it was possible to identify the tea cultivar by AFLP using the black tea as a sample. Moreover, a specific cultivar, Benifuki was detected in black tea materials by the analysis of AFLP comparison. It was suggested that 358.8bp fragment amplified by PCR with the primer pairs of EcoR I-ACA/Mse I-CTG and EcoR I-ACT/Mse I-CTC is a target DNA marker of Benifuki cultivar. AFLP will be used as a powerful tool to assess the descrimination of the processed-materials.

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In the Federation of Fisheries Cooperative Association of Nyuzen, in Toyama prefecture, F1-hybrid abalones have been cultivated in the deep-sea water warmed at 17 degrees. We examined free amino acids, ATP-related compounds, and rupture strength of the cultured abalone meat at intervals of one three months. The total amount of free amino acids and the content of each free amino acid were almost stable, and significant seasonal variations were not observed. Other results of analysis also did not show seasonal features. Sensory tests showed that the quality of the cultured abalone may be almost equal to that of the wild abalone.

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[in Japanese]

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