Wheat flour proteins were studied to identify the cultivar-specific proteins and use them to identify cultivars in flours. Proteins extracted from flours of Japanese wheat (cultivars Hokushin, Horoshirikomugi, Kitanokaori and Kachikei 33) and Canadian wheat (Canada Western Red Spring Wheat No. 1; 1CW) were analyzed by 2-DE with IEF gels over three pH ranges: pH 4-7, pH 5-8, and pH 6-11. This system enabled detection of more than 1600 protein spots. We recognized that among 50 protein spots showing cultivar-dependent qualitative changes, 25 proteins were wheat cultivar specific. These 50 protein spots were analyzed by N-terminal Edman degradation microsequencing and MALDI-TOF-MS; 21 protein spots were storage proteins, such as gliadin and low-molecular mass glutenin subunit. Five protein spots were identified as dehydroascorbate reductase (Triticum aestivum), triticin precursor (T. aestivum), alpha-amylase inhibitor (Oryza sativa), DNA-binding with one finger (Dof) zinc family protein (O. sativa), and nonphototropic hypocotyl 1 (NPH1) protein (Avena sativa). The other protein spots appeared to be hypothetical proteins (O. sativa or Arabidopsis thaliana) or functional unknown proteins. These specific proteins can be used as markers to identify wheat cultivars in blended flour composed of two or three flours.

Although it is known that the compositions of low-molecular weight glutenin subunits (LMW-GSs) are important factors for bread-making quality of wheat, it is still not clear which LMW-GSs confer improved bread-making quality and how those LMW-GSs interact with highmolecular weight (HMW) GSs. Using a hard red winter wheat line with good bread-making quality and a Japanese wheat cultivar with poor quality as well as their progeny we identified LMW-GSs associated with the bread-making quality. One such LMW-GS, KS2, which had a molecular weight of 42 kDa and was allelic to HS1, was associated with bread-making quality. Furthermore, by using four recombinant inbred lines with different HMW-GS and LMW-GS combinations, KS2 and HMW-GS 5 + 10 showed interaction effects on the bread-making quality. Two-dimensional polyacrylamide gel electrophoresis (PAGE) analysis showed that KS2 consists of two protein components and that HS1 is composed of three components. The N-terminal amino acid sequences of the five components were identical to the most frequently analysed sequence of LMW glutenin components.

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The lactic acid fermentation of instant Chinese noodle sheet by Lactobacillus plantarum NRIC 0380 changed the noodle quality as evaluated by texture and sensory tests. This interesting change was induced by only a short 2-h fermentation time, however the noodle quality subsequently degraded with prolongation of the fermentation of up to 24 h. SDS-PAGE analysis of proteins in the noodle sheet indicated no change in proteins extracted from the 2-h fermented noodle sheet compared to non-fermented noodle sheet. In contrast, native-PAGE analysis showed a shift in molecular weight of gluten proteins, with those extracted from the 2-h fermented noodle sheet having a higher molecular weight than those from nonfermented noodle sheet. These results strongly suggested a conformational change of gluten proteins in the noodle sheet caused by the short 2-h fermentation. The 2-h lactic acid fermentation decreased the pH from 8.5 to 7.5, but gluten proteins extracted from noodle sheet made with the addition of lactic acid to adjust the pH to 7.3 did not show this increase in molecular weight. Thus, the change from native state of gluten proteins does not seem to be induced by the presence of the lactic acid itself but by other factor(s) associated with lactic acid fermentation. On the other hand, the reduction of noodle quality by prolonged fermentation for up to 24 h seems to induce degradation of albumin and globulin proteins as revealed by SDS-PAGE analysis and also the change in the native state of gluten proteins as detected by native-PAGE analysis.

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