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Flavour-enhancing components of dried herring fillet (migaki-nishin in Japanese) were isolated and evaluated for their effects on sensory perception. Sensory evaluation revealed that addition of dried herring fillet water-soluble extracts to Japanese noodle soup significantly (P < 0.05) enhanced the soup flavour characters such as thickness, mouthfulness and continuity. The extracts were fractionated by dialysis and chromatography. Fractions containing flavour enhancers were isolated by sensory perception. Results from instrumental analyses showed that the kokumi flavour enhancers in dried herring fillet were creatine and creatinine.

Long-term ripened miso has a characteristic mouthfulness and continuity of flavour, which is heightened from 11 months of ripening. Focussing on its main components, changes of protein and sugar were investigated from 10 days up to 20 months of ripening. Protein and sugar changes during ripening did not correlate with sensory evaluation results. From visual observation of miso colour and colorimetric analysis of the water-soluble fraction, it was apparent that the Maillard reaction was occurring during 5–11 months of ripening. By fractionation and evaluation of umami, mouthfulness and continuity, we were able to identify a water soluble fraction of 20 month ripened miso with a molecular weight of 1000–5000 which was coloured and appeared to be a peptide that has undergone the Maillard reaction. From these results, the Maillard-reacted peptide was considered to be a key substance which gives the characteristic flavour (mouthfulness and continuity) of long-ripened miso.

This study investigated the flavour-enhancing properties of the Maillard reaction products from 1000 to 5000 Da peptides. Protein hydrolyzates obtained from enzymatic hydrolysis of soybean protein were fractionated with UF membranes to obtain the 1000–5000 Da fraction. Xylose was added to this fraction and allowed to react for 3.5 h at 95 °C. This reaction mixture was fractionated with 1000 and 5000 Da cut off membranes to obtain the 1000–5000 Da fraction (the “Maillard peptide”). To evaluate the flavour characteristics of the Maillard peptide, an additional test on a umami solution was carried out. It was found that the Maillard peptide produced an enhanced effect on flavour, including umami, continuity and mouthfulness in the umami solution and in consomme soup.