Search

Fermentation of kamaboko in koji with wheat (KW), rice (KR), brown rice (KB), or soybean (KS) was performed by simulation of tofuyo processing. Moisture and protein content decreased with fermentation, while other detected compounds increased significantly. Ash content increased from 12.9 g/100 g in kamaboko to 17.9–20.2 g/100 g (KW, KR, and KB) and 26.8 g/100 g (KS) after 4 weeks of fermentation. Mineral and fatty acid composition varied. After 8 weeks of fermentation, KW, KR, and KB exhibited total free amino acids, sugar, and phenolic content of 2804–3396 mg/100 g, 43.5–55.3 g/100 g, and 207–263 mg/100 g, while KS showed 12,300 mg/100 g, 11.3 g/100 g, and 539 mg/100 g, respectively. Radical scavenging and angiotensin-converting enzyme (ACE) inhibitory activity increased significantly following fermentation. KS showed the strongest 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity and ACE inhibition. Sensory analysis revealed that KW, KR, and KB were significantly more favorable than KS, with significantly stronger sweetness and weaker smell, saltiness, and aftertaste. These results indicate that wheat, rice, and brown rice koji-fermented products are acceptable as food, and that the soybean koji-fermented product is a useful source of bioactive compounds such as peptides and phenolics.

Traditional Japanese koji-fermented tofu (tofuyo) processing was simulated to make fermented seafood. The koji fermentation process at room temperature was applied to steamed surimi and kamaboko to develop new types of food, extend their shelf life and improve their health-promoting effects. Extractive nitrogen and sugar contents, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, copper-reducing activities, and angiotensin-converting enzyme (ACE) inhibitory activity significantly increased after fermentation. These increases were the highest in kamaboko. Kamaboko fermented for 6 months had the highest DPPH radical scavenging, copper-reducing activities, and ACE inhibition. Kamaboko fermented for 6 months showed statistically the same copper-reducing power and ACE inhibition to tofuyo, but significantly higher DPPH radical scavenging activity. Size-exclusion chromatography showed the same peak(s) analyzed as Lowry-reactive substances, ninhydrin-reactive substances, sugar, and DPPH radical scavenging activity. The most antioxidative fraction had a molecular weight of 900–1300 and a sugar and amino acid structure(s). There was no specific ACE inhibitory fraction(s). The koji fermentation process at room temperature did not need additional energy, led to different foods with a sweet and a umami-rich taste and a soft texture. Additionally, koji fermented steamed surimi and kamaboko effectively prolonged best-before periods of up to 6 months.

Bulky hard peel of Citrus natsudaidai is discarded and not utilized enough in Japan. In this study, the nutritional composition and volatile components of three cultivars of C. natsudaidai peel were determined. Considering the proximate composition and minerals, C. natsudaidai peels showed good carbohydrate and potassium content. The peel color varied probably due to the difference of cultivars. C. natsudaidai peels were extracted and analyzed for free amino acids and for fatty acids and volatile compounds. The amount of free amino acids in the extracts was not enough to affect the taste of extracts. The proportion of individual fatty acid was not comparable to other plant oils, however, typical aroma compounds with citrusy smell were identified. C. natsudaidai extracts could contribute for the utilization as flavoring additives without affecting taste.