Development of Natto Paste for Senior Citizens and Others Who Have Difficulty with Mastication and Deglutition

Abstract

Using “unicell beans”, a food material consisting of soybeans degraded to cells by several enzymes, we developed a Natto (fermented soybean) Paste, namely, natto without bean particles, for senior citizens who have difficulty with mastication and deglutition. To prepare Natto Paste, Bacillus subtilis PN 1 strain was inoculated into autoclaved unicell beans (soybean powder consisting of degraded single cells) in 4.5 volumes of water, and subsequently fermented at 37°C for 20h. The quality of Natto Paste from an inoculum of 10⁵cells/g was judged best by organoleptic tests. Chemical analyses showed that both the nitrogen solubilization ratio and nitrogen degradation ratio of Natto Paste were higher than those of commercial natto, suggesting that protein in the former degraded more than did protein in the latter. The nattokinase activity of Natto Paste was about 4.1 times higher than that of commercial natto. Organoleptic tests of Natto Paste were carried out by attendees of two senior citizen centers in Chiyoda-Ward, Tokyo. Natto Paste scored better than commercial natto on all items except “appearance” (p<0.05), the only aspect that required further improvement. This may have been due to the fact that Natto Paste differed from the expected image of natto. The above results showed that the Natto Paste developed in this study had a high protein content and appeared to be easy for senior citizens with difficulties in mastication and deglutition to eat. A high food functionality, similar to that of commercial natto, is expected.