This paper describes the mechanism behind consumer evaluations of the palatability of food. Preliminary observations leading to the quantitative analysis of palatability were made while traveling in Italy and France and studying the local food culture. The traditional food processing technologies in Italy that produce their well-known balsamic vinegars, hams, and risotto rice, provide a basis for highly palatable meals. Additionally, an evaluation method, practiced at the Bocuse d’Or in Lyon, France, showed that we use all five senses to evaluate a plate of food. These observations should be valuable for creating a structured platform for evaluating palatability based on communication between our five senses.
The effects of pre-treatment with aqueous ethanol on heat-induced gel formation of commercial milk whey protein were investigated using surface hydrophobicity analysis, rheological measurement, ultrasound spectroscopy and secondary structure analysis by FT-IR. Among the three kinds of whey proteins pre-treated with 10, 25 and 50% aqueous ethanol, the 10% treated sample showed a high gel forming ability based on the higher compressibility of the sample system, as well as the higher frequency dependency of the ultrasonic attenuation, which showed involvement of more proteins in construction of the network during heat treatment. It is suggested that these remarkable gel properties are due to stabilization of the native-like structure in the secondary structure level even at 60 °C, and formation of the aggregated particles similar to that of milk whey without aqueous ethanol pre-treatment in scanning electron microscopy analysis. These findings suggested that pre-treatment using aqueous ethanol for protein is a good technique for improving food functional properties.
The Liquor Tax Law in Japan was revised in 2018, and the revision has significantly deregulated both the variety and the quantity of the auxiliary ingredients permitted for use in beer. Consequently, we prepared worts containing three citrus fruits (Kara, Miekinan4gou, and Summer fresh), passion fruit, and atemoya that were local fruits in Mie Prefecture, and brewed beers by fermenting the worts with top-fermenting yeast or bottom-fermenting yeast. By the fourth day from the beginning of fermentation, various sugars included in the worts, such as glucose, fructose, maltose, and maltotriose, were substantially decreased, and had been utilized for ethanol fermentation. The flavors of the fruits, especially organic acid and the volatile terpenes, remained in the beers. Microorganisms were detected in the juices of the passion fruit and atemoya, but were not detected in the beers in which these fruit juices were employed as auxiliary ingredients. The antibacterial action of the alcohol and hop likely had a sterilization effect. The results of sensory evaluations indicated that, although the fruit flavors remained in the beer, the conditions of fruit addition need to be optimized.
Natto is a traditional Japanese food with a unique viscous property. The viscous property mainly derives from the poly-γ-glutamate (γ-PGA) produced by Bacillus subtilis, the so-called natto bacterium, during the fermentation of steamed soybeans. However, the γ-PGA-producing ability of B. subtilis is easily lost by insertion sequence (IS) transposition to the comP locus. We isolated a recA-deficient mutant, and evaluated the γ-PGA production and IS transposition in B. subtilis. After repeated passages, the parent strain lost the γ-PGA-producing ability whereas the recA-deficient strain retained it; IS transposition to the comP locus was observed in the parent strain, but not in the recA mutant. Furthermore, the amount of γ-PGA produced by the parent strain in natto was reduced to less than 1/10 that of the recA mutant. These findings suggest that the recA mutant may stabilize the viscous property of natto fermented food.
We compared the extractive components of the ordinary and dark muscle portions contained in hongarebushi and arabushi, both of which were produced by different katsuobushi-manufacturing processes. Taurine, histidine, and anserine were abundant among the free amino acids contained in both of the fushi types and muscle portions. In hongarebushi, taurine was richer in the ordinary muscle than in the dark muscle. Histidine and anserine were also abundant in the ordinary muscle in both of the fushi types. There was no significant difference in the composition of the bound amino acids compared to that of the free amino acids. Inosine monophosphate (IMP) was richer in the ordinary muscle than in the dark muscle, and there was little difference in inosine content between the muscle portions. The contents of compounds, such as creatine, creatinine, lactic acid, moisture and extractive nitrogen were higher in the ordinary muscle. Umami strength, calculated from both the IMP and glutamic acid contents, was found to be significantly higher in the ordinary muscle than in the dark muscle, but not between the fushi types.