The effects of preheating on the digestibility of ovalbumins (OVAs) derived from five poultry eggs were examined by the treatments with simulated gastric (SGF) and intestinal (SIF) fluids and compared to those of chicken. Similar to chicken OVA, the duck, Japanese quail, guinea fowl and turkey OVAs were relatively resistant to SGF on preheating below 65°C, getting susceptible to SGF from 70°C to 80°C, and then their digestibility decreased at more than 90°C. Ostrich OVA was relatively resistant to SGF on preheating at 80°C or lower but its digestibility markedly improved by preheating at more than 90°C. The poultry OVAs except for duck OVA were relatively resistant to SIF without preheating as well as chicken OVA but their digestibility by SIF became higher than that of chicken above 60°C of preheating. Duck OVA was rapidly digested by SIF regardless of the preheating temperatures. Since OVA was a major protein in the poultry eggs examined here, preferable heat treatments would be from 70°C to 80°C for duck, Japanese quail, guinea fowl and turkey eggs and more than 90°C for ostrich egg in order to enjoy nutritional benefits.
We studied whether it is possible to prepare choux as a new product from buckwheat flour. Firstly, the amount of liquid egg added to choux batter was adjusted based on the gelatinization characteristics of the buckwheat starch. Furthermore, the effect of replacing buckwheat flour with α-buckwheat flour was investigated. The gelatinization temperature of buckwheat flour was higher than that of wheat flour. Moreover, since buckwheat choux batter has high viscoelasticity, the specific volume increased when increasing the amount of liquid egg added. Furthermore, as the amount of buckwheat flour replaced with α-buckwheat increased, the yield stress of the choux batter increased. Each buckwheat choux prepared by adding 120 g of liquid egg increased the weight loss ratio and specific volume after oven heating, but the specific volume was smaller than that of wheat flour. In addition, the buckwheat choux prepared by adding 100 g of liquid egg significantly increased the cavity area formed by blending 10% and 30% α-buckwheat flour.
Using cabbage, which was separated into the outer, middle, and inner leaves, we investigated the changes in the ascorbic acid (AA) content after steam cooking at two different temperatures, 100°C and 70°C. The AA content was higher in outer leaves, followed by middle and inner leaves. AA retention was the highest in all layers of the cabbage when cooked using a microwave, followed by cooking at 100°C and 70°C using a steamer. We investigated the serial changes in the AA content of the middle leaves after steaming at 100°C and 70°C. The AA retention rate after cooking at 70°C for 10 min was significantly lower than that after steaming at 100°C. Moreover, the AA retention rate after 20 min was lower when the cabbage was steamed at 70°C. We investigated the AA retention rate after steaming at various temperatures for 10 min. The retention rates were 81.1%, 59.2%, and 91.2% after steaming at 100°C, 70°C, and 50°C, respectively, indicating that the maximum decline in AA content was observed when the cabbage was steamed at 70°C. The decline in AA content was inhibited when the cabbage was heated in a microwave before steaming at 70°C.
This study investigated whether differences in previous dietary experiences with Katsuobushi stock influence the palatability of reduced-salt dishes prepared using Katsuobushi stock. The palatability of reduced-salt Japanese-style clear soup improved as the concentration of Katsuobushi stock increased, regardless of the subject's previous dietary experience with Katsuobushi stock. In contrast, as the concentration of Katsuobushi stock was increased, the palatability of reduced-salt Takikomimeshi (rice cooked with stock, soy sauce, and vegetables) improved among subjects who had more previous dietary experiences with Katsuobushi stock, but it did not improve among subjects who had less previous dietary experiences with Katsuobushi stock. This may have been due to differences in preferences regarding the characteristic taste and aroma of Katsuobushi stock. This suggests that if the preference for the taste and aroma of Katsuobushi stock can be increased through accumulated dietary experiences, then the palatability of various reduced-salt dishes containing Katsuobushi stock can be improved.