The effects of change in cooling rate on the gelation of 0.8% sodium-type gellan gum solutions with and without 0.3% sodium chloride (NaCl) were investigated based on the storage moduli of the solutions. The cooling rate was changed at the temperature where the storage modulus began to increase. The storage modulus of 0.8% sodium-type gellan gum solution with 0.3% NaCl was larger in the measurement for cooling rate change from slow to fast than in that for change from fast to slow.
After the cooling rate change, in cases where the rate was equal to that before the change, the slower the rate, the larger the storage modulus. When the cooling rate was changed from slow to fast, the lower the temperature at which the rate was changed, the larger the storage modulus became. These results show that the cooling rate before the increase of storage modulus has a remarkably large influence on the formation of three-dimensional network structure.

View full abstract

The effect of β-amylase in sweet potato on rice and rice gruel cooked with sweet potato, called imomeshi and imogayu, was studied by measuring the chemical properties and by sensory tests. A crude enzyme extract from sweet potato (ESP) was used as the cooking water. The amount of reducing sugars, especially maltose, in the rice and rice gruel cooked with ESP was larger than that when cooked with water alone. It was found that β-amylase in ESP degraded the starch in the rice grains to maltose. Rice gruel contained a larger amount of reducing sugars than cooked rice, regardless of the cooking water used. This seemed to result from differences in the time-course characteristics of the cooking temperature and from the ratio of cooking water to rice grains. The degradation of starch seemed to occur to the inner endosperm as well as to the outer layer. Sensory tests indicated significantly higher sweetness in both the cooked rice and rice gruel cooked with ESP than in the samples cooked with water.

View full abstract

The effects of moisture and temperature on the textural properties of products baked as cookies by gas oven heating (G) and combined microwave heating (Mw + G) were investigated. The ingredients were wheat flour, and various contents of butter and water. The higher starch gelatinization level of the oven-baked products with greatest water content showed stronger breaking properties and a wider range of brittle fracture. The higher starch gelatinization level of the products baked by combined microwave heating showed the maximum hardening peak at 40°C just before ductile fracture occurred. Both the test samples with the greatest fat content and highest testing temperature had the lowest breaking properties, but highest hardening ratio (Mw + G / G). These results show that microwave heating expanded the hardening range and promoted starch gelatinization.

View full abstract

The use of black soybeans and their eluate, which were expected to have functional properties, was investigated by adding to four types of Kowameshi, cooked glutinous rice, using different buffers: sample S, distilled water; sample A, pH3; sample B, pH5; sample C, pH7; and sample W, soybean-free. We compared the chemical and physical properties of the cooked rice samples, and we discuss the most suitable cooking conditions.
The textural properties of sample A containing black soybeans were significantly higher than those of sample S, while Kowameshi sample C was significantly softer (both p < 0.05). The total polyphenol content and radical scavenging activity of Kowameshi were significantly higher with samples A and B than with sample W, showing highly significant positive correlation (r = 0.93). The growth of bacteria was suppressed in samples A and B when compared with sample S. A weakly acidic condition (sample B, pH5) was suitable for rice cooking, the color tone of sample B being lighter than sample S. Although sample B was judged to be slightly acidic, no significant difference was evaluated in the taste. The preserved condition of sample B was better than that of sample S.

View full abstract

The foaming power, drainage ratio and dynamic viscoelasticity were measured for soy milk foam samples, and an image analysis was performed by microscopy to investigate the characteristics of microbubble (MB) foam in comparison with bamix (ba) foam. The foaming power of the MB foam samples was higher, while the drainage ratio was lower than that of the ba foam samples, particularly for those samples with lower viscosity and longer blowing time. The high G′ value (elastic modulus) contributed to the high foaming power and stability of the MB foam samples. The low tan δ value (loss tangent) for the MB foam samples shows greater solidity than the ba foam samples. The bubble size of the MB foam samples was greater, while the size distribution was lower than the ba foam samples. The longitudinal changes in bubble size distribution and growth ratio for the MB foam samples were smaller than for the ba foam samples. The lower kinetic constants for bubble size growth of the MB foam samples are related to the lower drainage ratio, showing this relationship to be one of the factors stabilizing the MB foam.

View full abstract

Spices sterilized by heating and gamma ray irradiation were subjected to an ESR analysis. The ESR spectrum of the spices was composed of a singlet at g = 2.0, this signal originating from an organic free radical. The intensity of the singlet signal of the spices increased linearly with microwave power and met threshold. The singlet signal intensity of the irradiated sample was the strongest. The relaxation times(T₁ and T₂) of the singlet signal were calculated, the times for the heated and irradiated samples being almost the same. A dilapidation process was necessary for analyzing lipid-rich spices. We conclude that the radical components of the heated and irradiated spices were the same.

View full abstract

The physiological advantage of rutin has put the focus on buckwheat as health-promoting food. The interaction between rutin and wheat gluten during the food-making process has been studied for steam-puffed bread. The gluten was blended with either tartary or common buckwheat flour in different proportions (0-10 wt%). Bread samples steamed for 15 min were examined for their texture, puff quality and antioxidative activities.
The bread samples from the blended tartary buckwheat flour clearly showed a harder texture than those from the common buckwheat flour. The puff of the tartary buckwheat bread revealed insufficient volume with rough and irregular foam, whereas that from common buckwheat flour showed sufficient volume with a smooth and fine foam. A stress-strain analysis showed that the tartary buckwheat flour tended to make hard and fragile puffs. This characteristic was not overcome by adding gluten. Blending the gluten with both types of buckwheat flour enhanced the peroxyl radical scavenging activity of the resulting bread.

View full abstract

The effects of the cooking and holding process on collagen, glyceride and sodium chloride penetration into Japanese radish and its firmness at the surface and inside were investigated.
A decrease in the weight of radish by cooking was observed. While glyceride and collagen scarcely penetrated it, sodium chloride rapidly did. The amounts of these constituents at the surface of radish significantly differed from those inside. The firmness at the surface of radish was higher than that inside when cooked at high temperature for a long time.
An increase in the weight of radish was apparent during cold- or hot-holding, and the sodium chloride content at the surface was similar to that inside. However, the glyceride and collagen contents at the surface significantly differed from those inside. While collagen penetrated the surface of radish during hot-holding, glyceride seemed to adhere to the surface during cold-holding. The holding process is therefore considered to affect the taste of boiled radish.

View full abstract

The “Hygiene Management Manual of Mass Cooking Facilities“ states that meat should be heated for at least one minute after reaching 75°C. However, overheating results in decreased cooking quality with oven-cooked foods. We investigated the possibility of using remaining heat to achieve the required heating time without affecting the quality of the cooked dish. Experiments were conducted on oven-cooked food by using cylindrical pork samples 50 mm in diameter and 15 mm thick. At an oven temperature setting of 270°C, heating for one minute after the internal temperature of the meat had reached 70°C enabled the internal temperature to be maintained at 75°C for 1 min from remaining heat. Heating these pork samples for 1 min after reaching 75°C by using remaining heat resulted in a significantly lower weight loss, lower breaking stress and greater tenderness. These findings indicate that using the residual heat was an effective way of maintaining the temperature at 75°C for 1 min when heating meat in an oven, depending on the temperature setting and weight of the meat.

View full abstract