The optimum cooking conditions for shark skin were examined after pressure heating in various solutions in order to expand its utilization as a food. Shark skin was cooked in either a 0.2% potassium carbonate solution, 1% acetic acid solution or deionized water under pressure. The maximum force was evaluated for breaking strength as measured by a rheometer. The shark skin cooked in either solution resulted in the maximum force of the cooked skin decreasing rapidly up to 5 minutes of cooking, the decrease being greatest in the 1% acetic acid solution. Shark skin cooked in either solution became softer, and protein from the skin was eluted into the solution. The softening of the shark skin that occurred during cooking can probably be explained by this elution of protein and by the consequent change in the sharkskin structure. Heating the shark skin under pressure in either solution was effective in respect of the texture and cooking time.
The effects of micro-crystalline cellulose (MCC) on the gelatinization and retrogradation of cornstarch gel were studied by DSC, uniaxial compression and dynamic viscoelastic measurements. The total concentration of cornstarch and MCC was fixed at 15 wt%. The values for the fracture stress of cornstarch gel samples with MCC were less than those without MCC (control). The retrogradation rates for the gel samples with MCC were less than those for the control. These lower values were attributed to a decrease in the cornstarch concentration. Although MCC did not interact directly with cornstarch, the value for the elastic modulus of the gel samples with MCC was greater than that for the control. The rigid structure of MCC may have contributed to a strong network for a small deformation. Moreover, the elastic modulus of the gel samples with MCC was less temperature dependent than that of the control, the addition of MCC therefore making the gel more heat resistant.
The effects of the concentration of sugar syrup on the quality and preference for Italian meringue were investigated. Syrup with different concentrations of sugar was added to Italian meringue. The heating temperature and concentration of the syrup were set as A, 105°C and 89.0wt%; B, 110°C and 90.1wt%; C, 120°C and 91.5wt%; and D, 130°C and 92.7wt%. The quantity of liquids separating from Italian meringue decreased with increasing concentration of the sugar syrup. The stability of the meringue increased when the concentration of the syrup was higher than B, while syrup concentration. C or D resulted in extremely high stability even after 24 hours. The compressive stress and cohesiveness of the Italian meringue also increased with increasing concentration of the sugar syrup. The sensory evaluation scored syrup concentrations C and D highest for the preferred meringue, while syrup B was evaluated highly for baked meringue.
The frying time of prepared frozen foods was judged by their surface colors, and their center temperatures were not researched. In our project, we investigated the center temperatures of the frozen croquettes and meatballs during deep-frying, and aimed to find an appropriate frying method to meet the adequate surface color and the proper inside temperature. When the samples were fried at commonly-used high oil temperature, the heat did not sufficiently conduct to the center parts even after the surface colors were adequate. This tendency remarkably appeared in the meatballs that had no batter. The best frying method with meatballs was to fry them at a low temperature in the early stage, and then switch the oil to a higher level when the samples' center reached 0°C. As a result, the final center temperatures were high enough with the adequate surface colors and their harder and brittle textures were preferred.
We evaluated the effects of cooking conditions and hot -holding to tenderize chicken, based on the action of ginger protease on collagen which occurs only in the telopeptide region under acidic conditions and not in the triple-helical region. The acid-soluble and pepsin-solubilized collagen (ASC and PSC) contents in the chicken samples decreased with cooking, but the amount of insoluble collagen (ISC) increased. Hot-holding the cooked chicken samples decreased the total amount of collagen, as did ginger juice when added to the heated samples. This was probably because ginger protease acted on the thermally denatured regions of collagen with an irregular structure resulting from cooking and hot-holding. The addition of ginger juice significantly decreased the shear force of the cooked chicken samples in comparison with the other samples without added ginger juice.
The oxygen radical absorbance capacity (ORAC) was evaluated for arabushi-dashi and karebushi-dashi prepared at various temperatures for various times. The ORAC value for both types of dashi increased with increasing temperature, the highest degree of extraction being at 100°C for 30 min. Arabushi-dashi showed a higher ORAC value than karebushi-dashi under all conditions. The DPPH radical scavenging activity behaved in a similar manner to the ORAC value, these values being well correlated. The DPPH radical scavenging activity and ORAC value were each evaluated for niboshi-dashi, kombu-dashi, and shiitake-dashi. Niboshi-dashi had the lowest value, while shiitake-dashi had the highest value among the three types of dashi. The DPPH radical scavenging activity and ORAC value for these three types of dashi and katsuo-dashi were well correlated.