Kwang-Il Kim

Effect of Liposome-coated Hemicellulase on the Tenderization of Burdock

The elderly or patients with masticatory disturbance and deglutition dysfunctions, may have difficulty in chewing or biting foods with a hard texture. Thus, softening of the texture of foods using hemicellulase immobilized by the nanoencapsulation technique was examined in this study. Burdock was cut into cylindrical-shaped samples, which were immersed in distilled water and non-coated or coated enzymes for 48 h at 4 o C. The hardness of the treated samples decreased compared to the control. Microstructural observations revealed that the cells in the non-coated burdock were destroyed after 24 h. From the point of view of enzyme activity, the initial activity of the non-coated enzymes was higher than that of the coated enzymes. However, the enzyme activity was not significantly affected by the immersion time. Therefore, it appears that the encapsulation technique for enzymes may be useful for softening the texture of foods.

Quality Characteristics of Beef by Different Cooking Methods for Frozen Home Meal Replacements.

Blanching beef for use in home meal replacements (HMR) is an important process that determines the final quality of the beef after the cooking process. Thermal pretreatment also minimizes the change in quality during the main cooking process or storage. In this study, beef samples were washed and sliced, then treated by immersion in boiling water (1-10 min), steaming (1-10 min), or pan-frying in oil (30-240 s). The color after each thermal treatment showed higher L* and b* values and lower a* values compared with the raw beef, except for the pan-frying thermal treatment. The total color difference (∆E) and pH value were significantly increased by panfrying (p<0.05). There was no significant difference in the shear force of the beef samples, except for the sample pan-fried for 210 s. The nutritional content of beef was measured as the moisture, protein, fat, and ash contents, which were 69.96, 16.64, 3.49, and 1.13%, respectively, in raw beef. After thermal treatment, the crude protein and fat contents were increased, whereas the moisture and ash contents decreased. The mineral content, including Na, Mg, Fe, and Ca was highest after pan-frying. The heat treatment decreased microorganisms in all the samples. The total bacteria count in raw beef was 4.5-4.7 Log CFU/g, whereas the bacteria count decreased to 2.2-2.8 Log CFU/g after blanching. Thermophilic bacteria, coliform, mold, and yeast not detected in any thermally treated sample.

Effects of Various Thermal Treatments on Physicochemical and Nutritional Properties of Shiitake Mushrooms

In the food industry, thermal treatment is an important process for extending shelf-life of foods. However, heating process affects the physicochemical, nutritional, and microbial properties of foodstuff such as color, texture, pH, and proximate compositions. This study was conducted to select an optimal thermal treatment by observing physicochemical, nutritional, and microbial effects of shiitake mushrooms with different thermal treatment methods. Shiitake mushrooms were washed and sliced equally (5 cm×0.5 cm×0.5 cm) and then heat-treated by three methods. Samples were heated in 100°C boiling water, steamed for 10 min, or pan fried at 130°C for 4 min. Total color difference values showed significantly increasing tendency with treatment time. For pH values, boiling water-treated mushrooms showed increasing tendency according to increased thermal treatment. For the results of hardness, boiling water or pan frying-treated mushrooms showed reduced tendency within 1 min. In the case of steam-treated mushrooms, hardness values were maintained for 1 min. Organic acid contents of steam-treated sample showed the lowest value among treatments. For microbial counts, steam-treated samples for 3 min showed the lowest value. Consequently, the results of this study suggest that steam treatment could be the optimal thermal treatment to minimize quality loss of shiitake mushrooms.