Daisuke Hamanaka

Three-Dimensional Numerical Modeling of Convective Heat Transfer During Shallow-Depth Forced-Air Drying of Brown Rice Grains

We describe here a three-dimensional (3D) numerical study of the convective thermal transfer during forced-air drying of brown rice grains with the inclusion of moisture evaporation. Three levels of temperature were tested across a range from 40 to 60°C. The objective of the study was to determine the temperature distributions in the drying chamber as well as the surface and intra-kernel temperature gradients during convective drying of rice grains. The numerical model was based on the Navier-Stokes equation for fluid flow and the Fouriers equation for heat transfer. Results of the numerical solution showed that temperature distribution in the air and brown rice grains during the early minutes of drying were significantly influenced by the direction of flow of the heated air. Air gaps between grains and at the periphery of the drying chamber affected the rate and direction of airflow. The temperature history of the rice grains showed variations at different levels within the layers of grains. Moreover, the stream of heated air showed regions with airflows eight times greater than the inlet air velocity.

The Relationship between Temperature and Respiration Rate of Green Asparagus

Temperature plays the most important role in post-harvest treatment and quality preservation of fresh horticultural products. Although many studies on the effect of temperature on respiration and quality have been carried out, there was little information on temperature dependence of respiration at wide range of temperature. The objectives of present study were to investigate the relationship between temperature and respiration rate of green asparagus at temperature from 0 to 50C during storage period. The results showed that the relationship between respiration rate and storage time at different temperatures could be expressed by an exponential equation. The initial respiration rate was higher because of harvest stress from growing of green asparagus and change in temperature. After three hours, the respiration rate of green asparagus decreased exponentially and then stabilized at a certain value except 50C due to remove harvest stress gradually. At 50C, respiration rate decreased lineally without equilibrating at a certain value because of harvest stress and inactivation of enzyme at higher temperature.

Lipid hydrolysis and genotype analysis of microbial distribution on rice treated with volatiles from fractionated propolis

Rice lipids are usually stable in the intact spherosomes in the cell. However, lipid membrane destruction by the phospholipase, physical injury or high temperature, initiates hydrolysis through the action of lipases. Further, microbial related lipolysis demands simultaneous antimicrobial and antioxidation control to stabilize lipids. Accordingly, the activity of volatiles from polar extract (AEPE), non-polar extracts (MCPEV and HEPEV) and crude sample (CRUPV) of propolis on rice bran and brown rice (Oryza sativa, hinohikari var.) quality was evaluated. We comprehensively investigated treatment effects on three major rice lipids and elucidated through microscopic morphological observation and genotype analysis of the 16S ribosomal DNA the fungal and bacterial distribution on the product respectively. Oleic, linoleic and palmitic acids composition in brown rice was affected by the treatments. HEPEV treated brown rice indicated lowest stabilization of the fatty acids, albeit marginally greater than the control. The stabilization strength was such: CRUPV> AEPEV> MCPEV>HEPEV. This pattern was not replicated regarding the composition of fatty acids in the bran layer only. The bacterial species of Bacillus genus were most predominant with Bacillus cereus persistently on all samples and Moraxella osloensis, Pseudomonas oleovorans, Sphingomonas paucimobilis, Xanthomonas campestris, Curtobacterium citreum, Curtobacterium flaccumfaciens and Aerococcus viridans affecting the samples discriminately. Penicillium spp. was the most dominant fungi and persisted in all the treatments. However, MCPEV and CRUPV treatments indicated the lowest species infestation numbers. Post treatment milling of pretreated grain revealed improved head rice for MCPEV and CRUPV treatments. Improved end product whiteness was only noticeable by MCPEV treatment.

Respiration Rate of Shiitake Mushroom in Modified Atmosphere Packages

Abstract The respiration rate of fresh shiitake mushroom (Lentinus edodes Sing.) was measured by pouch method at 0, 5, 15, 20 and 30°C. The results indicated that respiration rates were suppressed by decreasing O and increasing CO concentrations at 5, 15, 20 and 30°C. The lower oxygen limit (LOL) was mainly controlled by O concentration and little affected by CO concentration. Moreover, the LOL was increased with rise in temperature. For the multiple regression analysis, among three factors of the elapsed time, O and CO concentrations, the respiration rate was also affected by O concentration markedly.