latent heat of vaporization for selected foods and crops

Cenkowski, S., Jayas, D.S., and Hao, D. 1992. Latent heat of vaporization for selected foods and crops. Can. Agric. Eng. 34:281-286. The equation for latent heat of vaporization was estab lished based on published equilibrium moisture content curves for main crops and selected foods. For moisture content (mc) above 0.2 db, there is little difference between the heat of vaporization from the grain kernels, hfg*, and that of free water, hfg. Below 0.2 db, this difference increases significantly for grains such as corn and rice. For the other grains (wheat, barley, bean, peanut kernel, soybean, sorghum), the ratio of hfg*/hfg increases at moisture contents below 0.12 db. There is a significant difference in hfg*/hfg results between durum wheat and soft or hard wheat. The latent heat of vaporization of free water is not significantly different from the latent heat of vaporization of water for celery, cloves, and eggs above 0.10 mc db and above 0.15 mc db for chamomile tea and horse radish. The hfg*/hfg ratios for starchy gels are 1.35 to 1.50, which were the highest of the tested crops and foods, for the moisture range between 0.11 and0.16db

Effects of Milling and Cooking Processes on the Deoxynivalenol Content in Wheat

Deoxynivalenol (DON, vomitoxin) is a natural-occuring mycotoxin mainly produced by Fusarium graminearum, a food-borne fungi widely distributed in crops and it is one of the most important mycotoxins in wheat and wheat-based foods and feeds. DON affects animal and human health causing diarrhea, vomiting, gastro-intestinal inflammation, and immunomodulation. Since the rate of the occurrence of DON in wheat is high, effective procedures to remove or eliminate DON from food products is essential to minimize exposures in those who consume large amounts of wheat. Cleaning prior to milling reduced to some extent the concentration of DON in final products. Since DON is distributed throughout the kernels, with higher content in the outer skin, milling is also effective in reducing the DON levels of wheat-based foods if bran and shorts are removed before thermal cooking. DON is water-soluble and cooking with larger amounts of water lowers DON content in products such as spaghetti and noodles. During baking or heating, DON is partially degraded to DON-related chemicals, whose toxicological effects are not studied well. This paper reviews the researches on the effects of milling and cooking on the DON level and discusses the perspectives of further studies

Dynamics of drying bentonite in superheated steam and air as a model food system. Canadian Agricultural Engineering

Dynamics of drying bentonite in superheated steam and air as a model food system. Can. Agric. Eng. 38:305-310. The objective of this research was to compare temperature patterns, drying rates, and diffusivities of bentonite as a food model with a high concentration of solids dried in hot air and superheated steam at 160°C. In our preliminary investigations on the drying of liquid food droplets in hot air and superheated steam, spherical samples of 13.5 mm in diameter were prepared from chemically stable bentonite paste. In superheated steam drying, bentonite samples reached the saturation temperature for steam (100°C) after the first minute of drying. During this period the samples gained approximately 0.1 kglkg dry basis (db) of moisture, due to condensation of water on the surface of the sample. In air drying at 160°C, the temperature of a similar sized sample gradually increased to a wet bulb temperature of 80°C over a 10 min period. The drying rate in the superheated steam was higher by 8 to 10% than in the 160°C air in the initial stage of drying. However, this situation reversed when samples reached the falling rate-of-drying stage. For this period and below moisture content of 0.10 kglkg db, the overall diffusion coefficient was 50 to 80% higher for samples dried in the 160°C air than in superheated steam of the same temperature