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

Process analysis of superheated steam pre-treatment of wheat straw and its relative effect on ethanol selling price

Existing bioethanol operations rely on starch-based substrates, which have been criticized for their need to displace food crops in order to be produced. As an alternative to these first generation biofuels, the use of agricultural residues is being considered to create more environmentally-benign second generation, or cellulosic biofuels. Recalcitrance of these substrates to fermentation requires extensive pre-treatment processes, which often consume more energy than can be extracted from the ethanol that they produce, so one of the priorities in developing cellulosic ethanol is an effective and efficient pre-treatment method. This study examines the use of superheated steam (SS) as a process medium by which wheat straw lignocellulosic material is pre-treated. Following enzymatic hydrolysis, it was found that 47% of the total glucose could be liberated from the substrate, and the optimal conditions for pre-treatment were 15 min in hot water (193 kPa, 119˚C) followed by 2 min in SS. Furthermore, a preliminary relative economic analysis showed that the minimum ethanol selling price (MESP) was comparable to that obtained from steam explosion, a similar process, while energy consumption was 22% less. The conclusion of the study is that SS treatment stands to be a competitive pre-treatment technology to steam explosion