Sugar (or more specifically sucrose) is one of the major food carbohydrate energy sources in the world. It is used as a sweetener, preservative, and colorant in baked and processed foods and beverages and is one of lowest cost energy sources for human metabolism. On an industrial scale, sucrose is produced from two major crops-sugarcane, grown in tropical and subtropical regions of the world, and sugar beet, grown in more temperate climates. Sugarcane, however, accounts for the vast majority of global sugar production. For much of the history of sugarcane production, sugar was a scarce and highly valued commodity. Sugarcane processing focused on extracting sucrose as efficiently as possible for the lucrative markets in the United Kingdom and Europe. The potential for the production of alternative products from sugarcane, however, has long been recognized. The key process by-products including bagasse, molasses, mud, and ash have all been investigated as a basis for the production of alternative products (Rao 1997, Taupier and Bugallo 2000). Sugarcane is believed to have originated in southern Asia, and migrated in several waves following trade routes through the Pacific to Oceania and Hawaii and through India into Europe. Sugarcane was introduced and spread through the Americas following the expansion by British, Spanish, and Portuguese colonies in the 15th and 16th centuries (Barnes 1964). While various methods of juice extraction and sugar production have been used over centuries to produce sugar, substantial innovations in sugar chemistry and processing technologies throughout the 18th and 19th centuries have formed the basis of modern sugar production methods (Bruhns et al. 1998). Dramatic improvements in processing efficiency, sugar quality, and automation and control characterized sugar processing throughout the 20th century.
The rheology of canola, sunflower, and soybean lecithin gum was examined by studying samples of different moisture contents produced in a batch evaporator (70°C, 0.1 atm). Soybean lecithin was found to have the lowest viscosity, approximately 10 poise (100 s −1 , 70°C), compared to canola and sunflower lecithin with viscosities of approximately 90 and 90,000 poise, respectively. The high sunflower viscosity was attributed to the presence of long-chain waxes. Lecithin gum was shown to change from a Bingham (water continuous phase) to a pseudoplastic (oil continuous phase) type fluid as the moisture content of the lecithin gum decreased. The viscosity maxima occurred between 6.9 and 19.3% moisture content (100 s −1 ), with the variation found to be related to the oil/water ratio of the system. Rheological results indicated that vertical scraped surface evaporator design could be optimized through the addition fluidizing of agents prior to the evaporator and/or increased heating at the evaporator outlet.Paper no. J8826 in JAOCS 76, 67-72 (January 1999).Commercial lecithin has traditionally been derived from soybeans owing to its high quality and low cost. Alternative commercial sources of lecithin have emerged with the increased production of sunflower and canola/rapeseed. The qualities of lecithin derived from these "soft" varieties of oilseeds have often been seen as inferior to that of soybean in respect to color, taste, and consistency (1,2). However, with effective quality control measures "soft" seed lecithin of comparable quality to existing commercial soy lecithin can be produced (Schneider, M., personal communication, 1997). The unique rheology of the lecithin-water system has lead to processing difficulties in the drying of lecithin. The rapid increase in viscosity that occurs when soybean lecithin gum contains 5-15% moisture (3) has further complicated thin film continuous drying. The rheological characteristics of soybean lecithin gum during drying are ill-defined in the literature. Even less is known about the rheological characteristics of sunflower and canola/rapeseed lecithin gum, apart from some processing difficulties noted in early attempts at production of rapeseed lecithin (4,5). This study focuses upon comparisons of lecithin gum rheology under steady state conditions and proceeds to derive practical engineering solutions to processing problems.De-oiled lecithin, even in low concentrations in aqueous solutions, exhibits considerable viscoelastic and non-Newtonian behavior (6), to a degree not normally associated with low molecular weight polymer chains. This results from the formation of an electrostatic gel arising from the electrostatic nature of the polar portion of the lecithin molecule, the charged nature of the micelles, and the large dipole moment and hydrogen bonding capacity of water (7). The importance of water in the creation of an electrostatic gel was underlined through the confirmation that de-oiled lecithin in a hydrocarbon solvent exhibited Newtonian characteristics and the solu...
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