GLASS TRANSITION AND TEXTURE IN A TYPICAL SPANISH CONFECTIONERY PRODUCT: XIXONA TURRON

The water sorption isotherm at 25C and glass transition temperature were determined in a typical Spanish confectionery product (Xixona turrón), as well as in the fat-free product. The samples were equilibrated at water activity levels from 0.113 to 0.755. The GAB and BET models were fitted to sorption data and the monolayer moisture contents were 2.8 and 6.0 (g of water/100 g of dried sample) for turrón and fat-free turrón, respectively. The sorption data indicate a lipid interaction with hydrophilic constituents. The analysis of the glass transition temperature (Tg) of the product as a function of its moisture content is used to determine the critical water content (CWC) at which the product becomes rubbery, at a determined temperature. From sorption isotherm at the same temperature (25C) we can also determine the critical water activity (CWA). The plasticizing effect of water in Xixona turrón can be modeled by the Gordon and Taylor equation. The fat also has a plasticizing effect, which is more obvious at low water content. A Texture Profile Analysis (TPA) was performed on samples with different moisture contents. Only samples with a moisture content lower than CWC showed fracturability, due to its glassy state. In the rubbery state hardness, gumminess and chewiness decrease when water content increases. Elasticity and cohesiveness increase in line with water content, more strongly for those moisture levels which are higher than BET monolayer value.     

Nutritional Improvement of Sorghum by Fermentation

A natural lactic fermentation of ground grain sorghum produced significant increases (P < 0.001) in available lysine/leucine, isoleucine, and methionine. The protein quality, expressed as relative nutritive value, increased significantly (P < 0.001) as a result of fermentation. Niacin and thiamin increased significantly (P < 0.001) and riboflavin also increased (P < 0.05) during the fermentation. Protein and carbohydrate appeared to be more available after the fermentation than before the fermentation. Although the fermentation produced increased availability of nutrients, it did not produce change in the proximate analyses.     

FLOW PROPERTIES OF ORANGE DIETARY FIBER SUSPENSIONS

The flow behavior of 7–20% orange dietary fiber (DF) suspensions at 15–65C was most adequately described by the simple power law model. The effect of the temperature on the apparent coefficient of viscosity (η_app) followed an Arrhenius-type relationship. The flow activation energy (E_a) was in the range 3.0–14. 7kJ/mol, depending on the concentration. The η_app increased exponentially with concentration within the temperature range studied. The combined effect of temperature and concentration on the η_app could be represented by an exponential equation. In all the cases, the effect of concentration on η_app was more pronounced than that of the temperature.