Charles I. Onwulata

Keratin sponge/hydrogel: I. Fabrication and characterization

Keratin sponge/hydrogels formed by oxidation and reduction hydrolysis of US domestic fine- or coarse-grade wool exhibited distinctively different topologies, each with unique porous structure. These materials retained amino acids and microstructure as protein homologues of intact keratin. Amphoteric character was confirmed by differential dyeing with anionic and cationic dyes. Differential scanning calorimetry (DSC) provided evidence of molecular organization and the behavior of occluded moisture through measurements of glass transition, peak temperature, thermal degradation temperature, enthalpy of water removal, and degradation (Tg, Tw, ΔHw, Tt, and ΔHt). The absence of denaturation peaks indicated highly crosslinked molecular association. Low ΔHw indicated high plasticity and the ability to absorb and retain moisture. Small amplitude strain analysis rheology to measure storage or elastic modulus, G′, and shear loss or viscous modulus, G′′, as a function of applied strain characterized the sponge/hydrogels as covalently crosslinked networks. With viscoelastic properties typical of both liquids and solids, they maintained their structural integrity under strain.

Food powder delivery through a feeder system: effect of physicochemical properties.

Understanding the differences in delivery by feeders as affected by the powder properties is important for control but not much is written about this in the scientific literature. A regression analysis was undertaken to determine how to quantitatively integrate the effects of powder physicochemical properties on delivery through a twin-screw feeder. There was a linear relationship between powder delivery and screw speed over the entire operating range of the commercial twin-screw feeder test platform with the slope varying with the material delivered. Apparent particle density and particle size represented by both D50 and mode of a volume weighted particle size distribution (PSD) were found to have the most influence on delivery rate. Their effects could be quantitatively accounted for through a multiple regression equation for predicting the slope of the linear powder delivery curves.

Physical and chemical changes in whey protein concentrate stored at elevated temperature and humidity

In a case study, we monitored the physical properties of 2 batches of whey protein concentrate (WPC) under adverse storage conditions to provide information on shelf life in hot, humid areas. Whey protein concentrates with 34.9 g of protein/100g (WPC34) and 76.8 g of protein/100g (WPC80) were stored for up to 18 mo under ambient conditions and at elevated temperature and relative humidity. The samples became yellower with storage; those stored at 35 °C were removed from the study by 12 mo because of their unsatisfactory appearance. Decreases in lysine and increases in water activity, volatile compound formation, and powder caking values were observed in many specimens. Levels of aerobic mesophilic bacteria, coliforms, yeast, and mold were <3.85 log10 cfu/g in all samples. Relative humidity was not a factor in most samples. When stored in sealed bags, these samples of WPC34 and WPC80 had a shelf life of 9 mo at 35 °C but at least 18 mo at lower temperatures, which should extend the market for these products.