Protein Beverage vs. Protein Gel on Appetite Control and Subsequent Food Intake in Healthy Adults

The objective of this study was to compare the effects of food form and physicochemical properties of protein snacks on appetite and subsequent food intake in healthy adults. Twelve healthy subjects received a standardized breakfast and then 2.5 h post-breakfast consumed the following snacks, in randomized order: 0 kcal water (CON) or 96 kcal whey protein snacks as beverages with a pH of either 3.0 (Bev-3.0) or 7.0 (Bev-7.0) or gels as acid (Gel-Acid) or heated (Gel-Heated). In-vitro study showed that Bev-3.0 was more resistant to digestion than Bev-7.0, while Gel-Acid and Gel-Heated had similar digestion pattern. Appetite questionnaires were completed every 20 min until an ad libitum lunch was provided. Post-snack hunger, desire to eat, and prospective food consumption were lower following the beverages and gels vs. CON (all, p < 0.05), and post-snack fullness was greater following the snacks (except for the Bev-3.0) vs. CON (all, p < 0.05). Gel-Heated treatment led to lower prospective food consumption vs. Bev-3.0; however, no other differences were detected. Although all snacks reduced energy intake vs. CON, no differences were observed among treatments. This study suggested that whey protein in either liquid or solid form improves appetite, but the physicochemical property of protein has a minimal effect.

Formation of protein-rich coatings around lipid droplets using the electrostatic deposition method

The purpose of this study was to determine whether protein-rich coatings could be formed around lipid droplets using an electrostatic deposition method. These coatings were assembled using two methods: (i) beta-lactoglobulin was adsorbed to beta-lactoglobulin-pectin-coated lipid droplets; (ii) beta-lactoglobulin-pectin complexes were adsorbed to beta-lactoglobulin-coated lipid droplets. Composite particles, consisting of lipid droplets with protein-rich biopolymer coatings, could be formed using both approaches (e.g., at pH 4, the protein surface load could be increased from 3 to 59 mg m(-2)). These composite particles could be made small (d < 500 nm) and relatively stable to gravitational separation at certain protein concentrations. Nevertheless, aggregation and sedimentation occurred at sufficiently high protein concentrations because of charge neutralization. The composite particles remained stable after they were heated above the thermal denaturation temperature of the globular proteins at pH 4. When the heated composite particles were adjusted to pH 7, where beta-lactoglobulin and pectin are both negatively charged, some of the pectin and beta-lactoglobulin became detached from the droplet surfaces but the protein surface load was still higher than in a nontreated sample. These composite particles may be useful for increasing the protein concentration in biopolymer coatings surrounding lipid droplets, which potentially has practical applications in the food industry (e.g., in protecting omega-3 oils from oxidation or in developing natural weighting agents).

Mesostructure of fibrillar bovine serum albumin gels

The mesostructure of bovine serum albumin (BSA) at low pH was investigated. Rheological measurements were performed to determine the critical percolation concentration (c(p)). A decreasing c(p) with increasing ionic strength was found. Fibrils with a contour length of about 100-300 nm were found using transmission electron microscopy. The measured conversion of monomers into fibrils was independent of ionic strength (0.20-0.30 M). Dilution of BSA samples showed that the aggregation process is reversible and that there exists a critical concentration for the self-assembly of BSA. We explain the decreasing c(p) with increasing ionic strength in terms of an adjusted random contact model.