Roberto A. Buffo

Factors affecting the emulsifying and rheological properties of gum acacia in beverage emulsions

Abstract Gum acacia, a natural hydrocolloid, is extensively used as an emulsifier/stabilizer in beverage emulsions. Factors that may affect emulsion formation, emulsion stability and viscosity of the emulsion concentrate were studied to assess their significance, including proximal composition of the gum (protein content and mineral content), gum processing prior to emulsion preparation (pasteurization and demineralization), and pH of the dilute emulsion. Protein content was not related to emulsion stability, whereas minerals decreased stability presumably due to an electrostatic screening effect. Both pasteurization and demineralization favored stability, most likely by promoting protein unfolding and eliminating the screening effect, respectively. Emulsions were less stable at pH=2.5 than at higher pH levels (4.5 and 5.5). There was a significant difference between the two gum species studied (Senegal and Seyal) in their sensitivity to these treatments. The viscosity of the emulsion concentrate was decreased by pasteurization and increased by demineralization. Protein load at the O/W interface and thickness of the adsorbed layer of emulsifier were not related to emulsion stability. The most important colloidal interactions in dilute beverage emulsions are van der Waals, electrostatic and polymeric steric.

Films from Laboratory-Extracted Sorghum Kafirin

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Modeling the rheology of concentrated beverage emulsions

Abstract A number of theoretical equations were tested against experimental measurements of viscosity of concentrated beverage emulsions in order to model their rheology. Seven samples of gum acacia were used as emulsifiers. All emulsions presented a Newtonian behavior. Best fit corresponded to the Einstein equation, both in its original form and expanded to include short-range colloidal forces. Oil droplets were assumed to be rigid spherical particles, not significantly affected by Brownian motion due to the viscosity of the bulk phase, and subjected to colloidal interactions of limited range.

Relationships among grain sorghum quality factors

ABSTRACT Correlations among grain sorghum quality factors (proximate composition, physical properties, and water absorption properties) were evaluated. Samples of 46 commercial hybrids (24 and 22 from crop years 1993 and 1994) were analyzed for starch, protein, crude free fat, test weight, absolute density, 1,000 kernel weight, percent kernel abraded, water absorption index, initial water absorption rate, and moisture saturation point. Test weight, absolute density, and percent kernel abraded were positively correlated among themselves (r > 0.5). Protein was negatively correlated with both test weight and absolute density (r < -0.5), while moisture saturation point showed negative correlations with test weight, absolute density, 1,000 kernel weight, and percent kernel abraded (r < -0.4). Principal component factor analysis through the covariance matrix explained 95% of the total variation of quality factors among hybrids (two factors), and, through the correlation matrix, 85% of the total variation (five ...

Influence of time–temperature treatments on the emulsifying properties of gum acacia in beverage emulsions

Abstract Response surface was used to evaluate the significance of time–temperature treatments on gum acacia solutions with respect to the stability of gum acacia-based dilute beverage emulsions. Treatments ranked from a minimum of pasteurization (30 min at 62.5°C) to a maximum just before inducing protein precipitation from the gum (90 min at 100°C). Heat treatment improved emulsion stability to a greater extent in Acacia seyal than Acacia senegal samples, with optimum values around 80°C and 60 min for both species. Response surface was statistically significant in Seyal but not in Senegal.

Shelf‐life and mechanisms of destabilization in dilute beverage emulsions

Mechanisms of destabilization and kinetic parameters of shelf-life in dilute beverage emulsions were investigated at six different temperatures. Close fit of the Arrhenius equation to emulsion breakage time indicated the occurrence of similar mechanisms throughout the temperature range and validated accelerated shelf-life tests at higher temperatures. Creaming increased by a factor of 10 between the lowest (4 °C) and highest (55 °C) temperatures. Ostwald ripening was highly significant and more important than coalescence in influencing emulsion stability. Copyright

Optimization of Sulfur Dioxide and Lactic Acid Steeping Concentrations for Wet-Milling of Grain Sorghum

Influence of sulfur dioxide (SO2) and lactic acid (LA) on grain sorghum steeping efficiency in terms of wetmilling ncharacteristics was investigated using response surface analysis. Tested ranges of concentrations in steeping nwater were 0.050 to 0.278% and 0 to 0.282% for SO2 and LA, respectively. Measured wet-milling variables were steeping nsolids yield, starch yield, protein yield, fiber/germ yield, starch recovery, protein recovery and protein content of starch. nStarch and protein recovery values were highly correlated to each other (r = 0.74). Correlations of these attributes with nfiber/germ yield were strongly negative (r = –0.96 and r = –0.70 for starch and protein recovery, respectively). A model ncomprised of the linear and quadratic terms of SO2 and LA concentrations and the interaction between SO2 and LA was nfitted to data for each dependent variable. The model satisfactorily explained starch yield (R2 = 0.84), starch recovery n(R2 = 0.85) and fiber/germ yield (R2 = 0.71). Lactic acid was the factor that consistently influenced all significant nsurfaces (P < 0.01 for starch yield and starch recovery, and P < 0.05 for fiber/germ yield). Maximum stationary points for nstarch yield and recovery, and a minimum stationary point for fiber/germ yield were observed at similar combinations of nSO2 (0.191-0.209%) and LA (1.387-1.415%) concentrations.