Kinetics of Formation and Functional Properties of Conjugates Prepared by Dry-State Incubation of β-Lactoglobulin/Acacia Gum Electrostatic Complexes

• Published in: Journal of agricultural and food chemistry Vol. 53; no. 23; pp. 9089 - 9099
• Main Authors: Schmitt, Christophe, Bovay, Claudine, Frossard, Philippe
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 16.11.2005
• Subjects: Acacia; Biological and medical sciences; Chemical Phenomena; Chemistry, Physical; Chromatography, High Pressure Liquid; dry-state incubation; Elasticity; Electrophoresis, Polyacrylamide Gel; electrostatic interactions; foaming capacity; foaming properties; Food industries; functional properties; Fundamental and applied biological sciences. Psychology; Gum Arabic - chemistry; gums; heat treatment; Hydrogen-Ion Concentration; Kinetics; lactoglobulins; Lactoglobulins - chemistry; Milk and cheese industries. Ice creams; reaction kinetics; Solubility; Static Electricity; Viscosity; Incubation; Foaming; β-Lactoglobulin; Solubility; Polymerization; Dry-state incubation; Properties; Milk protein; reaction kinetics; Leguminosae; Dicotyledones; Angiospermae; Acacia; foaming propertie s; Spermatophyta; Kinetics; Whey protein; interfacial properties; Gum; protein polymerization
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf051630t

The formation of conjugates between β-lactoglobulin and acacia gum based on electrostatic complexes formed at pH 4.2 was investigated upon dry-state incubation for up to 14 days at 60 °C and 79% relative humidity (RH). By means of SEC-HPLC and RP-HPLC, it was shown that the β-lactoglobulin incubated alone was able to form polymers with molecular masses higher than 200 kDa until 50% of the initial monomeric protein disappeared after 14 days. In the presence of acacia gum at initial protein to polysaccharide weight mixing ratios of 2:1 and 1:2, only 35% of the initial β-lactoglobulin monomers disappeared after 14 days. Using RP-HPLC, an apparent reaction order of 2 was found for the disappearance of monomeric β-lactoglobulin both in the presence or absence of acacia gum. However, the reaction rate was faster in the absence of acacia gum. SDS−PAGE electrophoresis with silver staining confirmed the formation of β-lactoglobulin/acacia gum conjugates. The solubility curves of the incubated β-lactoglobulin showed a minimum around pH 4−5. By contrast, the minimum of solubility of the β-lactoglobulin/acacia gum incubated mixtures shifted to lower pH values compared to initial mixtures. The conjugates exhibited higher foam capacity than the incubated protein as well as lower equilibrium air/water surface tension. Conjugation at ratio 1:2 led to increased interfacial viscosity (300 mN s m-1 at 0.01 Hz) compared to β-lactoglobulin alone (100 mN s m-1 at 0.01 Hz), but similar interfacial elasticity (30−40 mN m-1). The foam capacity of the conjugates was significantly higher than that of the incubated β-lactoglobulin as well as foam expansion and drainage time, especially at pH 5.3, i.e., higher than the pH of formation of the conjugates. Keywords: Dry-state incubation; reaction kinetics; protein polymerization; solubility; interfacial properties; foaming properties