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Laccase, an oxidative enzyme, was used to catalyze the hetero and homo covalent conjugation between ferulic acid in sugar beet pectin (SBP) and tyrosine in heated β-lactoglobulin (H_BLG). The conjugation of SBP and H_BLG was confirmed by peak position using size exclusion chromatography, multi angle laser light scattering, refractive index, and UV detection. H_BLG, pre-treated with laccase, eluted at an earlier volume with greater UV280 absorbance than non-laccase treated dispersions. Tyrosine decreased in H_BLG that contained laccase treated SBP samples. Heat enhanced exposure of tyrosine in BLG and improved conjugation with SBP by laccase. H_BLG·SBP conjugates with laccase had improved solubility than laccase untreated dispersions at pH values near the isoelectric point of BLG. [ABSTRACT FROM AUTHOR]

Highlights: [•] FT-IR identified differences in methyl contents between HPMCs. [•] The relative crystallinity of HPMC is dependent on the hydroxypropyl content. [•] The hydroxypropyl content is not an indicator of the percentage of free water. [•] The stress relaxation in weak HPMC gels depends on methyl content. [ABSTRACT FROM AUTHOR]

A rheological study was carried out to evaluate formulations of test dispersions and gels of high methoxyl pectins (HTHMP) obtained at different conditions from husk tomato waste ( Physalis ixocarpa Brot.). The effect of extraction agent (hydrochloric acid or citric acid), blanching time (10 or 15 min) and extraction time (15, 20 or 25 min) on the rheology of the tested samples was evaluated. Flow behavior and activation energy were evaluated on the test dispersions, while ( E a ) frequency sweeps, temperature sweep, creep-recovery test and penetration test were performed on the gels. HTHMP dispersions showed shear thinning flow behavior, while showing a good fit to Cross model. Extraction agent, blanching time and extraction time did not have effect on Cross parameters (η z , η∞, C, and m). E a decreased as blanching time and extraction time increased. Frequency sweeps revealed high dependence on frequency for both G’ and G”, while temperature sweeps (25- 95 °C) showed thermostable husk tomato pectin gels. Hydrocloric acid (HCl) extracted pectin gels showed stronger structure than citric acid (CA) gels. [ABSTRACT FROM AUTHOR]