Interactions in casein micelle – Pea protein system (part I): Heat-induced denaturation and aggregation

International audienceThe aim of this work was to investigate the heat-induced interactions between pea proteins (vicilin 7S or legumin 11S enriched-fractions) in admixture with suspended casein micelles (SCM), at weight protein ratio of 1:1 and pH 7.1. The single-protein samples and mixtures thereof were prepared at concentrations of 18 and 36 mg(protein)/g(sample), respectively, then heated from 40 to 85 degrees C and incubated for 0-60 min. As compared to single-protein samples, differential scanning calorimetry (DSC) data indicated that the denaturation temperature of pea proteins increased of about 4 degrees C in the presence of SCM. Heat-induced change in protein composition of the soluble (SP) and micellar (MP) phases from centrifuged SCM pea protein mixture was assessed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and densitometry. Likewise SP was analyzed by size-exclusion chromatography (SEC-HPLC). While pea legumin 11S and vicilin 7S oligomers were markedly sedimentable in MP from their respective unheated mixture, thermal denaturation and protein aggregation (>= 75 degrees C) resulted in increasing levels of dissolved pea proteins in SP. Heating of the SCM legumin mixture (85 degrees C, 15-60 min incubation) resulted in the dissociation of the legumin subunits L-alpha beta into acidic Le and basic L-beta polypeptides, yielding in comparable amounts soluble and insoluble disulfide-bonded aggregates, respectively. In contrast in the SCM vicilin mixture, the heat-denatured vicilin polypeptides in a temperature range of 70-80 degrees C produced in majority soluble and non-covalent aggregates. Though the heat-induced interactions between pea proteins were altered in the presence of micelles, caseins would not be involved into pea proteins aggregation

Caractérisation de laits de juments comtoises. Aptitude à la coagulation enzymatique et à la filtration membranaire . Fabrications de produits fromagers

Comtoise mare milk produced in three different breeds from Franche-Comté were assessed for their physico-chemical, biochemical and microbiological content along the lactation 2008. Exploratory trials were conducted also to determine the behaviour of the milk when submitted to fitlration, enzymatic coagulation and cheese manufacture. Le lait de jument Comtoise produit dans 3 élevages de Franche-Comté a fait l'objet d'une caractérisation physico-chimique, biochimique et microbiologique au cours de la saison de production 2008. Des essais technologiques exploratoires incluant l'aptitude à la filtration membranaire et à la coagulation enzymatique, ainsi que la fabrication de fromages selon 2 types de technologie ont été réalisés