Influence des variants génétiques de la β-lactoglobuline et de la κ-caséine sur la composition du lait et son aptitude fromagère

Abstract

The influence of genetic polymorphism of beta-lactoglobulin (beta-Lg) and kappa-casein (kappa-Cn) on milk composition and cheese-making capacity was investigated in 83 Camembert-type cheeses, issued from 230 Friesian cows' milk. Eight genetic combinations between beta-Lg and kappa-Cn were studied; the chemical composition of milks, curds and wheys was assessed, as well as the results and retention percentages of components during cheese processing; a Formagraph was used to determine coagulation properties. The positive influence of BB-genotype for beta-Lg is essentially shown in casein rate in milk (+ 4.7% compared to the AA-genotype) and total nitrogen retention in curd (+ 2.9%). Beneficial effects of BB-genotype for kappa-Cn are greater, especially as regards clotting time and maximum curd firmness (respectively -24% and +37% compared to the AA-genotype); these are explained, among other factors, by a more favourable proteic composition. The result is a better recovery of chemical components in curds characterized by the BB-genotype for kappa-Cn. The A-B-genotype is in between. Discriminating factorial analysis shows that the effects of genetic variants of beta-Lg and kappa-Cn are additive. Genetic combinations have been graded according to their cheese-making quality, the BB/BB genotype for both proteins ranking first.