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Lactoprotein Genetic Variants in Cattle and Cheese Making Ability

Johann Buchberger1 and Peter Dovč2*


1
Dairy and Food Research Center Weihenstephan, Weihenstephaner Berg 5, D-85354 Freising

2Department of Animal Science, Biotechnical Faculty, University of Ljubljana, Groblje 3, SI-1230 Domžale, Slovenia

Article history:

Received January 19, 2000
Accepted May 2, 2000

Key words:

bovine lactoproteins, genetic variants, milk composition, cheese making ability

Summary:

Cheese making ability of milk is associated with high contents of protein, casein (CN) and fat, high casein number, short rennet coagulation time (RCT), high curd firmness (CF) and with a high cheese yield. For the four CN loci, as well as for the β-lactoglobulin (LG)- and α-lactalbumin (LA) locus, more than 60 genetic variants have been observed. However, most of these variants have not yet been investigated with regard to their cheese making ability. In Holstein Friesian cows κ-CN BB is associated with a higher protein and casein content of milk than κ-CN AA. However, in Simmentals and in Brown Cattle this association is not so clear; a higher fat content of milk seems to be related to β-LG BB when compared with β-LG AA. In many publications β-LG BB also showed a higher casein content than β-LG AA. All publications referring to the casein number report that milk containing β-LG BB has an approximately 3 % (absolute) higher casein number than milk containing β-LG AA. Regarding the genotypes αs1-CN BC and CC contradictory results for the RCT and CF values have been published when compared with αs1-CN BB milk. β-CN BB showed in all publications the shortest RCT among all β-CN genotypes, whereas the reported results for CF of this genotype compared with the types A1A2 or A2A2 are conflicting. From the majority of the published data it may be concluded that milk containing κ-CN BB has significantly shorter RCT and higher CF than κ-CN AA milk. All rare genotypes at the κ-CN locus, such as AC, BC, AE, BE and EE, had worse RCT values than -CN BB milk. CF of -CN genotypes increases in the order AE/AA<AB/AC<BC/BB. In most investigations involving Parmiggiano-Reggiano, Cheddar and other cheese varieties higher yields of cheese were found, ranging from 0.3 to 10 %, in favour of κ-CN BB compared with κ-CN AA. Due to the higher casein number associated with β-LG BB, higher yields of cheese were reported in literature (range 1 to 10 %) for this genotype than for β-LG AA. In summary, κ-CN B and β-LG B are the most advantageous variants with respect to cheese making ability. However, in most publications attention was focused on the effects of a single milk protein locus but due to the tight linkage between the casein loci effects of haplotypes should be studied more extensively.



*Corresponding author:           peter.dovc@bfro.uni-lj.si
                                               ++386 (0)1 7241 005

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