Effect of β-lactoglobulin A and B whey protein variants on cheese yield potential of a model milk system

Abstract

Cheese yield mainly depends on the amount and proportion of milk constituents; however, genetic variants of the proteins present in milk may also have an important effect. The objective of this research was to study the effect of the variants A and B of β-lactoglobulin (LG) on cheese yield using a model system consisting of skim milk powder fortified with different levels of a mixture containing α-lactalbumin and β-LG genetic variants (A, B, or A-B) in a 1:2 ratio. Fortified milk samples were subjected to pasteurization at 65°C for 30min. Miniature cheeses were made by acidifying (pH=5.9) fortified milk and incubating with rennet for 1h at 32°C. The clot formed was cut, centrifuged at 2,600×g for 30min at 20°C and drained for determining cheese yield. Cheese-yielding capacity was expressed as actual yield (grams of cheese curd per 100g of milk) and dry weight yield (grams of dried cheese curd per 100g of milk). Free-zone capillary electrophoresis was used for determining β-LG A or B recovery in the curd during rennet-induced coagulation. The presence of β-LG variant B resulted in a significantly higher actual and dried weight cheese yield than when A or A-B were present at levels ≤0.675% of whey protein (WP) addition. Results of free-zone capillary electrophoresis allowed us to infer that β-LG B associates with the casein micelles during renneting, as shown by an increase in the recovery of this variant in the curd when β-LG B was added up to a maximum at 0.45% (equivalent to 0.675% WP). In general, actual or dried weight cheese yield increased as WP addition was increased from 0.225 to 0.675%. However, when WP addition ranged from 0.675 to 0.90%, a drastic drop in cheese yield was observed. This behavior may be because an increase in the aggregation of casein micelles with a concomitant inclusion of whey protein in the gel occurs at low levels of WP addition, whereas once the association of WP with the casein micelles reach a saturation point at addition levels higher than 0.675%, rearrangements of the gel network result in larger whey expulsion and syneresis. This knowledge is expected to be useful to maximize cheese yield and optimize processing conditions during cheese and cheese analogs manufacturing.