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Genetic Variants of Milk Proteins - Relevance to Milk Composition and Cheese Production.
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1999-07-01
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Fitzgerald, R.J., et al., Genetic Variants of Milk Proteins - Relevance to Milk Composition and Cheese Production, End of Project Reports, Teagasc, 1999.
Abstract
Objectives: (i) to develop rapid screening procedures for the determination of milk
protein polymorphism (genetic variants)
(ii) to determine the frequency distribution of milk protein genetic variants in
a large population of Irish Holstein-Friesians and to determine if there was an
association between κ-casein variant and milk yield and composition in this group
of animals, and
(iii) to make Cheddar and low-moisture part-skim Mozzarella cheese from
different κ-casein genetic variant milks and to assess any effect on cheese yield,
composition and functional characteristics. Conclusions:Analysis of 6,007 individual Irish Holstein-Friesian milks showed that the
phenotype distribution of the κ-casein BB variant was very low at 1.98%
compared to 53.07% for κ-casein AA and 44.95% for κ-casein AB. While no statistically significant associations were observed between κ-casein
variant and milk yield and composition, κ-casein BB variant milks had superior
rennet coagulation properties to that of the AA or AB variants.
Generally, κ-casein variant had little effect on compositional attributes of cheese
apart from FDM (fat in dry matter) which was significantly higher in cheeses from
κ-casein BB milk than in those from κ-casein AA milk.
Generally, κ-casein variant had no significant effects on either primary or
secondary proteolysis, or on the sensory and/or textural characteristics of Cheddar
or Mozzarella cheese throughout ripening; or on the functional characteristics (e.g.
flow and stretch) of baked Mozzarella on storage for 90 days at 4°C.
However, κ-casein BB variant milk gave significantly higher actual, and moisture
adjusted yields of Cheddar and Mozzarella cheese than either κ-casein AB or AA
variant milks. For example, the moisture adjusted Cheddar yield from κ-casein
BB milk was 8.2% higher than from κ-casein AA milk. In the case of Mozzarella,
the moisture adjusted yield was 12% higher.
Based on the results, it is estimated that the actual yield of cheese in a plant
producing 20,000 tonnes per year from κ-casein AA milk would increase to
approximately 21,180 tonnes of Cheddar, or 21,780 tonnes of Mozzarella if made
from κ-casein BB milk. Where κ-casein AB milk is used instead of κ-casein BB
milk, the estimated yield of Mozzarella would increase to 21,580 tonnes.