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Genetic Variants of Milk Proteins - Relevance to Milk Composition and Cheese Production.
Fitzgerald, Richard J. Walsh, Daniel Guinee, Timothy P. Murphy, J.J. Mehra, Raj Harrington, D. Connolly, J.F.
Fitzgerald, Richard J.
Walsh, Daniel
Guinee, Timothy P.
Murphy, J.J.
Mehra, Raj
Harrington, D.
Connolly, J.F.
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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.