• Effects of Seasonal Variation in Milk Composition on the Quality of Pizza Cheese

      Guinee, Timothy P.; O'Brien, Bernadette; Kelly, Paul M; Connolly, J.F. (Teagasc, 1999-02-01)
      The main aims of this study were to investigate the effects of diet and lactation stage on the composition and cheesemaking quality of milk produced under controlled conditions. The main conclusions were as follows: These studies clearly demonstrated that the Recommended Moorepark Milk Production System in conjunction with an objectively standardised cheesemaking process provides a model for year round production of quality Mozzarella cheese. Databases have been established on the effects of diet quantity and quality, and stage of lactation on the composition, processability and cheesemaking characteristics of milk from both Spring- and Autumn-calving herds. Increasing the daily herbage allowance from 16 to 24 kgs DM/cow/day during mid-lactation, resulted in increases in the level of milk casein and cheese yield but had little influence on cheese functionality. Similarily improving diet quality in mid-lactation by reducing the stocking density from 4.3 to 3.8 cows/ha combined with concentrate supplementation (3 kgs/cow/day) had the same effect. Using milk from a Spring-calving herd, produced according to the Recommended Moorepark Milk Production System, in conjunction with an objectively-standardised Mozzarella cheesemaking process, no major problems were encountered during the lactation period 170 - 273 days from calving. Extending the lactation period of the Spring-calving herd from ~ 273 to 286 days resulted in higher cheese moisture (by ~ 2%), softer cheese, and lower chewiness in the melted cheese. A sharp decline in both total protein, casein and lactose in the milk was observed during this period. However the blending of this milk with milk of an Autumn-calving herd overcame these cheesemaking problems. The yield of low moisture Mozzarella cheese (using milks from Spring- or Autumn-calved herds) was positively correlated with milk casein level. The yield of cheese from the Spring-calved herd increased concomitantly with increasing casein level to day 273 of lactation and decreased thereafter as the casein concentration declined. In these studies it was found that easy-to-use tests such as lactose level in the milk and rennet coagulation properties as determined by Formagraph were useful indicators of the suitability of milk for cheesemaking. The Recommended Moorepark Milk Production System, as applied in the late lactation period, was characterised by a high plane of nutrition and a drying-off strategy which ensured a minimum daily milk yield per cow of 9 kg. It resulted in milk of good cheesemaking quality - lactose > 4.25%, and casein > 2.6% and satisfactory rennet coagulation properties - curd firming rate of > 0.15 min ¯¹ curd firmness at 60 min of > 45mm - at the end of lactation.
    • 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. (Teagasc, 1999-07-01)
      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.