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Seasonal variations in the composition and thermal properties of New Zealand milk fat: II. Thermal properties of milk fat and their relation to composition

Published online by Cambridge University Press:  01 June 2009

Gillian E. Norris ,
I. K. Gray  and
R. M. Dolby
Gillian E. Norris
Affiliation:
New Zealand Dairy Research Institute, Palmerston North, New Zealand
I. K. Gray
Affiliation:
New Zealand Dairy Research Institute, Palmerston North, New Zealand
R. M. Dolby
Affiliation:
New Zealand Dairy Research Institute, Palmerston North, New Zealand
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Summary

Melting curves were determined by differential scanning calorimetry on 17 samples of milk fat obtained at approximately fortnightly intervals through one dairying season. Liquid-fat content at a number of temperatures was calculated from the melting curves.

Correlation between percentage liquid fat at 12 and at 22 °C and weight percentage of short-chain fatty acids (C4–C8) was low (r = 0·45 and 0·58 respectively) as was that with cis-unsaturated acids (r = 0·39 and 0·29). Correlation with the sum of short-chain and cis-unsaturated acids was higher (r = 0·71 and 0·68). With a multiple regression model including short-chain and cis-unsaturated acids the values of the multiple correlation coefficient (R) were 0·75 and 0·78.

The softening point showed a high correlation (r = 0·79) with weight percentage of long-chain saturated acids and also with the temperature at which 94 % of the fat was liquid (r = 0·75).

Possible explanations of these findings are discussed.

Type
Research Article
Information
Journal of Dairy Research , Volume 40 , Issue 3 , October 1973 , pp. 311 - 321
Copyright
Copyright © Proprietors of Journal of Dairy Research 1973

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References

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