Correlation between heat stability and alcohol test of milks at a milk collection center
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Abstract
The alcohol test is used by the milk industry as reception test for milk in the plant, to measure the heat stability of milk. The initial recommended ethanol concentration was 68% (v/v), but increased by the plants to 78% (v/v), with the risk of unjustified sample rejection.
The objective of this study was to determine the correlation between the parameters of alcohol test and the heat stability of milk towards and their relationships with pH, acidity, somatic cells and total bacteria counts.
Ninety six samples of cow raw milk from 11 small farms from the Milk collection center of Reumén, located in the Province of Valdivia, were analized. Eight samples were analyzed between September to December 1999. The quality analysis was carried out according to the national standards and heat stability was analyzed according to Davies and White modified method. The alcohol test was carried out at four ethanol concentrations (70, 75, 80 and 85% v/v) at Milk collection center of Reumén.
The average results for acidity and pH were within the range indicated for Chile. Somatic cells average were 299.000 (cél x ml) ± 69,950 and total bacteria counts log 4,58 (ufc/ml) ± 0,40; the average for heat stability was 63,38 (s) ± 3,96. The differences obtained among samplings were statistically significant (p< 0,05) for pH, heat stability and total bacteria counts.
The average of the results among farms were statistically significant (p< 0,05) for acidity, pH, somatics cells and total bacteria counts. There were significant correlations between pH and acidity (r = -0,4656) as well as between total bacteria count and heat stability (r= -0,2324), but not between the parameters of alcohol test and heat stability.
Based on the results, it is possible to conclude that there is no significant correlation between alcohol test and heat stability and a 75% (v/v) concentration of ethanol is recommended for the alcohol test at Milk collection center.