Problems concerning ovine milk clotting aptitude

Abstract

A comparative study of the lactodynamographic parameters was carried out on ovine milk. Besides evaluating the repeatability and reproducibility of the analytical method, the influence of some variables such as the genetic type (three breeds), the kind of milk (whole or skimmed), and its concentration after reconstitution (12g or 20g /100 ml) was evaluated. The working plan involved 6 laboratories for the final statistic analyses, by the use of freeze-dried milk samples (adequately reconstituted on the basis of established methods) from Sardinia, Comisana, and Massese ewes. All the considered variability factors showed a highly significant effect (P<0.001) on the lactodynamographic parameters considered. In particular, Massese ewe milk showed the shortest curd speed (k20) and the best coagulum strength (a30 and a45), although clotting time (CT) was the highest one. The same trend was registered for skimmed milk and for the most concentrated one (20g). Repeatability values within laboratories were 96% and 97% for CT and k20, lowering for a30 e a45, (respectively 87% and 85%). Much lower coefficients were found for the among laboratories reproducibility, ranging from a maximum of 58% for CT to a minimum of 18% for k20. The wide variability observed indicates that lactodynamographic parameters are comparable only within the same lab. Further investigation is needed to compare different labs in order to obtain more homogeneous results.

Keywords

• Ovine milk
• Lactodynamographic analysis
• Repeatability
• Reproducibility