The Effect of Outside Air Temperature on Transportation Temperatures and Processing Quality of Cow’s Milk

The objective of this study was to assess the effect of outside air temperature on the transportation temperature and processing quality of cow’s milk. The data used in the analyses (208 bulk samples) were collected on four farms over a period of 52 consecutive weeks. The samples were grouped into four outside air temperature‑based groups, namely: below 1.0 °C; from 1.1 to 8.0 °C; from 8.1 to 15.0 °C; above 15.1 °C. Mean values of the observed characteristics were as follows: average outside air temperature 7.40 °C, milk temperature on dairy farms 5.19 °C (at collection) and milk temperature on arrival at the dairy factory 5.60 °C. The average duration of transport was 211 minutes, milk volume in the tanker 12,885 l, fat content 4.13 %, protein content 3.40 %, lactose content 4.89 %, casein content 2.97 %, titratable acidity 6.31 SH, active acidity 6.75 (pH), rennet coagulation time (RCT) 201 sec., curd class 1.11 (on five‑point scale) and 1.49 (on ten‑point scale). Increasing outside air temperature was closely correlated (p < 0.01) with an increase in milk temperature at the dairy factory (at delivery). A significant (p < 0.01) increased difference between the temperatures on the farm (at collection) and at delivery in the dairy factory was also recorded. The titratable acidity decreased and so did the curd class on the ten‑point scale. Milk temperature on the farm (at point of entering transportation tank) also increased significantly (p < 0.01) with outside air temperature. Other differences were not significant (p > 0.05). Findings of this study suggest that outside air temperature influences the properties and processing quality of the transported milk, even though the temperature differences of the milk itself ranged within the acceptable limits. It therefore stands to reason that, when the temperature of milk on load is close to the recommended temperature limits it can exceed this limit during transportation to the dairy factory and cause significant damage to the processing quality of the transported milk.