Effect of temperature of storage on the composition and microbiological quality of raw milk

Abstract

The aim of the study was to evaluate the quality of refrigerated raw milk from dairy farms located in Southwestern state of Goiás during the rainy and dry seasons. Fresh milk samples were collected from bulk tank and stored for 0, 24, 48 and 72 h for the evaluation of psychrotrophic microorganisms counts, titratable acidity, chemical composition, somatic cell count (SCC) and total bacterial count (TBC). In the rainy season, the average temperature of the refrigerated raw milk samples was 17.4, 6.0, 6.1 and 5.3°C and in the dry period, the average temperature was 9.2, 2.4, 3.8 and 1.4°C for 0, 24, 48 and 72 h of storage, respectively. The physicochemical characteristics of refrigerated milk were consistent with the maximum limits established by Brazilian legislation after storage for 72 h in expansion tanks; however, in the dry period, refrigerated milk should not remain stored for more than 24 h due to the high TBC values. The results of the microbiological analyses revealed failures in the cleaning of equipment and utensils used for milking, demonstrating need for greater hygiene in the collection and maintenance of refrigerated milk at the production source.

Farm management and economic factors associated with bulk tank total bacterial count in Holstein dairy herds in Iran

“…Farms that delivered milk to the company multiple times per day had the lowest TBC. Storing raw milk under refrigeration for a long time at the dairy farm and its delivery to the processor can create an environment suitable for the growth of microorganisms and increase the TBC of milk (Silva et al ., 2015). For example, a Brazilian study recommended a maximum storage time of up to 24 h (Silva et al ., 2015).…”

“…Farms that delivered milk to the company multiple times per day had the lowest TBC. Storing raw milk under refrigeration for a long time at the dairy farm and its delivery to the industrial factories can create a suitable environment for the growth of microorganisms and increase the TBC of milk (Silva et al, 2015). One of the Brazilian state requirements for producing raw milk with high quality is the duration of milk storage in refrigeration for 48 hours.…”

“…One of the Brazilian state requirements for producing raw milk with high quality is the duration of milk storage in refrigeration for 48 hours. For more remarkable performance, it is recommended to have a maximum storage time of up to 24 hours (Silva et al, 2015). Nonetheless, O'Connell et al ( 2017) study indicated that milk could be stored for up to 96 hours at temperatures between 2 and 6 C with a negligible effect on its composition or properties.…”