Microbiota mesophilic aerobic contaminant UHT milk

Abstract

In 2011 the national production of ultra-high temperature milk (UHT) was 5.81 billion liters, corresponding to 78% of fluid milk consumed in Brazil. The present work aimed to study UHT milk contamination by mesophilic aerobes (MA), verifying the accordance with microbiological standards, classifying the groups found according to its morpho-tinctorial characteristics and discussing the methodology determined by Normative Instruction (NI) 62 from the Brazilian Ministry of Agriculture, Animal Husbandry and Supply. From 60 studied samples, 23 (38.3%) presented results above the 100 CFU/mL standard established by NI 370 for (MA). When B. sporothermodurans was considered, maximum counts raised 71.2% in whole milk samples, and 31.0% in skimmed milk samples. Regarding the higher dilutions inoculated that have shown growth, it was possible to isolate 462 colonies of (MA) that, in Gram coloration corresponded to 64.3% Gram positive bacteria and 9.5% Gram negative. Molds and yeasts added up to 26.2%. Among Gram positive, there was a prevalence of cocci, B. sporothermodurans, and other Gram positive bacilli. Among Gram negative, the coccobacilli and bacilli prevailed. Considering that the samples represent UHT milk from important industries of southern Brazil, the results demonstrate that 11 out of the 15 studied brands showed high counts of (MA) when compared to the established standards. Furthermore, among the groups of microorganisms found in the samples, especially heat sensitive Gram negative bacteria, indicates possible failures in milk processing and/or post-processing contamination.