Heating-induced bacteriological and biochemical modifications in human donor milk after holder pasteurisation.

OBJECTIVES

The objectives of the present study were to enumerate and characterize the pathogenic potential of the Bacillus population that may survive holder pasteurisation of human milk and to evaluate the nutritional damage of this treatment using the furosine and lactulose indexes.

MATERIALS AND METHODS

Milk samples from 21 donors were heated at 62.5°C for 30 minutes. Bacterial counts, lactose, glucose, myoinositol, lactulose, and furosine were determined before and after the heat treatment. Some B cereus isolates that survived after pasteurisation were evaluated for toxigenic potential.

RESULTS

Nonpasteurised milk samples showed bacterial growth in most of the agar media tested. Bacterial survival after pasteurisation was observed in only 3 samples and, in these cases, the microorganisms isolated belonged to the species B cereus. Furosine could not be detected in any of the samples, whereas changes in lactose, glucose, and myoinositol concentrations after holder pasteurisation were not relevant. Lactulose was below the detection limit of the analytical method in nonpasteurised samples, whereas it was found at low levels in 62% of the samples after holder pasteurisation. The lactation period influenced myoinositol content because its concentration was significantly higher in transition milk than in mature or late lactation milk samples.

CONCLUSIONS

Holder pasteurisation led to the destruction of bacteria present initially in donor milk samples, except for some B cereus that did not display a high virulence potential and did not modify significantly the concentration of the compounds analyzed in the present study.