Short communication: Heat treatment and souring do not affect milk estrone and 17β-estradiol concentrations.

The aim of our study was to establish whether heat treatment and souring of milk affect its estrone (E1) and 17β-estradiol (E2) concentrations. Milk samples were collected from 10 Holstein cows in late pregnancy. Concentrations of E1 and E2 were measured in milk samples that were previously heated to 70 and 95°C for 5 min. Additionally, E1 and E2 concentrations were determined in the same milk samples after 2 d of spontaneous souring at room temperature, and these samples were compared with E1 and E2 levels in raw, unprocessed milk. Concentrations of both hormones were determined by commercial ELISA kits. Concentrations of E1 in unprocessed and processed milk (milk heated to 70 and 95°C and soured milk) were (mean ± SE) 47.25 ± 4.16, 44.84 ± 3.47, 41.00 ± 4.55, and 44.92 ± 3.91 pg/mL, respectively. Concentrations of E2 in the same milk samples were 36.11 ± 10.01, 32.46 ± 9.88, 31.78 ± 9.56, and 31.43 ± 8.00 pg/mL, respectively. Concentrations of E1 and E2 in heat-treated milk did not differ significantly from those in unprocessed milk. Similarly, E1 and E2 concentrations in soured milk did not differ significantly from those in unprocessed milk samples. These results indicate that E1 and E2 are stable in milk and that milk processing (heating and souring) does not influence their degradation. Therefore, E1 and E2 concentrations are expected to be similar between commercial full-fat milk and the raw milk from which it was produced.