Effect of Heat and High-Pressure Treatments on Microbiological Quality and Immunoglobulin G Stability of Caprine Colostrum

Caprine colostrums (6 batches) were subjected to heat (56°C for 60 min and 63°C for 30 min) and high-pressure (400 and 500 MPa for 10 min at 20°C) treatments at laboratory scale, and analyses of the main microbial groups and the extent of IgG denaturation (determined by immunodiffusion) were performed. Overall mean microbial values in raw colostrums were: total count, 5.55 log cfu/mL; Enterobacteriaceae, 2.64 log cfu/mL; lactococci, 5.41 log cfu/mL; lactobacilli, 2.34 log cfu/mL; and enterococci, 4.06 log cfu/mL. Neither Salmonella spp. nor Listeria monocytogenes were detected, whereas coagulase-positive staphylococci were found in various colostrum samples with an overall mean of 1.02 log cfu/mL. Heat and high-pressure treatments significantly reduced total count (1.47 log), lactococci (1.45 log), enterococci (2.47 log), and Enterobacteriaceae, whereas lactobacilli and coagulase-positive staphylococci counts were reduced to undetectable levels, but differences between technological treatments were not statistically significant. High-pressure treatments were as efficient in reducing the bacterial population as were heat pasteurization treatments: 95.50 and 96.93% for pressure treatments of 400 and 500 MPa, and 91.61 and 97.59% for heat treatments of 56°C for 60 min and 63°C for 30 min, respectively. All treatments assayed produced a reduction in colostrum IgG concentration (27.53, 23.58, 23.33, 22.09, and 17.06 mg/mL for raw, heat-treated at 56°C for 60 min or 63°C for 30 min, and pressure-treated at 400 and 500 MPa, respectively), but differences were only observed between raw colostrums and those pressure-treated at 500 MPa. This laboratory-scale study indicated that 20- to 30-mL volumes of goat colostrum could be heated and pressure-treated (400 MPa) to produce hygienic colostrum without affecting IgG concentration.