Heat Treatment of Bovine Colostrum. Ⅰ: Effects of Temperature on Viscosity and Immunoglobulin G Level

摘要

The objective of this study was to identify the critical temperature, at or below which heat-treatment of bovine colostrum would produce no significant changes in viscosity, IgG concentration, or Ig activity. Results of preliminary work, using a Rapid Visco Analyzer (RVA) to heat 50-mL aliquots from 6 unique batches of bovine colostrum at 59, 60, 61, 62, and 63℃, suggested that colostrum could be heated to 60℃ for up to 120 min without changing viscosity or IgG concentration. This finding was confirmed by heating 50-mL aliquots from 30 unique batches of colostrum in an RVA for 120 min at 60 and 63℃. Heating colostrum to 63℃ resulted in an estimated 34% decrease in IgG concentration and 33% increase in viscosity. However, there was no difference in IgG concentration between pre-heat-treated (73.4 ± 26.5 mg/mL) and post-heat-treated (74.5 ± 24.3 mg/mL) samples after heating colostrum to 60℃ in an RVA for 120 min. Similarly, viscosity was unaffected after heating colostrum to 60℃ in an RVA for 120 min. High quality colostrum ( ≥ 73.0 mg/mL) suffered greater losses of IgG and greater viscosity changes when heated to 63℃ than did moderate quality colostrum ( < 73.0 mg/mL). However, the effects of colostrum quality were minor if high quality colostrum was only heated to 60℃. The results of a bovine viral diarrhea serum neutralization assay suggested that antibody activity was unchanged after heating colostrum to either 60 or 63℃. However, these results were interpreted as being inconclusive due to a high proportion of missing results because of the congealing of many samples after heat treatment. The results of this study indicate that 50-mL volumes of bovine colostrum can be heat treated at 60℃ for up to 120 min in an RVA without affecting IgG concentration or viscosity.