Compositional and functional analysis of freeze-dried bovine skim colostrum powders

In the early few days, the composition of colostrum changes significantly, which strongly impacts the functional characteristics of skimmed colostrum powders. This study evaluated the effect of compositional changes of colostrum and its functional characteristics in the first 5 days of post-partum milking. The protein content of samples from day-1 to day-5 reduced from 13.5 to 3.5% (w/v). The lactose content increased while fat, ash, and solid not fat content decreased significantly (p < 0.05) during this period. The foaming capacity changed slightly, while the emulsifying capacity significantly decreased from day-1 to day-5 (50.8 +/- 1.35% to 32.6 +/- 1.8). The X-Ray diffraction (XRD) showed that the first 2 days' samples were amorphous, and the later samples showed slight peaks due to an increase in lactose content. Differential scanning colorimetry (DSC) found that the thermal stability increased (109 degrees C on day-1 to day-5 (109-132.4 degrees C) with the increasing lactose and casein content. Since freeze-drying is a non-thermal process, no changes in secondary structures (alpha-helix similar to 1655, random coil similar to 1646, and beta-sheets similar to 1632 cm(-1)) were observed in Fourier transforms infrared spectroscopy (FTIR). The FTIR indicates that the bioactive proteins were intact, which can be used to incorporate health-promoting effects. The in vitro digestibility of the day-1 sample showed a higher amount of recovered IgG (55.28 +/- 1.11%), IgM (18.28 +/- 0.93%), and IgA (11.42 +/- 0.58%) as compared to the number of recovered immunoglobulins in later days samples. The recovered IgG for day-5 was 27.02 +/- 0.82%, while the IgM and IgA could not be detected after the first 2 days. These colostrum powders showed good functional properties and can be incorporated into functional foods, nutraceuticals, and infant formulas to obtain the immune-boosting benefits of their bioactive proteins.