Abstract
Camel, cow and buffalo skim milk samples were heated at 65, 75, 85 and 100°C for 10, 20 and 30 min. Presence and identity of whey proteins (WPs) were monitored using SDS-PAGE technique. Changes in activities of antimicrobial factors were measured. Heat-induced changes of WPs increased with increasing temperature and time of heating; they were more pronounced in buffalo and cow milk than in camel milk. Camel WPs were markedly more heat resistant than their counterparts in cow and buffalo milk. Among the WPs, the order of heat resistance found was: α-lactalbumin > β-lactoglobulin > serum albumin. Camel milk contained significantly (
P⩽0.01) higher concentrations of lysozyme (LZ), lactoferrin (LF) and immunoglobulin G (IgG) than cow and buffalo milk. Heating milk at 65°C/30 min had no significant effect on LZs and LFs, however, loss of activity of IgGs was significantly (
P⩽0.01) affected in the three kinds of milk. The whole activity of IgG in cow and buffalo milk was lost at 75°C/30 min versus 68.7% in loss activity of camel IgG. The entire activity of LFs was lost at 85°C/30 min in all kinds of milk, however, at this level of temperature, the activity losses of LZs were 56, 74 and 81.7% for camel, cow and buffalo milk, respectively. Camel milk antimicrobial factors were significantly (
P⩽0.01) more heat resistant than cow and buffalo milk proteins. Among the antimicrobial factors, the order of heat resistance found was LZ > LF > IgG.