Effects of high pressure on some constituents and properties of buffalo milk

Abstract

In this study, effects of high pressure (HP) on some constituents and properties of buffalo milk were examined. HP treatment at 100–600 MPa for 30 min affected casein micelle size only slightly, whereas treatment at 800 MPa increased it by ~35%. Levels of non-micellar αs1- and β-caseins were increased by treatment [ges ]250 MPa, and were highest after treatment at 400–800 MPa. The level of non-micellar calcium increased with increasing pressure up to 600 MPa. The L*-value of the milk decreased gradually with increasing pressure, from ~82 for untreated milk to ~65 for milk treated at 800 MPa. Milk pH was increased by ~0·07 units after treatment at 100–800 MPa, with no significant difference between treatment pressures. Denaturation of α-lactalbumin occurred at pressures [ges ]400 MPa, and reached >90% after treatment at 800 MPa, whereas β-lactoglobulin (β-lg) was denatured >100 MPa, reaching ~100% after treatment at 400 MPa; after treatment [ges ]400 MPa, all β-lg was associated with the casein micelles. The rennet coagulation time of buffalo milk increased with increasing pressure, whereas the strength of the coagulum formed decreased after treatment at 250–800 MPa. Overall, HP treatment affected many constituents and properties of buffalo milk; some of these effects have also been observed in the milk from other species, but the extent of the effects, and the pressure at which they occurred, differed considerably.

Inhibition of the proteolytic activity of indigenous plasmin or exogenous chymosin and pepsin in bovine milk by blood serum

“…The coagulation time (CT) of milk by chymosin (Maxiren 180; DSM Food Specialties, Delft, The Netherlands) and the rheology of the chymosin-induced gel were determined as described by Huppertz et al (2005). The CT of milk by pepsin was determined as for chymosin, except that 75 mL of a 1:10 aqueous dilution of a porcine pepsin solution (strength: 50 CHU; Chr.…”

Influence of added calcium chloride on the heat stability of unconcentrated and concentrated bovine milk

“…The concentration of ionic calcium in milk was determined using a calcium ion‐selective electrode (Radiometer, Copenhagen, Denmark) and calculated from a standard curve of 0–10 mmol/L CaCl 2 in 0.1 m KCl. The level of calcium in milk and milk serum was determined by atomic absorption spectroscopy, as described by Huppertz et al . (2005).…”

Baroprotection of vegetative bacteria by milk constituents: A study of Listeria innocua

“…The level of calcium in milk or its ultracentrifugal supernatant (100,000 Â g for 60 min at 20 1C) was determined as outlined by Huppertz et al (2005). The level of inorganic phosphate in milk or its ultracentrifugal supernatant was determined as outlined by IDF (1990).…”