Occurrence of major whey proteins in the pH 4.6 insoluble protein fraction from UHT-treated milk.
A clear picture of the protein rearrangement in milk following UHT-treatment was drawn by a comparative analysis of the pH 4.6 soluble protein fraction (SPF) and the pH 4.6 insoluble protein fraction (IPF) recovered from raw and UHT-treated milk samples. The two protein fractions were analyzed by mono- or bidimensional gel electrophoresis under reducing and nonreducing conditions, and protein bands were identified by specific immunostaining. Results showed that bovine serum albumin, β-lactoglobulin, and, to a lesser extent, α-lactalbumin coprecipitated with caseins in UHT-treated milk samples at pH 4.6. These proteins were almost exclusively involved in high molecular weight aggregates held together by disulfide bonds. Partition of α-lactalbumin and bovine serum albumin in the protein fractions obtained upon acidification of milk at pH 4.6 was evaluated by competitive immunoassays. The ELISA-based results suggested the possibility of using pH 4.6 insoluble α-lactalbumin and bovine serum albumin, in addition to pH 4.6 insoluble β-lactoglobulin, as indicators of the intensity of the heat treatment applied to milk.
Consiglio Nazionale delle Ricerche (CNR), Istituto di Scienze dell'Alimentazione, Avellino, Italy. rosa.pizzano@isa.cnr.it
Rosa
R
Pizzano
Carla
C
Manzo
Maria Adalgisa
MA
Nicolai
Francesco
F
Addeo
D000818:Animals; D002364:Caseins / Q000032:analysis; D005511:Food Handling / Q000379:methods*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007768:Lactalbumin / Q000032:analysis; D007782:Lactoglobulins / Q000032:analysis; D008892:Milk / Q000737:chemistry*; D008894:Milk Proteins / Q000032:analysis* / Q000737:chemistry; D012710:Serum Albumin, Bovine / Q000032:analysis; D012995:Solubility
D002364:Caseins; D007782:Lactoglobulins; D008894:Milk Proteins; D012710:Serum Albumin, Bovine; D007768:Lactalbumin