Behaviour of minerals during the vacuum concentration of dairy ultrafiltration permeates

Whey concentration using evaporators results in deposit of matter on the hot surfaces of the evaporation tubes. The mass deposited during concentration depends mainly on the mineral composition of the whey, which varies considerably depending on the production process. We investigated the behaviour of ultrafiltration permeates (UFP) during concentration and the susceptibility of their mineral fraction to precipitation. UFP with differing mineral compositions were produced by acidification of milk with different acids to pH values between 4.6 and 6.3, followed by ultrafiltration. The results revealed either no precipitation or the precipitation of calcium salts (calcium phosphate, calcium citrate) in the concentrates. The behaviour of mineral fraction during concentration could be assessed by considering: (i) the nature and quantities of cations and anions in the concentrates, (ii) the anionic forms present at the pH of the concentrates and their association constants with calcium, and (iii) the solubility limit of calcium salts.