Microfiltration performance: physicochemical aspects of whey pretreatment

Abstract

Clarification of whey by microfiltration (MF) can be achieved after appropriate pretreatment of the feed. A control pretreatment consists of a physicochemical process comprising increased ionic calcium and pH accompanied by heat (50 °C, 15 min) to cause aggregation of complex lipid-calcium phosphate particles, which are then separated by MF. This pretreatment process was modified by increasing the temperature to 55 °C and by maintaining the pH constant during heat treatment. This modification resulted in larger calcium phosphate particles and a lower content of soluble calcium and phosphate ions. As a consequence, a longer period of MF operation, better whey clarification and lower calcium and phosphate content of the filtrate were achieved. This suggests that a loosely structured deposit was formed on the membrane surface which was less resistant to filtration than that resulting from the control pretreatment. During MF, it was necessary to avoid .zones of high shear in the retentate compartment that might cause physical alteration of the aggregates.

Temperature dependent membrane fouling during filtration of whey and whey proteins

“…Since the speed of particle cross-linking increases disproportionately with temperature, the fouling reaction at high temperatures is enhanced. For the filtration of whey and whey proteins, some authors suppose that protein crosslinking by the formation of calcium-bridges or calcium phosphate precipitation are involved in membrane fouling [12,[15][16][17][18][19]. Even though it was found that calcium had a minor effect on flux decline, calcium-based protein interactions might enhance membrane fouling at higher temperatures when calcium phosphate becomes increasingly insoluble.…”

“…Independently from processing temperature it is generally agreed that whey proteins in general and, in particular the major whey protein β-lactoglobulin (β-Lg), are the main foulants during whey filtration processes [9,[12][13][14]. In addition to whey proteins, some authors suppose that protein cross-linking by the formation of calcium-bridges or calcium phosphate precipitation are involved in membrane fouling [12,[15][16][17][18][19].…”

Whey crossflow microfiltration using an M14 Carbosep membrane: influence of initial hydraulic resistance

“…According to previous and recent studies (Gésan et al, 1993a(Gésan et al, , 1994) the increase of fouling versus time could be the outcome of an increasing deposit layer thickness on the membrane surface. This deposit, composed 275 mainly of calcium and phosphate aggregates could entrap protein and consequently affect their transfer to the permeate.…”

“…The major features were: fouling heteroqeneity connected to counter-pressure modes, static and dynamic as reported by Gésan et al (1993a); aggregates size related to pretreatment and po rosit y of the fouling deposit th us created (Gésan et al, 1994).…”

“…The influence of initial membrane hydraulic resistance, Rm on MF performance was con-firmed using other operating conditions: static counter pressure mode (without recirculation of permeate); different whey pretreatment (temperature of whey -55°C, and pH maintained at 7.5 during the pretreatment (Gésan et al, 1994)). …”