Turbidity and Protein Aggregation in Whey Protein Beverages

Abstract

During storage of heat-treated acidic (pH <or= 4.6) whey protein beverages, formation of protein aggregates can create undesirable turbidity and sedimentation. In this study, we found that a slow protein aggregation process controlled the rate of formation of sediment and turbidity. A heat-treated model beverage containing 12.5 g/L whey protein at a pH of 4 was stored for 6 wk at 3 different storage temperatures and analyzed for turbidity, soluble protein, and protein aggregates. One sample was stored without further treatment and the other sample was filtered to remove protein aggregates formed during heating. This was done to test the hypothesis that aggregates formed during heat treatment served as nuclei for deposition of soluble protein. Turbidity increased and soluble protein decreased as protein aggregates formed during storage. Increasing the storage temperature accelerated this process. The loss of soluble protein during storage was fit to first- and second-order kinetic equations, allowing the prediction of the effect of protein concentration, storage time, and storage temperature on the formation of protein aggregates.

Effect of Maillard-induced glycosylation on the nutritional quality, solubility, thermal stability and molecular configuration of whey proteinv

“…Therefore, when heated at >60 C and at a pH close to its isoelectric point (pH 4.5e5.5), whey protein solubility is minimized (Pelegrine & Gasparetto, 2005), due to the denaturation of the protein and the suppression of electrostatic repulsions. The delayed onset of denaturation at acidic pH, on the other hand, explains the enhancement in solubility and clarity at pH < 3.5 (LaClair & Etzel, 2009). However, at relatively high protein concentrations (>4%) solubility and solution clarity are reduced upon heating, even at low pH (Imetti, Cairolo, Gregori, & Bonomi, 1995).…”

Optimizing the use of power ultrasound to decrease turbidity in whey protein suspensions

“…A disadvantage to acidic beverages is that astringency is more pronounced necessitating the use of more sugar to offset the astringency. Beverages produced at neutral pH are generally opaque or turbid, even at just 2.5% protein, and less astringent, but require higher thermal processing temperatures than acidic beverages (Beecher et al, 2008;LaClair & Etzel, 2009). Therefore, increasing the clarity of whey protein solutions at neutral pH values is of industrial importance.…”

Effect of microbial transglutaminase treatment on thermal stability and pH-solubility of heat-shocked whey protein isolate

“…It has applications in several food products (De Wit, 1998;Fitzsimons, Mulvihill, & Morris, 2007), including meal replacement bars and protein beverages (Childs, Yates, & Drake, 2007;LaClair & Etzel, 2009. Heat treatments during processing inevitably cause partial denaturation of whey proteins, which often impairs their functionality in various applications (De Wit, 1990).…”