Effects of pH and temperature on the water-holding capacity of casein curds and whey protein gels

Abstract

SummaryThe water-holding capacities of mineral acid casein (MAC) curd, rennet casein curd and whey protein concentrate (WPC) gel were determined as a function of pH and temperature by drainage of liquid on a stationary, horizontal screen. As precipitation pH was varied over the range 4·3–5·55, the water-holding capacity of MAC curd ranged from 2·4 to 5·2 g water/g dry casein with minimum water-holding capacity at precipitation pH 5·3. Samples of dried MAC curd over the same range of precipitation pH did not vary significantly in water-holding capacity, and all absorbed ∼2·0 g water/g dry casein. Both rennet casein curd and WPC (170 g total solids/kg) gels increased in water-holding capacity as the pH of the suspending liquid increased in the range 3·5–10, but the changes with pH were much smaller than for MAC curd. For both types of casein curd and for WPC gel, water-holding capacity decreased with increase in temperature in the range 5–90 °C. The results are interpreted largely in terms of changes in electrostatic interactions with pH and changes in hydrophobic interactions with temperature.

Microstructure and Some Functional Properties of Spray Dried Cheddar Whey Concentrated by Ultrafiltration or Combination of Ultrafiltration and Vacuum Evaporation.

“…This was because the protein contents of the UFSD and UFVESD were comparable (Ji, 2000) and protein structure was perhaps not altered significantly by the VE process. Teo et al (1996) reported a decrease in WHC of WPC gels with an increase in temperature in the range of 5-90˚C. Kneifel et al (1990) observed a steady increase in WHC of caseinates with an increase in temperature of preheating skim milk from 60 to 120˚C with a 10˚C increment.…”

Dynamics of isoelectric precipitation of casein using sulfuric acid

“…the same range as those found by Jablonka and Munro 1986 Ž . and Teo et al 1996a . At an aging time of 10 min, the solids content decreased linearly from 19.9% at an acidification time of 1.5 min to 17.6% at 16 min.…”

“…It was suggested that the calcium binding was a Ž . cause for the higher particle size Teo et al 1996a . The results on the influence of temperature that were found in this Ž .…”

Reversibility of shrinkage of mineral acid casein curd as a function of ionic strength, pH and temperature

“…The manufacturing processes for casein and caseinates have been reviewed recently by Mulvihill (1989). Efficient operation of the solid-liquid separation devices at the dewheying and dewatering stages and between each stage of the washing process requires some knowledge of the water-holding capacity of the casein curd as elaborated by Teo et al (1996). Ionic strength, pH and temperature are the main physicochemical variables known to affect curd water-holding capacity.…”

“…The physicochemical effects of washing on the curd water-holding capacity were not considered. Teo et al (1996) have shown that washing caused a dramatic reduction in the water-holding capacity of both mineral acid casein (MAC) and rennet casein (RC) curds. For MAC curd the water-holding capacity was calculated to be 8-18 g water/g dry casein after acidulation and 4-66 g water/g dry casein after the final wash. O'Meara & Munro (1982) reported that the shrinkage of MAC curd on entering the first wash was very rapid with the final curd volume reached within ~ 1 min.…”