Whey protein aggregation under shear conditions – effects of pH‐value and removal of calcium

Abstract

The effects of pH‐value and a reduction in calcium content on the kinetics of whey protein denaturation and the aggregation behaviour, under shear in a scraped surface heat exchanger, were examined. The denaturation rate of β‐lactoglobulin at 80 °C is considerably retarded as the pH‐value decreases from pH 6.7 to 4.5. Aggregates which are produced under shear between pH 4 and 5.5 reveal a small particle size (<5 μm) irrespective of the lactose content and the heating temperature. This is attributed to the low reactivity of the thiol groups and the small net charge of the proteins in this pH‐range. At a reduced calcium concentration the heat‐ and shear‐treatment resulted in a gritty structure with large rubber‐like particles. These are not to be taken as primary whey protein aggregates but as fragments of a fine‐stranded gel.

Effect of calcium chloride and moderate shear on β-lactoglobulin aggregation in processing-like conditions

“…Comparison with literature values is difficult because different average diameters are reported (Table 1). For the studies with the same principle of measurement (Spiegel and Huss, 2002;Dissanayake and Vasiljevic, 2009), the average diameters reported (respectively D[0.5] volume $20 lm and average particle size $10 lm) are comparable to the size of the aggregates obtained with the higher concentration of CaCl 2 in our study.…”

Formation of heat-induced protein aggregates in milk as a means to recover the whey protein fraction in cheese manufacture, and potential of heat-treating milk at alkaline pH values in order to keep its rennet coagulation properties. A review

“…At constant temperature, decreasing lactose concentration reduces the protective effect of the sugar on denaturation of the whey proteins [21,124], while a combination of increased heating regimen and lactose concentration produces large aggregates with a sandy texture [70,147]. Adjusting the pH of the whey, generally in the range 3.5 to 7, prior to heat-treatment, is also a common method to control the size and hydration of the aggregates, although the reported optimum pH values differ significantly [40,84,148]. Other chemical means used to control the size of the aggregates are the variation in concentration of calcium or sodium salts [23,148], or the use of transglutaminase enzyme [145].…”

“…Adjusting the pH of the whey, generally in the range 3.5 to 7, prior to heat-treatment, is also a common method to control the size and hydration of the aggregates, although the reported optimum pH values differ significantly [40,84,148]. Other chemical means used to control the size of the aggregates are the variation in concentration of calcium or sodium salts [23,148], or the use of transglutaminase enzyme [145].…”

Effect of microparticulated whey protein with varying content of denatured protein on the rheological and sensory characteristics of low-fat yoghurt

“…Alternative processes may be utilized instead, such as extrusion cooking at acid pH (Queguiner, Dumay, Saloucavalier, & Cheftel, 1992) or dynamic high pressure shearing, i.e., microfluidization (Dissanayake & Vasiljevic, 2009;Paquin, Lebeuf, Richard, & Kalab, 1993). The result is whey protein aggregates with particle sizes that usually range between 0.1 and 10 mm (Spiegel & Huss, 2002) and that have previously shown their ability to provide sensory sensations associated with the presence of milk fat, i.e., creaminess, when incorporated into low-fat stirred yoghurt (Janhoj, Petersen, Frost, & Ipsen, 2006). Regarding the rheological characteristics of yoghurts when MWP is included in the formulation, improvements of the texture in reduced fat set-style yoghurts have been reported (Barrantes et al, 1994;Sandoval-Castilla, LobatoCalleros, Aguirre-Mandujano, & Vernon-Carter, 2004).…”