Effect of cysteine addition and heat treatment on the properties and microstructure of a calcium-induced whey protein cold-set gel

Abstract

A model gel of whey protein isolate (WPI) was prepared by cold gelation with calcium. This system was modified by the addition of free cysteine residues (Cys) at different steps of the process. The WPI cold-set gels obtained were then subjected to heat treatment at 90°C. First, the effect of Cys addition on the heat-induced aggregation of WPI was studied through Atomic Force Microscopy (AFM) and infrared spectroscopy (ATR-FTIR), while Cys' effect on cold gelation was observed by AFM, Confocal Laser Scanning Microscopy (CLSM) and oscillatory rheology (amplitude sweeps). The impact of heating on the microstructure and the viscoelastic properties of the WPI cold-set gels were finally investigated through several techniques, including DSC, ATR-FTIR, CLSM, cryo-SEM, and rheological measurements (temperature sweeps). When added during the first step of cold gelation, Cys modified heat-induced aggregation of WPI, resulting in the formation of a denser gel network with a fractal dimension (Df) of 2.8. However, the addition of Cys during the second step of cold gelation led to the formation of highly branched clusters of WPI and a looser gel network was observed (Df = 2.4). In this regard, the use and limitations of oscillatory rheology and the “Kraus model” to determine the Df of WPI cold-set gels was discussed. The viscoelastic properties and the microstructure of the WPI cold-set gels were irreversibly modified by heating. Gels were stiffer, more brittle, and coarser after heat treatment. New disulfide bonds and calcium bridges formed, as well as H-bonded β-sheets, all contributing to the formation of the final gel network structure.

Impact of steaming and roasting heat‐treatment on physico‐chemical and functional properties of walnut kernel

“…The increase of random coil and ɑ‐helix proportions in protein can reflect the changes of Δ H (Liu et al, 2016). As can be shown in Table 3, there are an increase in the Δ H values of roasted and steamed walnut kernel compared to that of untreated sample, which suggested that the heating treatment could increase the unfolding molecular structure of protein and change the stable structure of protein (Lavoisier et al, 2019). The value of Δ H was the highest in roasting and steaming for 20 min, which was 7.07 and 8.69 J g −1 , respectively.…”

Brühwürste und Surrogate

“…Ovalbumin ist mit 386 Aminosäuren hinreichend lang und unterstützt mit Cystein eine Netzwerkbildung innerhalb von wenigen Minuten. [13,14] Dabei konkurriert Ovalbumin mit sich selbst: zum einen dienen dessen hydrophoben Sequenzen zur Emulsion, zum anderen werden Ovalbumine bei Temperaturen oberhalb 70 °C intermolekular vernetzt. Hydrophobe Sequenzen werden zugunsten der Vernetzung von der Öl-Wasser-Grenzfläche gelöst.…”

In vitro digestion of two protein-rich dairy products in the ageing gastrointestinal tract

“…1), which is typically observed when the structure of protein aggregate gels is broken. 48 The irreversible deformation of samples (=critical strain) occurred at γ ≈ 2.5% for WBD, and at γ between 0.5 and 1% for the three commercial products. These results show that the properties of WBD enriched in proteins and formulated mainly with whey proteins (WP : CAS ratio = 80 : 20) were comparable to the rheological properties of a stirred yogurt.…”