Small and large amplitude oscillatory shear behaviour of full-sugar and reduced-sugar aerated coating systems

MEZA, B. E.; DE PIANTE VICIN, D. A.; PERALTA, J. M.

Buenos Aires

Congreso; 11th World Congress of Chemical Engineering; 2023

Asociación Argentina de Ingenieros Químicos

The manufacture of high-quality and reduced-sugar confectionery coatings to satisfy the increased consumer demand is a priority for food industries. Isomalt is a naturally sourced sugar replacer with anticariogenic and probiotic properties, and its use in aerated foods was not studied. The objective of this work was to analyse the oscillatory shear behaviour of aerated coating systems formulated with sucrose and isomalt. Full-sugar systems were elaborated using commercial ingredients: powered sucrose (80% w/w), pasteurised egg white protein powder (1.6% w/w), and distilled water (18.4% w/w). Reduced-sugar samples were obtained by replacing 20% and 40% of sucrose by isomalt (20% SR and 40% SR). The aeration was done by whisking 200 g of each formulation with a planetary mixer for 10 min at medium velocity. Density of unaerated and aerated samples were determined gravimetrically (three replicates) to calculate the volume fraction of air (phi). Optical microscopy was used to estimate the microstructure of samples. Oscillatory shear rheometry was performed in duplicate, applying a stress sweep (0.8 to 1000 Pa) at 1 Hz and 25°C. Curves of elastic (G') and viscous (G'') modulus as function of stress amplitude (tau) were obtained. Normalised strain-stress Lissajous curves were also analysed. As result, phi values decreased as the sucrose replacement by isomalt increased, from 0.40±0.01 to 0.36±0.01 for full-sugar and 40% SR samples, respectively. The analysis of micrographs confirmed the presence of air and sucrose crystals in different levels depending on sample. Curves of G' and G'' have revealed two regions (see figure): a small amplitude oscillatory shear (SAOS) zone, where the behaviour is linear and the microstructure is preserved, and a large amplitude oscillatory shear (LAOS) zone, where the disruption of the structure is expected. A stress overshoot was observed in the LAOS region, producing an increase in the G' and G'' values, probably due to the formation of new clusters. Normalised strain-stress Lissajous curves for linear (1.3 Pa of tau) and non-linear (676 Pa of tau) behaviour showed a transition from viscoelastic to almost purely viscous behaviour that differs between full-sugar and reduced-sugar samples. As conclusion, the partial replacement of sucrose by isomalt in aerated systems modified their phi and the viscoelastic behaviour. These findings are useful to control the formulation and aeration of novel confectionery coatings elaborated with sweeteners.