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

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

Buenos Aires

Congreso; WCCE11 - 11th WORLD CONGRESS OF CHEMICAL ENGINEERING; 2023

The manufacture of high-quality confectionery coatings with reduced sugar content is a priority for food industries, in order to satisfy the increased consumer demand. Isomalt is a naturally sourced sugar replacer with anticariogenic and probiotic properties, that was not studied in aerated foods. The objective of this work was to analyse the oscillatory shear behaviour of aerated coating systems produced by sucrose (sugar) 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 inclusion of air was done by whisking 200 g of each formulation using a planetary mixer during 10 min at medium velocity. Density of unaerated and aerated samples were determined gravimetrically (three replicates) to calculate the volume fraction of air (). Optical microscopy was used to estimate the microstructure of samples. Oscillatory shear rheometry was performed by duplicated, applying a stress sweep (0.6 to 1000 Pa) at 1 Hz and 25°C. Curves of elastic (G) and viscous (G) modulus as function of stress amplitude () were obtained. Normalised strain-stress Lissajous curves was also analysed.As result, the  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. Micrographics confirmed the presence of air and sucrose crystals in different levels depending on sample. Curves of G and G have revealed two clear regions (see figure as example): a small amplitude oscillatory shear (SAOS) zone, where the behaviour is linear and the microstructure of sample is preserved, and a large amplitude oscillatory shear (LAOS) zone, where the disruption of the structure is expected. In the LAOS region, a stress overshoot was observed, producing an increase in the values of G and G, probably due to the formation of new clusters in samples. Normalised strain-stress Lissajous curves for linear (1.3 Pa of ) and non-linear (676 Pa of ) 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 the  and the viscoelastic behaviour. These finding are useful to control both the formulation and aeration of novel confectionery coatings elaborated with alternative ingredients, such as sweeteners.