Influence of formulation, process and storage conditions on the thermal and physical properties of hazelnut spreads

Hazelnut spreads are complex multiphase systems of different solid particles (sugar, cocoa powder, milk powder, hazelnuts, etc.) dispersed in a continuous fat phase. Their structure is mainly influenced by the fat crystals interactions. In this study, the effect of three variables: i) type of fat (palm oil (P), palm/sunflower oil (PS), sunflower oil/cocoa butter (SC)); ii) cooling temperature (22, 32°C); iii) storage times at 25°C (0, 2, 15, 30 days), on the thermal and structural properties of hazelnut spreads, was evaluated. A multilevel characterization was performed: fat melting, by differential scanning calorimetry; viscoelastic properties, by rheological tests; consistency, by texture analysis; colour, by CIE-Lab colorimeter. The statistical analysis showed how 'formulation' was the mainly discriminating variable. PS and P resulted respectively the more and the less rigid samples, according to both texture and rheological analysis, probably in relation to the different solid fat content or size of fat particles [1]. This hypothesis was supported by the calorimetric results, that showed higher enthalpies of fat melting for PS in comparison to SC and P, positively correlated with firmness, flow point and the colorimetric hue angle. The samples cooled at 22°C resulted more rigid than the ones cooled at 32°C. Probably the higher cooling rates cause the formation of smaller crystals and more particle interactions [2], as suggested by the lower Toff of fat melting observed for the 22°C cooled samples. During storage a general shift towards higher temperatures was observed for the fat melting peak, detected for P only after 30 days of storage, in relation to the increase of the rheological values K' and crossover point. These results can be useful for companies which intend to improve the process parameters that influence the quality of hazelnut spreads.