Characterisation of the viscoelastic properties of avocado puree for process design applications

Abstract

Avocado is increasingly utilised for the manufacture of products including purees, concentrates, powders and avocado oil. The design of such processes requires understanding of the rheology, particularly during the puree's transformation. This study characterised the viscoelastic properties at 25 °C of fresh avocado puree resulting from various processing operations including mixing, water dilution, and after sonication treatment. The storage ( G ′) and loss ( G ″) moduli of avocado puree demonstrated a solid-like behaviour irrespective of treatment or dilution, contrary to other food matrices. Avocado puree produced with manual-shearing showed greater G ′ and G ″ than when obtained with a food-processor. Extended shearing through the malaxation operation (mixing and kneading at 49 rpm and 45 °C); or water dilution to 72–94% moisture, diminished both moduli, with an exponential decrease observed in the latter. However, sonication for 5 min with high-power-ultrasound (18 kHz and 40 kHz) or megasonics (MS) (2 MHz) (80–90 kJ kg −1 ) increased G ′ and G ″. The net change in viscoelastic properties due to puree low frequency sonication correlated linearly with moisture content. The influence of processing interventions in avocado puree was demonstrated through rheological methods applicable for avocado process optimisation and product development.