Flavour release study as a way to explain xanthan–galactomannan interactions

In spite of numerous studies and abundant literature, xanthan(X)/galactomannan(GM) interactions still remain controversial while such mixtures have been intensively employed for a long time. The present work aims to bring new highlights on the nature of the interactions involved between both polysaccharides through an original approach: the behaviour of small volatile solutes in water-based X/GM solutions and mixtures. To this aim, a study of limonene release from X/guar (X/G) and X/carob (X/C) water-based mixed solutions has been investigated in the dilute and semi-dilute polymer concentration regimes. The aroma compound release from both matrices was compared together with the rheological properties of the solutions. When considering the limonene release as a function of the concentration regime, a dramatic decrease of the limonene release was observed for the X/C mixtures in the neighbourhood and above the critical overlap concentration C*. This result combined with kinetic experiments allowed to state the occurrence of specific interactions between limonene and polymeric junction zones formed in the X/C matrices. The apolar nature of the aroma compounds used allows to consider the nature by itself of the interactions responsible for volatile retention to be hydrophobic. A different mechanism for synergistic interactions between X and G was observed. The synergy appears quite lower than X/C mixtures and can be explained by phase separation occurring in the X/G mixture, favoured by ordered conformation of X.