Shear rheology and filament stretching behaviour of xanthan gum and carboxymethyl cellulose solution in presence of saliva

Hyejung Choi,John R Mitchell,Sanyasi R Gaddipati,Sandra E Hill,Bettina Wolf

doi:10.1016/j.foodhyd.2014.01.029

Abstract

The objective of the work reported in this paper is to determine if saliva addition has an effect on the rheology of xanthan gum solutions. The reasons for the interest was that it has been previously reported that flavour release from high viscosity xanthan thickened foods is not reduced in the same way as foods thickened by other hydrocolloids at comparable viscosities. It was previously postulated that this could be due to an interaction between saliva and xanthan that could change the microstructure and rheology of xanthan solutions. In this work the effect of saliva on the rheology of CMC and xanthan solutions was compared. Solutions of molecularly dissolved xanthan gum and CMC mixed with water or human whole saliva at a ratio of 5:1 showed little impact of the presence of saliva on steady shear or dynamic viscosity for the two hydrocolloids. In filament thinning experiments saliva addition significantly increased filament break-up time for xanthan gum while it had little effect on the break-up time of the CMC filament. Also, filament thinning appeared a lot less even and was not as reproducible in the case of xanthan gum. Addition of CMC and hydroxypropyl methylcellulose (HPMC) to xanthan gum solutions showed a similar increase in break-up time to saliva, but to see this effect the viscosity of the added CMC or HPMC solution had to be very much higher than the viscosity of saliva. The results are discussed in the context of the structure of xanthan gum and the reported extensional rheology of saliva.

Highlights

For many years there has been substantial interest in the taste and flavour perception from viscous solutions
Mixing efficiency has been linked with the good taste and flavour release from starches, which retain their granular form when swollen, compared to a molecular solution of hydroxypropyl methylcellulose (HPMC) that was of the same shear viscosity at 50 sÀ1 (Ferry et al, 2006)
In contrast to the shear rheological properties, saliva addition does have an effect on the filament thinning behaviour

Summary

Introduction

For many years there has been substantial interest in the taste and flavour perception from viscous solutions. Mixing efficiency has been linked with the good taste and flavour release from starches, which retain their granular form when swollen, compared to a molecular solution of hydroxypropyl methylcellulose (HPMC) that was of the same shear viscosity at 50 sÀ1 (Ferry et al, 2006). A recent study on model soups thickened with swollen particles of physically modified xanthan gum and molecularly dissolved xanthan gum revealed that superior mixing behaviour and shorter filament break-up times did not coincide with enhanced taste and flavour release (Abson et al, 2014). The sensory panel was not able to distinguish taste and flavour perception between the tomato flavour intensity in xanthan and modified starch thickened tomato soup. Morris (1993) found that xanthan gum gives better taste perception at high viscosity than solutions thickened with other molecularly dissolved polysaccharides. The cited observations could suggest that predicting the sensory properties of hydrocolloids from measurements in water could be misleading and that the appropriate fluid to predict sensory behaviour based on flow properties would be saliva

Methods

Results

Conclusion