Rheological characterisation of thickened fluids under different temperature, pH and fat contents

Abstract

Purpose – The purpose of this paper was to examine the rheological characterisation of thickened water under different temperature and pH conditions and thickened milk with different fat contents. Design/methodology/approach – Beverages thickened with powdered thickeners are used in the medical management of individuals who suffer swallowing difficulties (dysphagia). Each individual requires a specific level of thickness to best meet the needs of their dysphagia. Although the level of thickness is defined, obtaining the correct consistency of thickened fluids is difficult. This is due to fluctuations associated with temperature and type of fluids to be thickened. Rheological characterisation of commercially available xanthan gum-based thickener was performed under different conditions of temperature, pH and fat contents. Findings – The viscosity and the yield stress of thickened water was found to be unaffected by pH. Similarly, temperature did not affect the viscosity at a high thickener concentration, although it did at lower concentration levels. Conversely, viscosity and yield stress increased as fat levels increased in thickened milk. Furthermore, thickened water took less than 2 minutes to reach equilibrium viscosity, while thickened milk required approximately 15 minutes to reach equilibrium viscosity. Practical implications – These findings have implications for the standing time required for different beverages before they are thickened to a consistency that has been deemed safe for the patient’s physiological needs. Additionally, it highlights that different liquid base substances required different amounts of thickener to achieve the same level of thickness. Originality/value – Findings from this study confirms and explores the variability of thickened fluids under different conditions of temperature, pH and fat content for the medical management of dysphagia.

Development of International Terminology and Definitions for Texture-Modified Foods and Thickened Fluids Used in Dysphagia Management: The IDDSI Framework

“…Viscosity is only one of a number of relevant parameters affecting liquid flow; others include density, yield stress, sample temperature, elasticity, and propulsion pressure [65–69]. …”

Understanding the Viscosity of Liquids used in Infant Dysphagia Management

“…The variations observed suggest some instability in the product for reasons that are unknown. However, recent studies have shown that the viscosity of milk products varies based on protein and fat content [16, 17]. Given fact that the Enfamil AR™ specialty formulas involve elements designed to reduce acid reflux and/or provide caloric fortification, it is tempting to speculate that protein or fat content may be contributing to increased viscosity.…”

Rheological characterisation of thickened milk components (protein, lactose and minerals)

“…This is due to the heavy dependence of the viscosity of thickened fluids on a number of factors. These include: differences in thickening agent (Sopade et al, 2007(Sopade et al, , 2008aGarcia et al, 2005), solids content of the liquid (Sopade et al, 2008a), and differences in dispersing medium (Sopade et al, 2007;Garcia et al, 2005;Nicholson et al, 2008) Previous work has focused on investigating the rheological properties of thickened milk and other dispersing media (Hadde et al, 2015;Sopade et al, 2008a). Thickened milk is a fluid that is commonly served to patients, as it offers fluids for hydration in addition to much needed protein and calcium (Claes et al, 2012;Barr et al, 2000).…”

“…The role of fat in the thickened milk has previously been studied and reported. It was reported that fat increases the equilibrium viscosity of thickened milk (Hadde et al, 2015). The objective of the current study was to:…”