Serving Temperature Viscosity Measurements of Nectar- and Honey-Thick Liquids

Abstract

This study reports the viscosity (thickness) of nectar-and honey-thick liquids measured at a typical serving temperature. Centipoise (cP) measurements were compared for three products (two starch and one gum-based thickener) mixed with five beverages that set for three time intervals (manufacturer recommended time to thicken, 10 and 30 minutes). The serving temperature of the cold beverages was 4º C (water, apple juice, orange juice, and milk), and the hot beverage (coffee) was measured at 70º C. Statistical analysis showed that all factors interacted with one another, meaning that the viscosity of a nectar-or honey-like liquid varies greatly depending on the type of thickening agent and beverage combination in relation to the amount of time its thickens. Simply Thick, the gum-based thickener, typically produced samples that were the least viscous but they maintained a more consistent level of thickness over time.Serving temperature results are contrasted with viscosity measurements collected at room temperature, showing variable thickening patterns especially related to the type of thickening agent.Key Words: viscosity, thickened liquids, temperature 2 Complex issues surround the use of thickened liquids in dysphagia management including aspects of their preparation and service delivery. Current practice patterns suggest that many facilities make use of thickened liquids that require some type of preparation such as a powder or gel-product mixed with a beverage to produce a target level of thickness.1 Achieving an appropriate level of consistency is complicated by a number of factors including insufficient production information on labels about thickening properties, vague guidelines about their preparation, as well as staff compliance in their service delivery. [2][3][4] Additionally, thickening products alter flavor and texture characteristics of the base beverage and produce different thickening patterns over time. [5][6][7][8] Variability across products and within products is of added concern since clinical judgments of thickness are not reliable. 9Temperature also affects thickness of liquids. Bourne 10 noted that the "viscosity of fluids is highly temperature dependent" (p. 235). The effect often is described by the Arrhenius relationship which indicates that the natural logarithm of the viscosity of most liquids shows a direct inverse relationship to temperature. 11 This inverse relationship (thickness decrease with temperature increase) has been documented with both liquid and semi-solid consistencies. 12-14Additionally, some products (such as water) have a preferred temperature that impacts its consumption. 15 Temperature manipulation often is a consideration related to aspects of swallowing. For example, a cold bolus is applied to enhance the immediacy of a pharyngeal swallow response and recognition of the bolus in the mouth for some patients with dysphagia. 16,17 Other patients demonstrate improved esophageal function in response to hot water swallows. 18The viscosity measurement of a thick...

Understanding the Rheological Parameters of Thickened Fluids for Dysphagia Sufferers

“…It is well-known that the viscosity of fluids is highly temperature dependent (Garcia et al, 2008). However, study of the viscosity of thickened fluids under different temperature conditions are limited.…”

“…Subsequent to the studies noted above, Garcia et al (2008) analysed the effect of temperature on viscosity of thickened fluids by measuring the viscosity of the fluid at two different temperatures, room temperature and serving temperature, at nectar-thick and honey-thick level. It was concluded that the viscosity of the thickened fluid increases as temperature decreases for starch based thickener.…”

“…It was stated that temperature variations of ± 1°C did not appreciably affect the measured viscosity of the samples because the resulting measurement were within the instrument's accuracy range (± 1°C) (Garcia et al, 2008).…”

“…Rheological variations between different thickened fluids mean that dysphagic patients could receive inconsistent levels of thickened beverages. There are many factors that affect the ability to reliably produce thickened liquids of a consistent level of thickness (Rosenvinge and Starke, 2005, Garcia et al, 2005, Garcia et al, 2008. To date, it has been established that these factors include solid contents , Sopade et al, 2008a, Sopade et al, 2008b, pH of the dispersing medium (Sopade et al, 2008b, Nicholson et al, 2008, Garcia et al, 2005 and serving temperature (Garcia et al, 2008).…”

“…This is because there are many factors that affect the ability to reliably produce thickened liquids with a consistent level of thickness. These factors are: differences in thickening agent , Sopade et al, 2008b, Garcia et al, 2005 solids content of the liquid (Sopade et al, 2008a), serving temperature (Garcia et al, 2008), and differences in dispersing media , Garcia et al, 2005, Nicholson et al, 2008.…”