Xanthan v. Starch
Individuals who either suffer from dysphagia or care for someone with dysphagia know firsthand the frightening and life-threatening symptoms and complications that can occur. Perhaps the most dangerous of these symptoms is aspiration pneumonia.
Aspiration is the action or process of drawing breath and is typically associated with dysphagia when liquid or food enters the airways. This elevates the patient’s risk for developing aspiration pneumonia, a potentially fatal illness that can often be difficult to identify and treat. Aspiration pneumonia is an inflammation of the lungs or bronchial tubes caused by inhalation of foreign material, such as food, saliva, liquids or vomit. When it deposits in the lungs, the immune system produces localized inflammation to isolate the infected area from the rest of the lung.
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Avoiding aspiration is a primary concern in the care of dysphagia patients. Fortunately, there are ways to help with prevention. Thickening beverages with starch or xanthan serves to reduce the risk of aspiration, but there are several properties differentiating the two thickeners.
Modified cornstarch used for dysphagia nutrition contains high levels of amylopectin, an insoluble component that gels, but does not solidify in liquids. It is translucent and builds high viscosity across a wide range of temperatures. When added to a beverage or food, the starch crystal swells, absorbing water and building viscosity. However, it can take hours for the starch to become fully hydrated.
Xanthan gum is a polysaccharide; its structure contains a cellulose backbone with branches of the sugars galactose and mannose. Like starch, xanthan also builds viscosity over a wide variety of temperatures. Recently, producers have started clarifying xanthan to make it more transparent and aid in its functionality for dysphagia patients. Compared to starch, xanthan becomes fully hydrated faster, requires less product to build higher viscosity and is more stable over time.
Compared to starch, it takes much less xanthan to achieve a desired consistency when thickening a beverage, and patients are less likely to aspirate xanthan-thickened liquids when compared to starch-thickened liquids (Leonard n.d.). If the patient does aspirate a starch-thickened item, the cilia (small hair-like structures in the trachea that act to clear the lungs of foreign material) work hard to remove the aspirated starch. Xanthan-thickened food or drinks contain less thickening agent, therefore less thickener enters the respiratory tract if aspiration does occur. While the cilia still have to work hard to remove the aspirated xanthan, less energy is expended to clear it versus the larger volume of starch (Dysphagia 2014). When xanthan liquids are aspirated, they are less likely to cause pulmonary injury than aspirated starch-thickened liquids (Domer 2014).
Key Properties of Xanthan and Starch
The ability to maintain a consistent viscosity over time is an important feature of a thickening product. In an institutional setting, beverages are often made up well before serving.
Starch continues to thicken over time, and a beverage that was mixed at a nectar consistency can develop a honey consistency by the time it is served. Xanthan maintains a more stable viscosity than starch over time, providing caregivers more flexibility in preparing and serving foods and beverages, as well as giving patients more time to safely consume them (Black Mountain n.d.).
Thinning of a dysphagia product can also cause concern. Starch tends to thin in acidic conditions found in many juices and foods. It is also less temperature stable than xanthan. As heat increases, starch swells and thickens, while xanthan remains more stable. Freezing starch products followed by thawing can result in separation of the starch from the liquid, increasing the risk of aspiration. Xanthan maintains its consistency throughout freezing and thawing without separating.
Furthermore, human saliva contains an enzyme called amylase. Amylase breaks down amylose and amylopectin – the two components of starch – separating the starch and water and thinning the beverage. A patient with dysphagia generally takes more time to eat than someone who does not have a swallowing disorder. The longer the saliva is exposed to the starch product, the more the starch breaks down and the more separation occurs between the liquid and the thickening agent. Xanthan products are amylase resistant, so unlike starch, the enzyme has no effect on the xanthan molecule, reducing the risk of aspiration.
Aesthetics play a large part in how we perceive and enjoy food and beverages. We expect water to be clear. Starch makes water appear cloudy rather than transparent, whereas water mixed with xanthan is much clearer. This can make it more appetizing to the patient, which may lead to better compliance, influencing the patient to stay better hydrated. In addition, xanthan has a smooth texture, while starch tends to be grainy, especially right after mixing with liquid.
Xanthan is a more effective choice of beverage and food thickener for patients with dysphagia. Compared to starch, less product is needed to achieve a desired viscosity; the viscosity remains more stable over time and consistent over a range of temperatures; xanthan does not cloud beverages; and it presents a lower risk of aspiration.
Links of Interest
Thick-It Food and Beverage Thickener: http://thickit.com/
GLOSSARY OF TERMS
AMYLASE — An enzyme that catalyses the hydrolysis of starch into sugars. It is present in the saliva of humans and some other mammals, where it begins the process of digestion.
POLYSACCHARIDE — Polymeric carbohydrate molecules composed of long chains of monosaccharide units bound together by glycosidic linkages and on hydrolysis give the constituent monosaccharides or oligosaccharides. They range in structure from linear to highly branched.
STARCH — A carbohydrate consisting of a large number of glucose units joined by glycosidic bonds.
THICKENED PROTOCOL — Or Thickened Liquid Protocol, those patients who have difficulty swallowing that must drink thickened liquids to prevent choking and stop fluid from entering the lungs. The three common consistencies of thickened liquids are nectar thick, honey thick, and pudding (or spoon) thick.
VISCOSITY — The state of being thick, sticky, and semifluid in consistency, due to internal friction. A quantity expressing the magnitude of internal friction, as measured by the force per unit area resisting a flow in which parallel layers unit distance apart have unit speed relative to one another.
XANTHAN GUM — A polysaccharide secreted by the bacterium Xanthamonas campesteris, used as a food additive and rheology modifier. It is composed of pentasaccharide repeat units comprising glucose, mannose and glucouronic acid.
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Leonard, R., PhD, White, C., MA, McKenzie, S., MS, & Belafsky, P., Md. PhD. (n.d.). Effects of Bolus Rheology on Aspiration in Patients with Dysphagia.
Dysphagia (2014) 29:737-807 p744-5
Domer, Amanda et al. (2014). The Effects of Aspirated Thickened Water on Survival of Pulmonary Status in a Lagomorph Model. UC Davis Study.
Black Mountain case study, data on file (n.d.).
Kemboi, J. and Karunanithy, C. (n.d.). The addition of supplements to different brands of nectar consistency thickened water and their effect on viscosity over time:
An overview. University of Wisconsin.
Stetzer, Douglas A. Thickener Composition, Thickened Nutritive Products, Methods for Preparing Thickened Nutritive Products and Methods for Providing Nutrition. 11 Aug. 2015