The Swallowing Characteristics of Thickeners, Jellies and Yoghurt Observed Using an In Vitro Model.
Simmi Patel, William J McAuley, Michael T Cook and 3 others
PMID 31707519WHAT IT FOUND
In a mechanical throat model, starch thickener pastes moved slowly, xanthan gum made shorter boluses at nectar-like, and jellies or yoghurt moved like honey-like or spoon-thick fluids.
These lab results may help choose textures, but do not prove patient swallowing safety.
Key findings
01In the throat model, adding more thickener made the bolus take longer to pass and become shorter, but the measured viscosities of manufacturer-recommended thickener mixes did not always match National Dysphagia Diet expectations.
02At nectar-like consistency, the xanthan gum-based thickener produced a significantly shorter bolus length than the starch-based thickener.
03Chewed and free-flowing jellies behaved like honey-like thickened fluids in the model, while yoghurt behaved like spoon-thick Nutilis Powder; dry chopped jellies took over 100 seconds to pass.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study tested materials in a mechanical model, not people with dysphagia, so it does not show what happens in a patient. The model has a static epiglottis and cannot close to protect the airway, and the bolus moves under gravity rather than oesophageal peristalsis. The model applied a fixed tongue pressure of about 10 kPa and does not capture how oral pressure varies with bolus consistency. The in vitro oral transit time was not fully validated as a representation of physiological oral transit for all materials. Thickened fluids were made with deionized water, not the juices, milk or other liquids used clinically, and IDDSI levels were not tested. Some thickener mixes did not match National Dysphagia Diet viscosity ranges when prepared according to manufacturer instructions. Free-standing jellies were chopped or chewed by 12 healthy volunteers, not patients, and the chewed boluses were mixed before testing. Long model transit times, such as over 100 seconds, may not reflect real swallowing and could relate to residue risk, but the model cannot measure aspiration or residue.
Declared interests
The supplied text states the funder was named as the University of Hertfordshire.
The easy way to misread this
Do not read these model transit times as proof that a food is safe to swallow. Thick & Easy spoon-thick took over 100 seconds in the model, which the authors state did not represent physiological oral transit, and the static model cannot mimic epiglottis closure or normal oesophageal movement.