What is IDDSI?
Texture-modified foods and thickened fluids are essential components of clinical treatment for people who have trouble swallowing (a condition known as dysphagia). Some dysphagia sufferers have problems swallowing certain foods or liquids, while others cannot swallow at all. Coughing or choking when eating or drinking are common symptoms.
Treatment for dysphagia includes changing or carefully controlling the consistency of food and liquids to make them safer to swallow.
To ensure that dysphagia patients receive the proper consistency of food/drink, the International Dysphagia Diet Standardisation Initiative (IDDSI) developed a standardised international terminology and description for texture-modified foods and thickened fluids. While the IDDSI framework provides a standardised texture description (Level 0 to Level 7) and is now widely acknowledged as an international standard, IDDSI texture level testing and assessment are qualitative and subjective. These approaches were designed primarily for use by care workers. However, they are not optimised for use by food manufacturers for product quality control.
Why do we need instrumental methods that imitate IDDSI manual methods?
By using an objective instrumental method, any potential errors caused by subjective manual testing can be removed. A Texture Analyser can repeatedly perform consistent tests at the same speed, compression distances and scooping depths that are required. The superior sensitivity of the instrument can accurately measure the differences between two similar samples that might otherwise be difficult to assess by hand.
Automatic analysis and pass/fail criteria of IDDSI grades can be presented in spreadsheet format. This enables faster sample throughput and removes any requirement to make human judgement. The ability to generate internal frameworks of numbers for each IDDSI funnel category means common methodologies can be shared across sites/labs for comparative testing.
How we developed these Imitative IDDSI tests
The major goal of developing these tests was to create a set of quantitative instrumental procedures that best matched the IDDSI levels as an objective framework and best imitated the manual IDDSI methods. Commercially available liquid and solid foods of varied textures were used to create a set of test samples.
For each category covered by this equipment (Levels 3–7), IDDSI measuring methodologies were employed to evaluate texture grades of these samples on a Texture Analyser:
• Fork pressure test
• Fork drip test
• Fork cut test
• Spoon pressure test
• Spoon tilt test
For each food category, measurement thresholds were established using a combination of manual and instrumental tests. They are presented here as objective complementary techniques to the IDDSI framework.
These thresholds are for guidance only, and operators may wish to determine their own thresholds using known foods.
Third party assessment of our solutions
Tools and methods were developed with independent consultation from Dr Ben Hanson, Associate Professor in Mechanical Engineering at University College London.
The application of instrumental methods
Fork and Spoon Pressure Tests
To check how firm or hard a food is, a Fork/Spoon Pressure Test is best used to assess foods in Levels 4 – EC7 and transitional foods by assessing how the food changes when pressure is applied to the food with the tines/prongs of a fork or the back of a spoon. The slots/gaps between the tines/prongs of a standard metal fork typically measure 4 mm, which provides a useful measuring tool for particle size of foods at Level 5 – Minced & Moist.
The IDDSI recommended method for this test is to apply a fork to a 15mm cubed food sample and observe the food’s behaviour when pressure is applied. The recommended pressure is the level at which the thumbnail blanches white, approximately 17kPa. For the area covered by the food sample, this is equal to 3.825N of force. The Texture Analyser mimics this action by applying 3.825N to the food sample using a fork/spoon probe.
• Precise and repeatable applied force removes operator variation.
• Precise solid sample preparation using custom templates.
• Quick release adapter provides easy removal for cleaning between tests and thereby offers rapid sample throughput.
Fork Cut Test
The fork cut or ‘fork separation’ test mimics the action of a user turning their fork on its side and cutting the food sample and is used to determine whether or not a food sample will break apart easily. The fork cuts almost all of the way through a 15mm cube sample to 1mm above the test platform. If the maximum force during this measurement is below 378g, the sample has passed. Food samples of Levels 4 – EC7 should pass this test.
• Fork Pressure attachment is mounted on its side to perform the fork cut test.
Typical spreadsheet showing Fork Cut test results for various samples
Fork Drip and Spoon Tilt Test
The Fork Drip Test is used to check the correct thickness and cohesiveness in Levels 3-4 foods by assessing whether they flow through or how they hold together on the slots/prongs of a fork and comparing against the detailed descriptions of each level. This test mimics the action of a user pushing a fork into the sample and holding it above the surface.
The spoon tilt test is used to determine the stickiness of the sample (adhesiveness) and the ability of the sample to hold together (cohesiveness). This test mimics the action of a user scooping the sample with a spoon and turning the spoon over to drop the sample.
• Sensitive automated analysis to measure sample behaviour.
• Quick release screw on spoon/fork provides easy removal for cleaning between tests and thereby offers rapid sample throughput.
• Consistent fork/spoon movement through sample.
• Semi-solid sample volume minimised using a custom sample container.
How the attachments work
A range of parts are included that attach to the Texture Analyser to provide the full range of instrumental tests that can be mimicked according to IDDSI manual methods.
IDDSI testing requires a Texture Analyser with a 5kg load cell and Exponent/Exponent Connect or Exponent Lite software.
Pioneers in foods for dysphagia
Some corporations, such as CPKelco, are already using their Texture Analyser in the fabrication of ingredients for these food products.
The National Dysphagia Diet Task Force utilised a Stable Micro Systems Texture Analyser in the book ‘National Dysphagia Diet: Standardization for Optimal Care’ to compare and correlate over 100 different foods to assist in placing them in the proper diet level.