Texture Analysis – a Beginner's Guide

What is Food Texture and how is it measured?

Texture refers to those qualities of a food that can be felt with the fingers, tongue, palate, or teeth. Foods have different textures, such as crisp crackers or potato chips, crunchy celery, hard candy, tender steaks, chewy chocolate chip cookies and sticky toffee, to name but a few.

Texture is also an index of quality. The texture of a food can change as it is stored, for various reasons. If fruits or vegetables lose water during storage, they wilt or lose their turgor pressure, and a crisp apple becomes unacceptable and leathery on the outside. Bread can become hard and stale on storage.

Does it flow, bend, stretch or break? From a sensory perspective, the texture of a food is evaluated when it is chewed. The teeth, tongue and jaw exert a force on the food, and how easily it breaks or flows in the mouth determines whether it is perceived as hard, brittle, thick, runny, and so on.

Instrumental evaluation of texture involves measuring the response of a food when it is subjected to forces such as cutting, shearing, chewing, compressing or stretching. Food texture depends on the rheological properties of the food. Rheology is defined as the science of deformation and flow of matter or in other words, reaction of a food when a force is applied to it.

What is Food Texture Analysis?

It is the science we use to objectively measure the subjective mechanical characteristics of a food product.

We use Texture Analysers to imitate or create controlled stresses within the sample just as we do when we consume or use a product. The science of texture measurement (texture analysis) falls across the scientific fields of rheology (the science of material flow) and materials science.

Texture Analysis itself is the study of the deformation and flow of a food when under the influence of stress and includes the assessment of raw materials, intermediate components and finished products.

From a manufacturer's perspective, food texture analysis could be assessing the functionality of an ingredient within the production process or its effect on the finished product. From a customer's perspective, food texture analysis could be a vital assessment to ensure an anticipated or expected sensory property, quality or functional performance of a food.

What is a Texture Analyser? How does a Texture Analyser work?

A Texture Analyser moves in either an up or down direction to compress or stretch a sample.

The travelling arm is fitted with a load cell and records the force response of the sample to the deformation that is imposed on it. Force, Distance and Time data is collected and usually presented as a curve on a graph which, when analysed, indicates the texture of the sample.

Texture Analysers provide the operators with ultimate control and test flexibility for measuring all types of physical/textural properties of solid and semi solid systems by their ability to accommodate a wide range of probes and fixtures that can be attached to the Texture Analyser base and/or arm.

Depending upon the chosen probe/fixture the Texture Analyser can perform compression, extension, cutting, extruding, bending and shearing tests – and in doing so, can measure properties such as fracturability, chewiness, stickiness, consistency, bite force and springiness, to name but a few.

Why Measure Texture?

Successful production and quality control depends on the ability to measure and test at the various stages of production of a product. If you can’t measure it, you can’t control it!

It will certainly prove an indispensable tool when you need to quantify the texture or overall physical properties of your 'gold standard' product for future comparison in manufacture – the key to maintaining consistent textural quality. You could even use it to compare the texture of your product with your competitors!

For more detail on this topic, head to our Measure Texture page.

Food Textural Properties and Mouthfeel – the Vocabulary of Food Texture

The term 'food texture' embraces a large number of textural characteristics which are identified and evaluated by the consumer in a well-defined order during mastication.

The term mouthfeel is a general term used to describe the textural properties of a food as perceived in the mouth. To people who study food and eating, there are some important variables known as texture and mouthfeel characteristics/properties, and they can make food appealing or not.

For example:
• the crispiness of a potato chip from a newly-opened bag
• the crunchiness of a just-picked Gala apple or Bosc pear
• the springiness of freshly baked bread
• the resiliency of a piece of strawberry licorice
• the chewiness of bubble gum
• the firmness of jam
• the spreadability of ripe Brie cheese
• the firmness of an old fashioned, New York style bagel

Subtle changes in a food product's formulation can change mouthfeel significantly. Simply taking out sugar and adding a high-intensity sweetener can cause noticeable alterations in texture and mouthfeel, making a formerly-good product unacceptable to consumers.

Sensory Analysis vs. Texture Analysis

Sensory tests and verbal descriptor terms are highly useful in understanding product texture/rheology.

However, sophisticated instruments such as the TA.XTplus Texture Analyser, designed for rheological/textural food measurements, are becoming more and more common, easier to use and better able to provide reliable, meaningful data. "Meaningful" means that the data from these physical instruments correlate very well with the sensory judgments rendered by humans.

Consumer evaluation of textural characteristics and mouthfeel can be time-consuming and the data difficult to analyse, so it is extremely useful to replace this method of evaluation by instrumental methods. Texture Analysers are used to measure many properties, such as Hardness, Brittleness, Spreadability, Adhesiveness, Tensile Strength, Extensibility, etc, on a vast range of products.

For a review of the textural properties we are most commonly measuring, visit our Texture Properties page.

The challenge confronting food designers who want to quantify mouthfeel characteristics using an instrumental technique: How to take instrument readings – measurements of forces, distances and other data that look like numbers from a physics experiment – and relate them to something meaningful and relevant to what people actually experience when they taste, chew and swallow a food product.

That's where Stable Micro Systems leads the way – we’re happy to help you develop the correct analysis routines to test your products.

Measuring Food Quality with a Texture Analyser

More than ever before the food industry is finding itself forced, through outside pressures, to improve constantly its product quality and to maintain that quality at a consistently high level.

Food quality is an important concept, because the foods people choose depend largely on quality. Consumer preference is important to the food manufacturer, who wants to gain as wide a share of the market for the product as possible. Quality is difficult to define precisely, but it refers to the degree of excellence of a food and includes all the characteristics of a food that are significant, and that make the food acceptable.

Texture is one of the major criteria that consumers use to judge the quality and freshness of foods. When a food produces a physical sensation in the mouth (hard, soft, crisp, moist, dry), the consumer has a basis for determining the food's quality (fresh, stale, tender, ripe). Sometimes, texture is the primary aspect of the food and the main focus of its acceptability. Cucumber pickles, for example, are evaluated for quality by the consumer primarily on the basis of texture. In one survey, 400 consumers were asked, "What should a good pickle be like?" Almost 90% answered that a good pickle should be crisp, firm and hard.

Companies must also monitor the quality of their products during storage, when changing ingredients, and when developing new lines. If fruits and vegetables lose water during storage, they wilt or lose their turgor pressure, and the crisp apple becomes unacceptable and leathery on the outside. Bread can become hard and stale on storage. Products like ice cream can become gritty due to precipitation of lactose and growth of ice crystals if the freezer temperature is allowed to fluctuate, allowing thawing and freezing.

Objective evaluation of foods involves use of physical techniques to evaluate food quality such as texture analysis. Evaluation of texture with a Texture Analyser involves measuring the response of a food when it is subjected to a force, such as cutting, shearing, chewing, compressing, or stretching. Such tests are essential in the food industry, especially for routine quality control of food products.

Where will I use a Texture Analyser?

More often not, texture analysis is applied in a practical and open manner. Core characteristics are identified through sensory or consumer studies, and tests are undertaken by replicating the conditions through instrumental means.

Texture measurements can be used for:

a) Research and Development: In longer term studies to understand micro and macro structures or in the development of new ingredients or unique products.

b) New Product Development: In faster moving and shorter term investigations to benchmark key attributes. The Texture Analyser would assist in the development of products with specific consumer markets in mind and monitoring of the effect of formulation and shelf life changes.

c) Process Development: The Texture Analyser would be used in an engineering approach to measurement to form an understanding of key stages in the product process. The effects of these stages and how they can be manipulated to maximise product quality would be observed. From each of these environments a technologist would learn and transfer information to its practical application at the factory level.

Factory based texture measurements must be simple, reproducible and reliable. Factory measurements on the Texture Analyser would provide real benefits in terms of reducing product waste, production line down time and reduced consumer satisfaction from product non-conformance.

True quality control comes from the ability to use the Texture Analyser to measure manufactured products to desired quality standards and understand how you can alter the formulation or processing conditions should they deviate beyond acceptable tolerance levels.

The texture of a product is a critical consideration to the consumer – if they don't like how something feels, they won't buy it again. If the optimum physical properties of a component or ingredient are wrong you won't be able to maintain optimum processing efficiency and as such will experience higher product wastage and down time.

Worst case scenario – if you can't give the supermarkets what they want and in a consistent manner, they will simply move to a new supplier.

Stable Micro Systems Blog Posts that you may also find interesting:

• Sensory Analysis vs. Texture Analysis
• Sensory Analysis and Definitions of Food Texture
• The Importance of Texture in Food
• The Desire to Chew
• The Vocabulary of Food Texture
• Food Texture around the World
• Food Texture – Likes and Dislikes