Textural Measurement of Gelatine

Gelatine has become well established as a vital ingredient in many products, due to its multi-functional gelling, thickening, elastic and foaming properties.

A pure and naturally-sourced ingredient, gelatine is used to improve texture, appearance and sensory enjoyment. Selection of the correct gelatine and the right combination of gelling agents is vital to provide either soft, malleable textures or a smooth, firm end product, depending on application requirements. 

Multi-functioning gelatine

Gelatine is widely used for its varied functionality as a stabiliser, texturiser and thickener in many foods from confectionery, desserts and dairy products to meat and fish. In confectionery products, it offers plasticity, elasticity and chewy qualities and is easily incorporated into production processes. Effectively used in gelled desserts, gelatine provides gel strength and stability, allowing the ‘wobble’ in jelly, without affecting colour or taste.  Meanwhile, gelatine has become well established as a vital component in soft elastic capsules and two-piece hard capsules for pharmaceuticals and dietary supplements. Its thermoelastic properties ensure active ingredients are transported safely but break down effectively inside the body.

Two types of gelatine exist: type A, sourced from pig skin through an acid process and type B, produced from bovine hides or bones via an alkaline process. When incorporated into different products, each type brings its own advantages. For example, type A gelatine offers a lighter colour than gelatine derived from bones – providing good visual appearance. 

A major factor which influences selection of gelatine type is bloom strength. This refers to one of gelatine’s primary functions – technical strength, where a high bloom value signifies a greater gel strength – which ultimately determines the price. Other important considerations include viscosity, particle size (mesh), setting characteristics, pH value, foaming capacity, clarity, ash content and isoelectric point. 

Generally speaking, gelatines of the same type with a high bloom strength have a high viscosity and vice versa. Type B gelatines tend to have a higher viscosity than type A where the bloom strength is the same. By selecting the right gelatine, the ideal ‘gumminess’ and elasticity is achieved, without stickiness, air bubbles or tails (ie moulded deposits). Different textures can be developed by using higher concentrations of a low bloom gelatine to create a chewy, elastic texture (eg for wine gums). Alternatively, a lower concentration of a high bloom gelatine can be used to create a harder, smoother texture (eg for gummy bears). 

The setting point of gelatine is the temperature at which a gelatine solution forms a gel. This, combined with high bloom strength, is particularly important in the manufacture of marshmallows and other aerated confections, as quick setting and short solidification times are vital to prevent stoppages in production. Gelatine plays a multi-functional role in marshmallows, ensuring a light, fluffy foam texture which is soft but not sticky. It also provides stability during transport and storage and helps extend shelf life.

Bloomin’ power  

Gelatine has thermoreversible properties; when cooled, it forms a gel but this liquiefies at temperatures above 25-35ºC. This characteristic provides ‘melt-in-the-mouth’ qualities which are highly sought after, particularly by confectionery manufacturers. Since varying grades of gelatine produce different gel strengths at the same concentration, variations in texture can be achieved by changing either the concentration or the bloom strength of the gelatine. So, for products that are eaten chilled, such as jellies, a low bloom strength tends to be more appropriate as it softens better than gelatines with a high bloom strength.

To determine the bloom strength prior to incorporation of gelatine into end products, a number of testing methods are available. One innovation in testing instrumentation which provides quicker and more accurate results, used as the international standard (ISO 9665), is the Bloom probe from Stable Micro Systems. Attached to the company’s TA.XTplus texture analyser, the probe allows manufacturers to obtain a force reading at 4mm penetration which is translated as the ‘bloom strength’ of the gel. 

Typically 12.5% concentration of gelatine in cold water is left to soak for around three hours, not exceeding temperatures of 22ºC. The solution is heated in its container up to 60°C for approximately 15 minutes to ensure that the gelatine is fully dissolved. This is then poured immediately into standard bloom jars and covered, before being left to condition for 17 hours in a water bath at 10°C. Following this preparation procedure, the bloom jars are placed under the standard Bloom probe to commence testing. 

At a trigger force of 4g, the probe penetrates the gel to a depth of 4mm. The force reading at this depth is then obtained and interpreted using Exponent software, linked to the TA.XTplus texture analyser to provide the final bloom strength of the gel.  The graph below shows results of a test carried out on two types of gelatine gel, where the final bloom strengths were 300 and 150. 
  
In addition, if measurement of the rupture force or gel brittleness / elasticity is also required, the test can be adapted so that penetration continues beyond 4mm in depth into the bloom jar – as shown in the graph above. 

Unlike previous, more antiquated methods of testing gelatine, the TA.XTplus provides accurate, consistent and repeatable results. This instrumentation is now recognised as the industry standard by the Gelatine Manufacturers Institute of America and has since been adopted by the majority of leading gelatine manufacturers worldwide.
  

Conclusion

With its multi-functional attributes, gelatine is used in an array of applications. By understanding its bloom strength and other textural properties, manufacturers can adapt this vital ingredient to achieve specific textures and organoleptic profiles for their products. As new methods of testing gelatine are developed and recognised by international food industry associations, the selection of the correct gelatine is becoming more straightforward for manufacturers.

EDIBLE FILMS ARTICLE

Request our article for a fuller insight into this fascinating area of texture analysis testing...

---

We can design and manufacture probes or fixtures for the TA.XTplus texture analyser that are bespoke to your sample and its specific measurement.

Once your measurement is performed, our expertise in its graphical interpretation is unparalleled. Not only can we develop the most suitable and accurate method for the testing of your sample, but we can also prepare analysis procedures that obtain the desired parameters from your curve and drop them into a spreadsheet or report designed around your requirements.

For more information on how to measure texture, please visit the Texture Analysis Properties section on our website.

The TA.XTplus texture analyser is part of a family of texture analysis instruments and equipment from Stable Micro Systems. An extensive portfolio of specialist attachments is available to measure and analyse the textural properties of a huge range of food products. Our technical experts can also custom design instrument fixtures according to individual specifications.

No-one understands texture analysis like we do!

To discuss your specific test requirements click here...