Gels and Hydrocolloids
Gels are commonly used within the food industry as they form an extremely versatile and effectively processed ingredient. Gels as a thickener, binding agent, adhesive property, stabiliser and whipping agent among other functions. Every food sector is influenced by the use of gels in their products and cannot be easily replaced by any other ingredient. Gelatine has industry standard Bloom strength tests to grade and qualify its gelling properties and other agents (hyrocolloids) may be tested in similar ways.
Gelling agents are also used in the pharmaceutical and cosmetics industries to provide desirable texture.
Typical gel products tested include:
- mixed polysaccharides
- starch gels
- tara gum
- xanthan gum
Benefits of Gel Texture Testing
- Optimisation of ingredient functionality and blend characteristics of edible gelatines for industrial markets
- Raw material control and quality payment between manufacturers, customers and processors
- Product formulation and development to gain maximum functionality from gelatine used
Gel Testing Fixtures
Specific fixtures and accessories are required for Bloom strength testing. The gel sample bottle and probes have exact specifications in terms of dimensions and materials. The range of gel industry fixtures conform to ISO 9665, GME, AOAC 1985 and BS757 standards.
Test Methods for the Gels and Hydrocolloids Sector
Instrumental measurements are used to assess the functional properties of hydrocolloid gels, usually relating to its firmness and eleasticity, by compression (or occasionally penetration) of the surface. The measurement of gelatin and other gelling agent strength, for example, is an integral part of its quality assessment and grading. Gel strength has been shown to directly relate to the functional performance of the product, independent of its application. Preparation of the sample and test conditions imposed are of critical importance and directly influence the response of the sample being tested. The importance of accuracy and reproducibility of results is compounded when we consider that the majority of hydrocolloid systems are sold based upon their functional properties.
Bloom Strength Test
A key example of standardised gel testing is the long established gelatin Bloom strength test. Originally established within the British Standards Method (B.S. 757:1975), this test method has since been modified by the Gelatine Manufacturers of Europe (GME). This technique strictly defines the preparation of the gelatin sample, the test conditions (speed, trigger point, deformation distance, test probe etc.) and instrument specification used to make the test, which performs a controlled compression of the surface. The end result is an empirical test method that follows fundamental principles for standardisation and control. The principle reason for gelatin producers to establish a standardised technique is that gelatin is graded by its Bloom value, where higher values mean higher prices, hence uniformity in its quantification is critical in a world market. The Bloom strength relates to the force required to deform the gel, typically in the range 50 Bloom gelatin to 300 Bloom gelatin. Values below 120 are graded as low, those above 200, high and those in between, medium strength.
Samples of commercial gelatine were prepared and evaluated following recommendations from the Gelatine Manufacturers of Europe (GME) Monograph 2004 and ISO 9665.
Gel strength is used by the world’s gelatine producers and end-users as a key quality indicator. The functionality of gelatine is directly influenced by its strength, when prepared in accordance to the gelatine Bloom test. The Bloom value obtained is dependent upon sample preparation and evaluation. As higher Bloom values mean higher prices, the industry self-regulates itself. This helps guarantee accurate measurement of Bloom strength between the laboratories of customers and suppliers.
Key areas of standardisation are:
- standardised test probe
- concentration and molecular weight
- temperature during mixing and tempering
- hydration times
- test vessel dimensions
- instrumental accuracy and resolution
- test speed
- depth of penetration from trigger
Standard guidelines for sample preparation and gel strength measurement are fully established and enforced by the relevant geographic manufacturing bodies. The gelatine samples supplied were evaluated following relevant European recommendations for the concentration, preparation and tempering of gelatine gels.
The rigidity of the prepared gel was then tested with the AOAC 12.7mm diameter probe with no radius as per GME recommendations, July 1998, following traditional puncture principles.
Bloom - Optimisation of ingredient functionality and blend characteristics to the edible gelatines and industrial markets.
Strength - Raw material control and quality payment between manufacturers, customers and processors.
Elasticity / Modulus - Product formulation and development to gain maximum functionality from gelatine used.