What is Bloom Strength?

Bloom strength is one of the most important measures used to describe how a gelatin will perform. But what does the term mean, and why does it matter when manufacturers select gelatin for a particular application?

When gelatin is dissolved in warm water and cooled, its protein chains partially reconnect to form a three-dimensional network. This network traps water and creates the characteristic gel structure associated with gelatin.

Bloom strength measures the firmness of that gel under standardised testing conditions.

How is Bloom strength measured?

To measure Bloom strength, a gelatin solution with a concentration of 6.67 per cent is prepared and held at 10°C for approximately 17 hours. A standard plunger is then pressed 4 millimetres into the surface of the gel.

The force required to create this depression is recorded in grams and expressed as the gelatin’s Bloom value. For example, a gelatin rated at 250 Bloom requires more force to depress than one rated at 150 Bloom.

Under the same formulation and processing conditions:

• a lower-Bloom gelatin generally produces a softer, weaker gel;
• a medium-Bloom gelatin provides moderate gel strength; and
• a higher-Bloom gelatin generally produces a firmer, stronger gel.

Commercial gelatins are available across a broad range of Bloom strengths, allowing manufacturers to select a grade appropriate for the required product characteristics.

How do manufacturers achieve different Bloom strengths?

Bloom strength is influenced by several parameters throughout the gelatin manufacturing process, particularly those that affect the conversion of insoluble collagen into soluble gelatin.

Bloom strength is closely related to the average length, or molecular weight, of the gelatin protein chains. Longer protein chains generally contribute to a higher Bloom strength, while shorter chains generally produce a lower Bloom strength.

The process begins with the controlled treatment of collagen-rich raw materials such as bones, skins and hides. This treatment opens the collagen structure and breaks some of the cross-links between the protein chains, allowing the collagen to be converted into gelatin.

Partial chemical hydrolysis is required before extraction. This reduces the amount of heat needed to release the gelatin from the collagen structure while helping manufacturers retain the protein-chain characteristics required for the finished product.

During extraction, two of the most important variables are:

• temperature; and
• pH.

These conditions influence the extent to which the gelatin protein chains are broken down during extraction.

In general, lower extraction temperatures help preserve longer protein chains and support a higher Bloom strength. Higher temperatures can cause greater protein-chain breakdown, resulting in a lower Bloom strength.

By carefully controlling raw-material preparation, treatment conditions, pH, temperature and extraction time, manufacturers can produce gelatin with the targeted Bloom strength and performance characteristics required for different applications.

Finished-Product processing conditions

The same underlying science applies when gelatin is used in a finished-product formulation.

Prolonged exposure to high temperatures can continue to break down the gelatin protein chains. This effect can be accelerated under strongly acidic conditions.

Holding a gelatin solution at a high temperature, particularly at a low pH, for an extended period may therefore reduce its effective gel strength. In some formulations, this can produce a softer-than-expected texture or prevent the product from setting correctly.

Manufacturers must consequently consider not only the original Bloom value of the gelatin, but also how the gelatin is handled during hydration, dissolution, processing and holding.

Higher Bloom does not necessarily mean better gelatin

Bloom strength is not a simple measure of overall gelatin quality.

A higher-Bloom gelatin may be appropriate when a manufacturer needs a strong gel, good shape retention or a particular level of elasticity. A lower-Bloom gelatin may be preferred when a softer texture, gentler set or different processing behaviour is required.

The best gelatin is therefore not necessarily the one with the highest Bloom value. It is the gelatin that delivers the required performance in the finished product.

Why does Bloom strength matter?

Bloom strength can influence several aspects of product formulation and performance, including:

Texture and firmness

Higher-Bloom gelatins can create firmer gels at the same concentration. Lower-Bloom grades can provide softer or more flexible textures.

Gelatin concentration

A gelatin with greater gel strength may allow a manufacturer to achieve a target firmness using a different concentration. However, changing the concentration can also affect mouthfeel, elasticity and other product characteristics.

Setting and processing behaviour

Bloom strength can contribute to how a product develops structure as it cools. The required setting behaviour will depend on the formulation, manufacturing process and intended end use.

Product stability

The gel network can help products retain their shape and resist deformation during handling, packaging, storage and distribution.

Sensory experience

In food applications, Bloom strength can contribute to bite, chew, elasticity and melt-in-the-mouth characteristics. By varying gelatin concentration and Bloom strength, manufacturers can produce textures ranging from firm and elastic to soft and delicate.

Different applications require different Bloom strengths

Gelatin performs many functions across food, pharmaceutical and nutraceutical products. The appropriate Bloom strength depends on the product and the performance required.

For example:

• Confectionery products may require a specific combination of firmness, elasticity and chew.
• Dairy desserts may need a softer gel with a smooth, delicate mouthfeel.
• Meat products may use gelatin to support binding, structure and water management.
• Capsules require gelatin with carefully controlled mechanical and processing properties.
• Gelled desserts may need sufficient strength to hold their shape while still melting pleasantly in the mouth.

Even within the same product category, formulations, production equipment, storage temperatures and consumer preferences can lead to different gelatin specifications.

Bloom strength is only part of the specification

Bloom strength is important, but manufacturers should not consider it in isolation.

Other relevant gelatin characteristics may include:

• viscosity;
• clarity and colour;
• elasticity;
• melting and setting behaviour;
• particle size;
• microbiological requirements;
• compatibility with other ingredients; and
• processing and storage conditions.

Bloom strength and viscosity, for example, are separate technical properties. Two gelatins with a similar Bloom value may not necessarily have the same viscosity or behave identically during manufacturing.

Bloom strength is becoming more relevant to home cooks

Manufacturers have long specified gelatin by Bloom strength to achieve the required texture and performance in finished products.

Increasingly, gelatins with different Bloom strengths are also becoming available at retail, giving home cooks greater control over the firmness, texture and behaviour of their gelatin creations.

Understanding Bloom strength can therefore be useful not only for food manufacturers and product developers, but also for consumers choosing gelatin for different recipes and applications.

Bloom strength is not the same as blooming gelatin

The terminology can sometimes cause confusion.

Bloom strength is the measured gel strength of a gelatin.

Blooming gelatin refers to the preparation step in which gelatin is hydrated in cold water before it is dissolved.

Correct hydration is important for achieving consistent gelatin performance, but it is different from the laboratory test used to determine Bloom strength.

Selecting the appropriate gelatin

Choosing the right gelatin begins with understanding the required function of the finished product.

Manufacturers should consider the desired texture, processing conditions, product composition, storage requirements and consumer experience.

Technical trials may then be used to confirm that the selected gelatin delivers consistent performance within the complete formulation.

Bloom strength provides an essential starting point, but successful gelatin selection requires consideration of the product and process as a whole.

Read more on: How Manufacturers Choose the Right Gelatin