Fruit Texture: How to measure consistency of fruit preparations

The market for fruit preparations continues to grow, in large part due to their health and natural image.

The addition of fruit is immediately seen to add value, as well as sophistication, to products, from yoghurt to fresh cheese and ice cream. Consumers look for a high level of large fruit pieces, evenly suspended, with a natural texture.

Today fruit preparations are technologically advanced ingredients which can fit perfectly into the end user’s applications – sweet and viscous or low in fat, but very high in fruit content. The correct stabiliser system is also crucial for obtaining the desired texture from the fruit preparation. Modified starches, gums and gels are essential to control viscosity and texture and to guarantee the stability of the fruit preparation.

In applications where fruits are highly refined (i.e. further removed from their natural state), there is a myriad of factors that has a potential impact on the final texture profile. Achieving the desired composition and balanced texture then becomes a more delicate process, as alteration of one ingredient can affect another. For example, the addition of a starch or similar ingredient performs a necessary stabilising function in fruit-based preparations such as jams, jellies and preserves, but can at the same time impart undesirable influences on texture.

A home-made feel is popular with consumers of such products, and quality is often judged on piece integrity and fruit-to-syrup/jelly ratio. For manufacturers and product developers, objective assessment of texture tells of a fruit’s processing tolerance and stability, as well as the effects of various manufacturing methods and ingredients.

Texture Measurement of Soft Pastes and Pulps (purées, pulps, weak jellies and sauces)

Pulps and purées are very thick and viscous slurries made from processed fruit that are often concentrated and include fibrous material or fruit pieces that adds structure. 

They are commonly used for yoghurt, fromage frais or chilled dairy desserts, ice cream inclusion, fillings or toppings for pies, frozen desserts or fresh cakes.

In jarred, homogenous products, a Back Extrusion test (as shown left) is carried out by fixing a suitable diameter disc to the TA.XTplus texture analyser; the disc moves down into the vessel with good clearance between the vessel and disc so as not to produce erroneous increase force readings due to ‘side effects’.

Testing within the sample container is often the only means of assessing the product reliably where depositing the sample into an alternative vessel for testing may cause disruption of the structure of a ‘gelled’ product. The disc moves down into the product to a chosen distance (up to 75% of the depth of the product depending upon vessel height) and the area under the positive region of the resulting curve is taken as an indication of product consistency/overall firmness.

Texture Measurement of Fruit Gels (jams, preserves, jellies)

In many regions, the season for fresh fruit, particularly berries, is short and as a result very few industrially processed jams are made from fresh berries during the harvesting season. Instead, frozen berries are commonly used.

Unfortunately, the freezing and the heating processes needed for jam making have a negative effect on fruit texture. In order to maintain the original shape of the fruit, it is sometimes necessary to pretreat it to modify its structure.

Consumers demand high quality jams with more natural flavour, colour and whole fruit content. The changes in the texture of berries appear as tissue softening and loss of cohesiveness and the addition of calcium or crystallised sucrose is often necessary to fortify the fruit or act as a dehydrating agent in order to decrease the water content of the fruit, respectively. 

Manufacturers of such products may then require a means of determining which pre-freezing and processing factors dominate in the modification of final jam texture to determine the most favourable ranges to obtain the highest quality jam.

For testing non-homogenous samples, such as jam or marmalade containing fruit pieces, a Multiple Puncture Probe (as previously described, and shown right) can be used. Testing within the product’s standard vessel, i.e. its jar, eliminates the risk of structure disruption in transferring the product into a testing container.

Watch the video below to see a summary of the types of testing possibilities that are available for the measurement of fruit and vegetable texture to provide quality control tools and ultimately, consumer satisfaction:

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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.

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