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11th November 2015


How to Increase the Firmness of Fresh and Frozen Fruit

The summer is upon us and one of the greatest pleasures of the summer months is delicious soft fruits such as strawberries and raspberries. However, for food processors, these fruit may present difficulties, as sometimes fruit & vegetables can be damaged during processing. One of the most significant problems is tissue softening, largely due to endogenous enzymes within the fruit, which depolymerise and solubilise pectin.  This can limit the shelf life of fruit and lead to unwanted waste when manufacturing products such as fruit preparations. So how can you improve fruit firmness?

The firmness of soft fruit and vegetables can be increased with the addition of a pectin methyl esterase (PME) enzyme and calcium. PME removes methyl groups in pectin, thus generating free carboxyl groups. The free carboxyl groups are able to cross-link with calcium ions and form a network of pectin chains and calcium known as the “egg-box” model, which adds valuable rigidity to the plant tissue.

Improve Fruit Firmness – Fresh Strawberries

Fresh strawberries treated with our PME, Pectinase 872L, and calcium ions were shown to be more than three times as firm as those without PME treatment. Hence, using Pectinase 872L will improve fruit firmness.

Improve Fruit Firmness with Pectinase 872L


Improve Fruit Firmness – Frozen Raspberries

Freezing causes texture loss of plant-based foods due to intercellular and intracellular ice crystal formation. These ice crystals initiate the rupture of cellular membranes and cell walls, leading to texture losses. On thawing, the damage is not reversed; cells remain collapsed, resulting in a mushy texture of many fruit and vegetables. Pectinase 872L has been shown to increase the firmness of frozen raspberries by up to 60%.

For more information on using enzymes to improve fruit firmness, download our technical bulletin.

By Thomas Parkhill

Internal Sales Executive


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