Improved Fruit and Vegetable Gelation by Ultrasonics

Thickening sauces, juices, jams and other foods by gelation is a common process in the production of liquid foods. Ultrasonic extraction of pectins and natural intracellular sugars from fruits and vegetables is a highly efficient method to promote the gelation of food products without addition of refined sugars. Thereby, ultrasonication not only increases economic efficiency by reducing production costs (as sugar and thickening additives are unnecessary), but also helps to produce more healthy, calorie-reduced foods.

Gelation and Thickening of Food Products

The preparation of gels from fruits rich in pectins is a widely established process for the production of various food products including sauces, purees, ketchup, juices, smoothies, marmalades and jams. The thickening and gelation of such foods requires often the addition of sugar in high amounts to achieve the desired degree of gelation. The requirement for refined sugars is mostly necessary as the pectins and natural sugar in fruits and vegetables is entrapped in the cellular matrix of the plant cells, where it remains mostly unused.

The Solution: Ultrasonic Extraction of Pectins and Natural Sugars

Ultrasonication is a well established and widely used technology to extract bioactive molecules from plants such as fruits and vegetables. Therefore, sonication is a valued technique in food processing such as the production of juices, smoothies, beverages, sauces, purees, ketchups, fruit spreads, jams and marmalades, where the ultrasound waves help to release flavour compounds, pectins and sugars (e.g., fructose) from the cellular matrix of the plant material. This means that ultrasound not only promotes the gelling, but also makes food products more flavourful and sweet without the addition of flavours, sugars and other additives. With the increasing demand for natural, low-processed foods, ultrasonic food processing is the ideal technology to create healthy and flavour-intense foods. Ultrasonic pectin treatment of food has been found to be a highly efficient, reliable, energy-saving, and environment-friendly preparation strategy, especially for low-methoxyl pectin.
Pectin is a favoured ingredient in low‐sugar and healthy food products due to its gel‐forming properties. By applying ultrasonic irradiation to fruit- and vegetable-based liquids, the addition of refined sugar can be avoided or significantly reduced, since the functionality of pectin exhibits the desired gelation properties and contributes to favourable rheological properties of the food product.
Additional benefits of ultrasonic food processing include the inactivation of enzymes such as pectin methylesterase as well as the homogenisation (smoother texture) and pasteurization (improved microbial stability).

Ultrasonic pectin, flavour, and sugar extraction from the vegetal cellular matrix has been applied successfully to citrus fruits, oranges, lemons, mangos, passion fruits, apples, pears, peaches, tomato and many other fruits and vegetables.

How to Avoid the Destruction of Molecular Pectin Structure

Ultrasonication can highly promote the gel formation in pectin-containing fruit and vegetable products. However, over-sonication, i.e. an ultrasound treatment with to much intensity or for a too long period, can destroy the molecular structure of pectin thereby decreasing the gelation quality. Hielscher Ultrasonics supplies state-of-the-art ultrasonicators, which allow for exact operation settings, controlling and monitoring of the pectin extraction process. Easily accessible settings, the option to preset and save treatment parameters as well as the remote control via any internet browser makes sure that your product is sonicated under optimal conditions. Furthermore, the data of all ultrasonic runs are automatically recorded on a built-in SD-card, so that every single treatment can be monitored and revised for quality assurance and to fulfil Good Manufacturing Practices (GMP).
Hielscher industrial sonicators can deliver very high amplitudes. Amplitudes of up to 200µm can be easily continuously run in 24/7 operation. For even higher amplitudes, customized ultrasonic sonotrodes are available.
The table below gives you an indication of the approximate processing capacity of our ultrasonicators: