Ultrasound is a safe and sustainable technology that can be used to produce food products of higher quality than those obtained using traditional procedures. Here you can learn how ultrasound processing works and how it can be used in the food industry.
Although ultrasound is a well-known technology and is commonly used in several fields, such as medicine or in the automobile industry, its use in the food industry is still scarce.
Ultrasound in the food industry can be used as alternative to conventional food processing with a wide range of applications, leading to the production of safer and higher quality products than those obtained by traditional procedures. In addition, ultrasound is considered a safe, nonpolluting, and environmentally friendly technology, and the lower implementation cost of some applications compared to other nonthermal technologies such as pulsed electric fields or high hydrostatic pressures might facilitate its industrialisation in some food sectors.
Further research is still necessary for some applications since many factors must be considered when designing equipment and applying ultrasound treatments in the food industry in order to achieve an efficient application.
How to process food using ultrasound
Many factors condition the efficacy of ultrasound treatments. These include treatment parameters (frequency, amplitude, treatment temperature and time) and propagation medium/food parameters (viscosity, solid particles, gas bubbles). In any case, probably the most relevant factors conditioning how an ultrasound-based process is designed and which conditions are chosen are the objective pursued and the type of food to be treated.
Thus, for some applications low intensities are needed because preserving food quality is mandatory, whereas for others, such as extraction of extracellular compounds, high intensity short treatments would be preferred.
Applications in the food industry
1.Food and surface decontamination
Ultrasonic cleaning is one of the most successful and widely used ultrasound applications. It has already been successfully implemented on an industrial scale for cleaning and decontaminating abiotic surfaces, such as knifes or conveyor belts and has considerable potential for the decontamination (mainly microbial and even even microbial biofilms) of food products, either alone or in combination with other chemical agents, such as acids or disinfectants.
2. Reduction on the content of heavy metals and iodine
Recent studies have demonstrated that, besides microbial decontamination, ultrasound might also be used for reducing the heavy metal load from foods such as crabs and seaweeds, especially when combined with mild temperatures and/or EDTA.
3. Pasteurisation and sterilisation
The lethal effect of ultrasound on food microorganisms and enzymes is reduced but can be increased by combining it with pressure (up to 500 kPa) and/or heat. These combined processes are capable of inactivating pathogenic and spoilage microorganisms and, therefore, would allow for the pasteurisation and even sterilisation of foods. However, the required ultrasound intensities to achieve these objectives are quite high, which has hampered its industrial implementation (mainly due to technical limitations).
4. Extraction of compounds of interest
Since the microjets and shock waves generated by cavitation can break the cell membranes/envelopes, ultrasound constitutes a very interesting and sustainable alternative to conventional treatments based on the use of heat and/or toxic or contaminant solvents. In addition, since ultrasound also produces a rapid fragmentation of the raw material, the surface area of the solid in contact with the solvent can be increased upon its application, thus accelerating the extraction rate and yield.
5. Increase of heating/freezing rates
Ultrasonic waves can help to accelerate the heating processes both because of 1) its direct effect that leads and because they produce an intense agitation favouring a faster and more uniform heating of the products. On the other hand, the vibration caused by the indirect application of ultrasound can also accelerate the transfer of heat from traditional systems, both to release it in cooling processes and to provide it when heating.
More about ultrasound for drying, freezing and thawing
6. Other applications
- Emulsion formation/stabilisation: Ultrasound can generate more stable emulsions (e.g. mayonnaise) than conventional agitation methods and can even be used for the homogenisation of milk. More recently, it has has been proposed as a new method of encapsulation in the food industry
- Defoaming and degassing capacity: The degassing capacity of ultrasound has been known for years and it is a common and established method for degassing liquids in many laboratory applications, having the advantage of not substantially increasing the temperature of the liquid. Ultrasound is also a mechanical method of foam removal that can help in some processes such as product filling helping reduce the use of anti-foam chemical additives.
- Filtration: Ultrasound can help prevent the saturation of membranes or clean them and, therefore, it can facilitate processes such as filtration, ultrafiltration, dialysis, and reverse osmosis.
- Cutting of foods: Blades provided with ultrasonic probes have been successfully used in the cutting of fragile, heterogeneous, and sticky products such as cream cakes, bread, pastries, biscuits, and cheese.