Direct Contact Ultrasound in Food Processing: Impact on Food Quality

Abstract

Consumers' demand for “minimally processed” products that maintain the “fresh-like” characteristics has increased in recent years. Ultrasound (US) is a non-thermal technology that enhances mass and energy transfer processes resulting in improved food quality. A new method of applying US to food without using a liquid or gaseous medium for the propagation of acoustic waves has recently been under research. It is known as direct contact US, since the food is directly placed on a plate where the transducers are located. In this type of systems, the main effect is not cavitation but acoustic vibration, which encourages mass and energy transfer processes due to the “sponge effect.” Furthermore, as the product is not immersed in a liquid medium, the loss of hydrophilic nutritional compounds is reduced; systems such as these can thus be more easily implemented on an industrial level. Nevertheless, the very few studies that have been published about these systems mainly focus on dehydration and freezing. This article summarizes published research on the impact of direct contact US in nutritional and organoleptic quality of food in order to assess their potential to meet new market trends.

Advances, Applications, and Comparison of Thermal (Pasteurization, Sterilization, and Aseptic Packaging) against Non-Thermal (Ultrasounds, UV Radiation, Ozonation, High Hydrostatic Pressure) Technologies in Food Processing

“…US can significantly assist se eral industrial processes such as filtration, freezing, separation, drying, emulsion, tha ing, brining, oxidation, homogenization, meat tenderization, sterilization, and extracti thanks to their capability of improving energy and mass transfer, mixing, and retenti of food characteristics as well as reducing thermal and concentration gradients [56][57][58][59][60][61] Additionally, if ultrasounds are applied previous to drying, an enhancement in dr ing kinetics is always observed, implying a positive effect on the drying process and reduction in total energy consumption [4,5]. Furthermore, if the product it is not soak in a liquid medium, the loss of hydrophilic nutrients and compounds is reduced [62].…”

Revisiting Non-Thermal Food Processing and Preservation Methods—Action Mechanisms, Pros and Cons: A Technological Update (2016–2021)

“…The sponge effect, also termed as mechanical stress, refers to the successive compressions and expansions of the food material like a sponge due to the effect of acoustic vibrations on a solid matrix. The effect mostly occurs when ultrasound is applied in dry conditions [ 66 ].…”

“… Schematic diagram showing the cavitation and sponge effect of ultrasound technology (Source: Astráin-Redín et al [ 66 ]; permission to use not required). …”

Optimization of temperature and extraction time for the nutritional and phytochemical contents of corn bran with ultrasonic-method

“…From Table 2 it is known that the higher the temperature and the longer the extraction time, the yield of the extract produced will be lower. This is by following per under research conducted by [26], [27]. The higher the temperature and the longer the time of extraction, the lower the yield obtained.…”