Drying is a critical step in the processing of plant-based foods and ingredients, particularly those sensitive to heat. Conventional thermal drying methods often degrade nutritional and functional qualities. As the food industry shifts toward electrification and sustainability, novel non-thermal technologies are needed to meet consumer and environmental demands.

This study aims to evaluate the potential of ultrasonic non-thermal drying, particularly multi-frequency, multimode, modulated (MMM) ultrasonic technology, as a sustainable alternative to traditional drying methods for various heat-sensitive plant-based materials and ingredients.

Ultrasonic contact drying was applied to materials including egg whites, pea protein, distillers dried grains (DDG), vitamin E-loaded emulsions, and cellulose nanocrystals (CNCs). The drying was conducted at low temperatures (around 30°C), using a 20 kHz ultrasonic module with pulsed operation (5s on, 2s off), and compared against conventional hot air drying (HAD), spray drying (SD), and freeze drying (FD). Drying performance, structural and functional properties, oxidative stability, and digestibility were assessed through drying curves, spectroscopy (CD, FTIR, XRD), and in-vitro testing.

Ultrasound drying significantly reduced drying time and energy usage while preserving or improving product quality. For example, ultrasonic drying of pea protein enhanced functional properties such as solubility, emulsification, and gel strength due to increased random coil content. Vitamin E emulsions showed higher encapsulation efficiency, oxidative stability, and bioaccessibility compared to SD and HAD. CNCs dried with MMM ultrasonic methods retained better redispersion and morphology, overcoming typical nano-structure degradation observed in thermal drying. This method also resulted in lower CO2 emissions and reduced specific energy consumption compared to spray drying (SD), hot air drying (HAD), and freeze drying (FD).

Ultrasonic non-thermal drying demonstrates strong potential as an electrification-compatible, environmentally friendly technology. It enables energy-efficient processing of delicate plant-based ingredients while preserving functionality and structural integrity, supporting sustainable innovation in food and bio-based material industries.

Ragya Kapoor

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