https://orcid.org/0000-0001-8325-5858
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ABSTRACT
Freeze drying has been a very successful technology in the food and pharma industries, particularly owing to the benefits it offers in terms of product quality. It is most recommended for high-value foods and those that contain heat-sensitive ingredients. Over the years, to meet industry requirements, several variants of the freeze-drying technology have been developed, even to meet specific drying applications. The process of freeze-drying is highly energy-intensive and time-consuming. Nevertheless, innovative techniques are available with the potential to produce products at reduced drying times and lower cost, while being environment-friendly and maintaining freeze-dried quality. This review summarizes advances in the application of infrared, microwave, ultrasound, pulsed electric field, and other techniques as pretreatments and/or to assist conventional freeze-drying processes. Freeze drying combined with other techniques can provide more benefits in terms of energy, time, and cost savings. In this review, comparative studies have been presented to describe these aspects. Such techniques to assist the freeze-drying process can be linked well with sustainable food processing strategies, particularly considering a significant reduction in energy requirements.