Sustainable drying technologies

Sustainability issues are omnipresent in all what we do in the current societal proactive domain.^[1,2] This collective effort is linked directly to the nexus of food, energy, and environment. A framework outlining this three-pillar nexus has been proposed focusing on achieving climate protection and ensuring equitable access to food, water, and energy worldwide, while promoting the sustainable growth of a green economy in an increasingly urbanized world.^[3–5] In terms of population dynamics, we expect earth to be inhabited by over 9.5 billion persons by 2050. To meet societal needs for survival, we must double our agricultural production. You can imagine that there will be increasing demands for natural resources such as water, energy, etc. Also, anthropogenic impact on the environment is a growing concern. Our society is mindful of their quality of life and health, especially under the present threat of COVID-19. Today, the boundaries between disciplines are blurring in the quest for knowledge to address these concerns. It is thus no surprise that a multi-disciplinary framework is becoming the norm for research platforms. This is true of pundits of “Drying” who are fostering innovations to be of service to society for creating food, medicine, household or industrial products. Future generations will require this broad approach in all the work they do.

Over the course of our history, we have sought innovation for processes we use every day to achieve better quality products. A good example of this is thermal treatments used to preserve foods for longer periods of time, and which have contributed to the survival and progress of our species. Modern drying has developed since the 20^th century, when natural drying using the sun as a heat source was replaced by mechanical drying. Since the 1950s, the drying process has become better understood and consequently thermal treatments have evolved and are more efficient. Thermal treatments have made it possible to preserve and handle food, facilitate transport and reduce storage costs. Furthermore, these have been used to transform the characteristics of the food to obtain new textures, flavors, and new products. The transformation that food components undergo when heated or processed can dramatically affect the allergenicity of the food products, either by reducing it or increasing it. Thus, greater demands have been placed on thermal processes to be applied on products.

Research has been carried out on the hybridization of different drying processes and emphasis has been placed on mathematical modeling and simulations of drying processes to have tools for optimization. Nowadays, with recent development of software and machine learning platform, a window of opportunity has opened for the analysis and optimization of different coupled technologies to maximize the benefits in drying and other thermal treatments. Furthermore, the simulation and modeling of the drying process can also be used to determine the quality of the product.^[6–8] Several kinetic models of drying processes in different technologies have been proposed^[9,10] to evaluate the effective diffusivity during drying. The higher the effective diffusivity value, the better the kinetics of the drying process. As one of the best drying kinetics are achieved via the use of microwave technology, the scientific community has focused on the exploration, optimization, and modeling of heating and drying using microwave processing technologies. Different approaches have been taken to study and use microwave technology in different applications in engineering, food industry, and nutritional/health sector. The implications of the technology on the environment, economy, and society has also been examined.

Recently, the scientific community has become interested in the modification of allergenic proteins (epitopes) by external stresses, e.g., high temperatures, high pressures, microwave heating, pulsed-electric field.^[11] Microwave heating is a dielectric treatment, which has greater potential to modify the behavior and structure of proteins, since these have a high dielectric constant.^[12] However, the impact of microwaves on allergenic proteins remains controversial. The reason for this is that while the denaturation and unfolding of the allergenic proteins have been shown to be greater with microwave heating than with conventional heating at the same temperature,^[13] microwave heat treatment does not completely modify the antigenicity of the proteins. Thus, the combination of microwave treatment with other processes such as enzymatic hydrolysis or pH reduction has been studied to make this processing more effective.^[14] Moreover, simulation techniques have been adapted to visually evaluate the structural and dynamic processes of protein changes under external stress at the molecular level.^[15] Molecular dynamic modeling has been used to observe structural changes in peanut, soybean and some other fruit allergens under external stress to provide a visual prediction of structural changes in allergens, and then to identify appropriate treatment strategies.^[16,17] This microwave technology application is highly interesting and promising, since the population has developed greater allergies to different types of food. In just ten years from 1997 to 2007, there was an 18% increase in food allergies in children.^[18] Overall, about 10% of the world's population suffers from some form of food allergy.^[19] This problem has been mainly reflected in children, where it presents a series of allergenic reactions that range from mild to severe anaphylactic reactions that is life-threatening without immediate treatment. The reaction includes lowering of blood pressure, increased heart rate, and loss of consciousness. Therefore, allergies are a major problem related to both food safety and human health.

It is evident that, nowadays, the importance of thermal processes and their numerous applications are key for our society that demands better and new food products in the market that do not entail problems of allergies. The scientific community's efforts have also been directed toward developing thermal processes that can be adapted to the existing infrastructure and that do not represent higher production costs. Consequently, microwave technology, together with modeling and simulation processes are the key to technological development in drying and thermal processing in the food and health/nutrition sectors.

Vijaya Raghavan
Department of Bioresource Engineering, McGill University
President (2017-19), Academy of Science, Royal Society of Canada
President (2015), Canadian Society for Biological Engineering
[email protected]