In a groundbreaking development poised to transform the landscape of food preservation, researchers have introduced a novel method for dehydrating fruit that bypasses traditional heat-based drying techniques. Published recently in ACS Food Science & Technology, this innovative approach leverages room-temperature conditions in combination with calcium chloride and controlled atmospheric pressure to effectively remove moisture from fruit slices, specifically mango and apple, without compromising their quality or color. This technique promises not only enhanced energy efficiency but also potential applications in sustainable food processing industries worldwide.
Conventionally, the dehydration of fruits relies heavily on thermal energy. Both household and industrial dehydrators utilize heated air circulation to evaporate moisture from food products. While effective, this method demands significant energy input and can alter the taste, texture, and appearance of the dried fruit. Solar drying, an alternative low-energy method, is hindered by slow processing times and undesirable darkening effects on the final product. Addressing these limitations, the research led by Luis Bastarrachea proposes an ambient-temperature system that capitalizes on physical and chemical principles to harvest water from fruit under vacuum conditions.
At the core of this process is the inclusion of calcium chloride, a desiccant well-known for its high affinity for moisture, commonly used in food industries such as cheese production and molecular gastronomy. In the designed dehydration chamber, three distinct wire mesh screens are arranged vertically above a reservoir containing a saturated calcium chloride solution. Fruit slices are placed upon these screens, exposing them to an environment where moisture drawn out from the fruit is immediately absorbed by the salt solution below.
Two experimental conditions were assessed: drying under standard atmospheric pressure and drying under controlled vacuum levels. Over the course of four days, the researchers meticulously monitored moisture levels within different fruit samples at varied positions in the chamber. Under atmospheric pressure, moisture removal proved inconsistent, with slices positioned higher retaining significantly more water—up to 70% by weight—compared to the drier slices at the bottom, which contained about 20-30% water. This inconsistency poses challenges for commercial application, where uniformity of moisture content directly correlates with product quality and shelf life.
In stark contrast, the vacuum-assisted drying environment yielded remarkable consistency. Mango and apple slices subjected to reduced pressure conditions achieved approximately 30% residual moisture, aligning closely with industry standards for dried fruit products. Significantly, this method accomplished the removal of about 95% of the fruit’s original water content without exposure to damaging heat, highlighting the method’s efficiency. The vacuum promotes water evaporation by lowering the ambient pressure, effectively reducing the energy barrier for moisture transition from the fruit surface to the surrounding medium.
Color retention is a critical factor in consumer acceptance. The vacuum-dried mango slices maintained their vibrant yellow hue reminiscent of fresh fruit, enhancing visual appeal. Apples, however, exhibited comparable darkening under both drying protocols, suggesting factors beyond dehydration conditions may influence enzymatic browning in certain fruits. Nonetheless, the overall preservation of color in mango is a promising indicator of the method’s gentle impact on fruit biochemistry.
To investigate microscale changes, scanning electron microscopy (SEM) was employed to analyze the structural integrity of the dried fruit tissues. The images revealed degradation of starch granules in all samples, demonstrating biochemical changes induced by dehydration. However, vacuum-treated samples showed fewer granules affected compared to those dried at atmospheric pressure. This observation implies that vacuum conditions may retard deterioration pathways, preserving cellular structures key to texture and freshness perception.
Beyond the dehydration outcomes, the process exhibits intriguing potential for resource recycling and sustainability. The calcium chloride solution absorbs water released from fruit but can subsequently undergo evaporation itself to reclaim the extracted water, allowing the salt solution to be reconcentrated and reused in ongoing dehydration cycles. This closed-loop approach significantly enhances the environmental footprint compared to conventional single-use drying methods.
Moreover, the reclaimed water could serve diverse secondary purposes. With further treatment, this moisture may be purified for human consumption or industrial applications such as cleaning or chemical processes, presenting a valuable byproduct of fruit dehydration that is often overlooked in conventional systems. The integration of such resource recovery mechanisms aligns with current global imperatives towards zero-waste and circular economy principles.
The implications of this research extend into various domains of food science and technology. Implementing non-thermal drying methods that retain nutritional quality, sensory attributes, and aesthetic appeal can revolutionize snack production and ingredient supply chains. Particularly in regions with limited access to reliable energy sources, such technologies empower local producers to create shelf-stable products without prohibitive energy costs or infrastructure demands.
While the study primarily focused on mango and apple slices, the researchers envision adapting the technology to a broader spectrum of perishable foods, including vegetables and herbs. The system’s modular design permits scaling and customization based on specific product requirements and processing volumes, underscoring its versatility for commercial exploitation.
Future research directions will likely explore optimization of vacuum parameters, calcium chloride concentrations, and drying times to further refine efficiency and product quality. Additionally, comprehensive sensory evaluations and shelf-life testing are essential to fully characterize consumer acceptability and market viability. Investigations into the biochemical pathways impacted by non-thermal dehydration may also unveil new avenues for preserving phytochemicals and antioxidants in dried foods.
This innovative dehydration method represents a harmonious blend of chemistry and engineering designed to meet the contemporary challenges of food preservation. It exemplifies how fundamental scientific insights can unlock sustainable solutions with tangible societal benefits, promoting food security, waste reduction, and environmental stewardship.
As the global demand for minimally processed, high-quality dried foods grows, such advances offer compelling alternatives to energy-intensive drying operations. By harnessing atmospheric water harvesting under vacuum combined with moisture-absorbing salts, this technique paves the way for more eco-friendly, cost-effective, and consumer-friendly food preservation approaches for the future.
Subject of Research: Dehydration of fruit using atmospheric water harvesting under vacuum conditions combined with calcium chloride as a moisture adsorbent.
Article Title: “Dehydration of Mango and Apple through Atmospheric Water Harvesting under Vacuum”
News Publication Date: 15-Jul-2025
Web References:
https://pubs.acs.org/doi/10.1021/acsfoodscitech.2c00433
http://dx.doi.org/10.1021/acsfoodscitech.5c00534
Image Credits: Luis Bastarrachea
Keywords
Chemistry, Food science
