Drying Techniques and Moisture Management in Food Preservation

Drying is among the oldest and most widely used methods for extending the shelf life of food by reducing water activity and inhibiting microbial growth. Traditional approaches include sun‐ and hot‐air drying, which rely on convective heat transfer to remove moisture but often compromise nutritional and sensory quality when conducted at high temperatures. Freeze‐drying (lyophilisation) preserves structure and bioactive compounds through sublimation under low pressure and temperature, although at high energy and capital cost. Vacuum–microwave drying applies electromagnetic energy in a reduced‐pressure environment to accelerate internal heating and moisture transport, yielding faster kinetics and improved retention of colour and antioxidants. Osmotic dehydration utilises hypertonic solutions to extract water by diffusion without phase change, lowering energy demand and enabling infusion of solutes that enhance flavour or protect against oxidation. Emerging technologies such as electrohydrodynamic (EHD) drying, high‐pressure and ultrasound‐assisted drying, and pulsed‐electric‐field pretreatments aim to optimise energy efficiency, reduce drying times and preserve quality attributes. Moisture management is underpinned by an understanding of water–solid interactions characterised by moisture sorption isotherms and moisture diffusivity, which guide process control and storage stability. Hybrid and intermittent protocols that combine two or more techniques are increasingly explored to balance throughput with final product quality. Integration of predictive models for drying kinetics and thermodynamic analyses supports scale‐up, design optimisation and the reduction of environmental footprint. Rigorous control of residual moisture, packaging, and relative humidity is essential to maintain crispness, nutritional value and microbiological safety in dried foods ranging from fruits and vegetables to herbs, spices and protein‐rich materials.

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Drying Techniques and Moisture Management in Food Preservation publication trend

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Technical terms

Osmotic dehydration: A process in which water is removed from food via diffusion into a hypertonic solution without phase change, reducing energy needs and enabling solute infusion.

Electrohydrodynamic (EHD) drying: A low‐temperature drying method using electric fields to generate ionic winds that enhance moisture removal and energy efficiency.

Vacuum–microwave drying: A technique combining reduced pressure and microwave radiation to accelerate internal heating and drying rates while improving quality retention.

Moisture diffusivity: A coefficient representing the rate at which water moves within a food matrix during drying, governed by temperature and matrix structure.

Moisture sorption isotherm: A curve describing equilibrium moisture content as a function of relative humidity and temperature, essential for stability and packaging design.

References

1. Review of osmotic dehydration: Promising technologies for enhancing products’ attributes, opportunities, and challenges for the food industries. Comprehensive Reviews in Food Science and Food Safety (2024).
2. Electrohydrodynamic drying versus conventional drying methods: A comparison of key performance indicators. Energy Conversion and Management (2023).
3. Effect of Convective and Vacuum–Microwave Drying on the Bioactive Compounds, Color, and Antioxidant Capacity of Sour Cherries. Food and Bioprocess Technology (2013).
4. Freeze-Drying of Plant-Based Foods. Foods (2020).
5. Combined Drying of Apple Cubes by Using of Heat Pump, Vacuum-Microwave, and Intermittent Techniques. Food and Bioprocess Technology (2013).
6. Prediction kinetic, energy and exergy of quince under hot air dryer using ANNs and ANFIS. Food Science & Nutrition (2019).