Different drying methods – a practical overview
By Imre Sólyom, food science graduate (BSc) with a background in food processing and preservation, adapted for Natural NordicDrying is one of the oldest and most widely used methods for preserving food. By removing moisture, drying slows down microbial growth and enzymatic activity, helping berries, herbs, and mushrooms last longer while remaining usable in everyday cooking and food production.
Today, drying is no longer just a traditional practice — it is a carefully controlled process where temperature, airflow, time, and technology all influence the final quality of the product. Different drying methods come with different advantages and limitations, particularly when it comes to nutrient retention, sustainability, scalability, and practicality.
This article provides a brief, practical overview of the most common drying methods used for plant-based ingredients, with a focus on their relevance for berries, herbs, and mushrooms.
1. Sun drying
Sun drying is the oldest and simplest drying method. Ingredients are exposed to direct sunlight and natural airflow, allowing moisture to evaporate over time.
Advantages
Sun drying requires minimal equipment and relies entirely on natural energy, making it one of the most environmentally friendly methods available. It can be suitable for home use or very small-scale production in regions with consistently dry and warm climates.
Limitations
The process is highly weather-dependent and slow, often taking several days under ideal conditions. There is also an increased risk of contamination from dust, insects, and microorganisms, which makes sun drying less suitable for controlled food production in northern climates.
2. Air drying
Air drying uses natural or mechanically assisted airflow to remove moisture from food, usually at ambient or slightly elevated temperatures.
Advantages
Air drying can be carried out indoors, significantly reducing contamination risks. It is particularly well suited for herbs and leafy ingredients, where gentle moisture removal helps preserve structure and aromatic compounds.
Limitations
When relying solely on natural airflow, the process can be slow. Mechanically assisted air drying improves consistency but may increase energy use if not carefully managed.
3. Hot air drying (Dehydration)
Hot air drying, often referred to as dehydration, uses heated air circulated in a controlled environment to remove moisture. This method is widely used in both small-scale and industrial food production.
Advantages
Dehydration systems are relatively simple to operate and highly versatile. Temperature, airflow, and drying time can be adjusted to suit different raw materials. When low temperatures and appropriate drying times are used, a large proportion of the natural compounds in berries, herbs, and mushrooms can be retained.
Limitations
Heat-sensitive compounds, such as vitamin C and certain polyphenols, may degrade if temperatures are too high or drying times are too long. The process also requires energy input, making optimisation an important factor.
4. Freeze drying (Lyophilisation)
Freeze drying involves freezing the food and then removing moisture under vacuum, allowing ice to sublimate directly into vapour.
Advantages
Freeze drying is widely recognised for its ability to preserve flavour, structure, and a high proportion of nutritional compounds. The resulting products are lightweight, shelf-stable, and rehydrate well.
Limitations
The method requires specialised equipment, high energy input, and long processing times. Investment and operating costs are high, which makes freeze drying most suitable for high-value or niche products rather than broad, everyday use.
5. Spray drying
Spray drying transforms liquid foods into powder by spraying them into a hot chamber, where moisture evaporates rapidly.
Advantages
This method is fast and efficient for large-scale production and produces fine, uniform powders.
Limitations
Spray drying is not suitable for whole ingredients and often requires extensive pre-processing. Energy consumption is high, and the method is typically limited to specific product types such as liquids or extracts.
6. Vacuum drying
Vacuum drying removes moisture at reduced pressure, which lowers the boiling point of water and allows drying at lower temperatures.
Advantages
Lower temperatures help protect heat-sensitive compounds and preserve nutritional quality.
Limitations
Vacuum drying systems require significant investment and maintenance. Drying times are longer than with conventional hot air drying, and the method is less practical for bulk processing.
A balanced perspective
Each drying method represents a balance between preservation quality, sustainability, cost, and practicality. While freeze drying often delivers the highest level of nutrient retention, other methods — particularly carefully controlled air drying and dehydration — can achieve strong results when parameters such as temperature and time are optimized.
Understanding these differences helps producers and consumers alike make informed decisions about how dried ingredients are processed and used.
In the next article, we explore how different drying methods affect the nutritional composition of berries, herbs, and mushrooms, based on scientific research.