How drying methods affect nutritional value

 

Drying allows berries, herbs, and mushrooms to be preserved and used far beyond their natural harvest season. While the main goal of drying is moisture removal, the process also influences the nutritional composition of the final product.

Scientific research shows that drying always causes some changes to naturally occurring compounds. However, the extent of these changes depends less on whether an ingredient is dried or not, and more on how it is dried — particularly temperature, drying time, and process control.

This article summarises key research findings on how different drying methods affect the nutritional composition of plant-based ingredients, with a focus on berries, mushrooms, and herbs.

Nutrient sensitivity during drying

Many valuable compounds found in plants are sensitive to external conditions. Heat, oxygen exposure, and prolonged drying times can influence:

• Polyphenols and flavonoids
• Anthocyanins in berries
• Certain vitamins, especially vitamin C

For this reason, drying methods that allow better control over temperature and time tend to preserve nutritional composition more effectively than uncontrolled or prolonged processes.

Berries: Patterns observed in research

Research comparing fresh berries with dried counterparts consistently shows that freeze drying preserves the highest levels of phenolic compounds and anthocyanins. These compounds are particularly sensitive to heat and oxidation.

However, studies also indicate that carefully controlled hot air drying and vacuum-assisted methods can retain a substantial proportion of these compounds, especially when low temperatures and shorter drying times are used. While some losses compared to freeze drying are expected, the differences are often smaller than assumed when drying conditions are optimised.

These findings suggest that for berries, process control plays a critical role in preserving nutritional composition.

Mushrooms: Comparable results across methods

In mushroom studies, freeze drying again shows the highest overall retention of phenolic and flavonoid compounds. That said, research comparing freeze drying, hot air drying, microwave drying, and sun drying demonstrates that the gap between methods is often narrower than expected.
Hot air drying and dehumidified drying methods have been shown to preserve a large proportion of nutritional compounds when temperatures are properly managed. Visual appearance and texture may vary between methods, but nutritional differences are not always dramatic.

Herbs: Temperature and time matter most

Studies on medicinal and culinary herbs highlight the importance of drying parameters rather than the drying method alone. Prolonged drying at lower temperatures can sometimes lead to greater nutrient loss than shorter drying at moderately higher temperatures.

Research indicates that oven or hot air drying at controlled temperatures can preserve herb nutritional composition effectively, while extended drying times — even at lower heat — may result in increased degradation of sensitive compounds

.This reinforces the idea that how long an herb is dried can be just as important as how hot the process is.

Interpreting the research as a whole

Across berries, mushrooms, and herbs, freeze drying consistently achieves the highest preservation of nutritional compounds. However, it is not the only method capable of delivering high-quality results.

Controlled air drying, dehydration, and vacuum-assisted methods can achieve strong outcomes when temperature, airflow, and drying duration are carefully optimised. In many cases, these methods offer a practical balance between nutritional preservation, scalability, and sustainability.

A practical conclusion

Drying inevitably alters food, but it does not automatically mean significant nutritional loss. Scientific research shows that thoughtful process design can preserve much of an ingredient’s natural composition, even outside of freeze-drying techniques.

Understanding these patterns provides a foundation for making informed choices about how dried ingredients are produced — and sets the stage for discussing why certain drying methods are chosen in practice.

In the next article, we explain why Natural Nordic has chosen air drying and gentle dehydration for our powders, balancing nutritional quality, sustainability, and everyday usability.