The role of pre-treatment in freeze-dried herbs processing

15 June 2023

Freeze drying has emerged as a game-changing preservation method that meets the expectations of the culinary world. However, the journey from freshly harvested herbs to freeze-dried perfection involves a crucial step known as pre-treatment.

Often underestimated, pre-treatment sets the foundation for successful freeze-drying by addressing factors such as phytochemical preservation, microbial control, and enzymatic activity.

In this informative blog, we will unravel the significance of pre-treatment in freeze-dried herb processing, exploring the steps involved and the impact they have on the final product. Get ready to delve into the fascinating world of pre-treatment and discover the secrets behind the exceptional quality of freeze-dried herbs.

Why Pre-Treatment Matters?

Pre-treatment serves several important purposes in freeze-dried herb processing.

  • Microbial Load Reduction: Herbs are often exposed to various microorganisms during cultivation and harvesting. Pre-treatment steps like washing and sanitization aid in reducing the microbial load on the herbs. This ensures that the final freeze-dried product remains safe and free from harmful bacteria or fungi.
  • Enzyme Inactivation: Some herbs contain enzymes that can cause degradation and discoloration during the drying process. Pre-treatment methods such as blanching or enzymatic inactivation help in deactivating these enzymes, preserving the color, texture, and overall quality of the herbs.

Steps Involved in Pre-Treatment

Let’s next explore the steps involved in the pre-treatment process.

Sorting and Washing

During sorting, herbs are carefully examined to remove any damaged, bruised, or diseased parts. This ensures that only the highest quality herbs proceed to the next stages. After sorting, the herbs undergo thorough washing to eliminate dirt, dust, and pesticide residues.

Proper washing is crucial as it removes external contaminants and ensures the herbs are clean and safe for consumption. This step also helps to enhance the overall quality and appearance of the final freeze-dried product, setting the stage for subsequent processing steps.


Sanitize the herbs using appropriate methods such as soaking them in a food-grade sanitizing solution. This step helps eliminate surface bacteria, molds, and yeast, reducing the risk of microbial growth during the freeze-drying process.


Blanching involves briefly immersing the herbs in boiling water or steam. It helps in enzyme inactivation and reduces microbial load, ensuring the preservation of color, texture, and nutritional value. The blanching time and temperature vary depending on the herb type and its characteristics.

Slicing or Chopping

This step serves multiple purposes. Firstly, it facilitates faster drying during the freeze-drying process, as the smaller pieces have a larger surface area exposed to the drying environment. Additionally, slicing or chopping enhances the rehydration properties of the freeze-dried herbs, allowing them to absorb water more efficiently when reconstituted.

Enzymatic Inactivation (Optional)

Some herbs may require enzymatic inactivation before freeze-drying. Enzymatic inactivation can be achieved by applying heat or using specific enzyme inhibitors, preventing unwanted reactions during drying.

Pre-treatment plays a crucial role in the freeze-drying process of herbs. It helps preserve the phytochemicals, reduces microbial load, and deactivates enzymes, ensuring high-quality freeze-dried herbs with enhanced flavor, aroma, and nutritional value.

The steps involved in pre-treatment, such as sorting, washing, sanitization, blanching, slicing, and enzymatic inactivation, contribute to the overall success of freeze-dried herb processing. By implementing proper pre-treatment techniques, we can achieve optimal results and deliver herbs that are both visually appealing and packed with their natural goodness.

Contact Flex Foods for the best quality freeze-dried herb, freeze dried mushroom, freeze-dried kale, freeze-dried sweet corn, etc.

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