While freeze-dried fruits and snacks are a common sight on supermarket shelves, the process of freeze-drying also has a range of useful applications within the hospitality sector. This is largely due to it being a preservation process, preventing spoilage of herbs and other food items that might otherwise occur in non-freeze dried foods.
In this article, we’ll introduce the process of freeze-drying, explain how it works and what kinds of items are suitable for this process. Additionally, we’ll also explore how freeze drying can be beneficial for hotel kitchens and other venues wanting to serve delicious meals while saving on both expense and food wastage.
How Does Freeze Drying Work?
Water comprises around 80% to 95% of most raw food products. While these foods generally have to be used within a specific timeframe, using a freeze dryer extends their lifespan. This process (also called lyophilization) uses a to preserve food by freezing items before using pressure to remove water content. This then changes from a solid to a gas (omitting the liquid phase). This typically follows three stages:
- Freezing the food items by way of atmospheric pressure
- Primary or “proper” freeze-drying, which “sublimates” the food item through water extraction
- Secondary (or “desorption”) drying, which removes the remaining bound water.
The water found in food can be referred to as either “bound” or “free” water. While free water can be frozen, bound water typically does not. During the freeze-drying process, all free water is removed, remaining frozen throughout, while some bound water remains.
What to Freeze Dry and When to Use Caution
Many types of food can be freeze-dried, such as:
- Fruits, such as apple, pineapple, mango, cherries, raspberries and blueberries. These work well in deserts or can be used as an additional menu item for venues serving breakfast, for example with yogurt.
- Vegetables including tomatoes, squash and zucchini can all be freeze-dried and used as flavorful additions to soups, stews and other dishes. This process can be especially useful for commonly used “base” ingredients, such as chopped onions.
- Herbs and spices such as parsley, basil. ginger, mint and garlic freeze-dry well, offering a fresher, flavorful alternative to dried options.
- Legumes, like peas, lentils and cooked beans can also be freeze-dried.
Some meat and eggs can also be freeze-dried, although with caution: although the removal of water during freeze-drying lowers microbial growth, microorganisms present in raw egg or meat can remain during the process and throughout storage, potentially leading to foodborne illness, making it essential to cook these before consumption.
In some cases high levels of porosity in freeze-dried foods may also lead to high degradation of bioactive compounds or oxidation, which is why it’s important to recognise not all foods are suitable for freeze-drying, and that food should only ever be freeze-dried by machine).
What Are the Benefits?
Along with helping to extend the shelf life of otherwise perishable foods, freeze-dried foods offer a multitude of health benefits, removing water while retaining flavors, nutrients and bioactivity. Freeze-drying also helps to retain quality in food while helping reduce the likelihood of premature spoilage or bacteria growth.
Additionally, food preservation methods such as freeze-drying help to mitigate the vast amount of food wasted globally each year. Not only can this benefit hospitality business owners who might otherwise lose revenue through food spoilage, but also benefits the environment.
