Sunday, September 08, 2019

Freeze dried blueberries

Freeze drying—technically known as lyophilisation, or cryodesiccation is a dehydration process typically used to preserve a perishable material or make the material more convenient for transport. A freeze dried fruit is a dehydrated fruit derived from lyophilisation which can be stored for longer duration and can be consumed throughout the year.

Process of freeze drying is practically done in three main phases:
• Freezing, or sub-cooling of product below its eutectic point (cca. -30°C and lower);
• Dehydration (drying) by ice sublimation under vacuum; and
• Completion of product drying up to moisture content lower than 3% by the normal vacuum drying.

Traditionally, freeze-drying is performed at vacuum (vacuum freeze-drying, VFD), resulting in extensive drying periods with high operating costs. In order to shorten this period, alternative processes can be used, such as atmospheric freeze-drying (AFD), where the primary drying stage (sublimation) occurs at atmospheric pressure. AFD has been used successfully for drying of berries. Traditional freeze drying (lyophilisation) is used to quick freeze and vacuum moisture from a blueberry. This gets the blueberry to a 2 % moisture level where it is crunchy.

The freeze dry blueberry maintains all of the nutrients of the blueberry minus the water and an intense blueberry flavor. According to one study, freeze drying resulted in a higher retention of total polyphenols and anthocyanins as well as higher antioxidant activity in the glycoside forms. (International Journal of Food Engineering, Volume 4, Issue 6 July 2008)
Freeze dried blueberries

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