Freeze-drying strawberries keeps all their Vitamin C and polyphenols and 92% of their antioxidants, saving more nutrients than by chilling.
The study was carried out by Sheffield Hallam University, UK, with frozen fruit firm Chaucer Foods.
The research measured Vitamin C, total antioxidant capacity (TAC), and total phenolic content (TPC) in fresh, chilled and freeze-dried strawberries.
Freeze-drying had no significant impact on nutrient content, but refrigerated fruit experienced large losses.
Packaging research planned
John McAughtrie, technical director, Chaucer Foods, said the research highlights the nutritional benefits of freeze-drying fruit and vegetables.
“We are now planning to undertake further studies to compare the nutrient retention of freeze dried fruit and vegetables against those that have been dried using alternative technologies, and to consider the effects of packaging and storage on nutrient retention.”
In the fruit chilled for seven days, TPC was reduced by 82% from fresh, Vitamin C was down by 19%, and 23% of TAC was lost.
TPC is a measure of polyphenols, chemicals with antioxidant health benefits found in fruits, vegetables, tea and wine. The largest group of polyphenols is flavonoids, which can contribute to food’s color and mouthfeel.
The study also freeze-dried lime, orange, blackcurrant, broccoli and red bell pepper, and found freeze-drying had little or no negative effect on TAC, TPC or Vitamin C content.
Freeze-drying preserves foods using a combination of cold temperature and dehydration.
Fruits and vegetables are frozen, and water is removed from the food by reducing the surrounding pressuring so the frozen water moves straight from solid to vapor.
Chaucer Foods is based in Hull, UK and has freeze-drying facilities in France and China.