Freeze-drying of fruit is a modern drying method in which the phenomenon of sublimation plays the most important role – i.e. the transition of water from ice directly to steam, bypassing the liquid state. First, the fruit is frozen very quickly and then placed in a vacuum chamber. In such conditions the ice evaporates without damaging the delicate structure of the cells. Thanks to this, the fruit retains its shape, color and crunchiness, and at the same time becomes extremely light because it is almost completely free of water.
Chemically, this process is extremely beneficial because: the lack of high temperature and limited access to oxygen slow down dye oxidation or enzymatic browning. As a result, freeze-dried fruits retain much more vitamins, aromas and natural colors than those traditionally dried with hot air. Research conducted by the Faculty of Health Sciences at the Warsaw University of Life Sciences in 2017 shows that even sensitive compounds, i.e. vitamin C and anthocyanins are largely protected against decomposition.
From a biological point of view Freeze-drying effectively stops microbial growth and enzyme activity because microorganisms need water to live. Fruit prepared in this way can be stored for many months without preservatives, and after pouring water, they regain much of their original properties – softness, taste and smell.
Fresh blackberries and freeze-dried ones differ mainly in what happens to the water inside them. During freeze-drying, fruits are first deep-frozen, and then water is removed from them in a vacuum in the sublimation process. This prevents the cells from collapsing, and the delicate structure of the fruit is preserved. The result is a light, crunchy fruit with a porous texture.
Chemically, it is still the same blackberry, but in a more “concentrated” form. Because water previously constituted over 80% of its mass, after its removal, all valuable ingredients – anthocyanins, polyphenols, fiber and minerals – are concentrated. Research by Washington State University (2011) showed that freeze-drying allows you to preserve up to 90% of natural antioxidants, which are decomposed under the influence of high temperature in traditional drying. Only vitamin C, because it is extremely sensitive to oxygen and light, may partially degradeespecially if the fruit was not quickly frozen after harvesting.
Freeze-drying has one more advantage – increases the bioavailability of some compounds. The freezing process gently disrupts cell walls, making anthocyanins and other polyphenols more easily available to the body. Fresh blackberries remain unrivaled in terms of juiciness and smell, but the freeze-dried ones offer a higher concentration of bioactive ingredients in a light, durable form. We can therefore say that freeze-drying does not destroy the nature of the fruit, but “stops it in time”.
They contain anthocyanins, ellagitannins, flavonoids, vitamin C, vitamin K, manganese, dietary fiber and small amounts of folic acid and magnesium. Their deep purple color is the result of the presence of anthocyanins – natural plant pigments that act as strong antioxidants. Research conducted, among others, by the Arkansas Children’s Nutrition Center and Agricultural Research Service showed that blackberry anthocyanins can neutralize free oxygen radicals with similar effectiveness to vitamin Eprotecting cells from oxidative damage that promotes heart disease, neurodegeneration and cancer.
From the point of view of human physiology, regular consumption of blackberries – also in freeze-dried form – supports metabolism, immunity and intestinal health. An experiment conducted by the Finnish Technical Research Center VTT in 2011 showed that in overweight people, including berries in the diet reduced oxidative stress and improved the lipid profile, lowering the level of “bad” LDL cholesterol. In turn, the dietary fiber present in blackberries, especially the soluble fraction, has a prebiotic effect – it supports the development of beneficial intestinal bacteria, which translates into better immunity, more stable blood glucose levels and appetite regulation.
Blackberries are also distinguished by their high content of ellagitannins, which are transformed in the body into urolithins – compounds studied for their anti-inflammatory potential and supporting mitochondrial function. The analysis of the University College of Al-Jamum in 2021 indicated that urolithins can support the regeneration of muscle cells and protect DNA against damage. However, vitamin K also contained in blackberries supports calcium metabolism and bone health.
Sources: Terazgotuje.pl, ResearchGate
