# Some Aspects of the Modelling of Dried Red Beets Rehydration Process
## 1 Introduction  
Fruits and vegetables belong to the richest sources of bioactive compounds [1]. In the course of these products' consumption, we supply our organism with not only fibers, minerals, vitamins but also petamines, polyphenols or carotenoids. It has been proven that eating habits can lower the risk of such metabolic diseases as diabetes, obesity and also chronic inflammation, arthitic, hypertension, cardiovascular diseases, and cancers [2; 3; 4; 5]. Red beet (_Beta vulgaris_ L ssp. _valgaris_) derives from the region of the Mediterranean sea and belongs to the plant family Chemopodiaceae. It is cultivated in many parts of the world. Red beet is widely grown in Poland. The area under cultivation in 2021 was approximately 7.4 thousand hectares (4.5% of the total area of field vegetables cultivation), and the red beet harvest amounted to 324 thousand tons (about 6.2% of the total harvest of field vegetables) [6]. Red beet is considered one of the ten most potent vegetables with respect to its total phenolic content. Edible roots of red beets contain 4 to 12% sugar, 1.5% protein, 0.1% fat, and 0.8% fiber as well as vitamins such as B (B\({}_{1}\), B\({}_{2}\), B\({}_{3}\), B\({}_{6}\)) and C. Redbeets are also source of calcium, copper, iron, magnesium, phosphorus, potassium, and sodium. They are rich in a water-soluble nitrogenous pigments (betacyanins) giving red beets their reddish-purple hue. These bioactive compounds have an antioxidant capacity and therefore are very good for human health. Betanin represents 75-78% of the betacyanin pigments content [7; 8; 9]. The green leafy part of red beets contains \(\beta\)carotene and more iron than spinach [10]. The roots of red beets can be consumed fresh or after such processes as cooking, drying, the rehydration of dried products or fermentation. Pickled red beets are a traditional food in South America, and they are popular in Australia and New Zealand. Dried beetroots consumed as a chips can be rich in trans fatty acids and act as a counterbalance for traditional snacks. They are also a component of instant food. The juice from red beets (the composition of which is similar to raw ones) is a recommended healthy drink [11; 12]. Beetroot power produced via belt/tray or spray drying or extracted pigments are industrially applicated as a natural red colorant in jellies, yoghurts, sweets, jams, breakfast cereals, dry mixes as soups or Indian curry mixes [13; 14]. Red beets have medical uses because they are rich source of betamines. These pigments are reported to be antioxidants, compounds that delay the process of oxidation. Therefore, regularly consuming beetroots can protect against cardiovascular diseases, oxidative stress-related diseases and cancers and improve blood quality and digestion [7; 14; 15]. Red beets, in comparison to almost all other fruits and vegetables, have a short harvest period. Drying enables their longer shelf life by lowering their moisture content to such a level at which the deterioration of chemical reactions and microbiological contamination are minimalized to a safe level. Nowadays, the drying of fruits and vegetables is especially important because these dried products are added to ready-to-eat high nutrition meals and are ready supplements in food processing [16; 17]. Because of this, plenty of dried fruits and vegetables have to be rehydrated to return to a state similar to fresh products. The reconstituting ability of dried food products depends, to a high degree, on their internal structure. The kinetics of rehydration and the worsening of quality characteristics of rehydrated product depend on the structural changes caused by predrying treatments, drying, and rehydration [18; 19]. The drying and rehydration of red beets have not been investigated widely and not much data, especially about their rehydration, can be found in the literature. [PERSON] et al. [20] studied the effects of pulsed electric fields (200-600 V/cm) and temperature (30-90 \({}^{\circ}\)C) on the convective drying of red beets.