# Dehumidified Air-Assisted Spray-Drying of Cloudy Beetroot Juice at Low Temperature
## 1 Introduction  
Beetroot (_Beta vulgaris_ L.) is a part of the _Chenopadiacene_ family and is considered as one of the ten vegetables with the best antioxidant properties because of its high polyphenol content (50-60 mol/g solids) [1, 2]. Beetroot is mostly recognized for its characteristic color that it owes to betanins, which belong to the group of purple betacyanins. Betacyanins, in turn, belong to the group of betalains, which also include yellow betaxanthins, the most important of which are vulgaxanthins [3, 4]. Betacyanins are susceptible to high temperatures, which suggests that the application of low-temperature or non-thermal methods will result in products with high contents of these dyes. Moreover, during heat treatment, red dyes can turn into yellow dyes and there is also a high probability of Maillard reaction products being produced, which result from a series of chemical reactions that occur most often under the influence of heat between amino acids and reducing sugars. [5].  
In the food industry, betalines are mostly used as a natural dyes; however, their use is limited because of their susceptibility to high temperature and light. Currently, the main source of commercially used betalains dyes is beetroot [6]. Dyes are commonly used in the form of powders and the most popular method to obtain food powders is spray-drying, due to the short, single-step operation that enables the production of powders from liquid feeds. Moreover, this method is suitable for materials that may lose their properties due to high temperatures following brief contact with hot air [7]. However, during spray-drying there is a possibility of stickiness, which may occur when the drying materials are rich in low-molecular-weight sugars (glucose, fructose) because of their low glass transition temperatures (\(T_{g}\)). There are many approaches that make it possible to avoid this phenomenon,but the most common is the addition of carriers of high \(T_{g}\)[8]. However, the growing trend of \"clean labels\" among consumers makes it necessary to seek different approaches. One that is currently gaining more recognition in the literature is the use of dehumidified air as a drying medium. Dehumidified air makes it possible to lower the drying temperature and, as a consequence, prevent the stickiness problem. This method makes it possible to decrease the addition of carriers as well and, at the same time, enhance the product yield and powder properties. [PERSON] et al. (2019) successfully spray-dried rapeseed and honeybee honey at inlet/outlet temperatures of 75/50 \({}^{\circ}\)C with such a dehumidified air-assisted method [9]. It was possible to reduce carrier content to 20% thanks to the use of dehumidified air, while the addition of carriers in most honey powders is about 50%. [PERSON] et al. (2017) spray-dried olive mill wastewater using dehumidified air at an inlet temperature of 110-130 \({}^{\circ}\)C and they observed significantly higher product recovery (87-94%) than with traditional spray-drying (<3%) [10]. Powders obtained using dehumidified air are characterized by lower water content and higher bulk density and their particles have smoother surfaces. Moreover, lowering drying temperatures reduces the risk of degradation of thermolabile compounds, such as betalaines [11]. [PERSON] et al. (2019) obtained honey powder with underierated biological activity through the application of spray-drying with low-humidity air at 75/50 \({}^{\circ}\)C inlet/outlet temperatures [12].  
The aim of the study was to develop 100% powders (without carriers) from cloudy beetroot juice using dehumidified air-assisted spray-drying at low temperatures (inlet air temperature: 90 \({}^{\circ}\)C and 130 \({}^{\circ}\)C). The research included the determination of the powder recovery and of selected physicochemical properties of the obtained powders, which were compared for powders without carriers and those with carriers (maltodextrin, milk powder, nutriose, and kleptose).