# Physicochemical and Molecular Properties of Spelt and Wheat Starches Illuminated with UV Light
## 1 Introduction  
Starches and their products often have to be modified to improve their essential performance characteristics for many industries. Currently, enzymatic and chemical methods are primarily used to obtain starch degradation products on an industrial scale. To date, the physical modification of starch has taken place on a much smaller scale. Physical methods are environmentally friendly, lead to the creation of unique products, and do not generate unwanted by-products. One method of physically modifying starch is exposure to ultraviolet (UV) light. UV-illumination may be recognized as a green and accessible method for the modification of starch-based films [1].  
Exposure to UV radiation leads to oxidative depolymerization, especially to the cleavage of glycoside bonds [2, 3]. An absorption of UV-C leads to, in particular, the destruction of amylopectin while the amylose chains are attacked by UV-B radiation [4]. Depending on the wavelength and intensity of the radiation, the products may be dextrins, [5, 6] mono- and oligosaccharides [7], or even carbon dioxide and water. If this process takes place in an oxygen atmosphere, it may result in the oxidation of the resulting products [8]. In 1981, authors of [9] suggested that irradiating starch with ultraviolet radiation led to photodegradation, which is associated with C2-C3 bond cleavage in glucopyranose. This creates dialdehyde starch, followed by formaldehyde, formic acid, and carbon dioxide [10], while the cross-linking observed during UV irradiation is due to the formation of highly reactive peroxides on the acetal carbon of the D-glucose unit.  
It is worth knowing that ultraviolet radiation leads to the degradation of D-glucose units in water solutions. Currently, the literature proposes a mechanism by which theultraviolet radiation energy is absorbed by the D-glucose unit (acetal carbon atom chromophore) and consequently leads to a series of photoreactions [9; 10]. The presence of oxygen improves the degradation efficiency of the polysaccharide chains, possibly due to the formation of peroxides at the C-1 carbon. In [3; 11], the research demonstrated that ozone and reactive oxygen species (ROS) such as radicals HO. and HO\({}_{2}\) may be formed under the presence of water, oxygen, and UV light.  
The influence of UV on the molecular structure of the starch polysaccharide chains is less known and described. However, the works [12; 13] concerning the structural transformations of maize and cassava starch bear mentioning. Under aerobic conditions, UV illumination leads to structural changes induced via photodegradation reactions. Prolonged irradiation may provide crosslinking reactions [12; 14].  
Since the molecular structure of the polysaccharide chains of individual starches is different, the influence of UV radiation on the rearrangement of these polysaccharide chains can be varied. Therefore, the aim of this study was to determine the effect of ultraviolet light as an energy source on the molecular structure of spelt and wheat starches and on their selected functional parameters (XRD pattern, maximum absorption wavelength, and susceptibility to enzymatic hydrolysis).