Variation of sunstruck flavor-related substances in malted barley, triticale and spelt

Sunstruck flavor is an off-flavor formed when beer is exposed to light. Although isohumulone is known as the main substrate, the degradation of substances present in malt also plays a role in its formation. Riboflavin, phenylalanine, sulfur-containing amino acids and the sulfur-containing peptide glutathione have been described as sunstruck flavor initiators, promoting the formation of sunstruck flavor (Charpentier and Maujean in Flavour ´81, 3rd Weurman symposium, Munich, 1981; Huvaere et al. in J Agric Food Chem 53(5):1489–1494, 2005; Kuroiwa and Hashimoto in Am Soc Brew Chem 19:28–36, 1961). Moreover, tryptophan and polyphenols are known to reduce the formation of sunstruck character in beer (inhibitors) (Pozdrik et al. in J Agric Food Chem 54(17):6123–6129, 2006). The initiators and inhibitors of sunstruck flavor originate in the raw material used, and their content can be influenced during manufacturing. The aim of this paper was to define the influence of the malting process parameters on the content of initiators and inhibitors involved in the formation of sunstruck flavor in different cereals. Barley, spelt and triticale were malted under different parameters, and the content of the sunstruck flavor initiators and inhibitors was analyzed. The initiator and inhibitor contents were described by linear, two-factor interaction or quadratic models. The malting parameters exert in most of the substances a positive influence. The germination temperature had a negative influence on the content of cysteine, methionine and tryptophan of triticale. The germination time and temperature showed a negative influence on the tryptophan content of spelt. With the knowledge gained, the potential of different cereals for its use in the development of malted cereal-based beverages can be determined. Moreover, the influence of malting process on the content of these substances as well as differences between the raw materials was defined.