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Hop Constituents Suppress the Formation of 3-Methylbutanal and 2-Furfural in Wort-Like Model Solutions

​The ability of hop constituents to suppress the formation of 3-methylbutanal and 2-furfural in wort-like model systems containing maltose, leucine, and Fe²⁺ was investigated. From all constituents tested (α-acids, β-acids, iso-α-acids, tetrahydro-iso-α-acids, and spent hops), solely α-acids and β-acids were capable of significantly suppressing the formation of 3 methylbutanal as derived from degradation of leucine. 2-Furfural was also found in the model solutions after incubation, and its formation was diminished by all hop constituents but to a varying degree. A central composite rotatable design was employed, and from all factors tested (maltose, leucine, Fe²⁺, and α-acids), only maltose and leucine were found to be significant model terms (P < 0.05) for the formation of 3-methylbutanal, whereas α-acids also showed effectiveness but at a lower confidence level (α = 0.1063). Maltose and α-acid concentrations were significant model terms for the formation of 2-furfural. Although Fe²⁺ concentration was an insignificant factor for aldehyde formation, complexing it with ethylenediaminetetraacetic acid still inhibited aldehyde formation. When no maltose was present, 3-methylbutanal was also shown to be derived from leucine oxidative degradation by hydroxyl radical attack. Hop α-acids were demonstrated to significantly abate this particular pathway by Fe²⁺ complexation and hydroxyl radical scavenging. Keywords: Hops, Hop α-acids, Iron, Maillard reaction, Carbonyls, Response surface methodology