sinigrin

Sinigrin is an aliphatic glucosinolate found in Brassicaceae vegetables, with a 2-propenyl (allyl) side chain. It appears widely in Brussels sprouts, cabbage, cauliflower, and kale. In aqueous and lipophilic sensory tests, this compound itself is positioned as a sensory quality distinct from AITC, and sinigrin is perceived primarily as bitter; this serves as the starting point for understanding its role.

In a study tracking taste differences across Brussels sprouts cultivars, the combined content of sinigrin and progoitrin showed a negative correlation with overall consumer preference only in the range exceeding 2.2 g/kg (explaining 64% and 86% in 2 test designs, respectively). Below this threshold, the relationship between combined content and preference disappeared, but the correlation with bitterness itself was maintained across the entire range tested. The level of content does not translate directly into 「嫌われる度合い」 (in translation: "degree of dislike"), demonstrating a practical case in which the sensation of bitterness and the behavior of avoiding it represent separate variables.

The connection between this Brussels sprouts bitterness and sinigrin and progoitrin was already established in a 1983 study—15 years before the 1998 test—which linked the bitterness of that cultivar to the presence of these 2 glucosinolates. Sinigrin itself is bitter, while the bitterness of progoitrin is described as deriving from its degradation product, goitrin. However, both studies remain at the abstract level, and owing to differences in detail (such as consumer panel size) and differences in cultivation year and design between studies, the 2.2 g/kg threshold cannot be determined to be a universal threshold.

In sensory tests comparing thresholds between AITC and sinigrin in aqueous and lipophilic systems, 64 panelists distinguished sinigrin primarily as a bitter sensation and AITC primarily as a pungent sensation (sinigrin aqueous BET value 10.928 mg/100ml). Because both belong to the same glucosinolate-isothiocyanate system yet yield different sensory qualities, distinguishing the bitterness of sinigrin from the pungency of a different compound, allyl isothiocyanate (AITC), is essential to understanding the bitterness of Brassicaceae vegetables.