Utilizing raw rapeseed press cake in foods: A case study on sensory quality and profile of selected bitter compounds in snack bars

ABSTRACT Today’s canola quality rapeseed press cake (RPC) is a protein-rich co-product with potential as human food, but its application is limited due to antinutritional compounds and bitter taste. It remains, however, unknown how introduction of raw RPC to a food matrix affects sensory perception and which metabolites drive the sensation. Here, raw RPC from whole or dehulled seeds was introduced into snack bars at 0%, 7%, 14%, and 21%, and sensory responses were correlated to selected known RPC-derived bitter compounds. A trained panel evaluated 13 RPC-characteristic sensory attributes, and the bitter compounds sinapic acid, kaempferol 3-O-(2‴-O-sinapoyl-β-sophoroside) (KSS), KSS-hexose, selected bitter glucosinolates, and goitrin were quantified using targeted LC–MS/MS. Most dose-dependent sensory responses increased up to 14% RPC and then plateaued, whereas astringent mouthfeel increased almost linearly across the full dose range. Dehulling intensified several odor- and flavor-related attributes but did not increase bitterness or protein content in the final product. Principal component analysis linked bitterness and astringency positively with KSS, KSS-hexose, and goitrin. Dose-over-threshold analysis further showed that goitrin, but not progoitrin, reached concentrations relevant for bitterness perception. Together, the results demonstrate that raw RPC contributes distinct dose-dependent sensory attributes and that metabolite transformations in the food matrix shape final sensory profiles. These findings provide a basis for developing RPC-containing foods and for breeding rapeseed lines with improved sensory characteristics. HIGHLIGHTS This study presents the first sensory panel assessment of rapeseed press cake (RPC)-containing in food products (snack bars) made from whole and dehulled seeds. 13 RPC-characteristic sensory attributes are identified. Sensory profiles of the tasted snack bars differed significantly, influenced by the dosage of RPC and by the dehulling treatment. Bitterness and astringency are positively correlated with the RPC dosage. Goitrin, kaempferol 3-O-(2‴-O-sinapoyl-β-sophoroside) (KSS) and sinapic acid are RPC-derived bitter compounds that correlate with bitter taste of RPC-containing snack bars. Approximately 90% of glucosinolates introduced with the RPC are not detected in the snack bars, and goitrin levels in snack bars accounts for only ∼10% of introduced progoitrin. Goitrin is – for the first time – reported to contribute to the perceived bitterness of an RPC-containing food product.