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

Todays 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-{beta}-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. HIGHLIGHTSO_LIThis study presents the first sensory panel assessment of rapeseed press cake (RPC)-containing in food products (snack bars) made from whole and dehulled seeds. C_LIO_LI13 RPC-characteristic sensory attributes are identified. C_LIO_LISensory 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. C_LIO_LIGoitrin, kaempferol 3-O-(2'''-O-sinapoyl-{beta}-sophoroside) (KSS) and sinapic acid are RPC-derived bitter compounds that correlate with bitter taste of RPC-containing snack bars. C_LIO_LIApproximately 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. C_LIO_LIGoitrin is - for the first time - reported to contribute to the perceived bitterness of an RPC-containing food product. C_LI