Application of absorbent resins in protein extraction to reduce off-Flavours in flaxseed proteins

This study investigated the use of adsorbent resins (Amberlite XAD-16 N, Sepabeads SP-207, and Diaion HP-20) during flaxseed protein extraction to reduce the volatile organic (VOCs) and non-volatile compounds (non-VOCs). These compounds could limit the application and consumption of flaxseed proteins by imparting off-aromas and flavours, including bitterness and astringency. The reduction of these compounds using resins during protein extraction could potentially enhance the sensory quality of flaxseed proteins, making them more suitable for incorporation into a wider range of food products such as plant-based meat alternatives, beverages, and protein supplements. Headspace solid phase microextraction- gas chromatography-mass spectrometry (HS-SPME-GC-MS) analysis was performed to examine VOCs in flaxseed meal, untreated flaxseed protein isolate (FPI- control), and resin-treated protein isolates. The flaxseed meal was predominant in hydrocarbons. After extraction, the flavour profile of FPI exhibited aldehydes, ketones, alcohols, and hydrocarbons. Resin treatment indicated that Amberlite XAD-16 N and Diaion HP-20 were more effective at reducing total peak areas for hydrocarbons, aldehydes, alcohols, and acids/esters than Sepabeads SP-207 resin. Analysis of non-VOC using proton nuclear magnetic resonance (¹H NMR) showed that resin treatments decreased the sinapine content twelve times compared to the control and thirty-eight times compared to the flaxseed meal. The phenolic reductions were resin-dependent: Amberlite XAD-16 N achieved the highest reduction for gallic acid, ferulic acid reduction was similar across all resins, while chlorogenic acid reduction was approximately 50 % for all resins used. Additionally, the levels of cyanogenic glucosides were significantly reduced by resin treatment. The functional properties of the resin-treated protein isolates were comparable to the control. Overall, the combination of protein extraction with resin treatment was more effective than the extraction alone at reducing both VOCs and non-VOCs, supporting the use of resins to mitigate flaxseed off-flavours.