Stability and Bioaccessibility of Lignans in Food Products

Lignans are a group of plant phenolic compounds with various technofunctional and health-promoting
properties. They can be found in oilseeds (291.7-2513 mg/100 g), nuts, vegetables, fruits, and alcoholic
and nonalcoholic drinks. The most common structural representative feature of lignans' backbone is a
dimeric phenylpropanoid, which consists of two C 6 -C 3  units joined by a central carbon. Compared to
other phenolics, such as flavonoids, the literature on lignan stability and bioaccessibility is limited. This
Mini-Review aims to present an overview of recent literature, draw connecting lines to the known
regarding polyphenols, and suggest the main knowledge gaps. Processing methods and processing
conditions influence the stability of lignans with several thermal treatments explored. Roasting, as a
major studied processing step, displayed varying effects as a function of the lignan structure and matrix.
The content of specific and even total lignans was shown to increase in some cases even after intense
thermal treatment. Lignans were also reported to present a stabilizing effect against oxidation to oils
when added externally. Different fermentation methods presented inconclusive outcomes on the
content of lignans, likely stemming from the various matrices and microorganisms studied in a relatively
limited pool of studies. The bioaccessibility of lignans in in vitro studies was usually low (from less than
1% in fermented flaxseed to 30% for microwaved artichokes). Yet, a clear conclusion regarding the
digestive fate of lignans as a function of processing and structure cannot be currently suggested, and
significant additional effort in this direction is needed.