Bioavailability enhancement of Secoisolariciresinol diglycoside (SDG) in flaxseed milk through seed treatment and probiotication

Abstract

Multiple studies have demonstrated the health benefits of flaxseed products containing bioactive compounds such as SDG. It was claimed that grinding, soaking, or roasting seeds might enhance the bioavailability of active compounds. On the other hand, cereal fermentation may increase this bioavailability. This study aims to enhance the bioavailability of SDG in flaxseed milk.

Flaxseeds were reconstituted in distilled water at 5% (W/V) for 15 minutes. The mixture was filtered to produce flaxseed milk (the control). The flaxseed milk was autoclaved before being cultured with L. casei or B. bifidum. The treatment of the flaxseeds before milk preparation was carried out as follows: soaking at room temperature or in boiled water for 4 hours and roasting at 120 or 150 ^o C for 30 min. The changes in SDG in the control, treated and uncultured, and cultured flaxseed milk were monitored using HPLC. Furthermore, the cultured flaxseed milk was subjected to sensory evaluation.

The results showed that the flaxseed milk (5% w/v) contained 220 and 18.9 mg/ml of carbohydrates and protein, respectively. Probiotics were able to grow on the milk, with the best cell count being achieved after 25 h of incubation, reaching log 7 and log 7.23 for B. bifidum and L. casei, respectively. Several peaks in the chromatograph produced by B. bifidum were greater than those produced by L. casei. However, neither probiotics changed the percentage of SDG significantly. When B. bifidum was introduced to roasted whole flaxseeds, several HPLC peaks were generated, which may have been induced by the high temperature or bacterial activity. Additionally, SDG or its metabolites were slightly elevated. The best conditions that favored the production of SDG were soaking whole seeds for 4 h at room temperature and then culturing the milk with L. casei.

This study emphasised the significance of combining physical treatment and fermentation for flaxseeds to achieve higher levels of active compounds.