Impact of bee pollen fermentation on the profile and bioaccessibility of phenolic compounds

Bee-pollen is well-known by its nutritional and bioactive value in regard to protein, lipids, vitamins or polyphenols. In traditional medicine, alternative diets and supplementary nutrition, bee pollen has been used for many years due to its nutritional properties and health benefits. Reports indicate that pollen is insufficiently digested when entering the human digestive system due to its exine layer. However pollen has a high nutritional value. In this study, fermentation was done with pollen samples collected from local bee producers of three different cities (Afyon, Izmit, and Sivas) in Turkey to increase its digestibility by the degradation of exine layer. As starter culture Lactococcus lactis subsp. Lactis or commercial bee bread was used for the fermentation experiment. An in-vitro gastrointestinal digestion method was done for commercial bee bread, unfermented and fermented bee pollen samples. Total phenolic content, total flavonoid content and total antioxidant capacity analyses (based on the DPPH, ABTS, CUPRAC and FRAP methods) were performed on the unfermented and fermented, either or not digested pollen samples and commercial bee bread. Successful fermentation result was obtained only in Afyon bee pollen sample because of the high reduction of pH from 4.59 to 3.87-3.82 by the higher activity of LAB. It was seen that the total phenolic and total flavonoid content of unfermented samples decreased due to the fermentation. According to obtained total phenolic content results, decreasing was observed in Afyon fermented bee pollen samples (29%), İzmit fermented bee pollen samples (20%) and Sivas fermented bee pollen samples (50%) on average. In addition to this, according to obtained total flavonoid content results, decreasing was observed in Afyon fermented bee pollen samples (32%), İzmit fermented bee pollen samples (42%) and Sivas fermented bee pollen samples (48%) on average. In addition to this, fermented pollen samples had a significantly higher antioxidant activity compared to their unfermented sample according to the DPPH and CUPRAC methods. Moreover, according to obtained total antioxidant capacity results based on DPPH method, increasing was observed in Afyon fermented bee pollen samples (52%), İzmit fermented bee pollen samples (44%) and Sivas fermented bee pollen samples (210%) on average. In addition to this, According to obtained total antioxidant capacity results based on CUPRAC method, increasing was observed in Afyon fermented bee pollen samples (36%), İzmit fermented bee pollen samples (58%) and Sivas fermented bee pollen samples (26%) on average. Moreover, the effect of fermentation was not observed on the total antioxidant capacity of the bee pollen based on ABTS and FRAP methods. A higher total phenolic content, total flavonoid content and total antioxidant capacity were observed compared to unfermented bee pollen samples in all fermented bee pollen samples in all digestion phases according to digestion experiments results. Obtained bioaccessibility results from intestinal phase showed that fermented pollen samples had a higher phenolic and flavonoid compound bioaccessibility compared to their unfermented samples.