Freeze-drying duration influences the amino acid and rutin content in honeybee-collected chestnut pollen

Honeybee-collected pollen is gaining attention as functional food for human consumption, due to antiproliferative, antiallergic, antibiotic, antidiarrheic and antioxidant activities. Among the different bioactive compounds, flavonoids from bee-collected pollen are currently recognised as powerful antioxidant and antiradical molecules. Traditional conservation methods influence pollen organoleptic properties as well as the contents of nutrients and nutraceutical compounds. Here, freeze-drying (FD) was proposed as a novel conservation method, estimating its adequacy as drying process by the evaluation of changes in free and total amino acids and proline as well as in their ratios. Honeybee-collected chestnut pollen was taken into consideration and the level of rutin, as main flavonoid, was considered as marker compound highlighting the maintenance of pollen nutraceutical properties. Results showed that FD influenced rutin level, depending on the FD duration. However, the free proline to free amino acid ratio was always below 80%, and the free amino acid to total amino acid ratio remained unaltered indicating the adequacy of the FD treatment, which did not affect the nutritional value of chestnut pollen. Overall, this study shed light on the nutraceutical profile of honeybee-collected chestnut pollen, highlighting the promising potential of FD as a novel method to treat pollen for human consumption.