Łukasz Łuczaj, Artur Adamczak, Magdalena Duda
Tannin content in acorns (Quercus spp.) from Poland
Dendrobiology 2014, vol. 72: 103-111
Abstract: Oak acorns used to be an important human food, up until recent times. The major factor inhibiting their use in modern nutrition is their high tannin content. Polish oak trees were screened in order to find out whether there are any major geographical or interspecific differences in tannin and total phenolic contents in acorns, which might help us to establish further directions in the search for low-tannin individuals. We studied the level of phenolic compounds using the standard Polish and European Pharmacopoeia method, with Folin-Ciocalteu reagent and hide powder. Altogether 49 acorn samples of Quercus robur, 13 of Q. petraea, 1 of Q. pubescens (all native) and 12 of Q. rubra (introduced) were collected in different regions of Poland. The amount of investigated phenolics in Q. robur and Q. petraea acorns was similar, and tannins constituted the main component. The Q. pubescens sample was distinguished by the lowest tannin and total phenolic content and a relatively high amount of non-tannin phenolics. Q. rubra had a slightly lower tannin content than Q. robur and Q. petraea acorns, but the level of other phenolics was much higher. The results for Q. robur suggest geographical variability of phenolic content as well as a relationship between the phytochemical and biometric parameters of oak acorns.
Additional key words: polyphenols, oak acorns, phytochemistry, food security