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 Addresses: Ł. Łuczaj, University of Rzeszów, Institute of Applied Biotechnology and Basic Sciences, Department of Botany, Werynia 502, 36-100 Kolbuszowa, Poland, e-mail: lukasz.luczaj@interia.pl A. Adamczak, Institute of Natural Fibres and Medicinal Plants, Department of Botany, Breeding and Agricultural Technology, Kolejowa 2, 62-064 Plewiska near Poznań, Poland M. Duda, University of Rzeszów, Institute of Applied Biotechnology and Basic Sciences, Department of Botany, Werynia 502, 36-100 Kolbuszowa, Poland

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Tannin content in acorns (Quercus spp.) from Poland

Oaks cover a vast area of Jordanian forests, and their fruit (named acorns) have good nutritional value. In this study, we investigated the physical, chemical, and nutritional characteristics of the acorns produced by three Jordanian oak species, Quercus aegilops (QA), Quercus infectoria (QI), and Quercus calliprinus (QC). The physicochemical (acorn length, weight; cupule weight, coat weight, cotyledon weight, coat weight percent, cotyledon weight percent and acorn volume) and nutritional quality (protein, fat, fiber, ash, carbohydrate, amino acid, fatty acid and mineral compostions) of the acorns from the three oak species were determined using standard procedures. The acorn of QA showed significantly greater values compared to QC for all physical characteristics assessed while QC exhibited the lowest values; QI presented intermediate values.The chemical composition of the three species showed that fat content varied from  8.18% to 8.99% and the crude fiber and the total carbohydrate content ranged from 3.27% to 3.86% and 76.20% to 81.43%,  respectively According to obtained results, oak acorn can be considered a significant source of protein (9.54% for QC to 10.9% for QA). Oak acorncontained 18 known amino acids (AAs); with total essential amino acids (TEAA) levels in these oak species as 2307.9, 1699.1, and 2262.8 mg/100 g dry weight, respectively. The most abundant essential amino acid found varied between species: in QA it was leucine (446 mg/100 g dry weight), in QC it was arginine (526 mg/100 g dry weight), and in QI it was phenylalanine (395 mg/100 g dry weight). The ratio of TEAA to total amino acids (TAA) was 0.90: 0.50 and 0.79 for QA, QC and QI, respectively, which indicates that QA is the best species in terms of essential amino acid (EAA) proportion. The EAA scores showed that (phenylalanine + tyrosine) and (methionine + cysteine) were the most abundant AAs in oak acorns, while lysine and leucine were the most limited. The ratio of unsaturated fatty acids to saturated fatty acids in the acorn oil ranged from 3.45:1.00 to 3.93:1.00. Therefore, oak acorn oil may be considered healthy for a human diet. The most abundant minerals in decreasing order were K, P, Ca, Cl, S, Fe, and Mn. These results demonstrate that oak acorns from Jordan have great potential to be included in human feeding.
Key words: Amino acids, Fatty acids, Nutritional value, Oak acorn, Quercus L

https://ajfand.net/Volume20/No5/Radwan19170.pdf

Physiochemical properties and nutritional profile of Mediterranean oak acorn

SITE CHARACTERISTICS AND REGENERATION STUDIES OF BANI OAK (Quercus glauca THUNBERG) IN HIMACHAL PRADESH

The results of the chemical investigations of variously treated acorn samples are presented in this paper with the aim of obtaining data on the amount of nutritious components and biologically active substances. The Quercus robur acorn, which belongs to the Fagaceae family, was investigated in a raw, thermally treated form and as an extract that was subsequently dried in a dryer with a fluidized bed. The obtained results regarding the content of tannin, nitrogen containing compounds, macro- and microelements indicate that acorn maintains its functional characteristics after the investigated treatments.

http://www.doiserbia.nb.rs/ft.aspx?id=1450-81090502173R

M. Zivkovic

Papers

Drying of the aqueous extract of acorn Quercus robur in a spout-fluid bed