Phenolische Inhaltsstoffe in Eicheln (Früchte von Quercus spp.) sowie im Harn von Schweinen bei Nutzug von Eicheln als Futtermittel

The present dissertation shows an overview of the phenolic compounds of Quercus rubor, Q. petraea and Q. rubra. The reason for this paper is the renaissance of acorn fattening, where pigs are fed with acorns in autumn. After slaughtering and maturation of the meat, the acorn feeding results in a unique flavour of the meat. Consumers are willing to pay a higher price for this meat. In order to ensure this way of feeding in the stable, high standards are required for storing the acorns. Storing can be optimised by processing the acorn raw material. For this reason, untreated acorns as well as thermally dried acorns and acorn silage were investigated. By analysing processed samples of acorn feed new knowledge was gained. The polyphenolic content after thermal drying is very low. Also, the silage production reduces the total phenolic content. In processed samples of acorn feed free phenols were detected that were not detectable in untreated acorns. So it can be concluded that the use of processed acorns will not lead to the same results in the acorn meat products that are achieved by the feeding (in stable or grazing land) untreated acorns. For the first time different ripening phases of acorns were analysed. It was possible to show that the polyphenolic content of unripe acorns is significantly lower than in ripe or overripe acorns. In ripe acorns substances could be detected by HLPC-MS/MS that were not detectable in unripe acorns. For example, valoneic acid dilactone was not detectable in green oak acorns. For analysing the crucial polyphenols, different analytical methods were used and combined with each other. For the analysis by HLPC-UV a Chromolith® Performance RP 18 ec column was used. This made it possible to separate the extractions of the acorn samples and to detect several polyphenols (e.g. chlorogenic acid, gallic acid, ellagic acid) in untreated acorns. These polyphenols can also be detected in unripe and overripe acorns. Therefore, it can be concluded that these polyphenolic substances are entirely persistent during the growth of the acorns and there is no difference, whether the pigs are fed with unripe, ripe or overripe acorns. The high toxicity of unripe acorns cannot be explained clearly by the content of polyphenols. The results of all applied analytical methods (HPLC-UV and –DAD, GC-MS, HPLC-MS/MS) significantly show that the thermal drying of acorns results in the lowest total polyphenolic content and the lowest single polyphenolic content. For this reason the feeding with thermally treated acorns is not sufficient considering the polyphenolic content necessary to produce high-value meat products. The amount of fed acorns needs to be increased significantly in order to feed the same amount of polyphenols. By feeding high amounts of acorns, the acceptance of the pigs for this feed decreases. In the acorn silage free epicatechine and cholorogenic acid were not detectable, but high amounts of ellagic acid were detected. In the untreated acorns, beside gallic acid and ellagic acid, quercetine-galactosid dominated also. These substances are influenced in different ways by thermal treatment and fermentation. A lot of substances are oxidised and/or split during processing. The amount of gallic acid detectable by HPLC drops about 50 % and the contents of quercitine-galactosid and epicatechine decrease as well. On the other hand, the content of ellagic acid in thermally dried acorns increases fourfold, the content of detectable ellagic acid in acorn silage is fivefold higher in comparison with untreated acorns. Therefore, the feeding of acorn silage results in an enhanced supply of especially ellagic acid, chlorogenic acid and caffeic acid. Due to fermentative processes degradation during silaging, other ingredients of untreated acorns are not detectable any more. The total polyphenolic content of acorn silage is comparable with the content of untreated acorns. The present paper also shows that various characteristic metabolites of the polyphenols can be detected in the urine a few hours after the first feeding of acorns. Comparatively low amounts of acorn feed are sufficient. By using the HPLC-MS/MS it was possible to show the dependence of quercetinsulfat, quercetin-3-glucoside, quercetagetin-7-O-glucoside and urolithin A-diglucuronid to the acorn fattening. These investigations are only the basis for the analysis of the metabolism of acorn polyphenols and their influence on animals. Further analyses are absolutely necessary. As a result of this dissertation, it has to be advised to investigate the acorns intended for feeding (differences in acorn variety, ripening and processing) considering their total polyphenolic content or even better their polyphenolic spectra in order to rule out the occurance of intolerances during the fattening period. Further investigation of the acorn ingredients can contribute to the evaluation of tannins and polyphenols in a lot of plants and pieces of them based on several specific substances, considering whether they show beneficial and/or adverse health effects. This knowledge leads to further information that can be transferable to human nutrition and health.