Chemical Features of Phenolic Extracts Prepared on an Industrial Scale from a Processing Byproduct of the Japanese Apricot, Mume Fruit (<i>Prunus mume</i> Sieb.et Zucc.)

Mume fruit, Japanese apricots (Prunus mume Sieb. et Zucc.), have traditionally been used for pickles, juice, and liqueur in Japan. During the pickling of mume fruit, an exudate fluid from the fruit called umesu (or umezu) is produced as a byproduct. We developed laboratory-scale and factory-scale methods using synthetic absorbents HP-20 column chromatography to prepare phenolic fractions from umesu (umesu phenolics or umezu phenolics, hereafter referred to as UPs). In this study, we obtained six batches of UPs using a factory-scale method, and their chemical features were examined. The phenolic contents were 13.1±0.8% and 19.2±2.1%, respectively, with gallic acid and p-coumaric acid as standards. The total sugar content was 57.7±4.7%. Very close similarity was observed in the high-performance liquid chromatograms and compositions of the phenolics in the six batches of UPs. The four major phenolic compounds found in the alkaline hydrolysate of UPs were caffeic acid, cis-p-coumaric acid, trans-p-coumaric acid, and ferulic acid. Some batches showed high amounts of cis-p-coumaric acid / total p-coumaric acid. Since this isomerization did not occur during the UP preparation process, it seems likely that isomerization of trans-p-coumaric acid into cis-p-coumaric acid occurred due to sunlight irradiation during umesu storage.