Retention and stability of phenolic compounds in pear (Pyrus communis L.) juices made by novel spiral filter press technology

The retention of phenolic compounds during pear juice production using an innovative spiral filter press and a conventional decanter at pilot scale (150 kg, cv. Schweizer Wasserbirne) was comparatively analyzed. 25 compounds were tentatively assigned by RP-UHPLC-DAD-ESI(-)-QTOF-HR-MS/MS analyses. Caffeoylquinic acid dehydrodimers, detected in pear juices for the first time, may serve as markers of conventionally produced juices. Total phenolic compounds in spiral filter-pressed juices nearly doubled those obtained by decanter (256.2 vs. 136.5 mg/L). This was attributed to the higher retention of 5-O-caffeoylquinic acid (204.1 vs. 67.2 mg/L), which likely underwent oxidation and dimerization during decanter processing. Total flavonol glycosides (17.5 vs. 16.6 mg/L) and β-arbutin (24.8 vs. 30.8 mg/L) levels were unaffected by the processing technology. Over six months of storage, phenolic compounds in both juices were stable, with losses below 5%. Spiral filter-pressed juices were nearly colorless, while decanter-made juices underwent substantial browning during processing and storage.