Effects of High CO2 Concentration on Browning Injury and Phenolic Metabolism in Loquat Fruits.

The effects of high CO2 and/or low O2 on browning and phenolic metabolism of loquat (cv. Mogi) fruits were determined. During a 5-day CA storage in 12% CO2 with either air or 2% O2, internal browning and brown surface spotting developed in loquat. The symptoms increased with extended storage. Chlorogenic, neochlorogenic and 5-feruloylquinic acid contents increased to a peak 5 days after the onset of CA storage, it took caffeic acid 10 days to reach its peak. The activities of phenylalanine ammonia-lyase (PAL), 4-coumarate : CoA ligase (CL), and hydroxycinnamoyl CoA : quinate hydroxycinnamoyl transferase (CQT) had a transitory rise to a maximum in 5 days before they rapidly decreased to very low levels. No injury symptoms were found in loquat fruits during the first 5 days of storage in air or 2% O2 CA conditions. The levels of phenolic compounds decreased constantly throughout 20 days and there were little or no changes at all in PAL, CL, and CQT activity levels. The high CO2 may initially induce the activities of PAL, CL, and CQT and cause an accumulation of phenolic compounds. The high activity of CQT caused the degradation of chlorogenic acid which led to its end product, caffeic acid, to accumulate.