Effects of high CO2 concentration on browning injury and phenolic metabolism in loquat fruits

The effects of high CO2 and/or low O-2 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% O-2, internal browning and brown surface spot ting developed in loquat. The symptoms increased with extended storage. Chl orogenic, 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-coum arate:CoA ligase (CL), and hydroxycinnamoyl CoA:quinate hydroxycinnamoyl tr ansferase(CQT) had a transitory rise to a maximum in 5 days before they rap idly decreased to very low levels. No injury symptoms were found in loquat fruits during the first 5 days of s torage in air or 2% O-2 CA conditions. The levels of phenolic compounds dec reased 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 ca use an accumulation of phenolic compounds. The high activity of CQT caused the degradation of chlorogenic acid which led to its end product, caffeic a cid, to accumulate.