Effects of different temperature and humidity on bioactive flavonoids and antioxidant activity in Pericarpium Citri Reticulata (Citrus reticulata ‘Chachi’)

Pericarpium Citri Reticulata (PCR, Citrus reticulata 'Chachi') were stored under conditions of high temperature and high humidity (HTHH, 35 °C, 80%) for seven days, then at low temperature and low humidity (LTLH, 20 °C, 50%) for another seven days, and then under alternating HTHH and LTLH for six months. During storage, visual quality (L*, a*, b*, ΔE*) as well as physical (moisture content and water activity) and chemical (antioxidant activity, total flavonoids (TFs), total polyphenols (TPs), and polyphenol profile) parameters were measured. The results showed that, compared to natural ambient conditions, alternating the storage conditions accelerated the browning of PCR, as the values of L* and b* of PCR decreased from 47.62 to 32.44 and from 5.86 to 2.03, respectively. It also enhanced the loss of phenolic substances. The content of TPs, TFs and hesperidin decreased to 65.7 mg GAE/g DW, 57.7 mg CE/g DW, and 42.0, respectively. However, five polymethoxylated flavones (PMFs) and antioxidant activities increased throughout the storage period. Regarding the profile of polyphenols, stressful storage conditions enhanced the phenolic metabolism, suggesting the possibility of accelerating the aging of PCR for possible acceleration of bioactive compound accumulation by regulating the storage conditions to improve the internal chemical reactions.