Metabolic Characteristics Of Phenolic Compounds And Volatiles In Relation To Fruit Quality In Apples

With both reversed-phase high-performance liquid chromatography (HPLC) and thermo-desorption and cold trap (TCT) gas chromatography mass spectrometry (GC-MS), the studies were carried out on the composition of phenolic compounds and volatiles in fruits of 5 apple cultivars (Malus domestica Borkh. cvs. 'Fuji', 'Starkrimson', 'Jonagold', 'Orin' and 'Golden Delicious'). The relationship was revealed between phenolic compounds and fruit flavor, flesh browning and its nutrient value. And the dynamic changes of fruit aroma in different cultivars and pathway pertaining to its biosynthesis were explored as well. The main results were as follows:1. Phenolic compounds concentrations were much higher in young fruit than those in ripe fruit. The low-molecule phenolic compounds in young fruit included chlorogenic acid, (+)catechin and(-)-epicatechin. There were significant differences in three compounds among fruit from defferent cultivars. Young fruit of 'Fuji' were abundant in chlorogenic acid and (-)epicatechin, in (+)catechin of Orin, and in chlorogenic acid and (+)catechin of Golden Delicious. However, there were no significant differences in the three compounds between Starkrimson and Jonagold. Total concentration of the low-molecule phenolic compounds (chlorogenic acid, (+)catechin, (-)epicatechin, phloridzin and quercetin) was the highest in Starkrimson, with procyanidins the highestest in Jonagold and Golden Delicious.The main composition of low-molecule phenolic compounds in ripe 'Fuji' fruit was chlorogenic acid, while it was (-)epicatechin in Starkrimson and Orin. There were significant differences in contents of chlorogenic acrd, (+)catechin and (-)epicatechin between Jonagold and Golden Delicious fruit. Total quantity of low-molecule phenolic compounds and procyanidins were higher in Fuji's and Starkrimson's.ripe fruit.Phenolic compounds accumulated much more in peel, core and seed in fruit. Chlorogenic acid existed mainly in seed, core and flesh, and (+)catechin ,(-)epicatechin and procyanidins in the peel with small amount in the flesh and core, and phloridzin in the seed, peel and core.. However, qercetin was detected only in the peel.2. The fruit flavor was affected by phenolic compounds. Chlorogenic acid, (+)catechin and (-)epicatechin were attributed to astringeney. Phloridzin could result in bitter taste, and (+)catechin in both astringeney and bitter. The concentrations of chlorogenic acid, (+)catechin, (-)epicatechin and procyanidins were much higher in astringeney fruit, while the concentrations of chlorogenic acid, phloridzin and procyanidins ?were much higher in the fruit with strong bitter taste, and theconcentrations of chlorogenic acid, (+)catechin, (-)epicatechin, phloridzin and procyanidins were the highest in the fruit, leading to both astringency and bitter taste,. The levels of phloridzin and procyanidins in the bitter pit tissue on Starkrimson fruit were 15 and 3 times as high as those in normal fruit tissue. Therefore, bitter taste was closely related to an accumulation of phloridzin and procyanidins, but astringency was associated with the increase of chlorogenic acid, (+)catechin, (-)epicatechin and procyanidins in fruit.3. The sensitivity of 'Fuji' apple flesh to browning was the highest, followed by Starkrimson, Jonagold and Orinn, as well as Golden Delicious. With chlorogenic acid as substrate, the PPO activity in Starkrimson fruit was the highest, followed by Fuji and Golden Delicious. With (+)catechin as substrate, the Fuji and Orin fruit had the highest PPO activity, followed by Golden Delicious. With epicatechin as substrate, Orin, Jonagold and Fuji fruits had the highest PPO activity.Fuji, Starkrimson and Golden Delicious fruit had higher PPO activity with chlorogenic acid as substrate than with (+)catechin and (-)epicatechin. Jonagold fruit had higher PPO activity with chlorogenic acid and (-)epicatechin as substrate than with (+)catechin. PPO activity in Orin fruit had no difference by using the 3 substrates.PPO activity varied with different substra...