Changes Of Quality, Physio-Biochemical And Enzymatic Browning Characteristics Of Oenanthe Stolonifera (Cv. Liyang) During Storage

Oenanthe stolonifera (Cv. Liyang) after harvest is very sensitive to weight loss, is easy to loss its tenderness and fresh flavor, and to be brown, and to decay, and then commodity characteristic. This thesis studied the quality, physiology and browning characteristics of Oenanthe stolonifera (Cv. Liyang) after harvest to search optimal storage condition and control browning method. The results were as following:1. The effect of storing temperature on the quality and physio-biochemical characteristics of Oenanthe stolonifera (Cv. Liyang) was investigated. The results showed that 0+1℃was effective enough to prolong the storage life of Oenanthe stolonifera (Cv. Liyang). Compared to 20℃, 0+1℃slowed down weight loss by as high as 7%, reduced respiratory rate as much as 40mgCO₂·kg^-1·hr^-1, decreased the increase of fibre significantly and loss of reducing sugars, and inhibited tissue browning of Oenanthe stolonifera (Cv. Liyang).The total phenol in Oenanthe stolonifera (Cv. Liyang) was 85.33μg/100gFW, and most them was in bound form (free phenol was only 11.6%). The total phenol was decreased slowly, while free phenol changed little in Oenanthe stolonifera (Cv. Liyang) both stored at 0℃and 20℃.Oenanthe stolonifera (Cv. Liyang) was easy to be brown even at 0℃, and had very high activity of PPO and POD. Statistical analysis showed that the browning was related to the PPO and not related to POD.2. The effect of harvesting time on the quality and physiological—biochemical characteristics of Oenanthe stolonifera (Cv. Liyang) was investigated. The results showed that Oenanthe stolonifera (Cv. Liyang) harvested at Dec. 7, 2005 had a significantly slower weight loss (p＜0.05), browned more slowly, and had less contents of fibre (only 1.9mg.g^-1FW) , O₂^- and MDA, and increased more slowly during storage. The respiratory rate of Oenanthe stolonifera (Cv. Liyang) harvested at Dec. 7, 2005 was 32.9 mgCO2.kg^-1.h^-1, smaller than that harvested at other dates, and stabler during storage.3. TLC, ultraviolet scanning and HPLC analyses showed that main phenols in Oenanthe stolonifera (Cv. Liyang) were catechol.4. The characteristics of PPO and POD in Oenanthe stolonifera (Cv. Liyang) was investigated. The result showed that the PPO from Oenanthe stolonifera (Cv. Liyang) shows its greatest activity at 25℃and pH 6.0, and loss its activity easily when temperature was up 80℃with treating 7 minutes, while the enzyme after being treated at 60℃will be insensitive. The combining capability of PPO to different phenol substrate was in the order:chlorogenic acid＞dihydroxycinnamic acid＞gallic acid＞catechol＞pyrogallic acid＞methyl catechol＞epicatechin. The PPO shows the highest activity when combined with chlorogenic acid.The POD of Oenanthe stolonifera (Cv. Liyang) had its greatest activity at pH 5.0 and the second highest at pH 6.4. The optimal temperatures of POD was 40℃. Oenanthe stolonifera (Cv. Liyang) POD had worse heat resistance, lost its activity quickly when temperature above 80℃for 3 minute. The enzyme after treated at 90℃for 50 second would be inactivated completely. The POD of Oenanthe stolonifera (Cv. Liyang) shows its high activity at Low Temperature so enzyme reaction on browning should be noticed. The combining capability of POD to different phenol substrate was in the order: pyrogallic acid＞chlorogenic acid＞dihydroxycinnamic acid＞gallic acid＞hydroxytyramine＞epicatechin＞catechol＞methyl catechol.5. The effect of various inhibitors on PPO and POD of Oenanthe stolonifera (Cv. Liyang) was studied. The results demonstrated that L-Cys had strongest inhibition on the activities of PPO and POD; all Oxalic acid, NaHSO₃, CA and 4—HR were good for inhibiting PPO and POD activity; AA was effective to PPO but not very effective to POD; both CaCl₂ and EDTA-2Na had little effect on PPO and POD.