大蕉后熟期的褐变相关性及褐变底物鉴定

以粉蕉和香牙蕉为对照,观察大蕉后熟过程中褐变度、多酚氧化酶和过氧化物酶的变化规律,同时考察大蕉总酚和游离酚含量分别在大蕉褐变过程中起的作用。结果表明:三种香蕉在后熟过程中,褐变度均呈逐渐增长趋势,在储藏13d后,粉蕉与香牙蕉的褐变速率明显高于大蕉,说明大蕉更适合于作为深加工的原料。在储藏13d后,大蕉的多酚氧化酶和过氧化物酶比活力均比较低,游离酚含量也比较低,但总酚含量较高,最终导致褐变速率较慢,说明大蕉的褐变度同多酚氧化酶和过氧化物酶有一定的相关性,大蕉的褐变速率与游离酚的含量呈负相关。对褐变度与多酚氧化酶和过氧化物酶进行相关性分析,大蕉后熟过程中的褐变度与多酚氧化酶和过氧化物酶的相关性(R2值)分别为0.8789和0.9240,说明大蕉后熟过程中的褐变潜力与多酚氧化酶和过氧化物酶密切相关;通过紫外-可见吸收光谱扫描和高效液相色谱分析等方法初步鉴定,大蕉的褐变底物主要为没食子酸和表儿茶素。

Correlations between Browning Degree and PPO or POD Activity of Dajiao Banana(Musa paradisiaca ABB cv.Dajiao) and Preliminary Identification of Browning Substrates during Postharvest Ripening

The variation regularity of browning degree(BD),polyphenol oxidase(PPO) and peroxidase(POD) of Dajiao banana(Musa paradisiaca ABB cv.Dajiao) was observed and compared with other two banana varieties,Fenjiao and Cavendish.Meanwhile,the role of total and free phenol contents in the browning of Dajiao banana was investigated.BD indicated a progressively increasing trend in the three varieties of banana during postharvest ripening,and Fenjiao and Cavendish browned significantly faster than Dajian after the 13th day of storage,suggesting that Dajiao was more suitable for deep processing.In addition,Dajiao exhibited low PPO and POD activities and low free phenol content but high total phenol content and consequently browned slowly,demonstrating an association between the BD and PPO or POD activities and a negative correlation between the browning rate and free phenol content of Dajiao.The correlation coefficients between BD and PPO or POD activities were 0.8789 and 0.9240,respectively.Thus,there is a close correlation between the browning potential and PPO or POD activities of Dajiao.The main browning substrates in Dajiao were gallic acid and epicatechin as preliminarily identified using UV-VIS absorption spectroscopy and HPLC.