บทคัดย่องานวิจัย

หมวดหมู่ : ฐานข้อมูลงานวิจัย

Wound-induced phenylalanine ammonia lyase activity: factors affecting its induction and correlation with the quality of minimally processed lettuces

Gloria Lopez-Galvez, Mikal Saltveit and Marita Cantwell

Postharvest Biology and Technology Vol: 9 Issue: 2 Pages: 223-233.

1996

บทคัดย่อ

Wound-induced phenylalanine ammonia lyase activity: factors affecting its induction and correlation with the quality of minimally processed lettuces

One of the major causes of quality loss in minimally processed lettuce (Lactuca sativa L.) is the browning of the cut pieces. Phenylalanine ammonia lyase (PAL, EC 4.3.1.5) is a key enzyme in phenolic synthesis. PAL activity increased in lettuce midrib tissue with wounding and storage in the presence or absence of ethylene. PAL activity increased 2.5- and 3-fold at 5 and 15°C, respectively, by reducing midrib size from 2.5 × 15 to 0.5 × 1 cm. Wounding usually induced maximum levels of enzyme activity within 3 days at 5°C and 1 day at 15°C. Pre- and postharvest factors affected the kinetics of wound-induced PAL (WI-PAL) activity and of subsequent changes in the quality of minimally processed lettuce. The rate at which WI-PAL activity increased and the maximum level attained were influenced by the duration of storage before processing. These parameters were also affected by the cultivar and type of lettuce used. Butterhead and iceberg types had the highest and lowest levels, respectively, of WI-PAL activity; romaine, green leaf and red leaf had intermediate levels. The activity of PAL 1-2 days after processing, and the slope of the induction curve between days 0 and 2, were the enzyme measurements that gave the highest correlations with processed lettuce quality attributes, including overall visual quality, leaf edge browning, and leaf surface browning.