ศูนย์นวัตกรรมเทคโนโลยีหลังการเก็บเกี่ยว

Starch degradation in kiwifruit: in vivo and in vitro ultrastructural studies.

Hallett, I. C., Wegrzyn, T. F. and MacRae, E. A.

International Journal of Plant Sciences Year: 1995 Vol: 156 Issue: 4 Pages: 471-480 Ref: 39 ref.

1995

บทคัดย่อ

Kiwifruits (cv. Hayward) were examined at harvest and during postharvest ripening to quantify structural changes to starch granules as net starch degradation occurred. The changes were compared with those found in in vitro studies utilizing granules prepared from fruits at harvest. In in vitro studies starch granules were incubated with various mixtures of starch-degrading enzymes and examined by scanning and transmission electron microscopy at sequential points during enzyme incubation. Only alpha -amylase, or alpha -amylase in combination with other enzymes, was able to degrade the native granules. A combination of alpha -amylase and alpha -glucosidase resulted in less degradation than alpha -amylase alone. Crude extracts from kiwifruit or pea leaf resulted in minimal degradation under the conditions tested. In all experiments alpha -amylase attack began by creating channels to the centre of the granule, which was then followed by radial degradation from the centre outward. An external shell w

as generally all that remained. This pattern was not detected in vivo. Here degradation appeared to be from the outside in. Often individual granules within a plastid appeared to resist degradation when adjacent ones were being hydrolysed. Measurements of granule diameter, both in vivo and with extracted granules, also indicated that large granules may be preferentially degraded after fruit harvest. These results are discussed in relation to control of starch degradation.