碩士 / 國立臺灣海洋大學 / 食品科學系 / 92 / Abstract
An infrequent photosensitization case due to ingesting dried laver flakes had happened in Northern Taiwan. Our previous research suggested that the causative substances were chlorophyll a derivatives, pheophorbide a and pyropheophorbide a. The research is to study the temperature effects of storage and heat process on the content of pheophorbide a and pyropheophorbide a in three kinds of fresh edible seaweeds, Porphyra crispata, Gracilaria tenuistipitata and Ulva lactuca and one kind of market semi-processed laver, and then we invesgated the characteristics of chlorophyllase in the fresh edible seaweeds. Moreover, we will also investigate the levels of chlorophyll a derivatives and Hunter Lab values in market dried laver products.
The chlorophyll a contents of fresh seaweeds caused 70.67﹪and 95.74﹪losses during the storage process in 3℃ and 25℃, respectively. After dry heating at 20℃, the losses of chlorophyll a in seaweed samples were much slower and the degradative derivatives were less. When P. crispata heating at 60℃, the levels of chlorophyll a decreased faster than other heating temperature, and the levels of degradative derivatives were lower than 1400 ppm. The levels of chlorophyll a of G. tenuistipitata decreased to 28﹪after heating at 60℃for 2 hr. The pheophytin a contents of U. lactuca increased to 2105 ppm after heating at 40℃ for 16 hr. And the levels of pyropheophorbide a of market semi-processed laver were non-detectable after heating at 20℃ for 16 hr, but did cause its increase to 658 ppm when heating at 40℃ for 2 hr. In the study of the effect of blanching on the chlorophyll a compounds of three kinds of fresh seaweeds in boiling water, the levels of pyropheophorbide a were not detected after dipping in boiling water for 10 min.
The temperatures of maximum enzymatic activity of chlorophyllase were 50℃ for P. crispata and G. tenuistipitata, and 40℃ for U. lactuca. The optimum pH for P. crispata, G. tenuistipitata and U. lactuca were pH 8.0, 9.0 and 7.0, respectively. The chlorophyllase showed a considerable resistence to thermal treatment. The enzyme was stable for incubating at 50℃ for 30 min. And the activity was higher with substrate chlorophyll a than with pheophytin a.
Finally, we analyzed 40 samples of commercial seaweed products (dried lavers and dried laver flakes) sold in markets of Taipei, Keelung, Taichung and Kaohsiung. The results indicated the levels of pyropheophobide a of both dried lavers and dried laver flakes in Kaohsiung were higher than those in Taipei. In the aspect of Hunter Lab values between dried lavers and dried laver flakes, the a value was significantly different in Taipei’s samples, but the chroma and the hue angle were noted in Kaohsiung’s samples. Meanwhile, the L value of dried laver flakes collected from Taipei and Keelung was significantly varied.
| Identifer | oai:union.ndltd.org:TW/092NTOU5253037 |
| Date | January 2004 |
| Creators | Wei-Chun, Tu, 杜偉君 |
| Contributors | 黃登福 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 111 |
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