Evaluation index for fish freshness based on EEM analysis
|摘要:||本篇論文主要是利用光學螢光量測來探討並分析魚肉之新鮮度並找出光學的指標，期許對於食品及工業上希望能有所貢獻與發展。相較於傳統新鮮度檢測方法，化學性判讀時間過長、易破壞魚體而造成漁業及食品業的損失，此種光學方法具有非侵入式檢測特性，並期望能達到快速檢測之目的。實驗選用兩種魚類，八隻澎湖縣養殖場的海鱺，平均重量約為5±1.0公斤，以及八隻新竹縣活魚餐廳的紅魽，平均重量約1±0.2公斤。檢測部分與方式係將活魚處理切成相同大小的魚肚及魚背，利用自行架設的螢光光譜量測系統來進行實驗，觀察死亡後24小時內魚體光譜的時序變化。同一時間亦進行魚新鮮度的傳統檢測法，利用商用高效能液相層析儀(HPLC)來進行定性及定量分析，以獲得傳統方法的新鮮度標準K值作為魚肉新鮮度標準。由螢光的激發放射矩陣光譜之結果顯示，在激發光330~360 nm、放射光400~500 nm之間有明顯的螢光訊號。此訊號的最大值位在螢光波長470 nm及430 nm處，與菸鹼醯胺腺嘌呤二核苷酸(NADH)及第一型和第五型膠原蛋白在激發光330~360 nm所產生的螢光光譜位置雷同。而根據正規化處理而獲得光學指數數值，以變異數分析此數值與死亡後24小時之關聯性，發現此數值隨著死亡後時間逐漸地降低，且具顯著性差異(p value<0.05)，這表示可將此一數值視為另外一種新鮮度指標。由HPLC結果顯示，每隻紅魽的代謝變化速度皆不相同，推測原因可能是不同魚體差異性造成、環境及處理過程的差異性，因此會影響K值變化，推測也會影響魚體裡某些螢光成分的代謝。但整體結果來說光學指標與K值的數值大小大致呈負相關。而光學指標的高低結果也代表著魚死後肌肉所進行的僵直化及嫩化效應所造成的。是故，以目前的研究結果，此光學指標是可以用來判斷剛死亡的魚肉及生魚片的品質。|
In this study, the autofluorescence emitted from fish tissue is measured as an optical evaluation index for freshness identification. Because of the time-consuming and invasive nature of the traditional method, it causes property loss in the fishery and food industries. A quick and noninvasive method is necessary. The result can be applied to the fishery and food industries for quality control. With the quickness of the fluorescence technique, it could improve the procedure of detection. The species chosen are eight cobias, which weigh 5±1.0 kilograms, from a marine products farm in Penghu and eight Seriola dumerili, which weigh 1±0.2 kilograms, from a seafood restaurant near Hsinchu Science Park. The fish were sliced at the abdomen and dorsum. Then, the fluorescence from the tissue was measured within 24 hours after the fish had died by using Y-type fiber. Meanwhile, traditional detection was employed by extracting ATP degradation products and calculating K value to confirm fish freshness. From the results of the Excitation-Emission matrix (EEM), the two peaks in excitation wavelength were 330 to 360 nm, and emission wavelengths were 400 to 500 nm. The two peaks were at the 470 nm and 430 nm emission wavelengths, respectively. It has been shown that the fluorescence indicates that the major contributors are from Nicotinamide adenine dinucleotide (NADH), collagen type I, and collagen type V. Analysis of variance (ANOVA) showed that the intensity of fluorescence decreases with refrigeration time (p value < 0.05). Also, the chemical result presents that there are different metabolism rates between different fish species. It is known that with different treatments and growing environments of fish can affect the K value and even the fluorophores in fish tissue. On the whole, the optical index is negatively correlated to the K value index. The value of the optical index is that it can measure the process of rigor mortis and the tenderization of fish muscle. The optical index can be applied to quality control for the freshness of fish fillet and sashimi.
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