| Summary: | 碩士 === 國立臺灣海洋大學 === 食品科學系 === 103 === Mugilidae species include 6 genus 12 species currently, among them Mugil cephalus (MCe) is importantly economic species. Recently, the capture of the MCe was decreased, leading to the price of processed mullet roe was increased. Due to the appearance of Mugilidae fishes is similar, the species are not easy to distinguish. Besides, other Mugilidae species are cheaper than MCe, the mullet roe might be replaced by these species. On the other hand, compared to mullet roe, the oil fish roe showed similar quality in taste and flavor but with cheaper price, the mullet roe had been replaced by oil fish roe for serving and vending in recent year. After cooking and slicing, it’s hard to distinguish these two roe by its appearance. Since there had been reported that the puffer fish roe was adulterated into mullet roe and caused food poisoning, the method of identification to test the adulteration of fish roe should be estabilished. The mullet roe contained various nutrients, such as n-3 polyunsaturated fatty acid (n-3 PUFA) which is beneficial for humans. Since mullet roe were treated with high temperature before tasteing, n-3 PUFA were degraded into lipid oxidation products and effect human body health. Therefore, the stability of n-3 PUFA in mullet roe during processing period should be evaluated.
In this study, polymerase chain reaction - restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing were used to establish RFLP map of 8 common Mugilidae species in Taiwan and applied for the examination of market roe adulteration. The developed PCR-RFLP method can rapidly applied to identify the species of Mugilidae fishes and adulteration of commercial mullet roe with no adulteration found in 10 examined samples. Meanwhile, the lipid stability of mullet roe after different processing method (treating for 1, 5, and 10 min at 50oC or 100 oC) were also evaluated in this study. After treating for 10 min at 100 oC, the index of the oxidation level was increased, and PUFA were more stable compared to monounsaturated fatty acid (MUFA). The lipid extracted from processed mullet roe showed damaged effect to Caco-2 cell and lead cell apoptosis. In summary, the developed PCR-RFLP method in this study could be applied for distinguishing Mugilidae fishes and fraudulent substitution of commercial mullet roe. Besides, after heating treatment, the oxidation level mullet roe were increased, with decrease of MUFA content. The lipid extracted from processed mullet roe also showed damage to Caco-2 cell. Therefore, long period of high temperature treatment should be avoided when processing mullet roe.
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