| Summary: | 碩士 === 國立中興大學 === 動物科學系所 === 101 === Sanitation and safety of foods have become great concerns for consumers. Synthetic antioxidant, such as BHA (butylated hydroxyanisole) and BHT (butylated hydroxytoluene) have been doubted for their safety even though they exhibit good antioxidant activities. This concern has led to a great interest in development of natural antioxidants which might at least partially replace synthetic ones. Garlic (Allium sativum) has been used universally as a flavoring ingredient, and materials of functional food and traditional medicine. Previous studies have shown that garlic contains some phenolic compounds and sulfur compounds which contribute to their antioxidant activities. However, garlic skin, an inedible part and a waste which produced during manufacturing, has not been studied intensely for their uses. Many studies which regarding the re-utilization of agricultural by-products have been conducted due to their functional components. Ultrasonic extraction has gained much attention due to its higher extraction efficiency as well as shorter extraction time when compared to the conventionally maceration methods. Furthermore, it creates less impact on the phenolic compounds when compared to other extraction methods. Therefore, the objectives of this study were (1) to investigate the effect of ultrasonic extraction and extraction solvents on the antioxidant properties of garlic skin extracts and (2) to evaluate the qualities of fresh and pre-cooked pork patties which were added with garlic skin extracts during refrigerated storage.
The result showed that the water extracts exhibited higher yield, while the ethanol extracts showed higher total phenolic contents, DPPH (1,1-diphenyl-2-picrylhydrazyl) scavenging activity, ferrous ion chelating ability and reducing power. Ethanol extracts also showed higher yields of phenolic compounds obtained form the dry materials. On the other hand, garlic skins which were ultrasonically extracted for 15 min had equivalent or higher total phenolic contents than the ones conventionally extracted for 12 to 24 h. However, the DPPH scavenging activity of ultrasonic extracts was similar to the treatments macerated for 1.5 to 3 h as using water as an extraction solvent. Therefore, ethanol extracts which were ultrasonically extracted for 15 min and conventionally extracted for 12 h were chosen to be added for the further study. In the 2nd part of study, addition of garlic skin ethanol extract decreased the L* value (lightness) and retarded the decreasing of a* value (redness) of fresh and pre-cooked patties during storage at 4 °C. For the lipid oxidation evaluation, CD (conjugated dienes) and TBARS (2-thiobarbituric acid reactive substances) values of the fresh patties were increased during storage, whereas the both values of pre-cooked were decreased after storage for 9 days. Addition of extracts significantly retarded the increases of CD and TBARS values for fresh and pre-cooked patties. The treatments with addition of extracts showed lower rancid flavor and higher sensory acceptance than controls during refrigerated storage. In conclusion, the ethanol garlic skin ultrasonic extracts had equivalent antioxidant activities than that of the treatments conventionally extracted for long time. Addition of 0.1% extract could retard lipid oxidation and sensory deterioration effectively and improve overall acceptance of meat products. Not only dramatically increase the uses of garlic skin, the results of this study clearly demonstrated the potent development of natural antioxidant and application in meat and other foods in the future.
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