Master of Science (MS)
School of Nutrition and Food Sciences
Polyphenol compounds are widely used as antioxidants in food processing. The conventional phenolic content, scavenging DPPH free radical assays have been widely used for antioxidant evaluation. This research aimed to study the correlation between scavenging DPPH (2, 2-diphenyl-1-picrylhydrazyl) free radical activity, total phenolic content and anti-lipid-oxidation capability of natural and synthetic antioxidants and four beverages drinks. Synthetic phenol antioxidants, BHA (butylated hydroxyanisole), BHT (butylated hydroxytoluene), PG (propyl gallate), TBHQ (tert-butylhydroquinone) and naturally occurring phenolics ƒÑ-T(£\-tocopherol), CA(Chlorogenic acid), GA(Gallic acid), QCT(Quercetin), RSV(Resveratrol), and SA(Syringic acid) were examined for their total phenolic content (TPC) and scavenging DPPH free radical activity. The anti-lipid-oxidation capability of these antioxidants was determined by using a fish oil emulsion which imitated the blood serum environment. CA and GA had great phenolic content, while they were in the group of lowest anti-lipid-oxidation capability. Oppositely, BHA was in the lowest group of phenolic content but provided the greatest anti-lipid-oxidation capability. The DPPH annihilation activity of GA was equivalent to PG and QCT and among the top three performances in the assay. However, its anti-lipid-oxidation capability was four times lower than PG or QCT. In general, most of the synthetic antioxidants had poor phenolic content but demonstrated better anti-lipid-oxidation capability, while, the phenolic acids such as GA and CA, were totally reverse. Only QCT and PG exhibited great performance in all the three assays. Thus, the fish oil emulsion developed in this study could be an efficient and reliable model for the evaluation of various antioxidants which overcomes the unilateral reaction of conventional spectrophotometric assays. Tea, coffee, red wine and white wine were also investigated to assess the correlations of TPC, DPPH free radical scavenging activity and anti-lipid-oxidation capability in a fish oil emulsion model. Diversities and concentrations of the major phenolics in the four beverages were also determined. With the most abundant phenolics, red wine dominated in TPC, DPPH scavenging activity, and anti-lipid-oxidation capability. However, white wine which had better performance in the TPC and DPPH assays showed the lowest capability in preventing fish lipid oxidation. The anti-lipid-oxidation capability of tea or coffee was much higher than white wine, although the three beverages had similar TPC. Therefore, the results from TPC and DPPH assays may not always correspond to the actual anti-lipid-oxidation capabilities. As the fish oil emulsion model was designed to imitate the human serum, the obtained anti-lipid-oxidation capability could closely reflect the antioxidant activity in stabilizing lipids and reducing harmful lipid oxidation products in the serum.
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Zhu, Yongchao, "Relationship of Total Phenolic Contents, DPPH Activities and Anti-Lipid-Oxidation Capabilities of Different Bioactive Beverages and Phenolic Antioxidants" (2014). LSU Master's Theses. 624.