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Antioxidant Activity of Premature Mandarin (Citrus unshiu) and Its Effect on the Lipid Oxidation of Horse Oil-in-Water Emulsion

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Abstract
Mandarin is mainly used as a fresh product or juice in the food industry. During harvesting and processing mandarins, by-products including premature mandarins and mandarin peels are occurred and discarded. However, mandarin by-products are known to contain high concentrations of flavonoids, polyphenols, and organic acids with health functions. In this study, the antioxidant activity of premature and mature mandarin extracts and their potentials as functional food materials were investigated. The total phenolic and flavonoid contents (TPC, TFC) were measured and the flavanone compounds were analyzed by HPLC for identification and quantification of antioxidant active ingredients. The DPPH and ABTS+ radical, hydrogen peroxide, and hydroxyl radical scavenging activity, superoxide dismutase activity, and reducing power were measured for in vitro antioxidant activities. Additionally, to investigate the effect of premature mandarin on the lipid oxidation, premature and mature mandarin peel extracts, α-tocopherol, and Trolox were added to horse-oil-in-water (HO/W) emulsions, which were stored at 40 °C for 30 days thiobarbituric acid reactive substances (TBARS) were measured. The TPC and TFC of premature mandarin peel extract (PMP), mature mandarin peel extract (MP), premature mandarin juice (PMJ), and mature mandarin juice (MJ) were 94.04, 79.15, 37.05, and 31.20 mg GAE/g and 43.99, 23.51, 4.20, and 0.09 mg QE/g, respectively. The flavanone compounds in PMP, MP, PMJ, and MJ were identified only as glycoside form flavanones, hesperidin and narirutin with total amounts of 5.33 to 128.16 mg/g. The in vitro antioxidant activities of mandarin peels (PMP and MP) were higher than those of mandarin juices (PMJ and MJ). When compared to the premature and mature mandarins, in vitro antioxidant activities of premature were higher than mature. Especially, the mandarin peel extracts (PMP and MP) were particularly active in scavenging hydrogen-containing radicals. For the lipid oxidation of HO/W emulsions, α-tocopherol at 0.2 mg/mL acted as a pro-oxidant to promote lipid oxidation while mandarin peel extracts at 0.5 and 1 mg/mL and Trolox at 0.2 mg/mL acted as antioxidants to inhibit lipid oxidation. These results confirmed the potential of premature and mature mandarin peels, by-products of mandarin, for the functional food and cosmetics materials.
본 연구에서는 제주산 풋귤과 완숙귤 추출물의 in vitro 항산화 활성을 평가하였다. 귤 껍질 추출물(PMP와 MP)과 주스(PMJ와 MJ)의 총 폴리페놀 및 플라보노이드 함량은 31.20-94.04mg GAE/g, 0.09-43.99mg QE/g이었다. PMP, MP, PMJ, MJ의 flavanone 함량은 각각 128.16, 86.12, 10.32, 5.33mg/g로 정량화되었다. 풋귤과 완숙귤에서는 배당체 형태인 hesperidin과 narirutin이 검출되었으며, 비배당체 형태인 hesperetin과 naringenin는 검출되지 않았다. DPPH와 ABTS+ 라디칼 소거 활성은 PMP에서 가장 높았고 MJ에서 가장 낮았다. Hesperidin은 narirutin 보다 높은 소거 활성을 보였으며, 배당체 flavanone보다 비배당체 flavanone이 더 높은 소거 활성을 보였다. 풋귤, 완숙귤, flavanone화합물의 hydrogen peroxide와 hydroxyl 라디칼 소거 활성은 다른 in vitro 항산화 활성보다 높았다. 풋귤과 완숙귤 추출물의 SOD 활성은 DPPH와 ABTS+ 라디칼 소거 활성보다 높았지만 hydrogen peroxide와 hydroxyl 라디칼 소거 활성보다는 낮았다. Hesperetin을 제외한 flavanone 화합물의 SOD 활성은 유의적인 차이가 없었다. PMP와 MP의 환원력은 PMJ와 MJ보다 높았으며, 풋귤이 완숙귤보다 높은 환원력을 보였고, hesperidin과 hesperetin이 narirutin과 naringenin 보다 높았다. 결론적으로 in vitro 항산화 활성은 귤의 총 폴리페놀 및 플라보노이드 함량과 flavanone 농도와 높은 상관관계가 있을 것으로 예상된다.
풋귤과 완숙귤 추출물의 천연 항산화제로서의 효능을 확인하기 위해 in vitro 항산화 활성이 높았던 껍질 추출물(PMP와 MP)을 HO/W 에멀션에 첨가하여 지질 산화 안정성을 조사하였다. .
저장 초기에는 PMP와 MP가 첨가된 HO/W 에멀션의 TBARS는 Trolox보다 높았으나, 30일 저장 후에는 α-T, Trolox가 첨가된 HO/W 에멀션과 Control보다 TBARS가 낮았다. 따라서 PMP와 MP는 지질 산화를 억제하는 항산화제 역할을 했다. 0.2 mg/mL 농도의 α-T가 첨가된 HO/W 에멀션은 저장 기간 중 가장 높은 TBARS를 보였으며, α-T는 HO/W에서 pro-oxidant로 작용하였다. 동일한 농도의 Trolox를 첨가한 HO/W 에멀션은 α-T가 첨가된 HO/W 에멀션보다 지질 산화 억제 효과가 높았다.
결론적으로 귤을 생산하고 가공하는 과정에서 발생되는 풋귤과 완숙귤 껍질은 기능성 화합물의 풍부한 공급원이 될 수 있으며, 높은 항산화 활성을 나타내어 식품, 화장품, 제약 산업에서 천연 항산화제로 사용될 수 있는 가능성을 확인하였다.
Author(s)
Lee, Seo Gyeong
Issued Date
2021
Awarded Date
2021. 2
Type
Dissertation
URI
https://oak.jejunu.ac.kr/handle/2020.oak/23475
Alternative Author(s)
이서경
Affiliation
제주대학교 대학원
Department
대학원 식품공학과
Advisor
김현정
Table Of Contents
ABSTRACT 1
1. Introduction 5
2. Materials and Methods 7
2.1. Materials and chemicals 7
2.2. Preparation of premature and mature mandarin peel extract 7
2.3. Preparation of premature and mature mandarin juice 8
2.4. Determination of total phenolic and flavonoid contents 8
2.5. Analysis of flavanone compounds by HPLC 9
2.6. In vitro antioxidant activity 10
2.6.1. DPPH radical scavenging activity 10
2.6.2. ABTS+ radical scavenging activity 10
2.6.3. Hydrogen peroxide scavenging activity 10
2.6.4. Hydroxyl radical scavenging activity 11
2.6.5. Superoxide dismutase activity 11
2.6.6. Reducing power 12
2.7. Preparation of horse oil-in-water emulsions 12
2.8. Measurement of lipid oxidation products of HO/W emulsion 13
2.9. Statistical analysis 14
3. Results and Discussion 15
3.1. Total phenolic and flavonoid contents of premature and mature mandarin extracts 15
3.2. Flavanone compounds of premature and mature mandarin extracts 17
3.3. In vitro antioxidant activities of premature and mature mandarin extracts and flavanone standards 20
3.4. The IC50 of in vitro antioxidant activity in premature and mature mandarin extracts 25
3.5. Effect of premature and mature mandarin peel extracts on lipid oxidation of HO/W emulsions 28
4. Conclusion 31
국문요약 33
References 35
Degree
Master
Publisher
제주대학교 대학원
Citation
Lee, Seo Gyeong. (2021). Antioxidant Activity of Premature Mandarin (Citrus unshiu) and Its Effect on the Lipid Oxidation of Horse Oil-in-Water Emulsion
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General Graduate School > Food science and Engineering
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