에과도르에서 재배한 퀴노아의 항산화 활성 및 물리화학적 특성 = Antioxidant activity and physicochemical properties of quinoa (Chenopodium quinoa) seeds cultivated in Ecuador

다국어 초록 (Multilingual Abstract)

Quinoa seed is a greatly appreciated pseudocereal native from the Andean region (Bolivia, Peru, and Ecuador). In recent years, this seed has drawn significant attention due to its remarkable nutritional content, which features an important content of gluten-free protein in combination with the presence of essential amino acids.
Six quinoa ecotypes cultivated in Ecuador were used in this study, five corresponding to white seeds and one to a green-colored seed ecotype. From the five white quinoa seeds, four belonged to bitter quinoa, the remaining one to a sweet quinoa ecotype. This research consisted of two sections, one focused in the study of the physicochemical properties of quinoa seeds and their isolated starches. The second corresponds to the examination of the antioxidant activity of quinoa seeds. The results associated to the first section are as follows:
1.1. It was assigned to every quinoa seed a short name which is used to identify it easily in the different assays. As it follows: Latacunga chaucha amarga (white bitter quinoa) = Q1; Latacunga chaucha blanca (white bitter quinoa) = Q2; Native amarga Cochasqui (white bitter quinoa) = Q3; Latacunga chaucha verde (green-colored bitter quinoa) = Q4; Tunkahuan precoz dulce (white sweet quinoa) = Q5; Tunkahuan amarga (white bitter quinoa) = Q6.

1.2. The moisture contents for Q1 to Q6 were 10.25%, 9.50%, 8.87%, 11.25%, 11.13%, and 11.38%, respectively. The crude protein contents were 13.95%, 11.76%, 14.89%, 11.65%, 14.26%, and 12.19%, respectively. The crude lipids contents were 6.47%, 7.28%, 7.50%, 7.61%, 7.14%, and 6.75%, respectively. The crude ash contents were 3.00%, 3.22%, 2.89%, 4.00%, 2.56%, and 3.22%, respectively.

1.3. The amylose contents for starches isolated from Q1 to Q6 were 14.65%, 13.50%, 12.36%, 10.83%, 12.74%, and 7.02, respectively. The crude protein contents of starches were 0.46%, 0.51%, 0.23%, 0.36%, 0.28%, and 0.33%, respectively. The crude lipid contents of starches were 0.65%, 0.24%, 0.73%, 0.42%, 0.53%, and 0.20%, respectively.

1.4. The color attributes for quinoa seeds (Q1 to Q6) are as follows: L=72.79, a=-0.81, b=14.91; L=71.63, a=-0.30, b=15.24; L=75.47, a=-1.17, b=15.15; L=69.38, a=-0.70, b=14.52; L=73.51, a=-0.61, b=15.06; L=77.74, a=-1.54, b=14.29, respectively. The color attributes for quinoa starches (Q1 to Q6) were: L=79.74, a=-1.30, b=11.34; L=81.67, a=-1.86, b=10.95; L=83.23, a=-2.14, b=11.09; L=80.63, a=-2.35, b=11.10; L=81.28, a=-1.90, b=10.79; L=84.34, a=-2.94, b=9.53, respectively.

1.5. The pasting properties for Q1 to Q6 were as follows: PV=411.75, BV=166.08, FV=427.92, SB=202.33, PKT=4:93; PV=321.58, BV=91.42, FV=331.42, SB=127.83, PKT=5:27; PV=360.58, BV=87.00, FV=374.67, SB=139.42, PKT=5:20; PV=359.75, BV=95.92, FV=372.67, SB=185.58, PKT=5:40; PV=317.08, BV=82.33, FV=328.17, SB=128.17, PKT=5:40; PV=334.17, BV=78.17, FV=343.92, SB=142.25, PKT=5:20. PV= Peak viscosity; BV=Breakdown viscosity; FV= Final viscosity; SB= Setback viscosity; PKT= Peak time. All units are expressed as RVU except for PKT.

1.6. The water solubility index for Q1 to Q6 corresponding to quinoa starches were: 1.64%; 1.37%; 1.46%; 1.46%, 1.08%, and 1.42%. The water absorption of quinoa starches were: 3.12; 3.16; 2.96; 3.21; 3.26; 3.41 g, respectively.

1.7. The water-binding capacity of quinoa starches (Q1 to Q6) were: 82.65; 93.36; 92.87; 93.34; 83.53; 92.94, respectively.

1.8. The quinoa starches showed freeze-thaw stability consisted of five freeze-thaw consecutive cycles. The results of Q1 to Q6 for cycle #1 were: 0.22%, 9.76%, 2.34%, 4.36%, 13.46%, and 9.15%, respectively. For cycle #2: 0.47%, 6.42%, 2.08%, 3.03%, 11.24%, and 2.39%, respectively. For Cycle #3: 1.81%, 1.27%, 0.80%, 1.88%, 6.28%, and 0.36%, respectively. For Cycle #4: 1.60%, 0.54%, 0.03%, 1.82%, 4.41%, and 0.26%, respectively. Finally, for Cycle 5: 0.60%, 0.50%, 0.10%, 1.45%, 3.26%, and 0.22%, respectively.

1.9. Field emission scanning electron microscopy (FE-SEM) indicated the irregular, polygonal morphology characteristic of quinoa starch. The size of the quinoa starch granules varied from 0.7 to 1.9 µm, approximately. No differences in starch granule morphology were detected among the different genotypes.

1.10. The swelling power (SP) and solubility (S) for Q1 to Q6 were performed from 65°C to 95°C. The SP and S values obtained at 65°C were: SP=9.48%, S=5.48%; SP=9.47%, S=5.27%; SP=8.85%, S=5.20%; SP=9.44%, S=5.22%; SP=8.92%, S=4.32%; SP=9.11, S=3.82, respectively. For 70°C were: SP=10.10%, S=6.34%; SP=10.69%, S=6.25%; SP=9.65%, S=6.14%; SP=10.10%, S=6.42%; SP=9.67%, S=5.02%; SP=9.71%, S=4.63%, respectively. For 75°C were: SP=10.54%, S=6.89%; SP=11.63%, S=6.70%; SP=10.40%, S=6.21%; SP=11.98%, S=7.14%; SP=10.90%, S=6.61%; SP=11.54%, S=6.06%, respectively. For 80°C were: SP=11.82%, S=8.23%; SP=12.42%, S=8.54%; SP=11.94%, S=8.31%; SP=12.34%, S=9.13%; SP=11.61%, S=7.69%; SP=12.28%, S=8.21%, respectively. For 85°C were: SP=13.93%, S=14.87%; SP=13.68%, S=11.99%; SP=14.25%, S=11.89%; SP=13.50%, S=10.39%; SP=13.09%, S=7.79%; SP=13.49%, S=11.08%, respectively. For 90°C were: SP=15.81%, S=8.57%; SP=15.58%, S=15.66%; SP=14.99%, S=7.68%; SP=15.16%, S=10.69%; SP=13.44%, S=10.04%; SP=15.15%, S=10.96%, respectively. Finally, for 95°C were: SP=17.64%, S=8.96%; SP=17.80%, S=10.57%; SP=17.21%, S=8.08%; SP=17.57%, S=8.65%; SP=16.89%, S=9.61%; SP=18.22%, S=9.17%, respectively.
The second part of this study was composed of the evaluation of the antioxidant capacity of the quinoa seed extracts.
2.1. The total phenolic contents of extracts from Q1 to Q6 were: 80.20 mg GAE/g; 92.20 mg GAE/g; mg GAE/g; 74.20 mg GAE/g; 94.20 mg GAE/g; 62.20 mg GAE/g; 53.53 mg GAE/g, respectively.

2.2. The total flavonoid contents of extracts from Q1 to Q6 were: 104.33 mg QE/g; 112.11 mg QE/g; 100.44 mg QE/g; 124.33 mg QE/g; 86.11 mg QE/g; 38.67 mg QE/g, respectively.
2.3. The DPPH radical scavenging activity of extracts from Q1 to Q6 was: 26.75 µmol TE/g; 24.56 µmol TE/g; 21.96 µmol TE/g; 27.96 µmol TE/g; 16.67 µmol TE/g; 5.96 µmol TE/g, respectively.

2.4. The ABTS radical scavenging activity of extracts from Q1 to Q6 was: 32.34 µmol TE/g; 35.98 µmol TE/g; 36.40 µmol TE/g; 43.98 µmol TE/g; 31.30 µmol TE/g; 26.15 µmol TE/g, respectively.

2.5. The results corresponding to SOD-like activity of extracts from Q1 to Q6 was: 58.20%, 61.70%, 63.16%, 64.60%, 46.37%, and 42.24%, respectively.

2.6. The results for metal chelating activity of extracts from Q1 to Q6 was: 58.02 µmol EDTAE/g, 59.65 µmol EDTAE/g, 44.64 µmol EDTAE, 63.30 µmol EDTAE, 33.80 µmol EDTAE, and 27.48 µmol EDTAE, respectively.

2.7. The EC50 values related to antioxidant activity for DPPH radical scavenging activity were: 2.02 mg/ml; 1.16 mg/ml; 2.84 mg/ml; 0.42 mg/ml; 3.05 mg/ml; and 18.51 mg/ml, respectively. The EC50 values for ABTS radical scavenging were: 4.56 mg/ml; 2.23 mg/ml; 7.47 mg/ml; 1.42 mg/ml; 8.26 mg/ml; and 15.64 mg/ml, respectively. The EC50 values corresponding to SOD-like activity were: 7.45 mg/ml; 5.12 mg/ml; 3.46 mg/ml; 2.74 mg/ml; 10.45 mg/ml; 16.15 mg/ml, respectively. The EC50 values for metal chelating activity were: 6.21 mg/ml; 4.45 mg/ml; 8.28 mg/ml; 2.69 mg/ml; 11.12 mg/ml; and 15.92 mg/ml, respectively.

2.8. Seven phenolic compounds were identified in the six quinoa samples, and their contents were as follows: Gallic acid: 176.20 µg/mL; 173.39 µg/mL; 194.85 µg/mL; 147.03 µg/mL; 90.88 µg/mL and 288.29 µg/mL, respectively. p-Hydroxybenzoic acid: 36.90 µg/mL; 36.90 µg/mL; 38.48 µg/mL; 36.71 µg/mL; 33.70 µg/mL and 37.33 µg/mL, respectively. Rutin: 42.69 µg/mL; 14.03 µg/mL; 14.28 µg/mL; 11.72 µg/mL; 2.47 µg/mL and 54.16 µg/mL, respectively. p-Coumaric acid: 126.88 µg/mL; 138.20 µg/mL; 140.43 µg/mL; 142.55 µg/mL; 104.63 µg/mL and 131.98 µg/mL, respectively. Ferulic acid: 67.75 µg/mL; 90.60 µg/mL; 65.01 µg/mL; 88.73 µg/mL; 41.50 µg/mL and 67.03 µg/mL, respectively. Taxifolin: 32.77 µg/mL; 43.50 µg/mL; 32.24 µg/mL; 38.09 µg/mL; 28.84 µg/mL and 42.98 µg/mL, respectively. Finally, the last phenolic compound was trans-m-Coumaric acid: 4.72 µg/mL; 3.89 µg/mL; 3.95 µg/mL; 2.72 µg/mL; 1.90 µg/mL and 0.68 µg/mL, respectively.
Keywords: Quinoa, Antioxidant activity, Starch, Physicochemical properties, Phenolic compounds

목차 (Table of Contents)

• I. Introduction 1
• II. Materials and Methods 5
• 2.1. Materials 5
• 2.1.1. Plant Materials 5
• 2.1.2. Chemicals and Reagents 7
• 2.1.3. Statistical Analysis 7
• 2.2. Methods 8
• 2.2.1. Physicochemical properties of quinoa seeds and starches 8
• 2.2.2. Antioxidant activity of quinoa seeds 18
• III. Results and Discussion 25
• 3.1. Physicochemical properties of isolated quinoa starch 25
• 3.1.1. Proximate composition of quinoa seeds 25
• 3.1.2. Amylose, protein and lipids content of quinoa starches 28
• 3.1.3. Color attributes of quinoa seeds and starches 29
• 3.1.4. Pasting properties of quinoa starches 32
• 3.1.5. Water solubility index and water absorption index 34
• 3.1.6 Water-binding capacity of quinoa starches 36
• 3.1.7. Freeze-thaw stability 37
• 3.1.8. Field Emission Scanning Electron Microscopy (FE-SEM) 40
• 3.1.9. Swelling power and solubility of quinoa starches 42
• 4.1. Antioxidant Properties of Quinoa Seeds 45
• 4.1.1. Total phenolic content 45
• 4.1.2. Total flavonoid content 46
• 4.1.3. DPPH free radical scavenging ability 48
• 4.1.4. ABTS•+ radical scavenging activity 49
• 4.1.5. Superoxide dismutase-like activity 50
• 4.1.6. Metal chelating activity 51
• 4.1.7. EC50 Values of quinoa seed extracts 52
• 4.1.8. Chromatographic determination of phenolic acids and flavonoids 54
• V. References 66
• Abstract (Korean Version) 80