pissn 2384-0269 eissn 2508-3635 J. Milk Sci. Biotechnol. 2016;34(4):263-270 https://doi.org/10.22424/jmsb.2016.34.4.263 ARTICLE 스테비아잎추출물을첨가한그릭요거트의항산화활성변화 윤지우 김하나 하태준 박서희 이세미 안성일 주진우 * 김거유 강원대학교동물생명과학대학축산식품과학전공 Antioxidant Activity of Greek-style Yogurt with Stevia Leaf Extracts Ji-Woo Yoon, Ha-Na Kim, Tae-Jun Ha, Su-Hee Park, Sae-Me Lee, Sung-Il Ahn, Jin-Woo Jhoo and * Gur-Yoo Kim Dept. of Animal Products Food Science Program, College of Animal Life Sciences, Kangwon National University, Chuncheon, Korea Abstract This study was carried out to evaluate the antioxidant activity and total polyphnol content of Greek-style yogurt in 12% solid content with added stevia leaf extracts. Stevia leaf extracts used as sweetener in preparing Greek-style yogurt were prepared in hot water (100 for 6 h 3 times, and by 70% fermented ethanol for 24 h at room temperature 3 times). The antioxidant activities were measured by assessing the radical scavenging effect through DPPH, ABTS, and FRAP assays. To identify the compounds present, total polyphenol content was evaluated using a Folin-Dennis assay. The capability to scavenge free radicals and total polyphenolic content were the highest in Greek-style yogurt containing 1% stevia extract and fermented in 70% ethanol. According to the results, antioxidant activities significantly increased when high concentration of stevia extracts were added to the yogurt (p<0.05). Therefore, these results suggest that stevia leaf extracts can be used as a source of functional compounds in Greek-style yogurt. We also suggest that fermented ethanol extraction can be used to obtain stevia leaf extracts. Keywords stevia extract, Greek-style yogurt, antioxidant, hot water extraction, fermented ethanol extraction 서론 Received: December 9, 2016 Revised: December 17, 2016 Accepted: December 20, 2016 *Corresponding author : Gur-Yoo Kim, Dept. of Animal Products Food Science Program, College of Animal Life Sciences, Kangwon National University, Chuncheon, Korea. Tel : +82-10-9466-8647, Fax : +82-33-259-5574, E-mail : gykim@kangwon.ac.kr 현대인들의식습관과생활습관의서구화로각종성인병과질병이증가하고있으며고령화시대가가속화될수록사람들의건강에대한관심도또한함께증가하고있다. 또한사람들의생활수준이높아지면서식품은더이상배고픔을위해먹는것이아니라건강을향상시키고더나은삶을위해섭취하는것으로변화하고있다. 따라서유제품시장에서도기능성이향상된제품이개발되고있으며요구되고있는실정이다. 유제품시장에서대부분의유제품의소비가정체나소폭감소형태를보이는것과는대조적으로발효유제품의경우에는매출의신장을보이고있고꾸준한소비가이루어지고있다 (Kwang, 2007). 특히, 최근그릭요거트에대한영양학적이점이알려지면서소비자들의관심이높아지고있는추세이다. 그릭요거트는일반요거트에비해유청을더제거하여고형분함량을높이고더견고한질감을가지고있는 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/ licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Copyright Korean Society of Dairy Science and Technology. All rights reserved. 263
윤지우 김하나 하태준 박서희 이세미 안성일 주진우 김거유 발효유로서일반발효유에비해단백질함량은약 2배이상높고칼슘과식이섬유가보다풍부하다고알려져있다 (Phadungath, 2015). 파라과이와브라질의고산지대에자생하는국화과다년생초본식물인스테비아 (Stevia rebaudiana Bertoni) 의줄기와잎에서추출되는 stevioside 는설탕의 200~300배에달하는감미도를가지고있으며 (Hanson and De Oliverira, 1993), 칼로리가낮고열과 ph에안정성이높아각종가공식품에감미료로이용되고있다. 스테비아의추출물에는 stevioside 외에도다양한폴리페놀또한함유되어있어녹차의 20배이상에달하는높은항산화능을가지고있는것으로밝혀져있다 (Yamamoto et al., 200. 항산화능은노화와각종질병의원인이되는활성산소종 (reactive oxygen species, ROS) 을제거하는능력으로산소호흡등에의하여생성된반응성이매우높은활성산소종이체내세포나조직을손상시키는산화적스트레스 (oxidant stress) 를완화시켜준다 (Fridovich, 1978; Halliwell et al., 1992). 이러한항산화활성을가지고있는천연항산화제나합성항산화제가많이개발되어사용되어왔으나보다안전하고항산화활성이높은항산화제원료의개발이끊임없이요구되고있어스테비아의항산화능에주목할만하다고할수있다 (Choe and Yang, 1982; Lee et al., 2010). 본연구에서는영양적가치가우수한그릭스타일요거트에스테비아잎추출물을감미료로첨가하여항산화활성을알아보고발효유의항산화기능성향상에대하여알아보고자하였다. 재료및방법 1. 스테비아추출물의조제실험에서사용된스테비아는한국스테비아 에서재배, 수확, 건조된잎을공급받아사용하였으며추출은열수추출법 (hot water extraction, HWE) 과발효주정추출법 (fermented ethanol extraction, FEE) 을사용하였다. 열수추출은건조된스테비아잎 100 g에 1차증류수 3 L를가하여 100 로 6시간추출한후스테비아여과물을 3회추출하여총 9 L 열수추출하였고감압농축한뒤동결건조하여분말형태로열수추출물로이용하였다. 발효주정추출은건조된스테비아잎 100 g에 70% 발효주정 3 L를가하여실온에서 24시간추출하였다. 열수추출과마찬가지로 3회추출하여총 9 L를추출하여감압농축 (EYELA N-1000, RIKAKIKAI Co., LTD., Tokyo, Japan) 한뒤동결건조 (EYELA FD-1000, RIKAKIKAI Co., LTD., Tokyo, Japan) 하여분말형태로발효주정추출물로이용하였다. 2. 스타터 (Starter) 의제조그릭요거트의제조시사용된스타터 (stater) 는 1차증류수 88 ml에탈지분유 ( 서울우유 ) 12 g을첨가하여고형분함량을 12% 로맞추어 95 에서 15분간멸균하였고 37 로식혀동결건조되어있는유산균을 0.24% 접종하여 37 incubator 에서 6시간발효하여사용하였다. 접종한유산균은상업용혼합균주인 Yoflex Harmonic(Chr. Hansen Holdings A/S, Hersholm, Denmark) 을사용하였다. 3. 그릭요거트 (Greek-style yogurt) 의제조그릭요거트제조는시중에판매하고있는시유 ( 매일유업 ) 에탈지분유 ( 서울우유 ) 와감미료를전체 volume의 12% 로첨가하여고형분함량을 12%(w/v) 증가시켰고 stater 3%(w/v) 를접종한뒤 incubator 에서 8시간발효하여시료로사용하였다. Sample 의제조함량은 Table 1과같다. 스테비아추출물을첨가한요거트는당을전혀첨가하지않은 reference 와시중에판매되고있는발효유에당첨가로가장많이사용되고있는프락토올리고당을 0.5% 첨가한 control을비교하였다. 4. DPPH 라디칼소거능시료의전자공여능은 Blois의방법 (Blois MS, 1958) 을이용하여측정하였다. 각시료및대조군의요거트를 1 g 측정하여메탄올 9 ml에서추출한후 1,000 rpm으로 4 에서 15분간원심분리하였다. 그후상등액 1 ml를다시메탄올 9 ml와혼합하여 100배희석 (10 mg/ml) 한시료 100 μl와메탄올에녹인 100 mm의 2,2-diphenyl-1-picrylhydrazyl(DPPH, sigma Chemical Co., St. Louis, MO, USA) 용액 150 μl를 96 well-plate에혼합하였다. 상온에서 30분간반응시킨후분광광도계 (Macro plate reader, BioTek, USA) 를이용하여 517 nm의영역에서흡광도를측정하였다. 라디칼소거율 (%) 은다음의식에대입하여계산되었다. Scavenging activity(%) = (1-A sample /A blind ) 100 여기에서 A sample 은시료와 DPPH 용액과혼합한후측정한흡광도이며, A blind 는 DPPH 용액에시료대신메탄올을 100 μl를첨가하여측정한흡광도이다. 5. ABTS 라디칼소거능 ABTS 라디칼소거능측정은 ABTS + cationdecolourisation assay 방법을변형하여측정하였다. 2,2'-azinobis-(3-ethylbenzothiazoline- 264 J. Milk Sci. Biotechnol. 2016;34(4):263-270
Antioxidant Activity of Yogurt with Stevia Table 1. Composition of sample added stevia extracts by hot water and fermented ethanol 70% 2) 3) Ingredients (%) Treatment Reference Control GHW0.5% GHW1% GFE0.5% GFE1% Milk 88 88 88 88 88 88 Skim milk powder 12 11.5 11.5 11 11.5 11 Oligosaccharide 0.5 HWE 2) 0.5 1 FEE 3) 0.5 1 Starter 3 3 3 3 3 3 Reference: Greek-style yogurt without sweetener, Control: Greek-style yogurt with oligosaccharide 0.5%, GHW0.5%: Greek-style yogurt with HWE 0.5%, GHW 1%: Greek-style yogurt with HWE 1%, GFE 0.5%: Greek-style yogurt with FEE 0.5%, GFE 1%: Greek-style yogurt with FEE 1% HWE=Stevia extracts prepared by hot water extraction. FEE=Stevia extracts prepared by 70% fermented ethanol extraction. 6-sulphonic acid)(abts, sigma Chemical Co., St. Louis, MO, USA) 을 7 mm 농도에맞게증류수로조제하고 potassium persulfate(m.w=270.3 를 140 mm 농도에맞게증류수로제조하였다. ABTS 용액 5 ml와 potassium persulfate 용액 88 μl 를혼합하여실온의암실에서 12~16시간동안반응시켜 ABTS + stock solution 을제조하였고반응시킨 ABTS + stock solution (working ABTS + solution) 을에탄올로희석하여 734 nm에서흡광도가 0.70±0.02 가되도록조절한후시약으로사용하였다. 시료의제조는 DPPH 시료와마찬가지로시료를 1 g 칭량하여에탄올 9 ml와혼합추출한후 4 에서 1,000 rpm으로 15분간원심분리한후상등액 1 ml와에탄올 9 ml를다시혼합하여 100배희석 (10 mg/ml) 하였다. 10 μl의 sample 에 190 μl의 ABTS solution 을 96 well-plate 에첨가한후상온에서 30분간반응시켜 734 nm에서흡광도를측정하였고라디칼소거율 (%) 은다음의식에대입하여계산되었다. Scavenging activity(%)=(1-a sample /A blind ) 100 3.6으로조정하여 ( acetate buffer로사용하였다. 0.01 M의 2,4,6-tripyridyltriazine(TPTZ, M.W=312.33) 을 40 mm HCl 에혼합하여 (2) TPTZ solution 을제조하였고 ferric chloride (M.W=270.3) 도마찬가지로 40 mm HCl에혼합하여 0.02 M 농도로맞추어 (3) ferric chloride solution으로제조하였다. 환원력을측정하는데사용된 working FRAP buffer 는위의시약을 ( : (2) : (3) = 10 : 1 : 1의비율로혼합한후 37 에서 30분간안정화시켜사용하였다. 시료의제조는처리군과대조군의요거트를 1 g 칭량하여증류수 9 ml와혼합추출한후원심분리기 4 에서 1,000 rpm으로 15분간원심분리하여 1 ml의상등액과증류수 9 ml를다시혼합하여 100배희석 (10 mg/ml) 한후사용하였다. 96 well-plate 에시료 25 μl와시약 175 μl를혼합한후암실에서 30분간반응시킨다음 593 nm에서흡광도를측정하였다. 표준물질은 gallic acid를이용하여표준곡선을제작하고 gallic acid equivalent(gae) 로환산하여환원력을나타내었다. Gallic acid 의농도는 0, 0.02, 0.05, 0.1, 0.2, 0.3, 0.5 mg/l 로맞추어표준곡선을작성하였다. 여기에서 A sample 은시료를 ABTS solution 과혼합한후측정한흡광도이며, A blind 는 ABTS + solution 에시료대신에탄올 10 μl를첨가하여측정한흡광도이다. 6. 환원력 (FRAP) 측정환원력 (Ferric Reducing Antioxidant Potential ability, FRAP) 의측정은 Benzi와 Strain(1996) 의방법을이용하였다. FRAP 측정의시약제조는 sodium acetate(m.w=82.03) 을 0.25 M로증류수로제조한후 1 M의 NaOH와 1 M의 HCl을이용하여 ph를 7. 총폴리페놀함량측정총폴리페놀함량측정은 Folin-Dennis 법을이용하였다. 사용된시료는대조군과처리군을 1 g 칭량하여증류수 9 ml와혼합해원심분리하여상등액만을다시증류수 9 ml와혼합해 100배희석 (10 mg/ml) 하였다. 시료 50 μl와 Folin-Ciocalteu s phenol regent(sigma Chemical Co., St. Louis, MO, USA) 20 μl를혼합하여 3분간실온에서반응시킨후 sodium carbonate 포화용액 30 μl를첨가하고실온에서 30분간반응시켜증류수 100 μl 를더첨가하여총 volume 을 200 μl로맞춘후 750 nm에서흡 J. Milk Sci. Biotechnol. 2016;34(4):263-270 265
윤지우 김하나 하태준 박서희 이세미 안성일 주진우 김거유 광도를측정하였다. 표준물질은 gallic acid를사용하였고총폴리페놀함량은 gallic acid equivalent(gae) 로나타내었다. 표준곡선을작성할때사용한 gallic acid의농도는 0.06, 0.15, 0.3, 0.6, 0.9, 1.5 mg/l로맞추어작성하였다. 8. 통계분석본실험에서 3회반복실험하여얻은결과는 SPSS statistics 20 (IBM, Korea) 을사용하여분산분석하였으며, 집단간비교를위한사후분석은 Turkeyb 방법으로 5% 유의수준에서처리간의유의성을검증하였다. 결과및고찰 1. DPPH 라디칼소거능 DPPH 라디칼은생체내에생성되는라디칼은아니지만그자체로홀수전자를가지고있어산화방지제로부터전자또는수소를공여받아라디칼이소거될수있으며, 보라색을띠고있어 517 nm에서최대흡광도를나타낸다. 이러한라디칼이띠고있는색깔은라디칼이환원되어소거되면서노란색으로변하게되어흡광도가감소하게된다. DPPH는이러한원리를이용하여흡광도를이용하여산화방지제의라디칼소거능을측정하는항산화능측정실험방법이다. 스테비아추출물을첨가한그릭요거트의 DPPH 라디칼소거능 (%) 을실험한결과, DPPH 라디칼소거능은그릭요거트에열수추출물 0.5%, 에탄올추출물 0.5%, 열수추출물 1% 을첨가한순으로첨가하였을때높아지는경향을보여스테비아추출물을높은비율로첨가하였을때라디칼소거능도높아지는것을알수있 었다. 또한저장일수가길어질수록라디칼소거능이높아지는경향을보였고특히, 저장일수 15일차에에탄올로추출한스테비아추출물을그릭요거트에 1% 첨가하였을때 58.21±0.37% 로가장높았다 (Table 2). 이는추출물을첨가한양과희석배수를고려해보았을때매우높은라디칼소거활성으로스테비아잎추출물에는매우강한항산화력이있는것으로사료된다. 또한저장일수가늘어날수록 DPPH 라디칼소거능이증가하는경향을보였는데, 이는총폴리페놀함량이저장일수가지남에따라증가하기때문이라고사료된다 (Table 5). 2. ABTS + 라디칼소거능 ABTS + 라디칼항산화측정은 potassium persulfate 와반응시켜생성된 ABTS + 라디칼의소거능을이용해측정하는방법으로, ABTS + 라디칼이나타내는특유의청록색이 734 nm에서시료의항산화능이증가할수록흡광도가감소하는경향을나타낸다. 스테비아추출물을첨가한그릭요거트의 ABTS + 라디칼소거능을실험한결과, 대조군에비해스테비아잎추출물을첨가하였을때 ABTS + 라디칼소거능이증가하는것을확인할수있었고, 열수추출과에탄올추출모두에서 0.5% 첨가하였을때보다추출물을 1% 첨가하였을때더높은라디칼소거능을보여스테비아잎추출물에는항산화효과가있는것으로확인되었다 (Table 3). 또한, 같은농도의스테비아추출물을첨가하였을때를비교하면그릭요거트에열수추출물을첨가하였을때보다에탄올추출물을첨가하였을때더높은라디칼소거능을보여 DPPH 실험결과와유사한경향을보였다. 하지만 DPPH와다르게저장일수가지남에따른항산화력의증가는관찰되지않았다. Table 2. DPPH radical scavenging activity of the Greek yogurt added stevia extracts on during storage (Unit: %) Sample Storage (day) 0 5 10 15 Reference 4.66±0.83 ABd 4.01±0.33 Be 4.42±0.27 ABe 5.67±0.64 Ae Control 4.46±0.31 Ad 3.06±0.22 Be 4.19±0.36 Ae 3.99±0.24 Af GHW 0.5% 17.88±1.97 Bc 13.42±0.25 Cd 22.43±0.49 Ad 24.60±0.14 Ad GHW 1% 28.70±0.35 Cb 21.88±0.58 Dc 38.72±0.62 Bb 40.64±0.28 Ab GFE 0.5% 26.59±0.51 Db 28.37±0.25 Cb 32.56±0.36 Bc 34.71±0.37 Ac GFE 1% 31.63±0.83 Da 53.03±0.88 Ca 56.19±0.14 Ba 58.21±0.37 Aa Reference: Greek-style yogurt without sweetener, Control: Greek-style yogurt with oligosaccharide 0.5%, GHW 0.5%: Greek-style yogurt with HWE 0.5%, GHW 1%: Greek-style yogurt with HWE 1%, GFE 0.5%: Greek-style yogurt with FEE 0.5%, GFE 1%: Greek-style yogurt with FEE 1% Each value represents mean±s.d. (n=3) A~D Means with different storage days in the same row are different significantly at p<0.05. a~f Means with different treatment in the column are different significantly at p<0.05. 266 J. Milk Sci. Biotechnol. 2016;34(4):263-270
Antioxidant Activity of Yogurt with Stevia Table 3. ABTS radical scavenging activity of the Greek yogurt added stevia extracts on during storage (Unit: %) Sample Storage (day) 0 5 10 15 Reference 2.51±0.31 Ae 1.29±0.41 Bd 1.02±0.51 BC 0.89±0.64 Bd Control 2.33±0.27 Ae 1.11±0.08 Bd 0.97±0.45 BC 0.49±0.09 Bd GHW 0.5% 4.31±0.21 Ad 2.67±0.48 ABb 3.70±1.40 ABb 2.27±0.23 Bc GHW 1% 6.82±0.21 Ab 4.22±0.28 Bc 5.11±1.02 Bab 3.94±0.23 Bb GFE 0.5% 5.25±0.16 Ac 4.49±0.38 Bb 3.41±0.22 Cb 3.70±0.15 Cb GFE 1% 7.90±0.51 Aa 7.87±0.13 Aa 6.86±0.77 ABa 6.16±0.31 Ba Reference: Greek-style yogurt without sweetener, Control: Greek-style yogurt with oligosaccharide 0.5%, GHW 0.5%: Greek-style yogurt with HWE 0.5%, GHW 1%: Greek-style yogurt with HWE 1%, GFE 0.5%: Greek-style yogurt with FEE 0.5%, GFE 1%: Greek-style yogurt with FEE 1% Each value represents mean±s.d. (n=3) A~D Means with different storage days in the same row are different significantly at p<0.05. a~f Means with different treatment in the column are different significantly at p<0.05. 3. 환원력 (FRAP) 측정 FRAP 측정법은 DPPH 나 ABTS 처럼라디칼소거능을측정하는방법과는달리철이온을환원시키는능력을측정하는것으로환원력에따른시료의항산화능을측정할수있는방법이다. 본실험에서 FRAP 측정법에의해스테비아잎추출물을첨가한그릭요거트의환원력을측정한결과, control 에비해스테비아잎추출물을첨가하였을때환원력이유의적으로높게나타났다 (Table 4). 저장기간중 0, 10, 15일차에비해 5일차에서 GHW 0.5% 는 2.79±0.24, GHW 1% 는 3.96±0.31, GFE 0.5% 는 2.42±0.09, GFE 1% 는 3.58±0.16(GAE mg/ml) 으로가장높았고각처리구별로환원력을비교해보았을때스테비아잎을열수추출법으로추출한추출물을 1% 첨가한처리구가 0일차에서 3.45±0.03, 5일차에서 3.96± 0.31, 10일차에서 2.83±0.01, 15일차에서 2.97±0.05 GAE(mg/ ml) 로가장높았는데이것은 DPPH, ABTS, 총폴리페놀함량의실험결과와는다른경향으로 DPPH, ABTS의경우에는시료를제조할때메탄올과에탄올로희석하였지만 FRAP의경우, 증류수로희석했기때문에열수추출로추출된수용성항산화물질이더많이측정된것이라사료된다. 4. 총폴리페놀함량측정폴리페놀은식물에많이함유되어있는물질로식물이나식품이가지고있는페놀성화합물에서라디칼소거능과환원력이발생한다고알려져있다 (Kang et al, 1995). 스테비아에는 1,310 mg/100 g의다량의폴리페놀이함유되어있고특히, 잎에는 0.010 mg/ Table 4. FRAP activity of the Greek yogurt added stevia extracts on during storage (Unit: GAE mg/ml of sample) Sample Storage (day) 0 5 10 15 Reference 1.85±0.06 Ae 1.14±0.03 Cd 1.79±0.02 Ad 1.38±0.00 Be Control 1.62±0.04 Af 1.58±0.03 Ac 1.50±0.01 Be 1.39±0.01 Ce GHW 0.5% 2.45±0.04 Bc 2.79±0.24 Ab 2.16±0.00 Cc 2.10±0.01 Cc GHW 1% 3.45±0.03 Ba 3.96±0.31 Aa 2.83±0.01 Ca 2.97±0.05 Ca GFE 0.5% 2.11±0.01 Bd 2.42±0.09 Ab 1.45±0.03 Df 1.92±0.04 Cd GFE 1% 3.09±0.03 Bb 3.58±0.16 Aa 2.28±0.02 Db 2.82±0.00 Cb Reference: Greek-style yogurt without sweetener, Control: Greek-style yogurt with oligosaccharide 0.5%, GHW 0.5%: Greek-style yogurt with HWE 0.5%, GHW 1%: Greek-style yogurt with HWE 1%, GFE 0.5%: Greek-style yogurt with FEE 0.5%, GFE 1%: Greek-style yogurt with FEE 1% Each value represents mean±s.d. (n=3) A~D Means with different storage days in the same row are different significantly at p<0.05. a~f Means with different treatment in the column are different significantly at p<0.05. J. Milk Sci. Biotechnol. 2016;34(4):263-270 267
윤지우 김하나 하태준 박서희 이세미 안성일 주진우 김거유 Table 5. Total polyphenolic contents of the Greek yogurt added stevia extracts on during storage (Unit: GAE mg/ml of sample) Sample Storage (day) 0 5 10 15 Reference 1.35±0.05 ABe 1.30±0.03 Be 1.45±0.03 Ae 1.40±0.05 ABf Control 1.22±0.03 Cf 1.10±0.03 Df 1.43±0.03 Bf 1.54±0.03 Ae GHW 0.5% 2.59±0.00 Cd 2.55±0.03 Dd 3.08±0.00 Bd 3.17±0.00 Ad GHW 1% 4.48±0.03 Db 4.86±0.03 Cb 5.05±0.05 Bb 5.39±0.08 Ab GFE 0.5% 3.13±0.03 Dc 3.37±0.10 Cc 3.96±0.00 Bc 4.59±0.08 Ac GFE 1% 5.12±0.06 Ca 5.97±0.10 Aa 5.59±0.03 Ba 5.89±0.08 Aa Reference: Greek-style yogurt without sweetener, Control: Greek-style yogurt with oligosaccharide 0.5%, GHW 0.5%: Greek-style yogurt with HWE 0.5%, GHW 1%: Greek-style yogurt with HWE 1%, GFE 0.5%: Greek-style yogurt with FEE 0.5%, GFE 1%: Greek-style yogurt with FEE 1% Each value represents mean±s.d. (n=3) A~D Means with different storage days in the same row are different significantly at p<0.05. a~f Means with different treatment in the column are differentsignificantly at p<0.05. 100 g의 tannin 이함유되어있다고보고되기도하였다 (Yamamoto, 2001; Savita et al., 2004). 본실험에서도스테비아잎추출물을그릭요거트에첨가하였을때무첨가군보다높은페놀함량을나타내었고스테비아추출물을 0.5% 첨가하였을때보다 1% 의높은농도로첨가하였을때더높은폴리페놀을함유하고있는것으로보아스테비아잎추출물에는폴리페놀이함유되어있는것을알수있었다. 또한이는 DPPH와 ABTS 라디칼소거능과 FRAP의환원력을측정하였을때와유사한경향이며이로써스테비아를첨가한그릭요거트의항산화능은스테비아잎추출물에포함되어있는폴리페놀에의한것으로생각된다. 특히, 열수추출물을첨가하였을때보다에탄올추출물을첨가하였을때 0일차 5.12±0.06, 5일차 5.97±0.10, 10일차 5.59±0.03, 15일차 5.89±0.08 GAE(mg/ ml) 로더높은폴리페놀함량이있는것으로나타났는데이또한 DPPH와 ABTS와유사한경향이었으며이것은폴리페놀은 60~ 70 범위에서는추출수율이증가하지만그이상의온도에서는오히려함량이감소되었다는보고와유사하며, 본실험에서는 100 에서 6시간 3회추출하였으므로스테비아잎의열수추출물의폴리페놀함량이감소한것으로사료된다 (Kim et al., 2005; Cho et al., 2008). 또한본실험의총폴리페놀함량측정실험결과는폴리페놀은열수추출법보다에탄올추출법에서더높은농도로추출된다는연구보고와도유사한경향을보이는것을확인할수있었다 (Kim et al., 2013). 따라서스테비아잎추출물을그릭요거트에첨가하였을때의폴리페놀에의한항산화효과를보았을때스테비아잎추출물을추출할때는열수추출법보다에탄올추출법이더항산화기능성에효과적이라사료된다. 요약 본연구는열수추출과에탄올추출법으로추출한스테비아추출물을그릭요거트에당으로 0.5%, 1% 비율로첨가하여 DPPH, ABTS 라디칼소거능과 FRAP 측정법을통해환원력을측정하여항산화능을비교하고총폴리페놀함량을측정하기위하여수행되었다. 대조군에비해스테비아잎추출물을첨가하였을때항산화능이증가하였고열수추출물보다에탄올추출물을첨가하였을때더항산화능이증가하는경향을보였으며, 총폴리페놀함량또한증가하는경향을보였다. 따라서그릭요거트에스테비아잎추출물을첨가하여항산화기능성이함유된발효유로서에탄올추출법이효과적이라사료된다. 감사의말 본연구는한국연구재단지역혁신창의인력양성사업 ( 과제번호. 2015 H1C1A1035886) 에의하여이루어졌습니다. References 1. Benzie, I. F. F. and Strain, J. J. 1996. The ferric reducing ability of plasma (FRAP) as a measure of "antioxidant power": The FRAP assay. Anal. Biochem. 230:70-79. 2. Blois, M. S. 1958. Antioxidant activity determination by the use of a stable free radical. Nature 181:1199-1200. 268 J. Milk Sci. Biotechnol. 2016;34(4):263-270
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