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1 Korean J Food Cook Sci Vol. 33, No. 2, pp. 148~154 (2017) pissn eissn 냉동방법에따른떡의품질특성변화 이혜진 구수경 최희돈 박종대 성정민 김영붕 최현욱 최윤상 한국식품연구원식품가공기술연구센터 Quality Characteristics of Korean Rice Cake by Freezing Methods Hye-Jin Lee Su-Kyung Ku Hee-Don Choi Jong-Dae Park Jung-Min Sung Young-Boong Kim Hyun-Wook Choi Yun-Sang Choi Food Processing Research Center, Korean Food Research Institute, Seongnam 13539, Korea Abstract Purpose: Frozen Korean traditional rice cakes ( and ) were evaluated different conditions (-20 C and -10 C) freezing (magnetic resonance quick freezing and air blast freezing) to study differences in quality characteristics. Methods: Experiments analyze Korean rice cakes for water content, water activity, color, textural properties, and sensory characteristics. Results: Moisture content showed high value at -20 C freezing regardless of freezing method. Water activity was higher at -20 C than -10 C, and water activity higher magnetic resonance quick freezing than air blast freezing. The lightness values were higher -20 C freezing temperature compare to -10 C freezing temperature. Hardness and chewiness were the lowest -20 C magnetic resonance quick freezing. sensory evaluation both and showed better overall acceptability at -20 C magnetic resonance quick freezing. Conclusion: Therefore, the -20 C magnetic resonance quick freezing method resulted in favorable textural properties and sensory characteristics. Key words:,, magnetic resonance quick freezing, air blast freezing, textural properties Ⅰ. 서론 떡은가장오래된전통식품의한종류로형태및조리법이다양하고약 190 여종이있다고알려져있는의례식품이다 (Lee CH & Maeng YS 1987, Yim KY & Kim SH 1988). 제조하는방법에따라찐떡, 친떡, 지진떡, 삶은떡으로구분되어진다. 찐떡으로는설기떡, 백설기, 송편, 약식과기주떡등이있고, 친떡으로는가래떡, 개피떡, 인절미, 단자등이있다. 또한지진떡으로는화전, 부꾸미, 주악등이있으며, 삶은떡으로는경단등이있다 (Lee CH & Maeng YS 1987). 가래떡은멥쌀가루에물을내려찐다음절구나안반에놓고끈기가나도록쳐서둥글고길게만든떡으로예로부터엄숙함과청결함을의미하는뜻에서설날에떡국으로이용되어왔으며대중에게는인지도가가장높은떡이다 (Kang HJ 등 2012, Byun JI 2014). 설기떡은물을내리고체에쳐서적당한수분과공기를혼입하여균질화한다음시루에사뿐히안쳐찌는떡이다. 설기떡은멥쌀가루만을사용하여만든백설기와다양한부재료를첨가하여만든콩설기, 쑥설기, 호박설기등다양하게만들수있다. 떡제조시다양한부재료의사용은부족한영양소를보완할수있어영양학적으로우수한식품일뿐만아니라재료로부터오는색깔및형태도다양하여기호성이우수한식품이다 (Park HY 등 2008). 다양한떡은우리식생활문화에서큰부분을차지하고있으며, 웰빙과전통식품으로서의떡이재조명되고있다 (Yoon SJ & Oh IS 2014). 그러나떡은제조후시간이지남에따른노화현상으로인해쉽게굳어져떡의품질및상품성이저하되고이에따른떡의유통및판매등의성장저해를가져온다 (Kim DH 1992). 이에따라식미적기호도가급격히떨어지므로저장수명 Corresponding author: Yun-Sang Choi, Food Processing Research Center, Korea Food Research Institute, , Anyangpanagyo-ro, Bundang-gu, Sungnam-si, Gyeonggi 13539, Korea ORCID: Tel: , Fax: , kcys0517@kfri.re.kr Korean Society of Food and Cookery Science This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( nses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

2 Korean J Food Cook Sci 전기자장냉동에따른떡의품질변화 149 이짧은문제점을갖고있다 (Lee HK 등 2010). 떡의주재료인쌀은대부분이전분으로구성되어있으며, 쌀전분은아밀로오스및아밀로펙틴으로이루어져있다. 전분을충분한수분과함께호화온도이상으로가열하면전분입자가물을흡수하여팽윤 (swelling) 이일어난다. 이때전분은점성이증가하고선형고분자인 amylose 가전분입자로부터빠져나와구조가파괴되며호화가일어난다 (Wootton M & Bamunuarachchi A 1980). 호화상태의전분이저장기간중에너지가낮은상태로돌아가전분분자간에수소결합이형성되어재결정화가일어나경도가증가하고 syneresis 가생기는노화현상이발생하여전분을함유한식품의조직감, 소화율및기호도에영향을준다 (Kum JS 등 1996). 떡에관련된연구로는당류첨가 (Baker LA & Rayas-Duarte P 1998, Kim SS & Chung HY 2007a), 식이섬유첨가 (Kang KJ 등 1997), 유화제첨가 (Mun SH 등 1996, Kim SS & Chung HY 2007b), 효소첨가 (Song JC & Park HJ 2003) 및천연물질첨가 (Jung KM & An HJ 2012) 등으로대부분첨가물에의한떡의노화억제연구가대부분이다. 식품에서의냉동은열을제거하여식품내의수분을액상에서고상으로상변화시키는방법으로장기보존시우수한방법중하나이다 (Kim YB 등 2013). 냉기에유속을주어공기와시료간에열전달계수를크게작용하여냉동시키는방법을송풍식냉동법 (air blast freezing) 이라하며산업적으로활용도가높은방법이다 (Li B & Sun DW 2002). 자장에서에너지를부가하여물분자를진동시켜수분의빙결정화를억제하여냉동하는방법을전기자장냉동법 (magnetic resonance quick freezing) 이라한다. 이러한전기자장냉동법은피냉동물내 외부를동시에냉동하므로식품의냉동시물분자의이동이없기때문에세포조직의파괴가거의일어나지않도록하는방법이다 (Iwasaka M 등 2011). 전통식품인떡을인식의전환으로쉽고간편하게이용할수있게되었고이에따라새로운떡개발을통한상품의다양화가필요한시점이다. 떡의다양화및수요에맞춰품질유지를위한저장방법모색이필요하나냉동방법을활용한떡연구는아직미비한실정이다. 따라서본연구에서는냉동조건에따른떡의품질특성변화를평가하여떡류의효과적인저장방법에대한기초자료로활용하고자하였다. Ⅱ. 재료및방법 1. 공시재료및떡의제조설기떡은 Kim KS(1987) 의제조방법으로설기떡을제조하였고, 가래떡은 Park YK 등 (2011) 의제조방법으로가래 떡을제조하였다. 본실험에서사용한설기떡의제조는멥쌀 ( 추청 ) 을 3 회수세하여 3 시간침수후 30 분간체에밭쳐물기를제거한다음분쇄기 (JL-1000, Hibell, Hwaseong, Korea) 를이용하여분쇄하였다. 분쇄한쌀가루는 20 mesh 체에내린후떡제조에사용하였다. 1% 의천일염을첨가하여물내리기후설탕을첨가하여 20 분간찐후, 불을끈상태에서 10 분간뜸을들였다. 가래떡의제조는쌀가루에물내리기후 20 분간찐후, 불을끈상태에서 10 분간뜸을들였다. 찐떡반죽을사출기로사출시켜가래떡을제조하였다. 제조된설기떡과가래떡은 2 시간방냉후 0.2 mm PE film 으로포장하였다. 냉동전제조된설기떡의수분함량 47.52%, 수분활성도 0.998, 색도 (L, a, b) 가 87.27, -0.97, 8.55 로나타났다. 가래떡은수분함량 48.52%, 수분활성도 0.999, 색도 (L, a, b) 는 71.85, -1.72, 5.95 로측정되었다. 방냉후전기자장 -20 C 및 -10 C 냉동고 (KBL- 126DY-4D, Panasonic, Osaka, Japan) 와송풍식 -20 C 및 -10 C 냉동고 (LD-1143R, Lassele, Ansan, Korea) 에 7 일간냉동보관후실험재료로사용하였다. 냉동고에보관된떡은전자레인지 (RE-551B, 2450MHz, Samsung, Suwon, Korea) 를이용하여마이크로파해동 (700 W) 하여 1 시간실온방냉후이화학적및관능적품질특성평가를수행하였다. 2. 분석항목및실험방법본실험은떡을 3회제조하여 7일간냉동후각각실험항목별로 3회이상반복실험하여그평균치를구하였고, 각각의실험항목별로유의성검증을확인하여조사하였다. 1) 수분함량측정수분함량은 AOAC 법 (AOAC 2000) 에따라시료 1 g 을취하여 105 C 상압건조법 (SW-90D, Sang Woo Scientific Co., Bucheon, Korea) 으로분석하였다. 2) 수분활성도 (a w ) 측정시료를절단한후측정용원형 disc 에넣어수분활성도측정기 (Novasina, Labmaster-aw, Lachen, Switzerland) 를이용하여측정하였다. 3) 색도측정시료표면을 colorimeter(cr-210, Minolta, Osaka, Japan) 를사용하여명도 (lightness) 를나타내는 CIE L 값, 적색도 (redness) 를나타내는 CIE a 값과황색도 (yellowness) 를나타내는 CIE b 값을각각 3 회측정하였다 (illuminant C). 이때의표준색은 L 값이 97.83, a 값이 -0.43, b 값이 인 calibration plate 를표준으로사용하였다 ; 33(2):

3 150 이혜진등 Korean J Food Cook Sci 4) 물성측정시료를일정한크기로절단한후 texture analyzer(ta- XT2i, Stable Micro Systems Ltd., Surrey, England) 를이용하여물성을측정하였다. 일정한두께의시료를 plate 중앙에평행하게올려놓고 two-bite compression test 를이용하고분석계산하여경도 (hardness, kg), 점착성 (adhesiveness), 탄력성 (springiness), 응집성 (cohesiveness) 및씹힘성 (chewiness, kg) 등을구하였다. 이때의분석조건은 maximum load 2 kg, head speed 2.0 mm/sec, probe(φ20 mm cylinder probe), distance 40% 8.0 mm, force 5 g 으로설정하였다. 5) 관능검사관능적품질특성은 15 명의패널요원을선발하여시료에대한충분한지식과용어, 평가기준등을훈련시킨후평가를실시하였다 (Kim SI 등 1993). 평가대상인떡은 cm 의크기로제공하였다. 기호도조사평가항목은외관, 촉촉함, 맛, 조직감및전체적인기호도에대하여기호도조사를하였다. 차이식별조사항목은촉촉함및조직감에대한강도로모든항목은 9 점척도법에의해평균치를구하여비교하였다. 이때정도및강도에관한항목은 1 점 = 매우건조하다및단단하다, 9 점 = 매우촉촉하다및부드럽다 이며기호도에관한항목은 1 점 = 매우나쁘다, 9 점 = 매우좋다 로설정하여관능검사를실시하였다. 6) 통계분석본실험은떡을각각실험항목별로 3 회이상반복실험하여그평균치를구하였고, 각각의실험항목별로유의성검증을확인하여조사하였다. 통계분석은 SAS Program(ver. 9.12, SAS Institute Inc., Cary, NC, USA) 의 GLM(general linear model) procedure 를통하여분석하였고, 처리구간의평균간비교는 Duncan 의다중검정을통하여유의성검정 (p<0.05) 을실시하였다. Ⅲ. 결과및고찰 1. 냉동방법에따른떡의수분함량및수분활성도비교냉동방법에따른떡의수분함량및수분활성도측정결과는 Table 1에나타내었다. 설기떡의수분함량은 % 로유의적인차이는보이지않았으나, 냉동온도에따라 -20 C에비해 -10 C 냉동시수분함량이낮은경향을보였다. 가래떡의경우 -10 C 전기자장냉동시유의적으로가장낮은수분함량을보였다 (p<0.05). 수분함량은전기자장냉동및송풍식냉동법에의한차이는없었으나온도에따라 -20 C 냉동시떡의수분감소를지연시킬수있을것으로판단되었다. Park YM(2014) 의연구에따르면인절미의경우저장기간이경과할수록수분함량이감소하는경향을보였다. Koh BK(1999) 의설기떡의저장방법에따른연구에서는실온저장에비해냉동한떡의수분함량의변화가적은것으로나타났다. 전분겔의저장중수분은 plasticizer로서작용하여수분함량이높으면유리전이온도를낮추므로재결정화가일어나는온도를더낮출수있으므로수분함량이저장온도에따른노화를결정하는데중요한요인이된다 (Biliaderis C 1990). 그러므로본연구에서냉동저장이떡의수분함량유지에효과적이며특히냉동온도가낮을수록수분함량유지에효과적으로나타났다. 이는떡의저장중품질유지에중요한요인으로작용하는것을알수있었다. 수분활성도 (aw) 측정결과설기떡은 의범위로저장온도에따라 -20 C 냉동시유의적으로높은수분활성도를보였다 (p<0.05)(table 1). 냉동방법에따라송풍식냉동법에비해전기자장냉동법을이용시수분활성도가높은경향을나타냈다. 가래떡의수분활성도는 의범위로모든처리구간의유의적인차이를보이지않았으나 -20 C 전기자장냉동법을이용시수분활성도가가장높게나타났다. Kim MY & Chun SS(2009) 의연구에따르면호밀-밀혼합빵의수분활성도와조직감 Table 1. Change in the moisture contents (%) and water activity (a w) of Korean rice cakes ( and ) according to freezing conditions Moisture contents (%) 46.96± ± ± ±0.03 a w 0.997±0.001 A 0.986±0.003 B 0.995±0.002 A 0.988±0.001 B Moisture contents (%) 48.30±0.12 A 47.63±0.31 B 48.51±0.23 A 48.79±0.31 A a w 0.996± ± ± ± ; 33(2):

4 Korean J Food Cook Sci 전기자장냉동에따른떡의품질변화 151 이부의상관관계를나타내는것으로보고된바있다. 따라서전기자장냉동방법의수분활성도가높게유지되어냉동전의떡과가장유사하게촉촉함을유지하는데효과적일것으로판단되었다. 2. 냉동방법에따른떡의색도비교 Table 2는냉동방법에따른떡의표면색도측정결과를나타내었다. 설기떡은 -10 C 냉동에비해 -20 C 냉동시명도가높은경향을보였으나냉동방법에따른경향성은보이지않았다. 설기떡적색도의경우 -10 C 전기자장냉동시 -0.86으로가장높은적색도를보였다. 설기떡의황색도는명도와반대의경향으로 -10 C 냉동시 9.68 및 9.87로 -20 C에비해유의적으로높은수치으로나타났다 (p<0.05). 가래떡은 -20 C 전기자장냉동시 71.25로가장높은명도수치를보였다 (p<0.05). 가래떡의적색도는냉동온도에따라 -10 C 냉동시높게나타났고냉동방법에따라전기자장냉동법이용시송풍식냉동법에비해높은적색도를보였다. 가래떡의황색도에서는냉동온도에따른경향성은보이지않았으나냉동방법에따라전기자장냉동법이 로송풍식냉동법 보다높은수치를나타내었다. Kim BW 등 (2005) 은설기떡을 20 C에서 36시간저장하였을때명도는차이가크게나타나지않았고적색도와황색도는감소하는경향을보고하였다. Lee JW 등 (2013) 은 4 C에서 3일간냉장저장한가래떡은저장전의가래떡에비해명도의감소, 적색도의증가및황색도의감소가유의적인차이를보였다. Lee CH 등 (1995) 은냉동저장유무에따라조리한가래떡의색도를측정하였을때냉동저장후조리한가래떡은냉동저장없이조리한가래떡과비교하여낮은명도를나타내었다. Park YM(2014) 의연구에의하면인절미의경우냉동저장 1일후명도와황색도는각각 72.95에서 72.00, 14.19에서 13.75로낮아지고적색도는 -3.56에 서 로높아지는경향을나타났다. 이를통해냉장및냉동보관, 저장기간에의해색도변화에영향을주는것을알수있었다. 본연구에서냉동전명도, 적색도및황색도와비교하여냉동온도가낮은 -20 C 에서변화가덜일어난것을알수있었다. 따라서색도의변화는온도에의한영향으로냉동저장시떡을저장할경우저장온도가낮을수록품질유지에더욱효과적일것으로판단되었다. 3. 냉동방법에따른떡의물성특성비교냉동방법에따른떡의물성특성으로는경도, 점착성, 탄력성, 응집성및씹힘성을측정하였으며결과는 Table 3에나타내었다. 설기떡의경우모든항목에서유의적인차이를보이지않았으나냉동방법에따른경향성을나타내었다. 경도측정결과 -20 C 전기자장냉동시설기떡의경도가가장낮게측정되었다. 냉동온도에따라 -20 C 냉동시 -10 C 조건에비해낮은경도값을나타냈으며냉동방법에따라전기자장냉동법이송풍식냉동법보다낮게나타났다. 씹힘성의경우 -20 C 전기자장냉동시가장낮게측정되었다. 가래떡의경우냉동방법에따라유의적인물성의차이를보였다. 경도 0.81 kg, 탄력성 0.91 및씹힘성 0.67 kg으로 -20 C 전기자장냉동한가래떡이유의적으로가장낮은것으로나타났다 (p<0.05). 한편, Kim BW 등 (2005) 과 Lee JW 등 (2013) 의연구에서설기떡과가래떡의경도, 씹힘성및점착성이저장기간경과에따라증가하는것으로나타났다. Park YM(2014) 의연구결과, 인절미냉동저장 1일경과후경도가유의적인증가를보였고점착성과검성도증가하는경향을보였으며이러한결과는노화에의한영향으로보고한바있다. 따라서본연구결과냉동에의해떡의품질이저하되지만냉동조건에따라품질저하를지연시킬수있으며냉동온도가낮을수록, 전기자장냉동조건에의한 Table 2. Change in color values of Korean rice cakes ( and ) according to freezing conditions L-value 85.66±0.69 AB 84.29±2.42 B 86.42±0.51 A 84.09±0.18 B a-value -0.94±0.02 B -0.86±0.11 A -0.94±0.04 B -0.94±0.01 B b-value 9.14±0.22 B 9.68±0.65 A 9.14±0.43 B 9.87±0.07 A L-value 71.25±1.15 A 70.70±0.81 AB 71.00±1.05 AB 69.78±0.92 B a-value 0.63±0.16 A 0.85±0.08 A 0.53±0.12 B 0.78±0.29 A b-value 5.17± ± ± ± ; 33(2):

5 152 이혜진등 Korean J Food Cook Sci Table 3. Change in texture properties of Korean rice cakes ( and ) according to freezing conditions Hardness (kg) 0.59± ± ± ±0.18 Adhesiveness ± ± ± ± Springiness 0.93± ± ± ±0.02 Cohesiveness 0.82± ± ± ±0.02 Chewiness (kg) 0.45± ± ± ±0.13 Hardness (kg) 0.81±0.04 B 1.19±0.13 A 1.14±0.17 A 1.12±0.05 A Adhesiveness ± ± ± ±79.24 Springiness 0.91±0.02 B 0.92±0.01 B 0.93±0.02 AB 0.95±0.01 A Cohesiveness 0.92± ± ± ±0.01 Chewiness (kg) 0.67±0.03 B 1.00±0.11 A 0.97±0.13 A 0.96±0.04 A Table 4. Change in sensory characteristics of Korean rice cakes ( and ) according to freezing conditions Apparence 7.89± ± ± ±0.53 Moistness 7.89±0.78 A 7.22±0.44 B 7.89±0.78 A 7.22±0.44 B Taste 8.44±0.53 A 7.44±0.53 B 7.67±0.71 B 7.44±0.53 B Tenderness 8.22±0.44 A 7.78±0.44 AB 7.67±0.50 B 7.67±0.50 B Overall acceptability 8.33±0.71 A 7.67±0.50 B 7.89±0.60 AB 7.56±0.53 B Moistness (degree) 7.67±0.50 AB 7.33±0.71 AB 7.78±0.44 A 7.11±0.60 B Tenderness (degree) 8.11± ± ± ±0.50 Apparence 8.33±0.50 A 8.00±0.50 AB 7.67±0.50 B 7.56±0.53 B Moistness 7.78± ± ± ±0.50 Taste 8.33±0.50 A 7.67±0.50 B 7.67±0.50 B 7.89±0.60 B Tenderness 8.22±0.67 A 7.78±0.44 AB 7.67±0.71 AB 7.89±0.33 B Overall acceptability 8.33±0.50 A 7.67±0.50 B 7.56±0.53 B 7.44±0.53 B Moistness (degree) 7.89±0.33 A 7.67±0.50 AB 7.56±0.53 AB 7.67±0.50 B Tenderness (degree) 7.89± ± ± ±0.53 떡노화지연에효과적일것으로판단되어진다. 4. 냉동방법에따른떡의관능적특성비교 Table 4 는냉동방법에따른떡의관능적특성을기호도조사를통해분석한결과이다. 설기떡은냉동방법및온도에따른외관및조직감에대한기호적차이는없는것으로나타났다. 전반적인기호도에서는 -20 C 전기자장냉동 한설기떡이가장높은기호도를보였다. 촉촉함은강도및기호도평가하였으며촉촉함의강도는냉동방법에따른차이를보이지않았으나냉동온도에따라 -20 C 에서냉동한떡이가장촉촉한것으로평가되었다. 촉촉함에대한기호도에서는촉촉함의강도가높게평가될수록기호도또한높은것으로나타났다 (p<0.05). 조직감도강도및기호도를평가하였으며강도평가결과유의적차이를보 2017; 33(2):

6 Korean J Food Cook Sci 전기자장냉동에따른떡의품질변화 153 이지않았으나기호도에서는 -20 C 전기자장냉동한설기떡이가장높은기호도로평가되었다 (p<0.05). 가래떡은외관에서냉동온도가낮을수록, 냉동방법에따라전기자장냉동법이용시기호도가높은것으로나타났다 (p<0.05). 맛에대한기호도의경우 -20 C 전기자장냉동한가래떡이유의적으로가장높은기호도를보였다. 냉동한가래떡의전반적인기호도는 -20 C 전기자장냉동시다른처리구 ( 점 ) 에비해유의적으로가장높은기호를보였다. 촉촉함은강도및기호도에대한평가를하였으며냉동방법및냉동온도에따른강도및기호도모두유의적차이를보이지않았다. 조직감강도의경우처리구별차이는없었으나기호도의경우 -20 C 전기자장냉동법이 8.22 점으로가장높은기호도를보인반면 -10 C 송풍식냉동법은유의적으로가장낮은기호를나타내었다 (p<0.05). 따라서떡의경우냉동저장시품질유지를위해온도가낮은 -20 C 가가장우수하였으며냉동방법에따라전기자장냉동법이우수한것으로판단되었다. Ⅳ. 요약및결론 본연구에서는냉동방법 ( 전기자장식냉동및송풍식냉동 ) 의조건 (-20 C 및 -10 C) 을달리한냉동떡의품질특성차이를평가하였다. 수분함량은냉동방법에관계없이 -20 C 냉동시높은수분함량을나타냈으며수분활성도의경우냉동온도가낮을수록높았으며, 송풍식냉동에비해전기자장식냉동법으로냉동할경우높은활성도를보였다. 물성측정결과는설기떡과가래떡모두경도및씹힘성이 -20 C 전기자장냉동법을이용하였을때가장낮은수치를나타내었다. 관능적특성검사에서는 -20 C 전기자장냉동한떡에대한기호도가가장좋은것으로평가되었다. 따라서, 낮은온도의전기자장냉동법이물리적및관능적품질특성에있어서가장효과적인떡의냉동저장방법으로판단되었다. Conflict of Interest No potential conflict of interest relevant to this article was reported. Acknowledgments This research was supported by Main Research Program (E ) of the Korea Food Research Institute (KFRI) funded by the Ministry of Science, ICT & Future Planning (Republic of Korea). This research was also partially supported High Value-added Food Technology Development Program ( ) by the Ministry of Agricul- ture, Food and Rural Affairs (Republic of Korea). References AOAC Official methods of analysis. 17th ed. Association of Official Analytical Chemists. Washington DC, USA. pp Baker LA, Rayas-Duarte P Retrogradation of amaranth starch at different storage temperature and the effect of salt and sugars. Cereal Chem 75(3): Biliaderis C Thermal analysis of food carbohydrates. pp In: Thermal analysis of foods. Harwalkar VR, Ma CY (eds.). Elsevier Applied Science Publishers, Barking, UK. Byun JI Effect of casein and agar on quality characteristic depending on cold storage period of Topokki garaedduk. Keimyung University, Deagu, Korea. p 3. Iwasaka M, Onishi M, Kurita S, Owada N Effects of pulsed magnetic fields on the light scattering property of the freezing process of aqueous solutions. J Appl Phys 109(7):07E Jung KM, An HJ Effects of oyster mushroom on quality of Sulgidduk and Gyeongdan. J Korean Soc Food Sci Nutr 41(9): Kang HJ, Lee JK, Lim JK Quality characteristics of Topokki garaedduk with different moisture ratios. J Korean Soc Food Sci Nutr 41(4): Kang KJ, Kim K, Lee SK, Kim SK Relationship between molecular structure of acid hydrolyzed rice starch and retrogradation. Korean J Food Sci Technol 29(5): Kim BW, Yoon SJ, Jang MS Effects of addition Baekbokryung (White Poria cocos Wolf) powder on the quality characteristics of Sulgidduk. Korean J Food Cook Sci 21(6): Kim DH Sikpumhwahak [Food chemistry]. Tamgudang, Seoul, Korea. pp Kim KS Scientific study for the standardization of the preparation methods for Paeksolgi (I). J Korean Home Econ Assoc 25(2): Kim MY, Chun SS Changes in shelf-life, water activity, and texture of rye-wheat mixed bread with naturally fermented raisin extract and rye sourdough during storage. Korean J Food Cook Sci 25(2): Kim SI, An MJ, Han YS, Pyeun JH Sensory and instrumental texture properties of rice cakes according to the addition of Songpy (pine tree endodermis) or Mosipul (China grass leave). J Korean Soc Food Nutr 22(5): Kim SS, Chung HY. 2007a. Effects of carbohydrate materials on retarding retrogradation of a Korean rice cake (Karedduk). J Korean Soc Food Sci Nutr 36(10): Kim SS, Chung HY. 2007b. The texture and descriptive sensory ; 33(2):

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386-390.hwp 386 HANYANG MEDICAL REVIEWS Vol. 29 No. 4, 2009 우리나라 미숙아의 통계와 의료비용 Statistics and Medical Cost of Preterm in Korea 윤혜선 을지대학교 노원을지병원 소아청소년과학교실 Hye Sun Yoon, M.D., Ph.D., Department of Pediatrics, Nowon