쌀가루의 하이드록시프로필화 및 가교처리에 의한 절편의 저장성 향상

Abstract

This study was conducted to investigate the effects of a hydroxypropylation and cross- linking treatment on the characteristics of rice grit and Julpyun(traditional Korean plain rice cake). Rice grit was treated with propylene oxide(4%, 8% of rice grit weight, dwb, HP4 and HP8, respectively) with and without following treatment with phosphorus oxychloride(0.l% of rice grit weight, dwb, HP4-CL and HP8-CL, respectively). Various physicochemical properties of rice grits with and without modification were examined. Sensory and physical analysis were also performed on fresh and stored Julpyun, made with various modified rice grits. Nonwaxy (NWR) and waxy rice grits(WR) were used as controls. With modification, crude protein and lipid contents of modified rice grit were increased while crude ash content was decreased compared to NWR. HP was shown to take more water than NWR and this was more obvious with the higher substitution level. However, cross-linking resulted in less water uptake increased in HP. Apparent viscosity and yield stress values of modified rice grit were higher than NWR. And HP8, HP8-CL had lower values than HP4, HP4-CL. Amylographic measurement indicated that hydroxypropylation decreased the gelatinization temperature and setback. Increased peak viscosity and breakdown in HP were noted by hydroxypropylation but cross-linking in HP had adverse effect. In sensory evaluation, adhesiveness and cohesiveness were insreased while firmness of Julpyun was decreased by hydroxypropylation. This trend was less obvious when. hydroxypropylation was followed by cross-linking. As storage period was prolonged, increase in hardness was observed in all the Julpyun, especially in NWR Julpyun. Firming was delayed remarkably with hydroxypropylation at 8%. Cross-linking further slowed down the firming rate in HP Julpyun. It was concluded that hydroxypropylation on nonwaxy rice grit could decreased the firming rate in Julpyun, especially when cross-linking treatment was accompanied.;본 연구에서는 전분의 노화 억제 및 냉해동 안정성이 있다고 알려진 하이 드록시프로필화 및 가교처리의 화학적 변성 방법을 쌀가루에 직접 적용하여 이화학적 특성을 조사하고, 실제 식품에 적용되었을 때의 효과를 알아보고자 절편형 떡을 제조한 후, 관능검사에 의한 텍스처 특성과 저장기간에 따른 물리적 경도 변화를 알아보았다. 본 실험에서 얻어진 결과를 요약하면 다음과 같다. 1. 변성시의 처리 과정에 의해 변성 쌀가루의 조단백, 조지방 함량은 비변성 멥쌀가루보다 감소하였고 조회분 함량은 증가하였다. 2. 하이드록시프로필화는 쌀가루의 물 결합 능력을 현저히 증가시켰으나 하이드록시프로필화와 가교처리를 병행할 경우에는 같은 수준의 하이드록시프로필화 쌀가루보다 물 결합능력이 감소하는 경향을 보여주었다. 3. 전단속도 변화에 따른 점도 변화를 측정한 결과, 겉보기 점도와 항복력은 멥쌀, 하이드록시프로필화 8% 쌀가루, 하이드록시프로필화 4% 쌀가루, 하이드록시프로필화 8%-가교처리 쌀가루, 하이드록시프로필화 4%-가교처리 쌀가루, 참쌀가루 순으로 증가하는 것으로 나타났다. 4. 아밀로그램 측정 결과, 하이드록시프로필화 처리에 의해 호화개시온도 및 setback은 감소한 반면 최고점도와 breakdown은 증가하였다. 가교처리가 병행된 경우 이러한 경향을 완화시켰으며, 특히 setback은 크게 증가하였다. 5. 관능검사 결과, 하이드록시프로필화 쌀가루로 만든 절편 시료는 경도가 현저히 감소하였고 응집성 및 부착성이 증가한 반면 가교처리를 병행한 경우 이러한 경향이 감소하였다. 6. Instron에 의해 저장중의 경도 변화를 측정한 결과 저장기간이 길어짐에 따라 전반적으로 경도가 증가하였으나, 하이드록시프로필화 8% 처리에 의해 절편의 노화 진행이 현저히 지연되었으며, 가교처리를 병행할 경우 노화가 더욱 억제되었다. 이와 같이 굵은 쌀가루에 하이드록시프로필화 및 가교처리를 하였을 때 떡의 텍스처가 향상되었으며, 저장 중 노화가 억제되었다.