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Effects of enzymatic modification of wheat protein on the formation of pyrazines and other volatile components through the Maillard reaction

Title
Effects of enzymatic modification of wheat protein on the formation of pyrazines and other volatile components through the Maillard reaction
Authors
이상언
Issue Date
2010
Department/Major
대학원 식품공학과
Publisher
이화여자대학교 대학원
Degree
Master
Advisors
김영석
Abstract
본 연구에서는 밀 단백질 가수분해물과 환원당 (reducing sugar)인 glucose, fructose, xylose의 가열반응 시 생성되는 휘발성 성분들의 형성에 미치는 영향요인에 대해 알아보고자 하였다. 밀 단백질을 protease/peptidase로 1차적으로 가수분해 시킨 후, 가수분해물 중 분자량 3,000 이하만 ultrafiltraation을 사용하여 얻었다. 그리고, 얻어진 가수분해물을 glutaminase로 처리하여 deamidation 시킴으로써 free ammonia와 deamidation된 밀 글루텐 가수분해물을 생성하였다. Deamidation의 정도를 고찰하기 위해, glutaminase 처리 전과 후의 glutamic acid와 ammonia의 양을 각각 측정하였다. Glutaminase 처리 후, glutamic acid의 양은 처리 전보다 13배 증가하였고, ammonia는 1.3배 증가하였다. Deamidation이 pyrazine 및 기타 휘발성 성분들의 형성에 미치는 영향을 고찰하기 위해 glutaminase 처리 한 가수분해물과 처리하지 않은 가수분해물을 각각 glucose와 180 ˚C에서 가열 반응하였고, 세 종류의 환원당에서 생성되는 휘발성 성분들을 비교하기 위하여 glucose, fructose, xylose를 각각 가열 반응시켰다. 또한 온도 (150 ˚C, 180 ˚C)의 영향을 고찰하기 위해 각 조건에서 가열 반응 후 생성된 휘발성 성분들을 비교하였다. 휘발성 성분들은 용매추출을 통해 추출되었으며, GC-MS를 이용하여 분석하였다. 이 결과, 다양한 pyrazines, furans, thiophenes, thiazoles, pyrrolizines 등이 동정되었다. Deamidation 처리 실험군에서는 총 34개의 pyrazine과 10개의 기타 nitrogen-containing compounds, 4개의 furan, 7개의 sulfur-containing compounds가 생성됨을 확인하였다. 반면에 deamidation 처리하지 않은 실험에서는 19개의 pyrazine, 6개의 기타 nitrogen-containing compounds, 2개의 furan, 5개의 sulfur-containing compounds가 생성됨을 확인하였다. 따라서 glutaminase 처리를 한 실험에서 정성 및 정량적으로 더 많은 휘발성 성분이 생성됨을 확인하였다. 세 가지 서로 다른 환원당의 가열반응에서 39개의 pyrazines, 11개의 기타 nitrogen-containing compounds, 12개의 furan, 8개의 sulfur-containing compounds가 생성됨을 확인하였다. 전체적으로 fructose의 반응생성 정도가 가장 높았고, xylose와의 반응에서 furan류가 많이 생성되었다. Furfural은 xylose 반응물에서만 동정되었다. 150 ˚C, 180 ˚C의 서로 다른 반응온도에서 가열반응 시 생성되는 volatile components는 반응온도가 높아짐에 따라 그 종류와 함량이 급격히 증가하는 경향을 보였다.;In this study, the formation of volatile components from the thermal interactions of wheat gluten hydrolysates with reducing sugars, such as glucose, fructose and xylose, was investigated. Wheat gluten was hydrolysed using protease/peptidase, and the resulting hydrolysates were fractionated by using ultrafiltration membranes with cut-offs of MW 3,000. Then the ultra-filtered hydrolysates were deamidated using glutaminase to produce free ammonia as well as deamidated wheat gluten hydrolysates. In order to evaluate the effect of deamidation, the amounts of both glutamic acid and ammonia were determined before and after treatment of glutaminase, respectively. After treatment with glutaminase, the relative amounts of glutamic acid and ammonia increased more than 13 times and 1.3 times compared to those of before treatment, respectively. The hydrolysates were then reacted with reducing sugars, such as glucose, fructose, or xylose at 150 ℃ or 180 ℃ and the volatile components generated were isolated and analyzed by GC-MS. The effects of deamidation, reducing sugars (glucose, fructose or xylose) and temperature (150 ℃ or 180 ℃) on the formation of volatile components were investigated and compared. The volatile components included diverse pyrazines, furans, thiophenes, thiazoles, and pyrrolizines. The volatile components obtained from the thermal reactions of enzymatically deamidated gluten hydrolysates with glucose at 180 ℃ for 90 min included 34 pyrazines, 10 other nitrogen-containing compounds, 4 furans, and 7 sulfur-containing compounds. In contrast, the thermal reactions of gluten hydrolysates untreated by glutaminase with glucose at 180 ℃ for 90 min produced 19 pyrazines, 6 nitrogen-containing compounds, 2 furans, and 5 sulfur-containing compounds. More volatile components were formed from deamidated gluten hydrolysates than untreated ones, qualitatively and quantitatively. When compared between reducing sugars, more volatiles were generated from the interaction of fructose with deamidated wheat gluten hydrolysates than the interaction of glucose. In particular, the contents of 2,5-dimethylpyrazine and 2,5-dimethyl-3-isopentylpyrazine increased up 4 times and 2.7 times in hydrolysates with fructose compared to those in hydrolysates with glucose, respectively. In the case of furans, the reaction of xylose with hydrolysates generated more various furan derivatives than that of glucose or fructose. Furfural was identified only in deamidated wheat gluten hydrolysates with xylose. The thermal reactions of deamidated wheat gluten with reducing sugars at 150 ℃ or 180 ℃ were also investigated. As the reaction temperature increased, volatile components significantly increased both in quantitative and qualitative.
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