Changes of volatile compounds in heated welsh onion (Allium fistulosum L.) during storage

Abstract

특유의 향을 가진 대파 (Allium fistulosum L.)는 일반적으로 다양한 식품의 풍미를 향상시키기 위해 사용된다. 그러나, 대파의 휘발성 화합물, 특히 황 함유 화합물은 가공 공정 및 보관 중에 상당히 변화될 수 있다. 본 연구는 대파의 가열에 의한 휘발성 화합물의 화학적 변화를 확인하였다. 또한 ascorbic acid와 glutathione과 같은 항산화제를 첨가하여 저장 기간 동안 항산화 효과를 조사하였다. 휘발성 화합물을 solid-phase microextraction (SPME)를 사용하여 추출하였고, 저장 기간 동안 휘발성 화합물의 변화는 gas chromatography-mass spectrometry (GC-MS)를 사용하여 분석하였다. 대파의 휘발성 향미 성분의 통계적 차이를 평가하기 위해 PCA, PLS-DA와 같은 다변량 통계 분석과 ANOVA와 같은 단변량 분석을 적용하였다. 대파를 가열한 후 (methyltrisulfanyl)methane, 1-(methyldisulfanyl)prop-1-ene, 2,5-dimethylthiophene, (Z)-1-methylsulfanylprop-1-ene, 1-[[(E)-prop-1-enyl]disulfanyl]propane(trans-propenyl propyl disulfide), 3-methylsulfanylprop-1-ene(allyl methyl sulfide) 과 같은 대부분의 황 함유 화합물은 상당히 증가하였다. 그러나 다른 향기성분 (E)-2-methylpent-2-enal, hexanal, propanal, 2-ethylhexan-1-ol은 가열 후 열분해에 의해 감소하였다. 또한 저장 기간이 진행됨에 따라, 대부분의 황 함유 화합물은 감소하였다. 그러나 일부 황 함유 화합물 propylene sulfide, methyl 1-(methylthio)propyl disulfide, 1-methyl-2-(3,5-dimethylthien-4-yl)disulfide, propyl (Z)-1-propenyl trisulfide, 3,5-dimethyl-2-(methylthio)-thiophene 등은 저장 기간 동안 고리 구조 화합물의 절단과 황 함유 화합물의 재배열에 의해 증가하였다. 반면에, 항산화제 첨가에 따른 대파의 휘발성 화합물의 변화 양상은 각 항산화제마다 다른 경향을 보였다. Ascorbic acid를 첨가한 대파에서는 첨가하지 않은 대파에 비해 산화된 화합물이 적게 확인되었다. 그러나, glutathione을 첨가한 대파에서는 휘발성 화합물의 손실을 보였으며 다른 유형의 휘발성 화합물이 생성되는 것으로 나타났다. 결론적으로 이 연구는 항산화제의 효과와 가열 및 저장 중 휘발성 화합물의 변화를 확인하였다. ;Welsh onion (Allium fistulosum L.) is usually used to enhance the flavor of various foods. However, the volatile compounds of welsh onion, especially sulfur-containing compounds, can be significantly changed during process and storage. This study investigated the changes of volatile compounds by heating. Also, antioxidants such as ascorbic acid and glutathione were added to investigate the antioxidant effect during storage period. Volatile compounds were extracted using solid-phase microextraction (SPME) and analyzed by using gas chromatography-mass spectrometry (GC-MS) to compare the changes in volatile compounds during storage. Multivariate data analyses such as PCA and PLS-DA, and univariate analysis such as ANOVA were applied to evaluate statistical differences in volatile compounds of welsh onion. After heating the welsh onion, most sulfur-containing compounds such as (methyltrisulfanyl)methane, 1-(methyldisulfanyl)prop-1-ene, 2,5-dimethylthiophene, (Z)-1-methylsulfanylprop-1-ene, 1-[[(E)-prop-1-enyl]disulfanyl]propane (trans-propenyl propyl disulfide), 3-methylsulfanylprop-1-ene (allyl methyl sulfide) significantly increased. However, other volatile compounds such as (E)-2-methylpent-2-enal, hexanal, propanal, 2-ethylhexan-1-ol, decreased by thermal decomposition after heating and involved in changing to other compounds. In addition, most sulfur-containing compounds decreased as the storage period progressed. However, some sulfur-containing compounds such as propylene sulfide, methyl 1-(methylthio)propyl disulfide, 1-methyl-2-(3,5-dimethylthien-4-yl)disulfide, propyl (Z)-1-propenyl trisulfide, 3,5-dimethyl-2-(methylthio)-thiophene increased, possibly, by cleavage of ring structure and rearrangement of sulfur-containing compounds during storage. On the other hand, the changes in volatile compounds of welsh onion samples with antioxidants showed a different tendency for each antioxidant. Less oxidized compounds were detected in welsh onion with ascorbic acid than without the addition of ascorbic acid. However, when glutathione was added to the welsh onion, volatile compounds was reduced. It was shown that different types of volatile compounds were formed compared to other samples. In conclusion, this study investigated antioxidant effects and changes of volatile compounds during heating and storage.