Effects of several additives on the formations of furan and other volatile components in canned coffee model systems

Abstract

The aim of the present study was to analyze the formation of furan and other volatiles using gas chromatography-mass spectrometry combined by solid phase micro-extraction after dicarbonyl trapping agents [epicatechin (EC), epigallocatechin gallate (EGCG), and catechin], water-soluble antioxidants (caffeic acid, ferulic acid, and chlorogenic acid), fat-soluble antioxidants [(α-tocopherol and butylated hydroxytoluene (BHT)], reducing agents (glutathione and sodium sulfite), and proteins (casein and isolated soy protein ) were added into canned coffee model systems. In the case of dicarbonyl trapping agents, there was a significant decrease in furan formation in the order of EC (65.3%), EGCG (60.0%), and catechin (44.7%). In addition, the formations of Maillard reaction products, including furan derivatives (furfural and 5-methylfurfural), Strecker aldehydes (2-methylbutanal), pyrazines (2,6-dimethylpyrazine), and lipid oxidation products, including hexanal and 2-pentylfuran, were suppressed by all the dicarbonyl trapping agents added. The addition of sodium sulfite and glutathione into coffee model systems could lead to a considerable furan reduction of 64.1% and 44.9%, respectively. The relative contents of sulfur-containing compounds, such as methanethiol, dimethyl disulfide, and thiophene increased in coffee model systems with the addition of glutathione, while Strecker aldehydes, such as 2-methylpropanal and 2-methylbutanal, furan derivatives, such as furfural and 5-methylfurfural, and lipid oxidation products decreased. Among water-soluble antioxidants, chlorogenic acid significantly decreased furan level by 67.0%, followed by ferulic acid (57.6%), trolox (50.1%) and caffeic acid (48.2%) in coffee. In addition, chlorogenic acid also reduced the formations of furfural and lipid oxidation products. However, the addition of caffeic acid, ferulic acid, and chlorogenic acid decreased the generation of key coffee aroma components, such as Strecker aldehydes (2-methylpropanal and 2-methylbutanal), 5-methylfurfural, and pyrazines (2,6-dimethylpyrazine and 2-ethyl-5-methylpyrazine). Among fat-soluble antioxidants, BHT and α-tocopherol decreased furan level by 49.3% and 39.3%, respectively, while β-carotene increased furan level by 34.8%. In addition, nitrogen gas purging in coffee model system reduced furan formation by 30% whereas proteins had less inhibitory activity on the formation of furan and other volatile compounds in coffee model systems. Furthermore, we demonstrated the effects of hydroxycinnamic acids such as cinnamic acid, p-coumaric acid, caffeic acid, and chlorogenic acid on the formations of furan and selected volatiles in coffee model systems containing dicarbonyls (glyoxal and methylglyoxal), reducing sugars (glucose and fructose), and/or amino acids (glycine and serine). In the case of coffee model systems containing dicarbonyls, sugars, and/or amino acids, glucose/serine coffee model system generated the highest level of furan, followed by glucose/glycine > serine > glycine > fructose > glyoxal (GO) > methylglyoxal (MGO) > glucose. In addition, the level of furan decreased by 19.3-31.1% and 23.0-28.6% in coffee model systems with GO and MGO, respectively, by caffeic acid and chlorogenic acid. Moreover, the formation of furan after the addition of sugars and/or amino acids reduced by hydroxycinnamic acids in the order of chlorogenic acid (30-60%) > caffeic acid (20-40%), p-coumaric acid (10-20%), cinnamic acid (10%) in different coffee model systems.;본 연구에서는 커피모델시스템에 dicarbonyl trapping agents [epicatechin (EC), epigallocatechin gallate (EGCG), catechin], 수용성 항산화제 (trolox, caffeic acid, ferulic acid, chlorogenic acid), 지용성 항산화제 (α-tocopherol, BHT), 환원제 (glutathione, sodium sulfite) 및 단백질 (casein, isolated soy protein)을 첨가한 후 120℃에서 10분 가열 반응 시 생성되는 퓨란, Maillard 반응 산물 및 지방산화물을 고체상미세추출법 (solid phase micro-extraction)으로 추출 후 가스크로마토그래피-질량분석기 (gas chromatography-mass spectrometry)를 이용하여 비교분석하였다. 커피모델시스템에서 퓨란의 함량은 EC, EGCG, catechin 첨가 시 각각 65.3%, 60.0%, 44.7%으로 유의적으로 감소하였다. 커피모델시스템에 dicarbonyl trapping agents을 첨가 시 Maillard 반응산물인 furan류 (furfural 와 5-methylfurfural), Strecker aldehyde류 (2-methylbutanal), pyrazine류 (2,6-dimethylpyrazine) 및 지방산화물 (hexanal 와 2-pentylfuran)이 감소하였다. 환원제인 glutathione 및 sodium sulfite 첨가 시에는 퓨란 함량이 각각 64.1% 및 44.9% 수준으로 감소하였다. 환원제 첨가 시 황이 함유된 성분들 (methanethiol, dimethyl disulfide, thiophene)은 증가하는 반면, Strecker aldehyde류 (2-methylpropanal, 2-methylbutanal), furan류 (furfural, 5-methylfurfural) 및 지방산화물들은 감소하였다. 수용성 항산화제인 chlorogenic acid, ferulic acid, trolox 및 caffeic acid 첨가 시 퓨란 함량이 각각 67.0%, 57.6%, 50.1%, 48.2% 정도 감소하였다. 또한 지용성 항산화제인 BHT 와 α-tocopherol 첨가 시 49.3% 및 39.3%로 감소하였으나, β-catrotene 첨가 시 오히려 34.8% 증가하였다. 질소 가스 충전에 의하여 퓨란 함량은 30% 감소하나, 단백질 첨가 시에는 퓨란 감소 효과가 거의 나타나지 않았다. 또한dicarbonyls (glyoxal, methylglyoxal), 환원당 (glucose, fructose), 아미노산 (glycine, serine)을 커피모델시스템 첨가 후 가열반응 시 퓨란, Maillard 반응 산물 및 지방산화물 생성에 미치는 hydroxycinnamic acids (cinnamic acid, p-coumaric acid, caffeic acid, chlorogenic acid) 의 영향을 고찰하였다. Dicarbonyls인 glyoxal, methylglyoxal을 함유한 커피모델시스템에서 caffeic acid 와 chlorogenic acid에 의하여 퓨란 함량이 각각19.3-31.1%, 23.0-28.6% 감소하였고, 환원당 및 아미노산 커피모델시스템에서 퓨란 함량은 chlorogenic acid에 의해 30-60%, caffeic acid에 의해 10-20%, p-coumaric acid에 의해 10-20%, cinnamic acid에 의해 10% 감소하였다.