추출 조건에 따른 더치커피(Dutch coffee)의 이화학적, 관능적 특성 및 저장 중 특성 변화 연구

Abstract

This study was designed to investigate the changes on antioxidant activities as well as physicochemical and sensory characteristics of Dutch coffee(cold brew) depending on different extraction conditions and storage during 8 weeks. Dutch coffee was extracted from ground coffee soaked in water of 4°C and 20°C using exclusive instrument. The higher extraction temperature(temp.) was, the higher acidity, solid content, total phenolic content, and antioxidant activities were observed. Dutch coffee extracted with slower extraction rate showed higher values above mentioned, but not significant. Chlorogenic acid(CGA), quinic acid(QA), and caffeine content showed positively and negatively related to extraction temp. and extraction rate respectively. On the other hand, total peak areas of volatile compounds collected by headspace were contrary to other parameters. The extraction conditions, especially extraction rate, did not affect on sensory characteristics. Compared to drip coffee, Dutch coffee had low intensity of following 8 kinds of attributes: bitter flavor, winery flavor, greasy taste, bitter taste, burnt taste, oily, unpleasant-tasting, and duration of aftertaste, which caused Dutch coffee milder and less oily. During storage, the decline of pH and increase of acidity were more affected by storage temperature than extraction temp. Brown color and total phenolic content, were different from fresh Dutch coffee, but not quite. ABTS and DPPH radical scavenging activity right after extraction increased as extraction temp. was high, and DPPH radical scavenging activity increased after 2-week. As storage time prolonged, caffeine content decreased by about 10% at 20°C. The increase of caffeic acid and quinic acid content was caused by hydrolysis of CGA, and CGA content also increased at 20℃ due to the hydrolysis of CGA lactone. All samples were found that there were general bacteria less than 1 CFU/mL, which means it is safe to store and drink Dutch coffee within 8 weeks.