การเปรียบเทียบองค์ประกอบของสารตั้งต้นของสารให้กลิ่นรสของกาแฟพันธุ์อะราบิกาและผลของการคั่วต่อคุณภาพทางเคมีกายภาพ และทางประสาทสัมผัสของกาแฟ

Abstract

This research aimed to compare flavor precursors of Arabica coffee and to study the effect of roasting processes on the physical, chemical, and sensory properties of coffee. The flavor precursors of six coffee samples, (1) Omkoi organic, (2) Khun Chang Khian, (3) Doi Chang, (4) Doi Chang peaberry, (5) Pha Tang, and (6) Khun Lao, harvested from Chiang Mai and Chiang Rai in the year 2017 and 2018 were analyzed. The investigated properties included moisture content, ash, protein, fat, carbohydrate, trigonelline, total phenolic, profiles of amino acids and fatty acid, and sugars of those coffee samples. It was found that Omkoi organic and Doi Chang coffee contained the highest contents of fructose, glucose, sucrose, amino acids, trigonelline, chlorogenic acid and caffeine. The effect of roasting processes on physical, chemical, and sensory properties were investigated. There were two types of coffee roasters used in this experiment, drum and infrared roasters. The experimental design of 2x2 Factorial with 2 center points were applied with two factors of temperature and time of roasting. Moisture content, weight loss, bulk density, color, total phenolic, trigonelline, caffeine, flavor profile, and sensory properties of Omkoi organic and Doi Chang coffee were analyzed. It was found that moisture contents and bulk density of coffee roasted using infrared roaster were lower than ones that roasted using drum roaster. Higher roasting temperature and time resulted in a darker color of coffee bean. The color homogeneity of coffee beans roasted by infrared roaster were better than the ones roasted by drum roaster. For both types of coffee roasters, total phenolic, trigonelline, and caffeine contents tended to decrease when increasing temperature and time of roasting. The profiles of volatile organic compounds of coffee roasted from both roasters were similar. There were 64 compounds identified, consisted of 4 pyridines, 11 pyrazines, 12 ketones, 4 pyrroles, 5 phenols, 3 aldehydes, 22 furans, and 3 organic acids. The compound presented in the highest quantity was 2-furan methanol. In addition to that 5-methy1-2-furancarboxaldehyde, 2-fiuranmethanol acetate, furfural and 1-(acetyloxy)-2-propanone were found to be the dominant volatiles. It can be stated that coffee roasted by drum roaster contained higher amounts of volatile compounds. The sensory evaluation of Omkoi organic and Doi Chang roasted coffee was carried out by Q-graders of Hillkoff Company Limited. Omkoi organic and Doi Chang coffee roasted at any conditions were categorized as good to very good groups with the marks about 80 points. Interestingly, Omkoi organic coffee roasted using infrared roaster at 155 C for 7 min and at 1 70 C for 6 min 30 second were categorized as excellent coffee. The remarkable flavor character of roasted coffee described by Q-graders were caramel, vanilla, honey, citrus, flower, milk, and butter.