การศึกษาวิธีและสภาวะการอบแห้งสำหรับการผลิตผลิตภัณฑ์ชาจากดอกกาแฟโรบัสต้า (Coffea canephora)

Abstract

The optimal conditions for drying Robusta coflee flower using different methods and conditions (hot air drying (HD) at 50 60 70 and 80°C, drying time was 8 6 4 and 2 hours. respectively; infrared vacuum drying (IVD) at 50°C (50 min) and 55°C (40 min); microwave vacuum drying (MVD) at 1800 Watt (20 min) and 4800 Watt (10 min) were studied. When considered in both antioxidant activities and acceptability among HD samples, the sample at 80 °C obtained the highest total phenolic content (TPC) and the antioxidant ability of FRAP (P <0.05) as well as odor acceptance scores (p < 0.05). However, no diflerences in appearance of dried flower and the infusion, color flavor of the infusion and overall acceptance scores of all samples were observed (P > 0.05). Among the IVD samples, the infusion at 50°C had higher ABTS and DPPH radical scavenging activities than that of 55°C (p < 0.05). The acceptance scores of the dried flower and the infusion of both samples were not significantly different (p > 0.05). Comparing among the MVD samples, The MVD sample at 4800 W obtained higher TPC, TFC, DPPH radical scavenging activity and FRAP than that at 1800 W (p < 0.05). However, no differences in acceptance scores of all characteristic were found between both samples (p > 0.05). When comparing among the conditions selected in each drying method, including the HD at 80°C, the IVD at 50°C, the MVD at 4800 Watt and the Freeze dry (FD) methods, it was found that the FD has the highest TPC (32.61 # 0.31 mg gallic / g dry weight), followed by The IVD at 50°C (28.45 # 0.12 mg gallic / g dry weight) the HD at 80°C (19.55 ÷ 0.18 mg gallic / g dry weight) and the MVD at 4800 watts respectively (8.18 ÷ 0.04 mg gallic / g dry weight). When considering on the antioxidant activity, it was found that the HD at 80°C had the highest ABTS antioxidant activity (P <0.05), while the FD had the highest DPPH radical scavenging and FRAP (P <0.05) activities. Nevertheless the IVD sample obtained the lowest ABTS, DPPH radical scavenging and FRAP antioxidant activity (P <0.05). The acceptance test result showed that the FD and the IVD at 50°C had the highest appearance and color scores of the dried flowers (p < 0.05). When considering on the infusion, the IVD at 50°C and the MVD at 4800 watts had the highest appearance and color scores (P <0.05). In addition, no differences in odor, flavor of infusions and overall acceptance score were observed among the HD at 80°C the IVD at 50°C and the MVD at 4800 watts samples (P > 0.05). However, the FD obtained the lowest scores of appearance, color, odor. flavor and overall (P <0.05). Purchase intent scores of the HD at 80°C the IVD at 50°C and the YVD at 4800 watts were rated under criterior of "likely to buy" and "may to buy the product" with frequency of 60% 58% and 56%, respectively. While the FD were scored at "definitely not buy the product" and "may not buy the product" with frequency 50%. The main phenolic compounds found in the samples were polyphenols, phenolic acid including quinie acid, SZ-Cafleoylquinie acid, chlorogenic acid, 1,3-Dicaflcoylquinie acid and flavonoid substances i.c. catechin and rutin. While, those found in FD sample were quinic acid, chlorogenie acid rutin and 1,3-Dicalleoylquinie acid. In addition, the HID sample also contained callic Acid. When considered on both antioxidant activities and acceptability, the HD at 80°C and IVD at 50°C were the most suitable methods for producing tea from the Robusta coffee flower.