Effect of steam blanching and high temperature drying on the physicochemical properties, antioxidant activities and cons
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ORIGINAL ARTICLE
Effect of steam blanching and high temperature drying on the physicochemical properties, antioxidant activities and consumer acceptability of Hibiscus cannabinus leaves tea Yen Teng Haw1 • Yan Yi Sim1 • Kar Lin Nyam1
Revised: 4 February 2020 / Accepted: 29 April 2020 Ó Association of Food Scientists & Technologists (India) 2020
Abstract Kenaf (Hibiscus cannabinus) leaves are produced as the by product when kenaf stems were harvested. The kenaf leaves was examed for the applicable possibility as herbal tea due to their rich phenolic content. In this study, the effect of steam blanching and high temperature drying on physicochemical properties, antioxidant activity and consumer acceptability of the kenaf tea leaves were studied. Results showed that steam blanching prior ovendrying improved the extractability of phenolic compounds, leading to the increase in total flavonoid content, 2,2diphenyl-1-picrylhydrazyl radical scavenging activity, and ferric reducing antioxidant power. Drying at 120 °C was able to preserve more phenolic compounds, at the same time developing better taste, mouthfeel, and overall acceptability of kenaf leaves tea. Caffeic acid, tannic acid, catechin, and chlorogenic acid in kenaf tea leaves infusion were analyzed by ultra high performances liquid chromatography. In conclusion, steam blanching prior to 120 °C oven-drying was the best process method for the production of kenaf leaves into acceptable tea type. Keywords Steam blanching Antioxidant Ultra high performances liquid chromatography Caffeic acid Catechin
& Kar Lin Nyam [email protected] 1
Department of Food Science and Nutrition, Faculty of Applied Sciences, UCSI University, No. 1, Jalan Menara Gading, Taman Connaught, 56000 Kuala Lumpur, Wilayah Persekutuan Kuala Lumpur, Malaysia
Introduction Plant is a common source of food and medicine, either in the form of traditional medicine or as pure active ingredients (Farnsworth et al. 1985). Many exogenous antioxidants are therefore derived from food and medicinal plants. Generally, these natural antioxidants exhibit a wide range of nutritional and health benefits for human body (Zhou et al. 2016). Due to their health-promoting properties, there is increasing interest in making plant into herbal tea. As tea is the second most consumed beverage in the world especially in Asian countries. There are various tea leaves processing method, which can directly affect the chemical composition, characteristic flavour and unique aroma of the tea leaves. First, tea is processed by inactivation of polyphenol oxidase in the fresh leaves to prevent ezymatic oxidation. Inactivation can be done by steam blanching of leaves immediately after plucking. Steam blanching can also preserve more colour, polyphenolic content and antioxidant bioactivity than pan fixing in the production of tea leaves (Ahmed and Stepp 2012). In terms of sensory quality, steam blanching prior to drying is able to reduce bitterness of leaf by reducing the concentration of catechin (Hosomi et al. 2
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