Analysis and Evaluation of Sensory Properties and ... - UCSI University

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INTERNATIONAL JOURNAL FOR THE ADVANCEMENT OF SCIENCE AND ARTS, VOL. 2, NO. 2, 2011 Fermented, unfermented, bitterness, astringency, grassiness and sourness were six sensory attributes evaluated by the panellists using the 15-cm line scale. Table 1: Definitions and standard references for quantitative descriptive analysis of Thunbergia laurifolia teas produced from different drying methods Sensory attribute Definition Standard reference * Fermented Aromatics association with fermented teas such as oolong tea or black tea Unfermented Aromatics associated with green tea Bitterness Fundamental taste sensation associated with caffeine and quinine Astringency Feeling which shrivels the tongue and associated with tannins Grassiness Aromatics associated with cut grass Cut grass Citric acid Aromatics associated with citrus fruits Roasted grain Aromatics associated with roasted grain Floral Aromatics associated with flowers such as jasmine * Intensity scale of 2 Oolong tea (5 g) from Xiamen Tea Co. Ltd., China, infused with 200 ml boiling water for 2 min Green tea (1 g) from Xiamen Tea Co. Ltd., China, infused with 200 ml boiling water for 2 min Caffeine solution (0.05 %) from Merck, Germany Tannic acid solution (0.08 %) from Acros Organics, USA Citric acid solution (0.05 %) from Fisher Scientific, UK Roasted barley tea (3 g) from Dong Suh Food Co. Ltd., Korea infused with 250 ml boiling water for 2 min Jasmine tea (1 g) from Xiamen Tea Co. Ltd., China infused with 200 ml boiling water for 2 min Two standard references per attributes were provided to the panellists, one had a low intensity while another had a high intensity (Table 2). These standard references provided them with an idea of the range of samples intensities. Panellists were instructed to evaluate the given samples, one at a time for all six attributes, in separate booths to reduce distraction and interaction. They were not allowed to discuss their results after each session. 19
INTERNATIONAL JOURNAL FOR THE ADVANCEMENT OF SCIENCE AND ARTS, VOL. 2, NO. 2, 2011 Table 2: Low and high intensities of standard references per attribute Sensory attribute Intensity Standard reference Fermented Unfermented Bitterness Astringency Grassiness Sourness 2.5 Hedonic Survey Low – 1 High – 2 Low – 1 High – 2 Low – 1 High – 2 Low – 1 High – 2 Low – 1 High – 2 Low – 1 High – 2 Oolong tea (16 g/L) Oolong tea (25 g/L) Green tea (3.3 g/L) Green tea (5.0 g/L) Caffeine (0.03%) Caffeine (0.05%) Tannic acid (0.05%) Tannic acid (0.08%) Cut grass (50%) Cut grass (100%) Citric acid (0.03%) Citric acid (0.05%) A hedonic survey of consumer acceptability of the five T. laurifolia teas was conducted in the Food Science Laboratory of UCSI University. A total of 129 respondents, including students, lecturers and other staff members of UCSI University, as well as family members, participated in the survey. Respondents were invited to evaluate the tea samples, one at a time, in separate booths. The samples were coded with three-digit random numbers and were served warm in transparent testing cups in randomised presentation order to minimise bias. The evaluation was done under normal white fluorescent light, as appearance was an evaluated attribute of the survey. The respondents were then asked about their degree of liking of the teas in terms of appearance, aroma, flavour and overall acceptability, based on a 9-point hedonic scale, ranging from dislike extremely (1) to like extremely (9) [22]. A questionnaire was also provided to obtain their opinions on the tea samples, tea preferences and purchase intent. 2.6 Statistical Analysis Analysis of QDA and consumer acceptability of the T. laurifolia teas were performed in triplicate, and results were presented as means ± standard deviations (SD). Analysis of variance (ANOVA) was calculated using the Tukey’s HSD test at P < 0.05. Correlation analysis was also performed to determine the relationship between the QDA data and hedonic survey data. 20
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