Formulation and sensory evaluation of herb tea from moringa oleifera, hibiscus sabdariffa and cymbopogon citratus

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Date
2011
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Abstract
The sensory appeal of tea, like all food products, is an important consideration in new product development. Tea in general and herb tea in particular, are gaining increasing consumer attention due to a growing awareness of health benefits derived from their consumption. Even though several underutilized plants exist with potential for processing into herb tea, research in product development of herb teas is limited. The objectives of the study were (1) to conduct chemical analyses on three herbs – Cymbopogon citratus leaves, Hibiscus sabdariffa calyces and Moringa oleifera leaves – in order to assess their potential for food product development; (2) to conduct acceptance tests on herb tea prepared from formulations of the herbs; and (3) to generate descriptive vocabulary on the sensory properties of herb tea. The herbs were unblanched and solar-dried. Standard methods were used to measure proximate parameters, water soluble extractives (WSE), light petroleum extractives (LPE), pH, total polyphenolics content (TPC) and minerals (Ca, Fe, Cu and Zn). Fifty (50) untrained panelists conducted acceptance tests on infusions from nine formulations and one control, and a nine-member trained panel conducted descriptive tests on infusions from three selected blends. Results of chemical analysis revealed that Moringa, Roselle and Lemon grass had, respectively, TPC of 35.70 mg/g, 27.81 mg/g and 15.37 mg/g; WSE of 7.44%, 12.38% and 4.07%; LPE of 3.48%, 2.71% and 4.1%; pH of 5.47, 2.73 and 4.53. Mineral analyses revealed that Moringa, Roselle and Lemon grass had, respectively, Ca of 412.5 mg/100g, 294 mg/100g and Fe of 12.93 mg/100g; 24.26 mg/100g and 11.58 mg/100g. A total of seventeen (17) descriptors were generated, defined and referenced for herb tea comprising six (6) appearance, three (3) aroma, one (1) flavour, five (5) taste and two (2) mouthfeel descriptors. Herb tea brewed from product 532 (50% Moringa, 30% Roselle and 20% Lemon grass) was the most preferred in colour, flavour, astringency and overall sensory properties while the control (100% Moringa) brewed the least preferred herb tea in most of the sensory attributes. Product 532 was predominantly reddish in colour (12.56) while the control was yellowish (11.93). Product 532 had high mean scores for Turbidity (12.67), Herbal aroma (11.41), Citrus aroma (11.30), Sour taste (12.15) and Astringency (11.41) while the control had significantly low scores for most of these attributes (≤ 2.33). Herb tea from blend of Moringa, Roselle and Lemon grass was more appealing than herb tea from only Moringa.
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A thesis submitted to the Department of Biochemistry and Biotechnology, Kwame Nkrumah University of Science and technology, in partial fulfillment of the requirement for the award of the degree of Master of Science (Food Science and Technology)
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