Development of chemical-based reference standards for rooibos and honeybush aroma lexicons

• Published in: Food research international Vol. 127; p. 108734
• Main Authors: du Preez, B.V.P., de Beer, D., Moelich, E.I., Muller, M., Joubert, E.
• Format: Journal Article
• Language: English
• Published: Canada Elsevier Ltd 01.01.2020
• Subjects: Adult; Aged; Aroma lexicon; Aroma wheel; Aspalathus - chemistry; Beverages - analysis; Chemical reference standards; Female; Herbal tea; Humans; Middle Aged; Odorants - analysis; Quality control tools; Reference Standards; Herbal tea; Quality control tools; Aroma wheel; Aroma lexicon; Chemical reference standards
• ISSN: 0963-9969; 1873-7145
• DOI: 10.1016/j.foodres.2019.108734

[Display omitted] •Honeybush and rooibos aroma lexicons were validated using chemical standards.•Food grade chemicals (n = 100) were screened as candidate reference standards.•Selected chemicals (n = 65) were assessed for typicality of target aroma notes.•Levulinic acid had a high typicality score (90%) for ‘fynbos-sweet’ (honeybush).•Isophorone had a high typicality score (93%) for ‘rooibos-woody’ (rooibos). The honeybush sensory wheel was revised, using a large sample set (n = 585) comprising of the major commercial Cyclopia species, i.e. C. intermedia, C. subternata and C. genistoides. Only positive and negative aroma attributes were included in the wheel. Chemicals were identified to serve as reference standards for the honeybush (Cyclopia spp.) lexicon. Similarly, chemical-based reference standards were identified for the rooibos (Aspalathus linearis) lexicon. From a comprehensive literature search and gas chromatography–mass spectrometry analyses, chemicals were screened by an expert panel for their suitability in terms of typicality of the target aroma. Each chemical was evaluated in a ‘base tea’ and compared to a specific ‘reference tea’ exhibiting a high intensity of the target aroma. A total of 30 and 44 chemicals for rooibos and honeybush, respectively, were selected for validation by a trained panel. Descriptive sensory analysis was conducted to assign typicality and intensity scores for each chemical representing a target aroma attribute. Several chemicals were identified as suitable reference standards for the following aroma notes: isophorone (‘rooibos-woody’), maltyl isobutyrate (‘caramel’), cis-3-hexenol (‘green grass’), 4-oxoisophorone (‘seaweed’) and 2,4,6-trichloroanisole (‘musty/mouldy’) for rooibos; and 2-acetyl-5-methylfuran (‘woody’), levulinic acid (‘fynbos-sweet’), maltyl isobutyrate (‘caramel’), and 2-acetylpyrrole (‘nutty’) for honeybush.