Development of sensory tools for green rooibos (Aspalathus linearis (Burm.f.) R.Dahlgren) and changes in quality attributes during shelf‐life storage

Abstract

BACKGROUNDGreen rooibos (Aspalathus linearis (Burm.f.) R.Dahlgren) herbal tea is popular due to its health‐promoting properties. Information on its characteristic sensory profile is scarce and sensory tools to define product variation are needed. The storage conditions and time during its shelf‐life are hypothesized to affect the product quality.RESULTSProduction batches from two producers spanning 5 years (n = 57) were analyzed using descriptive sensory analysis. Primary attributes (>30 median intensity; 100% occurrence frequency) included ‘hay/dried grass’, ‘cooked oats’, ‘tobacco’, ‘honey’ and ‘caramel’ aromas, and astringent mouthfeel. ‘Cooked vegetables’, ‘green grass’, ‘stewed fruit’, ‘rooibos‐woody’, ‘marmalade’ and ‘cardboard’ aromas, sweet taste and bitter taste were secondary attributes (10–20 median intensity; 100% occurrence frequency). The same flavor attributes were present, except for sweet‐associated and fruity notes. A sensory lexicon and sensory wheels for aroma and palate attributes were constructed from the data. The shelf‐life stability of green rooibos was evaluated in moisture‐impermeable (pouches) and moisture‐permeable (sachets) packaging at 25 and 40 °C at 60% relative humidity over 24 weeks. Green rooibos samples stored in pouches at 4 °C were also evaluated. Storage in sachets led to moisture uptake (~10 g (100 g)−1 dry basis) and an increase in water activity (>0.6), causing degradation of chlorophyll and dihydrochalcones. Changes in color and sensory profile (decreased vegetal, cereal and cardboard aromas and increased sweet‐associated and fruity aromas) were evident and more pronounced at the higher storage temperature.CONCLUSIONSStorage at ≤25 °C in moisture‐impermeable packaging material is recommended for green rooibos herbal tea. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.