Heat treatment improves the sensory properties of the ultrafiltration by-product of honeybush (Cyclopia genistoides) extract

BACKGROUND Ultrafiltration of green honeybush (Cyclopia genistoides) extract results in a by-product (retentate). Application of further separation processes for recovery of polyphenols would entail creation of additional waste. Repurposing the retentate as a food flavour ingredient provides an alternative valorization approach. RESULTS The retentate, suspended in water (270 g L-1), was heat-treated at 80 degrees C for 2, 4, 8 and 16 h, and at 90 degrees C for 2, 4, 6 and 8 h to change its sensory profile. The heat-treated retentate, diluted to beverage strength (2.15 g L-1), had prominent 'grape/Muscat-like' and 'marmalade/citrus' aroma and flavour notes. Overall, heating for <= 4 h increased the intensities of positive flavour and aroma notes, while reducing those of 'green/grass', 'hay' and bitterness, whereafter further heating only had a slight effect on the aroma profile at 80 degrees C (P < 0.05), but not at 90 degrees C (P >= 0.05). The heat treatments, 80 degrees C/4 h and 90 degrees C/4 h, were subsequently applied to different batches of retentate (n = 10) to accommodate the effect of natural product variation. Heating at 90 degrees C produced higher intensities of positive aroma attributes (P < 0.05), but was more detrimental to the phenolic stability, compared to 80 degrees C. CONCLUSION After heat treatment, the phenolic content of C. genistoides retentate, reconstituted to beverage strength, still fell within the range of a typical 'fermented' (oxidized) honeybush leaf tea infusion. The change in phenolic composition will not diminish the benefit of an improved sensory profile for the retentate by-product through heating. (c) 2021 Society of Chemical Industry.