A modified Folin-Ciocalteu method for the microdetermination of total phenolic content in honey

Polyphenols are major antioxidant activity-associated bioactive substances in honey. Measurement of the total phenolic content in honey is of great importance for predicting antioxidant activity and characterising or selecting honey samples for their use as antioxidants or natural food preservatives. Considering that the original Folin-Ciocalteu (F-C) assay for total phenolic content determination is either time-consuming or high-cost, a microplate reader-based study was conducted to modify and validate the original F-C assay for the microdetermination of total phenolic content in honey samples. The linearity (R2 = 0.9982), detection limit (8.61 ± 0.33 mg gallic acid equivalents (GAEpkg-1 honey), quantitation limit (26.08 ± 0.99 mg GAE>kg-1 honey), and recovery rate (93.46 - 109.99%) were acceptable. The results suggested that the proposed F-C assay is fast, sensitive, precise, and repeatable. The method was successfully applied to analyse a total of 33 honey samples from 9 floral origins and 12 geographical regions. The modified F-C assay is low cost and easy to operate, and therefore could be applied to routine analysis.