Reverse Flow Injection Spectrophotometric Determination of Total Acidity in Beverages Using Butterfly Pea Flower Extract.

Background: Monitoring total acidity during beverage production is crucial for quality control (QC). The standard acid-base titration, though widely used, is slow and generates hazardous waste through the use of acid-base indicators.

Objective: To develop an analysis method for beverage samples to determine total acidity using a natural reagent from butterfly pea flower as the colorimetric reagent.

Methods: The determination of total acidity in beverages was based on the reaction of citric acid with anthocyanin extracted from butterfly pea flowers. The decreased absorbance of anthocyanin was measured at 620 nm. A two-line reverse flow injection manifold was used to perform online dilution of samples.

Results: Under optimal conditions, the calibration curve equation 1/A = 0.03782C + 0.00241 (A = absorbance and C = concentration) was linear over a range of 0.050-0.25% (w/v) citric acid. The LOD and LOQ were 0.0123 and 0.0409% (w/v), respectively. The system achieved a throughput of 120 samples per hour with comparable accuracy and precision to the standard titrimetric method.

Conclusion: The injection of butterfly pea flower extract into beverage samples with online dilution in a reverse flow injection system (FIS) was reported for the first time for the determination of total acidity.

Highlights: Use of a green reagent in the method reflects its alignment with the principles of green analytical chemistry, providing a rapid and straightforward solution.