Response surface optimisation for the extraction of phenolics and flavonoids from a pink guava puree industrial by‐product

Summary Pink guava puree industry produces huge amount of by‐products that have potential as sources for polyphenols. Response surface methodology was implemented to optimise the extraction conditions for phenolics (Y1) and flavonoids (Y2) from a by‐product of the guava industry. A three‐factor inscribed central composite design was employed to determine the effects of three independent variables, namely pH (X1: 2–6), temperature (X2: 40–60 °C) and time (X3: 1–5 h), on the response variables. The corresponding predicted values for phenolics and flavonoids were 336.30 and 427.35 mg 100 g−1, respectively. Predicted values for extraction rates of phenolics agreed well with experiment values; R2 of 0.902. However, the model derived for flavonoids extraction was less reliable; R2 of 0.983. Increase in time and temperature was found significant in increasing the extraction rate. The optimum conditions for extracting phenolics by ethanolic solvent occurred at a pH of 2 and 60 °C for a 5‐h extraction.