398: Optimizing an Alkaline Hydrolysis for Coffee By-Products to Increase the Yield of Caffeic Acid, a Precursor for Pyranoanthocyanins Formation

Introduction

The coffee industry generates numerous by-products, with coffee husk and spent coffee ground taking a major proportion. They contain high concentrations of chlorogenic acid, which can be hydrolyzed into caffeic and quinic acids. Caffeic acid can serve as a precursor of pyranoanthocyanins—vibrant, stable anthocyanin-derived pigments. Our goal was to optimize coffee by-products alkaline hydrolysis conditions to increase the caffeic acid production yields, and test if these extracts could form pyranoanthocyanins with known anthocyanins sources.

Methods

Dried coffee by-product (1g) was ground to a fine powder and alkali (KOH or NaOH) was added to saponify it. Preliminary tests used different alkali concentrations (5-40%), sonication times (30-75 min) and solid-liquid ratio (1:10-1:35). Conditions were then optimized using response surface methodology (RSM) using NaOH (10%, 20% and 30%), sonication times (30, 45, 60 min), and solid-liquid ratio (1:10, 1:20 and 1:30). Caffeic acid release and concentration were determined by the HPLC-PDA. Coffee by-product extracts obtained were mixed with red onion peel extracts in different molar ratios (1:2 to 1:30, anthocyanin: caffeic acid) at pH 3.1, 45°C to induce pyranoanthocyanins formation. Chemical changes were monitored by HPLC-PDA-MS/MS.

Results

Preliminary results showed higher caffeic acid recovery with NaOH as compared to KOH. Also, yields increased with sonication time <1 hr and NaOH concentration <30%. Additional time or concentration resulted in lower caffeic acid yield. The solid-liquid ratio didn’t affect yields when they exceeded 1:30 g/mL. The optimum conditions to maximize caffeic acid yields from coffee husks, determined by RSM, were 27% NaOH, at 1:25 g/mL solid-liquid ratios, sonicated for 53 min. The highest caffeic acid yield obtained from coffee husks was 225.2 mg/100 g. Pyranoanthocyanins were successfully produced from coffee by-products and red onion peel extract mixtures after 1day of incubation.

Significance

This study highlights the potential of using crude coffee by-product extract and red onion peel instead of purified compounds to reduce production costs and environmental impact. It could help reduce the waste from coffee production and contribute towards a sustainable way to produce pyranoanthocyanins.

Authors: Yunyang Qi, Xinyue Fan, M. Monica Giusti