Evaluation of condensed tannins from coffee pulp (Coffea arabica) as a natural preservative: study in a model food

Abstract

The present study was designed to evaluate the antimicrobial capacity of condensed tannins, extracted and purified from coffee pulp (Coffea arabica), for use as a natural preservative in food industry products. Condensed tannins were extracted from coffee pulp residues by Ultrasound-Assisted Extraction (UAE) and purified by open column chromatography with Sephadex LH-20. First, the in vitro antimicrobial evaluation was performed with the disc diffusion method (1, 5 and 10 g L⁻¹) against bacteria such as Escherichia coli, Salmonella typhimurium, Staphylococcus aureus and Listeria monocytogenes causing various foodborne diseases (FBDs). The qualitative analysis showed the presence of tannins in the acetone fraction purified and showed inhibitory activity at 10 g L⁻¹ against S. typhi, S. aureus, and L. monocytogenes. No inhibition was observed against E. coli, highlighting its relative resistance under these conditions. To evaluate its efficacy as a food preservative, a corn-based model food typical of the north-central region of Mexico (bocoles) was formulated by incorporating the purified tannins at a concentration of 10 g L⁻¹. The formulation consisted of adding lard, salt and black beans or cottage cheese to the corn dough. The tannins were incorporated during the kneading stage. This ensured a homogeneous distribution of the compound in the final product, which was pre-cooked and packaged in vacuum-sealed polypropylene bags. The effect of condensed tannins on shelf life was compared with a control group (no food preservative) and a group treated with a commercial synthetic preservative (potassium sorbate and sodium benzoate). The results showed a statistically significant difference between the groups, indicating that the condensed tannins prolonged the shelf life of the bocoles in a manner comparable to the synthetic preservative. This study demonstrates the potential of condensed tannins as natural food preservatives and presents them as a viable and functional alternative to replace synthetic additives in the food industry, which have been associated with adverse health effects from prolonged consumption. Significantly, this finding highlights the impact it will have on the development of safer products in the food industry that meet consumer demand for natural ingredients.