Effect of thermal processing on the antioxidant capacity, microbiological safety, and physicochemical properties of a controlled fermentation beverage from purple maize (Zea mays L).

In the production of controlled fermented beverages, thermal processing is an essential step to ensure microbiological safety, while also facilitating starch gelatinization in maize-based beverages. However, it can degrade antioxidant compounds from purple maize, such as anthocyanins and polyphenols. The aim of this study was to identify an adequate thermal treatment for a purple maize beverage that maximizes antioxidant capacity while ensuring its microbiological safety prior to controlled fermentation.

A 1:9 ratio of purple maize to water was soaked for 12 hours. The mixture was then milled and strained. The resulting liquid was subjected to different heat treatments: a no-heat control (A_c), 85 °C for 5 minutes (A₁), 85 °C for 10 minutes (A₂), and 121 °C for 15 minutes (A₃). Total mesophilic bacteria, total coliforms, and yeasts were quantified by plate count. The pH, total soluble solids (TTSs), color based on the CIELAB parameters, and apparent viscosity were measured. Total phenolic compounds (TPCs), monomeric anthocyanins (MAAs), and in vitro antioxidant capacity were assessed via DPPH and ABTS assays. Statistical analysis was performed using one-way ANOVA, followed by Tukey's test (p<0.05).

All heat treatments ensured the microbiological safety of the beverage. A₁ exhibited the highest apparent viscosity. The total color difference (ΔE) for samples A₁ and A₂ indicated minimal perceptible color changes. TPCs, MAAs, and the resulting antioxidant capacity were all significantly higher in sample A₁. Therefore, the A₁ treatment effectively enhances the extraction of TPCs and MAAs, leading to the highest antioxidant capacity. However, its viscosity requires further evaluation for consumer acceptability.