# Enhancing the Antioxidant Properties of Carrot Wastes Through Lactic Acid Fermentation and Thermophysical Treatments

## TL;DR

This study shows how carrot waste can be turned into a valuable source of antioxidants using fermentation and microwave or ultrasound treatments.

## Contribution

The novel contribution is demonstrating how lactic acid fermentation and thermophysical treatments can enhance antioxidant properties in carrot waste.

## Key findings

- L. salivarius fermentation increased total phenolic content by 1.3-fold and DPPH antioxidant activity by 2.7-fold.
- Ultrasound treatment at 100 g–15 min maximized increases in total phenols, flavonoids, and ABTS antioxidant activity.
- Microwave treatment at 3 W/g increased total phenols and flavonoids but reduced antioxidant activity with prolonged exposure.

## Abstract

Carrot wastes contain valuable bioactive compounds, particularly carotenoids, phenolics, and dietary fibre, whose concentration and bioaccessibility can be enhanced through structural and biochemical modifications induced by thermophysical and biological treatments, providing valorization potential. This study evaluated the effects of microwave treatment (1.5 or 3 W/g for 2, 4, and 6 min), ultrasound treatment (100 or 200 g at 40 kHz for 5, 10, or 15 min), and lactic acid fermentation with Lactiplantibacillus plantarum, Ligilactobacillus salivarius, and Limosilactobacillus reuteri for 48 h on the plant cell structure and physicochemical and antioxidant properties of fresh-cut carrot wastes. Among the tested strains, L. salivarius showed the highest growth after 24 h of fermentation (from 8.8 to 9.7 log10 CFU/g), increasing total phenolic content by 1.3-fold. Antioxidant activity improved, with DPPH peaking at 48 h (2.7-fold) and ABTS increasing from early fermentation stages. Ultrasounds enhanced antioxidant properties, so that 100 g–15 min led to maximum increases in total phenols, flavonoids, and ABTS (fold-increase of 1.3, 2.7, and 1.4, respectively), while DPPH values peaked after 5 min (70% increase). Microwave treatment at 3 W/g increased total phenols and flavonoids 1.3-fold, although prolonged exposure reduced antioxidant activity. Overall, selected thermophysical and fermentation treatments may enhance the bioactive potential of carrot wastes.