From waste to value: Enhancing vegetable leather quality using guar and xanthan gums in carrot pomace and tomato pulp systems

The valorization of agro-industrial by-products is essential for sustainable food systems and reducing post-harvest losses. Carrot pomace and tomato pulp are nutrient-rich materials that remain underutilized despite their high content of dietary fiber, bioactive compounds, and pigments. This study investigated the effects of κ- carrageenan, guar gum, and xanthan gum at concentrations of 1, 1.5, and 2% on the physicochemical and quality characteristics of vegetable leathers produced from carrot pomace and tomato pulp. Leather appearance, water absorption capacity, bioactive compound retention, pigment stability, color, texture, and microstructure (SEM) were evaluated. κ-Carrageenan failed to form continuous leathers in both matrices, likely due to unsuitable ionic conditions for gelation, and was excluded from further analysis. Guar and xanthan gums improved leather formation, with effects depending on concentration and matrix type. Xanthan gum produced smoother, more flexible leathers with enhanced color retention and higher preservation of phenolics, ascorbic acid, and pigments compared to guar gum. In carrot pomace leather, xanthan at 1% achieved the highest β-carotene retention (27.25%), while guar gum resulted in lower acidity and browning. In tomato leather, xanthan at 2% significantly improved retention of lycopene (50.66%), phenolics (60.2%), and ascorbic acid (62%). Hydrocolloid incorporation also modified texture, increasing cohesiveness, springiness, and gumminess, while SEM analysis revealed more compact and homogeneous microstructures with increased porosity. These findings demonstrate the potential of hydrocolloid-assisted processing to transform vegetable processing residues into stable, nutrient-rich products, supporting waste valorization and sustainable food innovation.