Tomato pomace as a sustainable protein source: Comprehensive characterization of proteins extracted by conventional alkaline, microwave, and ultrasound-assisted methods

Date

2026-07-01

Author

Aljurf, Bodoor Nabil
Cutroneo, Sara
Bugatti, Kelly
Barlas, Bora
Bashir, Amro K. H.
Şahin, Serpil
Öztop, Halil Mecit
Tedeschi, Tullia

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Tomato pomace is an abundant by-product of the tomato processing industry and represents a promising source of plant-based protein for sustainable food systems. In this study, proteins were extracted from tomato pomace using conventional alkaline extraction (CAE), microwave-assisted alkaline extraction (MWAE), and ultrasoundassisted alkaline extraction (USAE), and the methods were compared in terms of protein content, recovery yield, functional properties, structural characteristics, and amino acid composition. CAE and MWAE yielded protein contents that were not significantly different (p > 0.05), at 43.59% and 44.00%, respectively, whereas USAE resulted in a slightly lower protein content (41.47%). MWAE markedly intensified the extraction process by reducing the extraction time from 60 min to 3 min, while USAE reduced it to 5 min, without compromising protein yield or functionality. The highest protein recovery yield was obtained by MWAE (35.40%), followed by USAE (30.95%) and CAE (27.66%). Both MWAE and USAE improved foaming and emulsifying capacity relative to CAE, while MWAE also exhibited the highest antioxidant capacity. FTIR analysis revealed extractiondependent changes in protein secondary structure, characterized by a reduction in alpha-helix content and an increase in beta-sheet structures for MWAE and USAE, which were consistent with the observed functional enhancements. SDS-PAGE profiles showed comparable molecular weight distributions across all extraction methods, indicating preservation of the protein backbone. Amino acid analysis demonstrated similar overall profiles among the extracts, although ultrasound-assisted extraction led to a pronounced reduction in tryptophan, highlighting a trade-off between functional modification and amino acid stability. Overall, the results demonstrate that MWAE and USAE enable rapid and efficient protein recovery from tomato pomace while maintaining or enhancing functional performance, with MWAE offering the most favorable balance between processing efficiency, protein quality, and nutritional integrity.

URI

https://hdl.handle.net/11511/118847

Collections

Department of Food Engineering, Article