TOMATO POMACE AS A SUSTAINABLE PROTEIN SOURCE: IMPACT OF CONVENTIONAL ALKALINE, ULTRASOUND, AND MICROWAVE-ASSISTED EXTRACTION ON PROTEIN CONTENT, YIELD, AND FUNCTIONAL PROPERTIES

Date

2025-9-1

Author

ALJURF, BODOOR

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Tomato pomace, an abundant by-product of the tomato processing industry, is rich in protein and other valuable compounds. However, it is currently mostly utilized as animal feed, with considerable potential remaining for higher-value applications in human nutrition. Valorizing this agro-industrial waste as a sustainable protein source aligns with efforts to promote circular food systems and plant-based alternatives. In this study, protein extraction from tomato pomace was carried out using three methods: conventional alkaline extraction (CAE), microwave-assisted alkaline extraction (MWAE), and ultrasound-assisted alkaline extraction (USAE). The objective was to evaluate and compare these methods in terms of protein content, yield, and functional properties. Protein content was determined using the Kjeldahl method, while solubility was evaluated using the Bradford assay. Functional properties, including foaming capacity and stability, emulsifying activity and stability, water-holding capacity, oil-holding capacity, and color parameters (L, a, b*), were assessed. Structural differences between protein extracts were analyzed using FTIR spectroscopy, and antioxidant activity was determined by DPPH⸱ radical scavenging assay. CAE and MWAE yielded similar protein contents (44.46% and 45.12%, respectively). However, MWAE significantly reduced the extraction time from 1 h to 3 min. USAE yielded the lowest protein content (42.61%). MWAE showed the highest protein recovery yield (36.31%), followed by USAE (31.80%) and CAE (28.20%). Protein solubility was comparable across all methods. MWAE and USAE showed better functional properties than CAE, especially in foaming and emulsifying capacity. FTIR analysis revealed structural differences, and the highest antioxidant activity was observed in MWAE extracts. These findings support MWAE and USAE as effective, sustainable alternatives for protein recovery from tomato pomace.

Subject Keywords

Tomato pomace, Functional properties, Protein extraction, Ultrasound-assisted extraction, Microwave-assisted extraction

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https://hdl.handle.net/11511/115632

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Graduate School of Natural and Applied Sciences, Thesis