An in-depth analysis of initial processing steps in the extraction of proteins from tomato (Solanum lycopersicum) leaves

Tomato leaves, the by-products from tomato production, are a promising source of proteins. An important challenge to extract proteins is that leaves are perishable materials. Here we investigated different post-harvest processing routes of tomato leaves (fresh processing, three-day storage, freezing, freeze drying and oven drying) to understand their effects on protein extractability from leaves. Proteins were extracted at floating pH and alkaline condition (pH 10). Obtained protein fractions were characterized according to protein solubility, protein profile, molecular weight distribution, secondary structure and color. Results showed that tomato leaves should be processed fresh for protein extraction. Alternatively, leaves can be stored for three-day at room temperature. Extraction at pH 10 did not result in enhanced protein extraction but led to dark brown color formation. Extensive protein degradation was induced during oven drying, providing a new processing route when degraded products such as peptides and free amino acids are the target products. Industrial relevance: To support the transition of human diet from animal-based to plant-based, it is important to find new plant protein sources. Tomato leaves, the by-products of tomato fruit production, are widely available and are unexplored source of proteins. An additional challenge of using leaves as a protein source lies in the perishable nature of tomato leaves. The presented study discussed the post-harvest processing options to extract proteins from tomato leaves. Our findings provided insights on how to upscale protein extraction from tomato leaves in the future.