Evaluation of tomato processing by-products: A comparative study in a pilot scale setup

This study aims at providing a comparative evaluation of tomato processing by-products, i.e., seeds and peel. A pilot scale process has been demonstrated for extraction and drying (both freeze and cabinet drying) of tomato seeds and peel. Various aspects of dried tomato seeds such as its protein content, amino acid profile, calculated protein efficiency ratio (PER), presence of antinutritional factors, polyphenol contents and antioxidant activities were evaluated. In this study, the total polyphenol content in the hydrophilic extract as well as antioxidant activities of tomato peel were found to be 66.5 and 38.2% higher, respectively, than that of the tomato seed meal showing importance of the former from a functional point of view. Tomato seed protein isolate (92%) prepared from tomato seed meal had a calculated PER of 2.66. The protein isolate contained all essential amino acids (including lysine), meeting the minimum requirements of reference protein for preschool children aged 1–2 years (WHO/FAO/UNU). The tomato seed protein isolate showed negligible levels of phytate (3.48 μg/g) and trypsin inhibitory activity (2.655 TIU/mg). This study clearly highlights that tomato seed, a by-product of tomato processing industry, is a rich source of high-quality plant protein together with intrinsic polyphenols and antioxidant activities, although the functional properties being less dominant than the peel counterpart. Therefore, tomato seed meal with unique protein quality could be regarded as a potential source of protein-rich adjunct in various food formulations.