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 �g/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.
PRACTICAL APPLICATIONS
With the increased industrial demand of protein sources, there has been an
upsurge of research efforts in recent years to extract dietary proteins from plantbased
sources. By-products of oilseeds, fruits and vegetable-processing industries
can be sustainable low-cost protein alternatives, which are available at no additional
cost and can find commercial valorization in food formulations. As an
example, this study identified a pilot plant setup to produce tomato seed protein
isolate and investigated protein quality, antinutritional factors as well as compared
the polyphenol content and antioxidant activities in the context of its counterpart
by-product tomato peel. This knowledge will facilitate the use of tomato seed
protein isolate as a low-cost protein-rich adjunct with functional benefits in food
formulation. Most importantly, this study highlights that high-quality plant
protein isolates can be recovered from agro-industrial by-products, thus adding
commercial value to them and allowing their industrial exploitation.