Evaluation of Tomato Processing By‐Products: A Comparative Study in a Pilot Scale Setup

Abstract

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. 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 plant‐based 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.

Biorefinery cascade processing for creating added value on tomato industrial by-products from Tunisia

“…The nutritional quality of the protein from tomato residues was estimated based on two parameters: amino acid scoring pattern and protein efficiency ratio (PER) according to Sarkar and Kaul [11]. The amino acid score was calculated by dividing the content of each amino acid by a reference amino acid pattern of a protein recognized for the nutrition of preschool children (1–2 years old) [36].…”

“…The amino acid score was calculated by dividing the content of each amino acid by a reference amino acid pattern of a protein recognized for the nutrition of preschool children (1–2 years old) [36]. Moreover, the PER was calculated as an average of the following three equations with amino acids contents measured as g/100 g protein [11]:…”

“…Indeed, tomato peels were reported to contain, on dry basis, 14–20% protein [6, 7], 40–74% lignocellulosic material [6–8], and 3–5% oleoresin, being the oil fraction from tomato peels [9, 10]. Besides, tomato seeds were shown to contain 20–40% protein [11, 12], 35–50% lignocellulosic material [7, 13], and 18–37% oil [14, 15]. Nevertheless, currently, valorization of tomato peels has attracted little interest, since they are mostly considered for the extraction of carotenoids, especially lycopene [6], while tomato seeds have attracted very limited attention so far.…”

“…Yet, regarding literature, few papers have recently suggested other valorization pathways of tomato by-products such as biofuel production or as a source of oil, polysaccharides, and protein. For instance, Sarkar and Kaul [11] identified a pilot plant setup to extract tomato seeds protein toward its commercial application as a functional additive in food formulations. Additionally, the study by Rossini et al [19], performed on tomato manufacturing residues, suggested the use of tomato peels for combustion and tomato seeds for mechanical oil extraction.…”

Development, properties, and stability of antioxidant shrimp muscle protein films incorporating carotenoid-containing extracts from food by-products

“…Other food industries, such as the tomato industry, also generate considerable amounts of waste rich in carotenoids. It is estimated that peel and seeds represent 20e50 g/ kg of the initial weight of tomatoes (Knoblich, Anderson, & Latshaw, 2005), from which fiber and carotenoids, mainly lycopene, have been extracted (Ranveer, Patil, & Sahoo, 2013;Sarkar & Kaul, 2014).…”