Industrial by-products from tomato processing contain a significant amount of bioactive compounds that could be used to provide natural and sustainable source of antioxidants for functional food formulation, or to act as preservative ingredients in foods, say researchers.
The study – published in LWT - Food Science and Technology – compared the concentration of bioactive compounds in tomato processing by-products and unprocessed tomatoes. The research team found that on a dry weight basis, tomato by-products and wastes contained significantly lower amounts of lycopene, but had increased levels of beta-carotene, tocopherols, sterols and terpenes – while fatty acid profile were found to be similar in both processed wastes and unprocessed tomatoes.
“The results obtained indicate that industrial tomato by-products contain significant amounts of bioactive phytochemicals, which seem to be able to withstand industrial processing methods ... Most of these phytochemicals –tocopherols, polyphenols, carotenoids, some terpenes and sterols- are known to exert antioxidant activities,” explained the researchers, led by Nick Kalogeropoulos from Harokopio University, Greece.
“As tomato wastes are bioorganic materials and being in line with the trend for sustainability and recycling/reusing, these value adding constituents could be either isolated from the wastes to be used as natural antioxidants for the formulation of functional foods, or to serve as additives in food systems to elongate their shelf life,” they said.
Kalogeropoulos and his team noted that the tomato (Lycopersicon esculentum L.) is the second most important vegetable crop worldwide (behind the potato), “with annual production at 100 million tons fresh fruit produced in 144 countries.”
As such, processing is accompanied by the generation of a large amount of wastes, which are made up of bioorganic substances such as seeds, pulp and skins.
“Owed to rapidly expanding global demand on manufacturing processes and final products exerting minimal or no environmental risks, tomato processing wastes have been the subject of significant research during the last years aiming especially to the recovery of lycopene and β-carotene by several extraction schemes,” explained the research team.
In the new study, the team investigated the presence of health promoting phytochemicals – like carotenoids, polyphenols, sterols, terpenes and tocopherols – in tomato processing byproducts, “in order to evaluate the potential for their use as additives for the preparation of functional foods,” or for the use as a preservative ingredient in foods.
The team compared the contents of several bioactive phytochemicals, including sterols, tocopherols, carotenes, terpenes, total and simple polyphenols, in addition to measuring the radical scavenging capacity and reducing power of unprocessed tomatoes and processed tomato by-products.
Kalogeropoulos and his colleagues revealed that tomato by-products contained a similar amount of total polyphenols, and exhibited similar DPPH radical scavenging activity and ferric reducing power to unprocessed tomatoes.
“Among 18 simple polyphenols ...hydroxycinnamic acids predominated in whole tomatoes, while flavonoids predominated in tomato wastes with naringenin comprising 87% of flavonoids,” said the researchers.
They argued that since most of the phytochemicals determined in the by-products exert antioxidant activities, and have been previously suggested to have beneficial effects on human health, the tomato by-products “could be successfully utilised as functional ingredient for the formulation of antioxidant rich functional foods.”
Source: LWT - Food Science and Technology
Published online ahead of print, doi: 10.1016/j.lwt.2011.12.036
“Bioactive phytochemicals in industrial tomatoes and their processing byproducts”
Authors: N. Kalogeropoulos, A. Chiou, V. Pyriochou, A. Peristeraki, V.T. Karathanos