Tomato processing wastes as essential raw materials source

Abstract

Chemical composition of various fractions of tomato processing wastes was investigated. The seeds were found to contain about 27% hexane-extracted lipids. Oleic acid was the most predominant fatty acid, followed by palmitic acid. The seed flake obtained after hexane extraction had indicated a high protein content (-40%) high in threonine and lysine. Elemental analysis of the hexane-extracted tomato seed flour revealed that K, Mg, Na, and Ca were the major elements, followed by Fe, Mn, Zn, and Cu. Acetone extraction of the wet tomato skins yielded a highly colored concentrate consisting mainly of lycopene (total yield of about 12 mg per 100 g of wet tomato skins). The pigment freed skin residue was found to contain about 11% protein, with lysine, valine, and leucine as the most predominant essential amino acids. Elemental analysis showed that Ca, K, Na, and Mg were the major elements in tomato skins. About a third of tomatoes (Lycopersicon esculentum L.) delivered to processing plants ends as processing waste (Ries and Stout, 1962). The introduction of mechanical harvesting is estimated to have doubled the quantity of such waste material (Ben-Gera and Kramer, 1967). The waste during tomato processing is mainly obtained in the form of seeds and skin residues. The seeds were indicated as an edible oil source and tomato seed flake as a protein source (Boni and Sodini, 1981). Tomato is one of the most common vegetables in Iraq. It is mainly processed for the production of pastes, juice, and sauce. AI-Abadi (1981) estimated the annual quantity of wasted tomato seeds and skins (based on data for 1980) from tomato processing plants in Iraq at loo00 tons. The importance of utilization of these waste materials in Iraq may be judged from the fact that there is no revenue from the sale of these pro- cessing byproducts and dumping of these processing wastes at the nearest landfill site will add to the processing cost. On the other hand, if these wastes remain unutilized, they not only add to the disposal problem but also aggravate environmental pollution. The use of these wastes as animal feed during out season period is limited mainly to high mold susceptibility. Attempts to dry these residues to stable condition (10% moisture) will add to their cost. The present study was undertaken with the understanding that the results of this study will be of value in designing a unit to be installed on-site to produce some useful products from the tomato processing wastes. EXPERIMENTAL SECTION Tomatoes. Tomatoes (Lycopersicon esculentum L., cv. Pearson) are used by the cannery state plant in (Duhock) (northern part of Iraq) to produce tomato pastes. Processing Procedure. On delivery to the cannery the fruits were washed with tap water and fed into a disinte- grator. The seed portion was automatidy separated from the fruit parts and collected. The remaining macerate (tomatoes cut into pieces) is exposed to a short-period steam treatment (75-80 C for about 30 s) and then passed through a fiiher equiped with a suitable screen to remove the skins. Tomato pastes are usually prepared by con- centrating the resulting tomato juice to contain about 25-28% total solids. The ratio of tomatoes (as a raw material) to tomato pastes produced was about 7:l (w/w). Samples. As a standard procedure, samples were taken in triplicate (100 g each) and stored in a deep freezer until required for analyses. Prior to analysis, seed samples were