| Food Chain - Number 22 - January 1998 |
Food processing generally creates byproducts and waste materials. In many cases the by-products are unusable and their accumulation and/or disposal leads to environmental problems. Utilisation of the waste products is therefore attractive, especially if they are transformed into a product with a high market value.
A research group at the National Technical University of Athens is investigating the use of tomato waste products to form a protein rich concentrate which can be fed to animals or used as a food supplement in traditional foods.
The waste products of tomato - the skin and seeds - account for up to 38% of the raw fruit weight. The seeds are a good source of protein (15-22%) and oil (15-20%). In addition, they do not appear to contain anti-nutritional factors.
The methods used for extracting protein from the waste involve acid and alkali extractions. They require a stainless steel extraction tank, a centrifuge and a drier. To be economically feasible, they require a substantial supply of tomato waste products.
The first method of extracting protein involves removal of the oil which, after refining, can he used as an edible oil. After sun drying the waste, the skins are removed and the resulting seed meal is made alkaline (pH 11.5) and heated to 500°C. The mixture is then made acidic (pH 3.9) which causes the protein to precipitate. The extract is centrifuged to produce a tomato concentrate of more than 70% protein.
The second method does not involve removal of the oil. The extraction method is the same, but the product has a different composition - 28% oil and 47% protein.
The high-protein tomato concentrate has a deep red colour and can be used in a number of traditional dishes which contain tomatoes. It has also been used in sausages and other meat products, dairy products. snacks and also to fortify bread.