Valorização do tomate. Extracção supercrítica de compostos bioactivos a partir de repiso de tomate

Mestrado em Engenharia Alimentar - Instituto Superior de Agronomia

Lycopene is a carotenoid present in high concentration in tomatoes and tomato products, along with lesser amounts of α - carotene and β-carotene. It is found predominantly in the chromoplasts of epicarp. This pigment is the principal component responsible for characteristic deep-red color of tomato and has attracted attention in different fields of research. Lycopene is considered to be a commercially important natural pigment for the emergent market of nutraceutical products due to its function as a health-promoting ingredient. The acyclic structure with 13 double bonds, 11 of which are conjugated, determine its high antioxidant activity. The singlet oxygen-quenching properties of lycopene and, thereby, its ability to trap peroxyl radicals result in the reduction of the risk of developing atherosclerosis and coronary heart disease. Moreover, there are also a rising number of clinical evidences and epidemiological studies supporting the role of lycopene to provide protection against different types of cancer, such as prostate gland cancer, stomach cancer, and lung cancer. Evidence is now being obtained that suggests that lycopene may have direct stimulatory effects on the response of the immune system. Lycopene is known to exist in a variety of geometric isomers, including all-trans, mono-cis and poli-cis forms. The all-trans configuration predominates in fresh tomatoes and gradually isomerizes to Cis configurations upon processing and storage of tomato products. The tomato processing industry produces large amounts of solid waste that contain highly valuable biologically active compounds, including lycopene and other carotenoids. Recycling this by-product is of interest for an environmental and economical viewpoint and for the health benefits derived from the recovery of bioactive compounds now discharged. Every year, Portugal discharges approximately 55000 tons of tomato processing wastes. The fact that this waste are rich in skins and, consequently, in lycopene makes tomato industrial waste a suitable source of this carotenoid and its extraction a good alternative use for this by-product. Typically, carotenoids and lycopene are extracted from foods by solid-liquid extraction, which consumes large volumes of organic solvents. Organic solvents are expensive, hazardous to use, and costly to dispose off. Concern about the environment has increased interest in alternative and reliable extraction techniques such as supercritical fluid extraction. Its non-toxicity and non-flammability are at least two reasons why carbon dioxide is the supercritical fluid in most common use. In addition, its low critical temperature thatallows its use to extract thermally labile compounds such as carotenoids and the lack of solvent residues are also huge advantages. The main objective of the present work is to contribute for the study of supercritical carbon dioxide extraction of lycopene. The effects of extrusion (as pre-treatment), time of extraction and particle size on the extraction yield were evaluated. The experiments were carried out at a pressure of 220 bar and a temperature of 45ºC, without any modifiers The extracts were analyzed for lycopene, α-carotene and β-carotene content using highperformance liquid chromatography, and compared to a chemically extracted control. The results indicated that, after 990 minutes of extraction, higher extraction yield of lycopene, α - carotene and β - carotene were obtained with tomato industrial wastes lyophilized, ground and no extruded. However, when compared with solid-liquid extraction, supercritical carbon dioxide extraction gave extraction yield lower. The extrusion didn´t have a significant effect in the solid-liquid extraction.---------------------------------------O presente trabalho centrou-se na extracção por CO2 supercrítico de licopeno, a partir de repiso de tomate, para posterior uso na indústria alimentar. Os estudos de extracção foram efectuados a uma pressão de 220 bar, temperatura de 45ºC e sem adição de co-solventes. Foi testado o efeito do tempo de extracção e da granulometria das partículas, no rendimento da extracção. Foi ainda avaliado o efeito da aplicação de um tratamento prévio de extrusão no rendimento de carotenóides. Os extractos foram posteriormente analisados quanto ao seu teor em licopeno, α-caroteno e β-caroteno e os resultados obtidos foram comparados com os alcançados na extracção por n-hexano. Os resultados indicaram que, após 990 minutos de extracção, rendimentos de extracção superiores em carotenóides foram obtidos com repiso de tomate liofilizado moído e não sujeito a extrusão prévia. No entanto, quando comparada com a extracção por solventes orgânicos, a extracção por CO2 supercrítico nas condições testadas continua a conferir rendimentos de extracção mais baixos. A extrusão não implicou efeitos significativos no rendimento de extracção.