USED FOOD OILS: PHYSICAL-CHEMICAL INDICATORS OF QUALITY DEGRADATION
DOI:
https://doi.org/10.25746/ruiips.v5.i2.14504Keywords:
óleo alimentar usado, parâmetros físico-químicos, used food oil, physical-chemical parametersAbstract
O óleo alimentar usado (OAU) constitui um resíduo, mas pode ser valorizado para fins não alimentares. Contudo, o controlo de qualidade pode incorrer em análises dispendiosas, impraticáveis. Neste projecto, perspectivou-se seleccionar Indicadores de Degradação da Qualidade (IDQ), parâmetros físico-químicos que sinalizem defeitos, com rapidez, rigor e baixo custo. OAU´s de uso real (fritura industrial), ou de degradação induzida em laboratório (testes de fritura e de estabilidade), foram analisados através dos parâmetros: teor de Humidade, aw, Acidez Total, Índice de Peróxidos, Índice de Iodo, Cor (CIE, CIELab), Absorvência no UV, Compostos Polares Totais e análise microbiológica.Validaram-se procedimentos internos, pois o normativo não permitiu obter resultados fiáveis em todo o ciclo de vida dos OAU´s, cujo perfil se altera com o tempo e reutilização em fritura.Os resultados obtidos mostram diferenças significativas com indicadores de resposta rápida: Acidez Total, Índice de Peróxidos e cor CIELab perfilam-se como IDQ´s; IndI e AbsUV como métodos de referência. Humidade, aw e cor CIE revelaram-se inadequados.
ABSTRACT
Used food oil (UFO) is a residue, but can be recovered for non-food uses. However, quality control applied to UFO’s, may result into inappropriate expensive analysis. This project aimed to identify physicochemical parameters for further implementation as UFO´s Quality Degradation Indicators (QDI), evidencing defects, inexpensively, quickly and accurately. UFO´s analysis was tested on the use, for industrial frying, and by degradation induced in laboratory (frying and heat stability tests) by following parameters: moisture, aw, total acidity, peroxide index, iodine index, colour (CIE, CIELab), UV absorbency, total polar compounds and microbiological indicators. Internal procedures were validated, as standards did not provide reliable results for oil´s entire life cycle, whose profile changes with time and frying reuse. Results demonstrate significant differences with quick response parameters: total acidity, peroxide index and CIELab colour, outlined as QDI’s. Iodine Index and UV Absorbency were profiled as reference methods. Moisture, aw and CIE colour proved to be inadequate.
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