Extra virgin olive oil, virgin olive oil and mixed oil were analyzed by UV-Vis spectroscopy and Multivariate Curve Resolution with Alternating Least Squares (MCR-ALS). When the oils were heated at high temperatures (frying), oxidation products were formed which were harmful to human health and antioxidants present were degraded. The aim of this study was to evaluate tocopherol (an antioxidant present in oils) and the behaviour of oxidation products in different olive oil classes. MCR-ALS results showed that degradation started at 70 ºC for extra virgin olive oil, while tocopherol concentration decreased and oxidation products increased starting at 40 ºC in virgin olive oil. In mixed oil, commercialized as a mixture of 85% soybean oil and 15% olive oil, tocopherol concentration started to decrease and oxidation products increase at 30 ºC. The results suggested that extra virgin olive oil offered more resistance to increasing temperatures, while virgin olive oil and mixed oil were less resistant.
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The use of chemometric tools is progressing to scientific areas where analytical chemistry is present, such as food science. In analytical food evaluation, oils represent an important field, allowing the exploration of the antioxidant effects of herbs and seeds. However, traditional methodologies have some drawbacks which must be overcome, such as being time-consuming, requiring sample preparation, the use of solvents/reagents, and the generation of toxic waste. The objective of this study is to evaluate the protective effect provided by plant-based substances (directly, or as extracts), including pumpkin seeds, poppy seeds, dehydrated goji berry, and Provençal herbs, against the oxidation of antioxidant-free soybean oil. Synthetic antioxidants tert-butylhydroquinone and butylated hydroxytoluene were also considered. The evaluation was made through thermal degradation of soybean oil at different temperatures, and near-infrared spectroscopy was employed in an n-way mode, coupled with Parallel Factor Analysis (PARAFAC) to extract nontrivial information. The results for PARAFAC indicated that factor 1 shows oxidation product information, while factor 2 presents results regarding the antioxidant effect. The plant-based extract was more effective in improving the frying stability of soybean oil. It was also possible to observe that while the oxidation product concentration increased, the antioxidant concentration decreased as the temperature increased. The proposed method is shown to be a simple and fast way to obtain information on the protective effects of antioxidant additives in edible oils, and has an encouraging potential for use in other applications.
The Peruvian Maca (Lepidium Meyenii Walp) is a food which is widely consumed around the Peruvian Andes and has been used in Brazil thanks to medicinal properties attributed by popular culture. Due to lack of information on this cultivar, it was proposed a study to evaluate the effect of adding Peruvian Maca in transgenic soybean oil. For this purpose, the spectra of soybean oil samples with and without addition of Maca after heating at different temperatures were measured at Visible and Near Infrared regions. The results were evaluated by chemometric methods of Principal Component Analysis (PCA) and Multivariate Curve Resolution with Alternating Least Squares (MCR-ALS). The results suggest that Maca inhibits the appearance of oxidation products, which is evidenced when comparing the results obtained for the heated oil with and without addition of Maca.
Avocado and pequi oils were analyzed by UV-Vis spectroscopy and chemometric methods of curve resolution. When vegetable oils are heated at high temperatures, oxidation products are formed, which besides being harmful to human health strongly accelerates the antioxidants degradation. In this sense, monitoring antioxidants and oxidation products can provide information about the best conditions to its consumption. Therefore, this study aimed to evaluate antioxidants and oxidation products behavior in avocado and pequi oils. By applying Independent Component Analysis (ICA) in the avocado oil it was detected that antioxidant concentration decreased after 90°C. To the pequi oil, by applying Multivariate Curve Resolution Alternating Least Squares (MCR-ALS) it was possible to detect that the transformations between antioxidant/oxidation products took place at 70°C. The results suggested that avocado oil is more resistant to high temperatures then pequi oil. Moreover, the methods used in this study suggest that chemomstric tools are feasible to accomplish spectrophotometric techniques in food quality evaluation.
A fritura é um dos processos mais populares para finalidade de preparação de alimentos dado que promove rapidez e agilidade na cocção, além de permitir um ganho significativo referente as propriedades sensoriais, como sabor, aparência, textura e odor. As reações que ocorrem nos óleos e gorduras vegetais, induzidas pela presença de oxigênio, e especialmente acelerado por aquecimento, têm um impacto sobre a qualidade nutricional dos óleos com implicação para a saúde humana, com isso, a preocupação com a verificação da qualidade dos alimentos que são submetidos a este processo tem se intensificado. Nesse sentido, os objetivos deste estudo foram avaliar a qualidade e estabilidade oxidativa de óleo de soja e gordura de soja parcialmente hidrogenadas através da espectroscopia na região do ultravioleta e visível (UV-Vis) e da ferramenta quimiométrica de resolução multivariada de curvas com mínimos quadrados alternantes (MCR-ALS), além disso, a composição em ácidos graxos trans foi determinada por cromatografia gasosa. Os resultados obtidos sugerem que a gordura de soja apresenta maior resistência quando submetidos a ciclos de fritura do que o óleo de soja, porém a gordura de soja parcialmente hidrolisada também apresenta quantidade significativamente maior de ácidos graxos trans.
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