The quality changes and the concentrations of tocopherols and c-oryzanol, during successive steps of rice bran oil refining (RBO), were studied. For this purpose, samples of crude, degummed, neutralized, bleached, dewaxed and deodorized RBO were taken from an industrial plant and analyzed. The moisture, pH, acidity, peroxide value and unsaponifiable matter, were determined. The fatty acid composition was evaluated by GC, and the concentrations of tocopherols and c-oryzanol were determined using HPLC with fluorescence and UV-Vis detection, respectively. To identify c-oryzanol components, fractions of the HPLC eluant were collected and analyzed using mass spectrometry. Oil refining reduced the peroxide value and acidity to 1 and 3% of the values obtained in crude RBO, respectively. The fatty acid composition were not significantly altered during refining. The concentrations of the tocopherols in RBO followed the order a [ (b ? c) [ d.The total concentration of tocopherols was 26 mg/100 g, and remained practically unaltered during refining. Up to nine components were distinguished in c-oryzanol. After collecting the elution fractions, up to six components were identified by electrospray mass spectrometry. Refining reduced the total concentration of c-oryzanol to 2% of its initial value.

The objective of this study has been to evaluate the stability of alpha-, (gamma+beta)-, and delta-tocopherols in rice bran oil chemically refined submitted to heating in a heater without air circulation and shielded from light, at temperatures of 100 degrees C and 180 degrees C. The collection of samples took place after 48, 96, 144, 192, 240, 336, and 432 h of heating and were stored in amber-colored flasks and frozen (-18 degrees C). The analyses of tocopherols took place in accordance with the method by Chen and Bergman (2005), with slight modifications, utilizing a system of high efficiency system of liquid chromatography. It was observed that the alpha-tocopherol is present at higher concentration in rice bran oil (328.4 mg/kg), followed by (gamma+beta)-tocopherol (99.1 mg/kg), and delta-tocopherol (7.7 mg/kg). The alpha-tocopherol in rice bran oil submitted to 100 degrees C showed a reduction of 28.65% at the end of 432 h of heating whereas when submitted to 180 degrees C temperature; its reduction was of 100% at the end of 240 h of heating. The contents of (gamma+beta)- and delta-tocopherol in rice bran oil at the end of 432 h of heating at 100 degrees C was of 79.9 and 6.4 mg/100 g, respectively.

Neste trabalho de revisão de literatura, a composição, a estabilidade, as aplicações e os benefícios à saúde do farelo de arroz foram abordados. Aspectos referentes à composição de biofenóis no óleo de arroz e novas tecnologias empregadas para extração e refino do óleo também foram discutidos. Subproduto do beneficiamento do arroz com amplas possibilidades de uso, o farelo evidencia grande potencial econômico. O consumo humano de farelo e óleo de arroz no Brasil ainda é reduzido, no entanto, a tendência do mercado mundial e as pesquisas apontam para promissoras aplicações desse produto.

Este trabalho teve como objetivo avaliar parâmetros de qualidade para os óleos de arroz e soja após sucessivas frituras. Doze lotes de 200 g de batata cortada tipo palito foram levadas à fritura em dois diferentes tipos de óleo (arroz e soja). Os métodos analíticos aplicados para avaliação da alteração nos óleos incluíram a determinação de ácidos graxos livres, índice de peróxido, antes e após a fritura. Efetuou-se a avaliação sensorial das amostras de óleo quanto aos atributos cor e odor após períodos pré-determinados de fritura, e avaliação sensorial das batatas quanto aos atributos cor, odor e sabor. O óleo de arroz apresentou maior estabilidade e menor interferência nas características das batatas durante os sucessivos processos de fritura. O óleo de soja evidenciou alterações sensoriais significativas na cor e odor a partir do quarto período de fritura e o óleo de arroz a partir do oitavo período. As alterações sensoriais de cor, odor e sabor das batatas ocorreram no oitavo período de uso do óleo de soja e acima da décima segunda vez de uso do óleo de arroz. PALAVRAS-CHAVE: ÓLEOS VEGETAIS -DEGRADAÇÃO; ÓLEOS VEGETAIS -ESTABILIDADE; ANÁLISE SENSORIAL.

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