The thermal stability of some commercially available antioxidants alone or in binary or ternary mixtures was investigated in order to find the optimal combination of antioxidants for food processing. The synthetic antioxidants used were butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PG) and tertiary‐butyhydroquinone (TBHQ). Other antioxidants such as ascorbyl palmitate (AP), mixed tocopherols (TOCO) and monoacylglycerol citrate (MGC) were also employed. The effectiveness of these antioxidants and their combinations was assessed using the Rancimat test by measuring the induction period for the oxidation of sunflower oil after heating at 180C for 1 h and comparing it to the oxidation kinetics of the oil without added antioxidants. All antioxidants and their binary or ternary mixtures showed different degrees of thermal instability. TBHQ individually, among all the examined antioxidants, showed the highest thermal stability. On the other hand, AP as an antioxidant in sunflower oil exhibited low stability during heating. The thermal stability of AP could be enhanced by the addtion of BHA or BHT in binary mixtures at a ratio of 1:3 (w/w). In addition, the ternary mixture of AP, TOCO and MGC (65:25:10) in sunflower oil also showed a higher stability to thermal inactivation. However, the ternary mixture containing 0.13% AP, 0.05% TBHQ and 0.02% MGC provided the optimal protection during thermal treatment. Although a combination of 0.13% BHT, 0.05% AP and 0.02% MG was very effective synergistically at room temperature, it showed a higher susceptibility to thermal inactivation. It was

Palm olein with 22.9 h of stability at 100 C (by the Rancimat method) and low acid and peroxide values of 0.184% and 1.33 meq/kg, respectively, was used to study the deteriorative effect of frying of frozen prefried potatoes and chicken and compared it with the effect of frying the same fresh foods. Quality characteristics of palm olein were monitored by following the changes in physical and chemical properties; foam height (FH), smoke point (SP), refractive index (RI), viscosity (Vis), acid value (AV), peroxide value (PV), polymer content (%Pol.), oxidized fatty acids (%OFA), thiobarbituric acid (TBA) value and, conjugated acids (absorbance at 232 nm for conjugated dienes and at 268 nm for conjugated trienes) with the progress in frying time of up to 20 h. Results revealed that frying the frozen prefried foods express more deteriorative effect than the fresh foods throughout the frying process.

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RESUMENMejora del valor nutricional y tiempo de almacenaje de patatas fritas en presencia de vitaminas con actividad antioxidante.Mediante la adición de antioxidantes sintéticos y naturales, como TBHQ, retinil palmitato y ascorbil palmitato, es posible aumentar la estabilidad de aceites para la fritura comercial. Los resultados indican que TBHQ, seguido de retinil palmitato y ascorbil palmitato, en este orden, es el mejor para retrasar el deterioro de las condiciones para la fritura, 24 h a 180 o C, de patatas fritas cuando se compara con un control sin aditivos.Se tomaron muestras de patatas fritas en aceites con y sin vitaminas antioxidantes durante las primeras 8 horas de fritura, y se dividieron en tres porciones para someterlas a diferentes tratamientos: 1) sin aditivos (muestras control de patatas fritas con aceite control o con aceite que contenía TBHQ, retinil palmitato o ascorbil palmitato; 2) enriquecimiento de las cuatro muestras anteriores con vitamina E (tocoferol) mediante la inmersión de las patatas fritas en aceite con 0,1% tocoferol; y 3) enriquecimiento de las muestras anteriores con vitamina C mediante la dispersión de una mezcla de sal fina y ascorbil palmitato sobre la superficie de las patatas fritas y agitación de las mismas en el interior de paquetes. Las muestras controles y enriquecidas se empaquetaron en paquetes de aluminio y fueron guardadas en un horno eléctri-co a 63 ± 1 o C. La estabilidad de las patatas fritas a 63 ± 1 o C aumentó en presencia de vitamina E y de vitamina C antes del empaquetamiento y almacenamiento a esa temperatura.Las patatas fritas con aceite enriquecido en vitaminas A, C y TBHQ fueron las que mejor se conservaron a 63 o C; este efecto se prolongó mediante la adición de vitaminas E ó C después del proceso de fritura y antes de su almacenamiento a 63 o C en paquetes de aluminio. Estos resultados demuestran el efecto sinér-gico de vitaminas con actividad antioxidante que pueden actuar de manera independiente o complementaria a TBHQ, el cual además las protege en estas condiciones termo-oxidativas. PALABRAS-CLAVE: Patatas fritas-Antioxidantes-Vitaminas. SUMMARYFortification of fried potato chips with antioxidant vitamins to enhance their nutritional value and storage ability.The frying shelf life of commercial frying oil was increased by the addition of synthetic and natural antioxidants, e.g. TBHQ, retinyl palmitate and ascorbyl palmitate (antioxidant vitamins).The results revealed that TBHQ had the best effect in retarding the deteriorative effect of frying conditions throughout 24h of frying potato chips at 180 ± 1 0 o C followed by the effect of retinyl palmitate and the effect of ascorbyl palmitate compared to the control without any additives.Fried potato chips in oils either with or without antioxidant were collected during the first 8h of frying, divided into 3 main portions each portion had different treatment; 1) without any additives (control samples for fried potatoes resulting from the control oil or from oil containing TBHQ or containing retinyl or ...