Lebrón-Bosques, Lizbeth

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    Efecto de diferentes concentraciones de vitamina c (ácido l-ascórbico) en el desarrollo de rancidez oxidativa en filetes de tilapia (Oreochromis niloticus) congelados
    (2006) Lebrón-Bosques, Lizbeth; Díaz-Morales, Emilio; College of Agricultural Sciences; Kubaryk, John; Negrón de Bravo, Edna; Department of Food Science and Technology; Muñoz, Miguel A.
    The presence of long chain omega-3 polyunsaturated fatty acids in tilapia is of great nutritional benefit for people eating it, but double bonds present in fatty acids make them very susceptible to deterioration caused by lipid oxidation, which can cause the development of off- flavors. The objective of this research was to evaluate the effect of different concentrations of ascorbic acid in the development of oxidative rancidity in tilapia (Oreochromis niloticus) fillets stored at -18°C for a 6 month period. The ascorbic acid was added in the following concentrations: 0 ppm (control), 5 ppm, 500 ppm and 50,000 ppm (5%). The samples were taken monthly and the development of oxidative rancidity was evaluated by: 1) thiobarbituric acid- reactive substances (TBARS) determination, 2) fatty acid composition determination by GC-MS, 3) quantification of hexanal and identification of volatiles by SPME/GC-MS and 4) sensory evaluation. The vitamin C content did not change through the storage period in any of the treatments. TBARS values showed that the highest concentration of vitamin C (50,000 ppm) had a protection effect against rancidity. The fatty acid composition remained constant throughout the research therefore this analysis did not show any effect of the treatments of vitamin C used in fatty acid oxidation. The average of hexanal content between treatments suggested that 5 ppm and 50,000 ppm of vitamin C treatments had antioxidant effects in the fillets. There was a lower development of volatiles through the storage time in the treatment with the highest concentration of vitamin C (50,000 ppm), which suggests an antioxidant effect. Panelists in the sensory analysis found a less rancid taste in those samples containing 5 ppm and 50,000 ppm ascorbic acid, compared to a more rancid taste found in the control and 500 ppm. The results suggested that 50,000 ppm of ascorbic acid concentration was more effective than other treatments inhibiting lipid oxidation in frozen tilapia fillets. The study of oxidative rancidity in tilapia is difficult due to the low fat content of this fish and the high reactivity of the oxidation products. The rancidity developed in tilapia during the 6 months of frozen storage was minimal, non detectable, and did not affect the quality of the product. This suggests the use of antioxidant in tilapia is not necessary to extend the shelf life of tilapia fillets as long as frozen storage is less than the 6 months used in this study.