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Abstract: Vibrational spectroscopy (mid FTIR and FT-Raman) was used to monitor lipids extracted from hake fillets during frozen storage. Kramer shear resistance was used as a marker of texture changes and lipid damage was also investigated by following the development of conjugated dienes and free fatty acids by spectrophotometric methods. Results show that the intensity of the free fatty acid carboxylic ν(Ceasured by ATR-FTIR spectroscopy can be used for monitoring the development of lipid hydrolysis in hake lipids. Changes in the Raman ν(Ching region (1658cm−1 band), partially attributed to conjugated dienes development, were the only observed spectroscopic alterations related to lipid oxidation of hake lipids during frozen storage at −10°C. The high correlation of free fatty acids with instrumental texture and the disappearance of the ν as(PO2 −) band are consistent with membrane lipid hydrolysis being one of the factors directly related with toughening of lean fish flesh. [Copyright &y& Elsevier]

Free fatty acids (FFA) and lipid and protein oxidation changes during ripening were studied in Torta del Casar cheese. This cheese with protected designation of origin (PDO) is made from raw ewe milk and uses vegetable rennet. Cheeses were analysed at four different stages of ripening at 1, 30, 60 and 90 days. Most FFA significantly increased throughout maturation, except valeric and margaric acids. Acetic acid content increased during ripening and was the most abundant FFA in Torta del Casar cheese at the end of ripening. Short chain fatty acids (SCFA) showed an important increase throughout maturation, especially butyric, isovaleric and isobutyric acids. Lipid oxidation values significantly increased during the first month and decreased in the last 2 months of maturation; however, protein oxidation did not significantly change during ripening. Changes in FFA, especially SCFA, could have great importance in Torta del Casar cheese final characteristics; however, oxidative reactions did not play an important role. [ABSTRACT FROM AUTHOR]