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Summary: Lipid degradation caused by lipolysis and oxidation plays an important role in the evolution of final product quality of cured silver carp. This study aimed to determine the impact of exogenous lipase (ExL) on lipolysis and lipid oxidation during the wet‐curing and dry‐ripening of silver carp inoculated with mixed starter cultures. The addition of ExL to silver carp increased the hydrolysis of total lipids and phospholipids. The free fatty acids (FFAs) content during wet‐curing was significantly higher in the ExL‐treated group compared with the control. Increased FFA accumulation contributed to a high level of conjugated dienes, peroxides and thiobarbituric acid‐reactive substances in the ExL‐treated group, indicating that the lipid oxidation was improved by the addition of ExL. Increased neutral lipase, acid lipase and phospholipase activities during the wet‐curing stage might explain the more extensive release of FFAs in the presence of ExL. The addition of ExL promotes the hydrolysis and oxidation of lipids in cured silver carp. [ABSTRACT FROM AUTHOR]

In order to investigate the generation of aroma in Chinese bacon (unsmoked), the changes of lipolysis, lipid oxidation, and volatile compounds derived from lipid oxidation (VCDFLO) during processing were analyzed. The results showed that acid lipase activity decreased during the entire process, while neutral lipase and lipoxygenase (LOX) increased from raw meat to the 1 day of dry-ripening then decreased. Phospholipase increased during dry-curing then decreased during dry-ripening. Thiobarbituric acid reactive substances increased from raw meat to the 7 days of dry-ripening thereafter decreased. Total free fatty acids increased at the end of 1 day of dry-ripening and decreased subsequently. Thirty-five VCDFLO were identified; the total peak area of these compounds increased by almost double at the 4 days of dry-ripening than raw meat and indicated 47.37-50.85% of total 78 volatile compounds in the final products. In conclusion, VCDFLO generation was attributed to lipid-related enzymes and contributed mainly to the aroma. Practical applications: Chinese bacon (unsmoked) usually produced from high intramuscular fat pork has more intense and long-lasting aroma, since intramuscular triglycerides are good precursors for most volatile compounds. Understanding the mechanism of aroma formation related to lipid oxidation could help us to improve the product quality and optimize the duration of processing. Therefore, the present work identified the characteristic flavor compounds and provided the changing regularity of these compounds at various stages to facilitate the generation of them by regulating lipases and lipoxygenase (LOX) activities. The work showed that neutral lipase and lipoxygenase (LOX) played important roles during dry-curing and dry-ripening. The regulation of lipases and LOX activities can facilitate the generation of volatile compounds of Chinese bacon (unsmoked). [ABSTRACT FROM AUTHOR]

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]