Biochemical changes during the ripening of Chorizo de cebolla, a Spanish traditional sausage. Effect of the system of manufacture (homemade or industrial)

Chorizo de cebolla is a dry-fermented sausage abundantly produced and consumed in Galicia (NW Spain). The gross chemical composition and the main physicochemical, proteolytic, lipolytic and fat autooxidative parameters were determined throughout the ripening process of seven homemade batches and four industrial batches. Samples from each batch of sausages were taken at 0 days (mix before stuffing), and after 2, 7, 14, 21, 28 and 42 days of ripening. Dehydration throughout ripening was more intense in the homemade batches, which showed final moisture and a w values lower than the industrial batches. In comparison to other varieties of chorizo and other similar raw-cured sausages, Chorizo de cebolla is characterised by high contents of fat and hydroxyproline and low contents of protein, NaCl and ash. In both systems of manufacture (homemade and industrial), a significant decrease in the pH values is observed until the seventh day of ripening (coinciding with the period of maximum degradation of the sugars), after which the pH was practically constant until the end of ripening in the homemade batches and showed a slight, but progressive increase after the 14th day in the industrial batches. The final pH values were lower than those reported for similar sausages. The different nitrogen fractions showed an increase during ripening and no significant differences in the final values, associated with the system of manufacture, were observed. The values of the nitrogen fractions show that proteolysis is particularly evident in the early stages of ripening, coinciding with the development of fermentation and a sharp decrease in pH. The acidity of the fat increases considerably during ripening in both systems of manufacture; however, the final values were among the lowest previously reported. The peroxide and TBA values evolved differently in the homemade and industrial batches. At the end of ripening, no significant differences associated with the system of manufacture (homemade or industrial) were observed in the peroxide value; however, the homemade batches showed significantly higher TBA values.