Evaluation of natural preservatives for use in a traditional South African sausage

[摘要] English: Boerewors is a popular dish in South Africa, and it is classified as a ground meat product. It is a fresh sausage product and the quality of the sausage is affected by the growth of microorganisms and oxidation spoilage. Boerewors is currently preserved with 450 mg/kg sulphur dioxide (SO2). The SO2 has antimicrobial, antioxidant and sensory properties in the boerewors but SO2 may also have negative effects on consumer health. Natural preservatives have become important in the food industry because consumers are moving away from consuming chemically preserved food. Rosemary extract is a natural preservative that has been shown to have antimicrobial and antioxidant properties. Another natural preservative that has been studied is chitosan which is a deacetylated form of chitin derived from the shell of crabs and shrimps and the cell wall of fungi and also has been shown to have antimicrobial and antioxidant properties. One of the aims of the study was to evaluate the microbiological quality of boerewors produced in different regions of Bloemfontein and comparing the quality of boerewors from small butcheries with supermarkets. The boerewors of 50% of the butcheries in Bloemfontein were subjected to microbial evaluation by using aerobic plate counts (APC), psychrotolerant plate counts (PPC), Enterobacteriaceae counts, coliform counts, yeasts and moulds counts and determination of the presence of Staphylococcus aureus and Escherichia coli. No Staph. aureus was found in any of the boerewors samples. The results of this study demonstrated that the microbial quality of boerewors sold in the different regions of Bloemfontein retail outlets did not differ significantly between the regions. The incidence of E. coli in the central region may indicate that the socio-economic status has an effect on the quality, though the socio-economic status was not investigated in this study. The significantly high coliform counts in boerewors purchased from the butcher shops indicate that poor hygienic conditions exist in butcher shops compared to the supermarkets. That may be related to staff being trained in hygienic practices in the corporate supermarket environment, while no training or very little training takes place in butcher shops. The second aim was to determine the effectiveness of rosemary extract, chitosan and fungi) and sulphur dioxide (SO2) as a conventional preservative, applied individually and in combination with each other, on improving the quality of boerewors. Eight boerewors treatments were formulated as follows: control (Con), 450 mg/kg SO2 (S), 260 mg/kg rosemary extract (Ros), 10 g/kg chitosan (Chi), 260 mg/kg rosemary extract + 100 mg/kg SO2 (Ros+S), 10 g/kg chitosan +100 mg/kg SO2 (Chi+S), 260 mg/kg rosemary extract + 10 g/kg chitosan (Ros+Chi) and 260 mg/kg Rosemary extract + 10 g/kg Chitosan + 100 mg/kg SO2 (Ros+Chi+S). Water activity (aw), microbial properties, colour stability, lipid stability and sensory analysis were conducted on the different sausage treatments. There were no significant differences between the aw of the different treatments. Chitosan and chitosan in combination with other preservative types had a significant effect (p<0.001) on reducing the total bacterial counts, coliforms and Enterobacteriaceae counts which were comparable to the results of the SO2 treatment. Chitosan, however, had a better effect on decreasing yeasts and moulds counts than SO2. Chitosan also showed good colour properties which were comparable to that of the 450 mg/kg SO2 preserved sausage. Rosemary extract showed a comparable lipid stability to those of the S treatment and it showed significantly (p<0.001) lower TBARS values when compared to the Chi treatment. The Ros treatment had a positive effect on the sensory taste of the sausages when compared to the Chi treatment, but the S treatment was still preferred by the sensory panel. The reduced level of 100 mg/kg SO2 showed good synergistic effects in combination with chitosan as antimicrobial, colour stabilizer and in combination with rosemary as antioxidant and improving the sensory score of the sausages.

[发布机构] University of the Free State