Aspects of quality assurance in processing natural sausage casings

Abstract

Natural sausage casings are produced from the intestines of various species and used as edible containers for many different types of sausage around the world. Casings must therefore be fit for human consumption and must meet all food safety and hygiene requirements that apply to food of animal origin. As a hazard analysis of sausages would either focus on the final product or on the meat batter inside the casing, it becomes clear that many studies were done on sausages and only a handful on casings. Salt has been in use for centuries as the main preservative agent of casings and a study was done to determine whether this technique can meet the current microbiological criteria. Results indicate that the antimicrobial properties of salt used for the preservation of casings are sufficient to reduce the bacterial contamination (except for Clostridium spores) well below acceptable levels at a water activity level of 0.85 or lower during a 30-day storage period. To prevent the outgrowth of bacterial spores, additional preservation measures should be implemented. In the experiments described the use of the bacteriocin nisin was evaluated to reduce outgrowth of spores in desalinated casings. Additionally, the binding of nisin to casings, using 14C-labeled nisin Z and subsequent bioavailability of nisin were evaluated. Results demonstrate that nisin is bound to casings but if sufficient nisin was present the outgrowth of Clostridium spores in this model was reduced. Neural and lymphoid tissue can be regarded as marker tissues for the potential presence of Bovine Spongiform Encephalopathy (BSE) disease-specific prion protein (PrPPScP). These tissue types can also be present in cleaned beef casings. Based on the results from a quantitative histological analysis it was calculated that a standard 200 g sausage produced in beef casings contains 0.09 g lymphoid and 0.02 g neural tissue originating from the casing. Using these quantitative histological results a BSE infectivity risk - consumer exposure assessment was made, indicating that the potential risk when consuming a sausage produced in beef casings is far less than consuming a T-bone steak from the same animal. Casings are produced and shipped all over the world and this trans-global movement of casings means that restrictive measures, implemented to prevent the spread of contagious animal diseases, are also applicable. Two studies describe the efficacy of FMD and CSF virus inactivation in cleaned casings, either by salt (NaCl) or by using phosphate supplemented salt. After storage at about 20 C for 30 days, no remaining FMDV infectivity was found after either treatment, whereas casings stored at 4 oC still contained infectivity. CSFV infectivity was no longer present after treatment with phosphate supplemented salt and storage for 30 days at either 4 oC or 20 oC. To verify that phosphate supplemented salt was used, a commercially available phosphate assay kit was validated for the qualitative determination of phosphate present in treated casings without interference of naturally occurring phosphate in salt used for brines in which casings are preserved.