BACTERIAL ADHESION TO SAUSAGE CASINGS - DEVELOPMENT OF A MODEL EXPERIMENTAL SYSTEM

An experimental system was developed to study bacterial adhesion to cooked sausages, using natural sheep casing, 100% collagen casing, or collagen-sorbitol-cellulose casing as model surfaces. Square pieces (c. 1 cm2) of the casings were inserted into specially designed flow chambers. Bacteria were introduced (c. 10(8) cfu ml-1) and allowed to sediment on the casings for 20 min. The chambers were then rinsed under controlled conditions (shear stress of 0.05 N m-2) and the remaining (adherent) bacteria were stained and enumerated under light microscopy. Typically, Brochothrix thermosphacta cells adhered to casings in large numbers (c. 10(5) cfu cm-2), regardless of the casing type and mode of rehydration (30 min in water or 5 min in a 10% NaCl solution; room temperature). A Lactobacillus sp. was found to adhere to the casings in lower numbers (c. 10(4) cfu cm-2) and this was due to a low level of sedimentation rather than to weak adhesive properties. Preliminary results indicate that the method developed will be applicable to pieces of casings peeled from cooked sausages.