Toxin Production in Naturally Separated Liquid and Solid Components in Preparations of Heated Surface‐Ripened Cheese Inoculated with Clostridium botulinum

Abstract

SUMMARY Occasional solid‐liquid separation of soft surface‐ripened cheese packed into test tubes was examined for differences between the components with regard to growth and toxin production of Clostridium botulinum. Botulinum toxin was found in three tubes showing liquid‐solid separation; in each case the toxin was present in the solid but absent from the liquid cheese portion. Two mechanisms were found to be responsible for the peculiar distribution of toxin in liquid‐solid separated cheese: 1) the liquid portion possessed antimicrobial activity preventing the growth of C. botulinum whereas the solid component was antimicrobially inactive; 2) the particles in the solid cheese were able to adsorb botulinum toxin, thus preventing diffusion of preformed toxin into the liquid layer. Separation into a solid and liquid layer could be achieved deliberately by increase of the moisture content of the cheese preparation, or by mixing of thoroughly ripened cheese with relatively fresh cheese. However, in these tubes the toxin—when present—was distributed in essentially equal quantities in the adjacent solid and liquid components.

Toxicity of Spores of Clostridium botulinum Strain 33 A in Irradiated Ground Beef

“…The beef samples were homogenized in a tissue grinder and appropriate dilutions were made so that homogenized beef tissue was injected with the liquid into the mouse. This was thought to be necessary because botulinum toxin is known to be absorbed on food particles (Grecz & Dack, 1963). …”

Toxin Production by Clostridium botulinum in Shelf-Stable Pasteurized Process Cheese Spreads

“…In a study of the factors which inhibit growth of C. botulinum spores, the extent of inhibition was related to the level of free fatty acids in type I, aged, surface-ripened cheese, but fatty acids alone were not completely inhibitory (3). Some cheeses have been reported to be inhibitory by virtue of antibiotic substances produced in the cheese by the bacteria responsible for ripening (4,5,6).…”