The Bacteriology of " Pasteurized " Canned Hams*†

Abstract

THE large commercial losses caused by condemnation of spoiled consignments, -L complaints from consumers about the quality of outwardly sound material, and the identification of a &dquo; pasteurized &dquo; can of ham as the cause of an outbreak of salmonella food poisoning (Wildman, Nicol & Tee, 1951) have lately aroused considerable interest in Britain in the bacteriology of this product. Consequently, we have tried in this paper to review results obtained, in Britain, from the bacteriological examination of samples representing practically all the major producing countries outside America. Three separate, and rather different, investigations are here reported:(i) A routine examination of good commercial consignments, made to check general suitability for consumption, with particular emphasis on detection of faecal pollution and potential pathogens.(ii) A general investigation, on both sound and spoiled material, of the safety of such ham for human consumption, including a careful search for all potentially pathogenic types of bacteria of intestinal significance.(iii) A more thorough survey on a correspondingly smaller number of samples, from a chiefly ecological view-point, of the numbers and species of micro-organisms present in spoiled material. These groups of observations will be described separately, but they can best be understood if related to the normal flora of hams before canning which we shall first consider briefly.

Clostridium Perfringens Food Poisoning

“…Most market meats and poultry are heavily contaminated with C. per fringens (5,6,12,17,53,68,72,75,179,183,204). This is not surprising in view of the fact that the organism C. perfringens is ubiquitous and has been found in feces of humans (54,80,88,170,180,181,185,191) and animals (4,185,192), and in soil (169,174,185,196,203), water (169,201), and air (169).…”

The effect of sodium chloride, potassium nitrate and sodium nitrite on the recovery of heated bacterial spores *

“…Replicate 1-ml samples were placed in test tubes containing 10 ml Reinforced Clostridial Agar (RCA) (0x0 Ltd, London) containing varying amounts of sodium chloride, potassium nitrate or sodium nitrite. A black glass rod was added to facilitate subsequent counting of colonies (Ingram 8z Barnes, 1956) and, after solidification, the contents were sealed with a deep layer of agar containing the appropriate concentration of the salt. Incubation at 37°C was continued up to 14 days.…”

HEAT RESISTANCE and GROWTH CHARACTERISTICS OF MICROORGANISMS ISOLATED FROM SEMI‐PERISHABLE CANNED HAMS

“…Numbers and types of organisms are shown in Table 3. Ingram and Hobbs (8) found similar numbers of oragnisms and made complete identification of the cultures. The heat resistance coccus from the Eugon agar tubes was isolated and the thermal resistance determined at z = 9.…”