MICROORGANISMS IN FOODS 6 D CONTROL (shelf-stable cooked cured meats)

84 MICROORGANISMS IN FOODS 6 D CONTROL (shelf-stable cooked cured meats)

Summary

Significant hazards a r Cl. botulinum. r salmonellae.

r VTEC. r Staph. aureus.

Control measures

Initial level (H 0 )

r Selection of raw materials. r Microbial quality (spore load) of the raw ingredients. r Time and temperature from preparation to cooking

Reduction (ΣR) r Control of temperature and time during cooking and cooling. r Cooking and cooling rates and target internal temperatures.

Increase (ΣI) r Formulation (salt, nitrite and pH) to ensure multiplication is prevented. r Hermetically sealed packaging to prevent re-contamination. r Use water of appropriate quality. r Avoid manual handling of wet cans (risk of contamination if seals are

faulty). r Prevention of damage to container integrity and of post-cooking

contamination of contents.

Testing

r No routine microbiological testing of product is recommended. r Microbiological testing of some ingredients is a useful monitor of spore

load. r Routine examination of can seams is recommended.

Spoilage

r Selection of raw materials to avoid lots with many spore-formers. r Temperature and time of cooking and cooling.

a In particular circumstances, other hazards may need to be considered. Hazards to be considered. Food-borne illness has been traced to recontamination of the cooked

product during cooling, e.g. with S. typhi in contaminated, unchlorinated and cooling water. In general, the steps needed to ensure the microbial stability of shelf-stable cooked cured meats are similar to those for fully retorted “botulinum cook” meats.

XIII Snails

Snails are an important part of several food chains, surviving mainly on decaying vegetation and being consumed as food by fish and a variety of animals. Snails are considered a delicacy in many countries and are a staple part of the diet in parts of Asia where red meat and poultry are scarce sources of protein.

A Definition Many varieties of edible snails are used. However, the Moroccan snail (Helix aspersa) is especially

favored in Western European and Mediterranean countries and Helix pomatia in Central and Alpine

85 Europe (Andrews et al., 1975). The tropical species, Achtina fulica, is processed largely for African

MEAT AND MEAT PRODUCTS

and Southwest Asian markets.

B Production and processing Snails are usually obtained from swamps and marshes, may contain parasites and pathogenic bacteria

that they cannot purge. Several countries such as the UK and France are now raising snails by intensive farming in isolated trays, cages or pens (Daguzan, 1985; Runham, 1989). Snails are normally active only when feeding, and surround themselves with a membranous sheath while dormant (Andrews and Wilson, 1975). In the presence of moisture, they penetrate the sheath and emerge from their shells to forage for food. Snails that are imported are typically closely packed under conditions where there is ample moisture, hence the potential for cross-contamination is great. Snails inherently have high populations of indigenous bacteria and coliforms.

Fresh snails are usually eaten after cooking in hot water and prepared according to many regional recipes. Fresh or frozen snails are used as raw materials by the food industry for manufacturing traditional canned products. Ready-to-cook or cooked specialties such as snails in butter dressing with parsley and fricassee are being marketed. In addition, snail eggs prepared through an aromatic brining process are considered by some to be a gourmet delicacy (Pos, 1990).

C Pathogens Snails are vectors of many parasites, including Clonorchis sinensis, Eschinastoma ilocanum, Fasci-

ola hepatica, Fasciola gigantica, Fasciolopsis buski, Opisthorchis felineus and Paragonimus mester- mani (Bryan, 1977), and pathogenic bacteria. Surveys of both food and aquarium snails have revealed Salmonella is a frequent contaminant, being isolated from 62% of Achatina achatina (edible land snail) from Nigeria (Obi and Nzeako, 1980), 43% of H. aspersa from Morocco (Andrews and Wilson, 1975) and 27% of Ampullaria spp. (aquarium snails) from Canada and Florida (Bartlett and Trust, 1976). Salmonella contamination of snails occurs predominantly on the surface of the shell and snail meat, but the pathogen may also penetrate the snail flesh (Andrews and Wilson, 1975). In addition, A. hydrophila, Shigella and Arizona spp. were isolated from 72, 38 and 46%, respectively, of Achatina achatina from

Nigeria (Obi and Nzeako, 1980). High populations of coliforms (1.4 × 10 6 /g) and fecal coliforms (1.2 × 10 3 /g) have been found on aquarium snails (Bartlett and Trust, 1976).