Radiation preservation of meat and meat products: A review.

The World Health Organisation (WHO) in 1980 clarified the position regarding the medical acceptability of irradiated foods when it said'…no health hazard results from consuming any food irradiated up to a dose of one megarad (1 Mrad)'. This resulted in renewed interest in irradiation as a cost-effective alternative to traditional preservation methods such as canning and freezing. Thus, radurisation (the application of ionising radiation at a dose level which substantially reduces the microbial population) increases the shelf life of poultry, comminuted meat and meat dishes significantly. Low dose irradiation, or radicidation, eliminates parasites such as Trichinae and cysticerci in pork and, very importantly, salmonella organisms in poultry and red meat. Therefore, irradiation has an important rôle to play in public health protection. High dose irradiation, or radappertisation ('cold sterilisation'), uses doses in excess of 1 Mrad and is analogous to retorting as understood in the canning industry. However, it can adversely affect quality in producing 'free radicals' in high protein foods such as meat. To prevent this, special precautions are necessary, e.g. irradiation is conducted at very low temperatures and the product is usually vacuum packed. A further potential use of irradiation is its ability to reduce the quantity of nitrite necessary in cured meats. This may become of practical significance if legislation further reduces the amount of nitrite permitted in these products.

An in vitro effect of ascorbate on the spontaneous reduction of sodium nitrite concentration in a reaction mixture.

Nitrite is known to react with free amines to form nitrosamines which may have carcinogenic activity. The present study provides evidence showing that addition of ascorbic acid in a reaction mixture results in a spontaneous decrease in nitrite concentration. The nitrite lowering effect of ascorbic acid appears to correlate with the rate of oxidation of the vitamin to dehydroascorbic acid, suggesting that ascorbic acid may be involved in the reduction of nitrite to nitrogen oxide.

Number and distribution of bacteria on some beef carcasses at selected abattoirs in some member states of the European communities.

In seven member countries of the European Communities, three abattoirs were visited on three occasions in each of two surveys and at each visit ten beef carcasses were sampled, before chilling, at defined sites on the neck, brisket, forerib and medially on the round. In Survey I, samples were plated for total viable count (TVC) at 30° (ISO 2293) and Enterobacteriaceae at 37° (ISO 5552); in Survey II only TVCs were made. This paper is confined to analyses of the TVCs in the two surveys. Data from each country were analysed separately as sampling methodology may not have been sufficiently reproducible by different workers to allow between-countries comparison. Variations among visits to particular abattoirs and abattoir × site interactions made comparisons among abattoirs invalid within five of the seven countries. To effectively monitor differences between abattoirs within most countries it would be necessary to make more than three visits to each abattoir. Despite abattoir × site interactions in three countries in Survey I and four countries in Survey II, comparisons between sites were generally valid because of the consistent high contamination of the brisket. In the remainder of countries the abattoir × site interaction was too large to allow valid comparisons between sites. It is recommended that at least three or four sites are sampled in future surveys as only one site per carcass would underestimate the number of more heavily contaminated carcasses.

Cold water, ultra-high pressure cleaning of abattoirs.

Cold water (10 degrees C) at ultra-high pressure (38-5--49 kg/cm2) was compared with (a) hot water 65-6--82.2 degrees C) at low pressure (4-2--5-6 kg/cm2) and (b) hot water containing a detergent (2% (w/v) sodium silicate). Seven sites were examined in a beef abattoir and six in a bacon factor. Three surfaces in the beef abattoir had lower residual colony counts (higher reductions) after hot water/low pressure than after cold water/high pressure. However, the differences were not significant (P greater than 0-05). The range of the mean log10 count/cm2 before cleaning was 4-02-5.15, and after cleaning 1-73-2.32 (hot water) and 1-9--2-85 (cold water). On three of the remaining sites, the three methods were compared. The total differences between treatments were not significant (P greater than 0-05), although there was an effect of surface and an interaction between surface and treatment. The cold water produced lower residual counts on three sites in the bacon factory than the hot water (45--54 degrees C). However, the differences were not significant on the remaining surfaces.

A note on the hygiene of meat mincing machines.

Two mincing machines were cleaned by different methods, i.e. (a) a detergent/sterilizer method and (b) scrubbing parts in boiling (98.8 degrees C.) water. Initial results indicated that, on reassembly, post-treatment contamination took place. Efforts to clean each machine as consisting of two distinct parts, (a) the casing and (b) removable parts, were more satisfactory. Four other mincers which could be completely dis-assembled were satisfactorily cleaned, but only in terms of percentage organisms surviving and not in terms of actual numbers surviving.

Sources of contamination of cooked, ready-to-eat cured and uncured meats.

Forty-five samples of unsliced, cooked, ready-to-eat meats on sale in retail premises and supermarkets were examined. Thirty-six (80%) had Escherichia coli I and 21 (47%) had coagulase positive staphylococci in numbers ranging from 1 to > 1000/100 cm.(2). Twenty-one samples contained Clostridium spp. in numbers from 1 to > 100/100 cm.(2). Of the 45 samples tested, 11 (factory-produced) and 7 (home-produced) were examined after cooking but before being offered for sale. Cooked hams were contaminated after handling in a factory, as were samples of canned corned beef after sale and exposure for 24 hr. Some sources of contamination were: (a) raw beef, (b) factory and shop surfaces and equipment, and (c) workers' hands. Curing brines used in retail shops and supermarkets to produce corned beef were a potent source of contamination. The effect of holding cooked meats at ambient temperature on their spoilage (22 degrees C) and food-poisoning (37 degrees C) microflora was demonstrated.

The fate of a toxigenic strain of Staphylococcus aureus in vacuum-packaged bacon.

Pork was cured by (a) the Wiltshire method and (b) a hygienic sweet cure process. Representative samples of both bacons were inoculated at ;low' density (10(3) organisms/g.) and ;high' density (10(6) organisms/g.) with a toxin-producing strain of Staphylococcus aureus, ;High' and ;low' density samples of both bacons were each stored at 5 degrees C. for 42 days and 15 degrees C. for 21 days.Results indicated that the test organism at high inoculum density grew slowly in both bacons at 5 degrees C. The organism survived at 5 degrees C. in both ;low density' bacons. At 15 degrees C. the test organism grew; growth being more pronounced in the ;hygienic' than in Wiltshire bacon.

An evaluation of the efficiency of cleaning methods in a bacon factory.

The germicidal efficiencies of hot water (140-150 degrees F.) under pressure (method 1), hot water + 2% (w/v) detergent solution (method 2) and hot water + detergent + 200 p.p.m. solution of available chlorine (method 3) were compared at six sites in a bacon factory. Results indicated that sites 1 and 2 (tiled walls) were satisfactorily cleaned by each method. It was therefore considered more economical to clean such surfaces routinely by method 1. However, this method was much less efficient (31% survival of micro-organisms) on site 3 (wooden surface) than methods 2 (7% survival) and 3 (1% survival). Likewise the remaining sites (dehairing machine, black scraper and table) were least efficiently cleaned by method 1. The most satisfactory results were obtained when these surfaces were treated by method 3.Pig carcasses were shown to be contaminated by an improperly cleaned black scraper. Repeated cleaning and sterilizing (method 3) of this equipment reduced the contamination on carcasses from about 70% to less than 10%.