Microbial Quality and Preservatives in Manufactured Meat Products
In this section:
Microbial Quality and Preservatives in MANUFACTURED MEAT PRODUCTS
July September 1996
Report Prepared by Simon Rockliff, Geoff Millard and Andrew Rigg
1.1 To determine the bacteriological status of fermented meat products available on the ACT market.
1.2 To determine the compliance of manufactured meat products available on the ACT market to the Australia New Zealand Food Authority (ANZFA) Food Standards Code (the Code).
The samples for this survey were analysed by both the Microbiology and Food Chemistry units of the ACT Government Analytical Laboratory (ACTGAL) with the aim of providing a more holistic picture of the quality of manufactured meat products available on the ACT market. Additionally, testing of manufactured meat products for nitrite or preservatives had not been conducted by ACTGAL for a number of years and it was considered appropriate to investigate products for these analytes during this survey.
Meat products of this type have been implicated in several major food poisoning events
- in Australia. Examples of major outbreaks were a Salmonella outbreak in the 1980s and an outbreak in 1995 causing Haemolytic Uraemic Syndrome (HUS) as a result of E. coli O111 contaminated Mettwurst. There are other pathogens that can possibly cause a problem with this type of product. Three such pathogens were tested in this survey, namely, Listeria monocytogenes (L. monocytogenes), Bacillus cereus (B. cereus) and Clostridium perfringens (C. perfringens). The Food Standards Code has a Coagulase positive Staphylococcus (Coag+Staph) for Uncooked Fermented Meat.
Regarding the chemical composition of these foods, the addition of nitrite has two functions in meat products:
- as a food preservative, in particular for inhibiting the growth of the bacterium Clostridium botulinum, the bacterium responsible for botulism; and
- as a curing salt.
Nitrite has been known to cause nausea and vomiting, dizziness, headaches, de-oxygenation of the blood, low blood pressure and collapse of the circulatory system. Nitrite also forms small amounts of nitrosamines which have been shown to be carcinogenic in animals, but not in humans. Products containing nitrite are prohibited for sale in foods for babies and young children.
Preservatives are used to inhibit the growth of yeasts, fungi and bacteria and so play an important role. Commonly used are sorbic and benzoic acid, along with their sodium, calcium and potassium salts. These compounds have been known to cause allergic reactions in those persons who suffer from asthma.
3. Food Standards
Standard C1, part 8, subclause 34(1) Manufactured Meat defines manufactured meat that is prepared from a blend of meat and other foods including water, and includes
(a) smallgoods such as frankfurters, saveloys, brawn, devon, strasburg, salami, meat paste, chicken roll, and similar foods; and
(b) extended muscle products.
Manufactured meat may be divided up into one of the following categories
(1) Cooked Manufactured Meat;
(2) Uncooked Fermented Manufactured Meat; and
(3) Semi-dry Heat-treated Manufactured Meat.
3.1 Chemical Standards
Standard C1, part 8, subclause 36(1) states that manufactured meats may contain not more than 125 mg/kg in total of nitrites and nitrates, calculated as sodium nitrite, except as specified in subclause 38(1).
3.1.1 Cooked Manufactured Meat
Clause 37 states that cooked manufactured meat may contain not more than 260 mg/kg of sulfur dioxide.
3.1.2 Uncooked Fermented Manufactured Meat
Subclause 38(1) states that uncooked fermented manufactured meats may contain added potassium nitrate, sodium nitrate, or a mixture of these provided that the uncooked fermented manufactured meat contains not more than 500 mg/kg in total of nitrites and nitrates, calculated as sodium nitrite.
Subclause 38(2bii) states that uncooked manufactured meat may contain not more than 1.5 g/kg, calculated as sorbic acid, of added sorbic acid, its sodium or potassium salt or a mixture thereof applied to the surface of the food.
These products are referred to as uncooked samples in this report.
3.1.3 Semi-dry Heat-treated Manufactured Meat
Clause 39 states that semi-dry heat-treated manufactured meat may contain 1.5 g/kg, calculated as sorbic acid, of added sorbic acid or its sodium or potassium salt or a mixture of these in the final product.
These products were treated as cooked samples because of the difficulty in determining whether they are cooked or semi-dry heat-treated and because they have the same Maximum Permitted Concentration (MPC) for nitrite as cooked manufactured meats of 125 mg/kg.
3.2 Microbial Standards
Standard C1, Part 13, subclause 60, states that Uncooked Fermented Meat products must:
(a) have a coagulase-positive Staphylococci count not exceeding 1,000 coagulase-positive Staphylococci per gram as examined by Method 3.2 in the schedule;
(b) be free from Salmonella in 25 g of the food when examined by Method 4 in the schedule; and
(c) in the case of an uncooked fermented comminuted meat product to which clause 60A applies, after fermentation or any other process, be free from Escherichia coli (E. coli) in 0.1 g of the food when examined by Method 9 in the schedule.
4.1 Summary of Samples Collected
There were 67 samples collected from supermarkets and stores around Canberra from July to September 1996.
The samples were from 12 different manufacturers, consisting of salami, cabanossi, and other manufactured meat products, purchased from 12 different establishments. The greatest proportion of samples were salamis with 15 different types being collected.
4.2 Microbiological Analysis
All of the samples were analysed for coagulase-positive Staphylococci, Salmonella, E. coli and L. monocytogenes.
47 of the samples were tested for B. cereus and C. perfringens.
In order to adequately collect samples of the myriad of types of product available on the ACT market, the survey examined one sample consisting of one subunit of each product. No sample consisted of five subunits as required by the Code.
The Table 1 gives the range of results obtained for each test organism:
|L. monocytogenes||< 3#|
|E. coli||< 25# (Two samples positive One sample 2 the other 5)|
|B. cereus||< 50#|
|Coagulase positive Staphylococcus||< 50#|
|C. perfringens||< 50#|
# Range expressed in terms of colony forming units (cfu) per gram. Range expressed in terms of isolated / not isolated in 25 grams.
4.3 Chemical Analysis
52 samples were tested by the Food Chemistry Unit for nitrite, nitrate, and the preservatives, sorbic and benzoic acid. The samples were split into the categories of cooked or uncooked manufactured meat products with the percentages of each category type summarised in the above chart.
4.3.1 Summary of Nitrite Results
The chart shows that 12% of the samples failed the MPC for nitrite. 56% of the samples passed the MPC for nitrite whilst still containing nitrite and 33% of the samples did not have nitrite detected.
The charts show that:
- all of the samples that failed the MPC for nitrite concentration, 35% were from the category of cooked manufactured meat products;
- there is a significant proportion of samples in both categories that did not have nitrite in them at all, 24% for the cooked samples and 37% for the uncooked samples; and the largest proportion in each category are those samples which have nitrite in them but have passed the Code requirements.
The highest failure for the cooked samples was at 195 mg/kg, over 50% above the MPC of 125 mg/kg. Four samples did not claim nitrite on their labels, however, one of these products did contain nitrite.
4.3.2 Summary of Preservative Results
The laboratory analysed for the presence of the preservatives sorbic and benzoic acids in all of the samples. The chart shows:
- that none of the samples failed the Code requirements and only 17% of samples contained the preservative sorbic acid.
- that none of the samples contained the preservative benzoic acid.
One sample from the cooked category contained sorbic acid at a concentration of < 0.010 g/kg, whereas the uncooked samples contained the highest concentration of sorbic acid at 0.058 g/kg, well within the limits of the MPC of 1.5 g/kg.
None of the samples was analysed for sulfur dioxide, although one product did claim it on their label. The product that claimed preservative, claimed the presence of sulfur dioxide.
Salmonella, Listeria monocytogenes, Bacillus cereus, Clostridium perfringens and Coagulase positive Staphylococcus were found to be below the methods detectable limits for all samples.
Low numbers of E. coli were detected in two of the samples collected from the same establishment on the same day. These samples were blister packs prepared on the premises
There appears to be good overall compliance with the Code for nitrite levels in the manufactured meat products with a total of only 12% of samples failing to comply.
All samples that failed the nitrite MPC were from the category of cooked meat products, a total of 35%. Due to the small number of samples received in this category, it is difficult to decide whether this is a significant problem. It is interesting to note as a comparison that 24% of the samples in this category did not have nitrite detected and a further 41% of the samples, whilst containing nitrite, passed the MPC of 125 mg/kg, making a total of 65% of samples complying with the Code.
The category of uncooked fermented manufactured meat had excellent compliance with the Code for nitrite. It is interesting to note that 37% of the samples in this category contained no nitrite, whilst the rest of the samples contained nitrite but passed the MPC of 500 mg/kg. It is possible that some of the samples in this category were of the semi-dry heat-treated class but, as was stated previously, it is difficult to determine whether or not the samples have been heat-treated and this could be the cause of the relatively high proportion of samples not having nitrite detected.
All of the samples had excellent compliance for preservatives with all the samples complying with the Code. Sorbic acid was detected in 17% of the samples whilst benzoic acid was detected in none of the samples.
There was a small number of vegetarian products analysed and these contained neither nitrite nor preservative.
The likelihood of microbiological problems associated with this type of product appears to be low. There will be a need to resurvey in the future as manufacturers move in and out of the market. As low levels of E. coli were detected, a subsequent survey should look into the toxigenic status of any future E. coli isolates.
The overall compliance rate for manufactured meat products for nitrite appears to be high although the cooked manufactured meat products show a significant failure rate of 35%. No failures were recorded for the uncooked manufactured meats.
The compliance rate for preservatives in the manufactured meat products is excellent with none of the samples failing the requirements of the Code. The highest level of sorbic acid detected was approximately 1/25th of the MPC.
Future testing of manufactured meats should concentrate on the cooked and semi-dry heat-treated products to determine more clearly their compliance with the Code.
Future testing not to include determination of the preservatives benzoic and sorbic acid, but to include sulfur dioxide.