D CONTROL (animal by-products)

D CONTROL (animal by-products)

Summary

Significant hazards

r Salmonella and, in certain regions, BSE.

Control measures

Initial level of contamination (H 0 )

r Do not use animals with anthrax or BSE, processed animal proteins or high-risk material (for BSE).

Reduction of contamination (ΣR)

r Heat the raw material at 130 ◦

C for 20 min at 3 bars to achieve

a 3 decimal reduction of the BSE agent. This heat treatment will also reduce the number of B. anthracis and salmonellae to safe levels.

Increase of contamination level (ΣI) r Assure adequate separation between raw and processed material, keep line-environment dry and free of salmonellae.

Testing

r Test environmental samples for the presence of salmonellae or determine the level of Enterobacteriaceae to detect niches

where multiplication may have occurred.

Spoilage

r Spoilage is not a problem as long as the meal remains dry.

While producing meals derived from warm-blooded animals, the primary concern is to avoid passing heat-resistant pathogens such as B. anthracis and BSE from feed to cattle to man and to preventing recontamination with salmonellae. It is nearly impossible to control the initial levels of the first two hazards, because their multiplication in the host is the cause of their slaughtering or death and thus for rendering the animals. However, infected carcasses or parts thereof (see further on) can be sent to incineration plants instead of rendering plants in order to reduce the initial level of these hazards. In the production of meat and bone meal, it is very important to inactivate these pathogens in animal tissues through appropriate processing procedures.

C for 20 min has been established in some countries (Genigeorgis and Riemann, 1979, quoted by Swingler, 1982). As regards the BSE agent, a treatment of 133 ◦

To destroy B. anthracis spores, a heat treatment of 140 ◦

C, for 20 min at 3 bars (of particles <50-mm in size), or equivalent conditions are necessary to reduce the infectivity by 1000-folds (SSC, 1999). However, in BSE affected countries, where the risk of heavily contaminated animal by-products with BSE agent is significant, treatment of the raw material is not considered as a reliable method for the eradication of the BSE epidemic and ensuring feed safety. Therefore, the approach that has been taken is based on the minimization of the risk of BSE agent entering the feed chain. For this purpose, the United Kingdom and subsequently the EU countries have introduced a number of legislative measures aiming at preventing exposure of cattle to potentially contaminated feedstuff. First in 1988, United Kingdom prohibited the feeding of ruminant-derived protein to any ruminant animals. Subsequently, the EU Commission took, in 1994, the decision of banning the use of mammalian derived proteins to any ruminant animals.

However, despite these measures, and the fact that the incidence of BSE began to decline after 1993, the ban did not prove to be fully effective in containing the BSE epidemic. A number of cows born after the ban (BAB) were still affected. Subsequent investigation showed that at a number of points along the feed chain (feed mill, delivery lorries, and farms), cross-contamination occurred between the ruminant-derived protein for use in pig and poultry rations and the cattle feedstuffs. Consequently, in

MICROORGANISMS IN FOODS 6

March 1996, the United Kingdom banned the use of mammalian meat and bone meal (MBM) from the feed of all farm animals. The EU also introduced similar measures and in December 2000, the Council of the European Union prohibited, on a temporary basis, the feeding of processed animal proteins to all farmed animals. The EU Regulation No. 1234/2003 banned most commercially used processed animal proteins for feeding all animals which are kept, fattened or bred for the food production. Under certain conditions, exceptions are made for feeding fish meal, gelatine and hydrolyzed proteins to non- ruminants, and milk and milk products to all farm animals. Considering that cats were also shown to be susceptible to BSE agent, this provision was also made for pet food. Preventive measures have also been introduced in some other countries. For instance, in August 1997, the US Food and Drug Administration prohibited the use of most mammalian protein in the manufacture of animal feeds given to ruminants.

In addition to the feed ban, other public health measures have been introduced in BSE affected countries. Depending on the country, these measures include (EC, 2001a,b) the following:

r Statutory slaughter of all suspected cases of BSE, and depending on the country, all other ruminants of the holding or the cohort of the animal (same class of age and exposed to the same risk) in which

the disease was confirmed. r Ban of use of specified risk material (SRM), which refers to tissues of cattle, sheep, and goats that are

known to, or might, harbor detectable BSE infectivity in infected animals. This may vary depending on the country. The European Commission defines SRM as: (i) the skull including the brain and eyes, the tonsils, the spinal cord of bovine animals aged over 12 months, the intestines from the duodenum to the rectum of bovine animals of all ages; (ii) the skull including the brains and eyes, the spinal cord of ovine and caprine animals aged over 12 months or the ones that have a permanent incisor erupted through the gum, and the spleen of ovine and caprine animals of all ages (additional provision has been made for United Kingdom and Portugal).

r Interdiction of use of bones of the head, vertebral column of bovine, ovine and caprine animals in the manufacture of mechanically recovered meat.

r Surveillance of BSE and screening all bovines aged over 30 months for BSE and 24 months for cases of special emergency slaughter. Import restriction for countries where BSE is confirmed or likely. A number of measures are also

recommended for ensuring safety of gelatine, tallow, cosmetic, and pharmaceuticals. The fundamental principle in ensuring safety of these products is safe sourcing of raw material (WHO, 2001).

Dry rendering or wet rendering, where the products are subjected to conditions of high temperature and pressure appropriate to inactivate spores, will result in the destruction of salmonellae. Equipment used may be quite sophisticated and include, for example, an automatic feed mechanism coupled with an exit gate control that allows only cooked material to exit the cooker or end point controls to signal the point in the cooking cycle at which the products have been sufficiently cooked and dried (Wilder, 1971). With all commonly used rendering processes, a sufficient reduction in numbers of salmonella can, and should, be obtained. In case of doubt, process validation and trials should be carried out. Moreover, additional treatments may be given to reduce the numbers of salmonellae that may have recontaminated the product during further drying and processing. Heating and pelleting can reduce the level of salmonellae 100–1000-fold (Stott et al., 1975); expansion and extrusion are even more efficient. Ionizing irradiation is effective for destroying salmonellae in these products (Mossel et al., 1967). An alternative technique is to add chemical additives to the feed (Hinton and Linton, 1988). Such processes, which require specific control, are discussed in Section V.

Control procedures for preventing recontamination involve complete separation of raw and pro- cessed material, good hygiene, and sanitation procedures. Complete separation of raw material and finished product is critical to avoid reintroducing salmonellae into the heated or extruded material.

263 The areas for raw and processed materials should be physically separated by a leak-proof wall. In

FEEDS AND PET FOODS

addition, the two areas should have completely separate equipment and personnel for processing and maintenance.

Good hygiene and sanitation procedures are important. The processed material area should be kept scrupulously clean. Special care must be taken to prevent spreading dust from raw materials area to the finished products. Steam and water should be kept away from the processed material. Condensation of water should be avoided, especially in places where a fall in temperature is likely to occur during processing or transportation. If this is a major problem, control may require increasing air movement or insulating certain critical areas. Dry cleaning is preferred to wet cleaning in order to prevent possibility for growth of salmonellae in the environment.

Conveying systems should be as short as possible. Fresh air for cooling work rooms should not be from within the plant but from outside and as far as possible from the raw material area. Sweepings should not be reprocessed. Persons who enter the “clean” finished product area should put on clean clothing, wash hands, and clean the soles of their shoes (or change their shoes). Birds, flies, rodents, and other vermin should be eliminated from this area.

Finished product parameters for animal by-products depend upon the expected storage time. For storage of 2–3 years, an a w of 0.65 and moisture content of 8.5% or less is necessary. For storage of up to 5 months, an a w of 0.7 and moisture content of 9% is preferred. If storage will not exceed 5 weeks, an

a w of 0.75 and moisture content of 10.5% is acceptable (Thalmann and Wolf, quoted by Boloh, 1992). Increasing numbers of the hazards of concern due to multiplication is prevented by these levels of water activity.

Verification of the plant’s performance is necessary. Testing for the presence of salmonellae in en- vironmental samples should be done at frequent intervals (MAFF, 1989). Positive findings should be followed by a thorough investigation to eliminate the source of contamination. Samples of end prod- ucts may be directly examined for salmonellae. Since salmonellae are not uniformly dispersed in the material, occur in low numbers, and may be injured as a consequence of heat stress or osmotic shock, detection depends largely on the method of sampling, size of samples, and use of pre-enrichment procedures. Instead of testing for salmonellae, samples may be cultured for indicators. In The Nether- lands, regulations required analysis for Cl. perfringens and a review of the thermal processing to verify effectiveness of the cook. In certain countries, a test for Enterobacteriaceae has been advocated to locate potential contamination points along the processing line (Quevedo, 1965; Van Schothorst and Oosterom, 1984). It may also be applied to the final meal or feed to assess cross-contamination and growth (Cox et al., 1988). In one survey, the correlation coefficient between Enterobacteriaceae and salmonellae was 0.81 with confidence limits (95%) of 0.35–0.95. It was concluded that Enter- obacteriaceae are not good indicators for the presence of salmonellae, but they can be used to assess the hygienic quality of animal by-products (Michanie et al., 1985).

IV Fish meal

Between 20% and 30% of the total world catch of fish is used to manufacture animal feeds. The greater tonnage comes from processing whole fish that are not suitable for human consumption because they are too bony, too oily, or otherwise unsatisfactory; these fish are sometimes called “industrial fish”. Examples of fish used for fish meal include capelin, menhaden (Brevoortia spp.), sand eel, sprat, Norway pout, blue whiting, horse mackerel, Atlantic herring (Clupea spp.), anchovy (Engraulis spp.), pilchard, and related species. In the United States, for example, the entire menhaden catch goes to rendering.

A secondary source is the waste (offal) from fish and shellfish operations. South America, especially Peru and Chile, is a big producer with a yearly catch between 5 and 15 million tonnes. Amounts have

MICROORGANISMS IN FOODS 6

fluctuated partly due to the El Nino. Several European countries (Denmark, Norway, Iceland amongst others) process ∼6 million tonnes per year and the United States process 1 million tonnes.

Fish meal is basically prepared through three processes: boiling, separation, and drying. Industrial fish measuring 100 kg produces ∼20 kg of fish meal and 2–10 kg of fish oil. Whole or chopped fish are boiled in its own juice using an indirect supply of steam. The cooked material then passes into a screw press, which separates the liquid fraction (the press water) from the solid fraction—the press cake. The former contains about 50% of the water and most of the oil. The liquid passes a decanter in which the solids are separated and returned to the press cake and subsequently the oil is removed by centrifugation. The remaining liquid (the “stick-water”) is concentrated through evaporation, e.g. by falling film evaporators, and the product, “the solubles” added to the press cake. The press cake is then dried to a water content of 5–10%. A drying temperature of 90–100 ◦

C is used in the conventional process but some plants also produce LT meal, which had been dried at low temperature of ∼70 ◦

C. The material cools during further processing. The meal is sometimes cured before grinding and bagging by stacking it in a shed to allow oxidation to proceed. In most cases, antioxidants such as butylated hydroxytoluene (BHT) or ethoxyquin are mixed into the meal as it leaves the dryer. Stabilized meal passes directly from the dryer through a hammer mill, which reduces the particle size, and then into bags or bulk storage. In some parts of the world (e.g. Angola), the cooked, pressed fish are simply allowed to dry in the sun.

An increasing amount of ensiled fish is being produced as animal feed and the extent of current interest in the product suggests that production will increase even more. Ensiling involves liquefying the fish under acid conditions so that the final pH is below 4.5, producing a bacteriologically stable product. In one system, the chopped or comminuted fish is mixed directly with mineral (e.g. sulfuric) or organic (e.g. formic) acid and allowed to liquefy at temperatures above 20 ◦

C. Another process involves mixing a fermentable carbohydrate such as molasses or cereal meal with the minced or chopped fish, inoculating with lactic acid bacteria (e.g. Lb. plantarum or Streptococcus lactis) and allowing the fermentation to proceed, optimally at temperatures near 30 ◦

C. In both procedures, oil is removed from the final product by skimming or centrifuging. Fish solubles or fish concentrates are either a by-product of fish meal or a primary product of enzymatic digestion of entire fish. Fish meals are used widely in animal rations for their high protein content (60–70%). The fat level varies but is usually about 10%. Fish meal contains all the necessary nutrients for microbial growth except moisture, which is generally between 7% and 10%. On a global scale, some 7 million tones of fish meal and 1.5 million tones of fish oil are produced. During the last decade, aquaculture production has increased significantly (see Chapter 3) and ∼50% of fish meal and 90% of the fish oil is used for fish feed. Fish meal is also used for poultry and pork feed. A significant part of the fish oil is used for human consumption (IFFO, 2003).

A Effects of processing on microorganisms Fish may harbor different kinds of microorganisms, mostly reflecting the microbiology of the aquatic

environment (see Chapter 3). The heat treatment reduces the number of microorganisms to a low level (the actual number depending on the initial flora and the time–temperature combination used). However, Enterobacteriaceae and particularly Salmonella may be present in varying degrees due to recontamination after the heating. A study of fish meal from five factories found a mean aerobic plate

count of 10 4 , sulfite-reducing clostridia at approximately 3×10 3 , Enterobacteriaceae and enterococci ranging from 10 2 to 10 4 , and molds from 10 2 to 10 5 /g (Milanovic and Beganovic. 1974). The extent of recontamination with Enterobacteriaceae, including Salmonella, may differ widely among production sites and countries of origin (Van Schothorst et al., 1966; Reusse et al., 1976).

FEEDS AND PET FOODS

B Spoilage Fish meal is a microbiologically stable product because its a w (0.33–0.65) is below the value that will

support growth. Thus, in most cases, microbial spoilage is not important. If the product gets wet (e.g. during transport or storage), deterioration will occur due to rapid multiplication of fungi and/or bacteria.

There is no evidence of significant microbial problems with oils because they are unsuitable as growth media and undergo extensive physical and chemical refining.

C Pathogens Fish meal has been recognized as a source of salmonellae in animal feeds since the early 1950s, when

several serotypes such as S. Agona were introduced into many countries due to import of Peruvian fish meal. Salmonellae in feed are the principal problem not because they cause disease in the animals, but because they may ultimately cause food-borne illness in people who either handle or consume the products derived from the animals (Wiseman and Cole, 1990). An investigation showed that Enter- obacteriaceae, including salmonellae, could be isolated from the product at all stages of processing (Quevedo, 1965). The poor sanitation of many fish meal-rendering plants contributes to the spread of contamination. Table 4.2 lists the percentages of fish meal samples found positive in several investiga- tions. Erysipelothrix insidiosa has been recovered from Irish fish meal (Buxton and Fraser, 1971). If fish meal were to get wet, it would probably become moldy with the consequent potential for mycotoxin productions (Mossel, 1972; Gedek, 1973).