Cronobacter Support
07-15-2009, 11:26 AM
5.3.4 Post-processing and packaging
The difficulty which has to be considered in the evaluation of potential treatments for inactivating microbial pathogens in powdered infant formula is the behaviour of vegetative cells in dry products, i.e. very frequently there is increased heat resistance. Based on currently available knowledge, sterilization of the final product in its dry form in a processing environment in cans or sachets seems only possible using irradiation. However, with the doses that are likely to be required to inactivate E. sakazakii in the dry state, the technology does not appear to be feasible due to organoleptic deterioration of the product.
Figure 3 (attached). Heat resistance of different strains of E. sakazakii and other Enterobacteriaceae (Buchanan, 2003).
Note: E. sakazakii (N&F pooled) = pool of 10 strains as reported in Nazarowec-White and Farber (1997a).
A number of other technologies, such as ultra-high pressure and magnetic fields, may be potential candidates. These new technologies are at an early stage of development and currently none are suitable for dried foods. It is recommended that research be done in this field, bearing in mind the needs for quantitative validation of the killing effect.
5.3.5 Hazard Analysis Critical Control Point (HACCP) in the manufacture of powdered infant formula
In the United States and Europe, for many years now, infant formula manufacturers have recognized that GHP and HACCP play a primary role in the control of microbiological, chemical and physical hazards as well as allergens. Although there is currently no worldwide regulatory requirement for infant formula manufacturers to have HACCP plans, most (if not all) incorporate HACCP principles into their control programmes as well as GHP. Quality of raw materials, air and liquid filters, sifter screens, magnets/metal detectors, pasteurization and storage temperatures are important control points and must be addressed specifically.
Table 3 (attached). Decimal reduction time (D-value)a and z-valueb for E. sakazakii in powdered infant formula.
The heat treatments (CCP) applied are theoretically sufficient to ensure the destruction of eight or more log units of Enterobacteriaceae, including Salmonella and E. sakazakii, as well as other vegetative microorganisms, such as L. monocytogenes or S. aureus. Spore-formers, such as B. cereus and C. botulinum, are inactivated in part – to what extent depends on the processing conditions. Other heating steps are typically applied in a wet-mix process, but they are not considered CCPs; they include:
1. thermization or pasteurization of, for example, raw materials (e.g. incoming raw milk or raw whey);
2. preheating of the liquid formula before spray-drying; and
3. actual spray-drying.
Although these steps may have some killing effect (in particular, steps 1 and 2), they are performed for technological reasons and are not considered CCPs.
5.3.6 Monitoring
5.3.6.1 Methods for detection
Different genera and species of Enterobacteriaceae have been isolated from reconstituted powdered infant formula after enrichment (Muytjens, Roelofs-Willemse, and Jasper, 1988; Iversen and Forsythe, 2004), including E. sakazakii, E. cloacae, C. koseri, C. freundii, Pantoea agglomerans and Escherichia vulneris (the latter two formerly known as E. agglomerans). Specific detection methods are required to isolate and distinguish between closely related members of the Enterobacteriaceae.
• Primary isolation: Both E. sakazakii and S. enterica are isolated using pre-enrichment, enrichment and selective-differential agar. For Salmonella, multiple 25 g volumes (n = 60) are tested (CAC, 1979; ICMSF, 1986), whereas for E. sakazakii a most probable number approach is used with multiple 100 g, 10 g and 1 g volumes (Figure 4) (Muytjens, Roelofs-Willemse, and Jasper, 1988; Nazarowec-White and Farber 1997b; USFDA, 2002). For both organisms, presumptive isolates are confirmed using biochemical or gene-based tests (Anon., 1996; Kandhai, Reij, and Gorris, 2004). For Salmonella, methods have been validated by international organizations, but this is not the case for E. sakazakii. A characteristic of most E. sakazakii strains is the production of a yellow non-diffusible pigment below 37°C. However, this is not a unique trait and it is commonly found in the closely-related genus Pantoea which has also been isolated from reconstituted powdered infant formula (Muytjens, Roelofs-Willemse, and Jasper, 1988; Iversen and Forsythe, 2004). In addition, there are white E. sakazakii strains (Block et al., 2002). A second common trait used in presumptive identification is the production of α-glucosidase (Muytjens, van der Rose-van de Repe, and van Druten, 1984; Iversen, Druggan, and Forsythe, 2004). Internationally-validated methods exist for the specified pathogens, B. cereus, C. perfringens and S. aureus, and the indicator organisms coliforms and Enterobacteriaceae (USFDA Bacteriological Analytical Manual; Health Canada Compendium of Methods, ISO, Geneva). No internationally validated methods exist for specific Enterobacteriaceae such as E. sakazakii, E. cloacae and C. koseri. Biochemical profiles are frequently used following primary isolation (Figure 4), but contradictions in identification may occur in different biochemical kits for the same strain (Iversen, Druggan, and Forsythe, 2004). Further research is required into the genetic diversity and distinguishing traits of E. sakazakii and related organisms.
• Typing: Salmonella isolates are subject to established typing methods, including serotyping, phage typing and antibiograms. Central alert centres exist (PulseNet and Salm-Net) to detect multinational Salmonella outbreaks due to a common food source (Swaminathan et al., 2001; Rowe et al., 2004). Methods used to fingerprint E. sakazakii isolates include plasmid typing, ribotyping, pulsed field gel electrophoresis (PFGE) and random amplified polymorphic DNA (RAPD) typing (Biering et al., 1989; Clark et al., 1990; Nazarowec-White and Farber, 1999). These methods enable the tracing of specific strains in powdered infant formula production and are very useful during epidemiological investigations, to observe if clinical and food isolates are indistinguishable (Smeets et al., 1998).
Figure 4 (attached). Quantitative E. sakazakii isolation procedure.
a USFDA (2002); b Muytjens, Roelofs-Willemse, and Jasper (1988); c Nazarowec-White and Farber (1997b) from Iversen and Forsythe (2003).
BPW, Buffered peptone water; EE Broth, Enterobacteriaceae enrichment broth;VRBG, Violet red bile glucose agar.
E. sakazakii isolates from powdered infant formula available in Canada and Canadian clinical isolates were characterized by phenotypic (biotype and antibiograms) and genotypic (ribotyping, RAPD and PFGE) methods (Nazarowec-White & Farber, 1999). There is currently at least one large food company that is using ribotyping of E. sakazakii to track the spread or trace the source of the organism in powdered milk plants. Molecular typing methods, such as ribotyping and PFGE, are very suitable tools for studying environmental contamination in plant processing environments, in trouble-shooting, as well as in tracing sources of contamination, and should, wherever feasible, be encouraged.
The difficulty which has to be considered in the evaluation of potential treatments for inactivating microbial pathogens in powdered infant formula is the behaviour of vegetative cells in dry products, i.e. very frequently there is increased heat resistance. Based on currently available knowledge, sterilization of the final product in its dry form in a processing environment in cans or sachets seems only possible using irradiation. However, with the doses that are likely to be required to inactivate E. sakazakii in the dry state, the technology does not appear to be feasible due to organoleptic deterioration of the product.
Figure 3 (attached). Heat resistance of different strains of E. sakazakii and other Enterobacteriaceae (Buchanan, 2003).
Note: E. sakazakii (N&F pooled) = pool of 10 strains as reported in Nazarowec-White and Farber (1997a).
A number of other technologies, such as ultra-high pressure and magnetic fields, may be potential candidates. These new technologies are at an early stage of development and currently none are suitable for dried foods. It is recommended that research be done in this field, bearing in mind the needs for quantitative validation of the killing effect.
5.3.5 Hazard Analysis Critical Control Point (HACCP) in the manufacture of powdered infant formula
In the United States and Europe, for many years now, infant formula manufacturers have recognized that GHP and HACCP play a primary role in the control of microbiological, chemical and physical hazards as well as allergens. Although there is currently no worldwide regulatory requirement for infant formula manufacturers to have HACCP plans, most (if not all) incorporate HACCP principles into their control programmes as well as GHP. Quality of raw materials, air and liquid filters, sifter screens, magnets/metal detectors, pasteurization and storage temperatures are important control points and must be addressed specifically.
Table 3 (attached). Decimal reduction time (D-value)a and z-valueb for E. sakazakii in powdered infant formula.
The heat treatments (CCP) applied are theoretically sufficient to ensure the destruction of eight or more log units of Enterobacteriaceae, including Salmonella and E. sakazakii, as well as other vegetative microorganisms, such as L. monocytogenes or S. aureus. Spore-formers, such as B. cereus and C. botulinum, are inactivated in part – to what extent depends on the processing conditions. Other heating steps are typically applied in a wet-mix process, but they are not considered CCPs; they include:
1. thermization or pasteurization of, for example, raw materials (e.g. incoming raw milk or raw whey);
2. preheating of the liquid formula before spray-drying; and
3. actual spray-drying.
Although these steps may have some killing effect (in particular, steps 1 and 2), they are performed for technological reasons and are not considered CCPs.
5.3.6 Monitoring
5.3.6.1 Methods for detection
Different genera and species of Enterobacteriaceae have been isolated from reconstituted powdered infant formula after enrichment (Muytjens, Roelofs-Willemse, and Jasper, 1988; Iversen and Forsythe, 2004), including E. sakazakii, E. cloacae, C. koseri, C. freundii, Pantoea agglomerans and Escherichia vulneris (the latter two formerly known as E. agglomerans). Specific detection methods are required to isolate and distinguish between closely related members of the Enterobacteriaceae.
• Primary isolation: Both E. sakazakii and S. enterica are isolated using pre-enrichment, enrichment and selective-differential agar. For Salmonella, multiple 25 g volumes (n = 60) are tested (CAC, 1979; ICMSF, 1986), whereas for E. sakazakii a most probable number approach is used with multiple 100 g, 10 g and 1 g volumes (Figure 4) (Muytjens, Roelofs-Willemse, and Jasper, 1988; Nazarowec-White and Farber 1997b; USFDA, 2002). For both organisms, presumptive isolates are confirmed using biochemical or gene-based tests (Anon., 1996; Kandhai, Reij, and Gorris, 2004). For Salmonella, methods have been validated by international organizations, but this is not the case for E. sakazakii. A characteristic of most E. sakazakii strains is the production of a yellow non-diffusible pigment below 37°C. However, this is not a unique trait and it is commonly found in the closely-related genus Pantoea which has also been isolated from reconstituted powdered infant formula (Muytjens, Roelofs-Willemse, and Jasper, 1988; Iversen and Forsythe, 2004). In addition, there are white E. sakazakii strains (Block et al., 2002). A second common trait used in presumptive identification is the production of α-glucosidase (Muytjens, van der Rose-van de Repe, and van Druten, 1984; Iversen, Druggan, and Forsythe, 2004). Internationally-validated methods exist for the specified pathogens, B. cereus, C. perfringens and S. aureus, and the indicator organisms coliforms and Enterobacteriaceae (USFDA Bacteriological Analytical Manual; Health Canada Compendium of Methods, ISO, Geneva). No internationally validated methods exist for specific Enterobacteriaceae such as E. sakazakii, E. cloacae and C. koseri. Biochemical profiles are frequently used following primary isolation (Figure 4), but contradictions in identification may occur in different biochemical kits for the same strain (Iversen, Druggan, and Forsythe, 2004). Further research is required into the genetic diversity and distinguishing traits of E. sakazakii and related organisms.
• Typing: Salmonella isolates are subject to established typing methods, including serotyping, phage typing and antibiograms. Central alert centres exist (PulseNet and Salm-Net) to detect multinational Salmonella outbreaks due to a common food source (Swaminathan et al., 2001; Rowe et al., 2004). Methods used to fingerprint E. sakazakii isolates include plasmid typing, ribotyping, pulsed field gel electrophoresis (PFGE) and random amplified polymorphic DNA (RAPD) typing (Biering et al., 1989; Clark et al., 1990; Nazarowec-White and Farber, 1999). These methods enable the tracing of specific strains in powdered infant formula production and are very useful during epidemiological investigations, to observe if clinical and food isolates are indistinguishable (Smeets et al., 1998).
Figure 4 (attached). Quantitative E. sakazakii isolation procedure.
a USFDA (2002); b Muytjens, Roelofs-Willemse, and Jasper (1988); c Nazarowec-White and Farber (1997b) from Iversen and Forsythe (2003).
BPW, Buffered peptone water; EE Broth, Enterobacteriaceae enrichment broth;VRBG, Violet red bile glucose agar.
E. sakazakii isolates from powdered infant formula available in Canada and Canadian clinical isolates were characterized by phenotypic (biotype and antibiograms) and genotypic (ribotyping, RAPD and PFGE) methods (Nazarowec-White & Farber, 1999). There is currently at least one large food company that is using ribotyping of E. sakazakii to track the spread or trace the source of the organism in powdered milk plants. Molecular typing methods, such as ribotyping and PFGE, are very suitable tools for studying environmental contamination in plant processing environments, in trouble-shooting, as well as in tracing sources of contamination, and should, wherever feasible, be encouraged.