D CONTROL (pasta and noodles)
D CONTROL (pasta and noodles)
Summary
Significant hazards
r Staph. aureus. r Salmonella. r Cl. botulinum (only in refrigerated, fresh pasta packed under modified
atmosphere).
Control measures
Initial level (H 0 ) r Use pasteurized egg ingredients to reduce the potential for salmonellae. r Minimize handling of dough with bare hands for Staph. aureus.
Increase (ΣI) r Frequent and thorough cleaning of machinery, especially mixer hubs and
extruder heads. r Dry or refrigerate promptly after manufacture. r Chill refrigerated pasta rapidly to <7 ◦ C.
r Appropriate combinations of a w and pH can prevent growth of Cl. botulinum in refrigerated, modified atmosphere packaged pasta.
Reduction (ΣR) r Pasteurization can reduce salmonellae and Staph. aureus levels. r Boiling pasta dough or dried pasta before consumption inactivates salmonel-
lae. r Reduction of Cl. botulinum spores or Staph. aureus toxin levels is not possible
in pasta production.
Testing
r Periodic in-process testing for Staph. aureus is useful to evaluate process
control. r Environmental sampling for salmonellae is useful to identify potential harbor-
age sites. r Testing pH and a w may be appropriate if control of the formulation is used to
ensure safety of refrigerated products.
VIII Breakfast cereals and snack foods
A Effects of processing on microorganisms Manufactured dried breakfast cereal products are usually eaten in Western countries as breakfast foods.
They are produced primarily from wheat, maize, oats, and rice. Water is added to the cereal grains, which are processed by flaking, puffing or extrusion. Microbial growth can occur during the moist phase; however, further processing involves heat treatments that reduce the microbial load. Vitamins, minerals, sweeteners, flavorings, and colorings are applied after heating. This provides an opportunity for post-heat treatment contamination before packaging. Breakfast cereals processed in this manner under good hygienic practices typically have aerobic bacterial counts of <1000/g (Deibel and Swanson, 2001).
Whole grain breakfast cereals represent another type of product that may not be exposed to the heat treatments previously described. In a study of the microbial flora of whole grain cereal product in Germany, aerobic bacterial counts were ∼10 6 cfu/g and fungal counts were up to 2.0 × 10 5 /g (Table
8.11) (Spicher, 1979). Although counts of both bacteria and molds were high, pathogen levels were low.
MICROORGANISMS IN FOODS 6
Table 8.11 Average bacterial counts per gram from 184 whole grain cereal products a
Product
Rye and Bacterial type
Whole dehusked
Single grain
Cereal mixtures wheat flakes Mesophiles
grain
products in husk
0.9 × 10 6 3.3 ×10 6 5.5 × 10 6 1.1 × 10 4 Coliforms
1 Faecal streptococci
– Escherichia coli
0 60 3 – Staphylococcus aureus
0 0 0 – a From Spicher (1979).
The mycoflora of cereal products can be very diverse. One study isolated more than 60 fungal species from cereal flakes (wheat, oats, barley, and rye). Eurotium and Aspergillus species were dominant (Weidenb¨orner and Kunz, 1995).
B Spoilage Microbial spoilage of breakfast cereals is rare because of their extremely low water activity. The water
activity must be maintained below the monolayer level to maintain the crunchy character required for processed breakfast cereals, therefore no moisture is available for microbial growth.
C Pathogens and toxins Outbreaks of foodborne disease related to cereals are uncommon. As with spoilage, the low water
activity of the product prevents microbial growth. However, a large multi-state salmonellosis outbreak occurred in the United States related to toasted oat cereal (CDC, 1998). Salmonellae were isolated from the manufacturing environment after the outbreak (Breuer, 1999). Mycotoxin issues discussed previously in the grain section are applicable to cereals if the source of grains is not controlled.