D CONTROL (breakfast cereals, snack foods)

Summary

Signiﬁcant hazards

r When good hygienic practices are in place, there are no major hazards.

Control measures

Initial level (H 0 )

r Supplier qualiﬁcation and speciﬁcation programs.

Increase (ΣI) r The naturally low a w of breakfast cereals prevents microbial growth. Reduction (ΣR)

r Heat treatments required for product functionality effectively destroy

pathogens in processed breakfast cereals.

Testing

r Routine manufacturing environmental sampling for salmonellae is useful to

identify potential harborage sites.

Spoilage

r There are no spoilage concerns for cereal products due to low water activity.

CEREALS AND CEREAL PRODUCTS

IX Pastries and ﬁlled products

A Effects of processing on microorganisms

A wide variety of filled and unfilled sweet products is available around the world, including filled and unfilled cakes, muffins, doughnuts, and cream puffs. Savory filled dough products include Asian egg rolls, wontons, and dimsum; Indian mimosas; Latin American and Spanish empanadas, and tapas; and Western products such as pirogis, meat pies, pasties, pizza, and sausage rolls. All of these products have the potential to combine foods from other food groups with dough or batter, which can influence the a w and introduce new food safety concerns.

Three basic procedures are used for the manufacture of ﬁlled pastries.

1. Filling ingredients are combined, cooked, and dispensed on or into pre-baked pastry tubes, shells or cakes (e.g. chocolate eclairs, Napoleons or imitation cream pies).

2. A preformed, baked or unbaked, pastry shell or wrapper is ﬁlled with combined, uncooked ﬁlling, the entire pastry is then baked, cooled, and packaged (e.g. coconut custard pies or dim sum).

3. A pre-baked pastry shell is ﬁlled with ingredients, some of which have been combined and cooked (as in 1 or 2), but other ingredients are added without cooking and the completed pastry has no ﬁnal baking (e.g. Nesselrode pies).

Many ﬁllings are excellent microbial growth media. Others are minimal substrates or they may even

be inhibitory because of one or more limiting factors, such as low a w , pH or nutrient content. Particular attention must be given to the interface between filling and cereal product surfaces for products stored and distributed at room temperature. For example, moisture from a filling may increase the a w of the dough to a level that supports growth, and the dough may buffer pH of an acidic filling to neutral levels. These relationships must be studied carefully to stabilize the products. Preservation is accomplished by alteration of formulation, refrigeration, and/or preservatives.

C kills all microorganisms except microbial spores, assuming that the entire batch reaches this temperature. However, in Type 1 pastries above, there is considerable opportunity for recontamination of the bulk during cooling, conveying, and dispensing (Silliker, 1969). In Type

Cooking ﬁllings to 76–82 ◦

3 pastries, there is even greater likelihood of contamination, because some ingredients are not cooked at all. Such a practice can be hazardous (Silliker, 1969; Deibel and Swanson, 2000). Cooking or reheating failures sometimes occur if the product is not all brought to an adequately high temperature.

C for about 6 min) offers too little heat to kill bacteria except those in the top layer. Meringue is an excellent insulator because of air bubbles entrapped in the foam. The temperature attained at the meringue–ﬁlling interface is often <44 ◦

Browning of meringue over a heat sensitive ﬁlling (heating in an oven at ∼230 ◦

C during browning (Bryan, 1976). Meringue may also be folded into a pastry or dessert with no heat process. Freezing and frozen storage of pastries may cause some loss of bacterial viability, but rarely eliminates

a given population. Aerobic plate counts and coliform group levels on various custard pies dropped to one-half their original level after 76 days at −20 ◦

C, except for the very acid lemon-lime pies whose counts dropped to one-half their original level in only 12 days (Kramer and Farquhar, 1977).

B Spoilage As with bread, mold growth is the predominant spoilage problem for pastries. However, the pastry ﬁlling

or topping may be more susceptible to microbial growth than the cereal product. Many ﬁllings support the growth of spoilage bacteria, especially if they have a high a w , near to neutral pH, and contain high protein ingredients such as meat, egg or milk. Cooked ﬁllings spoil from spore formers that survive the

MICROORGANISMS IN FOODS 6

cooking, other bacteria introduced after the cooking step, or those that survive inadequate cooking. In a German survey of cream cakes, 50% had aerobic plate counts of 1–5 × 10 6 cfu/g, 16% were >10 6 cfu/g, 6.5% were >10 7 cfu/g, with the highest count >10 9 cfu/g (Hartgen, 1983). In Belgium, aerobic plate counts were higher, 12% of samples contained 10 1 –10 2 cfu/g of Staph. aureus, and 22% contained > 10 5 cfu/g of B. cereus (Yde, 1982). Imitation cream pies spoiled in 48 h at room temperature (22 ◦

C) with aerobic plate counts of 10 7 – > 10 8 , coliform group levels exceeding 10 6 , and Staph. aureus up to 10 6 cfu/g (Surkiewicz, 1966). Col-

iforms and E. coli have been found in real and imitation cream cakes and pastries from a variety of manu- facturers (Greenwood et al., 1984; Pinegar and Cooke, 1985; Schwab et al., 1985; Michard et al., 1986).

High-sugar icings or low-pH toppings (i.e. fruit) will not support growth of spoilage bacteria but will eventually permit fungi to grow (Silliker, 1969).

C Pathogens Cream- and custard-ﬁlled pastries can cause foodborne disease. In the 5-year period from 1993–1997,

35 of 2751 reported foodborne outbreaks were associated with baked products (CDC, 2000). Salmonellae contributed to 34% of these outbreaks, Staph. aureus 9%, 6% viruses and the remainder were of unknown etiology. The report did not specify the type of bakery product. However, a previous report for 1938– 1972 identiﬁed cream-ﬁlled pastries as the primary vehicle with 85.2% from Staph. aureus and 12.5% from Salmonella (Bryan, 1976).

Staph. aureus, B. cereus (Fenton et al., 1984), and salmonellae (Barnes and Edwards, 1992) have been involved in cream ﬁlled pastry outbreaks. Temperature abuse and/or inadequate cooking were root causes

of the outbreaks. Staphylococcal food poisoning can occur only after the bacteria have multiplied under favorable conditions to reach millions per gram. The minimal temperature for enterotoxin production is l0 ◦

C (ICMSF, 1996). It is not surprising, therefore, that foodborne disease outbreaks from cream-ﬁlled pastries are attributed primarily to inadequate refrigeration during manufacture or storage (McKinley and Clarke, 1964, Bryan, 1976).

Salmonellae have been reported in many bakery ingredients, such as flour, milk, eggs, butter, cream, cheese, nuts, coconut and dried fruit. It is therefore essential that cooked fillings be protected from direct or indirect contact with such raw ingredients. Children and the elderly or infirm are especially susceptible to infection from small inocula such as one might find in a pastry in which growth had not occurred.

Listeria monocytogenes is sometimes present in the raw materials used in pastry manufacture, including milk and milk products (see Chapter 16), unpasteurized egg and egg products (see Chapter 15), meat (Chapter 1), and poultry (Chapter 2). The surface water activity of unﬁlled pastries is below the minimum required for L. monocytogenes growth and temperatures required to develop the structure of baked products destroy it. However, ﬁllings must be evaluated individually to determine the potential for L. monocytogenes growth. For example, L. monocytogenes was reported to multiply between 4 ◦ and

C in whipping cream, although multiplication at 4 ◦

C was quite slow (Rosenow and Marth, 1986).

D CONTROL (breakfast cereals, snack foods)