E CONTROL (margarine)

Summary Signiﬁcant hazards a Although there are no reported cases of food-borne illness associated with

consumption of margarine, signiﬁcant hazards to which adequate control measures need to be established are:

r Salmonella spp.

E. coli O157:H7 r L. monocytogenes.

Control measures

Initial level (H 0 ) r Use appropriate ingredients (source from approved supplier on basis of

agreed speciﬁcations). r Pasteurise ingredients in-house before use, when contamination with

pathogens of concern cannot be excluded. r Use potable water from a reliable source.

Reduction (ΣR)

r Use preservatives where appropriate. r Pasteurise water or pre-emulsion phase.

Increase (ΣI) r Use the appropriate product structure: i.e. ﬁne water-in-oil dispersion to

prevent or limit growth of microorganisms. r Avoid (re-)contamination (keep to GMP; physically separate ingredients

and processed products). r Use suitable, hygienic equipment and process hygienically (incl. proper

cleaning). r Store ﬁnal product dry; prevent condensation.

Testing

r Ingredient speciﬁcation and water quality should be veriﬁed. r End product testing is not advised when a stable product formulation/

structure is used and process control is adequate.

Spoilage

r Generally, spoilage problems are controlled by using a stable formulation and an appropriate product composition, i.e. correct pH, clean

ingredients and appropriate (ﬁne) water dispersion. It is advisable to keep product refrigerated during open shelf-life.

a In particular circumstances, other hazards may need to be considered. Control measures.

A process design based on a cold process is generally adequate to achieve microbiologically safe and stable products, provided that suitable raw materials are employed. Correct product composition and emulsion characteristics should assure safety of margarine products at the point of consumption (Charteris, 1995; van Zijl and Klapwijk, 2000). For microbiologically sensitive products, it is most important to prevent contamination originating from raw materials or the processing environment. This means that for each product one should consider whether ingredients used present

a potential for contamination. Use of decontaminated ingredients or pasteurization of contaminated ingredients in a starch or water phase will control such a hazard. In the case of very sensitive products, refrigerated distribution should be considered.

Raw materials. The microbiological quality of ingredients should be ensured by purchasing on the

503 of a raw material, as obtained from the supplier, can be a CCP in an HACCP plan when that raw material

OIL- AND FAT-BASED FOODS

is at risk of being contaminated with relevant pathogens and does not undergo a decontamination step before it is used in the production of a margarine.

Refined oil is virtually sterile due to the high temperatures applied during refining. Microbiological problems can be prevented by keeping the oil storage and transport system free from water. Oil should therefore be monitored for the absence of water. As water is heavier than oil, water condensate will accumulate at the bottom of tanks or in low insufficiently flushed parts of process equipment, creating unexpected and undesirable problems with molds. This happens only when the oil system is improperly designed.

Some ingredients may be added to the oil (e.g. flavors, colors, vitamins, and emulsifiers). Spices and herbs added for flavoring purposes may be contaminated with pathogens of concern (i.e. Salmonella spp., L. monocytogenes, E. coli O157:H7) and may also contain high numbers of spoilage microorganisms (Chapter 7). Spices and herbs should be decontaminated either by the supplier or, directly prior to processing, by the margarine manufacturer. Special attention should be given to lecithin from, for instance, soybean oil, since this can be contaminated with lipolytic microorganisms as well as Salmonella spp.

Dairy ingredients should always be made from pasteurized milk. Therefore, tight microbiological criteria apply for dairy ingredients. Example criteria (taken from a typical manufacturer—not legal requirements) for powders: e.g. aerobic plate count <10000 cfu/g, Enterobacteriaceae (as indicator for hygiene) <100 cfu/g, yeasts and molds <100 cfu/g, Bacillus cereus <1000-cfu/g, and absence of infectious pathogens. Examples of criteria for liquids dairy ingredients, e.g. aerobic plate count < 1000 cfu/g, Enterobacteriaceae (as indicator for hygiene) <10 cfu/g, thermophilic bacteria <100 cfu/g, yeasts and molds <100 cfu/g, B. cereus <100 cfu/g, and absence of infectious pathogens. Buttermilk powder may contain high counts of thermophilic spore-formers, which is important when either stock solution, the aqueous phase, or the pre-mix is stored at a temperature allowing growth. Because the presence of bacterial spores in the ﬁnished product cannot be prevented, the composition and the physical structure of the ﬁnished product should limit their outgrowth.

Other ingredients such as salt, preservatives, and acidulants are generally free of microbial contamination. Water must always be of potable quality and drawn from a reliable source. The microbial content should be regularly monitored.

Composition. The stability of a margarine is influenced by the product composition (i.e. correct pH, the appropriate level of ingredients and fine water dispersion). Therefore, the process must be controlled to obtain these desired properties. The pH value of the product after equilibration with the fat phase may be critical, particularly when a preservative is being used. Critical product properties should always be incorporated into monitoring and verification programs and the results subjected to trend analysis.

Processing. Manufacture requires a well-cleaned and disinfected line. It is important to pay proper attention to cleaning and disinfection procedures; equipment should preferably be cleanable in place.

The effectiveness of cleaning and disinfection should be veriﬁed by analyzing start-up samples. Contam- ination from the environment and human sources should be avoided throughout the production process. The equipment can be a source of contamination when it is improperly designed (e.g. dead spaces occur), improperly maintained, allows build-up of product residues or remains wet during idle periods. Also, reciprocating or rotary shafts (in pumps) may carry external contaminants to the product stream. Therefore, the state of the equipment is an important factor in determining the time of a production run until the next cleaning cycle (Lelieveld and Mostert, 1992).

The preparation of the aqueous phase and the stock solutions are microbiologically vulnerable steps.

MICROORGANISMS IN FOODS 6

materials should be used when they enter the process at a stage when there is no heat-decontamination step further downstream. Permissible time and temperatures should be speciﬁed and controlled at this stage. The microbiological status at this point should be veriﬁed by taking samples at regular intervals. When temperatures over 40 ◦

C are used for extended periods, samples should also be checked for growth of thermophilic microorganisms.

A stable end product may be obtained when a suitable formulation is used and the emulsion characteristics are properly controlled. In a stable product, multiplication of contaminating bacteria or yeasts is not possible and, more likely, death may occur. In this case, more lenient microbiological speciﬁcations and sampling schemes may apply. However, when emulsion characteristics are not well controlled and a too coarse emulsion allows microbial growth, then the speciﬁcations for fresh product and the sampling scheme should be more stringent. The stability of a product can be checked by comparing microbial growth in stored (e.g. 2 weeks at 20 ◦

C) samples with fresh samples.

Packaging. Packaging equipment usually is not easily cleaned. Manual cleaning needs to be super- vised and closely monitored. Since end product may be exposed to the environment at packaging, the hygiene needs to be controlled carefully: air quality should be adequate (when necessary, air filtration should be used to limit contamination of the product with mold spores; in exceptional cases a laminar air flow cabinet is needed) and packaging materials should be of good microbiological quality (complying to specifications regarding mold counts; stored, transported and handled appropriately for a cold-filled food product). Secondary packaging materials, especially recycled cardboard (Scholte, 1995), may be a specific source of mold spores and should best not be handled in the packaging area. Packaging, storage, and distribution conditions should not permit free moisture to develop either on the product surface or on the packaging material.

Occasionally, product is made that is not packaged immediately after production. This may be at the start-up of the process when the packaging machine is mechanically out of order, or when the product has not been packed correctly. The handling of product ﬂow at this point is critical with respect to microbiological product quality. If unpacked product is reworked through a closed return pipeline and hygiene is properly controlled, the product can re-enter the main line without a decontamination step. Packaged product must be returned to the reﬁnery to regain the oil. This is microbiologically sound because this will involve a heat step. Rework that is exposed to the environment is subject to environmental contaminants and should be hygienically handled.

V Reduced-fat spread

A Deﬁnitions Much of the above information about margarine (with over 80 fat) is equally applicable to many of the

spreads with a reduced fat content. The difference is relative rather than absolute, as long as the spreads are true water-in-oil emulsions. Generally, water-in-oil spreads vary in fat content between 20% and 80%; below 20% fat spreads are oil-in-water emulsions. Products with a fat content between 41% and 62% are commonly referred to as reduced-fat spreads, whereas products with a fat content between 10% and 41% are called low-fat or light spreads (EC, 1994). Spreads made exclusively from milk fat are commonly referred to as dairy spreads (EC, 1994; CAC, 2001b). Spreads made from vegetable and animal fats, with a milk fat content of 10–80% of the total fat content, are called “blends” (EC, 1994). Other spreads are called “fat spreads” (EC, 1994; CAC, 2003) or “non-dairy spreads”, if they contain ≤3% milk fat of the total fat content. The following is applicable for a typical reduced fat-spread (water-in-oil; about 40% fat content); other spreads are not discussed separately.

OIL- AND FAT-BASED FOODS

B Important properties There are several differences between an 80% fat and a 40% fat water-in-oil emulsion (Keogh et al.,

1988): r The moisture content of the reduced-fat product is higher and salt and other water-soluble preservatives

(e.g. organic acids) are diluted to such an extent that they lose their effect on microbiological stability. This dilution factor cannot be compensated for by adding more salt or acid because an unacceptable taste results.

r In order to structure the aqueous phase of the reduced-fat product, there is a tendency to add biopoly- mers (vegetable or animal protein, thickeners), which may increase the microbiological vulnerability

of the aqueous phase. r The water droplet size distribution of the reduced-fat spread often has a higher mean diameter and a

larger distribution width compared to margarine products because of physical effects. As a consequence, reduced-fat spreads are more vulnerable to microbiological problems than mar-

garines. This increased vulnerability may partly be counteracted by introduction of in-line pasteurization, use of a preservative or increased attention to process line hygiene and equipment design. Preservatives generally allowed are sorbic acid (EC, 1995) and benzoic acid or their salts; permissible concentrations in, for example, 0.1% in ≥ 60% fat spreads and 0.2% in <60% fat spreads. To ensure a sufﬁcient level of the undissociated acid, the pH should be sufﬁciently low (i.e. <5.3; best <5.0). A pH of <4.5 is generally not possible because of precipitation of dairy proteins. The salt level in the aqueous phase of a reduced-fat spread is generally lower than in margarine or butter, except for spreads containing 70–80% fat. The salt level of the product ranges in general from 0% to 1% and rarely contributes to the microbiological stability of the spread.

The structure of reduced-fat spreads in principle is similar to that of butter or margarine, although the aqueous phase may be structured by thickeners and larger water droplets may occur that make the water dispersion coarser (Keogh et al., 1988; Madsen, 1990; van Zijl and Klapwijk, 2000). Reasonable emulsion characteristics for a 40% fat spread containing protein are, for instance, 50% of the water volume in droplets with diameters <15 µm and less than 5% in droplets with diameters >90 µm

(D 3.3 =

15 µm, e σ = 3.0). Reduced-fat spreads lacking protein are easier to produce and often have

a ﬁner water dispersion, e.g. 50% of droplets have ø <10 µm and <5% of droplets have ø >45 µm (D 3.3 =

10 µm, e σ = 2.5). Fat-continuous spreads containing 20% fat often have a very coarse water dispersion, e.g. 50% of droplets have ø <50 µm and <5% of droplets have ø >300 µm (D 3.3 =

50 µm,

e σ = 30). Next to water dispersion, the stability of the emulsion is important for microbiological stability. Coalescence of droplets can release water at the product surface allowing, for instance, mold growth.

C Methods of processing and preservation The manufacturing process for reduced-fat spreads is comparable to that of margarine. Strict hygiene

is necessary where the aqueous phase forms a water continuum (pre-emulsion phase). Also the microbiological stability of the complete formulation will determine the hygienic requirements of the production process (Klapwijk, 1992). With vulnerable formulations, in-line pasteurization of the complete emulsion is applied. Pasteurization aims at a 5–6 log reduction of vegetative microorganisms, for instance by applying 70 ◦

C for 2 min. Growth of microorganisms before pasteurization should be prevented, because metabolic products (e.g. enzymes, off-ﬂavors, toxins) might remain and affect the stability, quality, or the safety of the spread. It is advisable to decontaminate potentially suspect raw material before addition to the aqueous phase or pre-emulsion. Interim and ﬁnished product should be tested regularly to verify that microbial growth (including that of thermophiles) does not occur during

MICROORGANISMS IN FOODS 6

processing. Equipment should be designed to prevent contamination during processing, especially after the last heat-decontamination step, and it should be possible to properly clean and disinfect the process line. If the downstream equipment is a closed system preventing contamination from outside, microbiological stability will be obtained (Lelieveld and Mostert, 1992). The pasteurize and the conﬁg- uration of accompanying pipe-work should safeguard against under-pasteurization and should prevent leakage from the cooling system to the product and, thus, recontamination after pasteurization. Proper hygiene during packing is also important, especially with regard to contamination by molds. The most vulnerable products may require special measures such as a laminar ﬂow cabinet with sterile air and decontamination of packing materials (comparable to aseptic packing of liquid products).

Post-processing temperature abuse may be another factor to account for, as it may cause condensation of moisture on the surface of the spread and destabilization of the physical product structure. Both fac- tors can compromise the preservative effects of the compartmentalized structure providing opportunity for incidental (cross-)contaminants to proliferate. This may be especially relevant for the large-size, multiple-use containers commonly used in food-service establishments, which also get more popular for household in parts of the world. Challenge tests can help evaluate whether product formulations are sufﬁciently robust under abuse conditions. Cirigliano and Keller (2001), surface inoculated different commercial margarine and reduced-fat spreads with L. monocytogenes and found no growth for 7 days during storage between 5 and 23 ◦

C. Holliday et al. (2003) challenged two reduced-fat spreads (pH 4.05 and 49% fat; pH 5.37 and 61% fat) and a light-margarine (pH 5.34 and 31% fat), all containing preservatives, after temperature abuse (keeping products for 1 h at 37 ◦

C, 85% relative humidity) and physical abuse and stored the products at 4.4 or 21 ◦

C for up to 21 days. These products were found to be sufﬁ- ciently robust, as products did not support growth of any of the pathogens at either temperature for the duration of storage. In a related study, Holliday and Beuchat (2003) showed that the inactivation rate of individual pathogens in commercial yellow-fat spreads products varies according to product formulation (i.e. pH, emulsion characteristics, salt, fat, and preservatives content) and storage temperature.

Closed shelf-life of reduced-fat spreads is generally limited to 3–6 months, often for non- microbiological reasons. The more sensitive product formulations may require refrigerated storage, especially during consumer use. During consumer use, the product may become contaminated with a variety of microorganisms originating from the air, bread crumbs, or from other foods. With very vulnerable products, e.g. non-preserved low-fat spreads containing a dairy ingredient or water-continuous spreads, the closed shelf-life duration may be quite limited (e.g. 2–3 weeks) due to microbiological reasons. For most spreads, the open shelf-life duration is, however, not limited.

D Microbial spoilage and pathogens Spoilage. Many reduced-fat spreads, in principle, may allow growth of yeasts, molds, spoilage bac-

teria (e.g. Enterobacteriaceae, pseudomonads, aerobic spore-formers), and even pathogenic bacteria (discussed below) when present or introduced during production/open shelf-life. Compared with margarine, the aqueous phase is often more vulnerable, whereas the ﬁnal emulsion exerts less protection. Most frequently, microbiological problems are caused by molds of the same types as those causing spoilage of butter and margarine. The more coarse and less stable emulsions of reduced-fat spreads may favor mold-spore germination, mycelial development, and sporulation. Preservatives such as benzoate and sorbate greatly reduce mold problems during distribution and consumer use, provided they applied at the appropriate concentration and pH.

Pathogens. Although there are no reports of food-borne illnesses caused by the consumption of reduced-fat spreads, the microbiological vulnerability of this type of product requires use of suitable raw materials, pasteurized when necessary to assure absence of vegetative infectious pathogens, and

OIL- AND FAT-BASED FOODS

E CONTROL (margarine)