E CONTROL (butter)

E CONTROL (butter)

Summary

Significant hazards a r Salmonella spp.

E. coli O157:H7. r L. monocytogenes.

r Staph. aureus.

Control measures

Initial level (H 0 ) r Limit growth of microorganisms in cream/milk raw material by controlling time/temperature of storage before us.

r Assure that the milk or cream used to start butter manufacture with is

adequately pasteurized. r Use appropriate ingredients (source from approved supplier or pasteurize

ingredients in-house before use).

Reduction (ΣR)

r Use preservatives where appropriate. r Pasteurise before churning.

Increase (ΣI) r Minimize possible growth in milk/cream before pasteurization (keep

refrigerated). r Use appropriate product structure to prevent or limit growth of

microorganisms; assure proper distribution of moisture and salt throughout the product.

r Avoid (re-)contamination after pasteurization. r Use of hygienic equipment and process hygiene (incl. proper cleaning) is

critical. r Store final product dry; prevent condensation.

Testing

r Ingredient specification and water quality should be verified. r Intermediate and finished product should be tested regularly to verify

process performance. r Routine end product testing is not advised when a stable product

formulation/structure is used and process control is adequate.

Spoilage

r Yeast and molds are the most relevant spoilage microorganisms. The end product should be kept refrigerated during open shelf-life. Freezing may

allow very long shelf-life.

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

MICROORGANISMS IN FOODS 6

Control measures. To achieve microbiologically safe and stable products, a process design based on a cold process may be completely adequate, but dairy raw materials and ingredients should be of suitable quality; pasteurization of the cream is commonly applied. As butter is a rather vulnerable product, strict processing-line hygiene, microbiological quality of the processing environment, and air humidity—all need to be carefully controlled. Appropriateness of the product composition and emulsion characteristics of the final product should be ascertained, especially with types of butter containing less than 80% fat and considering post-processing temperature abuse. Refrigeration is necessary during open shelf-life.

Raw materials. Cream should be of suitable microbiological quality. Suggested microbiological criteria for cream are: aerobic plate count <1000 cfu/mL; yeast, mold, and coliform counts <1 cfu/mL (Murphy, 1990). Bacillus cereus, which may be relevant for sweet, unsalted, or low-salted products with coarse water droplets, might be considered for monitoring purposes in view of its increasing occurrence in milk and the ability of some strains to germinate and grow slowly at refrigeration temperature (te Giffel et al., 1996). To date no B. cereus related outbreaks have occurred. Growth of microorganisms in the milk or cream before use for butter should be kept to a minimum (CCP), by controlling time and

temperature of storage. Starter cultures used for souring of cream are responsible for lactic acid formation and a concomitant decrease in pH. Pure or mixed concentrated cultures of lactococci and leuconostocs from commercial suppliers will provide a great degree of control over the acidification process. The starter culture should not become a source of contamination. Therefore, the number of subcultures should be limited.

Ingredients such as salt, coloring agents (e.g. beta-carotene), and neutralizers (e.g. sodium carbonate) are generally free of microbial contamination because of the way they are manufactured; the chemicals should be of food-grade quality. When water is used in butter manufacture after pasteurization, e.g. for washing, the water should be of potable quality.

Use of a preservative in butter may be considered. A concentration of 0.033% undissociated sorbic acid on aqueous phase, for example, may be sufficient to control mold spoilage of a protein-containing 40%-fat spread (0.12% potassium sorbate on product, pH 4.9) during closed and open shelf-life (van Zijl and Klapwijk, 2000). To limit mold contamination, a laminar flow cabinet at the packaging stage may

be necessary. Product (mold) spoilage may be limited further by storage at refrigeration temperature (≤7 ◦ C).

Processing. Pasteurization of the cream before churning is commonly done. When high numbers of microorganisms are present before pasteurization, not all hazardous microorganisms or the products of their metabolism may be inactivated by the usual pasteurization conditions. Bacterial spores are not inactivated by pasteurization and can germinate and grow when milk or cream of neutral pH is not sufficiently cooled. Any failure in pasteurization could lead to the survival of pathogens. Pasteurization is a critical control point when there are no further decontamination treatments down-stream in the butter manufacture process. Subsequent process steps should be designed such that multiplication of those microorganisms surviving pasteurization is prevented and recontamination is minimized.

Moisture and salt distribution is important with respect to the microbiological stability of butter. The pH is an important product parameter of sour cream butter. The verification programme should incorporate measurements of these factors and include trend analysis. If butter is used for making whipped butter or spiced butter, care should be taken that pathogens are not introduced due to poor hygiene or contaminated ingredients. After whipping or cold mixing, the time before using the product should be strictly limited even under refrigeration.

Recontamination of butter with microorganisms usually results from inadequate post-pasteurization hygiene (van Zijl and Klapwijk, 2000). Care should be taken that the equipment is properly cleaned and disinfected before start-up of the process. Preventing recontamination is also a function of equipment

515 design, maintenance, cleaning and disinfection procedures, and proper supervision. Process line hygiene

OIL- AND FAT-BASED FOODS

is important for the microbiological verification program. Samples from the start-up of the process as well as from the end of the run should be analyzed.

Packaging. Product may be exposed to the environment during packaging and recontamination should be prevented. High humidity in the room and lack of proper ventilation may allow molds to grow on walls and ceilings, thus producing foci of contaminating organisms from which air currents may carry mold spores to the product. The packing material should be of a good microbiological quality. Of particular importance is the level of contamination with molds (i.e. their spores). Cardboard cartons used as shipping containers may be an important source of mold spores, especially when recycled cardboard is used. The cardboard packing material should therefore not be handled in the packing environment but in a separate room. When butter is moved from a cool area to an area of high humidity, e.g. at the time it is being printed and wrapped, moisture is apt to condense on the surface possibly triggering growth of mold spores. Careful handling is necessary to prevent damage to the wrappers. Repackaging butter (e.g. from large blocks to portion packs) may cause the spread in localized areas of microbial growth to the entire production lot. Hence, butter that is repackaged should be fresh or of extremely good microbiological quality. Frozen butter must be thawed in a dry and well-ventilated room to prevent moisture condensation on the butter. Butter should be kept free from moisture during distribution. Cool, dry storage without exposure to high humidities during transport is necessary to prevent mold spoilage problems.

VII Water-continuous spreads

Water-continuous products with fat contents as low as 3% have been introduced successfully on the market. These oil-in-water products are developed for spreading on bread as low-calorie alternatives. Water-continuous spreads lack the protective effect of the fat barrier, but this can partly be compensated for by adding more preservative. Nevertheless, the products are still likely to be more sensitive to microbial growth. Although they are used as if they were a fat-continuous yellow fat spread, it should

be realized that their preservation relies partly on a different principle. Water-continuous spreads may actually be so vulnerable to mold spoilage that special measures such as a laminar flow cabinet with sterile air and decontamination of packing materials may be necessary, comparable to aseptic packing. Water- continuous spreads will always require refrigerated storage. The shelf-life typical of these products may

be limited, for microbiological reasons, to 2–3 weeks. The physical structure is critical for product stability and this is based on the physical stability of the emulsions discussed in the previous sections of this chapter. Physical stability can be ensured by a proper product design, appropriate combinations of temperature–time for storage and distribution, and proper handling during open and closed shelf-life.

Other intrinsic factors contributing to stability, either alone or in combination, are salt-on-water, pH, limited availability of nutrients and presence of preservatives (e.g. sorbic acid; benzoic acid; bacteriocins or diacetyl resulting from lactic acid bacteria involved in milk fermentation). Although 0.033% undis- sociated sorbic acid on aqueous phase may be sufficient to control mold spoilage during refrigerated shelf-life in a protein-containing, aseptically packaged 40%-fat spread (0.12% potassium sorbate on product, pH 4.9), water-continuous spreads may require higher levels of undissociated sorbic acid (i.e. > 0.04%) to prevent mold spoilage under these conditions. Higher levels of undissociated sorbic acid can

be reached by increasing the sorbic acid level or by decreasing the pH. The pH level of water-continuous spreads, however, is not much lower than 4.9 because lower values cause precipitation of dairy proteins. Up to now, water-continuous spreads have not been associated with any serious microbiological problems, probably because considerable attention is paid to their production (including careful product

MICROORGANISMS IN FOODS 6

design, high quality starting materials, and proper process hygiene) and maybe also because they have not been marketed extensively. However, considering the trend for major product innovations in this field and the appearance of new, sensitive types of products on the market-place, it should

be emphasized that microbiological knowledge and examinations need to be kept up-to-date for such potentially problematic products as water-continuous spreads. Additionally, it is advisable to validate new product and processing concepts using appropriate challenge tests.

VIII Miscellaneous products

This group includes butter oil, ghee, vanaspati, cocoa butter substitutes, and cooking oils. All these products have an extremely low-water content (<0.5%) and, therefore, generally do not allow microbial growth. However, when stored under moist conditions, mold spoilage may occur on the product surface. Also survival of infectious pathogens, in principle, is possible although there is no epidemiological evidence to indicate that this occurs in practice.

Some specific properties are: r Butter oil is milk fat separated from cream or butter after heat destabilization; it is purely milk fat without non-fat milk solids.

r Ghee is prepared by cooking (up to 120 ◦

C) butter or concentrated cream under atmospheric pressure to evaporate the water; as a result, ghee differs from butter oil by taste and the presence of non-fat milk solids.

r Vanaspati is a blend of butter oil and vegetable fat; the butter oil from ghee or fermented cream is used to give the product the correct flavor.

r Cocoa butter substitute is a purely vegetable fat product used to replace expensive cocoa butter in some applications; cooking oils consist mostly, but not exclusively, of vegetable oil.