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Chemical and Physico-chemical Changes in Processed Cheese and Ready-made Fondue During Storage.

A Review

W. Scha¨r and J. O. Bosset*

W. Scha¨r: Tiger Cheese Ltd., CH-3550 Langnau - Emmental (Switzerland) J.O. Bosset: Federal Dairy Research Station, Liebefeld, CH-3003 Berne (Switzerland)

(Received April 17, 2000; accepted July 19, 2001)

Processed cheese is often expected to be a stable product with a very long shelf-life. However, even products without any bacteriological contamination retain their high quality only for a few months at room temperature. During storage, structure and flavour slowly change. The following possible causes for such changes are reviewed in the present paper: loss of water vapour, hydrolysis of polyphosphates, changes in ionic equilibria, crystal formation, oxidation, nonenzymic browning, enzymatic activity as well as interactions with packaging materials. The changes with age of processed cheese are influenced by four main factors: product composition, processing, packaging and storage conditions (time and temperature). No work about the changes with age of ready- made fondue appears to have been published.

r2002 Elsevier Science Ltd

Keywords: processed cheese; ready-made fondue; storage; ageing; shelf-life; quality

Introduction

So far, most research studies into the problems of the shelf-life and storage of processed cheese have dealt with problems caused by microbial contamination. Modern processing technologies and careful selection of ingre- dients make it possible to produce bacteriologically stable processed cheese. For this reason, processed cheese is often expected to be a product with a shelf- life of more than 1 y. However, even bacteriologically stable products in good packaging usually maintain their quality only for 6–12 mo at room temperature (Chambre and Daurelles, 1997). During storage, chemi- cal and physical aging processes impair flavour and structure. A typical off-flavour, often called ‘old’

flavour, gradually appears, thus limiting the sensory quality. Structure also continuously changes, typically towards a firmer, shorter texture. Several changes can occur simultaneously.

This subject is relevant for all processed cheese manufacturers who have great know-how on this topic but have not published it for obvious reasons. They have to check for these changes during product development.

The ‘best before’ date must be declared according to the ageing properties of their products. Processed cheese for export markets should retain its quality as long as possible, especially for hot countries where they are the most popular cheese types. The manufacturers collect empirical data but a better knowledge of the main causes of change and factors contributing to this change would form the basis for further improvements. However, only few scientific results have so far been published.

‘Swiss Cheese Fondue’ (‘Fertigfondue’) is a typical Swiss meal including cheese, white wine and brandy (Kirsch).

In 2000, approx. 7,400 tons of ‘Swiss Cheese Fondue’

and 13,100 tons of processed cheese were produced in Switzerland (Swiss Association of Processed Cheese Manufacturers, 2000). Both products are mainly based on Emmental and Gruye`re cheese.

No published data are available about the ageing and shelf-life of ‘Swiss Cheese Fondue’ and processed Swiss Emmental cheese with citrates. Therefore, the Federal Dairy Research Station (FAM) of Liebefeld/Bern and the Swiss association of processed cheese manufacturers are carrying out a collaborative study on the ageing of processed Emmental cheese and ready-made Fondue.

The two main aims of that study, published in two parts, are to review the current knowledge on this topic and to complete it on several aspects investigating a 1-y ageing

*To whom correspondence should be addressed. E-mail: jacques- olivier.bosset@fam.admin.ch

0023-6438/02/020015+06 $35.00/0 doi:10.1006/fstl.2001.0820

r2002 Elsevier Science Ltd All articles available online at http://www.idealibrary.com on

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of commercial processed Emmental cheese and ready- made Fondue. Actual information about chemical and physical changes in processed cheese is summarised in the present review article.

Manufacture of Processed Cheese

Processed cheese is produced by heating a mixture of cheese, water, emulsifying salts (mostly sodium citrates, sodium orthophosphates or sodium polyphosphates) and further optional ingredients such as butter or spices.

Mix constituents and processing conditions are selected to give the desired structure, appearance, colour, flavour and shelf-life at an acceptable cost. The mixture is heated in a batch cooker to 70–1201C under a partial vacuum with constant agitation, until a homogeneous mass is obtained, or in a continuous UHT-process at 1401C. Generally, the hot processed cheese is filled into the desired packages such as pouches or polymer-coated aluminium foils. Thereafter, these packages are sealed and the products are cooled down. Several textbooks and review articles on processed cheese manufacture are available (Meyer, 1970; Paquet, 1988; Berger et al., 1989; Zehren and Nusbaum, 1992; Caric and Kalab, 1997; Chambre and Daurelles, 1997). The influence of heating on the volatile compounds of Swiss processed cheese varieties was recently investigated (Mariacaet al., 1998).

During processing, the natural cheese, consisting mainly of insoluble calcium paracaseinate and fat globules, is finely dispersed, homogenised and converted into a gel in which fat is emulsified. By chelating the calcium from the protein structure, the emulsifying salts contribute to the dispersion of the proteins and enhance their emulsifying properties. The structure of the processed cheese depends on the type of cheese used, the fat ratio, the dry matter and the ability of the emulsifying salt to sequester the calcium (Paquet, 1988).

Manufacture of Ready-made Fondue

The manufacture of ready-made fondue is similar to the manufacture of processed cheese. White wine, starch and Kirsch brandy are additional ingredients. As the tartric acid from the wine acts as a chelating agent, the content of emulsifying salt is set to a maximum of 8 g/kg, whereas processed cheese contains up to 40 g/kg (Eidgeno¨ssisches Departement des Innern, 1998). Com- mercial ready-made fondue is traditionally filled into multilayer aluminium pouches with a content of 400 g.

Recent developments include ‘microwaveable’ fondue in cups.

Microbiological Aspects

The scope of this review is limited to publications dealing with bacteriologically stable products. Micro- biological hazards can be eliminated by UHTpro- cessing: even temperature-resistant spores such as

Clostridium butyricum, Clostridium tyrobutyricum, Clostridium sporogenescan be destroyed. Post-sterilisation infection is prevented by hot filling (85–951C) into the packing (Sturm, 1998).

Shelf-life of Processed Cheese

According to Bergeret al. (1989), processed cheese is not a preserved food, but a ‘semi-preserved food’ with a limited shelf-life. Premium grade processed cheese should be given a shelf-life guarantee not exceeding 3–4 mo, especially when the product is packaged in plastic foils. Products stored in metal cans or tubes may have longer shelf-lives. According to Chambre and Daurelles (1997), processed cheese products usually retain their good quality for up to 6–12 mo at room temperature. Sturm (1998) differentiates the shelf-life of the following products stored at room temperature:

8 wk for slices, 20 wk for small portions, more than 1 y for products packed in tubes or cans. Table 1 summarises the possible changes and their relevance.

Ready-made fondue in multilayer aluminium pouches is very well protected against loss of water vapour, gas permeation and light transmission. It is typically produced with sodium orthophosphate as an emulsify- ing salt. A longer shelf-life could theoretically be expected, but even in this case, changes in the mouth- feel are noticed: the structure continues to become more homogeneous and the corresponding mouth perception is described as becoming more creamy. An increasing

‘old’ off-flavour (taste and odour) limits its sensory acceptance. Changes in fondue strongly depend on storage temperature: at 51C, the changes are much slower than at 201C (Tiger Cheese Ltd., Langnau- Emmental: internal reports).

General aspects of the shelf-life of various foods are discussed in textbooks. The following main changes will be described: loss of water vapour, hydrolysis of polyphosphates, changes in ionic equlibria, formation of crystals, reactions induced by heat-stable enzymes, nonenzymic browning, reactions induced by light and oxygen as well as interactions with packaging materials.

Loss of Water Vapour

Usual packaging material for processed cheese provides a good, but not a completely tight barrier against water vapour. Depending on storage temperature, a consider- able weight loss may occur, leading to a firmer texture (Tiger Cheese Ltd., Langnau-Emmental: internal reports). Typically, processed cheese slices, stored for 1 mo at 201C, may present a weight loss of 2–5 g/kg (Ney, 1988).

Hydrolysis of Polyphosphates

Linear polyphosphates (with 4 phosphates) are ob- tained from very pure orthophosphates (monophosphates)

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by high-temperature condensation (Chambre and Daurelles, 1997). They are hydrolysed in an aqueous solution (Berger et al., 1989). This reaction begins during melting and continues during the storage of processed cheese (Ney, 1988). The hydrolysis quickly leads first to triphosphates and diphosphates (pyropho- sphates) then more slowly to orthophosphates which are excellent pH buffers (Mair-Waldburg, 1958; Ruf and Gla¨ser, 1971). A part of added polyphosphates is already hydrolysed during the melting process. The rest is completely hydrolysed after 7–10 wk of storage (Caric and Kalab, 1997). The hydrolysis of oligo- and polyphosphates creates new acid functions thus lowering the pH-value of the product and inhibits an eventual pH increase (Chambre and Daurelles, 1997). The buffering capacity of polyphosphates depends on the chain length:

the higher the chain length, the lower the buffering capacity. Commercial mixtures of emulsifying salts often contain short-chain oligophosphates with the required good balance of calcium binding and buffering properties. Long-chain polyphosphates are added to

improve calcium binding (Bergeret al., 1989; Caric and Kalab, 1997). The rheological properties of various processed cheese slices were measured during 1 mo of storage at 4, 13 and 201C (Ney, 1988). A measuring device was developed, which bends the slices until they break. The breaking angles generally decreased during storage and were not caused by pH or loss of water vapour. The results were described as a hardening effect and related to the hydrolysis of polyphosphates (Ney, 1988).

Klostermeyer (1990) reported measurements of the firmness, viscosity and elasticity of various processed cheeses. Products containing phosphates first showed, however, a decreasing resistance after production. After about 3 wk a minimum was reached, thereafter the measured resistance rose again. This effect was not observed with products containing citrates as emulsify- ing salt. The curves presenting minima or maxima often result from opposite processes, likely a slow destruction of the primary gel structure and the formation of a secondary structure. The author supposes that these Table 1 Chemical and physical changes in processed cheese during storage

Influence on

Practical Improvement

Effect Cause Flavour Texture significance possibilities

Loss of water vapour

Packaging not completely tight

Noa Becomes

firmer

Depends on the packaging properties

Tighter packaging Storage at lower temperatures Polyphosphates

hydrolysis during storage

Unstable polypho- sphates in aqueous so- lutions, hydrolysed to short-chain poly- and orthophosphate

Noa Yes Only in products con- taining polyphosphates

Storage at lower temperatures

Changes in ionic equilibrium

Interaction of emulsi- fying salts with ions and

proteins

Noa Becomes

firmer

Mainly in processed cheese spreads with polyphosphates

Optimised mixture of emulsifying salts Storage at lower temperature Crystal formation Solubility of the

ionic components such as calcium, amino acids and emulsifying salts

No Yes Depends on product

composition and process

Optimised mixture and quantity of emulsifying salts

Avoid ripe cheese including crystals Reactions induced

by heat-stable enzymes

Even after processing heat-stable

enzymes might remain active

Yes Yes Depends on ingredients

and heat treatment during processing

Careful selection of in- gredients

Higher heat treatment during processing Storage at lower temperatures Nonenzymic

browning

Reaction of reducing sugars with amino acids

Yes Not

significant

Products with a signifi- cant amount of lactose (1–6%) become yellow/

brown

Lower lactose content Less severe heat treat- ment Storage at lower temperatures

Reactions induced by light and oxygen

Traces of oxygen in the package.

Permeation of oxygen through the package.

Yes Oxidation flavour

Not significant

Depends on composition (oxidising, antioxidative components), light and packaging properties

Tighter packaging with lower oxygen permeation

Packaging with a good light barrier

Storage at lower temperatures Interactions with

packaging materials

Migration of packa- ging components, cor- rosion of aluminium foil

Yes No Depends on

packaging materials

Selection of optimal packaging material.

Storage at lower temperatures

aIndirect effect possible because of different texture and mouth-feel.

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phenomena are related to precursors in the submicelle range.

Changes in Ionic Equilibria

After the melting and cooling of processed cheese, the ionic equilibria and hence the pH settle slowly. During storage, the loss of water vapour and the hydrolysis of polyphosphates in turn influence the ionic equilibria in processed cheese. In addition, interactions between protein, emulsifying salt, sodium and calcium influence water binding and texture. Processed cheeses typically become firmer during storage. Spreadable, ‘creamed’

products should be stored below 201C, preferably at 10–151C, to avoid a firmer, shorter texture (Chambre and Daurelles, 1997).

Formation of Crystals

Crystals are due to compounds with a low solubility.

The following possible crystals have been reviewed (Berger et al., 1989; Caric and Kalab, 1997; Uhlmann et al., 1983): calcium phosphate, calcium diphosphate, calcium lactate, lactose, crystalline amino acids such as tyrosine, and calcium tyrosinate. Crystals of emulsifying salts may be observed in processed cheese as a result of (i) an excess of emulsifying salt, (ii) an unsuitable mixture of emulsifying salts or (iii) insufficient dissolu- tion of the latter in the mixture during processing.

Tyrosine or other crystals may act as nuclei for the formation of further crystals (Berger et al., 1989;

W. Berger, pers. comms., 2000). In general, the formation of crystals is favoured by excessive amounts of emulsifying salts or lactose, a high calcium content in the natural cheese, a high pH-value and a long storage of the processed cheese at low temperatures (Caric and Kalab, 1997).

Crystallisation on the surface of processed cheese slices is influenced by mechanical treatments as well as the phosphates/citrates ratio in the emulsifying salt (Uhl- mann et al., 1983). Small white crystals, identified as calcium citrate or tertiary sodium calcium citrate, may occur on the surface of processed cheese slices (Berger et al., 1989).

Microcrystals of calcium phosphate and calcium pyro- phosphate dihydrate have been described (Pommert et al., 1988). These microcrystals do not affect the taste and the appearance of the processed cheese, in contrast with the other crystals responsible for spots or lines on the product surface.

Reactions Induced by Heat-stable Enzymes

Most enzymes are denatured and deactivated during processing. Nevertheless, denatured proteases may rearrange and exhibit a certain degree of proteolytic activity. Mulvihill and McCarthy (1993, 1994) examined proteolytic and rheological changes during the storage

of cheese analogues made from rennet casein. The plasmin content significantly influenced the proteolytic and rheological changes during 1–35 wk of storage.

Beta-casein was more extensively hydrolysed than as1- casein. As rennet (EC 3.4.23.4) is a relatively heat- sensitive enzyme, its activity in processed cheese seems negligible (Mulvihill and McCarthy, 1993). Heat-stable lipases may also be active: processed cheese made with ripe Camembert cheese may develop a noticeable lipolysis during storage (Morgenthaler, M. Gerber Cheese Ltd., Thun, Switzerland: pers. comms., 2000).

Nonenzymic Browning

Nonenzymic browning (‘Maillard reaction’) is an im- portant and widely occurring reaction in foods. The primary reaction is the carbonyl-amine addition between reducing sugars and amines (usually thee-amino groups of lysine). It is followed by rearrangements, scissions, hydrolyses and other carbonyl-amine reactions, as well as numerous further reactions (Feeney and Whitacker, 1982). The Maillard reaction and its prevention have been reviewed (Feeney and Whitacker, 1982;

Pizzoferrato et al., 1998; Yaylayan, 1997). Its relevance in processed cheese was discussed by Bergeret al. (1989).

It plays a key role in products containing high amounts of lactose (10–80 g/kg). During storage, especially at elevated temperatures, the formation of a brownish colour and an off-flavour limit the shelf-life of the product. The extent of Maillard reactions is reduced by a lower lactose content, less severe heating conditions and a lower storage temperature (Berger et al., 1989;

Piergiovanniet al., 1989). The influence of manufactur- ing procedures and composition of stirred-curd Cheddar cheese were investigated for their effects on the non- enzymic browning of processed cheese (Bleyet al., 1985).

The correlation between galactose content of Cheddar and the brown colour intensity in process cheese was very high. Faster cooling of processed cheese reduced the intensity of brown colour. In another study, non- enzymic browning of processed cheese was examined in a model system. The processing temperature and storage temperature were found to be more important factors than the concentrations of protein and lactose. The results indicated the advisability of storing processed cheese at low temperature (approx. 51C), since otherwise the Maillard reaction continues during storage (Piergio- vanniet al., 1989).

Reactions Induced by Light and Oxygen

Typical packaging materials for processed cheese include aluminium foils for portions, multilayer foils for slices, steel cans and cups (Sturm, 1998). Bossetet al.

(1993) and recently Borle et al. (2001) reviewed light- induced reactions in milk and milk products. These reactions may be relevant for slices in transparent foil, but do not occur in opaque packaging materials such as aluminium foils or steel cans. Processed cheese slices in

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transparent foil are usually conditioned under a protective atmosphere (nitrogen/carbon dioxide) with an oxygen content below 20 mL/L. Oxidative reactions leading to colour change (Kristensen et al., 2001) and the formation of off-flavour due to methional and carbonyl compounds as well as cholesterol oxides depend on processed cheese composition (oxidising and antioxidative components), light expose (emission spectrum, intensity, duration) and properties of the packaging. Studies on various milk products, including processed cheese, show, that the formation of cholester- ol oxides is negligible under normal processing and storage conditions (Bossetet al., 1993). The influence of different packaging materials (tin cans, polystyrene cups, LDPE tubs) and storage temperature was exam- ined in an Indian study (Goyal and Babu, 1991).

Samples packaged in tin cans had the least chemical changes.

Interactions with Packaging Materials

A typical aluminium foil (11–15mm) for processed cheese is coated with a protective polymer and a polyvinyl co-polymer with a sealing temperature of 65–751C (Sturm, 1998). This coating protects the aluminium from corrosion due to salts and acids present in the matrix and also prevents the undesirable migration of aluminium into the cheese body. Factors leading to the corrosion of aluminium foils have been described (Flu¨ckiger, 1964; Berger et al., 1989; Meyer, 1970). In an off-flavoured product packed in aluminium foil, Stark and Urbach found that the contaminant was the vinyl monomer (G. Urbach, unpublished work by Stark and Urbach, pers. comms. 2001).

Interactions with packaging materials were reviewed by Gallmannet al. (1997). The migration of butylhydrox- ytoluene (BHT) and Irganox 1010 into processed cheese slices was measured (Schwope et al., 1987). Migration strongly depended on molecular weight: BHTwith a low molecular weight migrated faster than Irganox 1010.

Conclusions

Processed cheese is a ‘semi-preserved food’ with a limited shelf-life. Products without bacteriological spoi- lage retain their good quality typically only for 4–12 mo at room temperature. During storage, appear- ance, structure, colour and flavour slowly change. The possible causes of these changes are: loss of water, hydrolysis of polyphosphates, changes in ionic equili- bria, formation of crystals, oxidation, nonenzymic browning, enzyme activity, interactions with packaging materials. Several mechanisms for these changes can be active concurrently.

The changes with the age of processed cheese can be influenced by four main factors: product composition, processing, packaging and storage conditions (tempera- ture and duration). Firm products retain their quality longer than spreadable products with higher water

content. Other compositional factors such as lactose content or emulsifying salts also influence the shelf-life.

Most changes with age can be slowed down by lower storage temperatures.

While these global effects of storage on processed cheese are well known, this review clearly highlights the need for further research on specific topics such as changes in equilibria and interactions between the product compo- nents. The chemistry of the system during the ‘hard- ening’ of processed cheese as well as discrepancies between effects noted by various authors in different studies should still be experimentally explored and explained. Moreover, two main fields should be investigated: the storage of ready-made fondue, which was never dealt with, and the relationship between storage duration and storage temperature.

Acknowledgements

We are grateful to Mr Wolfgang Berger (Ro¨merberg, Germany), Mrs Annie Imbert (Fromageries Bel, Ven- doˆme, France), Mr Robert Sieber (FAM) and Mrs Gerda Urbach (Australia) for their careful review of the manuscript.

References

BERGER, W., KLOSTERMEYER, H., MERKENICH, K. AND

UHLMANN, G. Die Schmelzka¨seherstellung. Ladenburg:

Benckiser-Knapsack GmbH (1989)

BLEY, M. E., JOHNSON, M. E. AND OLSON, N. F. Factors affecting nonenzymatic browning of processed cheese.

Journal of Dairy Science,68, 555–561 (1985)

BORLE, F., SIEBER, R.ANDBOSSET, J. O. Photo-oxidation and photoprotection of foods, with particular reference to dairy products. An update of a review article (1993–2000).

Sciences de Aliments,21, 579–598 (2001)

BOSSET, J. O., GALLMANN, P. U. ANDSIEBER, R. Einfluss der Lichtdurchla¨ssigkeit der Verpackung auf die Haltbarkeit von Milch und Milchprodukten - Eine U¨bersicht.Mitteilungen aus dem Gebiete der Lebensmittel und Hygiene, 84, 185–231 (1993)

CARIC, M. AND KALAB, M. Processed cheese products. In:

FOX, P. F. (Ed). Cheese: Chemistry, Physics and Microbiology. London, New York: Elsevier Applied Science, pp. 467–505 (1997)

CHAMBRE, M. AND DAURELLES, J. Le fromage fondu. In:

ECK, A. AND GILLIS, J. C. (Coordinateurs). Le Fromage.

Paris: Technique et documentation Lavoisier, 3rd Edn, pp. 691–708 (1997)

EIDGENO¨SSISCHES DEPARTEMENT DES INNERNVerordnung u¨ber die in Lebensmitteln zula¨ssigen Zusatzstoffe, Bern: SR 817.021.22, 30.Januar (1998)

FEENEY, R. E. AND WHITACKER, J. R. The Maillard reac- tion and its prevention. In: CHERRY J. P. (Ed).

Food Protein Deterioration. Mechanisms and Functionality.

ACS Symposium Series, vol. 206. Washington, DC:

American Chemical Society, pp 201–229 (1982)

FLU¨CKIGER, E. Korrosion der Alufolie als Ursache fu¨r die Bla¨hung von Schmelzka¨se.Schweizerische Milchzeitung,90, 231 (1964)

GALLMANN, P. U., BOSSET, J. O.ANDSIEBER, R. Lebensmittel, Verpackung und Stoffmigration,Lebensmittel-Technologie, 30, 326–336 (1997)

(6)

GOYAL, G. K.AND BABU, K. E. Influence of packaging and storage on the chemical quality of processed cheese.Indian Journal of Dairy Science,44, 274–279 (1991)

KLOSTERMEYER, H. Zur Struktur des Schmelzka¨ses - Fakten und Hypothesen.Die Molkerei-Zeitung Welt der Milch,44, 214–219 (1990)

KRISTENSEN, D., HANSEN, E., ARNDAL, A., TRINDERUP, R. A.

ANDSKIBSTED, L. H. Influence of light and temperature on the colour and oxidative stability of processed cheese.

International Dairy Journal11, 837–843 (2001)

MAIR-WALDBURG, H. Anwendung und Wirkung kondensierter Phosphate in Milcherzeugnissen. Kondensierte Phosphate in Lebensmitteln. Giessen: Bru¨hlsche Universita¨tsdruckerei, pp. 104–121 (1958)

MARIACA, R., GAUCH, R., BERGER, T., BOSSET, J. O. AND

SCHA¨R, W. Volatile compounds of Swiss processed cheese.

Mitteilungen aus dem Gebiete der Lebensmittel und Hygiene, 89, 625–638 (1998)

MEYER, A.Joha-Schmelzka¨sebuch, Ludwigshafen: Benckiser- Knapsack GmbH (1970)

MULVIHILL, D. M. AND MCCARTHY, A. Proteolytic and rheological changes during ageing of cheese analogues made from rennet caseins. International Dairy Journal, 4, 15–23 (1994)

MULVIHILL, D. M.ANDMCCARTHY, A. Relationships between plasmin levels in rennet caseins and proteolytic and rheological changes on storage of cheese analogues made from these caseins. Journal of Dairy Research,60, 431–438 (1993)

NEY, K. H. Gera¨t zur Messung des Biegebruchverhaltens von Schmelzka¨sescheiben.Alimenta,2, 31–36 (1988)

PAQUET, D. La fonte des fromages: aspects physico-chimiques.

Cahier ENSBANA, Dijon: Janvier, pp. 227–241 (1988) PIERGIOVANNI, L., DE NONI, I., FAVA, P. AND SCHIRALDI, A.

Nonenzymatic browning in processed cheeses. Kinetics of

the Maillard reaction during processing and storage.Italian Journal of Food Science,1, 11–20 (1989)

PIZZOFERRATO, L., MANZI, P., VIVANTI, V., NICOLETTI, I., CORRADINI C. AND COGLIANDRO E. Maillard reaction in milk-based foods: nutritional consequences.Journal of Food Protection,61, 235–239 (1998)

POMMERT, J. F., LLAEBE, J., PERIE, J., LEBUGLE, A.ANDPUECH, J. Observation and analysis of crystalline phases in processed cheese. Journal of Food Science, 53, 1367–1369, 1447 (1988)

RUF, F.ANDGLA¨SER, A Einfluss der Hoch-Kurz-Sterilisation auf mechanische Eigenschaften des Schmelzka¨ses und dessen Phosphat-Schmelzsalze. Die Molkerei-Zeitung Welt der Milch,25, 1197–1201 (1971)

SCHWOPE, A. D., TILL, D. E., EHNTHOLT, D. J., SIDMAN, K. R., WHELAN, R. H., SCHWARTZ, P. S.AND REID, R. C.

Migration of BHTand Irganox 1010 from low- density polyethylene (LDPE) to foods and food-simulating liquids. Food Chemistry and Toxicology, 25, 317–326 (1987)

STURM, W. Verpackung milchwirtschaftlicher Lebensmittel.

Kempten: Edition IMQ (1998)

SWISS ASSOCIATION OF PROCESSED CHEESE MANUFACTURERS

(SESK),Jahresbericht 2000, Elfenstrasse 19, Postfach, CH- 3000 Bern 16 (2001)

UHLMANN, G., KLOSTERMEYER, H. AND MERKENICH, K.

Kristallisationserscheinungen in Schmelzka¨seprodukten - I.

Pha¨nomen und Ursachen. Milchwissenschaft 38, 582–585 (1983)

YAYLAYAN, V. A. Classification of the Maillard reaction:

A conceptual approach. Trends in Food Science and Technology,8, 13–18 (1997)

ZEHREN, V. L.ANDNUSBAUM, D. D.Process Cheese. Madison, Wisconsin: Cheese Reporter Publishing Company, Incorporation, (1992)

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