Food Safety Cheese Basic Course

Transcription

1 Food Safety Cheese Basic Course Didactic Unit 5: Characteristics of cheese

2 FoodSafety Cheese Continuous training on food safety in milk production centres and cheese industries. FoodSafety Cheese is a transfer of innovation project under LLP Leonardo da Vinci Program. It is transferred from Seguralimentaria and it is adapted to the European cheese industry sector and milk production centres related to these industries with the aim to improve quality and efficiency of the learning processes by means of design and validation of training materials based on new technologies of information and communication (NTIC) which improve vocational education and training (VET). This test, corresponding to the Food Safety Cheese Basic Course, has been drawn as a part of the FoodSafety Cheese project, part of the community vocational training action programme Leonardo da Vinci of the European Commission. Promoter and coordination organizations of the project: BETELGEUX, S.L. Paseo Germanías, Gandía Spain FEDERACIÓN AGROALIMENTARIA DE CC.OO. Pza. Cristino Martos, Madrid. España Partners involved in the project: Ecole d Ingenieurs de Purpan 5, voie du TOEC BP TOULOUSE Cedex 3 MINISTRY OF FOOD, AGRICULTURE AND LIVESTOCK General Directorate of Food and Control Eskisehir Street 9Km Lodumlu -Ankara TURKEY

3 UNION OF AGRICULTURAL COOPARATIVES OF LARISSA TYRNAVOS AGIA Hatzhmichali 81, GR Larissa GREECE Association of Private Farming of the CR Dělnická Prague 7 CZECH REPUBLIC Associates of the project: ASOCIACIÓN AGRARIA JÓVENES AGRICULTORES GRANADA C/ Sevilla, 5-BAJO. CP GRANADA Spanish Food Safety and Nutrition Agency Web page of the project: This project has been funded with support from the European Commission. This publication reflects the views only of the author, and the Commission cannot be held responsible for any use which may be made of the information contained therein.

4 Food Safety Cheese Basic Course INDEX Introduction Didactic Unit 1: Food Safety. What is food safety? Relationship between health and food. Foodborne illnesses. Food safety at this time. The most serious problems related to food safety. Food safety in Europe: The White Paper on Food Safety. The importance of the cheese producers and handlers to food safety. Most significant legislation. Didactic Unit 2: The Cheese Food Chain and Traceability. What is the food chain? Stages in the chesse chain: feed production; milk production; the cheese industry; retail distribution and sales; hotel and catering trade and household consumption. The complexity of the food chain. The concept of traceability. Instruments and advantages of traceability. Didactic Unit 3: Milk composition and physical-chemical characteristics. Milk composition. Milk quality concepts: - Physical-chemical characteristics. - Hygienic and sanitary characteristics. Didactic Unit 4: Milk production centers. Feeds, inhibitors and antibiotics. Farm: Biosecurity. Milking. Handling and Hygiene rules in milk production. The cold chain and transport conditions. Didactic Unit 5: Characteristics of cheese. Cheese composition. Cheese quality concepts: - Physical-chemical characteristics. - Hygienic and sanitary characteristics: main microorganisms. Shaping and pressing. Salting process. Ripening. Packaging and refrigerated storage. Didactic Unit 7: Hygiene in cheese Production and Handling. Cross contamination. Principles of personal hygiene. Good working practices and occupational health. Cleaning and disinfection. Didactic Unit 8: Food Hazards. Biological hazards. Chemical hazards: Includes allergens. Physical hazards. Didactic Unit 9: HACCP System and food safety management systems. Definition and Principles of the HACCP System. Critical control points. Food safety management systems: BRC, IFS, ISO Didactic Unit 10: Food safety and the environment. Sustainable food production. Environmental contaminants. Bibliography and references. 4

5 Basic Course Food Safety Cheese Didactic Unit 5: Characteristics of cheese. Chesse composition. Chesse quality concepts: - Physical-chemical characteristics. - Hygienic and sanitary characteristics: main microorganisms. For many thousands of years, the conversion of liquid milk into cheese has been practised. Cheese is the fresh or matured product obtained by removal of serum after coagulation of raw or heat treated milk, whole or partially skimmed milk. It is a very nutritious dairy food as milk is the main basic ingredient. Other ingredients involved in the production of cheese are rennet, microorganisms and salt, which are processed through a number of common steps such as gel formation, whey expulsion, acid production and salt addition, followed The primary objective of cheese by a period of ripening, if applicable. Therefore, cheese manufacture originally was to extend the is an important component of our food supply and shelf life and conserve the nutritious there is a wide range of varieties of cheese that satisfies components of milk. consumer needs. For instance, not long ago, low-fat cheese variants have been introduced to the market due to the emergence of a diet-conscious market. According to FAO, in 2009 the worldwide production of all types of cheese was about tonnes and in Europe was of tonnes. 5

6 Food Safety Cheese Basic Course In the European Union the consumption of cheese per capita has been reported to be 13.2 kg/year. Greece has the highest per capita consumption of kg/year (FAO Food Balance Sheets, 2007). Cheese composition. A high concentration of essential nutrients are found in cheese. Its composition mainly depends on the composition of the milk used (whole, skimmed or partially skimmed milk) and the cheese making process. In the cheese curd the water-insoluble nutrients of milk are retained: coagulated casein, colloidal minerals, fat, fat-soluble vitamins. However, the water-soluble milk components are removed with the whey: whey proteins, lactose, water-soluble vitamins and minerals. Cheese making is basically a dehydration process in which the fat and casein in milk are concentrate. Many studies have shown that a higher casein content in milk improves coagulation properties, whereas fat content only increase cheese yield. The protein content of cheese varies with the manufactured process. Table 1. Composition of selected cheese per 100 g (Holland et al., 1989). Cheese type Water Protein Fat Carbohydrate Cholesterol Energy (g) (g) (g) (g) (mg) Kcal KJ Brie Tr Caerphilly Camembert Tr Cheddar (normal) Cheddar (reduced fat) Tr Cheshire Cottage cheese

7 Characteristics of cheese - Unit 5 Cheese type Water Protein Fat Carbohydrate Cholesterol Energy (g) (g) (g) (g) (mg) Kcal KJ Cream cheese Tr Danish blue Tr Edam Tr Emmental Tr Feta Fromage frais Gouda Tr Gruyere Tr Mozzarella Tr Parmesan Tr Processed cheese* Ricotta Roquefort Tr Stilton Tr, trace *Variety not specified Cheese quality concepts: The quality of cheese depends on several aspects such as safety, nutritional, flavour, texture, functionality or appearance. It is well known that the quality of the milk supply has a major impact on quality from the chemical and microbiological viewpoints and consistency of the resultant cheese. Three characteristics of quality must be considered: microbiological, physical and chemical properties. Physical-chemical characteristics of cheese. The quality of cheese is mainly influenced by its moisture content, NaCl concentration, ph, moisture-in-non-fat substances (MNFS; essentially the ratio of protein to moisture) and the 7

8 Food Safety Cheese Basic Course percentage of fat-in-dry matter. Protein The biological value of cheese protein is slightly less than milk protein due to the removal of globulins and albumins during draining, it still contains all of the essential amino acids in the amounts proportional to the body s needs. On the other hand, in cheese the digestibility of protein is higher than that of whole milk due its breakdown during ripening to peptides and amino acids. The protein content of different kinds of cheese goes from 4 to 40% (Table 1), varying inversely with the fat content of milk. Casein is the main protein in cheese. It has been shown that higher quantities of casein in milk affects curd formation in less time, is firmer and more contractible and helps create a more uniform removal of whey. Previously, whey from cheese or casein production was considered a waste material which was fed to farm animals, irrigated on land or disposed into sewers. Economic and environmental considerations now dictate that whey be used more efficiently. The principal products produced from whey are: various whey powders, whey protein products which are produced mainly by membrane technology, lactose and its derivatives. P.F. Fox, Lactose: Chemistry and Properties in Advanced Dairy Chemistry: Volume 3: Lactose, Water, Salts and Minor Constituents Springer; 3rd ed. edition, 2009, p Milk proteins remaining in the serum after precipitation of caseins are known as whey proteins and account for about 20% of total protein in milk. In cheese, the amount of whey proteins depends on the amount of whey entrapped in the curd, representing only 2-3% of the total protein in cheese. Carbohydrate During cheese manufacture most of the lactose (98%), the principal carbohydrate in milk, is lost in whey and thus most cheeses contain only a trace amount of carbohydrate. Moreover, the residual lactose in cheese curd is converted to lactic acid by bacterial action. The fermentation of lactose due to bacterial β-d-galactosidase, make cheese digestible by lactose intolerant individuals. To control the cheese quality, acid production is essential since it determines the final ph and mineral content of the curd. Fat As previously mentioned, depending on the milk used and the manufacture process, the fat content of cheese varies considerably and ranges from approximately 4-48g/100g of cheese 8

9 Characteristics of cheese - Unit 5 (Table 1). Fat content in cheese plays an important role as it is responsible for: lubrication, the creamy mouth feel, for flavour and it also affects firmness. Usually, cheese fat is composed by 66% saturated, 30% mono-unsaturated and 4% polyunsaturated fatty acids. Of the different fatty acids found in milk only C12:0, C14:0 and C16:0 have the property of raising blood cholesterol. Furthermore, short chain fatty acids such as butyric acid (C4) are responsible for typical flavours of cheeses. Vitamins For the dairy industry, reduce fat and sodium content in cheese, maintaining safety and quality, is still a challenge. Due to whey removal, the content of water-soluble vitamins in cheese is lower than fatsoluble vitamins. In general, most cheeses are good sources of vitamin A, riboflavin, vitamin B 12 and folate. Minerals Cheese is a good source of many minerals such as phosphorus, magnesium and, particularly, calcium. The calcium content of cheese mainly depends on the acidity at coagulation and the quantity of whey expelled from the curd. The content of sodium in different kinds of cheese also varies with the manufacturing procedure due to different amounts of salt added during cheesemaking. Generally, the salt content of processed cheeses tends to be higher than that of natural cheeses. There are a number of physical parameters that vary with the cheese making process and are responsible for the control of the growth of microorganisms in cheese: ph The level of acidification during processing, the buffering capacity of cheese curd and, in certain cases, de-acidification during ripening determine the ph of cheese. Cheeses with high ph levels are softer than those that show lower ph levels. Furthermore, a short variation in ph may influence on rheological properties of cheese by affecting parameters such as softness, adhesiveness or longness among others which are essential in 9

10 Food Safety Cheese Basic Course determining its suitability for sliceability, for example. a w a w is defined as the relationship between the vapor pressure of the food (ρ) and that of pure water (ρ 0 ) at the same temperature: a w = ρ/ ρ 0. The moisture content, ph, NaCl and other low molecular weight compounds such as ash and nonprotein nitrogen are responsible for the a w of cheese. Thus, an increase in the moisture content of cheese means an increase in susceptibility to spoilage because water is a parameter required for the growth of microorganisms. For this reason, reducing the availability of water either through dehydration or addition of water soluble components such as sugar or salt, is the best way to control microorganism growth. Salt concentration Some effects of salt addition are: Control of activity and microbial growth; Control of the several enzyme activities in cheese; Complementary moisture reduction in cheese, which also influences the above; Physical changes in cheese proteins which influence cheese texture, protein solubility and probably protein conformation. Crust formation. Hygienic and sanitary characteristics: main microorganisms. Cheese-making started centuries ago as a means of conservation of raw milk trough fermentation, it has become a food sector of high economic importance in many countries. Whereas, many dairy products, are biologically, biochemically, chemically and physically stable, if correctly manufactured and stored; cheeses are, biologically and biochemically dynamic, and, consequently, are intrinsically unstable. The first objective in cheese-making is to obtain a curd with the desired chemical composition and with the desired micro-flora. Bacteria, molds and yeast are present in cheese during ripening and contribute to the maturation process either directly through their Main pathogenic bacteria that represent the greatest risk to the safety of cheese: - Salmonella enterica, - Listeria monocytogenes, - Staphylococcus aureus and - Enteropathogenic Escherichia coli. 10

11 Characteristics of cheese - Unit 5 metabolic activity or indirectly through the liberation of enzymes into the cheese matrix through autolysis. However, cheese may contain other microorganisms, spoilage or pathogenic microorganisms, which are present at the very beginning in the milk used or are added in subsequent steps of the cheese manufacture, if sanitation and other measures are not sufficient to prevent contamination during processing. To guarantee the safety of cheese it is necessary to take into account several aspects such as milk quality, starter culture or native lactic acid bacterial growth during cheese-making, ph, salt, food preservative added, aging conditions and chemical changes during cheese aging, as well as proper cheese manufacturing practices. Other parameters that affect microbial growth in cheese include aspects such as kind of packaging, time and temperature of storage and handling conditions. Microbiological tests of yeasts and molds, total coliforms and Staphylococcus must be peformed at the cheese industry during processing and after curing. All tanks for raw milk cheese should be analysed for the presence of Salmonella, Staphylococcus, Listeria monocytogenes and enteropathogenic E. coli. The presence of pathogens in cheese made from heat treated but not pasteurized milk should be also monitored on a regular basis. On the other hand, cheese whey must be also monitored for the presence of specific bacteriophage for the culture in use. The beneficial natural flora in milk such as Lactococcus lactis, Streptococcus thermophilus, Lactobacillus delbrueckii and Lb. helveticus are regarded as starter bacteria responsible for acid production during manufacture and, thus, of reducing the ph of milk rapidly, they are also known as starter lactic acid bacteria (LAB). Together with starter bacteria there is a secondary micro-flora that helps to preserve products and in many cases allows competition with bacterial pathogens and is involved in the ripening process but it does not play any role during cheese processing and may be divided into different groups: Non-starter lactic acid bacteria (NSLAB) consisting of non-starter Lactobacillus, Pediococcus, Enterococcus and Leuconostoc, propionic acid bacteria (PAB), Molds, Bacteria and yeast, which grow on the surface of smear-ripened cheeses. The milk enzymes, the SLAB and NSLAB, rennet and polluting micro-flora enzymes with other optimum chemical and physical properties of Leuconostoc are mesophilic heterofermentative lactic acid bacteria, which are characterized by the ability to produce CO 2 from lactose. Another property of leuconostocs is the production of diacetyl and acetoin responsible for eye formation and aroma compound in fresh cheese and soft type Cottage. In addition, this bacteria has a specific interest for blue-veined cheese as it is responsible of an open texture in the curd to enable a proper fungal grain, e.g. Penicillium roqueforti, also contributing to the inhibition of growth of mold contaminants sensitive to elevated CO 2. 11

12 Food Safety Cheese Basic Course milk previously studied, especially the concentrations of casein, fat, calcium and ph, are the main agents responsible for transformation of milk in cheese (glycolysis, proteolysis, lipolysis). For this reason, for the producers of raw milk cheeses, milk quality is particularly important. Milk quality indicators are low bacterial counts and low somatic cell counts, since high counts produce enzymes that degrade proteins, fats and other components of milk, resulting in off-flavors and odours in the cheese produced. Cheese-makers also should consider that milk must be free from antibiotics, which cause the inhibition of the starter bacteria and delay the acidification resulting in a deficient composition and micro-flora and thus in abnormal flavour and texture due to the growth of pathogenic microorganisms. A wide range of cheese varieties are made from raw milk, especially in small-scale artisan factories where in many cases milk comes directly from the farm using very fresh milk from healthy animals. Clearly, raw milk cheese is safe if adequate precautions are taken: milkscreening procedures, GMPs and HACCP. In bigger industries, it is considered that goodquality raw milk is too variable to be used successfully and instead of raw milk pasteurized milk is used to avoid negative impacts on cheese quality that may reduce consumer acceptability and cheese yield. Pasteurization is used to destroy pathogens and standardise the milk micro-flora. In addition, some microorganisms present in cheese can cause spoilage. Thus, another beneficial effect of pasteurization is the killing of spoilage microorganisms such as coliforms, pseudomonas and yeasts. Some examples of spoilage are: Fruity and bitter off-flavors, gassy and open texture attributed to yeast activity. Growth and production of gas by coliform bacteria due to slow lactic acid production of starter cultures. Although, pasteurization has contributed to ensure the safety of cheese, to avoid or minimize contamination in cheese by spoilage or pathogenic microorganisms, good on-farm hygiene, bactofugation or micro-filtration of milk, good hygiene practices during production and handling of cheese, or addition of additives will be essential. 12