PART III PROCESS SAFETY
3. Preliminary Tasks
2.8. Chemical control
The chemical control programme ensures the elimination of hazardous chemical substances from food. Chemical hazards, which can be found in a dairy industry, include sanitizers, pesticides, mycotoxins, allergens, refrigerants, solvents, and acids. These materials may interact with the raw materials and the ingredients or the additives and the equipment producing untoward effects. Certain chemicals are also used for food processing, cleaning, sanitation and pest control. Generally, chemical control procedures are related to receiving, storage, usage and disposal of chemicals.
2.9. Supplier control
The supplier control programme provides the company with a tool to evaluate the suppliers of raw materials, ingredients and services. Without an effective supplier control programme, the HACCP system can easily fail to provide safety assurance. The description of the industry requirements from the suppliers is of primary concern. These include the HACCP programme of the supplier, certifi- cates of analysis, and records of applied prerequisite programmes.
2.10. Trace and recall
The trace and recall programme is used to control the movement of food products from the reception of raw materials and ingredients to the distribution of final products. This programme provides the company with the ability to withdraw products defective or dangerous to human health. The establishment of an effective withdrawal programme includes recorded recall procedures, in which comprehen- sive information about the process and the responsible personnel are retained. This would include information regarding, raw materials, finished products coding, customer complaints and appropriate handling of recalled products.
2.11. Equipment calibration
Equipment used during food processing should be standardized and calibrated.
Equipment such as thermometers and pH meters, whose functionality affects food safety, must be calibrated on a regular basis. Certificates provided by national or international organizations are a means of ensuring reliability.
to effect implementation and maintenance of the HACCP system. The team, on the other hand, should clearly define the goals of the programme together with when it is expected to be operational (Surak, 2002). The HACCP team leader is responsible for coordination of the other team members and the provision of an effective HACCP system. Balanced representation from all plant departments in the HACCP team, is also important. A HACCP team should include scientists with different technical or scientific backgrounds as well as personnel with tech- nical and practical knowledge of all stages of the manufacturing process.
3.2. Description of the product
Since HACCP system design is product specific, the second preliminary task is to describe this product (e.g. intrinsic factors of the product such as pH or aw).
‘Feta’ cheese is a traditional white brined cheese, which has been produced in Greece since ancient times. It is made exclusively from ewe’s milk or from a mix- ture of ewe and goat’s milk and it is ripened in brine for two months. Feta cheese can only be produced under strict product specifications in certain areas of Greece. Feta is registered as a Protected Designation of Origin (PDO) product.
3.3. Description of the intended use and end user
Feta cheese is consumed primarily as it is, or less commonly, cooked. It has high nutritional value and is consumed by all groups of the population (except infants).
3.4. Developing the process flow diagram
During the development of the process flow diagram, the HACCP team should describe each step and operation that takes place during the manufacturing of the specific food. The flow diagram is a very important tool required by the HACCP team for the development and implementation of an effective HACCP plan. The flow diagram is also utilised by the auditors of the competent authorities called in to scrutinise the programme; these individuals, must understand all aspects of the manufacturing process during the evaluation of the HACCP programme.
The flow diagram should depict the processing steps controlled by the company.
Furthermore, it may include steps that precede or follow the processing operation, such as receiving of raw materials, storage and possible pre-treatment of them, handling, packaging, storage, distribution or usage of the end-product. The flow diagram should be detailed and contain a variety of data and information on raw materials, ingredients, and packaging materials. It should also provide information on the layout of the factory, equipment, relationship between temperature and time for every step of the processing operation from receiving and storage of raw mate- rials to handling of intermediate and end-products. Furthermore, the flow diagram may contain information about the storage and distribution of the end-product. The flow diagram for the production of Feta cheese is illustrated in Fig. 1. An outline of the Feta cheese flow diagram is given below.
3.4.1. Milk collection and reception
Milk is collected and transported from the farms to the dairy industry in refriger- ated milk cans (churns). On reception at the dairy plant, the milk is firstly exam- ined and weighed on a platform balance. Routine examination, by experienced personnel, of the content of each milk churn includes odour, colour, texture and
COLLECTION OF MILK
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CENTRIFUGAL SEPARATION-STANDARDIZATION
PASTEURIZATION (68⬚C for 10 min)
STORAGE AT 34-36⬚C
ADDITION OF STARTER CULTURES ADDITION OF RENNET AND CaCl2
(clotting at 35-36⬚C for 50 min) CUTTING OF THE CURD/GEL INTO CUBES
MOULDING
FIRST SALTING (12 hours)
SECOND SALTING (2 days at 15-16⬚C)
WASHING WITH BRINE OR COLD WATER
PACKAGING INTO BARRELS - ADDING OF PASTEURIZED BRINE
PRE-RIPENING (at 15-16⬚C for 15-20 days)
RIPENING – STORAGE (at 2-3⬚C for 2 months) FIGURE1. Flow diagram of Feta cheese.
temperature. In addition, the milk should be tested for the presence of antibiotics and acidity. The milk, which has been certified as appropriate for cheese manu- facturing is then stored at 4°C (in milk tanks) for a time that should not exceed 24 hours (Walstra et al., 1999).
3.4.2. Centrifugal separation
The aim of this procedure is to remove foreign objects and dirty particles from the milk. Another purpose is to separate the fat content of the milk. In the next step, the fat will be mixed again with skimmed milk to standardize it to a desired fat content. There are several types of milk separators currently commercially available (Abd El-Salam et al., 1999).
3.4.3. Milk standardization
The standardization of milk refers to the adjustment of its fat content to a legally determined percentage. The rationale used for the standardization of the milk for the manufacturing of Feta cheese, is the ratio of its fat content to its crude protein (casein). A fat to crude protein (casein) content of 1.2/1 ensures production of high quality Feta cheese.
3.4.4. Pasteurization
During this step, the milk is treated at 68°C for 10 min. Pasteurization destroys pathogenic microorganisms and enzymes harmful for the ripening. This thermal treatment is sufficient to inactivate alkaline phosphatase but not superoxide dis- mutase. A more intense thermal pasteurization above 78-80°C would inactivate superoxide dismutase but this would cause denaturation of milk proteins, through the formation of κ-casein and serum proteins complexes. As a result the ren- netability and the syneresis of the curd are decreased (Zerfiridis, 2001).
3.4.5. Addition of the starter culture
An appropriate starter culture is essential for the quality of the product. The lac- tic acid bacteria used for the production of Feta cheese are Streptococcus ther- mophilus, Lactococcus lactis subsp. lactis and Lactobacillus delbrueckii subsp.
bulgaricus. The starter cultures should be of excellent quality. It is applied at 1%
v/v and the inoculated milk is incubated for 30 min.
3.4.6. Addition of rennet and CaCl2
Cheese is produced by milk clotting through the action of chymosin that is the main component of rennet. This step is primarily essential for the development of a uniform gel and finally Feta with firm texture. Factors that affect the clotting with rennet are milk acidity, temperature and the amount of rennet added. This amount is usually 1.0-3.0 g rennet, of rennet strength 1: 100.000, for 100 litre of milk. The milk should be at rest during clotting for 30-60 min at 30-35°C.
Additionally to rennet, an aquatic dilution of calcium chloride (40%) is added with a maximum amount equal to 200 cm3/ 1000 l milk.
3.4.7. Cutting of the coagulum and moulding
After coagulation caused by rennet has been completed, the curd/gel formed is cut in 2-3 cm cubes, ladled in thin layers into perforated metal moulds and kept at rest for 5-6 hours for syneresis to occur. A very important factor for this essen- tial stage of Feta production is temperature. The temperature of the operation plants, where syneresis as well as salting takes place should be 16˚C. At this tem- perature a product of better texture and flavour is produced. When curd is firm enough to remove the moulds, it is cut into four sub-blocks of 23 x 12 x 6 cm.
3.4.8. Salting
Salting of Feta cheese takes place in two stages. The first stage includes dry salt- ing and takes place on a salting table, where the blocks of curd are placed. Coarse salt is sprinkled on the surface of the cheese to allow its slow penetration into the curd. Dry salting is repeated two or three times every 12 hours. During the second stage of salting, Feta is kept immersed in a concentrated solution of NaCl (brine).
The final concentration of salt in Feta cheese should be 3-4%. Salt combined with acidity (pH < 5.1) is essential for the quality and safety of the final product.
3.4.9. Ripening
Maturation of Feta cheese actually begins before the curd making is finished, and can be separated into two phases. The first one takes place simultaneously with dry salting in the ripening plants, at 18˚C, while the second one occurs during the storage of Feta in refrigeration. The duration of the first phase or pre-ripening is approximately 15 days. During this time, syneresis is completed while a wide range of biochemical reactions takes place.
3.4.10. Storage and packaging
During the final stage of the Feta cheese flow diagram, Feta is packed in either wooden barrels or tin cans. Containers should be thoroughly cleaned. Following packaging, the containers should be filled with brine. The brine added should cover the upper surface of the cheese in the container but it must also allow a free space of 2 cm. Then, it is kept at 14-16˚C until a pH of 4.6 and moisture content less than 56% are reached. At this time, the containers are sealed and stored at 4-5˚C. The relative humidity of the plant where maturation of Feta cheese takes place should be 95-100%. Care should be taken so that the surface of the cheese is completely covered with brine (Zerfiridis, 2001).
3.5. Verifying the accuracy of the process flow diagram
After the flow diagram of the manufacturing of the specific food has been developed, the HACCP team should regularly inspect the plants of the industry to
verify its implementation and accuracy. The inspection of the manufacturing processes is essential for the validation of how clearly the flow diagram depicts the process. The person responsible for the verification of the flow dia- gram is the quality and safety assurance manager. Moreover, the HACCP team must evaluate all the data concerning the production. Consultations or observa- tions should take place and cases of deviations recorded. The HACCP team should conduct inspections every month without notice, at any time during working hours.