Lesson 27. PROCESSED CHEESE AND RELATED PRODUCTS
Module 12. Manufacture of processed cheese and related products
PROCESSED CHEESE AND RELATED PRODUCTS
Processed cheese is a product made by blending natural cheese of different ages in required proportion with emulsifying salts followed by heating and continuous mixing to form a homogeneous mass. Processed cheese was initially manufactured with the aim of increasing the shelf life of natural cheese. Manufacturing of process cheese involves blending of cheeses of different age. These allows sub-graded cheeses like gassy, highly acidic etc. to be utilized, instead of those getting wasted.
According to FSSR (2011), ‘Processed Cheese’ means the product obtained by grinding, mixing, melting and emulsifying one or more varieties of cheeses with the aid of heat and emulsifying agents. It may contain cream, butter, butter oil and other milk products subject to maximum 5.0 per cent lactose content in the final product and edible common salt, vinegar/acetic acid, spices and other vegetable seasoning and foods other than sugars properly cooked or prepared for flavoring and characterization of the product provided these additions do not exceed one sixth of the weight of the total solids of the final product on dry matter basis and cultures of harmless bacteria and enzymes. It shall have pleasant taste and smell free from off flavor and rancidity. It may contain food additives permitted in the regulation and it shall conform to the microbiological requirements as prescribed in the regulation. It shall have moisture not more than 47% and milk fat not less than 40% on dry matter basis.
FSSR (2011) has defined Process Cheese Spread as the product obtained by grinding, mixing, melting and emulsifying one or more varieties of cheese with emulsifying agents with the aid of heat. It may contain Cream, Butter oil and other dairy products, subject to a maximum limit of 5.0 percent lactose in the final product, salt, vinegar, spices, condiments and seasonings, natural carbohydrate sweetening agents namely sucrose, dextrose, corn syrup, corn syrup solids, honey, maltose, malt syrup and hydrolysed lactose and food properly cooked or otherwise prepared for flavoring and characterization of the product provided these additions do not exceed one sixth of the weight of total solids of the final product on dry weight basis and cultures of harmless bacteria and enzymes. It shall have pleasant taste and flavor free from off flavor and rancidity. It may contain permitted food additives and shall conform to the microbiological requirements as prescribed in the regulation. It shall have moisture not more than 60% and milk fat not less than 40% on dry matter basis.
27.2 Classification of Processed Cheese Products
As per Code of Federal Regulations (CFR), USA, there are three main categories of process cheese viz., pasteurized process cheese (PC), pasteurized process cheese food (PCF), and pasteurized process cheese spread (PCS). Table 27.1 summarizes the compositional specifications (CFR, US and FSSR, India) and the major ingredients which are used in their preparation.
Table 27.1 Categories of cheese and their specifications
27.3 Preparation of Process Cheese
The manufacturing of process cheese involves selection and computation of ingredients, their blending and shredding, addition of emulsifying salts, heating, packaging, cooling and storage.
27.3.1 Selection and computation of ingredients
It involves selection of type of cheese and various ages of cheese, emulsifying salts, water and other optional ingredients to give process cheese the desired composition, textural and functional properties. The major constituent of process cheese is cheese. Types of cheese, degree of maturity and the blend selected for processed cheese have a major influence on textural attributes of the final product. Processed cheese can be made from only one or several types of cheeses. A blend of cheese having varying degree of maturity is selected on the basis of required flavor and texture in the finished product. General formulation of processed cheese is 70-75% mild cheese and 25-30% medium aged or mature cheese. For producing processed cheese in slices, Kosikowski had suggested a blend composition of 55% young, 35% medium aged and 10% aged cheese in order to obtain optimum firmness and slicing qualities.
Use of higher proportion of young cheese results in lesser raw material cost, formation of a stable emulsion with high water binding properties, firm body and good slicing properties. Sometimes it may also result in a product having mild taste, excessive swelling, and a tendency to harden during storage. Similarly, a high content of mature cheese have the advantages of full flavor development and flow properties while the disadvantages may be the harsh (sharp) flavor, low emulsion stability and a soft consistency.
After selecting all the ingredients, the quantity of the ingredients is calculated on the basis of fat and dry matter content of the natural cheese components. Formulation of material balance of fat and dry matter including all the ingredients, water, and moisture loss during heating is made in a way to yield the finished product with desired composition.
27.3.2 Shredding and mixing
After calculating the quantities of all the ingredients, all types of cheese are shredded and either pre-mixed with other ingredients or mixed in the process cheese cooker before processing. Pre-mixing of cheese with other ingredients offers some advantages like physico-chemical changes at lower temperature prior to cooking which results in more uniform quality in the end product. Since cheese of different ages is used in manufacturing process cheese, there may be batch-to-batch variation in the hydration time of cheese and the free fat emulsification. Pre-mixing evens out the effects of differences in processability of cheese of varying age on the consistency of the final product.
27.3.3 Processing the blend
Following pre-mixing, the blend is discharged into the cooker, where it is processed. When pre-mixing is not practiced, the ingredients are added directly to the cooker. The ingredients are added in the order of ground cheese, a dry blend of emulsifier and other dry optional ingredients, water and flavors. Emulsifying salt may also be added with a portion of water at the start of cooking process. The remaining water may be added later in the processing stage. This is practiced especially where cooking time is relatively short. Flavors may be added later in the process to minimize the loss of volatile flavor compounds.
Processing refers to the heat treatment of blend by direct or indirect steam with constant agitation. The main functions of processing are killing of pathogenic and spoilage microorganisms to extend the shelf life of the product and to induce physico-chemical and microstructural changes which transform the blend to an end product with the desired characteristics and physico-chemical stability. Processing may be carried out in batch or continuous cookers. The time-temperature combination of processing varies depending on the formulation, the extent of agitation, and the desired characteristics in the finished product.
Batch Processing --- 70-95°C for 4-15 min
Continuous Method—140°C for 5-20 sec.
Continuous Method—140°C for 5-20 sec.
In continuous method, after giving the required heat treatment, it is essential to hold the product at around 70-90°C for 4-15 minutes for interaction of different ingredients and for desired physico-chemical changes to occur. Processing may also be performed continuously using extrusion cookers at a temperature of about 70-90°C. Extrusion cooking gives a high degree of protein hydration and rapid emulsification.
The processed hot mass may be homogenized in a two stage homogenizer at pressures of 15 and 5 MPa, respectively. It improves the stability of the fat emulsion, consistency, structure, appearance and flavor of the processed cheese.
27.3.5 Hot packing and cooling
Hot processed cheese blend can be transported to packaging machines directly from cooker or a buffer tank can also be installed in between. Processed cheese is usually packed and wrapped in lacquered foil, tubes, cups, cans and cardboard cartons. It may also be packed in the form of slices wherein, the hot molten cheese is pumped continuously into an endless 'tube' of plastic film, e.g. saran-coated polyester, which is automatically flattened and crimped into a chain of individual wrapped slices using crimping conveyors and rotating crimping heads. The chain of slices is then passed through a water-cooling tank and cooled to <10°C, dried by removing water using fans and/or scrapers, and finally cut into individual slices which are stacked and packed.
The body of the finished product may vary from firm and sliceable to semi-soft and spreadable, depending on the blend formulation, processing conditions and the cooling rate. The product that is cooled slowly develops a firmer body as compared to the product that is cooled faster. Thus, the process cheese should be cooled as slow as possible while in the case of process cheese spread fast cooling is required.
The finished product is stored at less than 10°C. It should not be stored under frozen conditions as low temperature may induce crystal formation.
Fig. 27.1 Flow diagram for manufacture of Processed cheese products
27.4 Cheese Powder
Cheese is dried to prolong the keeping quality and to reduce weight and bulk. Cheese powders are used as functional and natural flavor ingredients in a wide range of food/culinary applications including biscuits, savory, snacks, soups, bakery, sauces, dressings, ready meals and processed cheese. Majority of hard cheeses can be transformed into powder. Among cheeses which are produced in powder form, Parmesan and Cheddar are the most common. There are several methods of dehydrating cheese. These include direct tray drying, roller or spray drying, extrusion drying and freeze drying. Among these methods, spray drying is most commonly used. The technological process of dried cheese production is different from that of majority of other dry products. Cheese is first ground, and stirred with intensive agitation while adding water at 27-32°C to achieve the dry matter concentration optimal for spray drying (35-45%). At this stage, melting salts, comprising sodium citrate, disodium phosphates or polyphosphates are added to prevent milk fat separation. The well-mixed mass is pasteurized, heated to 60°C and homogenized. It is spray dried at about 175°C inlet air temperature and immediately cooled to 29-32°C, then shifted and packed in bags. Packaging in the atmosphere of inert gas and addition of antioxidants can extend the shelf life of dry cheese.
Kapoor, R. and Lloyd E. Metzger, L.E. (2008). Process Cheese: Scientific and Technological Aspects—A Review. Comprehensive Reviews in Food Science and Food Safety. 7, 194-214
Last modified: Tuesday, 16 October 2012, 10:34 AM