Slurries, cheese

Most varieties of cheese are cooked by applying heat to the outside of the vessel containing the curd and whey slurry. Gouda cheese curd is heated by first draining a portion of the whey and then adding hot water. The proportion of whey removed and water added is varied to control the amount of residual lactose in the curd. Washing of the curd is also used in cottage and brick cheese manufacture to remove lactic acid and lactose, but in these cases the cheese curds have first been heated. 

Harper, W. J., Carmona de Catril, A. and Chen, J. L. 1980. Esterases of lactic streptococci and their stability in cheese slurry system. Milchwissenschaft 35, 129-132. 

Protein-rich foods can also be specially treated. According to Saag (135), in order to extract colorants from fish, samples are boiled, filtered, washed, with an ammonia solution to displace proteins, and then washed through Sephadex LH-20 with water. The colored zones are collected for HPLC analysis. Dairy products (ice cream, cheese, yogurt) are first mixed with acetone or ethanol to precipitate the protein, which is ground up with sea sand and Celite, and the slurry is placed in a column from which dyes are eluted with a solution of ammoniacal methanol (135,162). 

The measurement of pH in cheese making is extremely important to control fermentation/acid production and hence the final quality. While there are no standard methods available for measuring cheese pH, there have been few methods reported in the literature. One method involves preparing a slurry of 10 g of grated cheese in water and measuring the pH potentiometrically (Fox et al., 2004a). However, this method may alter the balance between colloidal and soluble calcium phosphate and hence it is preferable to measure the pH of the cheese directly. The quinhydrone electrode method (Marshall, 1992) measures the pH directly. The potential (mV) created by a paste of cheese and quinhydrone in saturated KC1 is measured and used to determine the pH at a particular temperature. 

Today, cheese flavored paste and powders, containing from 5 to 100 times the flavor level of native cheese, are available in the marketplace for most cheese varieties. Nearly all of these products are made by using added enzymes with most of them using a blend of enzymes and microorganisms. Selected cheese flavors are produced in a liquid or slurry form in a relatively short time compared to making the true cheese and at a flavor level many fold above the maximum flavor obtainable in the true cheese. 

Sood, V.K. and Kosikowski, F.V., Ripening changes and flavor development in microbial enzyme treated cheddar cheese slurry, J. Food Set, AA, 1690, 1979. 

Romano Cheese and Butterfat. The volatile flavor compounds were isolated from the EMB sample, a commercial sample of Romano cheese and a butterfat control sample by vacuum steam distillation. Volatiles were isolated from 2.5L EMB in five batch isolations. The EMB was mixed in a Waring blender prior to each isolation. Romano cheese was obtained from a commercial source (Stella Romano cheese, Universal Foods Corp., Milwaukee, WI). Volatiles were isolated from 700 gm Romano cheese in five batch isolations. One hundred and forty grams of cheese were cut into pieces for each isolation and slurried with 360 ml 0.1% sodium phosphate buffer solution in a blender. Volatiles were also isolated from 500 ml of butterfat emulsion control sample (207. butterfat). 

The slurry samples of EMB, Romano cheese and butterfat were vacuum distilled at 50°C for 8 hours. The volatiles were condensed in a series of cold traps cooled with a dry ice-acetone slurry. The condensates collected in the traps were combined, saturated with sodium chloride and extracted with ethyl ether. 

Rabie A.M. (1989) Acceleration of blue cheese ripening by cheese slurry and extracellular enzymes of Penicillium roqueforti. Lait., 69, 305-314. 

D. Cheese Slurries Processed Cheese Products A. Introduction... 

Flavor has been reported to develop very rapidly (1 week) in slurries containing 40% solids. Such systems have been used to screen exogenous enzymes. Fast-ripening slurries could be useful in the preparation of cheese sauces, cheese flavoring, processed cheeses, etc. Enzyme-modified cheeses, which can be regarded as being based on the slurry principle, are used commercially as ingredients in processed cheese and cheese products. 

The titratable acidity and pH of other dairy products, such as cheese and during cheesemaking, are measured in the same way. For cheese, it is usual to make a slurry of lOg cheese in 10 ml distilled water and measure the acidity or pH. 

VFA analysis is important in the ripening control of cheeses, particularly of hard cheeses. HSGC offers a rapid route to check for the presence of unwanted Clostridia species. These bacteria ferment lactic acid and are capable of forming large amounts of gas and butyric acid, which spoils the cheese. An elegant way of sample preparation for final HSGC analysis was devised by Osl (1988). A cheese slurry is made it is then refrigerated in order to crystallize the fat, filtered to remove the solidified fat and diluted with ethanol. To this ethanolic solution concentrated sulphuric acid is added as well as valeric acid as an internal standard this solution is then thermo-statted for 1 h at 80°C, and the ethyl esters formed are sampled from the HS. 

A sample can be anything from a few grams of grain or a few milliliters of beer to a fistful of straw, a sheet of plywood, or a human arm. Liquids with viscosities ranging from thinner than water to thick slurries plastic solids such as plastics themselves or something of the consistency of cheese a piece of cloth, soil, wood, or wool an area of skin a liter of river water or a bagful of cow manure, all of them present individual precepts for either bringing the material into contact with the NIR instrument or, more recently, the NIR instrament to the sample. All of these materials... 

Ordinary butter (the toast type) is another example of a liquid/semisolid, depending on temperature. Butter is really a slurry of water in fat, differing from many materials of similar stiff room temperature textures in that its production is essentially a room temperature operation. Materials of this type can be sampled with a core-type sampler in the semisolid state or by methods previously described, in the liquid state. They can also be sampled by an extmsion system, whereby the sample is chopped off from an extruded stream. It is important that temperature be controlled so that the cut surface remains level and does not start to flow. Cheese is even more solid and can be sampled by simply taking a slice. Processed cheese is usually manufactured in the liquid state, and can be sampled and analyzed as-is, or fed into a sampling cell and allowed to solidify before analysis. Crumbly materials, such as biscuit (cookie) or cake doughs, dough mixes for pasta or noodle production or compressed (fresh) yeast, can be sampled manually or by an extrusion system. This includes thick slurries, which will eventually either solidify or be compressed into solid sheets or blocks. 

Shipe, W.F., G.F. Senyk, R.A. Ledford, D.K. Handler, E.T. Wolff, Elavor and chemical evaluations of fresh and aged market milk, J. Dairy Sci., 63(Suppl. 1), p. 43, 1980. Chandran, R.C., K.M. Shahani, Milk lipases a review, J. Dairy Sci., 47, p. 471, 1964. Kwak, H., I.J. Jeon, S.K. Pemg, Statistical patterns of lipase activities on the release of short-chain fatty acids in Cheddar cheese slurries, J. Food Sci., 54, p. 1559, 1989. Murry, T.K., B.E. Baker, Studies on protein hydrolysis I — preliminary observations on the taste of enzymic protein hydrolysates, J. Sci. Food Agric., 3, p. 470, 1952. Fujimaki, M., M. Yamashita, Y. Okazawa, S. Aral, Diffusible bitter peptides in peptic hydrolyzate of soybean protein, Agric. Biol. Chem., 32, p. 794, 1968. 

As one would expect, microbial enzymes range in specificity. For example, lipases from Candida cylindracea and Staph aureus have little specificity while those from Geotrichum candidum are specific for long chain acids [57], which are of little value in this application. Fortunately, most microbial hpases show specificity for the one and three positions of the triglyceride where the short chain fatty acids are found. While substantial information exists in the literature characterizing lipase enzyme activity to help in enzyme choice [58], enzymes must be evaluated for function in a model system. This often is done in a curd slurry system, which is produced by blending two parts of fresh cheese curd plus one part sterile dilute salt solution (5.2%... 

EMCs are generally manufactured from cheese pastes that are made from the cheese of the same type. Additional components such as butterfat or cream may be added to add extra precursors when appropriate. Noncheese ingredients such as MSG, yeast extract, diacetyl, or other flavorants may also be added, but they may have to be declared on the label of the final product. Consistency in this base material is critical to the production of a standardized EMC product. Off-flavors may develop during incubation of the paste/enzyme slurry since the conditions are optimal for microbial growth. Equipment must be sterilized and precautions taken to prohibit miCTobial contamination. Bacterial inhibitors such as nitrates, sorbate, or nicin may be used. Free fatty acids generated by lipase enzymes afford some inhibition. Incubation time and temperature influence enzyme action and must be carefully controlled. 

Kwak, H.S., 1.1. Joen, S.K. Pemg, Statistical patterns of lipase activities on the release of short chain fatty adds in Cheddar cheese slurries, J. Food ScL, 54, p. 1559, 1989. 

When that stress is exceeded, the shear rate grows. Further stress leads finally to linear (Newtonian) behaviour. Examples of plastic systems are chocolate, butter, cheese, various spreads and ice cream. In pseudoplastic systems the observed viscosity decreases with an increase in shear stress. An example of a pseudoplastic system is pudding. Dilatant systems resist deformation more than in proportion to the apphed force. The shear rate is growing much faster than that of Newtonian fluids and viscosity increases with an increase in shear stress. At low apphed forces, the system behaves as a Newtonian fluid. Examples of dilatants systems are honey with added dextran and a slurry of wet beach sand. Thixotropic systems become more fluid (they have lower viscosity) with increasing time of an apphed force. If the apphed force ceases to operate, the original viscosity of the system is restored due to a reversible transformation of the sol gel type. Examples of thixotropic systems are mayonnaise, ketchup, whipped and hardened fats, butter and processed cheeses. Rheopectic systems exhibit behaviour opposite to that of thixotropic systems. Their viscosity increases with increasing time of apphed force. An example is whipped egg white. 

The history of the bacterial propionic acid fermentation began from the investigations by Adolph Strecker (1854) in which he observed for the first time the formation of propionic acid from sugar. He showed that a calcium carbonate-sugar mixture, to which cheese and sour milk were added, first formed a thick, calcium-lactate slurry. Later, a second fermentation occurred in the mixture that converted the lactic acid to mostly propionic acid, some acetic acid, and a gas (later identified as carbon dioxide [CO2]). 

---