Cheese standard methods

Analysis of cheese composition, including moisture, protein, fat, ash, and salt, is usually conducted according to the methods published by ISO, IDF, or AO AC. Some of the standard methods available for cheese analysis are summarized in Table 5.1 and briefly discussed below. Additional information may be found elsewhere (Nielsen, 2003 Nollet, 2004). 

TABLE 5.1 Standard methods for compositional analysis of cheese... 

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. 

Semi-solid foods, such as soft butter and some cheeses, cannot be formed into samples capable of supporting their own weight. For such foods, compression testing takes the form of cone or die penetrometry, in which a cone, die, needle or sphere is made to penetrate the sample (held in a suitable container) either under constant load or at constant speed, and the penetration depth measured as a function of time. Standard methods for penetrometry of fats are published by the AOCS (AOCS Official Method Cc 16-60, Firestone, 1998) and the British Standards Institution (BS 684 Section 1.11 1976, BSI, 1976c). 

Cheese The standard methods described previously are used to determine the composition of cheese with minor modifications. The Werner-Schmid method is generally preferred for the determination of fat but the Gerber method is also used. In both cases, the cheese has to be mixed very thoroughly with the reagents. 

The emulsifying salts in processed cheese (sodium, potassium, calcium and ammonium phosphate, citrate, and tartrate) can be measured from the phosphate, citrate, and tartrate content, after removing the protein with phosphotungstic acid, using standard methods. 

One example of the use of the spin echo technique is to measure moisture and oil content simultaneously in many agriculture and food products such as oilseeds, nuts, chocolate, milk powder, cheese, cookies, and sausages. The total oil and moisture analysis using TD-NMR for seeds and seed residues have become international standard methods (ISO CD 10565 and ISO CD 10632). In seeds, oil and water molecules all have hydrogen and they all contribute to NMR signals. In dried seeds, the water molecules are bound, and the mobility of the water molecules is much more restricted than that of oil molecules, which remain free in the seeds. Therefore, the water in the... 

Both multi-residue methods are presented in several parts, which separate general considerations from procedures for extraction, cleanup and determination/ confirmation. Whereas in EN 12393 several extraction and cleanup steps cannot be combined arbitrarily, the modular concept is utilized to a greater extent in EN 1528. In the latter standard, there is no limitation to the combination of several extraction procedures, mostly designed for different commodities, e.g., milk, butter, cheese, meat or fish, with different cleanup steps. Both standards, EN 1528 and EN 12393, do not specify fixed GC conditions for the determination and confirmation. All types of GC instruments and columns, temperature programs and detectors can be used, if suitable. 

Johnson, M. E. 1984. Methods of standardizing milk for cheesemaking. Paper No. 1984-2. 21st Annual M arse hall Invitational Italian Cheese Seminar. Marschall Products, Madison, Wise. 

Normally, odd-numbered fatty acids are used as internal standards. While the use of internal standards ensures the correctness of the extraction procedure, it does not guarantee the completeness of extraction for different fatty acids. Due to this reason, a comparison between the methods is essential to truly determine the efficacy of extraction. Chavarri et al. (1997) compared two sample preparation procedures. The first method was the direct method developed by de Jong and Badings (1990), described above. The second method involved saponification with TMAH as described by Martin-Hemandez et al. (1988) and the formation of methyl esters in the injector prior to analysis. The authors found that separation of the FFAs from the triglycerides prior to derivatization improved the analysis. Another comparative study by Ardo and Polychroniadou (1999) reported that the saponification method described above (Martin-Hernandez et al., 1988) was found suitable for both low and high FFA levels in cheese. 

IDF (1986). Whey Cheese—Determination of Fat Content—Rdse-Gottlieb Gravimetric Method (Standard 59A). International Dairy Federation, Brussels. 

ISO (1984). Cheese and Processed Cheese Products—Determination of Total Phosphorus Content—Molecular Absorption Spectrometric Method (Standard ISO 2962). International Organization for Standardization, Geneva. 

The methods described above have been used principally to quantify FFAs in cheese, but can be used for other milk products with some slight modifications. All the above methods use internal standards (typically FFAs which are not present in milk fat), and the recovery of all FFAs is based on the recovery of these internal standards. It is best to use both volatile and non-volatile FFAs as internal standards. Currently, the International Standard for the extraction of lipids and lipo-soluble compounds from milk and milk products is ISO 14156 (ISO, 2001) and involves solvent extraction. Determination of the fatty acid composition of milk fat involves the preparation of fatty acid methyl esters (FAME) by transesterification (ISO, 2002a), followed by quantification by GC (ISO, 2002b). 

British Standards Institution, London, BS 769 1961, Methods for the Chemical Analysis of Butter, BS 770 1963, Methods for the Chemical Analysis of Cheese, BS 2472 1966, Methods for the Chemical Analysis of Ice Cream, BS 809 1974, Methods of Sampling Milk and Milk Products. 

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