Milk analysis

The application of FTIR spectroscopy to the analysis of milk has been investigated, and its performance compared to that of conventional filter-based instrumentation [22]. Calibration of the FTIR spectrometer for the determination of fat, protein, lactose, and total solids was performed through the use of PLS. The FTIR method using modified Nicolet 510 research spectrometer was able to provide a four-component analysis of milk in 12 seconds per sample and met the AOAC specifications for milk analysis [22]. The results of this study demonstrated that the use of FTIR spectroscopy would allow payment laboratories to analyse for more components and with appropriate sample handling gain sample throughput speed. A commercial version of an FTIR milk analyser is presently on the market in Europe. An FTIR method for the direct determination of water in milk has also been reported [23]. 

The casein content of milk is an important indicator of cheese yield, and cheese yield formulas are used to determine milk payment in some cheese plants. Milks of similar protein content but dissimilar casein/whey ratio do not produce the same cheese yield. The methods presently used for casein estimation are based on precipitation of casein from the milk and involve a series of steps including centrifugation, aspiration of fat, filtration, drying and weighing. Two methods for the determination of the casein content of milk with the use of a commercial IR milk analyser have been described [24, 

Notes a) v (CO) ester linkage b) protein amide II band c) C-OH d) mean 

based on IR measurement of the protein content before and after removal of the casein from the milk by isoelectric precipitation [24] or by renneting 

08% of the actual values. The FTIR method was vahdated with 36 milk samples spiked with known amounts of sodium caseinate and whey protein concentrate. The predictions of the spiked amounts in these samples were within 0.09% for casein and within 0.12% for whey. 

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Purge-and-trap methods have also been used to analyze biological fluids for the presence of trichloroethylene. Breast milk and blood were analyzed for trichloroethylene by purging onto a Tenax gas chromatograph to concentrate the volatiles, followed by thermal desorption and analysis by GC/MS (Antoine et al. 1986 Pellizzari et al. 1982). However, the breast milk analysis was only qualitative, and recoveries appeared to be low for those chemicals analyzed (Pellizzari et al. 1982). Precision (Antoine et al. 1986) and sensitivity (Pellizzari et al. 1982) were comparable to headspace analysis. 

Mes J. 1981. Experiences in human milk analysis for halogenated hydrocarbon residues. Inter J Environ Anal Chem 9 283-299. 

An indirect enzyme immunoassay suitable for the determination of chloramphenicol and its glucuronide was developed for the analysis of urine, milk, tissue, and eggs as well (48). In this assay, chloramphenicol succinate was coupled to both bovine serum albumin and horseradish peroxidase by a mixed anhydride procedure. Unlike tissue and egg samples, urine and defatted milk could be directly analyzed, but when an ethyl acetate extraction was employed in milk analysis, the limit of detection was lowered at least 10 times. 

A different approach was followed by Blanchflower et al. (23) in a liquid chromatographic-mass spectrometric method for the determination of chloramphenicol residues in milk and animal tissues, using deuterated chloramphenicol as internal standard. For milk analysis, the sample is diluted with 1 volume of water and purified by loading the diluted milk onto a Cis Sep-Pak extraction column. Following column washing with water, chloramphenicol is eluted with methanol. The eluate is evaporated to dryness, and the residue is dissolved in water/acetonitrile (7 3). 

When liquid samples such as serum, plasma, milk, or honey are not to be extracted using direct liquid-liquid partitions with organic solvents but through use of solid-phase extraction or matrix solid-phase dispersion techniques, dilution with water (323, 324), phosphate buffer saline (325), or phosphoric acid (326, 327) is often the only sample preparation procedure applied. Milk analysis sometimes requires further pretreatment for fat removal (328). Centrifugation at about 7000g at 4-10 C for 20 min is the usually applied procedure for making the fat floating on top of milk readily eliminated. 

Very few methods have appeared in the literature with respect to the extraction, cleanup, and subsequent determination of corticosteroids in food samples (Table 29.17). Milk analysis usually requires a pretreatment step for fat elimination (527). Centrifugation for 20 min at about 7000 g at 4 C is the usually applied procedure for making the fat floating on the top of the sample. Tissue analysis also requires a pretreatment step for matrix break-up that can be accomplished by means of a mincing and/or a homogenizing apparatus. 

Preparation of electrochemical screen-printed immunosensors for progesterone and their application in milk analysis... 

Adrian, J., H. Font, F. Sanchez-Baeza, et al. 2008. Preparation of polyclonal antibodies for the generic determination of sulfonamide antibiotics and development of an enzyme-linked immunosorbent assay (ELISA) for milk analysis. J. Agric. Food Chem. 51 385-394. 

Schlaud M, Seidler A, Salje A, et al. 1995. Organochlorine residues in human breast milk analysis through a sentinel practice network. Journal of Epidemiology Community Health 49(suppl. 1) 17-21. 

These studies demonstrate that treatments that have been reported to modify the heat stability of milk also may change the distribution of tracer milk proteins between the physical phases of milk. Analysis of these interactions may provide useful information about the mechanisms of these effects. In unpublished experiments, we have extended this approach for studying homogenized milk-based systems, also containing a lipid phase, to investigate lipid-protein interactions. Dual-label experiments, for example in milk containing M-/3-L and 3H-methyl-/c-casein, could be applied to the isolation and characterization of protein complexes in milk. Labeled caseins could prove valuable as probes for elucidating micelle structure. 

Rodriguez-Otero, J.L., Hermida, M., Centeno, J. 1997. Analysis of dairy product by near infrared spectroscopy. J. Agric. Food Chem. 45, 2815-2819. van de Voort, F.R., Kermasha, S., Mills, B.L., Ng-Kwai-Hang, K.F. 1987. Factors affecting differences in milk test fat results obtained by the Babcock, Rose-Gottlieb and infrared milk analysis. J. Dairy Sci. 71, 290-298. 

Page Pedersen, USA Sound velocity Milk analysis No Yes... 

The shunt probe can be considered as a variation because the linear probe is contained inside another plastic tube (the shunt) where the fluid to be sampled passes, this arrangement allowing the continuous sampling from moving fluids. First described by Scott and Limte [31] it is usually appUed for bile sampling [32,33] but in vitro applications are also described such as that for milk analysis [34]. 

Wastewater from an industrial milk analysis laboratory Anaerobic filter + SBR 98% (COD), 99% (nitrogen) Industrial Laboratory scale Garrido et al. (2001)... 

The results are generally in good agreement with NIST certified values, indicating the validity of our procedure for whole milk analysis. 

Following the successful development in the mid-1960s of IR milk analysers, described above, attempts were made to extend their use to the analysis of meat [28-30] as well as fish [31]. Although the results of this work demonstrated the viability of IR analysis of these types of samples, the application of the methods developed was limited because the commercially available equipment was specifically designed for milk analysis applications. 

Soxhlet for fat and micro-Kjeldahl for protein). The preparation of freeze-dried meat mixtures to serve as calibration standards was also described in this work [32]. The availability of such pre-analysed, reconstitutable, shelf-stable calibration standards would facilitate the implementation of FTIR methods in the meat processing industry, in a similar manner as has been reported for milk analysis [33,34]. 

The following descriptions of the Breed Method and the Frost Method of counting bacteria are taken directly from the A. P. H. A. Standard Methods of Milk Analysis Fourth Edition, 1923. 

Newburg, D.S., and Nenbauer, S.H. 1995. Carbohydrate in milks analysis, quantities, and significance. In Handbook of Milk Composition, ed. R.G. Jensen, pp. 273-349. San Diego, CA Academic Press. 

Transmission instruments are used in milk analysis, and suitable provisional standards are available for fat, protein, and lactose determination in whole milk by use of a mid-infrared instrument. Near-infrared reflectance techniques are typically used for... 

Chromate has been used as a preservative for milk that is to be analyzed for quality-control purposes. Several reports document chromate allergy in milk testers and in milk analysis laboratories [129, 175, 176]. 

Huriez C, Martin P, Lefebvre M (1975) Sensitivity to dichromate in a milk analysis laboratory. Contact Dermatitis 1 247-248... 

Assessment of milk composition is a more difficult task than assessment of milk yield, since there are five main variables to consider. Modern analytical methods allow for routine milk analysis on a large scale, and values for fat, lactose and protein contents of herd bulk milks are now readily available. AVhen analytical results are not available, assumptions are often made concerning the quantitative relationships between constituents, which allow composition to be predicted from the content of a single, easily determined constituent, usually fat. 

Hall and De Thomas (24) described the development of spectroscopic models for the on-line analysis of fat in milk and cheese and moisture in butter and cheese. For fluid milk analysis, the process interface consisted of an interactance immersion probe inserted into a pipe. This probe was usefui for minimally scattering fluid streams as it reflected light that passes through the sample back to the fibers, providing a double pass through the sample. For butter analysis, the process interface consisted of two probes mounted at 180° to each other welded to the pipe at the end of the creamer. For process cheese analysis, transmission probes were positioned in a process pipe with sapphire windows. 

Biggs, D. A., Performance specifications for infrared milk analysis, 7. Assoc. Off. Anal. Chem., 62 1211 (1979). 

Sjaunja, L.-O., Studies on milk analysis of individual cow milk samples, thesis, Swedish University of... 

The original electrode was developed for detecting urea in blood and urine samples. An enzyme sensor for measuring urea in milk has been reported by an Indian group [31]. The working principle is identical to that of Guilbault s sensor. The sensor prepared for milk analysis, however, is a flat cell fabricated with screen-printed technology. 

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