Milk analysis storage

Speciation Analysis in Human Milk Sampling, Storage, Preparation,... 

SPECIATION ANALYSIS IN HUMAN MILK SAMPLING, STORAGE, PREPARATION, SEPARATION, AND DETECTION... 

The ADSA Committee on Milk Protein Nomenclature (Eigel et al. 1984) presented a tentative nomenclature for the new enzyme membrane proteins. While the primary structures of these proteins have not been established, sufficient information exists to obtain an operational definition. The total protein complement of the membrane as observed is dependent upon the past history of the membrane from its formation to its analysis. Both the temperature and the time of storage before analysis can alter the membrane composition and physical state (Wooding 1971). In addition, plasmin has been shown to be associated with preparations of the membrane, and proteolytic products of the membrane protein have been observed in milk (Hoffman et al. 1979 Kanno and Yamauchi 1979). Therefore, one should use fresh warm raw milk for the study of the native MFGM protein. 

Dill, C. W., Herlick, S. A., Richter, R. L., and Davis, J. W. 1979. Fat test depression during chilled storage of milk samples in plastic containers for analysis by the Milko-Tester J. Food Protection 42, 314-316. 

Once the material has been chosen for sampling and storage, it is important to establish a protocol for the collection of milk samples. The extraction will be achieved manually or by means of a plastic milk extractor, a new one for each sampling. The nipple and the skin around it should be cleaned with soap and distilled water before collection. The milk thus collected should then be stored in plastic containers previously decontaminated, as explained above. The containers should be labeled and kept at — 20°C until analysis. 

Milk samples should be refrigerated and delivered to the laboratory within 1-2 days. For longer storage, the milk sample should be frozen or a preservative added such as methiolate, formaldehyde, or thimerosal (DOE 1987, EPA 1984), as indicated in Table 5.1. Preservatives may interfere with radioiodine separation (Murthy and Campbell 1960), but can be added if radioiodine is measured directly by gamma-ray spectral analysis. 

A number of sensitivity studies have been performed in order to study the influence and effectiveness of preventive measures through the milk chain such as control of pasteurization conditions, analysis at cool storage and inspection at retail. In addition, this smdy will show the relevance of combining predictive and probabilistic modelling for food safety as it allows a more realistic exposure assessment. 

The first sensitivity study assumes there is no control of the pasteurization parameters, i.e. of the pasteurization temperature. Tables 6 and 7 show the results found in this case. One can observe now there is an increase of LM content through the milk chain with consequences Cj to C4 possible. Formnately, analysis of LM content at cool storage reduces the initial load of LM in milk reaching the market. 

Leaching is also the cause for riboflavin loss from tofu. Using HPLC analysis, a 20% loss of vitamin from tofu was found after 3 to 7 days of storage at 4°C (62). The quantitative assessment of flavins in cow milk and the effect of pasteurization on these compounds were studied by Roughead and McCormick (26) using the phenol extraction technique and reversed-phase HPLC (Table 4 Fig. 7). Riboflavin (61%), FAD (26%), and 10-(2 -hydroxyethyl)flavin (11%) were the predominant flavin compounds in all milk samples smdied. The distribution of flavins in raw and pasteurized milk reveals little difference, with the exception of a decrease in the FAD content with pasteurization. 

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