Meat products sample preparation

SFE of fruits and vegetables and meat products has been reported, but the sample preparation techniques necessary to obtain reproducible results are extremely time consuming. Solid absorbents such as Hydromatrix, Extrelut " anhydrous magnesium sulfate or absorbent polymers are required to control the level of water in the sample for the extraction of the nonpolar pesticides. Without the addition of Hydromatrix, nonpolar pesticides cannot penetrate the water barrier between the sample particles and the supercritical CO2. The sample is normally frozen and the addition of dry-ice may be required to reduce losses due to degradation and/or evaporation. Thorough reviews of the advantages and limitations of SFE in pesticide residues... 

BASIC PROTOCOL I PREPARATION OF FATTY ACID METHYL ESTERS FROM LIPID SAMPLES CATALYZED WITH BORON TRIFLUORIDE IN METHANOL In this method, lipid samples are first saponified with an excess of NaOH in methanol. Liberated fatty acids are then methylated in the presence of BF3 in methanol. The resulting fatty acid methyl esters (FAMEs) are extracted with an organic solvent (isooctane or hexane), and then sealed in GC sample vials for analysis. Because of the acidic condition and high temperature (100°C) used in the process, isomerization will occur to those fatty acids containing conjugated dienes, such as in dairy and ruminant meat products, that contain conjugated linoleic acids (CLA). If CLA isomers are of interest in the analysis, Basic Protocol 2 or the Alternate Protocol should be used instead. Based on experience, this method underestimates the amount of the naturally occurring cis-9, trans-11 CLA isomer by -10%. The formulas for the chemical reactions involved in this protocol are outlined in Equation D1.2.1 Saponification RCOO-R + NaOH, RCOO-Na + R -OH v 100°C DC Esterification RCOO-Na + CH,OH r 3 v RCOO-CH, + NaOH ioo°c ... 

Select a 25 g sample of ground meat from an appropriate location of the meat product. Additionally, select a proper control sample to prepare in parallel. 

Meat discoloration studies typically involve a maximum of 5 days, with discoloration analy-sis being performed every day or on alternate days. The actual experimental time involved in the objective assessment of discoloration is not extensive and depends on the number of samples being analyzed. Colorimetric measurements with hand-held colorimeters are very rapid (three measurements per meat surface in < 1 min). Spectral scans of meat surfaces require 1 to 2 min. Extraction and analysis of ground meat products has the added step of homogenization and filtration prior to spectrophotometry, but relative to many laboratory procedures, this is relatively quick. Isolation and purification of preparative amounts of myoglobin requires only 2 to 3 days once appropriate preparations are made. Finally, metmyoglobin can be reduced to oxymyoglobin in 15 to 20 min. 

The content of contaminants in foods is an altogether more demanding problem since contaminants are often present in trace quantities. Accordingly, it is necessary to resort to the sample preparation and trace enrichment techniques commonly used in environmental analysis. The types of problems that might be encountered include drug residues in meat products, furosine (known for its deteriorative and browning reaction) in... 

Formation, factors affecting concentrations, legal limits and occurrence of polycyclic aromatic hydrocarbons in smoked meat products and smoke flavor additives are briefly reviewed by Simko. The most widely employed techniques such as thin-layer chromatography (TLC), gas chromatography (GC), and high-performance liquid chromatography (HPLC) are evaluated. Moreover, sample preparation, pre-separation procedures, separation and detection systems being used for the determination have been evaluated with emphasis on the latest developments in applied food analysis and... 

Meat and other edible tissues of animals are difficult samples to analyze because of the nonuniformity and inherent instability of the sample. Because of the high water content ( 70%) of raw meat, meat samples are particularly prone to change either in storage or during preparation for analysis. This is more of a problem for raw meat than for meat products, which are often stabilized by some of the constituents added to the meat or by the processing procedmes (cooking, curing) used. 

See alsa Food and Nutritional Analysis Overview Sample Preparation Meat and Meat Products Oils and Fats Packaging Materials. 

The determination of nitrite and nitrate in meat and sausage products is an important problem, because their tolerated concentrations are strictly limited. Sample preparation includes homogenization of the sample, its extraction with a 5% borax buffer in a hot water bath, and subsequent Carrez precipitation with 15% potassium hexacyanoferrate(II) and 30% zinc sulfate solution. 

Highlights The broad assortment of samples presented in this section indicates the variability encountered by environmental samples. Uranium content in aerosols is usually associated with health physics considerations in facilities where uranium is mined, milled, and processed or in neighboring communities that may be affected by these activities. In general, exposure from airborne uranium containing particulates is very rare so the environmental interest is rather limited. Bioaccumulation by bacteria is still something of anecdotal interest, although it may be applied to bioremediation. Uranium that may enter the food chain is of concern, and several studies have focused on its content in vegetation and meat products. The analytical methods for all these samples are not unique and even the sample preparation techniques are similar to those described in detail in the previous sections. 

In this way, correlations with around 50 reference samples, very similar to those to be measured, is not unusual. Many products (proteins, oils in cereals, meat), can routinely be analysed by this method and often without preparation beforehand. In general, a relation is sought between certain absorptions and the presence of constituents in the mixtures to be analysed. This is the domain of correlation analysis. 

The effects of variation in meat oonposition on mutagenicity of cooked product were examined in reconstituted beef patties. Patties of variable water and fat content were prepared fron freeze-dried meat. Appropriate amounts of distilled water were added back to the meat for the variable-water-content experiment. Defatted meat was prepared by petroleum ether extraction of freeze-dried material in a Soxhlet apparatus. Petroleum ether was removed m vacuo and the remaining oil was used to reconstitute the meat sanples/ vhich were also reconstituted to their original water content. Reconstituted meat samples had the coitpositions indicated in Figures 4 and 5. 

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