Leu-M

The serum creatinine concentration is widely interpreted as a measure of the glomerular filtration rate (GFR) and is used as an index of renal function in clinical practice. Glomerular filtration of creatinine, however, is only one of the variables that determines its concentration in serum. Alterations in renal handling and metabolism of creatinine and methodological interferences in its measurement may have a profound impact on the serum concentration of creatinine. We review the fundamental principles of physiology, metabolism, and analytical chemistry that are necessary to correctly interpret the serum creatinine concentration. These principles are then applied to important clinical circumstances, including aging, pregnancy, diabetes mellitus, drug administration, and acute and chronic renal failure. Despite numerous limitations, serum creatinine remains a useful clinical tool, but more accurate measures of renal function are frequently necessary.

Serum creatinine as an index of renal function: new insights into old concepts.

Flavour formation in meat and meat products: a review

A rapid aqueous acid extraction thiobarbituric acid method for measuring malondialdehyde as a marker of lipid peroxidation in animal tissue, food, and feedstuff samples has been developed. Sample is homogenized with aqueous trichloroacetic acid in the presence of hexane and butylated hydroxytoluene, and the homogenate is centrifuged. Following reaction with thiobarbituric acid reagent, malondialdehyde is directly quantified on the basis of the third-derivative absorption spectrum of the pink complex formed. Further purification is not required because the derivative transformation of the conventional analytical band at around 532 nm virtually eliminates spectral interferences arising from other compounds. The effect of antioxidants and the optimum conditions for the reaction have been established, and the analytical performance of the new method has been evaluated. The applicability of the method on various animal tissue, food, and feedstuff samples has been also tested. Owing to its simplicity and increased sensitivity and specificity, the method may be preferred over other methods for estimating the extent of lipid peroxidation.

Rapid, sensitive, and specific thiobarbituric acid method for measuring lipid peroxidation in animal tissue, food, and feedstuff samples

http://ernaehrungsdenkwerkstatt.de/fileadmin/user_upload/EDWText/TextElemente/PHN-Texte/Erhebungsmethoden/Muscle_Mass_Creatinine_Indicator_Heymsfield_AJCN_47_478_1983.pdf

Measurement of muscle mass in humans: validity of the 24-hour urinary creatinine method.

SUMMARY
2-Thiobarbituric acid (TBA) values of raw pork were determined by distillation and extraction methods and those of raw beef were determined by the latter method during storage at 4° and –20°C. TBA values of these tissues were low compared to values usually reported for cooked tissue from these animals in similar environments. There were significant animal differences in TBA values of beef and pork; there were significant changes in TBA values of these tissues during storage at 4°C, but changes during storage at –20°C were insignificant. pH and TBA values were inversely related. Mathematical relationships between TBA values of pork and beef during storage at 4°C. between TBA values and pH and between results obtained by the two procedures for determining TBA values of pork during storage are discussed. The extraction method is an acceptable method for determining TBA values and is easier to use than the distillation method. The TBA test has limited use for meat samples that have been frozen.

A new extraction method for determining 2‐thiobarbituric acid values of pork and beef during storage

Ground beef was extracted by supercritical CO2 (SC-CO2) with pressure ranging from 103-310 bar at 30-50°C. Higher pressure was needed to increase yield of extracted lipid. The profile of cholesterol content for the fractionated lipid extracted at 172 bar or 310 bar was generally lower in the initial stage of extraction and increased with CO2 used. DSC thermograms indicated that, depending upon extraction conditions, the distribution of lipid components of fractionated samples either shifted toward higher melting temperatures or concentrated those lipids melting between 5-25°C.

Supercritical CO2 Conditions Affecting Extraction of Lipid and Cholesterol from Ground Beef

SUMMARY

Paper and ion-exchange chromatography were used to determine qualitatively certain constituents in lyophilized diffusates from cold-water extracts of beef, lamb, and pork muscles. The qualitative contents of low-molecular-weight diffusible organic constituents in tissue from these three species were remarkably similar. Involvement of constituents studied as flavor and odor precursors is discussed.

Water‐Soluble Flavor and Odor Precursors of Meat. I. Qualitative Study of Certain Amino Acids, Carbohydrates, Non‐Amino Acid Nitrogen Compounds, and Phosphoric Acid Esters of Beef, Pork, and Lamba

SUMMARY

Quantitative analyses were made of water-extractable amino nitrogen and carbohydrate constituents of beef, lamb, and pork before and after heating. In all three species, taurine, anserine-carnosine, and alanine were present in relatively large quantities, and losses of these were large during heating. Other important amino acids degraded during heating were: glutamic acid, glycine, lysine, serine, cystine, methionine, leucine, isoleucine, and methyl histidine. Heating caused marked increases of phosphoethanolamine in samples from the three animal species studied. Ribose was the carbohydrate most labile to heating, and glucose was the most stable. The importance of these constituents as odor and/or flavor precursors of meat is discussed.

Water-Soluble Flavor and Odor Precursors of Meat. II. Effects of Heating on Amino Nitrogen Constituents and Carbohydrates in Lyophilized Diffusates from Aqueous Extracts of Beef, Pork, and Lamba

SUMMARY: Studies of the perchloric acid-extractable nitrogen, amino nitrogen, nonamino nitrogen, total carbohydrates, inorganic phosphate, free creatinine, creatine and total creatine plus creatinine of raw and heated beef, lamb and pork were made. Specific changes that occurred in the various constituents during heating are discussed. An extensive study of the influence of heating on certain chemical constituents of 80 beef samples of eight different cuts was also performed. Changes in chemical constituents during cooking of the various beef cuts were greatest in Choice clod and Good calf clod roasts, followed by round roasts and smallest changes occurred in rib steaks. Cooking caused significant increases in creatinine and decreases in amino and non-amino nitrogen, creatine and total carbohydrates. Creatine-creatinine was a better index of sensory quality than other chemical constituents studied.

Water‐Soluble Flavor and Odor Precursors of Meat. 5. Influence of Heating on Acid‐Extractable Non‐Nucleotide Chemical Constituents of Beef, Lamb and Pork

Milton E. Bailey

Papers

A new extraction method for determining 2‐thiobarbituric acid values of pork and beef during storage

Supercritical CO2 Conditions Affecting Extraction of Lipid and Cholesterol from Ground Beef

Water‐Soluble Flavor and Odor Precursors of Meat. I. Qualitative Study of Certain Amino Acids, Carbohydrates, Non‐Amino Acid Nitrogen Compounds, and Phosphoric Acid Esters of Beef, Pork, and Lamba

Water-Soluble Flavor and Odor Precursors of Meat. II. Effects of Heating on Amino Nitrogen Constituents and Carbohydrates in Lyophilized Diffusates from Aqueous Extracts of Beef, Pork, and Lamba

Water‐Soluble Flavor and Odor Precursors of Meat. 5. Influence of Heating on Acid‐Extractable Non‐Nucleotide Chemical Constituents of Beef, Lamb and Pork