Free amino acid contents

Gilbert, J., Shepherd, M. J., Wallwork, M. A., and Harris, R. G. (1981). Determination of the geographical origin of honeys by multivariate analysis of gas chromatographic data on their free amino acid content. /. Apicult. Res. 20,125-135. 

Naulet et al. [223] compared three chromatographic techniques lEC on an automatic amino acid analyzer, HPLC (with phenylisothiocyanate derivatization) and GC for the determination of the free amino acid content in 64 orange juices from different countries. The consistency of the different methods was estimated by considering the mean standard deviation for the set of amino acids observed. The best consistency was observed between lEC and HPLC. 

Storage conditions and preservation treatments also can affect the free amino acid content. Some authors [242] reported changes in the concentration of free amino acids of broccoli florets stored in air or in controlled atmospheres. Arginine concentration varied greatly during air storage, while y-amino butyric acid, alanine and an unidentified amino acid accumulated in response to low O2 and/or high CO2 treatment. 

Brierley, E. R., Bonner, P. L. R., Cobb, A. H. (1996). Factors influencing the free amino acid content of potato Solanum tuberosum L) tubers during prolonged storage. Journal of the Science of Food and Agriculture, 70, 515-525. 

Due to interference, samples that are high in salt (especially sodium chloride) or samples with a high free amino acid content may be difficult to analyze using this method. In those cases, validated gas chromatography (GC) methods (Mason and Slover, 1971) are more applicable. In addition, samples containing sorbitol should be analyzed by GC or using a calcium-loaded anion-exchange column (see Alternate Protocol 2). 

It has long been commonplace to determine the concentration of free amino acids in the beverage industries (e.g., wine, beer, fruit juice). In recent years, it has become more common to analyze for free amino acid content in other food and nutritional products. This is due, in part, to the growing practice of supplementing nutritional products with added free amino acids. Since these free amino acids are often being added in response to specific/special nutritional requirements of a target population, it is very important to ensure the fortification levels in these products. 

Anon (1999c) Fruit and vegetable juices. Determination of free amino acids content liquid chromatographic method. BS EN 12742 1999. Available from the British Standards Institute (BSI) or one of the other EU standards bodies. 

Table II. pH, Ammonia N and Free Amino Acid Content of S. lucens, E. superba (7) and A japonicus ( 4)...

Free Amino Acid Content in Stratum Corneum. 99... 

The characteristics of hydration level and barrier function of SC in various types of dry skin were reviewed and summarized in Table 9.3. They are senile xerosis, seasonal allergic rhinitis, ichthyosis valgaris, and experimentally induced dry skin including atopic xerosis and dry skin by hemodialysis. The water content decreased in every type of dry skin and the free amino acids content also decreased corresponding to the decrease of the water content. However, the TEWL or the ceramide levels showed no clear tendency throughout every type of dry skin, especially ceramides showed higher or lower value even though the water content in SC was consistently lower in every type of dry skin. 

During the past decade, several reports have demonstrated the decline of sphingolipid metabolism in atopic dermatitis24,25 and the cause of dry skin has been shown to be the abnormality of sphingolipid metabolism.26 However, in experimentally induced dry skin, the total amount of SC ceramide did not change13,26 but the amino acid content decreased.13 Recently, Tanaka etal. reported27 that amino acid content was reduced in the SC in atopic respiratory disease. They suggested that the free amino acid content is the crucial factor of the dry, scaly features of not only experimentally induced... 

Katagiri, C., Sato, J., Nomura, J., and Denda, M. (2003) Changes in environmental humidity affect the water-holding property of the stratum corneum and its free amino acid content, and the expression of filaggrin in the epidermis of hairless mice. J. Dermatol. Sci. 31 29-35. 

The free amino acid content in natto was very small and corresponded to only about 10 % of the total nitrogen compounds. Most of the other nitrogen compounds were peptides. These peptides have been shown to contribute to the bitterness of the characteristic taste of natto ( ). One of these peptides was Isolated and its amino acid sequence was investigated. The amino acid composition of this peptide was Asp 1, Thr 1, Glu 1, Ala 1, Pro 2, Val 3, He 3 and Leu 5. The amino acid at N-terminus of this peptide was Leu and the G-termlnal structure was -Ala-Val-Ile-Leu. 

Thorsen, A. and H.J. Fyhn. Final oocyte maturation in vivo and in vitro in marine fishes with pelagic eggs yolk protein hydrolysis and free amino acid content. J. Fish. Biol. 48 1195-1209, 1996. 

Alcazar, A., Ballesteros, O., Jurado, J. M., Pahlos, F., Martin, M. J., Vilches, J. L., and Navalon, A. 2007. Differentiation of green, white, black, oolong, and pu-erh teas according to their free amino acids content. J. Agric. Food Chem. 55 5960-65. 

High-pressure-induced biochemical aspects such as glycolysis, lipolysis, and proteolysis during ripening of cheese have been studied by a number of researchers. Yokohama et al. (1992) showed that high-pressure treatment resulted in considerable reduction in the ripening time due to proteolysis of milk protein, which resulted in an increase in free amino acids content and improvement in taste. The increased free amino acids content, from 21.3 to 26.5 mg/g, in cheese treated at 50 MPa for 3 days was comparable to 6-month old control cheese. 

A wide range in the free amino acid contents of helminths has been reported (1). Concentrations are usually higher than those of vertebrates but lower than in many other invertebrates. In contrast to vertebrates, helminths have one or two dominant free non-essential amino acids, usually alanine, proline, glutamate, serine and/or glycine. Non-protein amino acids detected include 3-alanine, 2-aminoisobutyrate,... 

In aquatic plants adverse effects of mercury such as senescence, growth inhibition, decreased chlorophyll, protein and RNA content, inhibited catalase and protease activities, inhibited and abnormal mitotic activity, increased free amino acid content, discoloration of floating leaves, leaf and root necrosis, and death have been reported (Muramoto and Oki 1984, Mhatre and Cha-phekar 1985, Sarkar and Jana 1986). The level of mercury that results in toxic effects in aquatic plants varies greatly. Freshwater concentrations of between 50 and 3400 pg Hg " " or 0.8 to 6 pg methyl-mercury are toxic to plants, and for salt water 10 pg Hg " " for algae and 160 pg Hg " for seaweed are reported. No data are available on methylmercury in saltwater plants (EPA 1997). 

DeMasi, T. W., Wardlaw, F. B., Dick, R. L., and Acton, J. C. (1990). Nonprotein nitrogen and free amino acid contents of dry, fermented and nonfermented sausages. Meat Sci. 27,1. 

Type of amino acid Free amino acid content (mg 100 g ) Total amino acid content (mg g" )... 

The free amino acid content of crushed almond can be determined by extraction with 150 ml of a methanol-chloroform-water (69 25 15) mixture (Young 1974). After the solvent is removed, samples are dissolved with a pH 2.2 buffer and analyzed with an automatic analyzer under the same conditions as described above. 

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