Fruit free amino acid

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. 

The amount of protein in citrus fruit is relatively low (Table II), and the juice and peel have about the same amount (29). Much of the value that is considered as protein is either free amino acids or non-protein constituents which contain nitrogen. 

The protein in citrus is generally associated with the solid portions of the fruit, i.e., the seeds, flavedo, albedo, chroma-tophores, and pulp. Some of these components find their way into the juice along with the available free amino acids during extraction and processing and storage. Studies conducted in our laboratories (42,43,44) and by others (45) have shown that reductions in the pulp content of juice slow the rate of browning. 

There are, unfortunately, no studies to date of the dissolved protein content of microlayer samples. With the recent development of many sensitive techniques for the analysis of amino-acid mixtures in seawater using liquid chromatography and fluorescence detectors (e.g., Dawson and Pritchard, 1978), it should be relatively simple to analyse for combined amino acids after hydrolysis of the microlayer samples. Analyses of free amino acids in the microlayer seem not to have been performed to date either, but since considerable degradation of surface-adsorbed proteins may take place as a result of UV irradiation, this may be a fruitful area for future research. 

Table IV lists the proline, arginine, aspartic acid, glutamic acid, aminobutyric acid, alanine and total amino acid contents of several fruits as reported in selected literature references. A particularly salient reference is that of Fernandez-Flores et al (27) who reported quantities of 15 free amino acids for 22 different fruits. They suggested that the qualitative and quantitative distribution of free amino acids could be characteristic of the individual fruits. There were only smeill variations in the patterns for six different orange samples and seven strawberry samples. They concluded that the qualitative and quantitative distribution of amino acids could be a useful index for determining the authenticity of fruit products. Also, total amino acid content itself can be effectively used since apple and cranberry are very low in total amino acids while grape, blackberry, plum, and peach are relatively high.

C5H,N02. Mr 115.13, mp. ca. 196°C, [a]l -33.7° (H2O). Non-proteinogenic amino acid in the fruit bodies of Amanita pseudoporphyria and A. abrupta. Synthetic A. is long known as an antimetabolite against Escherichia coli and Saccharomyces cerevisiae and as an inhibitor of glutamate decarboxylase (EC 4.1.1.15). Ninhydrin reaction brown. A. inhibits protein synthesis. The 4-chloro derivative of A. [2-amino-4-chloro-4-pentenoic acid, (2S)-form CsHgClNOj, Mr 149.58] is a major constituent of the free amino acids in fruit bodies of Amanita pseudoporphyria. It has antibacterial activity. 

Some microorganisms associated with fruit and vegetable fermentations may cause the enzymatic formation of BA from free amino acids by the activity of substrate-specific amino acid decarboxylases. BA are small biologically active organic bases and are both physiologically/chemically and pharmacologically of great interest. They interfere in... 

Theanine is present in all parts of the plants except the fruits as the dominant free amino acid (305) although there is more glutamine than theanine in the sap of young tea plants (304). The largest amounts of theanine are found in the roots (325, 335). 

From a biochemical perspective, with the exception of a lower level of starch in the aborting ovaries, no substantial differences between the setting and aborting ovaries were found for protein, soluble carbohydrate, RNA, or DNA, while only minor differences in the pools of free amino acids were noted [8, 12]. Abscisic acid levels in seeds and pod walls of setting and aborting pods also did not vary significantly on a tissue weight basis [17]. Contrary to that, however, ABA levels were found to be lower in bean fruits induced to set by removal of fruits lower on the raceme relative to similar fruits on intact racemes [19]. 

Aqueous extracts of animal or plant organs, fruit juices, homogenates and body fluids generally contain peptides, proteins, carbohydrates, urea, salts and lipoids in addition to free amino acids in water-soluble or emulsified form. 

Lovkova (1964) administered uniformly labeled nicotine to N. tabacum and after 4 days recovered only 3.5% of the administered radioactivity in nicotine. About the same percentage of total radioactivity was recovered in the free amino acid fraction, which seems to have been convincingly purified from any contamination by nicotine. No separation of this amino acid mixture was undertaken, and no data were presented on the fate of the remaining majority (about 90%) of the administered radioactivity. Ill in, from the same laboratory (Ill in, 1965, 1966), reviewed his concept that the appearance of nicotine, especially in germinating seeds, and its disappearance during the maturation process have some relation to the metabolism of proteins and their constituents and that nicotine is not just a metabolic waste product. To support these hypotheses, he administered uniformly labeled [ C] nicotine to maturing fruits of Nicotiana plants. After 14 days, a radioactive protein fraction was isolated, but, because of the minute amount of nicotine in seeds and a high protein concentration, the total specific radioactivity of the isolated protein remained very low. Such incorporation of radioactivity into proteins was prevented by chloramphenicol. In later papers, more detailed experiments were described... 

Prasad U S, Jha O P, Mishra A 1979 Qualitative changes in sugars, free organic acids, free amino acids in leaves and fruit parts of Litchia chinensis. J Indian Bot Soc 58 114-119... 

Fruits contain 0.1-1.5% N-compounds, of which 35-75% is protein. Free amino acids are also widely distributed. Other nitrogen compounds are only minor constituents. The special value of nuts, with their high protein content, has already been outlined. 

Table 18.5. Free amino acids in fruits (as % of total free amino acids)...

Traditionally considered of benefit to the complexion and to prolong life mei rang yan nian), lycium fruit has been consumed for 2000 years in China for these purposes in recent years it is also used successfully in the topical treatment of bums, ulcers, bedsores, frostbite, canker sores, and fumncles. Its high contents of free amino acids, P-carotene, and bioactive polysaccharides as well recent evidence of its ability to increase skin hydroxyproline levels and at the same time with no known human toxicity make it a potentially useful cosmetic ingredient. 

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