Foods, organic acids

Because they play a pivotal role in maintaining the quality and nutritional value of a variety of foods, organic acids are among the most frequently assayed substances in this type of substrate. 

Lactic acid [50-21-5] (2-hydroxypropanoic acid), CH CHOHCOOH, is the most widely occurring hydroxycarboxylic acid and thus is the principal topic of this article. It was first discovered ia 1780 by the Swedish chemist Scheele. Lactic acid is a naturally occurring organic acid that can be produced by fermentation or chemical synthesis. It is present ia many foods both naturally or as a product of in situ microbial fermentation, as ia sauerkraut, yogurt, buttermilk, sourdough breads, and many other fermented foods. Lactic acid is also a principal metaboHc iatermediate ia most living organisms, from anaerobic prokaryotes to humans. 

Phosphoric Acid. This acid is the primary acidulant in cola beverages. Phosphoric acid is stronger than most organic acids and weaker than other mineral acids. The dibasic properties of phosphoric acid provide minor buffering capacity in the beverage. Food-grade phosphoric acid is commercially available in concentrations of 75%, 80%, and 85% and is one of the most economical acidulants. 

Citric acid 77-92-9] (2-hydroxy-l,2,3-propanetricarboxylic acid), is a natural component and common metabolite of plants and animals. It is tbe most versatile and widely used organic acid in foods, beverages, and pbarmaceuticals. 

Steel coated with tin (tinplate) is used to make food containers. Tin is more noble than steel therefore, well-aerated solutions will galvanically accelerate attack of the steel at exposed areas. The comparative absence of air within food containers aids in preserving the tin as well as the food. Also the reversible potential which the tin-iron couple undergoes in organic acids serves to protect exposed steel in food containers. 

The concentration of acid impurities is an important indication of the quality of petroleum products and the purity of organic solvents, plasticizers, mineral oils, food fats, and polymers. Methods are used to detect organic acids in such compounds have many disadvantages the alkalimetry - low sensitivity, especially in the determination of weak acids, the extraction-photometric method is laborious, instmmental methods are expensive. In addition, most of methods are commonly unsuitable for direct analysis. 

Table A lists some of the organic acids found in foods. All of these compounds contain the carboxyl group...

In addition to phenolic substances, there are other components present in foods which have no antioxidant activity of their own, but which increase that of phenolic antioxidants. They are called synergists, and they should be accounted for in any discussion of antioxidant activity. Polyvalent organic acids, amino acids, phospholipids (lecithin) and various chelating agents belong to this group. Proteins may modify the efficiency of antioxidants as they react with the reaction products of both antioxidants and synergists. 

Pasch, J.H. and Von Elbe, J.H., Betanine stability in bnffered solntions containing organic acids, metal cations, antioxidants, or sequestrants, J. Food Sci., 44, 72, 81, 1979. 

CE is widely used for separation and quantification of organic acids (Stover, 1997). Many CE studies were performed to quantify organic acids in some food matrices (Erazier, 2001 Galli et al., 2003 Klampfl et al., 2000 Lindeberg, 1996). Many small organic acids can be well separated with CE (Boden et al., 2000 Mato et al., 2006a,b Navarrete et al., 2005). Those acids include acetic, citric, fumaric, lactic, maleic, malic, oxalic, pyruvic, succinic, and gluconic acids which can be separated by CE in a short time. 

Klampfl, C. W., Buchberger, W., and Haddad, P. R. (2000). Determination of organic acids in food samples by capillary zone electrophoresis. J. Chromatogr. A 881, 357-364. 

Mato, 1., Huidobro, J. F., Simal-Lozano, J., and Sancho, M. T. (2003). Significance of non aromatic organic acids in honey. /. Food Prot. 66, 2371-2376. 

Piper, P., Calderon, C.O., Hatzixanthis, K. and Mollapour, M. (2001) Weak acid adaptation the stress response that confers yeasts with resistance to organic acid food preservatives . 

The most important methods commonly used in produce preservation are low temperature, aw reduction, low acidity, and preservatives (e.g. organic acids and sulfite). The microbial stability and the sensory quality of most foods are based on passing over a combination of hurdles. 

Effervescence these systems that consist for instance of a carbonate or bicarbonate salt and an organic acid like e.g. citric acid, develop carbon dioxide gas on contact with water and are well known in pharmaceutical/health food tablets. A few market products exist that make use of this system but for reasons explained above this system is not that suitable for detergent tablets with a high content of surfactants. 

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