Fruit organic acid

Fruit and vegetable juices packed with 21-26 in. of vacuum and stored in uncoated aluminum cans caused severe corrosion as shown in Table III. The corrosion rate brought about by the juices depends more on the nature of the organic acid present and the buffering capacity of the juice than on the total titratable acidity (11). The use of coated aluminum containers considerably minimized corrosion problems. Product control under extended storage conditions may be achieved by using specific chemical additives. However, more work is needed in this area before final conclusions can be reached. 

Carboxylic acids with one acid group are known as monobasic acids while those with two acid groups are dibasic acids. All acids with more than one acid group are in the class of polybasic acids. The simplest organic acid, formic acid, is responsible for the irritation of bee and ant stings. Vinegar is a 5% solution of acetic acid in water. The acetic acid is responsible for the characteristic sour taste. Citric acid, found in citrus fruits and used in soft drinks, is a tribasic acid with three carboxylic acid groups. The dibasic acid, adipic acid, is a major component of nylon. 

Grapes are one of the few fruit crops that contain a significant amount of the weak organic acid known as tartaric acid, HOOC-(CHOH)2-COOH. More than half of the acid content of wine is ascribed to tartaric acid. As a weak acid, tartaric acid partially ionizes in water to yield the bitartrate or hydrogen tartrate ion ... 

Similar results were found in a replicated field trial involving four cultivars at Wadenswil, Switzerland (Weibel and Widmer, 2004) and in a similar study carried out in the USA (Reganold et al., 2001) with organic fruit repeatedly achieving higher taste panel scores for fruit firmness, acidity, sugar content and overall sensory score. 

Different organic acids, primarily lactic acid, have been successfully used for decontamination of whole livestock carcasses, and the application of different organic acids used for decontamination has also been tested in the fruit and vegetable industry. Organic acids other than lactic acid that are known to have bactericidal effects are acetic, benzoic, citric, malic, propanoic, sorbic, succinic and tartaric acids (Betts and Everis 2005). The antimicrobial action is due to a reduction in the pH in the bacterial environment, disruption of membrane transport, anion accumulation or a reduction in the internal pH in the cell (Busta et al., 2001). Many fruits contain naturally occurring organic acids. Nevertheless, some strains, for example E. coli 0157, are adapted to an acidic environment. Its survival, in combination with its low infective dose, makes it a health hazard for humans. 

Chen et al. (1997a) analysed sodium saccharin in soft drinks, orange juice and lemon tea after filtration by injection into an ion-exclusion column with detection at 202 nm. Recoveries of 98-104% were obtained. They reported that common organic acids like citric and malic and other sweeteners did not interfere. Qu et al. (1999) determined aspartame in fruit juices, after degassing and dilution in water, by IC-PAD. The decomposition products of aspartame, aspartic acid and phenylanaline were separated and other sweeteners did not interfere. The recoveries of added aspartame were 77-94%. Chen et al. (1997b) separated and determined four artificial sweeteners and citric acid. 

G. Shui and L.P. Leong, Separation and determination of organic acids and phenolic compounds in fruit juices and drinks by high-performance liquid chromatography. J. Chromatogr.A 977 (2002) 89-96. 

You find them in citrus fruits (citric acid), vinegar (acetic acid), aspirin (acetylsalicylic acid), and numerous other natural and synthetic compounds, as well on numerous organic exams. In this chapter you explore the structure, synthesis, and reactions of these acids and acids like them. 

Elderberry (Sambucus nigra) is cultivated on small scale in Europe. The fruits have a high concentration of red and purple anthocyanins and a relatively low concentration of sugars, organic acids and aroma compounds, which make this juice attractive as a natural colour ingredient in other red fruit products [126-129]. The fresh green odour of elderberry juice is associated with volatile compounds with typical green notes such as 1-hexanol, 1-octanol, (Z)-3-hexen-l-ol, ( )-2-hexen-l-ol, hexanal and ( )-2-hexenal, whereas the floral aroma is mainly due to the presence of hotrienol and nonanal [127-130]. 

Methionine can be obtained from enzymatic protein hydrolysates or from petrochemical sources. To a lesser extent than cysteine, it is a raw material in Maillard reactions for the preparation of process flavours and it can also be utilised as a precursor for the chemical preparation of the sulfide methional, which is an important flavour constituent for potato, malt, seafood and many other flavours. Methional can be reduced to methionol, which can be esterified with organic acids to, for instance, methionyl acetate and methionyl butyrate, which are useful compounds for pineapple and other fruit flavours (Scheme 13.16). 

Ribes mandshurica (Maxim.) Kom. R. mandshurica (Maxim.) Kom. f. subglabrum (Kom.) Kitag. Shan Ma Zi (fruit) Citric acid, malic acid, organic acids.48 Treat cold. 

The major organic acids in fruits other than grape are usually citric and malic acids (Table III). However, quinic acid, in addition to citric and malic acids, was a principal acid in peaches (71, 72). The main acid... 

The term wine refers to the natural beverage produced from the juice of sound and ripe grapes, in strict accordance with federal and state regulations. The stabilization principles discussed will have equal application to fruit wines in general except for tartrate stabilization since tartaric acid, the primary organic acid of grapes, is not found in any other fruits commonly used in winemaking. 

These acids are found ready-made in nature in great numbers. Some of them occur as free acids (citric acid, tannic acid, malic acid), others as esters (products of acids and alcohols, such as fats and oils and the flavors of many fruits and the odors of many flowers). Still other of these organic acids are produced by the action of bacteria (acetic acid from wine or cider, lactic acid when milk turns sour, butyric acid in rancid hutter). 

For each sample type, a literature review must be done prior to analysis to determine the appropriate organic acids and their concentrations. Typical acids include acetic, butyric, citric, formic, hippuric, isobutyric, isovaleric, lactic, malic, oxalic, phenylacetic, propionic, pyruvic, tartaric, uric, and valeric acids. The recipe for organic acid standard solutions (see Reagents and Solutions) describes standards that can be used for a number of fruit juices. 

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