Sorbic acid preparation

Sorbic acid is easily oxidized. This oxidation is accompanied by the development of a glyoxal-like flavor in sorbic acid preparations and a brown color in a wide variety of model foods in which sorbic acid was included. Amino acids accelerate color development (Wedzicha et al., 1996). 

Sorbic acid is prepared by the condensation of crotonaldehj de with malonic acid ill the presence of pyridine at 100° (Doebner reaction) ... 

Sorbic acid anhydride [13390-06-2] can be prepared by heating the polyester of 3-hydroxy-4-hexenoic acid with sorboyl chloride [2614-88-2] or by reaction of sorbic acid with oxalyl chloride (15,16). Preparation of the esters of sorbic acid must be controlled to prevent oxidation and polymerization. The lower sorbic acid esters have a pleasant odor. 

Preparing sorbic acid by reaction of crotonaldehyde and acetone followed by oxidation of the crotonyUdenacetone is of interest in the former Soviet Union (41,42) ... 

Analytical Techniques. Sorbic acid and potassium sorbate are assayed titrimetricaHy (51). The quantitative analysis of sorbic acid in food or beverages, which may require solvent extraction or steam distillation (52,53), employs various techniques. The two classical methods are both spectrophotometric (54—56). In the ultraviolet method, the prepared sample is acidified and the sorbic acid is measured at 250 260 nm. In the colorimetric method, the sorbic acid in the prepared sample is oxidized and then reacts with thiobarbituric acid the complex is measured at - 530 nm. Chromatographic techniques are also used for the analysis of sorbic acid. High pressure Hquid chromatography with ultraviolet detection is used to separate and quantify sorbic acid from other ultraviolet-absorbing species (57—59). Sorbic acid in food extracts is deterrnined by gas chromatography with flame ionization detection (60—62). 

Bacon, processed with 40 mg/kg of nitrite and 0.26 sorbate contained an average of 8.7 pg/kg of NPYR, whereas samples prepared with 120 mg/kg of nitrite contained an average of 28.1 yg/kg of NPYR. This marked reduction in NPYR levels is clearly due to the reduced levels of nitrite, although it has been reported that sorbic acid also possesses anti-N-nitrosamine activity (47). 

Sorbic acid has been prepared from crotonaldehyde 1 5 or aldol6 and malonic acid in pyridine solution by hydrogen peroxide oxidation of the condensation product of crotonaldehyde and pyruvic acid 7 and by the action of alkali on 3-hydroxy-4-hexenoic acid,8 9 /3,5-disulfo-w-caproic acid,10 and parasorbic acid.1112... 

Figure 5. Sorbic acid molecules on HOPG as reported by Smith et. al. (10). This surface was prepared by spin-coating a dilute sorbic acid-benzene solution onto a freshly cleaved HOPG substrate. Images of the surface were obtained in liquid helium. The elongated structure shown was representative of those present on surfaces prepared with this procedure.

For a liquid or semi-solid pharmaceutical dosage form, it is crucial to include a preservative in the formulation. Commonly used preservatives in these systems include sodium benzoate, EDTA, sorbic acid, and parabens. A generic HPLC method is also recommended for the preservatives used in liquid formulations for routine monitoring to ensure the stability of the preservative itself and it must be validated specific to its use with the dosage form. (See chapters on Sample Preparation and Method Development.)... 

Potassium sorbate is prepared by reacting potassium hydroxide with sorbic acid, followed by evaporation and crystaUization ... 

Examples given in Expt 5.216 include the preparation of non-2-enoic acid starting from hexanal, but-2-enoic acid (crotonic acid) from acetaldehyde, and also hexa-2,4-dienoic acid (sorbic acid) starting from the conjugated aldehyde crotonaldehyde. 

Natta, Farina, and Donati (47) have prepared diisotactic polymers from alkyl esters of sorbic acid and /5-styryl acrylic acids by anionic initiation with optically pure 2-methyl butyllithium. The polymers were optically active. 

Conjugated olefinic acids containing more than one double bond are prepared from olefinic aldehydes. Thus, acrolein and crotonaldehyde with malonic acid yield vinylacrylic acid (60%) and sorbic acid, (32%) respectively. In this manner, the completely conjugated 2,4,6,8,10,12-tetradecahexaenoic acid, CH3(CH = CH)6COjH, has been made. ... 

The bydrolysis can be carried out induetrially on a mixture of the lactone and its polymer. Aa a matter of fact, the stracid medium and the high temperature naed cause dehydration to the hydro. y acid, and tine method, which ie a variant of the pcceding ones, ie vaod for the preparatiem of unsaturated tlerivatives. Sorbic acid and its esters have b n prepared iu this way from ketone and crotonaldehyde. 

Potassium sorbate is prepared from sorbic acid and potassium... 

Sorbic acid is an antimicrobial preservative with antibacterial and antifungal properties used in pharmaceuticals, foods, enteral preparations, and cosmetics. Generally, it is used at concentrations of 0.05-0.2% in oral and topical pharmaceutical formulations, especially those containing nonionic surfactants. Sorbic acid is also used with proteins, enzymes, gelatin, and vegetable gums. It has been shown to be an effective preservative for promethazine hydrochloride solutions in a concentration of 1 g/L. ... 

When stored in glass containers, the solution becomes very pH sensitive therefore, preparations using sorbic acid as a preservative should be tested for their microbial purity after prolonged periods of storage. 

Naturally occurring sorbic acid may be extracted as the lactone (parasorbic acid) from the berries of the mountain ash Sorbus aucuparia L. (Fam. Rosaceae). Synthetically, sorbic acid may be prepared by the condensation of crotonaldehyde and ketene in the presence of boron trifluoride by the condensation of crotonaldehyde and malonic acid in pyridine solution or from 1,1,3,5-tetraalkoxyhexane. Fermentation of sorbaldehyde or sorbitol with bacteria in a culture medium has also been used. 

Benzoic acid is often combined with sorbic acid in order to reduce its peculiar flavor. It has to be stated, however, that this is at least partly caused by impurities in the benzoic acid preparation used. 

Treatment of various foods (e.g., absorption of sorbic acid during processing of dried prunes, or loss of sorbic acid during cooking of prepared foods). 

Preparation of the fruit. Since the early research of Webb et al. (33) several workers have recognized the problem of artefact formation during work-up of grapes. Accordingly, these investigators have employed additives such as NaF and ascorbic acid or SO. and sorbic acid to minimize microbial and oxidative degradation of the juice (2,10,34). 

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