Sorbic acid, reduction

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). 

Since our initial communication (10) concerning the catalytic reduction of organic substrates by this homogeneous hydrogenation system, two further reports have come to our attention de Vries (2) demonstrated the reduction of sorbic acid to 2-hexenoic acid and Kang (8) described the reductive amination of a-keto acids. 

Scheme 3.5 Reduction of sorbic acid with [RuCp (T 4-sorbic acid)][OTf] as catalyst...

Potassium sorbate is used as a yeast inhibitor for the stabilization of table wines containing residual sugar. When conditions permit the growth of lactic acid bacteria, wines treated with sorbic acid can develop an odor resembling crushed geranium leaves (Burkhardt, 1973 Radler, 1976 Wurdig et al., 1975). This result due to bacterial reduction... 

Lewis acid catalyzed versions of [4 4- 2] cycloadditions are restricted to functionalized dieno-philes. Nonfunetionalized alkenes and alkynes cannot be activated with Lewis acids and in thermal [4 + 2] cycloadditions these suhstrates usually show low reactivity. It has been reported that intcrmolecular cycloaddition of unactivated alkynes to dienes can be accelerated with low-va-lent titanium, iron or rhodium catalysts via metal-mediated - -complex formation and subsequent reductive elimination39 44. Usually, however, low product selectivities are observed due to side reactions, such as aromatization, isomerization or oligomerization. More effective are nickel-catalyzed intramolecular [4 4- 2]-dienyne cycloadditions which were developed for the synthesis of polycycles containing 1.4-cyclohexadienes45. Thus, treatment of dienyne 1, derived from sorbic acid, with 10mol% of Ni(cod)2 and 30 mol % of tris(o-biphenyl) phosphite in tetrahydrofuran at room temperature affords bicyclic 1,4-dienes 2, via intramolecular [4 + 2] cycloaddition, with excellent yield and moderate to complete diastereocontrol by substituents attached to the substrate. The reaction is sensitive towards variation in the catalyst and the ligand. 

Studies on the metabolism and saturation of sorbic acid have shown that fungi are capable of producing /ra .s-4-hexenol60-61. This bioconversion comprises the reduction of the carboxy group to the alcohol which seems to be the initial reaction, followed by hydrogenation of the a,/(-double bond of the unsaturated alcohol (see Section 2.5.1.3.1.2.). The remote double bond... 

Guillard, V. Issoupov, V. Redl, A. Gontard, N. Food preservative content reduction by controlUng sorbic acid release from a superficial coating. Innovat. Food Sci. Emerg. Tech. 2009,10 (1), 108-115. 

Winemakers wishing to stabilize juice with sorbate should also consider the potential presence and activity of LAB. In the absence of alcoholic fermentation and other countermeasures (SO2, filtration, etc.), bacterial reduction of the sorbic acid to sorbyl alcohol may occur. Upon blending... 

Packaging material compatibility (Wallhdufier, 1984). The suitability of a preservative, depends not only on the breadth of its efficacy spectrum and the other criteria already mentioned, but also on primary packaging materials. Efficacy reduction in this case is mainly due to absorption effects, and depends on the type of formulation -how lipophilic the preservatives are and the plastics used. Plastics such as polyethylene absorb quaternary compounds [II, 18.1.], PHB ester [II, 8.1.11.], sorbic acid PI, 8.1.5.] benzoic acid [II, 8.1.9.] etc., from fluid and semi-fluid contents, leading to a reduction in their efficacy, often within weeks. 

Off-flavors in dairy products have been reviewed (86,87), but there are several recent developments. In sour-cream buttermilk, the key odorant responsible for a metallic off-flavor was identified as ( ,Z)-2,6-nonadienol (120). During cream fermentation, its formation occurs from peroxidation of alpha-linolenic acid to generate the 2,6-nonadienal precursor, with subsequent reduction to the dienol by starter culture reductases that remain active during storage. Metallic off-flavors are not formed readily in fermented sweet-cream buttermilk due to the much lower concentration of alpha-linolenic acid present (121). The common use of sorbic acid and potassium sorbate as a mold inhibitor in commercial dairy products often produces an off-flavor described as kerosene, plastic-, or paintlike, which may incorrectly be attributed to packaging materials. The flavorant... 

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. 

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