Simple analysis of odorous fatty acids in distillery effluents by capillary electrophoresis

Abstract

Short-chain fatty acids are mainly produced by food and beverage industries during fermentation processes. For example, volatile acidity, which gives bad taste to wine, may appear during the vinification process, especially during storage. This is due to alcohol oxidation by lactic or acetic bacteria [1,2]. The volatile acids formed are acetic, propionic, butyric and valeric acids [1,2]. These fatty acids are malodorous at relatively low contents in ambiant air, i.e. the perception levels of acetic, propionic, butyric and valeric acids are respectively 2, 0.109, 0.014 and 0.020 mg.m -3 [3]. Consequently, these compounds may contribute greatly to the unpleasant odor generated by distilleries where byproducts of the wine industry are used as raw materials.In order to reduce the olfactory pollution in such activities, the compounds responsible for the malodorous emissions must be monitored. Therefore, 4 fatty acids (acetic, propionic, butyric and valeric acids) were chosen as odor markers and analysed in liquid effluents of the main steps of the process. According to the numerous analysis expected, a simple, cheap and fast method was requested. The analytical techniques generally used for the determination of carboxylic acids involve gas chromatography [4,5]. However, the polar acids are not suitable for direct GC injection. Therefore, a preliminary derivatization step is needed, using, for example, esterification by pentafluorobenzyl bromide (PFBBr) or methylation catalyzed by trifluoroboron (BF 3 ) [5,6]. These reactions are performed in organic media and thus require preliminary solvent or solid-phase extractions [7]. These procedures are long and complex to carry out. A more simple and specific approach may consist in performing a separation by ionic chromatography [8]. In this case direct injections of aqueous samples are allowed, but a possible damage of the column can occur after numerous analysis of complex matrices such as distillery effluents. Indeed, this kind of samples are constituted of a wide diversity of organic compounds such as alcohols, carbohydrates, ketones, aldehydes, esters and acids. Thus, capillary zone electrophoresis appears as an interesting alternative method. As example, Roldan-Assad et al. developed the separation of linear saturated fatty acids in their free form from C2 to C14 in less than 10 min [9]. The solubility of the most apolar compounds in the water-based electrolyte was improved by adding cyclodextrins and methanol. An indirect UV detection led to minimum detectable concentrations of the order of 0.2 -0.5 mg.L -1 . Another study also showed good performances of CZE for the analysis of organic acids in biological matrices with limited sample preparation [10].According to these encouraging results, this paper described the development of a CZE method for the fast analysis of short-chain fatty acids in distillery effluents. The performances were defined according to different experimental conditions in order to improve the sensitivity. The possibility of analysing gaseous samp...

The storage of grape marc: Limiting factor in the quality of the distillate

“…The bibliographic references that exist on the characteristics and conditions of this important stage indicate, among others, that the grape marc must be stored in the absence of oxygen, in small containers, and that storage should not be prolonged, although it must be sufficient to complete the alcoholic fermentation while avoiding the proliferation of microorganisms (Cortés, Gil, & Fernández, 2001, 2006Da Porto, 2002;Usseglio-Tomasset, 1971;Versini & Odello, 1990;Williams & Strauss, 1978). Principally, they are acetic, lactic and butyric bacteria that would cause undesirable secondary fermentations through the formation of a series of volatile compounds with negative aromatic connotations, which notably degrade the sensorial quality of the resulting distillate (De Rosa & Castagner, 1994;Desauziers, Avezac, & Fanlo, 2000;Nykänen, 1986;Silva & Malcata, 1998). Among these compounds should be mentioned: ethyl acetate, the acetic, butyric and propionic acids, 2-butanol and ethyl esters of long-chain fatty acids.…”

Discrimination and risk assessment due to the volatile compounds and the inorganic elements present in the Greek marc distillates Tsipouro and Tsikoudia

“…According to table III, the presence of short chain fatty acids in these concentrations, which are far above their perception threshold, decreases the distillate quality (DESAUZIERS et al, 2000).…”

“…Short chain fatty acid contents increase as a consequence of extended fermentation (SILVA and MALCATA, 1999) of grape pomace, improper conditions of storage (ORRIOLS and BERTRAND, 1990;DESAUZIERS et al, 2000) and origin of distillate from « tail » fraction (SILVA and MALCATA, 1999).…”

Capillary electrophoresis for short‐chain organic acids and inorganic anions in different samples

“…Nevertheless, benzoic acid [12], ascorbic acid [17] alone or with isoascorbic acid [49], and a group of compounds produced as effluents in a distillery [69] or in the production of sugar [71] have been measured with normal polarity. In the case of clinical analysis, vanillylmandelic acid (VMA) and homovanillic acid (HVA), which contain an aromatic ring and therefore bigger size, normal polarity is the most common mode, but reversed polarity has also been employed [122].…”

“…The important observation is that the electrophoretic mobilities of the anions change at different rates and that permits to manipulate the selectivity. Nonabsorbing electrolytes have been employed for direct detection such as tetraborate at pH 9.3 [21,28], phosphate at pH 10.2 [69], pH 7.5 [19], pH 6.5 [33], 6.25 [78], and pH 6 [59]. Regarding concentration, it affects EOF, electrodispersion of the analyte bands, and current generated at a given potential.…”