Organoleptic volatile compounds

This article contains a detailed summary of the experiments carried out by LCA Coates Lorilleux aimed at evaluating the sensorial perception thresholds of ethyl acetate (and other solvents) used in rotogravure printing of flexible packaging for food. The methodological approach applied in the present study can be deemed a valid tool of study for the organoleptic behaviour of solvents and/or volatile compounds other than ethyl acetate that may be present inflexible materials. 8 refs. 

Proteins can bind flavor constituents, especially volatile carbonyls. When bound to protein, some volatile aldehydes behave as if they were non-volatile compounds and are retained over a long period of time during storage. Such interaction may cause chemical as well as organoleptical deterioration of food proteins. 

When you enter a damp cellar, open a packet of mushrooms or go for a walk in the woods in the autumn, you will often smell the chemical activities of fungi. Although many of the more pungent smells of decay are associated with bacterial activity, fungi make a characteristic, often more musty , contribution. The volatile compounds of mushrooms contribute to their organoleptic properties. Other compounds behave either as insect attractants or as feeding deterrents. Yet others contribute to the relationship of a fungus with its competitors. 

Bade-Wegner et al. (1998) studied the volatile compounds associated with the over-fermented flavor defect, considered to be one of the most objectionable organoleptic defects in coffee. They examined two defective samples of arabica and one sample of robusta green coffees, comparing them to reference products with a neutral flavor. As the off-flavor can be due to overfermentation of green coffee or to the presence of so-called stinker beans, the authors considered that the previous studies and identifications were more indicative than causative. By GC-olfactometry, three fruity odor notes were perceived, at different intensities, that were attributed to ethyl 2-methylbutanoate (Section 5,F.40), ethyl 3-methyl-butanoate (Section 5,F.41) and ethyl cyclohexanecarboxylate (Section 5,F.46). The three esters were considered to be the most important contributors to the over-fermented flavor defect. 

The organoleptic character of hydrocarbons has received little attention in spite of the fact that compounds such as hexane or cyclohexane have a detectable odor. Boelens (1974) reported that the members of a panel could not make any distinction between Cj i - to C)5-alkanes and the corresponding aliphatic alcohols. On the contrary, polyunsaturated hydrocarbons possess typical odor qualities and may therefore be important contributors to food flavors (Ohloff, 1978a) but their presence in coffee is limited to aliphatic volatile compounds, such as pentadiene (A.41) and isoprene (A.44), and to 5-methyl-1,3-cyclohexadiene (A.47), not forgetting the terpenes mentioned later. Nevertheless the flavoring power of these paraffins is certainly negligible as compared with the most characteristic constituents of coffee, cocoa, and tea. 

Over the past 15 years, much research has been done and over twenty articles of real scientific value have been published on this subject. These articles examine the composition of cork in terms of volatile compounds, especially those molecules likely to cause organoleptic defects in wine. 

With improved analytical methods there has been a large increase in the number of compounds identified in wines. Volatile compounds from different families (such as alcohols, esters, aldehydes, terpenes, etc.) play an important role in the organoleptic characteristics of wines. This wide variety of compwimds with different chemical properties and with different concentrations makes the flavour pa-ofile of wines very complex. Therefore, it is necessary to standardise the terminology so as to facilitate the knowledge of the aromatic profile of wines. 

Bleaching is achieved by adsorption on activated bleaching clays (sorbents of the aluminium silicate type) or in combination with other adsorbents (such as activated carbon, also known as activated charcoal) to remove oil soluble pigments (such as carotenoids and chlorophylls), residual phosphoHpids, and eventually soap residues resulting from the deacidification process. Volatile substances are removed by deodorisation via steam distillation under reduced pressure. The volatile compounds are mainly responsible for the unpleasant smeU and aftertaste of cmde oil, so this process provides organoleptically neutral, indifferent oils. 

Schmidt NF, Missan SR, Tarbet WJ. 1978. The correlation between organoleptic mouth-odor ratings and levels of volatile sulfur compounds. Oral Surg Oral Med Oral Pathol 45 560-567. 

Veciana-Nogues, M., Marine-Font, A. and Vidal-Carou, M.C. (1997). Biogenic amines as hygienic quality indicators of tuna. Relationships with microbial counts, ATP-related compounds, volatile amines and organoleptic changes, Jl. Agric. Food Chem., 45, 2036. 

Different studies have focused on the biosynthesis of aroma compounds during MLF and the concomitant organoleptic consequences (Laurent et al. 1994). Maicas et al. (1999) demonstrated that MLF noticeably changes major and minor volatile... 

Since yeast lees may adsorb some aroma compounds responsible of off-flavours in wines (volatile phenols), these components have been also proposed such as a cost-effective and efficient approach to remove or to decrease organoleptic defects in wine (Chassagne et al. 2005). 

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