Flavour significant compounds in yeast autolysate Gistex X‐II powder. Part I. Acidic fraction

Abstract

Basic informations about the composition of yeast autolysate GistexLX-11-powder were obtained. The representative sample of volatile flavour-significant compounds was isolated. There were 29 substances identified in the acidic fraction of the isolate and the odour of this fraction was organoleptically evaluated. The organoleptic properties were mainly influenced by the presence of lower fatty acids and phenylacetic and 3-phenylpropionic acids. Two sulphur-containing heterocyclic acids, i. e. 2-thiophenecarboxylic and 5-methyl-2-thiophenecarboxylic acids were identified for the first time as volatile constituents of foodstuffs. Flavour properties of these two and other 6 sulphur-and oxygen-containing heterocyclic acids were evaluated and their mass spectra are presented.Hydrolyzed vegetable proteins have been widely used for flavouring of many foodstuffs [l]. There are various types of these products that can be divided into 2 groups. First, chemical hydrolyzates produced mainly by hydrochloric acid hydrolysis, second, enzymic hydrolyzates (shoyu, yeast autolysates, etc.).A great number of studies has paid attention to flavour-significant compounds contributing to the typical flavour of Japanese shoyu [2-41. NONUMURA et al. HOUGH et al. [16] studied the biochemical changes occurring during yeast autolysis. They described the principle hydrolytic enzymes splitting the main components of yeast cells, i.e. proteins, saccharides and nucleic acids.This study was undertaken in order to receive some additional informations about flavoursignificant components of yeast autolysates. Experimental Material and rejerence compoundsYeast autolysate Gistex X-I1 powder (Koninklijke Netherlandsche Gist-en Spiritusfabriek N.V., Delft, Holland). The following heterocyclic acids were synthesized: 2-thiophenecarboxylic acid [17, 181, 5-methyl-2-thiophenecarboxylic acid [19, 201, 2-thienylacetic acid [21], 5-methyl-2-thienylacetic acid [2 I], 3-(2-thienyl) propionic acid [20,22],2-furylacetic acid [23-251, 5-methyl-2-furylacetic acid [23, 261. Other chemicals were obtained from Lachema n.p., Brno, Czechoslovakia. ApparatusA gas chromatograph Chrom 4 equipped with a flame ionization detector (Laboratorni piistroje n.p., Praha, Czechoslovakia), a LKB 9000 mass spectrometer (LKB Producter AB, Stockholm, Sweden). MethodsIsolation of flavour-signljkant compounds 8000 g of the yeast autolysate were mixed with sand and all the portions, 1000 g each, were extracted in a SOMLET apparatus with diethyl ether for 52 h. The combined extracts were dried over anhydrous sodium sulphate and concentrated to 100 ml using a Snyder column. Acidic fraction90 ml of the above mentioned diethyl ether solution were extracted with five 20 ml portions of 5 7; sodium bicarbonate, the extract was evaporated under vaccum nearly to dryness, acidified with hydrochloric acid to pH 0.5 and extracted again with five 20 ml portions of diethyl ether. The combined extracts were dried with anhydrous sodium sulphate and concentrated as above to 1 ml.One half of the obtained...

Characterization of Aroma-Active Compounds in Four Yeast Extracts Using Instrumental and Sensory Techniques

“…The organic acids in YEs may be from yeast metabolism; on the other hand, they may be the oxidation products of the corresponding aldehydes for thermal oxidation during evaporation of YE manufacture. This is supported by the fact that Davídek et al identified a large number of acids in their aroma isolate of autolyzed yeast (AY) powder, and these probably derived from the corresponding aldehydes during the more rigorous thermal and oxidative drying AY to powder form.…”

Thermochemical properties of three 2-thiophenecarboxylic acid derivatives

“…This thiophene derivative is used as an intermediate in the synthesis of a thienylthiazolylthioaminoalcohol derivative, applied in the treatment of irregular impulse, heart sickness or hypertension [19], in the preparation of phosphorylamides derivatives, that possesses excellent antibacterial activity especially against Helicobacter pylori [20] and is applied in the synthesis of novel 3-substituted-2-oxindole derivatives that are analgesic, antiinflammatory and antiarthritic agents in the treatment of chronic inflammatory diseases [21]. Besides the therapeutic applications cited above, 2-thiophenecarboxylic acid and 5-methyl-2-thiophenecarboxylic acid were identified, for the first time, as volatile constituents of foodstuffs [22].…”

Aroma‐active components of yeast extract pastes with a basic and characteristic meaty flavour

“…Additionally, the processing conditions, such as nature of the yeast and the presence of additional components, are likely to lead to flavour development, and the temperature of concentration or drying, could also have effects on the specific flavour profiles of yeast extract pastes. Munch and others studied several types of yeast extracts from different manufacturing sources and different aroma compounds were identified and characterised …”