Volatile sulfur compound in yeast

AMES Volatile Sulfur Compounds in Yeast Extracts... 

The anaerobic fermentation of sugars by Saccharomyces wine yeasts generates a variety of volatile metabolites that contribute to the sensory profile of wine. The important compounds include esters, higher alcohols, volatile fatty acids, carbonyls, and volatile sulfur compounds. The accumulation of these compounds in wine depends on the strain of yeast, must composition (chemical, physical and nutrient composition) and fermentation conditions. In addition, a variety of... 

Table 8D.3 Volatile sulfur compounds produced in wine by yeast metabolism ...

Two other low volatile sulfur compounds included in this study were 2-methylthio-l-ethanol (MTE) and 3-methylthio-l-p>rop>anol or methionol (MTP). MTP is considered to be the most important heavy sulfur compound involved with reduction defects brought about by yeast activity (Ribereau-Gayon et al., 2006b). MTP can generate odours reminiscent of cauliflower and cabbage at a concentration above its perception threshold (1200 pg/L). MTE... 

Yeast extracts represent an important source of volatile sulfur compounds, many of which possess low odor threshold values. They are used as sources of flavor for a range of savory foods, especially when a meaty note is required. In spite of the usefulness of yeast extracts, there are very few reports of their volatile flavor components. The production of yeast extracts is briefly reviewed, and the volatile sulfur compounds which have been identified are discussed. A recent study is presented in which the aroma components of some yeast extracts were analyzed. A total of 268 compounds were identified, including 67 sulfur compounds. The 34 sulfur compounds reported for the first time comprised 3 aliphatic sulfur compounds, one sulfur-substituted benzene derivative, 10 thiophenes, 18 thiazoles and 2 alicyclic sulfur compounds. Their importance as components of flavors and routes to their formation are considered. 

Yeast extracts (YEs) are sources of natural flavor compounds, and their exact composition varies according to the type of yeast and the conditions used for its propagation and the production of the final YE. This chapter is devoted to a review of the volatile sulfur compounds of YEs (many of which play a crucial role in determining the overall flavor) and to a report of some sulfor compounds which have recently been identified as components of selected YEs. 

Table IV. Selected volatile sulfur compounds reported in cysteine (or cystine)-reducing sugar (or carbonyl compound) model systems which have been identified in yeast extracts...

Since antiquity, animal milks have been converted by empirical processes to a wide variety of cheeses. With the development of microbiology as a scientific discipline, the critical role of microorganisms - bacteria, fungi, yeasts - in cheese began to be understood. Today, more than 650 cheese types are recognized and the flavor(s) of cheese has (have) now been investigated for more than a century.33 Typically, the situation is complex and the literature is enormous. For instance, more than 200 volatiles occur in Cheddar cheese. In a listing of 58 of these volatiles, 7 are sulfur compounds dimethyl sulfide (DMS),... 

The investigation of a series of model meat systems has demonstrated the important role of volatile sulfur-containing heterocyclic components substituted with sulfur in the 3-position. One of these 3-substituted sulfur compounds, 2-methy1-3-methy1thio-furan was identified recently in the volatiles from cooked beef aroma (5J and from a heated yeast extract composition (6J and is considered a meaty character impact compound. 

Methionine metabolism Sulfur compounds, responsible for aroma in wine and typically related to the grape variety, are released by yeast during the AF. In addition, the metabolism of the sulfur-containing amino acid methionine has an impact on wine aroma. Lact. brevis, Lact. plantarum, and O. oeni strains, using a pathway similar to dairy LAB, catabolize methionine producing light volatile sulfur molecules such as methanethiol and dimethyldisulfide, and heavy volatile molecules such as 3-(methylsulphanyl) propan-l-ol and 3-(methylsulphanyl) propionic acid (Pripis-Nicolau et al. 2004 Weimer et al. 1999 VaUet et al. 2008). In wine, O. oeni strains produce more heavy compounds, mainly 3-(methylsulphanyl) propionic acid, than lactobacilli. In water 3-(methyl-sulphanyl) propionic acid descriptors are chocolate and roasted but these notes are not found in wine where they are replaced by red fruit and earthy odors probably because of interactions with other wine components (Pripis-Nicolau et al. 2004). 

---