Combinatorial Approach to Flavor Analysis. 2. Olfactory Investigation of a Library of S-Methyl Thioesters and Sensory Evaluation of Selected Components

Abstract

The odor characteristics of individual components present in a library comprised of S-methyl thioesters were determined independently by two laboratories using similar but not identical techniques. The odor potency was assessed by values of best estimate-GC-lower amount detected by sniffing (BE-GC-LOADS). For small and medium chain S-methyl thioesters, these values were found to increase from 6 ng for S-methyl thiobutanoate to 90 ng for S-methyl thiostearate. All assessors detected a "green", "floral", or "pineapple" odor for S-methyl thiohexanoate and described thioesters containing a 2-6 carbon chain length as "cheesy". The results of this preliminary analysis were confirmed by a more extensive study of selected compounds, namely S-methyl thioacetate, S-methyl thiopropionate, S-methyl thiobutanoate, and S-methyl thiohexanoate, using a trained panel of 18 subjects. The subjects confirmed the presence of the "green" and "fruity" notes in the odor of S-methyl thiohexanoate. The analysis also revealed a significant difference in the odor of S-methyl thiopropionate relative to that of S-methyl thioacetate and S-methyl thiobutanoate. When "cheesy" characteristics were mentioned, the majority of panelists clearly associated the flavor of S-methyl thiopropionate with Camembert with almost 20% of all the descriptors given referring specifically to this cheese variety as compared to about 2 and 5% in the case of S-methyl thioacetate and thiobutanoate, respectively. Prompted by this observation, two samples of Camembert prepared from unpasteurized and pasteurized milk were analyzed and relatively large amounts of S-methyl thiopropionate were found in the former but not in the latter cheese. The results obtained in the course of this work suggest that the sensory analysis of combinatorial libraries is a useful new approach in the search for new commercial flavors and/or identification of characteristic flavors in foods.

Esters and their biosynthesis in fermented dairy products: a review

“…Furthermore, this review is focused on the biosynthesis of fatty acid ethyl esters formed from ethanol (the most common alcohol found in cheese) that impart fruity flavours and on the biosynthesis of 2-phenylethyl esters formed from 2-phenylethanol that produce floral/rose-like flavours. In addition, the formation of S-methylthioesters that impart different flavour notes, (e.g., cheesy, cooked cauliflower) (Cuer et al, 1979c;Berger et al, 1999b;Khan et al, 1999) is also briefly assessed in the broad context of ester biosynthesis. most frequently found (Table 1).…”

Enzymatic versus spontaneous S-methyl thioester synthesis in Geotrichum candidum

“…These compounds contribute to the characteristic aroma of cheese odor, especially in smear-ripened varieties. The speci¢c £avor imparted by these compounds depends on the chain length and con¢g-uration of the acyl moiety [11]. Among them, S-methyl thioacetate (MTA) which has the £avor of cooked cauli£ower, is the most commonly found thioester in cheeses [12,13].…”

Occurrence of the ribes odorant 3‐sulfanyl‐3‐methylbutyl formate in aged beers

“…As described by Berger et al, [23] the parameter 'best-estimated-GC-lower amount detected by sniffing' (BE-GC-LoADS) was defined as the geometric mean between the lowest mass of compound perceived at the outlet of the GC-odour port and the highest undetected amount injected onto the column. Experiments were performed with the initial solution of a compound and its sequential dilutions as follows: 1/2, 1/5, 1/10, 1/20, 1/50, 1/100, 1/200, 1/500, 1/1000, and so on.…”