Comparison of dynamic headspace methods used for the analysis of the volatile composition of Spanish PDO ewe’s raw milk cheeses

Abstract

-Different dynamic headspace (DHS) methods used for determination of volatile compounds in cheeses were compared. Three different laboratories using gas chromatography coupled to mass spectrometry carried out the analyses of volatile compounds of Spanish Protected Designation of Origin ewe's raw milk cheeses. One laboratory used "purge and trap" (P&T) with thermal desorption of the trap by ultrafast microwave heating (MWH) and the other two laboratories used P&T with thermal desorption of the trap by resistive heating (RH). Each method detected around 78-85 different individual compounds which belonged to different chemical groups, namely, acids, alcohols, ketones, esters, aldehydes, sulphur compounds, hydrocarbons and terpenes. Using the P&T-MHW method, larger percentages of acids and aldehydes in the cheeses were found compared with the P&T-RH methods, whereas the contrary occurred for the percentages of alcohols and ketones. Differences in the percentages of some volatile compounds such as ketones, alcohols and acids between the laboratories using P&T-RH under different analytical conditions were also recorded. The results pointed out differences in the selectivity for the extraction of various volatile compounds from cheese samples according to the DHS methods used, particularly when using tenax or graphitised carbon as trap absorbents. In spite of these differences, both P&T-MWH and P&T-RH methods were equally satisfactory for the comparison of the different cheese varieties. However, each of the DHS methods was more suitable for the characterisation of the volatile compounds of a particular cheese type. De plus, des différences dans les pourcentages de certains composés volatils, tels que cétones, alcools et acides ont également été observées entre les laboratoires utilisant le système de P&T-CR dans des conditions différentes. Les résultats soulignent des différences en termes de sélectivité d'extraction des volatils à partir des échantillons de fromage selon la technique d'extraction employée, et en particulier selon la nature de l'absorbant du piège (tenax ou charbon). Malgré ces différences, les deux méthodes P&T-CMO et P&T-CR se sont révélées également satisfaisantes pour comparer différentes variétés de fromages. Cependant, chacune des méthodes d'extraction était plus appropriée pour caractériser les composés volatils pour un type de fromage en particulier.fromage / composé volatil / espace de tête dynamique / étude inter-laboratoire

The role of the canonical biplot method in the study of volatile compounds in cheeses of variable composition

“…Analyzing the variables responsible for this separation, it may be seen that this difference is due to the fact that the samples take higher values in ethanol, ethyl acetate, acetaldehyde and 2-butanol, together with lower values in 2-heptanone, 2-pentanone, isopropanol, 2-pentanol, acetone and 2-heptanol. This result is in agreement with previous works indicating that ethanol is present at higher concentrations in cow's cheese than in sheep's cheese (Molina et al, 1999), while acetaldehyde is not one of the more important aldehydes in sheep's cheese (Barron, et al, 2005b;Fernández-García et al, 2004a, b) and it could not be found in goat's cheese (Castillo et al, 2007).…”

Volatile compounds associated with desirable flavour and off-flavour generation in ewe´s raw milk commercial cheeses

“…The volatile profile of ND cheeses, along with their above mentioned sensory characteristics, was concordant with results previously reported on Idiazabal cheese variety [5,14]. Acids were the most abundant chemical family in ND cheeses mainly due to the content of straight short-chain free fatty acids (FFA), in particular n-butanoic, n-hexanoic and n-octanoic (Table 2).…”

“…Some studies have associated these straight volatile acids with desirable and characteristic acid, pungent and rennet flavours of particular cheese varieties [5,12,[30][31][32][33]. So, the highest relative abundance of straight acids mostly contributed to the desirable flavours slightly acid, pungent and natural rennet in ND cheeses.…”

Solid-Phase Microextraction to the Study of the Stability of Selected Volatile Constituents in Irradiated Manchego Cheese

“…As far as sample 1 composition is concerned, wherein acetoin was one of the main components, decanoic acid was not detected. In this regard, high amounts of acetoin have also been determined, especially in industrial Manchego cheese by using different extraction techniques (Barron et al 2005;Soto-Yarritu et al 2007;Poveda et al 2008). It may be due to the action of commercial starters containing Lactococcus lactis subsp.…”