Effect of adding hygroscopic salts on the analysis of the volatile fraction of cheese

Abstract

The dynamic headspace technique coupled with gas chromatography and mass spectrometry is frequently used to characterize the volatile fraction of food products [1][2][3][4][5][6][7]. However, water is very often the main volatile component and generates artefacts during the different steps of the analysis [8][9][10]. Several approaches to limit these artefacts have already been tested. They include acting on the sample or the adsorbent [11][12][13][14], inserting a water trap between the sample and the adsorbent [15][16][17][18], modifying injection parameters [19] or selecting a particular type of chromatographic column [20].Water activity in the sample can be lowered simply by mixing in hygroscopic substances such as salts or sugars. To date, many studies have been conducted to evaluate the effect of such substances on the analysis of the volatile fraction of liquids such as apple juice [21], milk [22] or model aqueous solutions [23][24][25][26][27]. These investigations have shown that adding hygroscopic salts increases the vapor pressure and therefore the concentration of the volatile substances in the headspace of samples. However, very little work has been published on the effects of using such salts in solid or semi-solid media [28].The objective of this work was therefore to determine whether or not the incorporation of various hygroscopic salts into cheese, which modifies both the structure and the physical and chemical properties of the product, could facilitate the analysis of its volatile fraction, and if so to what extent. Materials and methods SamplesCommercial wax-coated pre-portioned hard processed cheeses were selected (mini-Babybel ® ). Such samples are biochemically stable, homogeneous, and have a relatively simple volatile fraction. Their water content was 48 % and the relative humidity of their headspace was 72 %. Storage of samplesThe cheese samples in their original wax packaging were wrapped in aluminium foil, vacuum-sealed in polyethylene bags and stored at -25°C. Before each analysis the sample was left overnight at room temperature. Choice of saltsFive salts were chosen for their hygroscopic properties and their low reactivity toward the matrix of the products stud- n°28 114.365). The salts were dehydrated in an oven at 105°C before use. To determine the least quantity of salts necessary to obtain a dense homogeneous mixture with medium particle size, preliminary tests were conducted on the texture of the cheese-salt mixtures. For 4 g of cheese the quantities of salt to be added were: 4 g of calcium chloride, 2 g of magnesium sulfate, 6 g of potassium carbonate, 10 g Abstract. We investigated the effect of adding hygroscopic salts on the analysis by dynamic headspace -gas chromatographymass spectrometry of the volatile fraction of cheese. We tested five salts: calcium chloride, magnesium sulfate, potassium carbonate, sodium chloride and sodium sulfate. Relative humidity of the headspace, pH value of the matrix, desorption of volatile components and their odor were modified differentl...

Effect of a condenser on the analysis by dynamic headspace-GC-MS of the volatile fraction of a cheese

“…2). This observation confirms both the efficiency of the dry purge for rapidly removing the water adsorbed on the Tenax, and the existence of residual water difficult to eliminate from the adsorbent (CanacArteaga et al) [18].…”

“…After preliminary trials carried out with and without the dry purge, with a condenser operating at -12, -7 and 0°C, the duration of this operation was set at 10 min for all the analyses. This value, which is slightly higher than that recommended by Canac-Arteaga et al [18] affords an essentially artifact-free analysis of the very water-rich volatile fraction retained by the condenser.…”

“…To determine the origin of the noise in this chromatogram segment, an average spectrum was recorded. The origin of this noise has already been described by CanacArteaga et al [18]. The peak area of the volatile components (arbitrary units of area, a.u.a.)…”

“…For each volatile component, a comparison for all temperatures of the fractions retained by the condenser (RC) and those not retained (NRC) was made with a reference analysis, i.e., with no condenser and with a dry purge under the conditions described by Canac-Arteaga et al [18]. As in all the tests performed in this work, the reference analysis was carried out twice.…”

Detection of Volatile Compounds of Cheese and Their Contribution to the Flavor Profile of Surface‐Ripened Cheese

“…Another solution is to install a cold‐water trap (condenser at ∼–10 °C) located before the trap to condense the residual water from the sample (condensation technique) (Canac‐Arteaga, Viallon, & Berdagué, ). Other approaches include mixing a hygroscopic salt (such as sodium sulfate, sodium chloride, or potassium carbonate) with the sample (Canac‐Arteaga, Begnaud, Viallon, & Berdagué, ; Valero et al., ; Villaseñor et al., ), or placement of a cartridge with a hygroscopic salt (such as sodium carbonate, magnesium sulfate, or calcium chloride) in front of the trap to eliminate water (Guillot, Fernandez, & Le Cloirec, ). A drying tube made of permeable material such as Nafion has also been used to facilitate diffusion and to remove water from the sample (Pankow, ).…”