Agilent 7890b

Sugar determination was carried out using the GC-MS method (Medeiros and Simoneit, 2007 (link); Ruiz-Matute et al., 2011 (link); Milkovska-Stamenova et al., 2015 (link); Wang et al., 2022 (link)). Briefly, sugar substances in grape berries were analyzed by gas chromatography (Agilent 7890B), mass spectrometry (7000 d), and a DB-5MS column. With helium as the carrier gas, the flow rate is 1 mL/min. The injector and source temperatures were maintained as per standard procedures. The oven temperature ramp progress was maintained at 170°C, 250°C, 280°Agilent 7890B), mass spectrometry (7000 d), and a DB-5MS column. With helium as the carrier gas, the flow rate is 1 mL/min. The injector and source temperatures were maintained as per standard procedures. The oven temperature ramp progress was maintained at 170°C, 250°C, 280°C, and 310°C. The details of the GC-MS analysis for specific parameters are presented in Table 2.
Based on the GC-MS platform, MetWare software (Wuhan, China, http://www.metware.cn/) was used to do a qualitative and quantitative analysis of the sugar components (Wang et al., 2022 (link)). For each group of samples, three biological replications were maintained. Sugar standards were procured from Olchemim, Aladdin (Shanghai), and Sigma (America). The detected sugar components include 9 monosaccharides and 4 disaccharides (Table 3).

The chemical analysis of thyme white essential oil was conducted using an Agilent 7890B (Agilent Technologies, Santa Clara, CA, USA) equipped with a flame ionization detector (FID). We used a DB-5MS (30 m × 0.25 mm i.d., 0.25 µm film thickness, Agilent, CA, USA) and HP-innowax column (30 m × 0.25 mm i.d., 0.25 µm film thickness, Agilent, CA, USA). The oven temperature was programmed as isothermal at 40 °C for 6 min, raised to 250 °C at the rate of 6 °C/min. The flow rate of the carrier gas (nitrogen) was 1.0 mL/min. The retention indices were calculated in relation to a homologous series of n-alkanes (C10-C29) under the same GC operating conditions. The constituents of thyme white essential oil were further analyzed using a gas chromatograph (Agilent 7890B)-mass spectrometer (Agilent 5977B MSD, Agilent Technologies, Santa Clara, CA, USA) (GC-MS) with an DB-5 MS column (30 m × 0.25 mm i.d., 0.25 µm film thickness, Agilent, CA, USA). The oven temperature program was the same as that used for the GC-FID analysis with helium as the carrier gas at a flow rate of 1.0 mL/min. Ionization was achieved using electron impact (70eV, source temperature 230 °C), and the scan range was 25–800 amu. Most compounds of thyme white essential oil were identified by comparing the mass spectra with those of authentic samples in the NIST MS library.

One (1) g of each type of chocolate was grated in a mortar to form a fine powder. Then, the chocolate powder was added to a septum vial (20 mL). Volatile compounds of each sample were extracted using the Headspace Solid-Phase Microextraction technique (HS-SPME). The fiber used for the extraction was 50/30 µm divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS, Stableflex 24 Ga, Manual Holder) of Supelco. The use of this fiber for cocoa organoleptic analysis allows obtaining a good separation of chromatographic peaks [41 (link)]. The SPME fiber was conditioned in the GC-MS Agilent 7890B’s injector system for 15 min at 250 °C. The conditioning was done below the suggested conditioning temperature provided by Supelco for this fiber type (i.e., 30 min at 270 °C) because it was found that our conditions extended the working life of our fiber without carry over compromise. After fiber conditioning, the SPMEs fibers were exposed to heated chocolate samples (at 60 °C) for 15 min in a thermostat block. Although individuals consume chocolate bars at room temperature, the temperature of 60 °C used was to maximized VOCs emission without risking degradation. The VOCs were then desorbed in the GC-MS Agilent 7890B’s injector system for 10 min at 250 °C.