Gc eims

IAA and indole-related compounds were determined by the Salkowski colorimetric reaction and GC-MS analysis. Bacterial strains JEP3, JEP8, JEP33, JEC8, JEC9, and JEC11 were inoculated in LB broth supplemented with 1% tryptophan (Trp, Sigma-Aldrich) and incubated at 28 °C for 72 h with shaking at 180 rpm. The supernatant was obtained by centrifugation at 1378.21 g for 15 min. For colorimetric determination, cell-free supernatant (200 µL) was mixed with 800 µL of Salkowski reagent and incubated for 30 min at room temperature in the darkness. Absorbance was determined at 530 nm in a UV–visible spectrophotometer (Evolution TM 201, Thermo Fisher Scientific, Cleveland, OH, USA). The identification of IAA in the bacterial supernatants was determined by GC-MS analysis according to Rolón-Cárdenas, et al. [21 (link)]. Ethyl acetate extract was obtained from the supernatant of each bacterial culture and was analyzed by gas chromatography with electron impact mass spectrometry (GC-EIMS, Agilent Technologies, Palo Alto, CA, USA). Quantification of IAA and indole-related compounds were determined using an IAA (Sigma-Aldrich, USA) calibration curve.

The bread VOC profile (sliced bread samples) was assessed according to the protocol previously described in Sanmartin et al., 2018 [47 (link)], sampling the volatile analytes using a 50/30 µm coating thickness SPME (Supelco, St. Louis, MO, USA) and using a gas chromatography-electron impact mass spectrometer (GC-EIMS) (Agilent Technologies Inc., Santa Clara, CA, USA) for their determination.

Bread samples were characterized in terms of VOCs considering separately whole loaf (w) and sliced one (s), the latter without crust. The aromatic profile of bread samples was determined following the protocol previously described by Sanmartin et al. [35 (link)], using a SPME Supelco (50/30 μm coating thickness, St. Louis, MO, USA) for the adsorption of the volatile analytes, followed by gas chromatography-electron impact mass spectrometry (GC-EIMS) (Agilent Technologies Inc., Santa Clara, CA, USA).