Residual sugar was determined by high-performance liquid chromatography, using a Shimadzu chromatograph with a Nucleogel Ion 300 OA column, a LC-9A pump, a CTO-10A oven at 30°C, and a RID-6A refractive index detector. H2SO4 0.008 Ν was used as mobile phase with a flow rate of 0.8 mL/min, and propanol-1 was used as an internal standard. A volume of 0.25 mL of the sample and 0.625 mL of a 1% (v/v) solution of propanol-1 were diluted to 25 mL. Then, 60 μL of the final solution was injected directly to the column. Residual sugar and concentrations were calculated using standard curves.
Volatile fatty acids were determined by high-performance liquid chromatography, using a Jasco chromatograph LC-2000 Plus (Jasco Analytical Instruments, Tokyo, Japan) with a Bio-rad Aminex HPX-87H column (7.8 mm ID × 300 mm, 9 μm particle size), a PU-2089 plus quaternary gradient pump, a Jasco CO-2060 Plus oven at 50°C, a MD-2018 plus photodiode array detector operated at 210 nm, and an autosampler AS 2050 plus. H2SO4 0.008 Ν was used as mobile phase with a flow rate of 0.6 mL/min. The samples were filtered by a membrane filter of 0.45 nm, and all the data were processed with the ChromNav program.
Volatile fatty acids were determined by high-performance liquid chromatography, using a Jasco chromatograph LC-2000 Plus (Jasco Analytical Instruments, Tokyo, Japan) with a Bio-rad Aminex HPX-87H column (7.8 mm ID × 300 mm, 9 μm particle size), a PU-2089 plus quaternary gradient pump, a Jasco CO-2060 Plus oven at 50°C, a MD-2018 plus photodiode array detector operated at 210 nm, and an autosampler AS 2050 plus. H2SO4 0.008 Ν was used as mobile phase with a flow rate of 0.6 mL/min. The samples were filtered by a membrane filter of 0.45 nm, and all the data were processed with the ChromNav program.