Materials and methods Sample preparation and division In this study
The NIR spectra were collected with the reflectance mode (log 1/R) using an Antaris™ II FT-NIR spectrometer (Thermo Scientific Co., USA) equipped with an integrating sphere. Each spectrum was the average of 16 scanning spectra. The NIR measurements were performed within the region 10,000–4000 cm–1, and the data were acquired with a spectral Puromycin of 3.856 cm–1, which resulted in 1557 variables. When spectra collecting, about 6 g of fermented sample without pretreatment as a sample, which was put in a telophase standard sample cup particularly designed by Thermo Scientific Co. Each sample was collected three times at different positions, and the three spectra were averaged to provide a mean spectrum for each sample was recorded as the original spectrum of the sample. In NIR spectra collection, near infrared spectrometer was sensitive to the change of outer environment conditions such as temperature and humidity. Therefore, the temperature was kept around 25 °C and at a steady humidity level in the laboratory.