Thermogravimetric analysis (TGA)
Since amino acid salts were prepared from an aqueous solution and two commercial amino acid salts were reported to contain water, the water content was determined by TGA, which was then used for an accurate concentration of amino acid in oil. A Model Q50 TGA (TA instruments, New Castle, DE, USA) was used for TGA experiments. The sample (8-10 mg) was weighed onto a platinum sample pan and loaded with the autosampler. The temperature was increased at a rate of 20 °C/min from 25 °C to 250 °C and nitrogen was blown into the sample chamber at a flow rate of 60 ml/min during measurements. Universal Analysis software was used to analyze data. The weight loss was recorded at the temperature where dehydration was completed (typically at 120-180 °C). The experiments were conducted in duplicate, and results are shown in Supplementary Table 1.