Acidity vs time, during the esterification stage (E-1). Esterification alcohol:
ethanol; catalyst: p-toluene sulphonic acid. Soybean oil; alcohol/oil molar ratio:
16:1, 60 C, catalyst concentration 0.66% v/v. Beef Tallow: alcohol/oil molar ratio
11:1, 60 C, catalyst concentration 0.56% v/v.