The pH of the solution was recorded using a digital pH meter
− 0.10252 × X3 (5)
(Model PHS-3C; CD Instruments, China). Ash, moisture, total sugar and protein contents of the samples were determined according to
where Y is the RPs yield (%, w/w), X1
is the time (min), X2
is the
standard methods (Hou, 2004).