Secondary structure of proteins on oil release in aqueous enzymatic extraction of rapeseed oil as affected hydrolysis state

Figures & data

Figure 1. The flow chart for aqueous enzymatic extraction of rapeseed oil.

Table 1. Optimal enzymatic hydrolysis conditions of proteases.

Proteases	Enzyme to substance ratio (%, v/w)	Initial pH	Temperature (°C)	Time (h)
Flavourzyme 1000L	1.5	6.0	50	4.0
Neutrase 1.5MG	1.5	7.0	50	4.0
Protamex	1.5	7.0	50	4.0
Alcalase 2.4L	1.5	8.5	55	4.0
Thermolysin	1.5	8.0	60	4.0

Figure 2. Effects of proteases on free oil and total oil yield.

Figure 3. Protein hydrolysis and oil release state under different enzymatic hydrolysis time (a control; b 1.0 h; c 2.0 h; d 2.5 h; e 3.0 h; f 4.0 h).

Figure 4. Effects of hydrolysis time on protein degree of hydrolysis and free oil yield.

Table 2. The secondary structure content (%) of proteins in different hydrolysis time.

Hydrolysis time (h)	α-helix	β-sheet	β-turn	Random coil
Control	31.3	22.3	27.7	18.7
1.0	25.1	25.4	32.5	17.0
2.0	23.6	25.0	33.1	18.3
2.5	21.9	25.3	33.9	18.9
3.0	20.6	25.8	33.2	20.4
3.5	18.2	27.1	32.6	22.1
4.0	19.2	28.3	32.3	20.2

Figure 5. FTIR spectra of proteins in different hydrolysis time.