Rice bran is major used as animal feed, especially for horse and aging dogs. Ì´80 % Animal feed. Ì´15 % Cooking rice bran oil. Bakery application: gluten free ...
Effect of Enzymatic Hydrolysis on Antioxidant Activities of Rice Bran Protein Hydrolysates C. URAIPONG, J. ZHAO* School of Chemical Engineering, Food Science and Technology, The University of New South Wales, NSW 2052
AIM
ANTIOXIDATIVE ACTIVITIES OF HYDROLYSATES
To use enzymatic digestion for revealing rice bran bioactive peptides and their anti-oxidative properties Objectives • To investigate enzymatic condition for hydrolysis of protein • To screen and study anti-oxidative activities of protein hydrolysates
BACKGROUND • The world production of milled rice in 2013 was 487 million metric tonnes. It resulted in 48 million tonnes of rice bran.
• Rice bran is major used as animal feed, especially for horse and aging dogs.
• The activities of protamax-assisted albumin and glutenin slightly decreased at 240 min incubation time, though the highest degree of hydrolysis was obtained (Figure 2 and 3), which is concurrent to the study of Bamda et al.3 • Prolamin hydrolystes presented the lowest ABTS and DPPH scavenging effect. This is due to the lower solubility of prolamin in phosphate buffer leading to less diffusivity to manifest scavenging capacity. • The scavenging ability of flavourzyme-assisted glutenin, which is alkaline soluble protein, was significantly lower than other three proteases. This suggests that the optimal condition of enzyme hydrolysis may play important role in protein digestion and antioxidant activities. • Alcalase is the most appropriated protease to produce antioxidative rice bran protein hydrolysates 90 90
Globulin
75 60 Neutrase
45
30 15
Flavourzyme
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Glutenin
75
ABTS inhibition (%)
60 45
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100 200 Hydrolysis time (min)
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Hydrolysis time (min
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Prolamin Degree of hydrolysis (%)
Degree of hydrolysis (%)
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100 200 Hydrolysis time (min)
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• Alkaline proteases hydrolysis was related to the previous study by Zhao et al.2
15 10
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Globulin
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60
5
5
Albumin
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30
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100 200 Hydrolysis time (min)
60
60
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Glutenin
0
Figure 2: ABTS scavenging activities of fractionated RBP.
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Hydrolysis time (min)
Figure 1: Proteolytic hydrolysis of fractionated RBP (Alcalase 2.4L, Protamax, Neutrase 0.8L and Flavourzyme 1000L).
CONCLUSION • Rice bran protein hydrolysates could potential serve as a good source of desirable peptides to be as natural additive with antioxidant properties. • Albumin and glutenin were most easily hydrolysed by the alkaline and neutral enzymes, while globulin and prolamin were the more resistant to enzymatic hydrolysis. • The high levels of DPPH and ABTS radical scavenging activities of protein hydrolysates are associated with a high degree of hydrolysis, which should be equal or less than 25% References 1. Chanput W, Theerakulkait C, and Nakai S ( 2009) J Cereal Sci 49: 422-428 2. Zhao Q, Xiong H, Selomulya C, Chen XD, Zhong H, Wang S, Sun W and Zhou Q (2012) Food Chem. 134: 1360-1367 3. Bamdad F , Wu J and Chen L. (2011) J Cereal Sci 54, 20-2
DPPH inhibition (%)
0
• The highest hydrolytic efficiency was observed in protamaxtreated albumin at Neutrase 24.6%, and the lowest Protamax Alcalase rate is 6.1% from Flavourzyme flavourzyme-treated 100 200 300 prolamin Hydrolysis time (min)
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300
Glutenin
Prolamin
50
Neutrase Protamax
DPPH inhibition (%)
15
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DPPH inhibition(%)
20
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45
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DPPH inhibition (%)
Degree of hydrolysis (%)
Degree of hydrolysis (%)
25
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30 Albumin
300
Prolamin
75
30
ENZYMATIC HYDROLYSIS Globulin
100 200 Hydrolysis time (min)
90
15
30
45
0
ABTS inhibition (%)
• There are on-going attempts to add value to rice bran, and rice bran protein should be considered when investigating the potential for adding value • Enzymatic rice bran protein hydrolysis is challenging to promote the health benefit of rice bran protein (RBP) hydrolysates without formation of toxic by-products or destruction of amino acid1
60
Alcalase
15
Dietary supplements: oil and fibre
75
Protamax 30
Bakery application: gluten free mueslis
ABTS inhibition (%)
̴15 % Cooking rice bran oil
ABTS inhibition (%)
̴80 % Animal feed
Albumin
40 30 20 10
40
Alcalase Flavourzyme
30 20 10
0 0
100 200 Hydrolysis time (min)
300
0 0
100 200 Hydrolysis time (min)
300
Figure 3: DPPH scavenging activities of fractionated RBP
FUTURE WORKS • To determine other biological activities: in-vitro antihypertensive activity and in-vitro anti-diabetic activity • To isolate and identify biological active rice bran peptides • To apply the rice bran protein hydrolysates as natural additive on food products
ACKNOWLEDGEMENT The authors greatfuly acknowledge the financial support provided by Rural Industries Research and Development Corporation (RIRDC). Special thanks to SunRice Australia® for sponsoring rice bran samples and Novozymes Australia® for proteases.
