Background World rice production in year 2007 was about 645 MT. 10% - PDF document

21/07/54 Oral Presentation CRDC 5 Effect of stabilization methods on antioxidant activity in rice bran By Patiwit Loypimai Food Science & Technology Faculty of Science & Technology, Bansomdejchaopraya Rajabhat University Background � World rice production in year 2007 was about 645 MT. � 10% is a by product from the rice milling (60 MT) � 10% is a by product from the rice milling (60 MT). � Rice bran (RB) is a rich source of fat, protein, vitamin & nutrients essential of life. 1

21/07/54 Oral Presentation CRDC 5 Saturated Fatty Acid : Monounsaturated Fatty Acid : Polyunsaturated Fatty Acid Equal 10 : 10-15 : < 10 � RB has great potential as a supplementary source of many valuable substances, such as Vitamin E, γ -Oryzanol Nutraceuticals Nutraceuticals ppm ppm Phytosterols 2,230-4,400 γ -Oryzanol 2,200-3,000 Tocopherols Tocotrienols Tocopherols, Tocotrienols 210-440 210 440 Polyphenols 305-309 Squalene 4,000 2

21/07/54 Oral Presentation CRDC 5 Drawback of RB RB Rancidity Oxidative Hydrolytic (lipase) Enzymatic (lipoxygenase) Non Enzymatic (Autoxidation) 3

21/07/54 Oral Presentation CRDC 5 � Therefore, immediately after milling process, inactivation enzyme and inhibition the formation of FFA are necessary. � The process in doing so is called “ stabilization” Stabilization methods Such as � Steaming � Extrusion � Microwave heating Disadvantage � Thermodegradation � Thermodegradation � Substantial moisture removal 4

21/07/54 Oral Presentation CRDC 5 Alternative method Oh i h ti (OHM) Ohmic heating (OHM) OHM occurs when alternating current is passed through a food sample, and heat is generated by virtue of h t i t d b i t f sample’s electrical resistance (Lakkakula et al., 2004) Advantages � Rapid and uniform treatment � Preventing overcooking (minimal heat damages) � Environmentally friendly � Reduced maintenance costs Potential future applications exist for OHM, including its use in blanching, evaporation, dehydration, fermentation, and extraction (FAD, 2001). 5

21/07/54 Oral Presentation CRDC 5 The objective : To investigate the effect of different stabilization g methods on � antioxidant activity in rice bran � percent yield of the extracted oil Materials and Methods Materials RB sample RB l Sieved with 20 mesh (remove broken pieces and husks) RB characteristics Stabilizations 8 6

21/07/54 Oral Presentation CRDC 5 1. Microwave heating 2. Steaming Rice Bran Rice Bran MC adjusted (21%) MC adjusted (21%) 2450 MHz 900 W, 3 min Autoclave (105 o C, 15 min) RB RB Cooling (25 ° C) Hot air oven (60 º C, MC~8%) Cooling (25 ° C) 13 3.Ohmic heating Rice Bran MC adjusted (30%) Electrical field strength (E) (150 Vcm -1 ) 60 Hz Data logger controller RB Cooling (25 ° C ) Hot air oven (60 º C, MC~8%) 7

21/07/54 Oral Presentation CRDC 5 Stabilized RB and raw RB Polyethylene zip bag Antioxidant activities % Oil yield DPPH radical scavenging Lipid peroxidation Total antioxidant capacity Results 8

21/07/54 Oral Presentation CRDC 5 1. Rice bran characteristics 1. RB particles 2. Chemical compositions Table 1. The size distribution of raw rice bran particles. RB size % Mesh Mesh um um < 20 > 750 3.75 20 - 35 750 - 500 8.50 35 - 50 500 - 300 50.85 50 - 70 300 - 212 33.15 > 70 < 212 3.75 9

21/07/54 Oral Presentation CRDC 5 Table 2. Chemical compositions of raw rice bran. g/ 100 g RB Chemical compositions Moisture content M i t t t 8.16 ± 0.06 8 16 0 06 Fat 12.38 ± 0.15 Protein 12.76 ± 0.21 Ash 11.57 ± 0.11 Carbohydrate 55.13 ± 0.20 2. Effect of stabilization methods (SM) on antioxidant activities 10

21/07/54 Oral Presentation CRDC 5 Table 3. Effect of SMs on antioxidant activity by DPPH • scavenging & lipid peroxidation assay. Stabilization methods DPPH radical Lipid peroxidation IC 50 (mg/ml) IC 50 (mg/ml) Raw rice bran 160.1 d 212.4 d (No heating) Steaming 100.2 c 138.2 c Microwave heating 79.1 b 115.7 b Ohmic heating 65.3 a 81.6 a % CV 7.10 4.81 a, b means within a column with different letters are different ( p< 0.05) %CV : %Coefficient of variance (n=3) 21 3 2.68 2.47 2.26 2.5 weight) 2 2 Gallic eq. mg/ g (dry w 1.5 1.5 1 0.5 0 0 Raw rice bran Steaming Microwave Ohmic Fig 1. Effect of SM on antioxidant activity by total antioxidant capacity (Gallic acid quivalent) 22 11

21/07/54 Oral Presentation CRDC 5 3. Effect of SMs on %yield of the extracted RB oil Table 4. Effect of SMs on %yield of the oil. Oil yield Stabilization methods (%) 12.8 c Raw rice bran (No heating) 15.8 b Steaming 16.1 b Microwave heating 17.4 a a Ohmic heating 5.21 % CV a, b means within a column with different letters are different ( p< 0.05) %CV : %Coefficient of variance (n=3). 24 12

21/07/54 Oral Presentation CRDC 5 Conclusion � Stabilized rice bran with OHM is an effective stabilization method. � To improve the stability and preserve the antioxidant activity � OHM obtained the highest percent yield of the extracted � OHM obtained the highest percent yield of the extracted RB oil. 25 26 13