P-STARCH-11. Effect of Extrusion Parameters on Starch Fractions and Fhysicochemical Properties of Job s Tear (Coix lacryma jobi L.) Flour.

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1 P-STARCH-11 Effect of Extrusion Parameters on Starch Fractions and Fhysicochemical Properties of Job s Tear (Coix lacryma jobi L.) Flour. Jiraporn Chaisiricharoenkul and Sunanta Tongta School of Food Technology, Institute of Agricultural Technology, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand The effect of extrusion parameters, a feed moisture of 20%,35%,50% and a barrel temperature of 90,120,150 C with a screw speed of 150 rpm on the starch fractions and physicochemical properties of white husk job s tear flour was investigated. As compared to the raw job s tear flour, the extrusion parameters had an influence on lowering slowly digested starch fraction, increasing water solubility index, but did not significantly affected the resistant starch fraction. At feed moisture of 20% with the barrel temperature of 120 and 150 C, the water absorption index of extrudates was significantly lower than that of the other conditions. An increase in feed moisture or a decrease in barrel temperature lowered the degree of gelatinization of job s tear extrudates. The pasting profile of all extrudates, as determined by Rapidly Visco Analyzer, was decreased, as compared to the raw flour, but they were different depending on extrusion conditions. The extrusion processing destroys the semi-crystalline structure of job s tear flour as investigated by X-ray diffraction. Keywords: Job s tear, extrusion, starch fractions, physicochemical property Introduction Job s tear, scientifically named Coix lacryma jobi L., is a grass crop in Gramineae. Job s tear grain is used in soups and beverages, and as flour or whole grain. It is popular use in Chinese traditional medicine (Tseng,et al, 2005). Recently, several studies reported that job s tear grains possessed antitumor activity and anti-allergic and hypolipidomic properties (Chang,et al, 2003). Although job s tear grain is now used in a higher extent due to its nutritional and health values but it is not processed to be obtained a diversity of products (Kang, Kim and Hahm, 2001) Extrusion cooking is one of popular technology in food processing. It is a high temperature short time process, and used worldwide for processing a number of food products (Singh, et al., 2007). The extrusion of starchy foods results in gelatinization, partial or complete destruction of the crystalline structure and molecular fragmentation of starch polymers, as well as protein denaturation, and formation of complexes between starch and lipids and between protein and lipids As the extrusion process involves both thermal and mechanical shearing, it has been shown that it is possible to manufacture new food products such as cereal-based snacks, modified starches, animal feeds and beverages (Hagenimana, et al., 2006). Extrusion variables and composition of feed material significantly affect extrusion parameters and product properties. (Gujral, et al.,2001). Therefore, the objective of this study was to investigate the extrusion variables, feed moisture and barrel temperature on starch digestion and physicochemical properties of Job s tear flour. 183

2 Material and Method Material White husk Job s tear was obtained from Yongsawadpudpol Wangsapund, Co.,Ltd, Loei, Thailand. All chemical reagents were of analytical reagent grade. The porcine pancreatic (P-1750), amyloglucosidase (AMG, A-7095) and PGO enzyme (P-7119) were purchased from Sigma-Aldrich Chemicals, Inc. (St. Louis, MO, USA). Sample preparation White husk Job s tear was milled using dry milling method and then passed through a 60 mesh sieve. Extrusion processing A co-rotating twin-screw extruder with intermeshing screws (APV MPF 19:25, APV Baker, Inc., Grand Rapid, MI, USA), L/D ratio of 25:1, with a circular die diameter of 3 mm was operated. The barrel temperatures profile was set at low (40/60/80/90 o C), medium (60/80/100/120 o C) and high (90/110/130/150 o C) condition. The feed moistures were 20, 35 and 50 %. The screw speed rate was set at 150 rpm. After extrusion, extrudates were collected and dried in hot air oven at 40 o C for 21 h and stored at -40 o C for further analysis. The experiment was conducted in duplicate. In vitro starch digestion Rapidly digested starch (RDS), slowly digested starch (SDS) and resistant starch (RS) fractions were determined according to Englyst, et al. (1992 and 1999) with slightly modification. The sample, guar gum and glass ball were added into a centrifuge tube. The 0.1 M sodium acetate buffer (ph 5.2) and enzyme mixture containing porcine pancreatin and AMG were added and place in a shaking water bath. After 20 and 120 min, the mixture digested was removed into absolute ethanol and designated as G20 and G120 respectively. After removal of the aliquot at 120 min, the tube was placed in a boiling water bath for inactivate enzyme. Then, 7 M KOH was added and shaked in ice shaking. The aliquot was removed and added into 1 M acetic acid. AMG solution was added and it was placed in a shaking water bath (50 O C). The tube was heated in a boiling water bath and then absolute ethanol was added. This was assigned as the total glucose (TG). The G20, G120 and TG were centrifuged and then the glucose was determined using PGO enzyme reagent. The RDS, SDS and RS fraction was calculated as follows: RDS= G20 x 0.9, SDS = (G120 G20) x 0.9 and RS = (TG G120) x 0.9. Degree of starch gelatinization (DG) The degree of gelatinization is determined according to Chiang and Johnson (1977) as the weight ratio of gelatinized starch to total gelatinized starch. The total gelatinized flour was prepared by autoclaving extrudate suspension (2%, w/w) at 121 C for 1 h. Then, it was mixed with methonal, filtered and dried. The samples were milled, and then it was solubilized with alkali reagent, digested with glucoamylase and stopped enzyme reaction by trichloroacetic acid. The released glucose reacted with o-toluidine was quantified by measuring the absorbance at 630 nm. Water absorption index (WAI) and water solubility index (WSI) WAI and WSI were determined using the modified method of Anderson (1969 and 1982). The powder sample and distilled water were added into the centrifuge tube with screw cap and mix well. It was heated at 30 o C for 30 min in a shaking water bath and then centrifuged. The clear supernatant was removed into a preweighed dish and dried at 105 o C. Swollen sediment and dried supernatant were weighed to determine the WAI and WSI as follows: WAI = [weight of sediment (g)/ weight of dry sample solid in original sample (g)], WSI (%) = [weight of dissolveed solid in supernatant (g)/weight of dry sample solid in original sample (g)] x

3 Pasting property The pasting property of the sample were measured using a Rapid Visco Analyzer (RVA). The sample of 2.5 g (dry basis) was weighed into a RVA canister and the distilled water was added to obtain moisture content of 14%. The time-temperature profile was programmed using as extrusion with no alcohol profile which was: holding tempeature at 25 o C for 6 min, operating at 960 rpm for 10 second and decreased speed to 160 rpm, heating to 95 o C in 5 min, holding for 6.5 min at 95 o C, cooling to 25 o C in 6 min and holding for 9 min at 25 o C. X-ray diffraction X-ray powder diffraction analysis was performed using X-ray diffractometer using 1.54 Å Cu K radiation. The samples were exposed to the X-ray beam with X-ray generator running at 40kV and 40mA. The scanning regions of Bragg s angle (2 ) were Statistical analysis A factorial experiment in completely randomized design (CRD) was designed. Analysis of variance (ANOVA) was performed using the SAS for windows v6.12. The differences among mean values were established using Duncan s multiple-range test (DMRT) at 95% significance level. Result and Discussion Effect of extrusion on starch fractions The effect of extrusion cooking on starch fractions of job s tear flour was shown in Table 1. Extrusion parameters, feed moisture and barrel temperature, were affected on the RDS and SDS fraction but not on RS fraction when compared to the native flour. This process had an influence on lowering SDS fraction and increasing RDS fraction. Due to physical disruption of the organized granular structure. Extrusion cooking is responsible for gelatinization and degradation of starch and also for changing the extent of molecular association between components such as the amylose lipid complex (Hagenimana, et.al, 2006). Both of feed moisture and barrel temperature did not affect on starch fractions. Effect of extrusion on degree of gelatinization The degree of gelatinization (DG) of job s tear flour extrudates range from 49 to 91 % (Table 2). The DG of extruded job s tear flour was higher with increasing barrel temperature but decreased with increasing feed moisture. Decreasing feed moisture resulted in higher mechanical degradation, leading to a progressive change of DG where the form of gelatinized like transformed to dextrinized like. (Owusu, et al.,1993) Effect of extrusion on water absorption index and water solubility index The water absorption index (WAI) and water solubility index (WSI) were shown in Table 3. The WAI was increased with higher temperature and it depended on feed moisture. The WAI of job s tear extrudate at feed moisture of 35 and 50% was higher than that of the native flour. At feed moisture of 20%, the WAI extrudates was significantly lower than that of the other extrusion conditions. Since water acted plasticizer during extrusion cooking, the degradation of starch granules was decreased. This results in an increased capacity of water absorption when compared to the raw material (Hagenimana, et.al, 2006). At feed moisture of 50%, as the barrel temperature was increased to 150 C, the WAI of extrudates was lower than that of feed moisture of 35 %. Mercier and Feillet (1975) reported that the WAI of wheat, corn, and rice starch was increased as the extrusion temperature was increased to 180 C but it decreased afterword. The WSI of all extrudates was higher than that of the native flour. The highest feed moisture and the highest barrel temperatures showed the lowest values of WSI because this condition was highest mechanical degradation. The WSI depended on the amount of solubles substances which could be greater due to the degradation of starch and other components (Guha, et al 1997). 185

4 Effect of extrusion on pasting property Figure1 showed pasting property of job s tear native flour and its extrudates. The pasting profile of all extrudates was decreased as compared to the native flour, but they were difference depending on extrusion conditions. At the feed moisture of 20%, the extrudates showed no viscosity profile which was similar to that of water. At the feed moisture of 35 and 50 % of the extrudates with barrel temperature of 120 and 150 o C, the extrudates showed viscosity profile contaning peak viscosity at the temperature of o C. The peak viscosity of extrudates at the feed moisture of 35 and 50 % was increased with increasing barrel temperature. The paste viscosity of the extrudates depended on the extent of degree of gelatinization and the extent of their molecular breakdown. (Gutkoski and Dash, 1999) Table 1 Starch fractions of job s tear flour and its extrudates. Extrusion conditions Feed moisture Last zone of barrel RDS (%) SDS (%) RS (%) content (%) Temperature ( o C) native flour 13.99±0.25 c* 45.07±1.74 a 40.98±1.02 ab ±0.32 ab 33.49±1.43 bcd 40.59±1.12 ab ±0.29 ab 33.43±1.63 bcd 40.86±1.93 ab ±0.26 b 35.54±1.06 b 39.65±1.31 ab ±0.64 ab 31.07±1.78 d 42.63±2.42 a ±1.78 a 31.74±1.76 cd 41.60±0.02 ab ±0.05 ab 34.86±0.80 bc 38.75±0.76 b ±0.22 ab 34.53±2.40 bcd 39.94±2.62 ab ±0.38 ab 34.08±0.44 bcd 39.79±0.82 ab * Means with different lettrs within a column are significantly different (p<0.05) 1 RDS: rapidly digestible starch, SDS: slowly digestible starch and RS: resistant starch Table 2 Degree of gelatinization of job s tear flour extrudates. Extrusion conditions Last zone of barrel Degree of gelatinization (%) Feed moisture content (%) Temperature ( o C) ±0.89 ab* ±2.63 a ±1.91 g ±1.99 cd ±0.34 bc ±0.95 f ±1.52 e ±3.56 d * Means with different letters within a column are significantly different (p<0.05) Effect of extrusion on X-ray diffraction Figure 2 showed X-ray diffraction of job s tear flour and its extrudates. The job s tear flour displayed an A-type X-ray diffraction pattern (Figure2i). The extrusion cooking destroys the semi-crystalline structure of job s tear flour. The extrudates with feed moisture of 35% and barrel temperature of 90 o C illustrated the semi-crystalline structure (Figure 2c). At higher temperatures, the structure is completely destroyed, leading to a typical X-ray pattern of amorphous state similar to the report of Charbonniere et al. (1973). 186

5 Table 3 WAI and WSI of job s tear flour and its extrudates extrudates. Extrusion conditions Last zone of barrel Feed moisture content (%) Temperature (oc) native flour WAI (g/g) WSI (%) 2.27±0.04ef* 9.08±0.12g ±0.06f 62.69±0.39b ±0.11f 66.42±1.30a ±0.03 de 16.96±1.86d ±0.00b 22.15±1.03c ±0.14a 11.61±0.09f ±0.29 d 18.94±0.16d ±1.38c 14.55±0.33e 8.24±0.13b 11.88±1.02f 150 Means with different letters within a column are significantly different (p<0.05) WAI: water absorption index and WSI: water solubility index * Figure 1 Pasting property of job s tear flour and its extrudates. (LT: low barrel temperature, MT: Medium barrel temperature and HT: high barrel temperature) Figure 2 X-ray diffraction of job s tear flour and its extrudates. (Feed moisture-barrel temperature; a=20-120, b=20-150, c=35-90, d=35-120, e=35-150, f=50-90, g=50-120, h=50150 and i=native) &%

6 Conclusion Extrusion conditions on the starch fractions and physicochemical properties of job s tear flour. RDS and SDS fraction were affected by extrusion conditions, except RS fraction. WAI, WSI and pasting properties depended on feed moisture contents and barrel temperature. This extrusion condition destroys the semi-crystalline structure of job s tear flour. Acknowledgement This work was supported by Suranaree University of Technology and Thailand Research Fundemental-Master Research Grants. Referrences Chang, H. C., Huang, Y.C. and Hung, W. C. (2003). Antiproliferative and Chemopreventive effect of adlay seed on lung cancer in vitro and in vivo. J. Agric. Food Chem. 51: Charbonniere, R.; Duprat, F. and Guilbot, A., Changes in Various Starches by Extrusion- Cooking Processing. II. Physical Structure of Extruded Products. (Abstr.) Cereal Science Today, Vol. 18, p. 286 (1973). Englyst, H.N., Kingman, S.M. and Cummings, J.H.(1992). Classification and measurement of nutritionally important starch fractions. Euro. J. Clin. Nutr.46: Guha, M., Ali, S. Z. and Bhattacharya, S.(1997). Twin-screw extrusion of rice flour without a die: effect of barrel temperature and screw speed on extrusion and extrudate characteristics. J. Food Engi. 32: Gujral, H. S., Singh, N. and Singh, B. (2001). Extrusion behaviour of grits from flint and sweet corn. Food Chem. 74 : Gutkoski, L.C. and Dash, A.A. EL.(1999). Effect of extrusion process variables on physical and chemical properties of extruded oat products. Plant Foods for Human Nutrition 54: Hagenimana, A., Ding, X. and Fang, T.(2006). Evaluation of rice flour modified by extrusion cooking J. Cereal Sci.43: Mercier, C. and Feillet, P. (1975) Modification of carbohydrate components by extrusion cooking of cereal products. Cereal Chem 52: Owusu, A.J., van de Voort, F.R. and Stanley, D.W. (1993). Physicochemical changes in corn starch as a function of extrusion variables. Cereal Chem., 60: Singh, B., Sekhon, K.S. and Singh, N. (2007). Effects of moisture, temperature and level of pea grits on extrusion behaviour and product characteristics of rice. Food Chem. 100: Tseng, Y.H, Yang, J.H., Chang,H.L. Lee, Y.L. and Mau, J.L.(2005). Antioxidant properties of methanolic extracts from monascal adlay. Food Chem.97:

Project Title: Development of GEM line starch to improve nutritional value and biofuel production

Project Title: Development of GEM line starch to improve nutritional value and biofuel production Prepared by Jay-lin Jane and Hanyu Yangcheng, Department of Food Science and Human Nutrition, Iowa State