Americn-Eursin J. Agric. & Environ. Sci., (3): 470-474, 2011 ISSN 1818-6769 IDOSI Publictions, 2011 Effect of Whitener Type nd Pddy Moisture Content on Rice Grin Dmge During Milling Process 1 2 Seed Firouzi nd Mohmmd Rez Alizdeh 1 Deprtment of Agronomy, Islmic Azd University, Rsht Brnch, Rsht, Irn 2 Deprtment of Agriculturl Engineering, Rice Reserch Institute of Irn, Rsht, Irn Abstrct: Rice (Oryz stiv L.) grin dmge in common rice mills of Guiln province of Irn ws evluted. A fctoril bsed on rndomized completely design with three levels of moisture content of 8-9, -11 nd 12-13% (w.b.) nd three types of universl rice whitener mchines, brsive type whitener (AW), blde-type whitener (BW) nd frictionl-type bldeless whitener (FBLW) ws conducted in triplictes. A typicl rice vriety in Guiln s pddy cultivted re nmely Hshemi ws considered. The obtined results indicted tht the effect of moisture level nd whitener type on the broken rice ws significnt (p<0.01). The lowest percentge of broken white rice (.14%) took plce in the AW with moisture level of 8-9%, wheres the highest percentge of broken rice (17.19%) ws defined in FBLW with 12-13% moisture. The min effect of pddy moisture level nd the whitener type on the crcked grins ws significnt (p<0.05). So tht, the lowest percentges of crcked grins of 3.29% nd 2.84% were mesured in AW nd pddy moisture content of 8-9%, respectively. It seems tht using brsive type whitener with pddy moisture level of 8-9% is the most proper choice for milling of Hshemi vriety. Key words: Rice whitener Broken rice Crcked grins Brekge Pddy moisture Hshemi INTRODUCTION whiteners re divided into two min groups including frictionl nd brsive types [2, 8-11]. In frictionl-type Rice (Oryz stiv L.) s stple food of two third of whiteners, brn removl is performed by rubbing of pddy world popultions, hs key role to supply mnkind on brown rice kernels in milling chmber. Use of blde on required clories. About 40 to 80% of required energy of blde-type frictionl whiteners (Engleberg whiteners) Asin people is provided through rice crop [1]. In Irn, intensifies the mechnicl stresses in milling chmber; 75% of rice is cultivted in northern prt of the country consequently, more crcked rice would pper. However, nd rice hs been counted s min crop. Rice production in frictionl bldeless type whiteners, moving upper prt record hs incresing trends; in 1980 nd 2007, the nnul of milling chmber with respect to perforted screen frme production rte hs been reported from 1.3 million to 3.5 hs replced blde. Also in brsive ones, milling process million tons, respectively [2]. is performed by brsion stone over brown rice grins. Milling is the finl step in rice post-hrvest Thus, it is necessry to seprte brown rice kernels from processing. It includes pre-clening, destoning, husking, unhulled pddies. This procedure is conducted by pddy brn removl, clening nd grding. The type of rice mills seprtors [1, 7, 12]. Frmers in northern Irn, usully nd the method of opertions significntly ffect on utilize Englebreg rice whiteners in which rice brekge is recovery of rice [3]. The quntity of interest in efficiency very high, therefore ltertion of mills structure should be judgment of ny pddy milling opertion is the mount of the min priority to investigte on rice crck. However, the unbroken kernels remining [4]. Among ll preformed key question rised for the replcements would be the mill opertions for pddy milling, brn removl is mjor step of structure in wht extent will be efficient? According to the opertion. During this process, rice kernels re subjected conducted studies during rice milling opertions, few to intensive mechnicl nd therml stresses which might reserches hve focused on comprison of milling dmge or brek some of the kernels. The process of brn systems nd most of them were bsed on effect of removl is clled whitening or perling [5-8]. Rice mechnicl prmeters nd vrietl fctors on the Corresponding Author: Seed Firouzi, Deprtment of Agronomy, Islmic Azd University, Rsht Brnch, Rsht, Irn. Tel: +98-1313462235, Fx: +98-1313462255, E-mil: firoozi@iursht.c.ir. 470
Am-Eurs. J. Agric. & Environ. Sci., (3): 470-474, 2011 performnce of ech single mchine. It hs been reported tht modern mills using rubber roll huller combined with brsive nd frictionl whiteners yield n verge overll increse in totl rice recovery of 2.5% over disc huller type rice mill nd 6.6% over Engleberg mills [11, 13, 14]. Afzlini et l. [15] hve demonstrted tht the optimum moisture level of pddy in milling opertion for Khmfirouzi vriety ws 12-14% (w.b.), using three brsive whiteners in series nd one friction whitener s polisher resulted in the lest rice brekge. This method ws identified s the best choice for the rice milling opertion in the province of Frs, Irn. It hs been reported tht the brekge of long pddy vriety, nmely Trom in lbortory brsive whitener ws.23% less thn tht of frictionl whitener [16]. The recent investigtion conducted on performnce of frictionl nd brsive whitener showed tht the verge broken rice in brsive whitener ws significntly less thn tht of blde-type whitener [16, 17]. The highest broken rice ws resulted with moisture level of 14%. It hs lso been concluded tht brsive milling system cused less broken compred to milling systems include rubber roll huller nd blde whitener s well s system with blde husker nd blde whitener [17]. The overview of reports revels tht some of the studies were performed on lbortory scle nd some others were on locl pddy vrieties nd lso the role of grin moisture level hs not been considered in ll reserches. Therefore, the objective of present study ws to exmine the effects of whitener type nd pddy moisture level on broken nd crcked kernels of common long-grin vriety nmely Hshemi during milling process. MATERIALS AND METHODS The present study ws crried out in order to compre three common types of rice whiteners, nmely blde-type whitener (BW), frictionl bldeless whitener (FBLW) nd brsive type whitener (AW) in rice mills of Guiln, Irn. In order to eliminte ny error nd lso to unify the experimentl mteril, the pddy ws bought from one frm for lessening the effects of gronomicl nd environmentl effects. The experiments were crried out in fctoril bsed on rndomized completely design in triplictes [18]. According to methodologies stted by other reserchers; specil ttention ws pid for the uniformity nd smpling [19, 20]. For evlution of the effect of pddy moisture, three moisture levels; 8-9, -11 nd 12-13% moisture (w.b.) were considered. These moisture levels were selected ccording to rice moisture limit in Guiln s mills. For ech experimentl run, 40 kg of pddy ws prepred for milling. The moisture level of pddy ws mesured by the mens of grin moisture meter (GMK-303 RS Model, Kore). In order to obtin the desired moisture level, the pddy smples were dried in btch type dryer (HASAN- MANSOR Mnufcturing Co. Ltd. Irn). The drying process ws performed t constnt ir temperture of 43 ºC until the desired moisture level ws obtined [21, 22]. For the uniformity of dried pddy, the depth of pddy in the dryer bin ws reduced to 20 cm [23]. For prevention of moisture bsorption, the dried pddy ws kept in thick plstic bgs. For husking process, the pddy smples were loded into rubber-roll husker (Iseki Mnufcturing Co. Ltd. Jpn). It should be noted tht in BW nd FBLW the outlet of pddy husker which is the mixture of pddy nd brown rice ws fed to the whitener mchine. However in AW it is necessry to seprte pddy grin from brown rice using pddy seprtor which is locted fter the pddy husker. In ech experimentl run, five smples of 200g of white rice were collected from the outlet of the whitener. The broken rice ws seprted from hed rice by mens of rotting sieve (TRG058 Model, SATAKE Test Rice Grder, Jpn). A kernel hving equls to or more thn 75% intct ws considered s whole kernel [, 13, 20]. The percentge of broken kernels ws clculted from the mss rtio of broken milled rice to the totl milled rice. In order to determine the percentge of crcked milled rice, 50 complete kernels from ech tretment were rndomly smpled nd put over n opticl crck tester nd the number of crcked kernels ws counted by mens of mgnifier nd its number ws multiplied by two. The obtined results were subjected to sttisticl nlysis pplying fctoril tril bsed on rndomized completely design (RCD) with 9 tretments nd three replictes. Since the dt of broken kernels were non ccountble percentge mounts, so the trnsformtion of Arc Sin X ws used for normliztion of them nd trnsformtion of x + 0.5 ws used for normliztion of ccountble percentge mounts of crcked kernels [2, 11, 14, 18]. RESULTS AND DISCUSSION Anlysis of vrince of the effects of whitener type nd pddy moisture level on percentge of broken nd crcked milled rice is shown in Tble 1. According to obtined results, the whitener type nd pddy moisture level hd significnt effect on the broken grins (p<0.01) nd crcked grins (p<0.05). Also, the interction effect of whitener type nd moisture level ws significnt (p<0.01) on broken milled rice. 471
Am-Eurs. J. Agric. & Environ. Sci., (3): 470-474, 2011 Tble 1: Results of nlysis of vrince (ANOVA) for broken brown rice nd crcked kernel Men Squre ------------------------------------------------------------------------------- Source of vritions Degree of freedom Broken rice Crcked rice Type of whitener 2 0.00359 * 0.44 Pddy moisture level 2 0.00849 * 0.608 Type of whitener Moisture level 4 0.00207 ns 0.049 Error 18 0.00034 0.1 Totl 26 c.v. 4.9% 16.25% * significnt t =5% significnt t =1% ns non significnt difference 20 20 Amount of rice brekge (%) 15 16.09() 14.78(b) 13.12(b) Amount of rice brekge (%) 15 12.60 () 14.42 (b) 16.96 (c) B W FBLW A W 8-9 % -11 % 12-13 % Type of whitener Moisture level (w.b.) Fig. 1: Effect of whitener type on rice kernel brekge Fig. 2: Effect of pddy moisture level on rice kernel brekge Fig. 1 illustrtes the lowest broken milled rice (13.12%) which ws obtined with AW whitener. obstructions like blde on grin movement route; Menwhile, the mount of broken milled rice in FBLW then the mount of rice brekge is reduced. The (14.78%) ws less thn BW (16.09%). However there ws obtined results were in good greements with the no significnt difference between the FBLW nd BW. reported dt by Afzlini et l. [5]. Their investigtion Also there ws no significnt difference between the AW showed tht using three brsive whiteners in nd FBLW in broken milled rice. This could be ttributed series nd one friction whitener s polisher to different type nd severity of stresses on rice kernels resulted in minimum mount of the rice brekge for in milling chmber. In BW, the pressure exerted by the the locl vriety of Kmfirouzi. Another conducted blde cused more pressure on milling chmber nd more experiment indicted tht the verge broken rice in friction between brown rice nd pddies. Obstruction of brsive whitener ws significntly less thn the grins movement in whitener by blde nd the contct of blde-type whitener [12]. grins with them resulted in more mechnicl stresses. In The mximum (16.96%) nd the minimum percentges FBLW, the horizontl movement of upper cp towrd to (12.60%) of the broken milled rice took plce when the the perforted screen continer hs been replced by pddy moisture level ws round 12-13% nd 8-9% (w.b.), blde. It seems tht this ction tempers the pressures on respectively (Fig. 2). This my be due to low grin grins during milling opertion nd consequently hrdness t high pddy moisture level. It seems to be due decreses the grin brekge. In brsive whitener (AW), to high brittleness of the grins t low moisture content; the grins re whitened through rubbing on roller grinder the kernel brekge most probbly increse t moisture stone. Therefore, regrding the toughness of grinder level lower thn 8-9%. However, more investigtion my roller, less pressure is required in milling chmber thn be required to define the exct cuse of the kernel the fictionl whiteners. Once, there re not physicl brekge. 472
Am-Eurs. J. Agric. & Environ. Sci., (3): 470-474, 2011 Tble 2: Amounts of kernel brekge nd crck t different tretments 1 Tretments 2 Broken rice (%) Crcked rice (%) (FBLW) M3 17.19 4.00 (AW) M3 17.02 4.33 (BW) M2 16.51 4.67 (BW) M3 15.97 6.33 (BW) M1 15.60 4.00 (FBLW) M2 b 14.99 4.00 (FBLW) M1 bc 12.34 2.33 (AW) M2 bc 12.15 2.67 (AW) M1 c.14 2.33 1- M 1, M 2, M 3 = pddy moisture levels of 8-9, -11 nd 12-13% (w.b.), respectively. FBLW, BW, AW= Frictionl bldeless whitener, Blde type whitener, Abrsive whitener respectively. 2-Significnt t =1% Amount of crcked rice (%) 5 0 4.96() 3.40(b) 3.29(b) B W FBLW A W Type of whitener Fig. 3: Effect of whitener type on crcked milled rice Comprisons for the mens of the tretments for the broken grins re summrized in Tble 2. The obtined results showed tht the tretment includes brsive whitener with 8-9% pddy moisture level hs yielded minimum mount of broken rice. But the mens comprisons of the broken rice indicted tht there ws no significnt difference between the AW for the pddy moisture content of 8-9 nd -11% nd FBLW t moisture content of 8-9%. In ddition, Results reveled tht there ws significnt effect (p<0.05) of whitener type nd moisture level on the crcked grins. However, the interction effects of whitener type nd pddy moisture content ws not significnt on the crcked grins. Figure 3 illustrtes the mximum percentge of crcked rice (4.96%) ws devoted to BW, but there ws no significnt differences between the AW nd FBLW. Amount of crcked rice (%) 5 0 2.84 () 3.74 (b) 4.84 (c) 8-9 % -11 % 12-13 % Moisture level (w.b.) Fig. 4: Effect of pddy moisture level on crcked milled rice This could be ttributed to tht in BW, frictionl ction between the grins led to incresed therml stress in whitening chmber, leding to more crck formtion on the grins. Fig. 4 shows the minimum percentge of crcked grins with the totl verge of 2.84%; this ws found t the lowest percentge of pddy moisture level of 8-9%. Menwhile the most crcked grin of 4.84% ws delivered t the highest pddy moisture level (12-13%). As mentioned before, the reson of therml tension resulted in grin-grin friction s well s grin-whitener, formed the grin crcks. Perhps in this level of pddy moisture content, the effect of friction on therml stresses of milling chmber ws t mximum level. Tble 2 shows the lowest percentge of crcked rice (2.33%) which ws obtined in AW nd FBLW with pddy moisture level of 8-9%. According to obtined results, it ws concluded tht the lowest broken nd crcked rice ws obtined in AW with pddy moisture content of 8-9%. ACKNOWLEDGMENTS Authors re grteful to Islmic Azd University, Rsht brnch for the scientific coopertion nd finncil support provided for the present reserch. Specil thnks devoted to Rice Reserch Institute of Irn (RRII) for providing lbortory fcilities for this project. REFERENCES 1. Pingli, P.L., M. Hossin nd R.V. Gerpcio, 1997. Asin rice bowls: the returning crisis? CABI., 473
Am-Eurs. J. Agric. & Environ. Sci., (3): 470-474, 2011 2. Witt, C., A. Dobermnn nd D. Dwe, 2004. 13. Ydv, B. nd V. Jindl, 2008. Chnges in hed rice Incresing productivity of intensive rice systems yield nd whiteness during milling of rough rice through site-specific nutrient mngement. Int. Rice. (Oryz stiv L.). J. Food Engineering, 86(1): 113-121. Res. Inst., 14. Roy, P., T. Ijiri, H. Okdome, D. Nei, T. Oriks et l., 3. Rhmn, M., M. Mih nd A. Ahmed, 1996. Sttus 2008 Effect of processing conditions on overll of rice processing technology in Bngldesh. energy consumption nd qulity of rice (Oryz Agriculturl Mechniztion in Asi Afric nd Ltin stiv L.). J. Food Engineering, 89(3): 343-348. Americ, 27: 46-50. 15. Afzlini, S., M. Shker nd E. Zre, 2002. 4. Archer, T. nd T. Siebenmorgen, 1995. Milling qulity Comprison of different rice milling methods. s ffected by brown rice temperture. Cerel Cndin Biosystems Engineering, 46(3): 63-66. Chemistry, 72(3): 304-307. 16. Frhmndfr, R., E. Frhmndfr, M. Ghsemi 5. Arullo, E.V., D. De Pdu nd M. Grhm, 1976. Rice: Vrnmkhsti nd M. Zrei, 20. Milled Rice Posthrvest Technol., Qulity Assessment. Interntionl J. Food 6. Bonifcio, E.P., 1989. Effect of Milling Opertions on Engineering, 6(2): 1682. Grin Qulity nd Price in Selected Philippine Rice 17. Firouzi, S., M.R. Alizdeh nd S. Minei, 20. Effect Mills. of the size of perforted screen nd blde-rotor 7. Greeley, M., 1987. Posthrvest losses, technology clernce on the performnce of Engleberg rice nd employment: the cse of rice in Bngldesh. whitener. Africn J. Agriculturl Res., 5(9): 941-946. Westview Specil Studies in Socil, Politicl nd 18. Med, R., R.N. Curnow nd A.M. Hsted, 2003. Economic Development (Us). Sttisticl Methods in Agriculture nd Experimentl 8. Lyon, B.G., E.T. Chmpgne, B.T. Vinyrd, Biol., CRC. Press. W.R. Windhm, F.E. Brton et l., 1999. Effects of 19. Cnossen, A., M. Jimenez nd T. Siebenmorgen, 2003. degree of milling, drying condition nd finl moisture Rice fissuring response to high drying nd tempering content on sensory texture of cooked rice. Cerel. tempertures. J. Food Engineering, 59(1): 61-69. Chemistry, 76(1): 56-62. 20. Zhng, Q., W. Yng, L. Howrd nd C. Erp, 2003. 9. Ojh, T., 1984. Improved post-hrvest technology to Trcing fissure informtion by scnning electron mximize yield nd minimize quntittive nd microscopy chrcteriztion of nturlly fissured qulittive losses. The United Ntions University. surfces of rice kernels. Trnsctions-mericn. Wongpornchi, S., K. Dumri, S. Jongkewwttn Society of Agriculturl Engineers, 46(6): 583-1588. nd B. Siri, 2004. Effects of drying methods nd 21. Yng, W., C.C. Ji, T. Siebenmorgen, Z. Pn nd storge time on the rom nd milling qulity of rice A. Cnossen, 2003. Reltionship of kernel moisture (Oryz stiv L.) cv. Kho Dwk Mli 5. Food content grdients nd glss trnsition tempertures Chemistry, 87(3): 407-414. to hed rice yield. Biosystems Engineering, 11. Stke, S., Y. Okd nd S. Ariji, 1997. Brn-removing 85(4): 467-476. Perforted Cylindricl Body of Abrsive Type Grin 22. Mdmb, P.S. nd R.P. Ybes, 2005. Determintion Milling Mchine. of the optimum intermittent drying conditions for 12. Chmpgne, E.T., K.L. Bett, B.T. Vinyrd, B.D. Webb, rough rice (Oryz stiv, L.). Lebensmittel- A.M. McClung, et l., 1997. Effects of drying Wissenschft und-technologie,. 38(2): 157-165. conditions, finl moisture content nd degree of 23. Zhng, Q., W. Yng nd Z. Sun, 2005. Mechnicl milling on rice flvor. Cerel Chemistry, 74(5): properties of sound nd fissured rice kernels nd 566-570. their implictions for rice brekge. J. Food Engineering, 68(1): 65-72. 474