Milling and Functional Properties of Co-mingled Rice Cultivars

Transcription

1 University of Arknss, Fyetteville Theses nd Disserttions Milling nd Functionl Properties of Co-mingled Rice Cultivrs Nikhil N. Bsutkr University of Arknss, Fyetteville Follow this nd dditionl works t: Prt of the Agronomy nd Crop Sciences Commons, Food Processing Commons, nd the Other Food Science Commons Recommended Cittion Bsutkr, Nikhil N., "Milling nd Functionl Properties of Co-mingled Rice Cultivrs" (2014). Theses nd Disserttions This Thesis is brought to you for free nd open ccess by It hs been ccepted for inclusion in Theses nd Disserttions by n uthorized dministrtor of ScholrWorks@UARK. For more informtion, plese contct scholr@urk.edu.

2 Milling nd Functionl Properties of Co-mingled Rice Cultivrs

3 Milling nd Functionl Properties of Co-mingled Rice Cultivrs A thesis submitted in prtil fulfillment of the requirements for the degree of Mster of Science in Food Science By Nikhil Bsutkr University of Mumbi Bchelor of Technology in Food Engineering nd Technology, 2011 My 2014 University of Arknss This thesis is pproved for recommendtion to the Grdute Council. Dr. Terry J. Siebenmorgen Thesis Director Dr. Y-Jne Wng Committee Member Dr. Andronikos Muromoustkos Committee Member

4 ABSTRACT Differences hve been observed in the milling nd functionl properties of different rice cultivrs, prticulrly between hybrid nd pureline cultivrs. Co-mingling of rice cultivrs commonly occurs during hrvest, storge nd drying opertions. Thus, there is need to study the effect of co-mingling on the milling nd functionl properties of rice cultivrs. Two longgrin, hybrid (H) cultivrs CL XL745 nd CL XL729 nd two long-grin, pureline (P) cultivrs CL 151 nd Wells were used to prepre CL XL745/CL 151 (H/P), CL XL745/CL XL729 (H/H) nd Wells/CL 151 (P/P) co-mingles, mixed in vrious proportions. Milled rice yield (MRY), hed rice yield (HRY), surfce lipid content (SLC), hed rice color, hed rice chlkiness nd geltiniztion nd psting properties of hed rice flour were mesured for individul lot smples, s well s the bove mentioned co-mingled smples. Kernel dimensions, totl lipid content (TLC), chlkiness nd bulk density of brown rice smples of the individul cultivr lots were lso studied to determine the effect of brown rice properties of individul cultivr lots on the milling nd functionl properties of co-mingled smples. The MRYs, HRYs, hed rice chlkiness nd psting properties of the co-mingled smples incresed or decresed with the incresing percentge of given cultivr in the co-mingled smples. The differences in hed rice whiteness nd yellowness of the co-mingled smples milled to the sme DOM were negligible, indicting tht co-mingling did not ffect the color of rice fter milling to the sme DOM. An investigtion of geltiniztion curves showed tht the co-mingled smples retined chrcteristics of the geltiniztion properties of the individul cultivrs used in those comingles. For exmple, the onset geltiniztion temperture (T o ) of co-mingled smple ws equivlent to the T o of tht cultivr in the co-mingle with the lower T o. These findings will help

5 to mke key decisions regrding the use of co-mingles depending on the brown rice, milling nd functionl properties of the individul cultivr lots used for co-mingling.

6 nd this thesis: ACKNOWLEDGEMENTS I would like to cknowledge the following who hve contributed to my grdute studies My dvisor, Dr. Terry J. Siebenmorgen, for his invluble mentorship nd support through my MS degree. My grdute committee members, Dr. Y-Jne Wng nd Dr. Andronikos Muromoustkos, for the guidnce nd support they hve offered throughout. Dr. Brndon Grigg nd Dr. Jmes Ptindol for their support nd dvice during the course of this project. The industry sponsors of the University of Arknss Rice Processing Progrm nd the University of Arknss Food Science Deprtment for the finncil support of this project. The Rice Processing Progrm stff who ssisted with dt collection. Finlly, my fmily in Indi nd my friends in Fyetteville for their continued support nd encourgement throughout the wy.

7 TABLE OF CONTENTS OVERALL INTRODUCTION... 1 MILLING PROPERTIES OF CO-MINGLED RICE CULTIVARS... 3 INTRODUCTION... 3 MATERIALS AND METHODS... 6 Smple procurement nd preprtion... 6 Milling yields... 7 Surfce lipid content nd totl lipid content... 8 Hed rice color... 9 Hed rice nd brown rice chlkiness... 9 Bulk density Dt nlysis RESULTS AND DISCUSSION Properties of bulk lots Milling durtions required by the co-mingled smples to rech 0.4% surfce lipid content 17 Milled rice yields of co-mingled smples Hed rice yields of co-mingled smples Hed rice color of co-mingled smples Hed rice chlkiness of co-mingled smples CONCLUSION REFERENCES APPENDIX... 38

8 FUNCTIONAL PROPERTIES OF CO-MINGLED RICE CULTIVARS INTRODUCTION MATERIALS AND METHODS Smple procurement nd preprtion Surfce lipid content Geltiniztion properties Psting properties Dt nlysis RESULTS AND DISCUSSION Geltiniztion properties of co-mingled smples Psting properties of co-mingled smples CONCLUSION REFERENCES APPENDIX OVERALL CONCLUSIONS... 69

9 OVERALL INTRODUCTION Given tht rice is the most importnt stple food for mjority of the world's popultion (USDA, 2008), it is importnt to grow sufficient mounts of rice to stisfy the needs of tht mjority. Cultivtion of hybrid rice is prt of the solution tht will help to meet those demnds. An intct rice kernel consists of endosperm nd germ covered by first, the brn nd then the hull. The kernel in this stge is clled rough rice. Removl of the hull from rough rice results in brown rice. When brown rice is milled, primrily brn nd germ re removed nd white rice is obtined. In the removl of brn nd germ, there cn be indvertent loss of endosperm tht mkes up white rice, prticulrly during extended milling, nd consequently, economic losses re incurred. Strch is the mjor component of rice nd undergoes order-disorder trnsitions during geltiniztion (Sivk nd Preiss, 1998). Thus, geltiniztion properties govern the mount of het input required to cook rice. Strch grnules form pste fter becoming geltinized nd the cooking behvior of rice is reflected by its psting properties. Consequently, geltiniztion nd psting properties of rice determine the end-use pplictions of rice nd re therefore importnt for food processors from cooking point of view to optimize nd mintin process conditions nd product chrcteristics. Rice hs cultivr-specific milling nd functionl properties becuse of differences in kernel dimensions (Chen et l., 1999; Chen nd Siebenmorgen, 1997), topogrphies (Bhshym nd Srinivs, 1984; Pomernz nd Webb, 1985), moisture content (Andrews et l., 1992), chlkiness (Ambrdekr et l., 2011; Cheng et l., 2005; Ptindol nd Wng, 2003) nd chemicl composition (Li et l., 2001; Vndeputte et l., 2003). Moreover, functionl properties of rice re lso ffected by the degree to which it is milled (Chmpgne et l., 1990; Mrshll, 1992; 1

10 Perdon et l., 2001; Sleh nd Meullenet, 2007). Therefore, when rice cultivrs re co-mingled during opertions such s hrvesting, drying nd storge, there could be resultnt impct on milling nd functionl properties. This my deleteriously ffect processing opertions such s milling, cooking, nd prboiling. Although considerble reserch hs been conducted on studying the milling nd functionl properties of individul rice cultivr lots, effects of comingling on these properties hve not been studied. Therefore, there is need to study the effects of co-mingling on the milling nd functionl properties of rice cultivrs. 2

11 MILLING PROPERTIES OF CO-MINGLED RICE CULTIVARS Nikhil Bsutkr, Terry Siebenmorgen, Andronikos Muromoustkos, Brndon Grigg INTRODUCTION A rice kernel with the husk intct is known s rough rice, which when dehulled, gives brown rice. When brown rice is milled, initilly the germ nd brn lyers re removed, followed by outer lyers of the endosperm. Degree of milling (DOM) is the extent of removl of germ nd brn during milling. As DOM increses, more of these re removed nd mss of the milled kernels decreses. DOM is importnt s it ffects milling yield (Cooper nd Siebenmorgen, 2007) nd functionl chrcteristics, including, texture of cooked rice (Sleh nd Meullenet, 2007) nd psting properties (Perdon et l., 2001). Rice brn is present on the surfce of rice kernel nd contins 15-20% lipids (Julino, 1985). Therefore, surfce lipid content (SLC) is directly relted to the extent to which rice is milled nd is n indictor of DOM of rice (Hogn nd Deobld, 1961; Miller et l., 1979; Pomernz et l., 1975). Lmberts et l. (2007) showed tht yellow nd red pigments in rice re minly concentrted in the brn nd thus, yellowness of kernels decreses wheres whiteness increses with n increse in DOM. Therefore, hed rice yellowness nd hed rice whiteness cn lso be used s indictors of DOM. Rice is the most importnt stple food for mjority of the world s humn popultion. World rice production hs lmost qudrupled from 1960/61 to 2008/09 hrvest yers (USDA, 2013), prtly due to the cultivtion of hybrid rice. Acrege of hybrid cultivrs hs incresed in lrge prt due to greter gronomic yields, strong disese resistnce nd more efficient use of soil nutrients, s compred to pureline cultivrs. However, differences hve been observed in the milling properties of hybrid nd pureline cultivrs (Lnning nd Siebenmorgen, 2007; 3

12 Siebenmorgen et l., 2006). Lnning nd Siebenmorgen (2011) showed tht hybrid rice cultivrs rech trget SLC fster thn pureline cultivrs. This suggests tht hybrid cultivrs require shorter milling durtions thn pureline cultivrs to rech prticulr DOM, possibly due to differences in the brn lyer thickness or the brn/embryo chemicl composition. Vrious rice kernel chrcteristics such s kernel topogrphy (Bhshym & Srinivs, 1984; Pomernz & Webb, 1985), physicl dimensions (Chen et l., 1999; Chen nd Siebenmorgen, 1997) nd moisture content (Andrews et l., 1992) hve been shown to ffect the milling performnce of rice. Therefore, different cultivrs often hve different DOM levels when milled for given durtion (Siebenmorgen et l., 2006). Bhshym nd Srinivs (1984) nd Pomernz nd Webb (1985) showed tht kernels with deeper surfce grooves require longer milling durtions or greter milling pressure to rech specified DOM. As brn is likely to be more redily removed from the ridges but left remining in the grooves, more milling is required to remove brn from the grooves, which invribly results in the removl of endosperm from the ridges. This results in the loss of useful endosperm s well s possible, incresed brekge. Therefore, milling losses re less for shllow-grooved cultivrs reltive to deep-grooved ones (Bhshym nd Srinivs, 1984). In studies of long-grin (Chen nd Siebenmorgen, 1997) nd medium-grin (Chen et l., 1999) cultivrs, it ws observed tht when rice ws lightly milled, the SLC of thicker kernels ws significntly lower thn tht of thinner kernels. This suggested tht thicker kernels re milled t fster brn removl rte thn the thinner kernels during the initil stges of milling. When the extent of milling ws incresed, this difference in kernel SLCs progressively decresed nd ultimtely, there ws no significnt difference between the SLCs of thicker nd thinner kernels, when milled beyond certin bulk DOM. 4

13 Hed rice yield (HRY) is expressed s the mss percentge of rough rice remining s hed rice, i.e., milled kernels tht re t lest three-qurters of their originl length (USDA, 2005). Hed rice is more vluble thn broken rice nd thus, mximizing HRY is of economic importnce in the rice industry. HRY nd DOM re significntly ffected by the moisture content of rice kernels (Bnszek et l., 1989; Webb nd Clderwood, 1977). For the sme milling durtion, decrese in kernel moisture content cuses the HRY to increse nd DOM to decrese (Bnszek et l., 1989; Webb nd Clderwood, 1977). Chlkiness is mjor defect in rice kernels. It usully occurs when high nighttime ir tempertures (NTATs) re experienced during certin criticl stges of kernel development. Also, some cultivrs re more susceptible to high NTATs thn others (Ambrdekr et l., 2011; Cooper et l., 2008; Counce et l., 2000). One undesirble effect of chlkiness is tht kernel strength is reduced. Thus, chlky kernels tend to brek during milling, reducing the HRY (Ambrdekr et l., 2011). Co-mingling of rice cultivrs commonly occurs during hrvest, drying nd storge opertions. Becuse kernels of different physicl dimensions, topogrphies, moisture content nd chlkiness my be mixed during co-mingling, there could be resultnt impct on milling properties, prticulrly when dissimilr cultivrs re co-mingled. Therefore, evluting the effects of co-mingling on milled rice chrcteristics could provide justifiction for identity preservtion of cultivr lots nd id in mngement decisions regrding cultivr co-mingling t the field or post-hrvest levels. While the forementioned studies report the impcts of singlecultivr chrcteristics on HRY, chlk nd DOM, no reserch ws found showing the consequences of co-mingling on these properties. 5

14 MATERIALS AND METHODS Smple procurement nd preprtion The study ws conducted using four long-grin cultivrs, CL XL729 nd CL XL745 (hybrids) nd CL 151 nd Wells (purelines), grown in two seprte yers, 2011 nd Among the 2011 lots, the CL (Clerfield ) cultivrs (CL XL729, CL XL745 nd CL 151) were procured from Jonesboro, AR nd Wells from Stuttgrt, AR. Among the 2012 lots, the CL cultivrs were procured from Hrrisburg, AR nd Wells from Forest City, AR. The 2011 lots were selected to hve high HRY while the 2012 lots were selected to hve low HRY; this ws done to determine if co-mingling hd similr effect on rice of different levels of milling yield. All lots were clened using dockge tester (Model XT4, Crter-Dy Co., Minnepolis, MN) nd conditioned to 12±0.5% (wet bsis) moisture content. A convection oven (1370FM, Sheldon Mfg. Inc., Cornelius, OR) ws used to mesure the moisture content of rough rice by drying duplicte smples t 130 C for 24 h (Jindl nd Siebenmorgen, 1987). The bulk lots were then refrigerted in plstic bins t 4±2 C. Before smple preprtion, the bulk lots were removed from refrigerted storge nd equilibrted in the sme bins to room temperture for t lest 24 h. The co-mingled smples prepred re presented in tble 1.1. Co-mingling rtios of 25:75, 50:50 nd 75:25 were selected to reflect brod rnge of co-mingling. The CL XL745/CL 151 co-mingle lso included the 90:10 nd 10:90 rtios to investigte effects of the common prctice of plnting CL 151 on the levees of CL XL745 fields. Four replicte smples of rough rice for ech individul cultivr/comingling rtio, ll weighing 150 g, were prepred for multiple milling durtions. Therefore, the msses of the individul cultivrs in the co-mingled smples were 15/135 g, 38/112 g, 75/75 g, 112/38 g nd 135/15 g respective to the 10:90, 25:75, 50:50, 75:25 nd 90:10 co-mingling rtios. 6

15 To reduce bis, the individul lots of rough rice were first divided into close pproximtion of the required quntities using grin divider (Boerner Divider, Seedburo Equipment Co., Chicgo, IL), weighed nd then mixed in respective proportions. Ech co-mingled smple of rough rice ws thoroughly homogenized for 2 min using rotry rice-grder (TRG, Stke, Tokyo, Jpn). Tble 1.1. Co-mingles prepred for the study Co-mingle Cultivr-Lot Type Co-mingling Rtios CL XL745/CL 151 hybrid/pureline 10:90, 25:75, 50:50, 75:25, 90:10 CL XL745/CL XL729 hybrid/hybrid 25:75, 50:50, 75:25 Wells/CL 151 pureline/pureline 25:75, 50:50, 75:25 Milling yields Ech smple of 150-g rough rice ws first dehulled in lbortory sheller (THU 35B, Stke, Hiroshim, Jpn), hving cm (0.019-in.) clernce between the rollers. The resulting brown rice ws then milled for 10, 20, 30 or 40 s using lbortory mill (McGill No. 2, RAPSCO, Brookshire, TX), hving 1.5-kg mss plced on the lever rm, 15 cm from the centerline of the milling comprtment. Milled rice, which comprises intct nd broken kernels, ws weighed to clculte milled rice yield (MRY), which ws expressed s the mss percentge of 150 g of rough rice remining s milled rice. Hed rice ws then seprted from the brokens using sizing device (Model 61, Grin Mchinery Mnufcturing Corp., Mimi, FL). Hed rice yield (HRY) ws expressed s the mss percentge of 150 g of rough rice remining s hed rice. Cultivrs vry in brn removl rtes nd thus hve different DOM levels when milled for the sme durtion (Siebenmorgen et l., 2006). As HRY is linerly nd directly relted to SLC (Cooper nd Siebenmorgen, 2007; Reid et l., 1998; Lnning nd Siebenmorgen, 2011), milling the smples for vrious durtions ws essentil to obtin HRY vs. SLC reltionships (sometimes 7

16 referred to s millbility curves). From the curves, HRYs corresponding to trget SLC vlue were determined; this procedure ccounted for differences in brn removl rtes. Surfce lipid content nd totl lipid content Surfce lipid content (SLC) of hed rice nd totl lipid content (TLC) of ground, brown rice were mesured using lipid extrction system (Soxtec Avnti 2055, Foss North Americ, Eden Pririe, MN), following the method (AACC Intl., 2000), with modifictions s described by Mtsler nd Siebenmorgen (2005). While SLC ws mesured for ll hed rice smples, TLC ws mesured only for brown rice from the four individul cultivr lots. For TLC mesurement, smples of brown rice were ground using cyclone mill ( , UDY, Fort Collins, CO) equipped with 100-mesh (0.5-mm) sieve. Approximtely 5 g of hed rice or ground, brown rice ws weighed into cellulose thimbles (33mm, i.d. 80 mm, externl length) (Foss North Americ, Eden Pririe, MN). After pre-drying the smples nd thimbles for n hour in n oven mintined t 100±2 C, the thimbles with hed rice or ground, brown rice inside were plced in the lipid extrctor. Aluminum cups were then weighed nd plced under the thimbles in the lipid extrctor. Lipids were extrcted by boiling the thimbles in 70 ml of petroleum ether (boiling point C; VWR, Suwnee, GA) nd then rinsing with the petroleum ether condenste for 30 min. When most of the solvent hd evported from the extrction cups fter pproximtely 3 min, the cups were plced in n oven (100±2 C) to evporte the residul solvent nd lter plced in desicctor for 30 min to cool to room temperture. Finlly, the cups contining the extrcted lipids were weighed. The mss of the extrcted lipids ws obtined by subtrcting the originl mss of the cups from the mss of the cups contining the extrcted lipids. The rtio of mss of the extrcted lipids to the originl mss of hed rice or ground, brown rice, multiplied by 100, gve SLC nd TLC percentges, respectively. 8

17 Hed rice color Whiteness (L*) nd yellowness (b*) of ll hed rice smples were mesured using colorimeter (ColorFlex Colorimeter, Hunter Assocites Lbortory, Reston, VA). The instrument's smple continer, smll plstic petri dish (6-cm dimeter), ws filled with pproximtely 30 g of the smple, plced into the smple port, covered with the blck cover provided nd the first mesurement recorded. A second mesurement ws recorded by rotting the smple continer by 120 to 180 degrees. The instrument ws progrmmed to verge the two redings. Hed rice nd brown rice chlkiness As 0.4% SLC is the degree to which rice is often milled in the rice industry, hed rice chlkiness ws mesured for ll individul cultivr lot nd co-mingled smples tht hd been milled for durtions tht produced DOM closest to 0.4% SLC, while brown rice chlkiness ws mesured only for brown rice smples of the individul cultivr lots. Chlkiness ws mesured using n imge nlysis system (WinSeedle Pro 2005, Regent Instruments Inc., Sinte-Foy, Quebec, Cnd), ccording to the procedure of Ambrdekr et l. (2011). Approximtely 100 hed rice kernels from smple were plced on trnsprent, crylic-sheet try (152 mm 100 mm 20 mm), such tht no two kernels were in contct with ech other. A blue bckground ws selected for scnning to hve contrst in color between the rice kernels nd the bckground. The imging system ws configured to quntify rice-kernel surfce re ginst this contrsting bckground. Using completely chlky kernel s the reference color for chlk, the imging system ws lso configured to color-clssify kernel chlkiness. The system mesured the number of pixels corresponding to the kernel projected re nd the number of pixels corresponding to res color-clssified s chlk. The rtio of the number of pixels representing the chlky res of 9

18 the kernels to the number of pixels representing the totl re of the kernels, multiplied by 100, gve percent chlk. This procedure ws repeted on nother set of 100 kernels from the sme smple nd n verge of the two redings ws recorded s percent chlk for tht smple. The sme procedure ws used to mesure brown rice chlkiness of the individul cultivr lot smples. Bulk density Bulk density of brown rice ws mesured for the four individul cultivrs using bulk density test weight pprtus (Filling Hopper nd Stnd, Seedburo Equipment Co., Chicgo, IL), ccording to the procedure of Fn et l. (1998). The pint cup provided ws weighed nd plced under the funnel (hopper) of the pprtus on collection pn. Brown rice ws loded into the hopper, nd then the hopper vlve ws opened to llow the rice to flow into the cup until it overflowed. The smple ws leveled to the top of the cup by oscillting wooden stick provided in zigzg motion. The cup filled with the smple ws weighed. Subtrcting the mss of the empty cup from the mss of the cup contining the smple gve the mss of the smple. The procedure ws repeted twice. The three msses were then verged nd divided by the volume of the pint cup to obtin the bulk density in g/cm 3. Dt nlysis Brown rice properties of individul cultivr lots were compred mong cultivrs nd cross hrvest yers. In order to ccount for the vrition in the DOM of different cultivrs, milling durtions, MRYs, HRYs nd color vlues were djusted for ll individul cultivr lot nd co-mingled smples. Regression nlyses of SLC vs. milling durtion were conducted on four replicte smples milled for 10, 20, 30 or 40 s. These equtions were used to determine the milling durtions required by smples to rech DOM level of 0.4% SLC. Likewise, regression nlyses of MRYs, HRYs nd color vlues vs. SLCs were conducted nd using these equtions, 10

19 their vlues were djusted to 0.4% SLC. Hed rice chlkiness ws compred for individul cultivr lot nd co-mingled smples. An verge of SLCs for ech milling durtion (10, 20, 30 or 40 s) for ech co-mingle from ech yer ws tken nd the milling durtion tht produced DOM closest to 0.4% SLC ws selected s the bsis of comprison for tht co-mingle. Regression nlyses, nlysis of vrince (α=0.05) nd comprison of mens using Tukey's Honestly Significnt Difference (HSD) test were performed using sttisticl softwre (JMP Pro 10, SAS Institute, Cry, NC). RESULTS AND DISCUSSION Properties of bulk lots Brown rice properties of bulk density, kernel dimensions, chlkiness nd TLC of the four individul cultivr lots re presented in tble 1.2. Between the cultivr lots used in the P/P (Wells/CL 151) co-mingle, brown rice bulk density of Wells ws less thn tht of CL 151 in In 2012, the trend ws reversed. Between the cultivr lots used in the H/P (CL XL745/CL 151) co-mingle, brown rice bulk density of CL XL745 ws greter thn tht of CL 151 in both hrvest yers. Between the cultivr lots used in the H/H (CL XL745/CL XL729) co-mingle, there ws no difference in the brown rice bulk density of CL XL745 nd CL XL729 in both yers. Across hrvest yers, between the cultivr lots used in the P/P co-mingle, brown rice kernels of Wells were longer nd nrrower thn those of CL 151. Between the cultivr lots used in the H/P co-mingle, brown rice kernels of CL 151 were shorter nd wider thn those of CL XL745 in However, in 2012, brown rice kernels of CL 151 were shorter nd nrrower thn the brown rice kernels of CL XL745. Between the cultivr lots used in the H/H co-mingle, brown rice kernels of CL XL745 were longer nd of equivlent width to those of CL XL729 in However, in 2012, brown rice kernels of CL XL745 were both longer nd wider thn the brown 11

20 Tble 1.2. Brown rice properties of individul cultivr lots. Yer Cultivr Bulk density (kg/m 3 ) Length (cm) Brown rice property Width (cm) Thickness (cm) Chlkiness (%) TLC (%) Wells 750 de [1] 7.12 b 2.09 f 1.80 b 3.6 d 2.45 d CL bc 6.80 e 2.23 b 1.79 b 3.2 d 2.60 bc CL XL c d 2.28 e CL XL b 6.99 c 2.21 c d 2.34 e Wells 747 e e c 2.36 de CL f 6.78 e 2.23 b 1.79 b 5.3 c 2.95 CL XL de b 8.0 b 2.64 bc CL XL cd 6.93 d 2.18 d b [1] Sttisticl differences in mens of bulk density, kernel dimensions, chlkiness nd totl lipid content (TLC), mong cultivrs nd cross hrvest yers, re indicted by different letters, ccording to Tukey's Honestly Significnt Difference test, t 0.05 level of significnce. rice kernels of CL XL729. No significnt differences were observed in the thicknesses of the four individul cultivr lots cross hrvest yers. There were no sttisticl differences in the brown rice chlkiness of the four individul cultivr lots from 2011 wheres, brown rice chlkiness of the 2012 lots differed significntly, rnging from 5.3% for CL 151 nd 5.6% for Wells to 12.0% for CL XL729 (tble 1.2). Overll, the 2012 cultivr lots hd greter brown rice chlkiness thn lots comprising the sme cultivrs from the 2011 hrvest. Between the cultivr lots used in the P/P co-mingle, TLC of CL 151 ws greter thn tht of Wells in both hrvest yers. Similrly, between the cultivr lots used in the H/P co-mingle, TLC of CL 151 ws greter thn tht of CL XL745 in both hrvest yers. There ws no difference in the TLCs of the cultivr lots used in the H/H co-mingle, i.e., CL XL745 nd CL XL729, in both hrvest yers. These differences in bulk densities, kernel dimensions, chlkiness 12

21 nd TLCs of brown rice led to milling differences in the individul cultivr lot nd co-mingled smples tht re subsequently explined. SLC vs. milling durtion, MRY vs. SLC, nd HRY vs. SLC curves for the individul cultivr lots for both hrvest yers re presented in fig Figs. 1.1 nd 1.1b show tht SLC decresed exponentilly with n increse in milling durtion nd figs. 1.1c-1.1f show tht MRY nd HRY decresed linerly with decreses in SLC. Regression nlyses of SLC vs. milling durtion, MRY vs. SLC nd HRY vs. SLC were conducted (tbles ) nd vlues (milling durtion, MRY nd HRY) were predicted bsed on these regression equtions, to chieve trget DOM level of 0.4% SLC. These predicted vlues of the individul cultivr lots re presented in tble 1.3. CL 151 ws used in the H/P nd P/P co-mingles nd CL XL745 ws used in the H/P nd H/H co-mingles ech yer. Therefore, CL 151 nd CL XL745 were the cultivrs tht were used in two co-mingles in ech yer. Dniels et l. (1998) hve shown tht storge up to three months fter hrvest hs significnt impct on milling properties. Since there ws no considerble time difference in studying the milling properties of the H/P nd P/P co-mingles in both yers, it would hve been redundnt to study the milling properties of CL 151 twice in ech yer. Therefore, the milling properties of CL 151 were studied only once in ech yer nd were used to represent the 0:100 rtio in the H/P nd the P/P co-mingles. Similrly, s there ws no considerble time difference in studying the milling properties of the H/P nd H/H co-mingles in 2012, milling properties of CL XL745 were studied only once in tht yer nd they were used to represent the 100:0 rtio in the H/P nd H/H co-mingles tht yer. However, s there ws considerble time difference of four months in studying the H/P nd H/H co-mingles in 2011, the milling properties of CL XL745 were studied twice, first s prt of the H/P co-mingle nd 13

22 HRY (%) HRY (%) MRY (%) MRY (%) SLC (%) SLC (%) Wells CL CL XL CL XL Milling durtion (s) () Milling durtion (s) (b) SLC (%) (c) SLC (%) (e) SLC(%) (d) SLC (%) 1.2 (f) Fig Surfce lipid content (SLC) vs. milling durtion (, b), milled rice yield (MRY) vs. SLC (c, d) nd hed rice yield (HRY) vs. SLC (e, f) plots of the indicted cultivr lots milled for 10, 20, 30 nd 40 s using lbortory mill. Ech dt point represents n verge of four replictes for ech milling durtion. 14

23 Tble 1.3. Milling durtions nd milling yields of individul cultivr lots djusted [1] to degree of milling (DOM) level of 0.4% surfce lipid content (SLC). Yer Cultivr Milling durtions nd yields predicted t DOM of 0.4% SLC Milling durtion (s) MRY (%) HRY (%) 2011 Wells CL CL XL745/w CL 151/CL XL729 25/30 [2] 74.7/ /61.9 CL XL Wells CL CL XL CL XL [1] Milling durtions, milled rice yields (MRYs) nd hed rice yields (HRYs) were djusted using regression nlyses of SLC vs. milling durtion, MRY vs. SLC nd HRY vs. SLC, respectively (See tbles for regression nlysis constnts). [2] Dniels et l. (1998) hve shown tht storge up to three months fter hrvest hs significnt impct on milling properties. There ws considerble gp in studying the CL XL745/CL 151 nd CL XL745/CL XL729 co-mingles in Therefore, the milling properties of CL XL745 were studied twice, first s prt of the CL XL745/CL 151 co-mingle (first vlue in ech cell in tht row) nd secondly s prt of the CL XL745/CL XL729 co-mingle (second vlue in ech cell in tht row). secondly s prt of the H/H co-mingle in tht yer. Therefore, there re two vlues for milling durtion, MRY nd HRY of CL XL745 from 2011 in tble 1.3. The first vlue in ech cell in the 2011 CL XL745 row is the vlue of the given property of CL XL745 tht ws studied s prt of the 2011 H/P co-mingle nd ws therefore used to represent the 100:0 rtio in tht co-mingle. The second vlue in ech cell in the 2011 CL XL745 row is the vlue of the given property of CL XL745 tht ws studied s prt of the 2011 H/H co-mingle nd ws therefore used to represent the 100:0 rtio in tht co-mingle. In fig. 1.1, c nd e, two curves were not used to represent the two times tht CL XL745 ws studied in 2011, since those curves were only used to 15

24 illustrte the trends in SLC, MRY nd HRY. In those curves, the first lot of CL XL745, the one tht ws studied s prt of the 2011 H/P co-mingle, hs been presented. Between the cultivr lots used in the P/P co-mingle, CL 151 required greter milling durtion (32 s in 2011 nd 25 s in 2012) thn Wells (30 s in 2011 nd 20 s in 2012) to rech DOM of 0.4% SLC. Between the cultivr lots used in the H/P co-mingle, CL 151 required greter milling durtion (32 s in 2011 nd 25 s in 2012) thn CL XL745 (25 s in 2011 nd 18 s in 2012) to rech DOM of 0.4% SLC. Between the cultivr lots used in the H/H co-mingle, CL XL745 required greter milling durtion (30 s) thn CL XL729 (25 s) to rech DOM of 0.4% SLC in However, in 2012, there ws hrdly ny difference (1 s) in the milling durtions required by the two hybrid cultivr lots (18 s for CL XL745 nd 17 s for CL XL729) to ttin DOM of 0.4% SLC. These differences in the milling durtions required by the individul cultivr lots to ttin 0.4% SLC suggest tht when the P/P nd H/P co-mingles from both yers nd the H/H co-mingle from 2011 re milled, it could be tht the CL 151 kernels in the P/P nd H/P comingles nd the CL XL745 kernels in the H/H co-mingle will be under-milled wheres the CL XL745 kernels in the H/P co-mingle, Wells kernels in the P/P co-mingle nd CL XL729 kernels in the H/H co-mingle will be over-milled. However, unlike the other co-mingles, the H/H comingle from 2012 might mill more homogeneously since CL XL745 nd CL XL729 from 2012 hd overlpping SLC vs. milling durtion curves (fig. 1.1b) nd thus required similr milling durtions to ttin 0.4% SLC. However, the dynmics of milling individul cultivr lots seprtely my be different thn when different lots re co-mingled nd milled simultneously. Between the cultivr lots used in the P/P co-mingle, Wells hd greter MRY but lesser HRY compred to CL 151 in both hrvest yers. Similrly, between the cultivr lots used in the H/P co-mingle, CL XL745 hd greter MRY but lesser HRY compred to CL 151 in both 16

25 hrvest yers. On the other hnd, between the cultivr lots used in the H/H co-mingle, CL XL729 hd lesser MRY nd lesser HRY thn CL XL745 in both hrvest yers. HRYs of the 2011 lots rnged from 59.7% for Wells to 66.7% for CL 151, nd were found to be fr superior to the 2012 lots, whose HRYs rnged from 36.3% for Wells to 57.5% for CL 151. These differences between HRYs of the sme cultivr lot cross both hrvest yers cn be ttributed in prt to the greter chlkiness of the 2012 lots compred to those of the 2011 lots, demonstrting the fct tht chlky kernels re wek nd tend to brek during milling, reducing the HRY (Ambrdekr et l., 2011). Milling durtions required by the co-mingled smples to rech 0.4% surfce lipid content Prmeter estimtes obtined on conducting regression nlyses of SLC s function of milling durtion for ll co-mingled smples in both hrvest yers re presented in tble 1.4. Milling durtions required to ttin trget DOM of 0.4% SLC re presented s br chrts in fig As previously mentioned, in the H/P co-mingle in both hrvest yers (fig. 1.2), the 0:100 rtio, consisting of only CL 151, required greter milling durtion (32 s in 2011 nd 25 s in 2012) thn the 100:0 rtio, consisting of only CL XL745 (25 s in 2011 nd 18 s in 2012). In 2011, the milling durtions initilly incresed from the 0:100 rtio to the 10:90 rtio, nd then decresed. The 10:90 rtio required the gretest milling durtion, followed by the 25:75 rtio, to chieve the trget DOM of 0.4% SLC. Similr trend ws followed by the milling durtions required by the H/P co-mingle smples in Brown rice kernels of CL 151 were shorter nd wider thn those of CL XL745 in 2011, but in 2012, the CL 151 brown rice kernels were shorter nd nrrower thn those of CL XL745. In ddition, TLC of CL 151 ws greter thn tht of CL XL745 in both hrvest yers. Therefore, it cn be resoned tht kernel length nd TLC influence the milling dynmics of the H/P co-mingle wheres width does not ply n importnt role. Consequently, the greter milling durtions for the 10:90 nd the 25:75 rtios suggest tht when 17

26 two cultivrs, one with shorter nd greter-tlc kernels thn the other re co-mingled, in proportion where the shorter nd greter-tlc kernels re in excess, milling durtion to rech DOM of 0.4% SLC is greter thn tht required when milling the individul cultivrs seprtely. When co-mingled, the shorter CL 151 kernels possibly hide between the longer CL XL745 kernels nd therefore, the CL XL745 kernels mill fster thn the CL 151 kernels. In the H/H co-mingle from 2011, the 100:0 rtio, consisting of only CL XL745, required greter milling durtion (30 s) thn the 0:100 rtio, consisting of only CL XL729 (25 s), to ttin DOM of 0.4% SLC (fig. 1.2b). Milling durtions required by the 0:100, 50:50, 75:25 nd the 100:0 rtios incresed with n increse in percentge of CL XL745 in tht co-mingle. However, the 25:75 rtio, like the 10:90 nd the 25:75 rtios from the H/P co-mingle, required greter milling durtion thn wht it would hve required, hd it followed the forementioned trend of the milling durtions incresing with n increse in percentge of CL XL745 in the comingled smples. CL XL729 brown rice kernels were shorter thn those of CL XL745 with no difference in their TLCs. Therefore, it cn be ssumed tht TLCs did not ply n importnt role in this cse. Therefore, the 2011 H/H co-mingle suggests tht when two cultivrs, one with shorter brown rice kernels thn the other, re co-mingled in proportion where the shorter kernels re in excess, milling durtion required to rech 0.4% SLC is greter thn tht required when the individul cultivr lots re milled seprtely. This might hppen becuse the shorter CL XL729 kernels possibly hide between the longer CL XL745 kernels, similr to trends of the H/P co-mingles from both yers. In the 2012 H/H co-mingle, milling durtions required to ttin DOM level of 0.4% SLC differed by only 1 s between the two individul cultivrs (18 s for CL XL745 nd 17 s for CLXL729). Unlike the trends of the 2011 H/H co-mingle, milling durtions required by the 18

27 Tble 1.4. Reltionships [1] between surfce lipid content (SLC) nd milling durtion. Yer Co-mingle Co-mingling Rtio Asymptote ( 10-1 ) Scle Growth Rte ( 10-2 ) 2011 H/P 0: (CL XL745/ 10: CL 151) 25: : : : : H/H 0: (CL XL745/ 25: CL XL729) 50: : : P/P 0: (Wells/ 25: CL 151) 50: : : H/P 0: (CL XL745/ 10: CL 151) 25: : : : : H/H 0: (CL XL745/ 25: CL XL729) 50:

28 P/P (Wells/ CL 151) 75: : : : : : : [1] Regression nlyses of SLC s function of milling durtion were conducted on four replicte smples t 10, 20, 30 nd 40-s milling durtions using the prediction model SLC = + b e( c Milling durtion), where = Asymptote, b = Scle nd c = Growth rte. 25:75, 50:50 nd 75:25 rtios were slightly less thn those required by the individul cultivr lots to rech the trget DOM of 0.4% SLC (fig. 1.2b). In 2012, CL XL745 brown rice kernels were both longer nd wider thn those of CL XL729 with no difference in their TLCs. This might hve cused the 2012 CL XL745 nd CL XL729 cultivr lots to hve similr milling chrcteristics (overlpping SLC vs. milling durtion curves in fig. 1.1b). However, the slightly lesser milling durtions required by the 25:75, 50:50 nd 75:25 rtios in the 2012 H/H co-mingle suggest tht when these two cultivrs re co-mingled, the shorter nd nrrower CL XL729 kernels mill in tndem with the longer nd wider CL XL745 kernels. This cn be resoned to ffect the milling of co-mingled smples of these two cultivrs nd help them mill slightly fster or t similr rte to tht when the individul cultivr lots re milled seprtely. 20

29 Milling durtion (s) Milling durtion (s) Milling durtion (s) % CL XL745 () % CL XL745 (b) % Wells (c) Fig Milling durtions for the CL XL745/CL 151 (), CL XL745/CL XL729 (b) nd Wells/CL 151 (c) co-mingles in 2011 nd 2012, estimted using regression nlysis constnts in tble 1.4, t degree of milling level of 0.4% surfce lipid content. 21

30 In the 2011 P/P co-mingle, the 0:100 rtio, consisting of only CL 151, required slightly greter milling durtion (32 s) thn the 100:0 rtio, consisting of only Wells (30 s), to rech trget DOM of 0.4% SLC (fig. 1.2c). The predicted milling durtions incresed from the 0:100 rtio to the 25:75 rtio nd then decresed to the 50:50 rtio nd then remined more or less constnt. In 2011, CL 151 brown rice kernels were shorter nd wider nd hd greter TLC thn those of Wells (tble 1.2). Since the H/P co-mingle showed tht width my not ply n importnt role in influencing the milling of co-mingled smples contining different-tlc cultivrs, greter milling durtion required by the 25:75 rtio from the 2011 P/P co-mingle, like the 10:90 nd 25:75 rtios from the H/P co-mingle from both yers, gin points out tht when two cultivr lots, one with shorter nd greter-tlc kernels thn the other re co-mingled, in proportion where the shorter nd greter-tlc kernels re in excess, the milling durtion required to rech DOM of 0.4% SLC is greter thn tht required when the individul cultivr lots re milled seprtely. This might hppen becuse the shorter CL 151 kernels probbly hide between the longer Wells kernels, cusing the Wells kernels to mill fster thn the CL 151 kernels. In the 2012 P/P co-mingle, the predicted milling durtions required to ttin 0.4% SLC decresed to the 50:50 rtio nd then remined more or less constnt (fig. 1.2c). Unlike the 2011 P/P co-mingle, the 25:75 rtio did not require greter milling durtion thn the 0:100 nd the 50:50 rtios. Similr to trends in 2011, CL 151 brown rice kernels were shorter nd wider nd hd greter TLC thn those of Wells in 2012 (tble 1.2). Therefore, the bsence of greter milling durtion for the 25:75 rtio in the 2012 P/P co-mingle, s compred to trends of the 2011 P/P co-mingle, suggests tht there re fctors other thn co-mingling proportion, kernel dimensions nd TLC tht influence the milling chrcteristics of co-mingled smples. Bulk density of CL 151 ws greter thn tht of Wells in 2011 but in 2012, the trend ws reversed. 22

31 However, in the H/P nd H/H co-mingles from both yers, the trends in bulk densities of the individul cultivr lots used in these co-mingles remined constnt. Therefore, bulk density might be one of the fctors tht impcts the milling of co-mingled smples. The H/P nd P/P co-mingles suggest tht when there re differences in TLCs nd lengths of the cultivrs being co-mingled, milling durtion required by the co-mingle tht contins greter proportion of the cultivr with shorter nd greter-tlc kernels to rech DOM of 0.4% SLC is greter thn tht when the individul cultivr lots re milled seprtely. However, there ws no difference in the TLCs of CL XL745 nd CL XL729 brown rice kernels in both yers nd the 25:75 rtio still required greter milling durtion tht the other rtios in this co-mingle in In the 2012 H/H co-mingle, milling durtions required by the co-mingled smples were slightly less or close to those required by the individul cultivr lots when milled seprtely. This difference in trends of milling durtions required by the H/H co-mingles in 2011 nd 2012 ws probbly due the differing kernel dimensions of the two individul cultivrs over the two yers. In 2011, CL XL745 kernels were longer nd of equivlent width to those of CL XL729 while in 2012, CL XL745 kernels were longer nd wider thn those of CL XL729. Therefore, it cn be sid tht when the two cultivrs being co-mingled hve equivlent TLCs, widths of the brown rice kernels of the cultivrs being co-mingled impct the milling of co-mingles of these cultivrs. Trends in widths of the cultivrs used in the H/P co-mingle were reversed over the two yers, suggesting tht when TLCs of the cultivrs being co-mingled re different, width does not impct the milling of co-mingles. Lstly, the P/P co-mingle from 2012 suggested tht there re fctors other thn co-mingling proportion, kernel dimensions nd TLCs tht influence the milling dynmics of co-mingled smples. Bulk density might be one of these fctors s trends in bulk 23

32 densities of Wells nd CL 151 reversed over the two yers, but they remined sme for cultivrs used in the other two co-mingles. Milled rice yields of co-mingled smples Bsed on the liner regression nlyses of MRY vs. SLC, the resulting equtions nd R 2 vlues re presented in tble 1.5. MRYs djusted to DOM level of 0.4% SLC re presented in fig There were consistent trends in ll co-mingles cross both hrvest yers. As presented in fig. 1.3, MRYs incresed or decresed with the incresing percentge of prticulr cultivr in co-mingle. For instnce, in the H/P co-mingle from the 2011 hrvest, MRYs of the co-mingled smples incresed from 72.9% to 74.7% s the percentge of CL XL745 in the smples incresed from 0 to 100% (fig. 1.3). This cn lso be interpreted s decrese in MRYs of the co-mingled smples from 74.9% to 72.9% with n increse in the percentge of CL 151 in the smples. Similrly, MRY of the 2011 H/H co-mingle incresed from 72.3% to 74.1% s the percentge of CL XL745 in tht co-mingle incresed from 0 to 100% (fig. 1.3b). Likewise, MRY of the P/P comingle from 2011 incresed s the percentge of Wells in the co-mingle incresed, except for the 25:75 co-mingling rtio tht hd slightly less MRY thn the 0:100 rtio (fig. 1.3c). Similr trends were observed for the 2012 lots, with their MRYs being less thn those of the 2011 lots (fig. 1.3), becuse chlkiness of the 2012 lots ws greter thn tht of the 2011 lots. Chlky prts of the kernels re speculted to hve disintegrted during milling, thereby leding to lesser MRYs for the 2012 lots s compred to the 2011 lots. The 25:75 rtio from the 2012 P/P co-mingle, unlike the 25:75 rtio from the 2011 P/P co-mingle, lso followed the trend of the MRYs incresing with n increse in percentge of Wells in the co-mingle. Therefore, MRY of the 25:75 rtio from the 2011 P/P co-mingle not following the forementioned trend my be ttributed t lest in prt to experimentl error. 24

33 Tble 1.5. Reltionships [1] (SLC). between milled rice yield (MRY) nd surfce lipid content Co-mingle H/P (CL XL745/ CL 151) H/H (CL XL745/ CL XL729) P/P (Wells/ CL 151) Co-mingling Rtio Eqution R 2 Eqution R 2 0: SLC SLC.97 10: SLC SLC.96 25: SLC SLC.96 50: SLC SLC.97 75: SLC SLC.96 90: SLC SLC : SLC SLC.94 0: SLC SLC.98 25: SLC SLC.97 50: SLC SLC.95 75: SLC SLC : SLC SLC.94 0: SLC SLC.97 25: SLC SLC.97 50: SLC SLC.95 75: SLC SLC : SLC SLC.94 [1] Liner regression nlyses of MRY s function of SLC were conducted on four replicte smples milled for 10, 20, 30 nd 40-s durtions. 25

34 MRY (%) MRY (%) MRY (%) % CL XL745 () % CL XL745 (b) % Wells (c) Fig Milled rice yields (MRYs) of the CL XL745/CL 151 (), CL XL745/CL XL729 (b) nd Wells/CL 151 (c) co-mingles in 2011 nd 2012, estimted using the regression equtions presented in tble 1.5, t degree of milling level of 0.4% surfce lipid content. 26

35 MRY - Weighted Avg MRY MRY - Weighted Avg MRY To compre MRYs of the co-mingled smples to their weighted verge MRYs determined using the MRYs of the individul cultivr lots, the differences between MRYs nd weighted verge MRYs of the co-mingled smples re presented in fig Differences between the two were less thn ±0.5 percentge points for ll co-mingles cross both hrvest yers. Therefore, it cn be sid tht when two cultivrs re co-mingled in ny proportion nd milled to trget DOM of 0.4% SLC, the resulting MRY of the co-mingled smples will be very close to the weighted verge of the MRYs of the individul cultivr lots milled seprtely. CL XL745/CL 151 CL XL745/CL XL729 Wells/CL % First cultivr () Fig Differences between milled rice yields (MRYs) (fig. 1.3) nd weighted verge MRYs for ech co-mingle in 2011 () nd 2012 (b). % First cultivr is the percentge of the first cultivr in the co-mingle, i.e., CL XL745 in the CL XL745/CL 151 nd CL XL745/CL XL729 comingles nd Wells in the Wells/CL 151 co-mingle. Weighted verge MRY for ech co-mingled smple ws clculted using MRYs of the individul cultivr lots in tht co-mingle, s presented in tble 1.3. For e.g., the weighted verge MRY of the 10:90 rtio in the 2011 CL XL745/CL 151 co-mingle = (10 MRY of CL XL MRY of CL 151)/100 = ( )/100 = 73.1% Hed rice yields of co-mingled smples Bsed on the liner regression nlyses of HRY vs. SLC, the resulting equtions nd R 2 vlues re presented in tble 1.6. HRYs of the co-mingled smples djusted to DOM level of 0.4% SLC re presented in fig Like MRYs, there were consistent trends in HRYs of ll co % First cultivr (b)

36 mingles cross both hrvest yers. As presented in fig. 1.5, HRYs incresed or decresed with n incresing percentge of prticulr cultivr in co-mingle. For instnce, in the H/P co-mingle from the 2011 hrvest, HRYs decresed from 66.7% to 63.2% s the percentge of CL XL745 in the co-mingle incresed from 0 to 100% (fig. 1.5). Similrly, HRY of the H/H co-mingle from 2011 incresed from 61.2% to 61.9% with n increse in percentge of CL XL745 in the comingle (fig. 1.5b). Likewise, HRY of the P/P co-mingle from 2011 decresed from 66.7% to 59.7% with n increse in percentge of Wells in the co-mingle (fig. 1.5c). Similr trends were observed for the 2012 lots, with their HRYs being less thn those of the 2011 lots (fig. 1.5), becuse brown rice chlkiness of the 2012 lots ws greter thn tht of the 2011 lots, resulting in greter tendency for kernels to brek during milling becuse of reduced kernel strength. To compre HRYs of the co-mingled smples to their weighted verge HRYs determined using the HRYs of the individul cultivr lots, the differences between HRYs nd weighted verge HRYs re presented in fig In 2011, when HRYs of ll the individul cultivr lots were good (round 60% nd greter), differences between HRYs nd weighted verge HRYs of the co-mingled smples were less thn ±1 percentge point. Therefore, it cn be sid tht when two cultivrs with good HRYs re co-mingled in ny proportion nd milled to trget DOM of 0.4% SLC, the resulting HRY of co-mingled smples will be close to the weighted verge of HRYs of the individul cultivr lots milled seprtely. In 2012, when HRYs of ll the individul cultivr lots, except CL 151, were low (less thn 50%), differences between HRYs nd weighted verge HRYs of the co-mingled smples were between 0 nd -3.5 percentge points. Therefore, it cn be sid tht if co-mingle contins t lest one cultivr with low HRY nd is milled to trget DOM of 0.4% SLC, the resulting HRY of the co-mingle will be less thn the weighted verge of HRYs of the individul cultivr lots milled seprtely. In ll 28