Physical and Chemical Characterization of Fuel Ethanol Coproducts Relevant to Value-Added Uses

Transcription

1 Physil nd Chemil Chrteriztion of Fuel Ethnol Coproduts Relevnt to Vlue-Added Uses R. Bhdr, 1 K. Muthukumrppn, 1 nd K. A. Rosentrter 2,3 ABSTRACT Cerel Chem. 87(5): One of the fstest growing industries in the United Sttes is the fuel ethnol industry. In terms of ethnol prodution pility, the industry hs grown y more thn 600% sine the yer The mjor oproduts from orn-sed ethnol inlude distillers dried grins with solules (DDGS) nd ron dioxide. DDGS is used s livestok feed euse it ontins high quntities of protein, fier, mino ids, nd other nutrients. The gol of this study ws to quntify vrious hemil nd physil properties of DDGS, distillers wet grins (DWG), nd distillers dried grin (DDG) from severl plnts in South Dkot. Chemil properties of the DDGS inluded rude sh ( %), neutrl detergent fier (NDF) ( %), id detergent fier (ADF) ( %), rude fier (CF) ( %), rude protein ( %), rude ft ( %), nd totl strh ( %). Physil properties of the DDGS inluded moisture ontent ( %), A w ( ), ulk density ( kg/m 3 ), therml ondutivity ( W/m C), therml diffusivity ( mm 2 /se), olor L* ( ), * ( ), * ( ), nd ngle of repose ( ). These properties were lso determined for DWG nd DDG. We lso onduted imge nlysis nd size determintion of the DDGS prtiles. Cron group hrteriztion in the DDGS nd DDG smples were determined using NMR spetrosopy; O-lkyl omprised >50% of ll DDGS smples. Results from this study showed severl possiilities for using DDGS in pplitions other thn niml feed. Possiilities inlude hrvesting residul sugrs, produing dditionl ethnol, produing vlue-dded ompounds, using s food-grde dditives, or even using s inert fillers for ioomposites. The potentil inrese in the demnd for ethnol s fuel dditive nd s soure of lternte fuel hs resulted in rdil trnsformtion in griulture throughout the United Sttes. Aording to n RFA report, 15 illion ushels of orn ws produed in 2009, out of whih 4.2 illion ushels of orn went to the ethnol industry for ioethnol prodution ( In 2009, 200 mnufturing plnts in the United Sttes hd totl output prodution pity of 34 illion L (9 illion gl) of ethnol (RFA 2009). Sientists estimted tht >18 million metri tons of DDGS ws produed in The mount of orn used for the ethnol prodution nd the quntity of oproduts hs inresed 22-fold during pst 20 yers. Industril proessing of ethnol from orn is minly lssified into two types: wet milling nd dry milling. Wet milling filities re generlly orporte-owned nd hve high operting osts. In these, strh is isolted in pure form due to frtiontion of the orn kernel into strh, fier, germ, nd protein. Wet milling requires sophistited equipment, high energy, nd wter onsumption, nd yields oproduts suh s orn gluten feed (CGF), germ mel, orn gluten mel (CGM), nd rude orn oil (Johnson nd My 2003). The other proess for otining ethnol from orn is dry milling. Aording to n RFA (2009) report, 85% prodution of ethnol omes from dry milling, while only 15% omes from wet milling. The dry milling proess generlly does not utilize frtiontion (lthough tht is eginning to hnge), nd the primry oprodut is distillers dried grins with solules (DDGS). DDGS is dry grnulr form of the nonfermentle omponents fter orn fermenttion in ioethnol proessing plnts. The dry milling prodution proess usully onsists of severl unit opertions: grinding, ooking, liquefying, shrifying, fermenting, nd distilling the orn grin (Rosentrter 2006). More detils out this 1 South Dkot Stte University, Ag nd Biosystems Engineering, Brookings, SD. 2 Agriulturl nd Bioproess Engineer, North Centrl Agriulturl Reserh Lortory, USDA-ARS, Brookings, South Dkot. Nmes re neessry to report ftully on ville dt; however, the USDA neither gurntees nor wrrnts the stndrd of the produt, nd the use of the nme y the USDA implies no pprovl of the produt to the exlusion of others tht my lso e suitle. 3 Corresponding uthor. Phone: Fx: E-mil ddress: kurt.rosentrter@rs.usd.gov doi: / CCHEM AACC Interntionl, In. proess re ville (Tielius 1996; Weigel et l 1997; Jques et l 2003). After distilltion to remove the ethnol, the wet residuls re pressed or spun to remove exess wter y entrifugtion. One portion of the wter is removed, the wet ke is mixed with ondensed solule mterils nd then dried. This finl produt is DDGS (Rosentrter 2006). The solules re often referred to s syrup in the industry. This oprodut is high in vitmins, ft, nd protein ut low in fier. Syrup yields digestile energy vlue of 91% of tht of rw orn (Buhheit 2002 [ ~redi/grins/ftsheets/historyofethnolprodution.pdf]; Cruz et l 2005). It typilly ontins 28 46% dry mtter, 6 21% (d) ft, 18 22% (d) protein, nd 9 12% (d) minerls (Shingoethe 2001; Rosentrter nd Muthukumrppn 2006). DDGS is used lmost exlusively s livestok feed. Its nutritionl omponents, produt shelf-life, trnsporttion, nd flowility re vitl onsidertions for overll feed qulity. Chnges in the finl produt qulity ffet the overll ost of DDGS nd the eonomi viility of eh ethnol plnt. Reserh hs een relted to nutritionl properties (Spiehs et l 2002), physil properties (Rosentrter 2006), nd flowility properties of DDGS (Gnesn et l 2008,). DDGS hs lso een investigted s protein-rih ingredient for qufeeds (Chevnn et l 2007, 2008). Additionlly, sorption isotherms for vrying solule solid levels nd humidity levels were developed; this study oserved tht modified Hlsey nd modified exponentil models performed well for isotherm dt; however, the GMR model followed y new modified exponentil model were the est fit for DDGS (Gnesn et l 2007). Reserhers hve lso worked with using flow gents in DDGS to minimize flow restritions due to king of prtiles (Gnesn et l 2008). Thus vrious studies hve een onduted on DDGS yet there re other res in whih DDGS ould e used s vlue-dded produt, in ddition to its use s niml feed, e.g., removl of fier from DDGS, iodiesel prodution from orn oil, iomss gsifition, ellulosi degrdtion of DDGS (Bls et l 2006) for further ethnol prodution. However, to ddress these new res, omplete understnding of physil nd hemil properties of DDGS is required. Consequently, the ojetive of this study ws to quntify vrious physil nd hemil properties of DDGS, DWG, nd DDG to estlish thorough understnding of these oproduts, whih will produe novel uses for these mterils. Vol. 87, No. 5,

2 MATERIALS AND METHODS Smple Colletion In this study, smples of DDGS nd DWG were olleted from three ommeril fuel ethnol plnts (denoted s Plnt A, Plnt B, nd Plnt C) in the stte of South Dkot. Smpling ws done in two thes (Bth I nd Bth II) t two different dtes; one th eh of DDGS nd DWG were olleted in Septemer nd gin in Deemer. The DDGS smples were stored t room temperture (24 ± 1 C), while DWG smples were stored under refrigerted onditions (5 ± 1 C). DDG ws olleted from only one plnt; one th ws nlyzed for the sme properties s the DDGS nd DWG for omprison purposes. Experimentl Design nd Dt Anlysis The smples were sujeted to extensive physil nd hemil testing. For most properties in orresponding plnt nd th, five replites were mesured. Thus, n = 30 for eh property for eh produt strem ross ll plnts. For the determintions of rude ft (% d), rude protein (% d), nd totl strh (% d), however, only two replites were tken from eh plnt nd the orresponding thes (n = 12). Eh property ws studied using ompletely rndomized design. For eh physil nd hemil property, minimum, mximum, men, nd stndrd devition vlues were determined (Mirosoft Exel 2003, Redmond, WA). Additionlly, lest signifint differene (LSD) test ws performed for ll the physil nd hemil properties t 95% onfidene level using α = 0.05 (v.9.1, SAS Institute, Cry, NC) to test for differenes mong the plnts. Furthermore, plnt-wise omprisons were mde for eh DDGS nd DWG property to quntify vriility mong the ethnol plnts. Physil Properties Moisture ontent ws determined using Approved Method in fored onvetion lortory oven (Thelo Preision, Jovn, Winhester, VA) (AACC Interntionl 2010). Wter tivity ws mesured using lirted A w meter (Sprint TH 500, Novsin, Tlstrsse, Switzerlnd). Therml properties (ondutivity, diffusivity, nd resistivity) were determined with meter (KD2, Degon Devies, Pullmn, WA) tht utilized the line het soure proe TABLE I Plnt-Wise Comprison of DDGS Properties Plnt A Plnt B Plnt C Physil properties Moisture (% d) 4.61 (1.01) 4.98 (1.00) 5.18 (1.02) Wter tivity 0.47 (0.05) 0.45 (0.05) 0.52 (0.04) Bulk density (kg/m 3 ) (13.95) (12.89) (15.1) Angle of repose ( ) (10.23) (10.56) (9.23) Energy ontent (MJ/kg, d) (0.5) (1.52) (1.23) Therml ondutivity (W/m C) 0.07 (0.00) 0.12 (0.01) 0.06 (0.05) Therml diffusivity (mm 2 /se) 0.14 (0.1) 0.14 (0.14) 0.15 (0.12) Color L (2.56) (2.36) (2.86) Color 9.37 (1.05) (1.26) (1.24) Color (2.95) (2.45) (2.56) Chemil properties Crude protein (% d) (1.25) (1.20) (1.32) Crude ft (% d) (10.0) 9.75 (1.05) (0.95) Crude fier (% d) 9.93 (1.45) (1.23) (1.53) NDF (% d) (4.02) (3.95) (4.01) ADF (% d) (4.02) (3.95) (4.56) Totl strh (% d) (1.2) 9.81 (1.52) (1.42) Ash (% d) (3.01) (2.56) (3.05) Vlues followed y the sme letter re not signifintly different (P < 0.05). Vlues in prentheses indite ±1 SD. Eh property (n = 30 smples) sed on 5 replites nlyzed from 3 plnts olleted in 2 thes. Eh property (n = 12 smples) sed on 2 replites nlyzed from 3 plnts olleted in 2 thes. TABLE II Plnt-Wise Comprison of DWG Properties Plnt A Plnt B Plnt C Physil Properties Moisture (% d) (4.23) (3.25) (5.01) Wter tivity 0.97 (0.01) 0.95 (0.03) 0.98 (0.02) Bulk density (kg/m 3 ) (110.56) (112.36) (123.56) Therml ondutivity (W/m C) 0.12 (0.04) 0.13 (0.03) 0.14 (0.06) Therml diffusivity (mm 2 /se) 0.11 (0.02) 0.11 (0.04) 0.12 (0.03) Color L (4.12) (4.23) (4.56) Color 6.56 (1.12) 8.10 (1.56) 5.97 (1.03) Color (2.1) (1.95) (1.56) Chemil properties Crude protein (% d) (1.20) (1.02) (1.0) Crude ft (% d) 9.70 (1.00) (1.23) (1.56) Crude fier (% d) (1.53) (1.23) (1.56) NDF (% d) (4.12) (4.13) (4.56) ADF (% d) (3.95) (3.68) (3.56) Totl strh (% d) (1.53) (1.77) (1.23) Ash (% d) (3.10) (2.58) (1.56) Vlues followed y the sme letter re not signifintly different (P < 0.05). Vlues in prentheses indite ±1 SD. Eh property (n = 30 smples) sed on 5 replites nlyzed from 3 plnts olleted in 2 thes. Eh property (n = 12 smples) sed on 2 replites nlyzed from 3 plnts olleted in 2 thes. 440 CEREAL CHEMISTRY

3 tehnique (Bghe-Khndn et l 1981). Bulk density ws mesured using stndrd ushel tester (Seeduro Equipment, Chigo, IL) s desried y the USDA (1999). Color ws mesured using spetrophotoolorimeter (LSn XE, Hunter Assoites Lortory, Reston, VA) using the L,, opposle olor sles (Hunter Assoites). Angle of repose for DDGS nd DDG were determined s desried y Mohsenin (1980), where the DDGS nd DDG were llowed to fll onto 44-mm dimeter irulr plte. Gross energy ontent of DDGS nd DDG smples were mesured using om lorimeter (1260 Isoperioli, Prr Instrument, Moline, IL). For ll these properties, five replites were mesured. Prtile size distriution ws determined using Rotp sieve nlyzer (model RX-29, Tyler Mnufturing, Mentor, OH) for DDGS nd DDG, using three replites, nd the geometri men dimeter nd geometri stndrd devition for eh oservtion ws lulted using Stndrd Method S319.3 (ASAE 2004). For the DDGS smples only, mirosopi nlysis ws done for the prtiles from eh sieving sreen using n Olympus SZH10 stereomirosope with DP digitl mer (Leeds Instruments, Minnepolis, MN), followed y imge nlysis of the prtiles y Imge ProPlus (softwre version 4.0, Medi Cyernetis, Bethesd, MD) to determine the mximum dimeter, minimum dimeter, re, nd roundness using two replites for eh sreen from eh smple (Fig. 1). Chemil Properties Ash ontent ws determined using Approved Method (AACC Interntionl 2010). Aid detergent fier (ADF), neutrl detergent fier (NDF), nd rude fier nlysis ws done with fier nlyzer (model 200, Ankom Tehnology, Medon, NY). For these properties, five replites for eh smple were used. Protein ontent ws determined using Offiil Method nd ft ontent using Offiil Method (AOAC 2000). Totl strh ws mesured s in Xiong et l (1990), nd gluose ontent ws mesured using iohemistry nlyzer with sensor memrne (2700, YSI, Yellow Springs, OH) following method dpted from Knudsen (1997). Eh of these properties were determined using two replites only. Nuler mgneti resonne (NMR) spetrosopy ws onduted t South Dkot Stte University, Deprtment of Chemistry nd Biohemistry. NMR spetr were only done for DDGS (ll thes) nd DDG (Bth I only) using single replite for eh smple. RESULTS AND DISCUSSION Plntwise Comprisons Ethnol oproduts hve een reported to exhiit onsiderle vriility mong plnts (Rosentrter 2006, 2007). This held true for the smples in this study s well, s evidened y plntwise omprisons for eh DDGS nd DWG property. The LSD test (Fisher 1948) t 95% signifine level (α = 0.05) very lerly reveled tht there were signifint differenes for most of the properties mong the plnts (Tles I nd II), s well s within the thes of the sme plnt (not shown), for oth DDGS nd DWG. Differenes in the physil nd hemil properties n e due to vritions in the orn ultivr, in the proessing onditions, or in the simultneous effet of these two ftors. Previously, vritions were found minly in the DDGS rther thn in rw orn ultivrs (Belye et l 2004) nd sttistil orreltion showed little reltionship etween hemil omposition of the orn nd the DDGS. It ppers tht differenes rise mostly due to vritions in proessing prmeters ssoited with DDGS nd DWG prodution. For exmple, vrition in DDGS n our in the drying step, where DWG nd solules (CDS) re mixed. For our smples, we found vrition in the DWG smples (plntwise s well s thwise). This ould e due to vrition in the overll fermenttion proess, fermenttion time, enzyme ddition, entrifugtion, drying, strh degrdtion time, or other prmeters tht my vry from plnt to plnt s well s within plnt over time. All these ftors ould result in the vritions oserved mong the DDGS nd DWG smples otined from the three different plnts. Beuse DDGS is sold s livestok feed, vritions in the produt will ffet potentil mrket vlue (Rosentrter 2007). Moreover, if DDGS is onverted into vlue-dded mteril, it is even more importnt to hve onsistent produt, oth in terms of hemil omposition nd physil properties. Furthermore, physil properties re importnt for trnsporttion nd hndling of the oproduts. DDGS Physil Properties Overll physil properties of DDGS re shown in Tle III. The moisture ontent rnged from 3.54% d (minimum) to 8.21% d (mximum), with men vlue of 5.07% d. This low moisture ontent indites tht the DDGS ws dried well (for higher shelflife nd etter flowility) efore it ws sold in the feed mrket. This vlue differed somewht from moisture ontent dt otined Fig. 1. Mirosopi imges of DDGS (smples from plnt A only) illustrte vrying size nd shpe of DDGS prtiles. * Sieve opening size (mm). Vol. 87, No. 5,

4 y Rosentrter (2006) (men vlue 14.7% d), whih ws higher thn our findings. Stndrd devition ws <1.21% s well. Typilly, moisture ontents of <12% re reommended for storge, hndling, nd trnsporttion of feed produts. All DDGS in this study hd moisture ontents elow this threshold. This should help with long-term storge nd future vlue-dded pplitions. Moisture ontent nd solule levels will ffet the flowility of DDGS s well (Gnesn et l 2008). DDGS A w ws , with very low stndrd devition of The verge A w ws This vlue differed slightly from erlier results (Rosentrter 2005). The A w is defined s the vpor pressure of wter in iologil system divided y tht of pure wter t the sme temperture. It represents the mount of free wter ville for miroil tivity; the lower the A w vlue, the less prone the produt will e to miroil spoilge. Very low levels of A w prevent miroil spoilge nd inrese the shelf-life of the mteril, whih hve less hne of teril, fungl, nd yest growth t A w < 0.7 (Bros-Cnovs nd Veg-Merdo 1996). Bulk density ws kg/m 3, with men vlue of kg/m 3. It hd stndrd devition of Although this vriility ppered somewht high ompred to the other physil properties, y onsidering this in reltion to the ulk density men vlue, the resulting oeffiient of vrition ws tully reltively low (3.1%). The stndrd devition ws less thn tht reported y Rosentrter (2006). Bulk density dittes the effetive storge pity for ins nd silos; it inludes oth the mteril volume s well s the enlosed ir spes etween prtiles. Bulk density reported here is lso known s the loose ulk density. But mesure of ulk density with n pplied externl perturtion is lled the tpped ulk density nd gives loser representtion of the ehvior of the mteril in n industril senrio. The ngle of repose ws with n verge vlue of The men vlue ws very lose to tht in Rosentrter (2006). However, the rnge of vlues in this urrent study ws roder thn the dt otined y Rosentrter (2006). This indites higher vriility mong the plnts nd the thes in this study. Finer prtiles were otined in our findings, whih ould ffet the flowility of DDGS nd my inrese the possiility of king (Gnesn et l 2008). Angle of repose indites grin struture: the higher the ngle of repose, the lower the potentil flow rte euse the ngle of frition etween the prtiles is greter. Differenes mong ngle of repose vlues re dependent on the milling prmeters nd other proessing steps used y n individul plnt, nd it my differ sustntilly from one plnt to nother. The energy ontent of DDGS ws MJ/kg. This rnge of energy ontent ws very lose to tht in Morey et l (2006). Thus, it ppers tht DDGS my prove useful s feedstok for onversion y gsifition or other thermohemil proesses. In ft, DDGS ould e used to provide energy to the ioethnol proess itself (Morey et l 2006). The energy ontent of orn stover is less thn tht of DDGS. But omintion of DDGS nd orn stover ould provide lned pproh to generte eletriity nd would e eonomilly fesile (Morey et l 2006). On the other hnd, euse DDGS is used extensively s livestok feed, this diversion would redue the mount of feed ville (Morey et l 2006). Therml ondutivity ws W/m C, with smll vritions (stndrd devition of 0.01), while nd therml diffusivity ws mm 2 /se (with low stndrd devition of 0.01). These vlues were very lose to the results of Rosentrter (2006). Therml properties re inherent to the mteril nd thus less prone to vritions mong the plnts or etween thes. For olor prmeters, Hunter L vlue ws (men vlue of 42.3); Hunter vlue ws (men vlue of 9.65); nd Hunter ws (men vlue of 20.62). Differenes in the rnges of the three olor sles were ompred to those found y Rosentrter (2006). In this study, we otined wide rnge of olor vlues. This indites muh vrition mong the thes, s well s etween the proessing plnts. Color vlues my possily e relted to the nutritionl hrteristis of the smples (Goihl 1993; Ergul et l 2003), lthough this hs to e estlished definitively. Rosentrter (2006) found orreltions etween Hunter olor TABLE III Overll Physil nd Chemil Properties of DDGS Minimum Mximum Men Stndrd Devition Physil properties (n = 30 for eh property) Moisture (% d) Wter tivity Bulk density (kg/m 3 ) Angle of repose ( ) Energy ontent (MJ/kg, d) Therml ondutivity (W/m C) Therml diffusivity (mm 2 /se) Color L Color Color Chemil properties (n = 30 for eh property) Crude sh (% d) NDF (% d) ADF (% d) Crude fier (% d) Crude protein (% d) Crude ft (% d) Totl strh (% d) Gluose (% d) Cron prtitioning (%) Alkyl (0 50 ppm) O-Alkyl ( ppm) Aromti ( ppm) Croxyl ( ppm) Cronyl ( ppm) Eh property (n = 30 smple), sed on 5 replites nlyzed from 3 plnts olleted in 2 thes. Eh property (n = 12 smple), sed on 2 replites nlyzed from 3 plnts olleted in 2 thes. Eh property (n = 6 smple), sed on 1 replite nlyzed from 3 plnts olleted in 2 thes. 442 CEREAL CHEMISTRY

5 prmeters nd other physil properties. For exmple, Hunter nd vlues hd high orreltions with A w nd moderte orreltions with therml properties. Physil properties of the DDGS re relted to flow properties. Prtile shpes, sizes, edges, moisture ontent, ngle of repose (nd thus fritionl hrteristis), nd ulk density re some key prmeters tht influene flow nd trnsporttion ehvior. Cking nd stikiness re ommon prolem for the trnsporttion nd logistis of DDGS (Gnesn et l 2008). Cking is n dded urden for the DDGS mrket, where dditionl ost is neessry for reking the onsolidted prtiles. Not only do physil properties ply role, hemil properties re lso importnt to the flowility of DDGS, s well s future nd vlue-dded opportunities. DDGS Chemil Properties The results for hemil properties re shown in Tle III. The gretest onstituent ws NDF (with men vlue of 36.74% d), then rude protein (men of 29.93% d) followed y ADF (men vlue of 16.2% d), rude sh (men of 12.82% d), totl strh (men vlue 11.07% d), totl ft (men of 10.5% d), rude fier (men of 10.22% d), nd then gluose (men of 0.84% d). Crude sh ws % (d). The verge sh ontent ws higher ompred to the results otined of Spiehs et l (2002), nd our results showed roder rnge of sh ontent. This indites vritions in the mount of minerls mong the proessing plnts where our smples were olleted. Beuse the plnts were loted t different ples, vrition mong the orn types, whih in turn depends on the soil properties nd minerl vilility, ould e one possile reson for the rod rnge of sh ontent. However, it hs een reported tht the rtios of the DWG used nd CDS dded to during proessing, s well s fermenttion proesses will influene the nutritionl properties more thn soil ehvior nd fertility (Spiehs et l 2002). NDF rnge ws % d. ADF rnge ws % d. The rude fier (CF) ws % d. NDF nd rude fier ontent vlues re slightly higher thn those found y Spiehs et l (2002). ADF vlues were very similr, however. NDF is the sum of the ADF nd the hemiellulose ontent, wheres ADF is the sum of ellulose nd lignin. This tegory of fiers (NDF, ADF, nd CF) is generlly lled insolule fier ontent. Crude fier n e determined y sutrting the ADF vlue from the NDF ontent. This sutrtion is not ompletely urte, ut vlue lose to rude fier is rehed (Test Diet 2006, Fier. Aville online t: Compred to Speihs et l (2002), it is evident tht our smples showed higher mount of hemiellulose euse they showed higher NDF nd CF ontents, ut similr ADF ontents. The differene of NDF vlue from the ADF indites the presene of higher mount of hemiellulose ontent in the DDGS. Our results lso indited higher verge NDF vlue thn the protein ontent (29.93% d), whih mens our DDGS smples were higher in overll ellulose, lignin, nd hemiellulose. These results suggest tht DDGS ould possily e vile sustrte for further enzymti hydrolysis (y reking down the fier) to yield further ethnol. The presene of ellulose nd hemiellulose ould e utilized y pproprite enzymes (i.e., ellulses nd hemiellulses) to form gluose, whih n e further onverted y fermenttion into ethnol. In ft, few studies hve egun to exmine the potentil to onvert the fier portion into ethnol (Mosier et l 2005; Kim et l 2008,). Another oservtion ws the reltive high presene of strh in the DDGS. It is true tht 100% of the strh n not e prtilly onverted to ethnol in typil ethnol plnt, nd the residul strh will ultimtely pss to the oprodut strem. If DDGS is sujeted to enzymti degrdtion with ellulse nd hemiellulses to yield ethnol, then the ddition of mylse would lso onvert the leftover strh to gluose, then to ethnol. The lrge protein moleules nd the presene of unknown inhiitory proteses n possily inhiit the fermenttion proess. Deproteiniztion studies ould eluidte further spets of this prolem nd ould help in reduing the issue of the prtil strh onversion. The presene of gluose, even in smll quntities, reveled tht the fermenttion effiieny of the ethnol plnts in this study ws not 100%. The ethnol prodution proess onsists of multistep enzymti retions, where the orn strh is onverted to gluose, nd then to ethnol y the Emden-Meryerhof-Prns pthwy (Kelsll nd Lyons 2003). Key steps inlude geltiniztion (αmylse reks the strh to give ess to the enzymes), liqueftion (strh is onverted to dextrin), shrifition (whih yields gluose moleules y gluomylse), nd fermenttion y yest to yield ethnol. The onversion of gluose to ethnol is n neroi loholi fermenttion step (Kelsll nd Lyons 2003). The presene of gluose in the DDGS strongly suggests tht the ethnol prodution proess ws unle to onvert ll fermentle sugrs. Chnges in the fermenttion tempertures, ph, strins, nd enzyme tivities re possile resons why the proess ws not 100% effiient. DDGS NMR Spetrosopy Nuler mgneti resonne (NMR) revels the nture of the ompounds present in iomterils (Fig. 2). The results of ron prtitioning through NMR spetrosopy is shown in Tle III. Averged over ll the smples, the highest C-group ws O-lkyl with n verge 52.81%, followed y lkyl (men of 28.86%), romti (men of 10.75%), roxyl (men of 7.56%), nd ronyl (men of 0.11%). These trends were irrespetive of plnt nd smpling time. To dte, no previous studies with NMR spetrosopy hve een done for DDGS. These results indite the nture of the ompounds present nd possile vlue-dded uses tht ould e developed from DDGS in the future. Alkyl (CH 3 O) groups re results of the deprotontion from the lohol moleules (Flether 1974). A high numer of lkyl groups indite the presene of stright-hin ompounds suh s simple rohydrtes nd possily lkoxyl groups. However, romti ompounds were not found in high mounts. Aromti ompounds re mde of enzene rings, usully found in seondry plnt metolites like rotenoids, shikimi ids, plnt steroids, et. (Trevor 1975). Thus, reltively lower perentge of these ompounds indites tht it would proly not e effiient to use DDGS for hrvesting phrmeutil ompounds suh s ntioxidnts, rotenoids, or other suh vlue-dded moleules (whih onsist of romti ring strutures). Phytosterols, romti nutreutil ompounds, ontined in the fier portion of the DDGS euse phytosterols re found in the ell wlls nd firous tissue of orn kernels. Most of these phytosterols were ssoited with the perirp lyer (Singh et l 2001). But dditionl studies showed low mount of phytosterols reovered in the spirted (fier-rih) prt of frtionted DDGS (Singh et l 2001). This indites tht using DDGS s soure of nutreutils my e diffiult with DDGS due to low onentrtions of these romti ompounds. Biodiesel is n ester tht n e produed from vegetle oils, niml fts, lge, or even reyled greses. It is ommonly used s fuel dditive in truks nd other vehiles (USDOE Aville online t: The presene of hrged lkoxyl groups nd ftty id levels suggest proility of utilizing suh esters from DDGS (Hssner 2002). Biodiesel prodution from DDGS is onept tht hs egun to grner interest (Hs et l 2007). The presene of hydrorons would fvor the gsifition of DDGS, whih is the onversion of iomss to gs mixture of hydrogen, methne, nd ron monoxide (USDOE 2008). Furthermore, DDGS itself my prove fvorle for more ethnol prodution using enzymti hydrolysis of the fiers, due to the higher mounts of rohydrte ompounds tht re present. On the other Vol. 87, No. 5,

6 hnd, higher O-lkyl groups with hrged eletrons on the oxygen moleules my enhne the inding properties of DDGS, nd it my e le to e used in ioomposites s iofillers. Severl studies hve suessfully used DDGS in plsti omposites (Ttr et l 2007; Cheesrough et l 2008; Ttr et l 2009). DDGS Prtile Size nd Imge Anlysis The results of the imge nlysis re shown in Tle V. There were mny differenes in the size nd shpe prmeters (i.e., minimum dimeter, mximum dimeter, re, nd roundness) for vrious size frtions. For eh plnt, prtiles were smpled from different sreens from no. 8 (2.38 mm) to no. 100 (149 µm). Geometri men dimeter, or medin size (d gw ), ws highest in Plnt C, followed y Plnt A, then Plnt B. Stndrd geometri devition (S log ) ws greter in Plnt A, followed y Plnt C, then Plnt B. Prtile dimeters were mm for Plnt A, nd mm for Plnt B, for Plnt C they were mm. The highest verge re ws in prtiles from Plnt C (16.70 mm 2 ). For the other two plnts, the vlues of verge res were quite similr (5.11 nd 5.06 mm 2 ). Roundness is the degree of rsion of grin prtile, s shown y the shrpness of its edges nd orners. By roundness, we men either the spheriity of three-dimensionl ody, or the irulrity of two-dimensionl figure (Cox 1927). The spheriity of three-dimensionl ody my e expressed y the degree to whih the rtio of its volume to its surfe re pprohes tht of sphere. For two-dimensionl prtiles, it is mesured y the degree to whih the rtio of the re to the irumferene pprohes tht of irle. It is expressed mthemtilly s K = A 4π/(Pr) 2, where A is the re, P is the perimeter, r is the prtile rdius, nd K is onstnt. The K onstnt depends on the shpe of the prtile; K =1 for irle or sphere, ut <1 for ny other shpe. K represents the perentge rtio (%) of the prtile re to tht of irle with the sme perimeter (Cox 1927). For exmple, if K is 0.78 of squre, it mens tht squre ontins just 78% of the re tht irle with the sme perimeter would ontin. Thus, the higher the roundness vlue, the more regulr nd smooth the edges of the ojet. The highest roundness vlues were in Plnt A (64.30%), then Plnt C (56.61%), followed y Plnt B (31.30%). From these findings, we n sy tht the DDGS from Plnt A nd Plnt C hve more round edges thn Plnt B. A roundness rtio from 96 80% is lled well rounded ojet; 95 74% is lled firly well rounded ojet; nd 83 60% is lled ngulr (Cox 1927). Not surprisingly, DDGS prtiles were irregulr, ngulr prtiles. More irregulrity on the edges (i.e., roughness) would possily fvor using these prtiles in omposites. The prtiles from the Plnt B hve lower roundness rtios nd thus hve suffiient roughness on the edges. Lrge prtiles were from Plnt C, whih hd the highest re nd mximum dimeter. Lrge prtile sizes fvor use in ioomposites ut lower roundness vlues (56.61%), would not fvor essentil lok nd key mehnisms required to form omposites, thus inders my e neessry for these prtiles s well. TABLE IV Overll Physil nd Chemil Properties of DDG Minimum Mximum Men Stndrd Devition Physil properties (n = 5 for eh property) Moisture (% d) Wter tivity Bulk density (kg/m 3 ) Angle of repose ( ) Energy ontent (MJ/kg, d) Therml ondutivity (W/m C) Therml diffusivity (mm 2 /se) Color L Color Color Chemil properties (n = 5 for eh property) Crude sh (% d) NDF (% d) ADF (% d) Crude fier (% d) Crude protein (% d) Crude ft (% d) Totl strh (% d) Gluose (% d) Cron prtitioning (%) (n = 1 for eh property) Alkyl (0 50 ppm) O-Alkyl ( ppm) Aromti ( ppm) Croxyl ( ppm) Cronyl ( ppm) Eh property (n = 5 smple), sed on 5 replites nlyzed from 1 plnt olleted in 1 th. Eh property (n = 2 smple), sed on 2 replites nlyzed from 1 plnt olleted in 1 th. Eh property (n = 1 smple), sed on 1 replite nlyzed from 1 plnt olleted in 1 th. TABLE V Size nd Shpe Results for DDGS Prtiles Plnt D gw (mm) S gw (mm) D mx (mm) D min (mm) Are (mm 2 ) Roundness (%) A B C D gw, geometri men dimeter; S gw, geometri stndrd devition y mss; D mx, mximum dimeter of prtiles (mm); D min, minimum dimeter of prtiles (mm). Vlues followed y the sme letter re not signifintly different (P < 0.05). Eh property (n = 6 smple) from eh plnt, sed on 2 thes olleted from eh plnt, 3 replites nlyzed per th. Eh property (n = 4 smple) from eh plnt, sed on 2 thes olleted from eh plnt, 2 replites nlyzed per th. 444 CEREAL CHEMISTRY

7 Flowility of powders depends on interprtile frition, whih is dominted y prtile shpe, size, nd surfe roughness. As the surfe roughness inreses, the interprtile frition inreses nd lessens effiient flow. For ll prtile sizes exmined, imge nlysis nd prtile size determintion reveled tht there were fewer differenes mong the DDGS prtiles etween the thes nd more differenes for prtiles olleted from different plnts. Grin size nd prtile shpe depend very muh on the proessing mhines used y the plnts, nd these differ from one plnt to nother ut not etween thes within prtiulr plnt. DDG Physil Properties Physil properties of DDG re shown in Tle IV. Moisture ontent of DDG ws % d. This ws muh less thn the moisture ontent of DDGS, whih ws %. It ws lso less thn the level of moisture ontent required for sfe storge, whih is 12%. With inreses in moisture ontent, there hve een prolems in the flowility of DDGS (Gnesn et l 2008). Our results indite tht DDG should e suitle for long-time storge nd should hve sound flowility nd hndling hrteristis. The A w ws very low t This vlue ws less thn tht of DDGS (0.48). Low A w will prevent miroil spoilge nd should filitte long-term storge nd hndling (Rosentrter 2006). The ulk density ws kg/m 3. Bulk density of the DDG ws less thn tht of DDGS ( kg/m 3 ). DDGS does hve dditionl solule mteril, ut DDG does not, whih ould explin why the density of DDGS is higher thn the DDG (Gnesn et l 2008). The ngle of repose ws The mximum vlue ws lower in DDG thn DDGS, nd therefore DDG is potentilly more free-flowing thn DDGS. This my e possile euse DDG does not hve the dditionl solule ft lyers on the surfe of the prtiles, whih would ffet the fritionl hrteristis of the prtiles nd thus the ngle of repose. The energy ontent of DDG ws slightly higher thn DDGS, with n verge of 21 MJ/kg. Normlly, due to reltively high ft ontent in DDGS, the energy ontent should e higher thn DDG. Beuse DDG ws only from one plnt (nd one th), there ould e possiility of insuffiient smpling. Also, the slightly higher protein ontent in DDG (men vlue of 30.9% d) ould e nother possile reson for the higher energy ontent. Therml ondutivity ws W/m C nd diffusivity ws within mm 2 /se. These rnges of therml properties for DDG were very ner those otined for DDGS, ut the vrition oserved ws muh less for the therml properties of the DDG. Hunter L vlue ws ; Hunter vlue ws ; Hunter ws from The vlues of the olor sles differed sustntilly from those for the DDGS. This is result of different proessing onditions nd different nutritionl hrteristis thn DDGS, nd is due to the sene of CDS (Goihl 1993; Ergul et l 2003). DDG Chemil Properties Chemil properties of DDG re shown in Tle IV. The gretest onstituent ws NDF (verge vlue 31.43% d), then rude protein (verge vlue 30.9% d), followed y ADF (verge vlue 28.69% d), rude fier (verge vlue 12.33% d), totl strh (verge vlue of 11.01% d), rude sh (verge vlue 10.91% d), rude ft (verge vlue 8.9% d), then gluose (men vlue of 0.21% d). The NDF ontent ws % d. Thus, the NDF levels were very lose to those in DDGS. However, the verge NDF vlue of DDG (31.43% d) ws little lower thn the verge NDF ontent of DDGS (36.74% d). ADF vlue ws % d. Thus, the ADF ontent in DDG ws lmost doule tht of DDGS. Beuse NDF is the sum of ADF nd hemiellulose, the higher ADF vlue indites lower mount of hemiellulose in DDG ompred to tht in DDGS euse the NDF vlues were very similr. Thus, DDG hd higher ellulose nd lignin vlues. So degrdtion with only hemiellulse enzymes my not yield suffiient gluose moleules if DDG is sujeted to single enzymti degrdtion for future vlue-dded uses (suh s onversion to dditionl ethnol). Crude protein of DDG ws % d. It ws slightly higher thn in DDGS euse the DDGS is formed y inorportion of CDS, whih is high in ft ompounds. The ft ontent of DDG ws % d. These result prlleled the findings of Gnesn et l (2008). As suspeted, the ft ontent ws lower in DDG thn in DDGS euse there ws no dded CDS. The totl strh ontent of the DDGS ws % d. This rnge ws quite lose to tht of DDGS ut the mximum vlue ws higher in DDGS (14.04% d). Agin, due to similr proessing tehniques, DDG nd DDGS hd similr strh levels. However, the presene of very little gluose in the DDG would e due to resons similr to tht for DDGS: oth oproduts me from similr fermenttion proess. TABLE VI Overll Physil nd Chemil Properties of DWG Minimum Mximum Men Stndrd Devition Physil properties (n = 30 for eh property) Moisture (% d) Wter tivity Bulk density (kg/m 3 ) Therml ondutivity (W/m C) Therml diffusivity (mm 2 /se) Color L Color Color Chemil properties (n = 30 for eh property) Crude sh (% d) NDF (% d) ADF (% d) Crude fier (% d) Crude protein (% d) Crude ft (% d) Totl strh (% d) Gluose (% d) Eh property (n = 30 smple), sed on 5 replites nlyzed from 3 plnts olleted in 2 thes. Eh property (n = 12 smple), sed on 2 replites nlyzed from 3 plnts olleted in 2 thes. Vol. 87, No. 5,

8 DDG NMR Spetrosopy Cron prtitioning of DDG (Tle IV) ws quite similr to the DDGS results. The highest rtio ws in the O-lkyl group (50.08%), followed y lkyl (27.46%), romti (15.15%), roxyl (7.11%), nd ronyl (0.18%). DDG ould lso e used for ioomposites or enzymti hydrolysis due to high rohydrtes nd hrged lky groups. The romti group ws it higher in DDG thn DDGS. However, new studies should exmine DDG from multiple plnts over time to fully exmine these funtionl groups. DWG Physil Properties Vlues of physil properties of DWG re given in Tle VI. The moisture ontent of DWG ws % d nd ws very muh higher thn DDGS, whih ws expeted euse DWG is the wet form of DDG. There were differenes in moisture ontent mong the plnts s well etween the thes. Higher moisture ontent in DWG retes prolem in trnsporttion, storge, nd shipping. The A w ws 0.96 ( ). High A w filittes rpid miroil spoilge. The A w vlues >0.9 foster mold, teril, nd other fungl growth in iomterils. Thus, long-term storge nd long-distne trnsporttion is not fvorle. Bulk density of DWG ws kg/m 3. Bulk density ws greter for DWG thn for DDGS, whih ws due to the greter quntity of wter moleules in DWG. DWG hd greter therml ondutivity (verge vlue 0.12 W/m C) nd therml diffusivity (verge vlue 0.11 mm 2 /se) thn DDGS. This ws lso due to higher wter levels in the DWG. Thus, unlike DDGS, DWG my e hllenging for further hemil proessing or other vlue-dded uses euse it shows higher ondutivity, A w, nd ulk density. Men L,, vlues were 50.94, 6.91, nd 23.75, respetively, nd thus DWG ws slightly righter thn DDGS euse the DDGS hs een sujeted to drying opertions. DWG Chemil Properties Chemil property results for DWG re provided in Tle VI. There ws firly high fier ontent in the DWG smples. The gretest onstituent ws NDF (men vlue 33.80% d), followed y rude protein (men vlue 28.62% d), ADF (men vlue 14.22% d), rude sh (men vlue 13.31% d), rude fier (men vlue 12.04% d), totl strh (men vlue 11.24% d), rude ft (men vlue 11.12% d), nd gluose (men vlue 0.66% d). DWG showed very similr mounts of fier nd protein s DDGS. The totl strh ontent of DWG ws quite similr to DDGS s well. CONCLUSIONS The min ojetive of this study ws to exmine vrious physil nd hemil properties of DDGS, DDG, nd DWG, inluding imge nlysis nd NMR spetrosopy. The min ide ws to provide n overll piture of these oproduts whih will ffet end-use options. Chemil dt re essentil for livestok diet formultions ut they re lso importnt for pursuing other potentil uses suh s humn foods, ioenergy, ioomposites, or even for hrvesting of importnt nutreutil moleules, to nme few. Physil property informtion, on the other hnd, is ritil for the design nd opertion of proessing equipment (suh s dryers, onveyors, mixers, pellet mills, extruders, et.), proessing filities, nd storge strutures (suh s flt storge uildings nd vertil silos). LSD testing showed differenes in the properties mong three plnts, whih ws not surprising. This study highlights the neessity for simultneous optimiztion etween vrious physil nd hemil properties, nd the need for onsisteny of the oproduts mong plnts nd etween thes in given plnt. ACKNOWLEDGMENTS We would like extend grtitude to the ethnol plnts tht ontriuted oprodut smples, Agriulturl Experiment Sttion t South Dkot Stte University nd USDA-ARS for providing equipment nd finnil support, nd we would like to thnk Mihel Heldrith, Deprtment of Miroiology, South Dkot Stte University, for lortory ssistne with prtile imging. Fig. 2. NMR spetr for DDGS nd DDG (n = 1 for eh th from eh plnt); x-xis ppm units. Cron prtitions of lkyl (0 50 ppm), O-lkyl ( ppm), romti ( ppm), roxyl ( ppm), nd ronyl ( ppm). 446 CEREAL CHEMISTRY

9 LITERATURE CITED AACC Interntionl Approved Methods of Anlysis, 11th Ed. Methods nd Aville online only. AACC Interntionl: St. Pul, MN. AOAC Offiil Methods of Anlysis of the Assoition of Anlytil Chemists nd The Assoition: Githersurg, MD. ASAE Stndrds, Engineering Prties, Dt, 51st Ed. S19.3. The Soiety: St Joseph, MI. Bghe-Khndn, M., Choi, S. Y., nd Okos, M. R Improved line het soure therml ondutivity proe. J. Food Si. 46: Bls, B., Dle, B., nd Bln, V Enzymti hydrolysis of distillers dry grin nd solules (DDGS) using mmoni fier expnsion pretretment. Energy Fuels 20: Bros-Cnovs, G. V., nd Veg-Merdo, H Dehydrtion of Foods. Interntionl Thomson Pulishing: New York. Belye, R. L., Rush, K. D., nd Tumleson, M. E Composition of orn nd distillers dried grin with solules from dry grind ethnol proessing. Bioresoure Tehnol. 94: Buhheit, J. K Distillers dried grins with solules. Report No.11. I-FARM. Online t ethnolprodution.pdf. Southern Illinois University: Crondle, IL. 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ASABE 51: Gnesn, V., Rosentrter, K. A., nd Muthukumrppn, K Effet of moisture ontent nd solule levels on the physil nd hemil properties of DDGS. Cerel Chem. 85: Gnesn, V., Muthukumrppn, K., nd Rosentrter, K Effet of flow gent ddition on physil properties of DDG with vrying moisture ontent nd solule perentges. Trns. ASABE 51: Goihl, J Color, odor good inditors of DDGS nutritionl vlue. Feedstuffs 65(21):1. Hs, M. J., Sott, K. M., Fogli, T. A., nd Mrmer, W. N The generl ppliility of in situ trnsesterifition for the prodution of ftty id esters from vriety of feedstoks. J. AOCS 84: Hssner, A Orgni Syntheses Bsed on Nme Retion, 2nd Ed. Pergmon Pulishers: Amsterdm. Jques, K. A., Lyons, T. P., nd Kelsll, D. R Alohol Textook. University Press: Nottinghm, UK. Johnson, L. A., nd My, J. B Wet milling: The sis for orn iorefineries. Pges in: Corn Chemistry nd Tehnology, 2nd Ed. P. J. White nd L. A. Johnson, eds. AACC Interntionl: St. Pul, MN. Kelsll, D. R., nd Lyons, T. 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L Improved enzymti method to mesure proessing effets nd strh vilility in sorghum grin. J. Anim. Si. 63:3861. [Reeived Ferury 2, Aepted April 1, 2010.] Vol. 87, No. 5,