Effect of Cross-Linked Resistnt Strch on Whet Tortill Qulity J. N. Alviol, 1 T. Jondiko, 1 nd J. M. Awik 1,2 ABSTRACT Cerel Chem. 87(3):221 225 Resistnt strch (RS) ingredients re n ttrctive option to increse dietry fiber in bked products. This study determined the effect of two forms of cross-linked nd pregeltinized cross-linked RS, (Fsym) or (FRite), respectively, from whet on dough nd tortill qulity nd cceptbility. Refined whet tortills with 0% (control) to 15% RS (flour bsis) were mde using stndrd bking process. Tortills with 100% whole white whet were lso mde. Physicl nd rheologicl properties of dough nd tortills, nd sensory profile of tortills were evluted. Dough with whole whet nd 15% FRite were significntly hrder nd less extensible thn the control dough; this ws relted to high wter bsorption of these doughs. Tortills with whole whet nd 10 15% FRite were less puffed nd denser thn the control; however these levels of FRite significntly incresed tortill weight (by up to 6.2%). Dough nd tortills with Fsym were comprble to the control. Dietry fiber (g/100 g, db) incresed from 2.8 ± 0.3 in control to 14.3 ± 0.5 nd 13.6 ± 0.5 in 15% Fsym nd 15% FRite tortills, respectively. Tortills with whole whet were less cceptble thn the control in ppernce, flvor, nd texture, while tortills with 15% Fsym hd higher overll cceptbility thn the control. Incorportion of 15% cross-linked whet RS to increse tortill dietry fiber is fesible without negtively ffecting dough hndling nd tortill qulity. Resistnt strch (RS) is strch or its hydrolysis by-products tht re not bsorbed in the smll intestine but re prtilly or completely fermented in the lrge intestine (Chmp et l 2003; Higgins 2004). Short-chin ftty cids (SCFA), which re the min fermenttion products of RS, my improve colonic musculr ctivity, regulte pthogen popultion nd increse clcium bsorption (Topping et l 2003). Other possible helth benefits of RS include inhibition of tumor cells through butyrte production, enhncement of growth of beneficil bcteri in the colon (i.e., RS s prebiotic), nd improved glycemic nd insulinemic responses (Shrm et l 2008). RS cn be found nturlly in strch-rich products in the form of physiclly inccessible strch, grnulr strch, or retrogrded strch (Topping et l 2003). However, digestibility of nturlly occurring RS chnges with processing conditions, mylose to mylopectin rtio, nd food prticle size (Liljeberg et l 1996; Akeberg et l 1998; Kle et l 2002; Shrm et l 2008). On the other hnd, commercilly produced cross-linked RS (referred to s type 4 RS, or RS4) hve n dvntge of stbility during processing. The RS4 strches lso hve very high DF content (up to 100% DF) (Woo nd Seib 2009; Woo et l 2009), which llows for gret flexibility in product formultion. Adding RS ingredients into bked product improves its nutritive profile by incresing dietry fiber content nd providing ssocited helth benefits. RS ingredients hve n dvntge over trditionl high-fiber ingredients becuse they generlly hve low wter-holding cpcity, do not significntly ffect dough hndling properties, re blnd in flvor, hve smll prticle size, nd my even improve the texture of the finl product (Bixuli et l 2008; Shrm et l 2008). Flour tortills hve moved from being n ethnic (Hispnic) commodity to being prt of typicl Americn diet. Verstility, convenience, nd tste mke tortills highly cceptble to consumers. This populrity nd cceptnce mke tortills good cndidte for dietry fiber fortifiction nd powerful strtegy to promote helthy eting. Unfortuntely, mny consumers re turned off by dull ppernce nd hrsh flvors of whole grin or brnfortified products. Whet brn nd other cerel fibers lso tend to 1 Cerel Qulity Lbortory, Dept. of Soil nd Crop Sciences, Texs A&M University, College Sttion, TX 77843-2474. 2 Corresponding uthor. Phone: 979-845-2985. Fx: 979-845-0456. E-mil ddress: jwik@g.tmu.edu doi:10.1094/ CCHEM-87-3-0221 2010 AACC Interntionl, Inc. hve high wter-holding cpcity, which negtively ffects dough mchinbility nd tortill qulity (Seethrmn et l 1994). Resistnt strch my provide convenient nd functionl source of dietry fiber for consumers who prefer the sensory properties of refined flour tortills. However, so fr, how the high dietry fiber RS4 strches ffect tortill processing nd qulity is unknown. The objective of this study ws to determine the effects of RS4 whet strch on the physicl nd rheologicl properties of tortill dough nd tortills, s well s consumer cceptbility of the tortills. MATERIALS AND METHODS Dough nd Tortill Preprtion Eight tretments were prepred with the sme mount of ingredients, except for the mount of resistnt strch (RS) substituted for refined whet flour (untreted, bleched, enriched; ADM Milling Co., Overlnd Prk, KS), which were 0 (control), 5, 10, nd 15%. Two cross-linked resistnt whet strch ingredients were used: Fibersym RW (Fsym) nd FiberRite RW (FRite) (MGP Ingredients, Atchison, KS). Composition dt from the supplier indicted tht Fsym nd FRite hve 85% nd >75% totl dietry fiber (TDF), respectively, s determined by AOAC Method 991.43. Both smples re considered RS4 ingredients (modified strch), but Fsym hs low wter bsorption nd is intended for bked goods, while FRite is pregeltinized cross-linked strch tht is ble to bsorb significnt mounts of wter while mintining grnule integrity nd is ment for use in reduced ft formultions nd s thickener. Another tretment with no RS ws prepred using whole white whet flour (Frmer Direct Foods, Atchison, KS) insted of refined whet flour. Dough nd tortills were prepred s described by Alviol nd Wnisk (2008). Quntities of the other ingredients used (side from 500 g of whet flour/rs combintion) were 30 g of shortening (Sysco, Houston, TX), 7.5 g of slt (Morton Interntionl, Chicgo, IL), 3 g of sodium bicrbonte (Arm nd Hmmer, Princeton, NJ), 2.9 g of sodium luminum sulfte (Budenheim USA, Plinview, NY), 2.5 g of sodium steroyl lctylte (Crvn Ingredients, Lenex, KS), 2 g of sodium propionte (Nicet, Nigr Flls, NY), 2 g of potssium sorbte (B.C. Willims, Dlls, TX), 1.6 g of encpsulted fumric cid (Blchem, New Hmpton, NY), nd 0.015 g of cysteine (Fleischmnn s Yest, Burr Ridge, IL). Wter (distilled) ddition ws bsed on mixogrph wter bsorption ( 10%) (% flour bsis) s control 52.0; whole whet 56.0, 5% Fsym 54.7, 10% Fsym 60.0, 15% Fsym 64.7, 5% FRite 55.8, 10% FRite 62.2, 15% FRite 67.0. Vol. 87, No. 3, 2010 221
Subjective Evlution of Dough Properties Dough ws subjectively evluted using 1 5 rting for smoothness, softness, extensibility, nd force to extend (Alviol et l 2008). A score of 1 mens the dough is very smooth, very soft, breks immeditely, nd needs less force to extend. Conversely, score of 5 mens tht the dough is very rough, very firm, excessively extensible, nd needs much force to extend. Hrdness of dough ws mesured objectively with texture nlyzer (model TA-XT2i, Texture Technologies, Scrsdle, NY). A dough bll ( 2.1 cm thick, 5.2 cm dimeter, 45 g) ws plced on n luminum pltform nd compressed t speed of 10 mm/sec t 70% strin with n luminum cylindricl probe (10 cm dimeter). Pek force ws determined s dough hrdness (Brros 2009). The extensibility test ccording to Smewing (1995), which uses the Kieffer dough nd gluten extensibility rig ttched to texture nlyzer, ws followed with modifictions. After resting the dough blls for 10 min in the proofing chmber (32 C, 70% RH), 20 g from one dough bll ws tken nd rolled into cylindricl shpe, plced into the grooved mold, rested for 40 min t room temperture, nd evluted. Dough extensibility nd resistnce to extension were determined. Subjective Evlution of Tortills Ten tortills from ech btch, prepred on two different dys, were rndomly selected nd mesured for weight, thickness, dimeter, nd opcity (Alviol et l 2008). Likewise, two tortills from ech btch were rndomly selected nd mesured for color using chrommeter (model CR-300, Minolt Cmer, Osk, Jpn). Vlues for L* (brightness or whiteness), * (greenness to redness), nd b* (yellowness to blueness) were determined. Tortill smples were freeze-dried for totl strch nd dietry fiber nlysis. Totl strch ws determined using Approved Method 76-13 (Megzyme Amyloglucosidse/α-mylse) (AACC Interntionl 2000). Totl dietry fiber ws determined using AOAC Method 985.29. The tortills were subjectively evluted for shelf-stbility using the rollbility technique, 4, 8, 12, nd 16 dys fter processing (Ceped et l 2000). A tortill ws rolled round 1-cm wooden dowel nd rted from 1 (breks immeditely, cnnot be rolled) to 5 (no crcks, very flexible). Tortills were considered uncceptble when the rollbility score ws <3. The two-dimensionl extensibility test ws done with texture nlyzer to get the texture profile of the tortills (Alviol nd Wnisk 2008). Deformtion modulus nd force, distnce, nd work to rupture were determined fter 0, 4, 8, 12, nd 16 dys of storge. Sensory Evlution All eight tretments were evluted for cceptbility using consumer pnel consisting of 73 untrined pnelists. Ech smple ws presented with n ssigned rndom three-digit number code, nd evluted for texture, flvor, color, nd overll cceptbility using 9-point hedonic scle (1 = dislike extremely, 9 = like extremely). Informtion bout the pnelists were lso gthered (ge, gender, ethnicity, nd frequency of tortill consumption). Sttisticl Anlyses Anlysis of vrince (ANOVA) ws performed in completely rndomized design using SPSS v11.0 for Windows for ll dough nd tortill prmeters. Men difference between the refined flour (control) nd ech tretment ws nlyzed with two-sided Dunnett s test (α = 0.05). RESULTS AND DISCUSSION Dough Properties Determining the effects of the dded RS ingredient on dough properties is importnt to know if chnges in processing conditions will be needed. A significnt chnge in formultion my men differences in dough mchinbility (i.e., ese of dividing, rounding, pressing, etc.). Doughs with 5 15% Fsym nd 5% FRite were s soft, extensible, nd esy to press s the refined whet dough (control) bsed on subjective evlution (Tble I). Dough with 10 nd 15% FRite on the other hnd ws less soft nd extensible, nd lso hrder to press or hndle thn the control. Whole whet dough ws lso less soft nd extensible thn its refined whet counterprt. Objective evlution with texture nlyzer confirmed tht 15% FRite nd whole whet dough were hrder nd less extensible thn the refined whet dough (Tble I). This ws due to the type of fiber in whole whet nd FRite RS, which bsorbed wter nd competed with the gluten in the dough system. Whet brn is rich in wtersoluble polyscchrides with high wter-binding cpcity, wheres FRite is primrily used s viscosity modifier by mnufcturers. Whole whet nd 5, 10, 15% FRite tretments incresed dough wter bsorption by 2% nd 1, 3, 5%, respectively, reltive to the control; Fsym incresed wter bsorption by 1 nd 3% t 10 nd 15% substitution, respectively. Between the two RS ingredients, Fsym ws esier to incorporte nd process nd behved similr to control. Thus, the Fsym would more redily fit into existing tortill processing protocol without the need for extensive djustments. FRite worked liked trditionl fiber ingredients nd ws comprble to whole whet dough in tht it incresed wter requirement nd still hd reltively hrder dough fter proofing. This high wter-holding cpcity of fiber ffects the dough properties nd, consequently, the tortill qulity becuse it competes with gluten for wter. Gluten hs to bsorb enough wter to be fully developed nd efficiently provide the needed structure of the finl product. 222 CEREAL CHEMISTRY TABLE I Properties of Control nd Resistnt Strch-Fortified Dough Evluted Subjectively nd Objectively Control Whole Prmeter Refined Whet Whet 5% 10% 15% 5% 10% 15% Subjective b Softness 2.0 3.3* 1.8 2.0 1.8 2.0 2.8* 3.0* Extensibility 3.8 1.8* 3.8 3.0 3.3 3.0 2.3* 1.5* Force to extend 1.8 3.3 1.8 2.0 2.0 2.0 3.0 3.5* Press rting 2.3 3.5 2.3 2.5 2.3 2.5 3.3 3.8* Objective Hrdness (N) 113 229* 142 122 112 124 130 221* Resistnce to extension (N) 0.40 0.62* 0.48 0.35 0.34 0.65* 0.50 0.57* Extensibility (mm) 55.9 17.3* 26.8 39.3 41.6 39.7 32.3 20.6* Men vlues from two trils. * Indictes significnt difference from control (P < 0.05, Dunnett s test). b Subjective dough evlution scle. Softness (1 very soft, 5 firm); extensibility (1 not extensible, 5 very extensible); force to extend (1 less force, 5 much force); press rting (1 esy to press, 5 hrd to press).
Tortill Properties Tortill weight of whole whet nd Fsym tortills were similr to control (Tble II), even though the whole whet nd 15% Fsym doughs bsorbed more wter thn control dough. The whole whet tortill likely lost more moisture in the oven due to its porous nture (lrger prticle size) reltive to control. The Fsym dough likely lost more moisture in the oven thn the control due to the fct tht this prticulr RS4 hs poor bility to trp excess bsorbed wter due to very wek or limited hydrogen bonding sites with wter. FRite tortills on the other hnd showed significnt (P < 0.001) nd liner (R 2 = 0.97) (dt not shown) trend of incresing weight with incresed RS substitution (Tble II). At 15% substitution, FRite tortills weighed 6.2% more thn control. Bsed on liner regression, every 1% increse in FRite substitution incresed tortill weight by 0.4%. Miller et l (2008) recently observed tht substitution of whet flour with pregeltinized cross-linked nd hydroxypropylted whet strches t 8.3% incresed bred weight by 3.8%. They suggested this my be promising strtegy to increse bred yield. The FRite should be investigted further for potentil to increse yield of tortills (tortill weight reltive to dry ingredient input). However, its negtive effect on dough hndling would need to be overcome. The 10 nd 15% Fsym tortills hd significntly lrger dimeters, which is one of the key qulity ttributes of tortills (Adms nd Wnisk 2002) compred with control tortills (Tble II); other tretments were similr to the control in dimeter. This ws likely due to the fct tht the Fsym RS diluted the gluten network without significntly contributing to the dough intermoleculr network during mixing (i.e., Fsym behved like reltively inert ingredient). The resulting dough ws esy to spred with miniml shrink-bck during pressing. Even though the whole whet nd 10 nd 15% FRite doughs lso significntly diluted gluten network, they produced doughs tht were less extensible (Tble I), thus resisted spreding, due to the hydrogen bond networks formed by wter-soluble components (Neukom 1976). Whole whet tortills were significntly thinner, less opque, nd hd drker color thn the control. The reltively lrge brn prticles not only wekened the gluten mtrix, mking it less effective in mintining the ir bubbles from the levening ction, but lso creted porous surfce, llowing ir bubbles to escpe esily, resulting in thinner tortills. Hving less ir bubbles lso resulted in more trnslucency of the whole whet tortills becuse refrction of light from ir bubbles contribute to opcity (Adms nd Wnisk 2002). The brn components in the whole whet flour lso gve light brown color to the tortills, thus significntly reducing its L vlue reltive to the other smples (Tble II). Tortills with 10 nd 15% FRite nd whole whet flour lso hd lower specific volume thn the control. This mens tht they were Fig. 1. Subjective rollbility scores of control tortills nd tortills fortified with resistnt strch: 1 = breks immeditely, cnnot be rolled; 5 = no crcks, very flexible. Error brs represent ± stndrd devition. Brs with * significntly different from control within ech dy (P < 0.05; Dunnett s test). TABLE II Properties of Control nd Tortills Fortified with Resistnt Strch Control, Refined Whole Prmeter Whet (RW) Whet 5% 10% 15% 5% 10% 15% % RSD Weight (g) 40.5 39.5 40.8 40.2 39.3 41.3 41.8* 43.0* 1.4 Thickness (mm) 3.00 2.39* 3.00 2.82 2.81 2.95 2.79 2.84 2.2 Dimeter (mm) 164 161 169 177* 176* 161 158 158 1.5 Opcity (%) 75 49* 85 88 90 74 69 77 4.7 Specific volume (cm 3 /g) 1.57 1.24* 1.64 1.72 1.74 1.46 1.32* 1.29* L* 81.5 64.4* 82.1 82.4 83.5 81.9 81.1 81.3 0.9 * 0.36 6.4* 0.37 0.14 0.13 0.38 0.61 0.60 36.6 b* 19.0 21.9 18.7 17.8 16.2 18.3 18.3 17.7 3.8 Totl strch (%, db) 68.0 54.5* 68.4 67.7 67.6 67.7 67.9 66.8 0.9 Totl dietry fiber (%, db) 2.8 12.6* nd nd 14.3* nd nd 13.6 5.5 Men vlues from two trils. * Indictes significnt difference from control (P < 0.05, Dunnett s test); nd, not determined. Vol. 87, No. 3, 2010 223
less fluffy or puffed nd more dense. Bixuli et l (2008b) observed decrese in gs cells nd height of muffins (i.e., denser muffins) with n incresing substitution of whet flour with RS. Tortills with Fsym, on the other hnd, gve excellent tortill qulity (similr to control). Totl strch content of the control nd RS-contining tortills were similr with rnge of 67 68% db (Tble II). Tortills from whole white whet flour hd significntly lower totl strch (54%), s expected, becuse of the higher protein, ft, nd nonstrch fiber content from the whet pericrp nd brn. The substitution of 15% RS in refined tortill flour incresed dietry fiber content of the tortills from 2.8 g/100 g db to 14.3 nd 13.6 g/100 g db for Fsym nd FRite, respectively (Tble II). Whole whet tortills hd 12.6 g/100 g db of dietry fiber. These vlues trnslte to 0.8 g of dietry fiber/serving (40 g of tortill) for refined flour tortill. Tortills with whole whet, 15% Fsym, nd 15% FRite hd 3.5, 3.9, nd 3.6 g of fiber/serving, respectively. Thus, both 15% RS4 substituted tortills qulified s good sources of fiber bsed on FDA llowed nutrient content clim. Subjective rollbility scores of tortills on dy 4 of storge were similr between the control nd the tretments (Fig. 1). By the dy 8 of storge, 15% FRite tortills were significntly less flexible thn the control; while t dy 12, both 10 nd 15% RS4 substituted tortills were less flexible thn the control. However, bsed on the rollbility scores, ll tortills were still cceptble (scores 3). After 16 dys, the treted tortills were not different from the control; ll still hd cceptble rollbility scores (Alviol et l 2008). Objective texture evlution with texture nlyzer showed n increse in deformtion modulus with storge time (Tble III), which mens more force/mm ws needed to deform tortills s they stled, primrily due to strch retrogrdtion (Alviol nd Wnisk 2008). This ws ccompnied by decrese in both extensibility (rupture distnce) nd work required to rupture the tortill (Tble III). The fresh (dy 0) Fsym-substituted smples hd significntly lower deformtion modulus (0.64 0.66 N/mm) compred with the control (0.76 N/mm), while whole whet tortills hd higher vlues (0.89 N/mm) thn the control. This indictes tht t dy 0, tortills with Fsym were softer nd more tender thn the control tortill, probbly due to the fct tht this cross-linkge did not significntly prticipte in intermoleculr bonding nd minly cted s diluent nd prtil inhibitor of strch mylse network formtion during bking. Whole whet tortill, on the other hnd, ws less tender thn control, probbly due to effect of wter-soluble brn polyscchrides tht prticipted in cross-linkges with strch nd proteins (Neukom 1976). By dy 16, ll smples hd similr texturl profiles s mesured by the texture nlyzer. Sensory Evlution One-dy-old tortills were evluted for consumer cceptbility of ppernce, flvor, nd texture using 9-point hedonic scle. The untrined pnel ws composed of 55% femles nd 45% mles, with 67% in n ge rnge of 18 40. The two mjor ethnic groups represented were Cucsins (40%) nd Hispnics (23%). When sked frequency of tortill consumption, 40% sid t lest once week nd 30% sid once every two weeks. Among the tretments, only the whole white whet tortills were significntly less cceptble thn the control in overll cceptbility, ppernce, flvor, nd texture (Tble IV). This grees with the results of Friend et l (1992), wherein the increse in substitution of refined whet with whole whet flour gve corresponding decrese in consumer cceptbility of tortills. This lso underscores broder consumer dislike for whole grin products, thus necessitting lterntive strtegies to deliver dietry fiber to consumers. TABLE III Texture Chnges of Tortills Fortified with Resistnt Strch Deformtion Modulus (N/mm) Rupture Distnce (mm) Work (N mm) Dy 0 Dy 16 Dy 0 Dy 16 Dy 0 Dy 16 Control, refined whet (RW) 0.76 1.19 19.6 11.4 75.3 34.9 Whole whet 0.89* 1.36 14.9 10.0 55.7 29.5 5% 0.66* 0.95 20.1 11.7 67.2 31.9 10% 0.64* 0.94 17.2 10.7 46.9 21.6 15% 0.68* 0.85 17.3 10.6 50.7 20.3 5% 0.70 1.16 19.2 10.7 67.8 28.4 10% 0.77 1.33 18.2 10.1 68.7 26.8 15% 0.81 1.09 15.8 9.8 57.6 20.1 Men vlues from two trils. * Indictes significnt difference from control (P < 0.05, Dunnett s test). TABLE IV Sensory Evlution Scores of Tortills Fortified with Resistnt Strch,b Overll Acceptbility Appernce Flvor Texture Control, refined whet (RW) 6.6 7.2 6.7 6.7 Whole whet 5.5* 5.9* 5.3* 5.8* 5% 6.3 7.1 6.5 7.1 10% 7.0 7.2 6.8 7.8* 15% 7.5* 7.6 7.3 8.2* 5% 6.8 7.2 6.6 6.5 10% 6.9 7.2 7.2 7.0 15% 6.5 6.9 6.7 6.4 % RSD c 16.6 16.4 18.8 17.4 Men vlues from two trils. * Indictes significnt difference from control (P < 0.05, Dunnett s test). b Hedonic scle (1 dislike extremely, 5 neither like nor dislike, 9, like extremely). c Reltive stndrd devition. 224 CEREAL CHEMISTRY
Tortills with Fsym generlly hd higher scores for texture thn the control, which confirms the objective texturl dt described bove (these tortills were generlly more tender). Bixuli et l (2008) lso observed higher texture cceptbility scores in muffins with 10% RS. Interestingly, tortill with 15% Fsym hd significntly higher overll cceptbility scores thn the control tortill, suggesting this RS my be vluble functionl dietry ingredient for tortills. The FRite tortills were judged similr to control, which lso grees with objective mesurements described bove. However, this prticulr RS hd negtive effect on dough mchinbility nd qulity (Tble I) due to high wter bsorption cpcity. CONCLUSIONS It is techniclly fesible to substitute prt of the whet flour in tortills with low wter-bsorbing cross-linked RS4 whet strch ingredients without significntly ffecting dough mchinbility or product qulity nd cceptbility. The Fsym RS mnufctured from whet ws generlly blnd nd did not interfere with dough hndling, thus 15% ws successfully incorported in tortills, resulting in high dietry fiber content of the finl product tht met FDA requirement for good source of fiber clim. This opens opportunities for mnufcturers to crete nd promote helthier versions of tortills to mrket segments tht prefer refined flour tortill products. However, becuse the RS ingredients re more expensive thn whet flour, such RS-substituted tortills re likely to sell t premium, which is not unusul for products tht offer potentil helth profiles. ACKNOWLEDGMENTS We grtefully cknowledge the vrious suppliers for the ingredients, prticulrly MGP Ingredients for the resistnt strch smples; nd the Texs Whet Producers Bord nd Texs AgriLife Reserch for the finncil support. LITERATURE CITED AACC Interntionl. 2010. Approved Methods of Anlysis, 11th Ed. Avilble online only. AACC Interntionl: St. Pul, MN. Adms, J. G., nd Wnisk, R. D. 2002. 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