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Journal of Cereal Science 58 (2013) 437e445

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Journal of Cereal Science

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Effects of endoxylanases, vital wheat gluten, and gum Arabic on the rheological properties, water mobility, and baking quality of whole- wheat saltine cracker dough

Juan Li a,b, Gary G. Hou b,*, Zhengxing Chen a,**, Kathleen Gehring b a School of Food Science and Technology, National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, Wuxi, Jiangsu 214122, PR China b Wheat Marketing Center, Inc., 1200 NW Naito Parkway, Suite 230, Portland, OR 97209, USA article info abstract

Article history: The aim of this study was to improve the baking quality of whole-wheat saltine cracker (WWSC) using Received 14 June 2013 endoxylanases, vital wheat gluten (VWG), and gum Arabic. SRC results showed both water-SRC and Received in revised form sucrose-SRC of soft white whole-wheat flour (SWWW) were significantly reduced by gum Arabic 26 August 2013 (r ¼ 0.94, P < 0.05). Alveograph results indicated that the tenacity and extensibility of the whole-wheat Accepted 8 September 2013 dough (WWD) were increased by VWG. Rheometer G0 and G00 moduli increased with higher addition levels of endoxylanases, VWG, and gum Arabic. Low-field nuclear magnetic resonance (LF-NMR) detected Keywords: three CPMG proton populations (T , T , and T ) in WWD. T peak area ratio (tightly bound water) Whole wheat saltine cracker 21 22 23 21 Endoxylanases reduced and T22 peak area ratio (less tightly bound water) increased with the levels of each additive. LF- Rheological properties NMR results revealed increased water mobility from T21 population to T22 population with addition of Water mobility these additives, which was beneficial for gluten to form a continuous network. Both stack height and Baking quality specific volume of WWSC were improved by the use of endoxylanases, VWG, and gum Arabic, but the breaking strength varied. The results of Orthogonal experimental design showed that the most-improved quality WWSC could be produced by combining 0.035% endoxylanases, 1.5% VWG, and 1.5% gum Arabic into SWWW flour. Ó 2013 Elsevier Ltd. All rights reserved.

1. Introduction application of WWF in saltine cracker has not been reported else- where in the scientific literature. Crackers are low-moisture content products that have a unique In the manufacture of whole-grain flour products, high water crispy texture. In commercial production of saltine crackers, flour of absorption and weak gluten strength of WWF present many chal- low water absorption but relatively strong gluten strength is lenges in processing and product quality attributes. Loaf volume of required (Kweon et al., 2011). As a result, soft wheat is commonly whole-wheat bread tends to be lower than that of bread made from used for cracker flour, but hard red winter wheat offers some white flour (Bruckner et al., 2001). In the case of whole-wheat quality characteristics that are desired for making saltine crackers saltine crackers (WWSC), additional water is required in the for- by providing gluten strength (Slade et al., 1994). Whole-wheat flour mula and weak gluten strength of soft white whole-wheat flour (WWF) is rich in dietary fiber, phenolic compounds, enzymes, vi- (SWWW) increases the difficulty of cracker dough preparation and tamins, minerals, and phytoestrogens. The regular consumption of reduces puffiness and breaking strength (more fragile) (Li et al., whole-grain flour can provide health benefits such as the reduced 2013). Additional water of whole-wheat dough (WWD) must be risk of cardiovascular disease, type II diabetes, and cancers (Liu, baked out through baking evaporation, which results in prolonged 2007). However, to the best of our knowledge, the practical baking time and energy consumption (Rogers and Hoseney, 1987). Arabinoxylans (AX) are the major non-starch polysaccharides in wheat endosperm cell walls and the primary components responsible for water absorption in WWF. Wheat flour contains approximately 1.5e2.5% AX, of which 25e30% is water extractable * Corresponding author. Tel.: þ1 503 2950823; fax: þ1 503 295 2735. AX (WE-AX) and 70e75% is water unextractable AX (WU-AX) ** Corresponding author. Tel.: þ86 510 85917205; fax: þ86 510 85867273. E-mail addresses: [email protected], [email protected] (G.G. Hou), (Courtin and Delcour, 2002). WE-AX can form highly viscous so- [email protected] (Z. Chen). lutions, whereas WU-AX has a high water-holding capacity

438 J. Li et al. / Journal of Cereal Science 58 (2013) 437e445

(Meuser and Suckow, 1986). The water holding capacity of AX has OR). Baking soda (ARM & HAMMER Div. of Church & Dwigh, Co., Inc., been demonstrated to have significant influences on dough rheo- Princeton, NJ), mineral yeast food (ADM Arkady Inc., Olathe, KS), salt logical behaviors and quality attributes of baked products (Courtin (Morton Salt, Inc., Chicago, IL), Crisco vegetable shortening (trans-fat and Delcour, 2002). Bettge and Morris (2000) reported a negative free) (J.M. Smucker Company, Orrville, OH) and instant dry yeast relationship between cookie diameter and WE-AX in soft wheat (Lesaffre Yeast Corporation, Milwaukee, WI) were purchased from a flour, as dough viscosity (mainly controlled by WE-AX) appears to local supermarket (Portland, Oregon). A sourdough starter was control cookie spread; low-viscosity cookie dough tends to spread originally supplied by Oregon State University and was fed daily more and yields larger diameter (Guttieri et al., 2001). using old starter (50 g), HRW flour (100 g), and distilled water (50 g) In general, endoxylanases (EC 3.2.1.8) hydrolyze the glycosidic during the course of the study. bonds within the xylans, degrading the WU-AX into high molecular weight WE-AX, and/or decomposing the latter into low molecular 2.2. WWF blends preparation weight WE-AX (Sunna and Antranikian, 1997); therefore, it was stated that endoxylanases decrease the water holding capacity of Different levels of endoxylanases (0.01%, 0.02%, 0.03%, and 0.04%), AX and redistribute water in a dough system (Courtin et al., 1999). VWG (1.0%, 2.0%, 3.0%, and 4.0%) and gum Arabic (0.5%,1.0%, 2.0%, and In addition, endoxylanases were shown to improve dough handling 3.0%) (flour basis) were blended into the SWWW flour, respectively. and machinability (Slade et al., 1994), which are beneficial to The addition levels of each ingredient were based on the usage ranges WWSC dough preparation. Vital wheat gluten (VWG) is tradition- recommended by ingredient suppliers and confirmed by our own ally noted for its functional properties in various bakery applica- trials. Each blending was done in a blender (model 71, IMER Inter- tions, such as improving strength and network forming of dough, national Inc., Poggibonsi, Italy) for 20 min to achieve uniform mixture reducing breakage in snack products, improving gas retention and prior to dough preparation. Control flour was 100% SWWW flour. product volume, and improving structure in whole-grain products (Kalin, 1979). It is expected that VWG may improve the quality of 2.3. SRC testing WWSC by increasing gluten strength of SWWW flour and oven spring during baking. Gum Arabic was reported to bring many To determine the effects of endoxylanases, VWG, and gum benefits to bakery products in terms of processing, texture and Arabic on water absorption of SWWW flour, the SRC values of flour shelf life due to its moisture regulation and film-forming properties blends added with different ingredients described in Section 2.2 (Thevenet, 2010). The use of gum Arabic in WWSC is expected to were tested. The SRC values with four solvents as lactic acid SRC make positive contributions to its quality. (LA-SRC), sodium carbonate SRC (SC-SRC), sucrose SRC (Suc-SRC), The molecular mobility of water and biopolymers in food and water SRC (W-SRC) were determined according to the AACC products can be studied with proton nuclear magnetic resonance International Approved Method 56-11.02. (1H NMR). It was successfully applied to examine the water mobility between macromolecule complexes in various dough 2.4. Rheological measurements systems. By determining the spinespin relaxation time (T2) with LF-NMR, Lu and Seetharaman (2013) used a 1H NMR spinespin 2.4.1. Alveograph analysis relaxation time (T2) to study the water mobility in various dough Alveograph parameters of different dough samples were systems containing barley flour. Bosmans et al. (2012) investigated determined by the Alveo-Consistograph (Chopin, Villeneuve-La- starchewater, glutenewater, and flourewater model systems as Garenne, France) according to the AACC International Approved well as straight-dough bread with 1H NMR relaxometry and iden- Method 54-30.02. Dough tenacity (P), extensibility (L) and defor- tified different proton populations in these systems. mation energy (W) were determined. The objectives of this study were: 1) to examine the individual effects of endoxylanases, VWG, and gum Arabic on physicochemical 2.4.2. Dynamic viscoelasticity and rheological properties of WWF and baking performance of The effects of adding endoxylanases, VWG, and gum Arabic on WWSC, 2) to determine the optimal addition of combined endox- rheological properties (storage modulus, G0; loss modulus, G00)of ylanases, VWG, and gum Arabic that provide the most improve- SWWW flour were determined using an AR1000 Rheometer (TA ment to the end-product quality attributes, and 3) to detect the Instruments, New Castle, USA). A standard steel parallel plate (20- effect of each additive on water mobility between proton pop- mm diameter, 1 mm-gap distance) was selected as the testing ulations in a WWD system using LF-NMR in order to explain the probe. The conditions of the frequency sweep test were 0.1e100 Hz mechanism of end product quality improvement. (frequency) and 28 C (temperature). An oscillatory strain sweep test at constant frequency (1 Hz) was performed to determine the 2. Experimental maximum deformation in the linear viscoelastic range. On the basis of this data, the target strain was 1%, which was within this linear 2.1. Materials region. A 3-g SWWW dough added with different levels of each additive was placed between the plates immediately after optimum Ò Soft white whole-wheat (SWWW) flour (Ultragrain : moisture, dough mixing in the Farinograph with a constant water absorption 10.3%; protein, 9.77%; ash, 1.52%; wet gluten, 22.2%; starch damage, of 60%, in order to observe and compare the effects of each additive 3.3%; protein, ash, wet gluten and starch damage were reported on a on the dynamic viscoelasticity of WWD. The excess dough was cut 14% moisture basis) was supplied by ConAgra Mills, Inc. (Omaha, off and mineral oil was coated on the rim of the sample to prevent it NE). This commercial flour was ultrafine WWF that has higher water from drying during the test. The dough was allowed to rest for absorption than traditional cookie flour due to higher damaged 5 min to release the residue strain before testing. Triplicate mea- starch. VWG was provided by MGP Ingredients, Inc. (Atchison, KS). surements for each sample were performed. Pentopan Mono BG is a purified (1, 4)-b-xylanases and was provided by Novozyme Company (Franklinton, NC). Pre-Hydrated gum 2.5. Whole-wheat saltine cracker preparation Arabic-FT was from TIC gums, Inc. (Belcamp, MD). The chemical reagents (ACS grade) used for testing solvent retention capacity A modified sponge and dough method was used to prepare (SRC) were purchased from Nurnberg Scientific Company (Portland, WWSC in the laboratory. Sponge ingredients of WWSC included Author's personal copy

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SWWW ﬂour (65%) (added with different levels of endoxylanases, 2.9. Statistical analysis VWG, or gum Arabic as described previously), sourdough starter (4%), instant dry yeast (0.3%), yeast foods (0.03%), and water (34%). Statistical analyses of orthogonal experimental data were The dough ingredients included SWWW ﬂour (35%), shortening analyzed with the Statistical Package for the Social Sciences (SPSS) (14%), salt (0.8%), water (1%), and baking soda (determined by the Analysis software 17.0 (SPSS Institute, USA). The mean values based total titratable acidity of the sponge). The detailed processing on at least three individual measurements, were compared procedures were described by Li et al. (2013). (a ¼ 0.05) using the general linear model and multivariate ANOVA procedure.

2.6. End-product quality evaluation 3. Results and discussion The stack height, stack weight, specific volume, and breaking strength of WWSC were determined (Li et al., 2013) to evaluate the 3.1. Effects of the endoxylanases, VWG, and gum Arabic on the SRC effects of endoxylanses, VWG, and gum Arabic on the end-product values of SWWW flour baking quality. All measurements were conducted at least three times. The effects of different levels of endoxylanases on the SRC values of SWWW flour are shown in Fig. 1a. The W-SRC and Suc-SRC fl 2.7. LF-NMR determination values of SWWW our reduced only slightly with the increasing level of endoxylanases, mainly because the enzyme reaction time with the flour components was not long enough as the standard Spinspin relaxation time (T2) was determined using the LF- NMR system to observe the effect of endoxylanases, VWG, and SRC procedures were used. Kweon et al. (2011) reported that the fl gum Arabic on water mobility between proton populations in the W-SRC values of ours added with xylanases were consistently fl WWD system. The relaxation time measurements were performed decreased. Treatment of European commercial wheat ours with on a Niumag Desktop Pulsed NMR Analyzer (Shanghai Niumag aculeatus xylanase also caused a decrease in all SRC values (Duyvejonck et al., 2011). The authors further noted that WE-AX Electronics Technology Co. Ltd., China). Transverse relaxation (T2) was measured using the CarrPurcellMeiboomGill (CPMG) only contributed to the Suc-SRC values, whereas the solvent- pulse sequence. The detailed parameters and procedures of mea- accessible AX generally contributed to all SRC values, and particu- surements were described in our previous study (Li et al., 2012). larly to the Suc-SRC values. The reduced water absorption of WWF is preferred for crackers to obtain a crispy texture and to reduce the baking time (Li et al., 2013). The LA-SRC and SC-SRC values of 2.8. Orthogonal experimental design SWWW flour did not show a linear change with the level of endoxylanases because both glutenins and damaged starch were Effects of combined endoxylanases, VWG, and gum Arabic on not affected by the endoxylanases. The differences between this 3 the end-product quality were determined via a L9 (3 ) orthogonal study and other reported results might be caused by the complex experiment. The array was designated involving three factors, A system of WWF, and the type and dosage of endoxylanases used in (endoxylanases), B (VWG), and C (gum Arabic), each at three levels this study. which were selected from the single-factor experiment. Nine In bread making, the use of endoxylanases is to degrade WU-AX groups of experiment were designed to determine the optimum that interfere with the formation of gluten network, into high conditions of combined experimental factors based on the evalu- molecular weight WE-AX, resulting in increased viscosity and ation of stack weight, stack height, specific volume, and breaking dough stability (Courtin and Delcour, 2001), improved oven spring, strength of four dependent variables. and softer crumb (Heldt-Hansen, 2006). In contrast, the most

Fig. 1. Effects of different addition levels of endoxylanases (a), vital wheat gluten (b), and gum Arabic (c) on the solvent retention capacity (SRC) values (W-SRC: Water-SRC; LA-SRC: Lactic Acid-SRC; SC-SRC: Sodium Carbonate-SRC, and Suc-SRC: Sucrose-SRC) of 100% soft white whole-wheat (SWWW) ﬂour. Author's personal copy

440 J. Li et al. / Journal of Cereal Science 58 (2013) 437e445 favorable endoxylanases for making crackers are those that pref- process of dough stretching during fermentation. Rheometer, on erentially hydrolyzed WE-AX and are poorly reactive on WU-AX, so the other hand, determines the viscoelastic properties of dough they can reduce both the water holding capacity and viscosity of under a certain oscillatory frequency without destroying their dough, which are beneficial for crackers to expand and obtain structure. It is expected the results of these two methods are not crispy texture. necessarily linked to each other. The W-SRC, LA-SRC and SC-SRC values showed positive corre- lations (r ¼ 0.91, P < 0.05) with the addition level of VWG, but the 3.2.1. Alveograph W-SRC increased significantly (r ¼ 0.98, P < 0.05) only upon The effects of endoxylanases on the alveograph values of addition of the highest level at 4%. Addition of VWG increased the SWWW are shown in Fig. 2a. The dough tenacity (P value) total gluten content of WWF and its water absorption. VWG can decreased with the levels of endoxylanases, especially between the also enhance the existing gluten network formed by the gluten 0.01 and 0.02% levels, making the cracker dough softened and thus present in the WWF and mitigate the dough weakening effect by easy to handle during processing, and increased the tenderness of the presence of bran particles in such flour. However, the Suc-SRC the baked products. The dough extensibility (L value) had a positive value had no clear relationship with the added VWG (Fig. 1b) correlation (r ¼ 0.98, P < 0.01) with the level of endoxylanases. This since Suc-SRC was mainly affected by WE-AX (Duyvejonck et al., may be caused by the hydrolysis of WE-AX by endoxylanases so 2011). that dough viscosity was reduced and became more extensible. The The W-SRC, LA-SRC, SC-SRC and Suc-SRC values of SWWW flour P/L ratio had a negative correlation (r ¼0.97, P < 0.01) with the all reduced with the level of gum Arabic (Fig.1c). Compared to other endoxylanases. Lower P value and higher L value are desirable for water-soluble polysaccharides with a similar molecular weight, the cracker flour since too high P value exerts a detrimental effect gum Arabic exhibits very low viscosity in water due to its globular, on the crispy and puffy texture of cracker (Kweon et al., 2011). The highly branched structure which hinders the formation of cross- deformation energy (W value) had no clear correlation with the links or hydrogen bonding with water (Thevenet, 2010). Hydra- amount of endoxylanases. tion properties of gluten was not affected by the presence of gum The P, L, and W values all increased with the addition of VWG, Arabic at the tested levels of 0.002e0.013 g per gram of gluten as its while the P/L ratio showed no clear trend, meaning that P and L compact structure could inhibit possible interactions between its values increased in similar proportions (Fig. 2b). These results polar groups and the peptide chains of the gluten (Bárcenas et al., indicated that incorporation of VWG reinforced the existing gluten 2009). network, which could partially offset the negative effect of bran For optimum cracker flour, a higher level of LA-SRC value and particles on the formation of gluten network in the WWD system. lower levels of W-SRC and SC-SRC values were preferred (Kweon However, the increased P value could increase dough toughness, et al., 2011). As the individual performance of endoxylanases, making the cracker too hard in texture for optimized production. VWG, and gum Arabic did not meet the desired quality re- The increased L value could improve the extensibility and the gas quirements of whole-wheat cracker flour, the combined effects of retention capacity of the whole-wheat cracker dough, which was these ingredients must be investigated. expected to increase the puffiness (thickness) of the end products. Therefore, the addition level of VWG should be carefully controlled 3.2. Effects of the endoxylanases, VWG, and gum Arabic on to optimize the end product quality. rheological behaviors of SWWW flour The P, W and P/L values of SWWW flour all reduced with the addition of gum Arabic, while the L values of SWWW flour had a Alveograph and rheometer are two methods that can observe positive correlation (r ¼ 0.99, P < 0.01) with the amount of gum the rheological behaviors of dough. However, there are some dif- Arabic (Fig. 2c). These results indicated that the tenacity of WWD ferences between the two methods. Alveograph testing assists in reduced and the extensibility of the WWD increased by the incor- predicting the biaxial extension produced during dough bubble poration of gum Arabic, both of which are considered beneficial to inflation, which is well linked, from a physical point of view, to the cracker production. There are at least two possible explanations for

Fig. 2. Effects of different addition levels of endoxylanases (a), vital wheat gluten (b), and gum Arabic (c) on the alveograph values (P: tenacity; L: extensibility; W: work; and P/L ratio) of 100% soft white whole-wheat (SWWW) ﬂour. Author's personal copy

J. Li et al. / Journal of Cereal Science 58 (2013) 437e445 441 these results. First, since the alveograph was run on the fixed water macropolymer particle size that was associated with modified absorption, as gum Arabic reduced the dough water absorption gluten rheological properties of a lower Rmax and larger E at Rmax (reduced W-SRC), the dough became wetter and softer, so the P (Wang et al., 2004b). These observations were in agreement with value reduced and the L value increased. Second, gum Arabic has a our alveograph results. highly branched compact arabinogalactan structure that gives a As the addition level of VWG increased, the stack weight, stack low-viscosity solution and also contains a central protein fraction height, specific volume, and breaking strength of end products that provides good emulsification properties. These properties were all gradually increased (Table 1). The original SWWW flour would aid in the extensibility of the dough. Meanwhile, from the was lacking necessary gluten strength due to the presence of bran observation during dough preparation, the cohesiveness of the and germ, resulting in the breakage of cracker dough sheet during WWSC dough pieces was increased by gum Arabic, making the lamination and less gas retention capacity during fermentation and dough easier to handle during processing. Thus, the gum Arabic baking. Upon addition of VWG, the dough strength (P and L values) contributed to the overall quality improvement of WWSC. was increased, and both elasticity and the dynamic viscous property (G0 and G00 moduli) of dough were enhanced; as a result, the 3.2.2. Dynamic viscoelasticity WWSC dough was strong enough to retain gas, and the oven spring G0 represents the dynamic elasticity and G00 represents the dy- was improved. However, too much gluten would greatly increase namic viscous property. Both the G0 and G00 moduli of WWF the tenacity of the cracker dough and restrict the puffiness of the increased with the higher levels of endoxylanases, VWG, and gum end products. Arabic in the frequency sweep test (Fig. 3). According to the results The stack height and specific volume of end products increased of the SRC test, the W-SRC value of WWF components (especially with the added gum Arabic; however, the breaking strength of the the AX) was significantly reduced (r ¼0.95, P < 0.05) by the cracker had a negative correlation (r ¼0.89; P < 0.05) with the presence of gum Arabic at higher addition levels. Presumably, the amount of gum Arabic. The stack weight of the end products had no water may be redistributed from the AX matrix into the gluten significant correlation with the amount of gum Arabic (Table 1). network in the WWD system in the presence of gum Arabic. For- Results of SRC testing showed that the water absorption of WWF mation of the gluten network which attributed to its adequate was reduced by the presence of gum Arabic, which was beneficial water absorption, enhanced the elasticity of gluten and increased for gluten proteins to absorb adequate water and form stronger the G0 modulus of WWD. As for endoxylanases, it was possible that gluten network. Meanwhile, gum Arabic reduced dough tenacity the aggregation of the gluten network was enhanced by the hy- (P) and increased dough extensibility (L), making WWF softened; drolytic action of xylanases on WE-AX (Wang et al., 2004a). On the thus the oven spring and the crispy texture of the end products other hand, additional VWG also contributed to the increases of were expected to benefit from it. dough elasticity (G0 modulus) because VWG enhanced the network formation together with the existing gluten in the flour. 3.4. Effects of the endoxylanases, VWG, and gum Arabic on water The degradation of WU-AX into WE-AX by endoxylanases mobility in WWD increased the mobility of polysaccharide molecules (Meuser and Suckow, 1986) and resulted in a more viscous gel structure (Wang A typical curve of T2 relaxation time distributions of fresh dough 00 et al., 2004b), leading to a higher G modulus. Also, the viscosity usually shows one to three CPMG proton populations, namely T21, of the WWD system was increased by the enhanced adhesiveness T22, and T23 (Li et al., 2013; Lu and Seetharaman, 2013), but they are of VWG and gum Arabic, yielding increases of the G00 modulus of affected by the dough moisture content and compositions (Lu and WWD. High-levels of G0 and G00 values indicate a better dough Seetharaman, 2013), the degree of interactions between polymers elasticity and extensibility for more expansion in baking whole- and water, and the type of NMR measurements [free induction wheat products. decay (FID) and/or CPMG pulse sequence] (Bosmans et al., 2012). Lu and Seetharaman (2013) detected three CPMG water populations in 3.3. Effects of the endoxylanases, VWG, and gum Arabic on the the fresh dough moisture range of 1.1e2.0 g/g db, namely, tightly baking quality of WWSC (T21,2e5 ms), less tightly (T22,20e50 ms), and weakly (T23,100e 200 ms) bound water. As the dough moisture was below 1.1 g/g db, The quality attributes of WWSC were measured after produc- the T23 peak disappeared, and the T21 and T22 peaks seemed to tion. The moisture content of baked crackers was controlled to be in merge into a broad single peak with further decrease of moisture the range of 3e5%. Evaluation results showed that the stack height level (<0.9 g/g db). When the moisture was higher than 2.0 g/g db, and specific volume of WWSC increased with the amount of T23 merged into T22 and formed a broader T22 peak, but a new peak endoxylanases; while the stack weight and breaking strength of was separated from T22. However, both peak times and distribution end products decreased with the amount of endoxylanases patterns were shifted with the blend ratio of whole-grain barley (Table 1). Baking performances of the end products are determined flour in the dough; peak time dramatically reduced with the in- by dough rheological properties especially in relation to the volume creases of whole-grain barley flour in the dough (r ¼0.96, and internal structure of the leavened products. The use of P < 0.05). Therefore, both peak positions and their distribution endoxylanases in the baking process modifies the rheological patterns vary with the dough system being researched. properties of dough such as dough extensibility and resistance to In our WWD system, a typical curve of T2 relaxation time profile breakage (Sorensen, 2003). As more endoxylanases were added, showed three CMPG proton populations: T21 (0.02e0.5 ms), T22 cracker dough became much softer (lower P) and more extensible (0.5e30 ms), and T23 (30100 ms), which represented tightly (high L), which helped the cracker to expand during baking. The bound water, less tightly bound (immobilized) water, and weakly decreased dough crumbliness during lamination also demon- bound (free) water of the moisture in the dough system, respec- strated the modified effects of endoxylanases on the cracker-baking tively, as defined by Lu and Seetharaman (2013). However, the peak performance (Carey et al., 2002). The high water-holding capacity times reported here were much shorter than those reported by Lu of the AX affects the distribution of moisture among the WWD and Seetharaman (2013) because our dough system was 100% constituents, thereby modifying the rheological properties of WWD WWD. In their study, T2 peak times were significantly reduced as system. It was reported that the use of xylanase also resulted in the the blending ratio of whole-grain barley flour was increased in the formation of gluten characterized by a lower average glutenin dough, indicating that some components of whole-grain barley Author's personal copy

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Fig. 3. Effects of different addition levels of endoxylanases on G0 (a) and G00 (b), vital wheat gluten on G0 (c) and G00 (d), and gum Arabic on G0 (e) and G00 (f) of 100% soft white whole- wheat (SWWW) ﬂour. Author's personal copy

J. Li et al. / Journal of Cereal Science 58 (2013) 437e445 443

Table 1 Table 2

Quality evaluations of 100% whole-wheat saltine crackers prepared with different T2 relaxation time distribution of whole-wheat ﬂour with different addition levels of addition levels of endoxylanases, vital wheat gluten, and gum Arabic.a endoxylanases, vital wheat gluten, and gum Arabic.a

c b b b Addition level (%) Stack Stack height Specific Breaking Addition level (%) T21 T22 T23 weightb,c (mm) volume strength (g) Control 0 0.0844 0.0018a 0.8954 0.0013a 0.0202 0.0002b (g) (ml/g) Endoxylanases 0.01 0.0824 0.0006b 0.8969 0.0015a 0.0207 0.0003b Control 0 25.0 0.1a 26.2 0.6a 1.01 0.08a 708.4 68.5a 0.02 0.0770 0.0007c 0.9035 0.0011b 0.0195 0.0001a Endoxylanases 0.01 24.9 0.1a 26.7 0.6ab 1.05 0.09a 701.2 58.5a 0.03 0.0758 0.0005d 0.9039 0.0013b 0.0203 0.0002b 0.02 24.5 0.1b 27.4 0.4b 1.09 0.10a 654.5 55.7a 0.04 0.0713 0.0005e 0.9081 0.0017c 0.0206 0.0002bc 0.03 23.9 0.1c 28.8 0.3c 1.15 0.05a 512.0 45.9b Vital wheat 1.0 0.0741 0.0007b 0.9049 0.0012b 0.0210 0.0004cde 0.04 23.4 0.1d 29.9 0.2d 1.26 0.05b 502.2 38.4b gluten 2.0 0.0734 0.0006b 0.9058 0.0015b 0.0208 0.0002bcd Vital wheat 1.0 24.9 0.1a 27.9 0.6b 1.10 0.09ab 736.3 29.8ab 3.0 0.0714 0.0004c 0.9075 0.0011c 0.0211 0.0003cde gluten 2.0 25.1 0.1a 28.3 0.2b 1.19 0.04b 800.4 27.6b 4.0 0.0704 0.0005d 0.9092 0.0014c 0.0204 0.0002b 3.0 24.4 0.1b 30.0 0.5c 1.20 0.07b 858.4 28.0c Gum Arabic 0.5 0.0702 0.0006b 0.9086 0.0015c 0.0212 0.0002de 4.0 25.5 0.1c 37.2 0.6d 1.40 0.06c 861.5 48.1c 1.0 0.0665 0.0004c 0.9120 0.0017d 0.0215 0.0003de Gum Arabic 0.5 25.9 0.1b 33.7 0.3b 1.10 0.02a 651.9 30.8a 2.0 0.0659 0.0004c 0.9123 0.0016d 0.0217 0.0003e 1.0 25.9 0.1b 38.5 0.2c 1.16 0.03b 583.9 23.5b 3.0 0.0646 0.0005d 0.9144 0.0014d 0.0210 0.0002cde 2.0 26.6 0.2c 41.9 0.4d 1.21 0.02b 530.6 19.8c a Values are means S.D. (based on at least three replicate measurements). 3.0 25.9 0.1b 42.2 0.2d 1.27 0.03c 527.4 20.1c Values for each ingredient (for the four levels) were compared to the control value. a Values are means S.D. (based on at least 10 replicate measurements). Values Values for each ingredient within the same column followed by the same letters are for each ingredient (for the four levels) were compared to the control value. Values not significantly different (P < 0.05). b for each ingredient within the same column followed by the same letters are not Peak area ratio, ratio of each peak area to total area (T21, T22, and T23). significantly different (P < 0.05). b Dry basis. c Stack of 7 crackers. assignments to each population because of the different methods used. In addition, the authors did not see much impact of minor levels of nonstarch polysaccharides and lipids in flour on the NMR flour (such as beta-glucan and AX) substantially reduced T peak 2 profiles, and the addition of salt and sugar in concentrations typi- times. At 30% whole-grain barley flour in the fresh dough, T peak 21 cally used in breadmaking did not influence the proton distribu- was at 0.5e2 ms, T peak was at 2e50 ms, and T was at 50e 22 23 tions to a large extent. 150 ms, which were closer to those detected in our WWD system. In our study, due to the presence of AX which has a high-level of X-axis in T relaxation time profile represents water mobility 2 water absorption in WWD, T proton population probably also and is usually presented as degree of binding, rather than a specific 21 contain water absorbed by the AX in addition to the intragranular value, because of its dependence on total moisture content in water in starch; AX have a strong water holding capacity due to dough (Lu and Seetharaman, 2013). The Y-axis in T relaxation time 2 their polysaccharide structure (Izydorczyk and Biliaderis, 1995). curve represents the signal amplitude (intensity) of protons. The Presumably, some water migration occurred from the T popula- areas under the curves of the populations with certain T values are 21 2 tion to the T population with the presence of endoxylanases, vital proportional to the number of protons in the population. Some 22 wheat gluten or gum Arabic, which was beneficial for gluten to researchers have used the integration of peak areas of T distribu- 2 hydrate more and form a continuous network. These three addition profile to calculate the percentage of water populations for tives have different impacts on water holding capacity, and their quantifying the water mobility (Tananuwong and Reid, 2004). We mechanisms of action to promote gluten development are used a similar approach to estimate the water population to detect different. Endoxylanses decrease the water holding capacity of AX water mobility among flour components in WWD in response to and redistribute water in the dough system (Courtin et al., 1999). the addition of each of the three additives. The peak area ratio was The added VWG directly enhanced gluten competition for water defined by Eq. (1). from other sources such as AX and increased the strength of WWD. Similar to endoxylanases, gum Arabic was effective in reducing W- ð Þ SRC as well, so it helped redistribute water to gluten. Additionally, it ð Þ¼ Area T2i ð ¼ ; ; Þ Peak area ratio T2i i 1 2 3 has a function of significantly reducing the pasting viscosities of AreaðT21 þ T22 þ T23Þ starch (Bárcenas et al., 2009) so dough becomes more extensible (1) and easy to spread during baking. An intact gluten network is T2 relaxation time profiles of WWD showed that the T21 peak preferred to enhance the gas retention capacity during fermenta- area ratio reduced and T22 peak area ratio increased with the levels tion and baking of WWSC, resulting in improved oven spring and of endoxylanases, VWG, or gum Arabic (Table 2). In addition, the T2 multi-layer structure of end products. relaxation times of WWD moved slightly with the addition of these When comparing T2 relaxation time profiles of WWD added with additives. The T21 peak position was shifted to the right (longer different additives, some gave very similar results (Table 2), for relaxation time), and T22 and T23 peak positions were slightly example, 0.03% endoxylanases vs. 1.0% VWG, 0.04% endoxylanases shifted to the left (shorter relaxation times) with higher levels of vs. 3.0% VWG, and 4.0% VWG vs. 0.5% gum Arabic. However, their endoxylanases, VWG, or gum Arabic (data not shown). According to end-product quality attributes especially the breaking strength of fi Lu and Seetharaman (2013), the T21 population was assigned to cracker was very different. T2 relaxation time pro le with NMR is a intragranular water in starch (tightly bound water), T22 was useful tool to detect water mobility in complex dough systems, but assigned to overlapped populations of starch extragranular water the end product quality is determined by interaction of each additive fl and water in the gluten matrix (less tightly bound water), and T23 with our components and ingredients of WWSC dough system. was assigned to capillary water (weakly bound water) in a fresh white flour dough system. In another study, Bosmans et al. (2012) 3.5. Effects of combined endoxylanases, VWG, and gum Arabic on investigated the proton populations of unheated flourewater the end-product quality attributes mixture with 1H NMR relaxometry using FID and CPMG pulse se- quences and detected two FID populations (A and B) and three The orthogonal experimental design data of multiple factors CPMG populations (C, D, and E). The authors gave different proton were analyzed using the range analysis to determine optimal Author's personal copy

444 J. Li et al. / Journal of Cereal Science 58 (2013) 437e445 conditions of factors and levels (Table 3). In Table 3, range value (R on the formation of a continuous gluten network in the WWD. Gum value) is the determination of how much variation each factor has Arabic was very effective in reducing the tenacity and improving the contributed to variables. Mean value (K value) shows the effect of extensibility of WWD. All three additives increased G0 and G00 moduli factor levels on variables. If the K value is higher, it means more of WWD, indicating a better dough elasticity and extensibility bal- significant impact of independent factors on variables. Results of ance for more expansion in cracker baking. LF-NMR revealed an multiple factor range analysis show that the rank of R-value of increase of water mobility from the T21 proton population to the T22 cracker stack weight was: RA > RB > RC, meaning the effect of factors proton population with the incorporation of endoxylanases, VWG, on the cracker stack weight was: A > B > C. The ranks of K-values of or gum Arabic. These results suggested that accessible water became A, B, and C factors were: K3 > K2 > K1, K3 ¼ K2 > K1, K1 > K2 ¼ K3, more available for gluten to develop a continuous network and the respectively, so the optimum conditions for the cracker stack improved baking quality of WWSC was realized. weight was A3B2C1 (although the K value of B2 was equal to B3, the lower addition level was selected). Based on the same selection principles, the optimum condition factors and levels for the cracker References stack height, specific volume, and breaking strength were A3B3C2, A B C , and A B C , respectively. In summary, A had the most AACC International. Approved Methods of the American Association of Cereal 3 1 3 3 3 1 3 e fi fi Chemists. Methods 56 11.02 and 54-30.02, eleventh ed. The Association, St. signi cant impact on the stack weight, stack height, speci c vol- Paul, MN. ume, and breaking strength of crackers; B3 had the most significant Bárcenas, M.E., De la O-Keller, J., Rosell, C.M., 2009. Influence of different hydro- impact on the stack height and breaking strength of crackers; and colloids on major wheat dough components (gluten and starch). J. Food Eng. 94, e fi 241 247. C1 had the most signi cant impact on the stack weight and Bettge, A.D., Morris, C.F., 2000. Relationships among grain hardness, pentosan breaking strength of crackers. Thus, the optimum condition factors fractions, and end-use quality of wheat. Cereal Chem. 77, 241e247. and levels of all three ingredients for the most quality improvement Bosmans, G.M., Lagrain, B., Deleu, L.J., Fierens, E., Hills, B.P., Delcour, J.A., 2012. As- signments of proton populations in dough and bread using NMR relaxometry of of end products were: A3B3C1 (0.035% endoxylanases, 1.5% VWG, starch, gluten, and flour model systems. J. Agric. Food Chem. 60, 5461e5470. and 1.5% gum Arabic). Bruckner, P.L., Habernicht, D., Carlson, G.R., Wichman, D.M., Talbert, L.E., 2001. Comparative bread quality of white flour and whole grain flour for hard red spring and winter wheat. Crop Sci. 41, 1917e1920. 4. Conclusions Courtin, C.M., Roelants, A., Delcour, J.A., 1999. Fractionationereconstitution exper- iments provide insight into the role of endoxylanases in bread-making. J. Agric. Food Chem. 47, 1870e1877. The dough extensibility of SWWW flour was much improved by Courtin, C.M., Delcour, J.A., 2001. Relative activity of endoxylanases towards water- endoxylanases due to increased mobility of polysaccharide mole- extractable and water-unextractable arabinoxylan. J. Cereal Sci. 33, 301e312. fl cules and reduced dough viscosity. VWG reinforced the existing Courtin, C.M., Delcour, J.A., 2002. Aarabinoxylans and endoxylanases in wheat our bread-making. J. Cereal Sci. 35, 225e243. gluten network, which mitigated the negative effect of bran particles Carey, J.M., Moisey, M.J., Levine, H., Slade, L., Dzurenko, T.E., McHugh, K., 2002. Crispy Wheat-based Snacks Having Surface Bubbles. US Patent No. 6,479,090 Table 3 B1. 3 Orthogonal array L9 (3 ) design and multiple factors range analysis. Duyvejonck, A.E., Lagrain, B., Pareyt, B., Courtin, C.M., Delcour, J.A., 2011. Relative contribution of wheat flour constituents to solvent retention capacity profiles of b fi No. A (%) B (%) C (%) Stack Stack height Speci c volume Breaking e a,b European wheats. J. Cereal Sci. 53, 312 318. weight (mm) (ml/g) strength (g) Guttieri, M.J., Bowen, D., Gannon, D., O’Brien, K., Souza, E., 2001. Solvent retention (g) capacities of irrigated soft white spring wheat flours. Crop Sci. 41, 1054e1061. 1 0.025 0.5 1.5 28.1 20.6 1.09 506.3 Heldt-Hansen, H.P., 2006. Macromolecular interactions in enzyme applications for food products. In: Gaonkar, A.G., McPherson, A. (Eds.), Ingredients Interactions: 2 0.025 1.0 2.0 27.9 22.8 1.12 543.6 Effects on Food Quality. Taylor and Francis, Boca Raton, pp. 363e388. 3 0.025 1.5 2.5 28.3 26.2 1.21 576.4 Izydorczyk, M.S., Biliaderis, C.G., 1995. Cereal arabinoxylans: advances in structure 4 0.030 0.5 2.0 28.0 21.0 1.18 500.9 and physicochemical properties. Carbohydr. Polym. 28, 33e48. 5 0.030 1.0 2.5 28.7 23.2 1.27 619.8 Kalin, F., 1979. Wheat gluten applications in food products. J. Am. Oil Chem. Soc. 56, 6 0.030 1.5 1.5 28.5 26.2 1.10 634.1 477e479. 7 0.035 0.5 2.5 28.4 26.5 1.39 600.1 Kweon, M., Slade, L., Levine, H., 2011. Solvent retention capacity (SRC) testing of 8 0.035 1.0 1.5 29.7 30.7 1.27 674.4 wheat flour: principles and value in predicting flour functionality in different 9 0.035 1.5 2.0 29.6 34.0 1.33 649.5 wheat-based food processes and in wheat breedingda review. Cereal Chem. 88, 537e552. Stack weight K1 28.1 28.2 28.8 Li, J., Kang, J., Wang, L., Li, Z., Wang, R., Chen, Z.X., Hou, G.G., 2012. Effect of water K2 28.4 28.8 28.5 migration between arabinoxylans and gluten on baking quality of whole wheat K3 29.2 28.8 28.5 bread detected by magnetic resonance imaging (MRI). J. Agric. Food Chem. 60, R 1.1 0.6 0.3 6507e6514. Stack height K1 23.2 22.7 25.8 Li, J., Hou, G.G., Chen, Z.X., Chung, A.-L., Gehring, K., 2013. 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