Starch Damage in Soft Wheats of the Pacific Northwest

Transcription

1 CRBOHYDRTES Starch Daage in Soft Wheats of the Pacific Northwest P.-Y. LN 1 and Z. CZUCHJOWSK 1 BSTRCT Cereal Che. 73(5): The effect of broad growing conditions in the Pacific Northwest and varietal differences on starch daage (191 saples) of soft white winter (SWW) and club wheat flours were investigated. Starch daage was easured enzyatically by the ethod and iodoetrically by a Chopin Rapid Flour Tester (RFT). The overall average of starch daage (cultivars, years, and locations) showed a coparable level in SWW and club wheat flours. The starch daage in club wheat flours was ore stable over crop years than in SWW wheat flours. For individual cultivars, averaged over crop years and locations, the SWW cv. Madsen had the highest percentage of starch daage at 4.77%, while Lewjain and Dusty had the lowest percentage of starch daage aong SWW wheats, at 3.19 and 2.76%, respectively. ong club wheats, Tres showed the highest percentage of starch daage at 4.3%, and Moro the lowest with 3.4%. The strong correlation between starch daage values easured enzyatically by the ethod and the electric current reading (Eu) of the Chopin Rapid Flour Tester (RFT) for 191 Buhler illed soft wheat flours fored the basis for a calibration curve and respective equation. The equation was introduced into the Chopin RFT instruent and successfully used for predicting starch daage in three validation sets of saples (41 saples total) with excellent accuracy of.29% for soft white winter (SWW) wheat flours and.1% for club wheat flours. The equation could to be applicable to unknown coercial blends of soft wheat flours. The level of starch daage is an iportant quality index for the evaluation of both hard wheat and soft wheat flours. Starch daage is unpreventable during the process of conversion of cereal grain to flour; it is a consequence of illing, rather than an objective (Evers and Stevens 1985). The aount of daage varies with the severity of the illing process and the hardness of the wheat kernel (Faridi 199). Daaged starch granules absorb ore water than nondaaged starch and are ore susceptible to enzyatic hydrolysis (Evers and Stevens 1985, Bloksa and Bushuk 1988, Hoseney et al 1988, Poeranz 1988, Faridi 199). Both end-use and rheological properties of a flour dough are greatly influenced by the level of starch daage in the flour. Starch daage is substantially and consistently lower in soft than in hard wheat flours (Poeranz 1988). High starch daage is detriental to soft wheat products, especially in cookies and cakes (Evers and Stevens 1985, Gaines et al 1988, Hoseney et al 1988, Faridi 199). Methods currently used for deterination of starch daage are based on enzyatic and iodoetric assays. Enzyatic ethods require a long process and high operator skill (Rogers et al 1994). Chopin RFT cobines the iodoetric ethod with aperoetric titration, which requires 1 in for each saple and less intensive operator skill. Other analytical ethods, such as the near-infrared reflectance technique (Osborne and Douglas 1981, Finney et al 1988, Morgan and Willias 1995) and reversed-phase highperforance liquid chroatography (Sutton and Mouat 199) have also been reported. Several publications describing the coparison between Chopin RFT and enzyatic ethods have recently been published (Ranhotra et al 1993, Rogers et al 1994, Morgan and Willias 1995). With a liited nuber of soft wheat saples, Morgan and Willias (1995) concluded that the Chopin RFT is not suitable for evaluation of starch daage in wheats other than hard wheats. ndependent of the technique, research on starch daage of wheat was focused on saples including soft and hard cultivars differing widely in starch daage or intentionally daaged flours. The lgraduate student, associate professor, respectively, Departent of Food Science and Huan Nutrition, Washington State University, Pullan, W E-ail: zuza@wsuvl.csc.wsu.edu Publication no. C R erican ssociation of Cereal Cheists, nc. differences in kernel structure and illing perforance between soft and hard wheats result in large differences in starch daage. These differences are easy to detect. On the other hand, the differentiation of starch daage in soft wheats, which have siilar kernel structure and a narrow range of starch daage, represents a real challenge. The Pacific Northwest (PNW) area of the United States is the largest producer of soft white wheats and the only place where the club wheats are grown. Growing conditions in the PNW area differ widely. These differences in growing conditions ay have a detriental effect on grain quality, such as elevated protein content, increased hardness, or ipaired illing perforance. No systeatic inforation describing the effect of growing conditions and varietal differences on starch daage within PNW soft white wheats is available. Therefore, the objectives of this study were to investigate the effect of broad growing conditions and varietal differences on starch daage in SWW and club wheats grown in the PNW and to develop a calibration curve for the Chopin RFT to predict starch daage in those wheat flours. MTERLS ND METHODS Materials This study investigated a total of 24 soft wheat saples and was conducted in two parts. Part 1 used 191 soft wheat saples, including 123 SWW and 68 club wheats harvested in 1988, 199, and SWW wheat included cvs. Hill8l, Lewjain, Nugaines, Daws, Dusty, Madsen, and Stephens. wheats included Moro, Tres, Crew, and Hyak. The saples were provided by C. J. Peterson (USD-RS), and were collected fro seven locations (Pullan, Poeroy, Ritzville, Walla Walla, Cunningha, Coulee City, and Cavendish) in the PNW. Each cultivar was planted in every location in four replicates. Part 2 included a second set of 41 saples fro seven coercially blended soft wheat flours provided by Fisher Mill Corp. (Seattle, W) and 34 saples obtained fro the USD Western Wheat Quality Laboratory (Pullan, W), representing 17 SWW wheats, and 17 club wheats. Methods Saples used in Part 1 of the study were laboratory illed on a Buhler experiental ill to 6% flour extraction by the approved ethod (CC 1995). n Part 2 of the study, saples were coercially or laboratory (Buhler and Miag) illed. Flour Vol. 73, No. 5,

2 oisture content was easured by the standard CC ethod Protein content (N x 5.7) was deterined by a Leco FP- 428 N-analyzer (Leco Corp., St. Joseph, M). Starch daage was analyzed iodoetrically by a Chopin RFT (Seedburo Equipent Co., Chicago, L) with the original calibration curve provided by Chopin Co., and enzyatically by ethod (CC 76-31). The operation procedures for the RFT were applied according to the user's anual. The E, and predicted CC starch daage value (RFT-CC) were recorded. E, is the current flow between the platinu electrodes as detected by the instruent. Higher E, resulting fro the free iodine ions indicate that a less daaged starch was present in a saple that absorbed iodine ions. Therefore, E, is negatively correlated with starch daage. The E, can be converted to any applied starch daage index (deterined by a selected ethod) by the internal equation of the instruent. The RFT-CC value of starch daage is predicted by the calibration equation, based on the CC 76-3 ethod and built into the Chopin RFT instruent. The conversion of the E, reading to starch daage values can bias the results (Ranhotra et al 1993). n this study, the E, readings were used. calibration curve for predicting starch daage in the PNW soft wheats was constructed based on the correlation between E, and value for the first set of 191 saples, and was introduced to the instruent. The second set of 41 saples was used for the validation of the calibration curve. Statistical nalysis ll tests were run at least in duplicate. Correlation analysis between the two ethods, analysis of variance (NOV) and least significant difference (LSD) were perfored using the Statistical nalysis Syste, Version 6.8 (SS nstitute, Cary, NC.) v Ec b B vi Ec RESULTS ND DSCUSSON The protein content, value of starch daage, RFT- CC value, and E, for the first set of saples (n = 191) and for SWW and club wheat flours considered separately are suarized in Table. The overall average for each of the above easureents for cultivars, years, and locations covers a broad range of values. The SWW and club wheat flours considered separately show coparable levels of protein and starch daage, the latter being siilar within each of the applied ethods. The E, and values for each crop year for all 191 saples are presented in Figure 1. Both ethods, for the SWW and club wheats considered jointly, show the sae trend in changes of starch daage over the three-year period. When the individual crop year is considered, statistically significant differences appear. Saples fro 1993 had the highest starch daage, followed by saples fro 199 and The sae order was obtained by both ethods. This indicates that differences in growing conditions between crop years have great influence on starch daage in wheat flours and that these differences can be easured by both ethods. Figure 1 also shows that for SWW and club wheats, there are significant differences in starch daage between each crop year in SWW wheat flour as easured by both ethods, whereas there is no difference in starch daage in club wheat flour between crop years. Only 1993 is higher in starch daage, as easured by Chopin RFT. This indicates that starch daage in club wheat flours is ore stable over crop years than in SWW wheat flours. Starch daage levels deterined by the ethod in each individual cultivar averaged over crop years and locations is shown in Figure 2. Madsen had the highest level of starch daage (4.77%) aong all cultivars used in this study. Dusty and Lewjain had significantly lower percentages of starch daage than other cultivars (2.76 and 3.19%, respectively). Tres showed the highest and Moro showed the lowest levels in starch daage aong club Starch Daage () 5- b e b cd f a b de b c c 44- c b a ~~~~~~~~~~~~~~~4 24~~~~~~~~~~~~~~~~~4 5 C b a i a a a.u ~~~~~~~~~~~~ SWW Fig. 1. Electrical current (Ej) readings and starch daage values representing each crop year for cobined soft white winter (SWW) and wheats averaged over cultivars and locations () and representing each crop year for SWW and club wheats separately, averaged over cultivars and locations (B). Bars annotated with the sae letter denote ean values that are not significantly different (P <.5) j c ) z c u) Ul ) c) C') 25 % o 2 L ) Fig. 2. starch daage values representing each cultivar averaged over crop years and locations. Bars annotated with the sae letter denote ean values that are not significantly different (P <.5). TBLE Protein and Daaged Starch Content of Saples in Part 1 of Study Daaged Starch Valuesb Protein (%) (%) RFT-CC (%) EC Saplesa Range Mean ± SD Range Mean SD Range Mean ± SD Range Mean ± SD ll (191) ± ± ± ±.21 SWW (123) ± ± ± ±.21 (68) ± ± ± ±.21 a Soft white winter (SWW) and club wheats. Saple nuber indicated in parentheses. b Predicted value using CC ethod for Chopin Rapid Flour Tester (RFT); Ec = electrical current of Chopin RFT. 552 CEREL CHEMSTRY

3 wheats. Siilar order was observed in each crop year (data not shown). This indicates that varietal differences contribute significantly to the aount of daaged starch in wheat flours, and that the varietal contribution can be observed over crop years. The effect of growing location on starch daage averaged over cultivars and crop years is shown in Figure 3. Saples grown in Pullan and Cunningha had the highest percentage of starch daage ( %), followed by Ritzville (3.85%), Cavendish (3.73%), and Walla Walla (3.67%). Poeroy and Coulee City produced wheat flours with the lowest starch daage (3.38 and 3.41%, respectively). The effect of growing location for each crop year is also shown in Figure 3. The level of starch daage for t 3. H 7 7 r F 2..E 5. 4 OQQ, UOO O H H H H E 3. H n n >'- N H E t E E D E E M C5 ( O. ~~~~~ Fig. 3. starch daage values representing each location averaged over crop years and cultivars () and representing each crop year for each location averaged over cultivars (B). TBLE nalysis of Variance for Starch Daage Source of Variationa df Mean Square Fb ll Cultivar *** Location *** Crop year *** SWW Cultivar *** Location *** Crop year *** Cultivar ** Location * Crop year a ll, cobined soft white winter (SWW), and club wheats. b *, ***, = significant at P <.5, P <.1, P <.1, respectively. individual crop years did not follow the sae order as did the average over crop years. However, significant differences existed in starch daage between wheat flour saples grown in different locations for each year. This indicates that not only differences in soil, but also differences in cliatic condition and cultural practice between growing locations ay have strong influences on starch daage in wheat flours. Exaples of the effect of growing locations over crop years on a single cultivar is deonstrated in Figure 4. None of the selected three SWW cultivars (Hill8l, Daws, Dusty) showed a significant difference in starch daage between growing locations, except Poeroy. However, each cultivar showed levels of starch daage distinctly different fro other cultivars. The highest percentage of starch daage (4.6%) characterized Hill8l, while Dusty ) n- &..u, 5.- Hill8l H H H H H H B Daws HHHHHHHH 5.- C Dusty Z. v U n E -,, E ' a- ~~~~~~ (U E Z' * Location Fig. 4. starch daage values representing three soft white winter cultivars Hill81 (), Daws (B), and Dusty (C) averaged over crop years for each location. TBLE Correlation Coefficients Between Value and Electrical Current (E,) of Chopin Rapid Flour Tester (RFT) Cultivara R (P <.1) SWw Hill8l (21) -.91 Lewjain (21) -.87 Nugaines (19) -.93 Daws (21) -.97 Dusty (15) -.85 Madsen (13) -.98 Stephens (13) -.91 Moro (17) -.92 Tres (18) -.91 Crew (2) -.86 Hyak (13) -.78 a Soft white winter (SWW) and club wheats. Saple nuber indicated in parentheses. Vol. 73, No. 5,

4 Ec 3. T qn 3. T showed nearly two ties lower starch daage (2.3-3.%) than Hill81, Daws represented the interediate values. These results indicate that varietal differences have a strong influence on starch daage. The effect of cultivar, location, and crop year on starch daage in the PNW soft wheat flours is suarized in Table. Correlation coefficients between starch daage deterined by enzyatic assay and Chopin RFT ethods for indi *et. *,# M. *... 1.bU i.n -L l l l fi -l vidual cultivars (years and locations) are listed in Table. The correlation coefficients for 11 cultivars range fro -.78 to -.98, indicating that the relationship between these techniques of deterination of starch daage is affected by different cultivars. The effects of crop year on correlation between starch daage value and Chopin RFT Ec reading for cobined SWW and club wheat flours and for each of these classes are suarized in Table V. For cobined saples harvested in 1988, R = For those harvested in 199, R = -.69, while for saples harvested in 1993, R = wheats in these three crop years gave stronger correlations (-.83 to -.95) than did SWW wheats, which had correlation coefficients fro -.62 to The correlation coefficients between value and E, for each class separately are statistically significant for each crop year. However, the growing conditions (weather, fertilizer, etc.) in each crop year have a strong effect on this correlation. The relationship between value and E, for all 191 saples used in the first part of this study and for the 123 SWW and 68 wheat flours considered separately are presented in Figure 5. n each set of saples, there is an even distribution of readings along the regression line. The correlation coefficients of R = -.8 for the cobined 191 saples, R = -.77 for SWW wheats, and R = -.87 for club wheats are statistically significant at the.1% level. These strong correlations for the large nuber of soft wheats grown under diverse conditions indicate that E, readings can be used for prediction of starch daage. The calibration curves and the respective equations of the cobined, SWW, and club sets of wheat flour saples are shown in Figure 6. Because the three regression lines are nearly overlapping, the prediction equation for soft wheat flours was based on all 191 saples. This calibration curve was then built into the Chopin RFT instruent and used for predicting starch daage of the three validation sets of saples used in the second part of (%) Fig. 5. Plots of electrical current (Eu) readings vs. starch daage values., cobined 191 soft white winter (SWW) and club wheats (R = -.8, P <.1); B, 123 SWW wheats (R = -.77, P <.1); C, 68 club wheats (R = -.87, P <.1). TBLE V Correlation Coefficients Between Value and Electrical Current (E, ) of Chopin Rapid Flour Tester (RFT) Year Saplea R (P <.1) 1988 ll (6) -.77 SWW (38) -.62 (22) ll (72) -.69 SWW (49) -.67 (23) ll (59) -.82 SWW (36) -.74 (23) -.95 a Soft white winter (SWW) and club wheats. Saple nuber in parentheses. -- a) E N e %-. a* ll * sww *.~ ~ ~ ~ ~ ~ N- ">~~~~~ Ec (p) Fig. 6. Calibration curves represented all saples (n = 191, % = Ec ), soft white winter (SWW) wheats (n = 123, % = E, ) and club wheats (n = 68, % = E, ). E, is electrical current reading. TBLE V Protein Content,, and RFT-MEGa Values of the Validation Saple Sets Daaged Starch Values Protein Content (%) (%) RFT-MEG (%) Saplesb Range Mean + SD Range Mean t SD Range Mean ± SD SWW (17) ± ± ±.58 (17) ± ±.55 Coercial (7) ± ± ±.46 a Predicted value using CC ethod for Chopin Rapid Flour Tester (RFT); Ec = electrical current of Chopin RFT. b Soft white winter (SWW) and club wheats. Saple nuber indicated in parentheses. 554 CEREL CHEMSTRY

5 w LL z T r ' 7 i _ i i (%) Fig. 7. Plots of easured and predicted starch daage values for the validation sets of saples., 17 SWW wheats (R =.95, P <.1); B, 17 club wheats (R =.91, P <.1); C, seven coercial blends (R =.87, P <.1). RFT-MEG is predicted value using CC ethod for Chopin Rapid Flour Tester (RFT). this study. The validation sets included SWW wheat flours, club wheat flours, and coercially illed blends of soft wheat flours. The protein content, starch daage values, and the values predicted by the Chopin RFT (RFT-MEG) for the validation sets of saples are listed in Table V. Protein content and starch daage for each set of saples fit in the range of calibration set of saples. The set of SWW and club wheat flours had coparable values of starch daage. The starch daage in coercial blends was on average 1% higher than in SWW and club wheat flours. On average, the and the RFT-MEG starch daage values of SWW and club are in excellent agreeent. The differences in percentage of starch daage between actual and predicted values are.29 and.1% for SWW and club wheat flours, respectively. However, the differences in percentage of starch daage between and RFT- MEG values for coercial blends are.91%. This ay have been caused by different treatents (enrichent, bleaching, etc.) or different illing processes of the coercial blends. The good agreeent between easured and predicted RFT- MEG values for all three validation sets is evident in Figure 7. Suary The SWW and club wheat flours show a broad range of starch daage resulting fro different growing conditions (soil, cli- atic, and cultural practice) and varietal differences. However, on the average, the starch daage for both classes is coparable. Varietal differences have consistent strong effects on starch daage in wheat flours, which is likely under genetic control. The calibration equation for Chopin RFT has been successfully attained for prediction of starch daage in flours fro soft wheat grown in the PNW which were laboratory illed on Buhler or Miag ill. The equation could also be used to estiate starch daage in flours illed coercially. CKNOWLEDGMENT Financial support of Washington Wheat Coission is gratefully acknowledged. LTERTURE CTED MERCN SSOCTON OF CEREL CHEMSTS pproved Methods of the CC. 9th ed. Method 26-31, approved October 1988, revised October 1994; Method 44-15, approved October 1975, revised October 1981, and October 1984; Method 76-3, approved May 1969, revised Noveber 1972, October 1982 and October 1984, reviewed October 1994; Method 76-31, approved Septeber 1992, reviewed October The ssociation, St. Paul, MN. BLOKSM,. H., and BUSHUK, W Rheology and cheistry of dough. Pages in: Wheat Cheistry and Technology Vol., 3rd ed. Y. Poeranz, ed.. ssoc. Cereal Che.: St. Paul, MN. EVERS,. D., and STEVENS, D. J Starch daage. Pages in: dvances in Cereal Science and Technology, Vol. 7. Y. Poeranz, ed.. ssoc. Cereal Che.: St. Paul, MN. FRD, H pplication of rheology in the cookie and cracker industry. Pages in: Dough Rheology and Baked Product Texture. H. Faridi and J. M. Faubion, eds. Van Nostrand Reinhold: New York. FNNEY, P. L., KNNEY, J. E., and DONELSON, J. R Prediction of daaged starch in straight-grade flour by near-infrared reflectance analysis of whole ground wheat. Cereal Che. 65: GNES, C. S., DONELSON, J. R., and FNNEY, P. L Effects of daaged starch, chlorine gas, flour particle size, and dough holding tie and teperature on cookie dough handling properties and cookie size. Cereal Che. 65: HOSENEY, R. C., WDE, P., and FNLEY, J. W Soft wheat products. Pages in: Wheat Cheistry and Technology Vol., 3rd ed. Y. Poeranz, ed.. ssoc. Cereal Che.: St. Paul, MN. MORGN, J. E., and WLLMS, P. C Starch daage in wheat flours: coparison of enzyatic, iodoetric, and near-infrared reflectance techniques. Cereal Che. 72: OSBORNE, B. G., and DOUGLS, S Measureent of the degree of starch daage in flour by near infrared reflectance analysis. J. Sci. Food gric. 32: POMERNZ, Y Coposition and functionality of wheat flour coponents. Pages in: Wheat Cheistry and Technology Vol., 3rd ed. Y. Poeranz, ed.. ssoc. Cereal Che., St. Paul, MN. RNHOTR, G. S., GELROTH, J.., and ESENBRUN, G. J Correlation between Chopin and CC ethods of deterining daaged starch. Cereal Che. 7: ROGERS, D. E., GELROTH, J.., LNGEMEER, J. M., and RNHOTR, G. S Evaluation of starch daage values deterined enzyatically or aperoetrically. Cereal Che. 71: SUTTON, K. H., and MOUT, C. L Deterination of daaged starch in wheat flours by reversed-phase high-perforance liquid chroatography. J. Cereal Sci. 11: [Received Septeber 29, ccepted May 21, 1996.] Vol. 73, No. 5,