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The effect of incorporation of rye flour on the quality of oriental noodles
Food Research International, Vol. 31, No. 1, pp. 27±35, 1998 # 1998 Canadian Institute of Food Science and Technology Published by Elsevier Science Ltd. All rights reserved Printed in Great Britain PII: S0963-9969(98)00055-6 0963-9969/98/$19.00+0.00
The eect of incorporation of rye ¯our on the quality of oriental noodles J. E. Kruger, D. W. Hatcher* & M. J. Anderson Grain Research Laboratory, Canadian Grain Commission, 1404-303 Main St. Winnipeg, Manitoba, Canada R3C 3G8
Salted noodles were prepared using Canadian Western Red Winter (CWRW) or Canadian Western Red Spring (CWRS) patent ¯ours augmented with 15, 30 and 50% rye ¯our. Addition of incremental amounts of rye ¯our resulted in signi®cant decreases in both raw and dried noodle brightness, L*, and yellowness, b*. In addition, dry noodle breaking strength, cooked noodle ®rmness, (MCS), and chewiness (REC) also decreased with increasing rye content. However, an acceptable wheat:rye noodle was still possible with a rye incorporation of 30%. Proportional substitution of high gluten strength ¯our from the Canadian Western Extra Stron (CWES) class of wheat in exchange for CWRW ¯our had no signi®cant impact on noodle color but did signi®cantly (p40.05) improve the textural attributes, especially ®rmness, of the 70:30 wheat:rye blended noodles. The addition of peroxide at a 0.5% concentration was found to signi®cantly improve wheat:rye blended noodle brightness and ®rmness. The use of peroxidase in the presence or absence of peroxide had no impact on the wheat:rye noodle quality characteristics. # 1998 Canadian Institute of Food Science and Technology. Published by Elsevier Science Ltd. All rights reserved Keywords: rye, noodles, color, texture.
INTRODUCTION
Wisker, 1995). Preliminary ®ndings have also indicated that rye may reduce cancer in laboratory animals (Hallmans et al., 1995). Boros (1995) has stated that the rye arabinoxylans are one of the major components contributing to the nutritional value of this cereal. The objective of this study was to examine the potential of incorporating increasing amounts of rye ¯our with high quality patent wheat ¯ours in order to produce dried salted noodles. Of particular importance were the eects on noodle color and textural attributes, important discriminating criteria which impact heavily on commercial noodle quality (Miskelly, 1984; Miskelly and Moss, 1985; Oh et al., 1983, 1985a; 1985b; Moss et al., 1986; Toyokawa et al., 1989a; Toyokawa et al., 1989b; Kruger et al., 1992; 1994; 1995; Baik et al., 1995). A secondary purpose was to determine the extent to which the properties of such noodles could be modi®ed by the incorporation of selected ingredients such as ¯our from another class, peroxide and peroxide in combination with peroxidase.
The demand for new niche market noodle products continues to increase in south east Asia as the economies of the respective countries improve. As the gross domestic product, GDP, per capita rises, consumers are now considering secondary features such as health and nutritional aspects of the products they eat. Most Asian markets prefer their noodle products to be made from high quality patent wheat ¯ours. However, the Japanese soba noodle, prepared from buckwheat ¯our, is decidedly colored and has established itself as a viable niche market. Rye (Secale cereale L.) ¯our may have many of the potential health bene®ts attributed to oats. This cereal is known to contain many essential and nonessential dietary components and is a particularly important dietary source of ®ber in Northern and Eastern Europe (Knudsen et al., (1995); Feldheim and *To whom corresondence should be addressed. Fax: +1-204983-0724; e.mail:[email protected] Paper #774 of the Grain Research Laboratory. 27
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J. E. Kruger et al.
METHODS
Noodle preparation
Flours
Noodles were prepared using the method previously described by Kruger et al., (1994). A 1% salt solution (containing hydrogen peroxide and/or peroxidase in selected experiments) was added to 200 g of ¯our in a Hobart N50 mixer (Hobart Canada, North York, ON) over a 30 s interval at the slow speed setting to achieve a ®nal water absorption of 32%. An additional 30 s slow mixing was followed by a 1 min medium setting mix before returning to the slow setting for an additional 3 min. The mixture was then sheeted on an Ohtake laboratory noodle machine (Ohtake, Tokyo, Japan) with an initial gap setting of 3 mm. Two passes were made at this setting with the noodle sheet being folded between passes to ensure homogeneity. A representative 25 cm long section of the noodle sheet was utilized in the subsequent sheeting passes. Seven sheetings with gap settings of 3, 2.55, 2.15, 1.85, 1.57, 1.33 and 1.10 mm were carried out. Total force of individual sheetings was measured via a Labmaster DMA analog-digital board (Scienti®c Solutions, Solon, OH) interfaced to a personal computer using Labtech Notebook software (Laboratories Technologies, Wilmington, MA) to ensure reproducibility between replicate sheetings. The noodle sheet was cut into two portions; one being used for time dependent, raw noodle color measurements while the second portion was passed through the Ohtake cutting blades yielding 2.7 mm wide noodle strands. A portion of these strands were cut into 5 cm lengths, cooked and underwent textural analyses. Dried noodles were prepared in a temperature and humidity controlled drying oven (Conviron, Winnipeg, MB, Canada) for 16 h before being stored a minimum of 2 weeks at 24 C prior to cooking and texture evaluation.
Wheats representing dierent classes of Canadian wheat grown on the Western Prairies; Canadian Western Red Spring (CWRS), Canadian Western Red Winter (CWRW) and Canadian Western Extra Strong (CWES) were milled on the Canadian International Grains Institute (CIGI) pilot mill using a commercial ¯ow operation. Individual streams were composited on the basis of increasing ash to yield high quality patent ¯ours (0.37±0.51% ash). The rye sample was a composite blend of material grown across western Canada, selected from harvest survey samples of 1995, and was milled on the Grain Research Laboratory research mill (Black, 1980). Only breaks and sizings (1±4) from the rye ¯our millstreams were pooled in order to minimize a-amylase and polyphenol oxidase (PPO) activities in the composite rye ¯our (Fig. 1). Analytical results of the ¯ours used in this study can be found in Table 1. Blended ¯ours consisting of 15, 30 and 50% rye ¯our were prepared by incorporating the rye ¯our, on a weight basis, with both CWRW and CWRS ¯ours. A special blend series, composed of 30% rye ¯our and 70% wheat ¯our, in which the composition of CWES and CWRW ¯ours was changed incrementally, was prepared to study the in¯uence of protein strength on noodle quality. Analytical methods Protein content (%N5.7) was determined by the Kjeldahl method, as modi®ed by Williams, (1973); ash content, farinograph and starch damage were determined by AACC methods, (1983) 08±01, 54±21 and 76±30A respectively. Polyphenol oxidase levels were determined by the method of Hatcher and Kruger, (1993) while amylase was determined by the nephelometric method of Kruger and Tipples, (1981).
Table 1. Analytical properties of the ¯ours used in the preparation of oriental noodles Flour Properties Moisture % Protein % Ash % Starch Damagec Farinographb Absorption % Development Time (min) Mix. tolerance Index (B.U.) Stability (min) a
Fig. 1. Levels of polyphenol oxidase (PPO) and amylase activity in the rye ¯our mill streams. *Polyphenol oxidase ~ -amylase.
CWES CWRS CWRW
CWRW: Rye rye blenda
14.2 11.4 0.51
12.5 12.4 0.42
11.8 9.6 0.37
12.1 8.9 0.51
12.8 8.0 0.81
9.0
7.0
5.5
5.3
5.2
59.4
58.1
52.5
52.6
11.50
4.25
2.00
4.25
15 40.0
40 8.50
40 9.00
55 7.00
(CWRW: rye 70:30 blend). Farinograph was carried out at 65 rpm for all samples except CWES where 90 rpm was used. c Starch damage expressed in A.A.C.C. units. b
The eect of incorporation of rye ¯our on the quality of oriental noodles Drying conditions consisted of an initial cabinet temperature of 25 C maintained for the ®rst 1.5 h followed by 2 h at 35 C with the remaining time being spent at 25 C. Relative humidity was maintained at 90% for the ®rst 3 h followed by a 4.5 h linear decline to 60% with the remaining 8.5 h maintained at 55%. Noodle color measurement Noodle color was measured with a Labscan II spectrocolorimeter (HunterLab, Reston, VA) equipped with a D65 illuminant using the CIE 1976 L*, a* and b* color scale. Measurements were made in triplicate at two random locations on the surface for each sample at 0, 2 and 24 h. For white salted noodles, high values of L* are preferred. A consumer preference for a slightly creamy color requires moderate yellow, b*, values while extremes on either side of the red, a*, scale are considered deleterious. Dry noodle breaking strength Breaking strength of individual noodle strands was determined by a 1 mm wide blade ®xture attached to the Instron Universal Testing Machine (IUTM model 4201, Instron, Canton, MA) traveling at 100 mm minÿ1 as per the method of Oh et al. (1985b). Two replications were carried out for each noodle series with each replication being the average of ten individual measurements. Texture measurement Noodles were optimally cooked, cooled for 1 min under running distilled water, drained, and stored for exactly 10 min at 25 C as described by Kruger et al., (1994) prior to textural analysis. The 10 min storage period was utilized as previous work (Kruger et al., 1994) has shown the need to standardize the time after cooking in order to achieve reproducible results. Optimal cook times for the CWRS and CWRW wheat ¯ours, respectively, were 16 and 11 min as determined by the disappearance of the noodle core when squeezed between lexan plates. Cook times decreased with increasing admixtures of rye ¯our. Textural measurements, recovery and maximum cutting strength (MCS) were carried out on cooked noodles using an the IUTM model 4201 with ®xtures and procedures similar to those described by Oh et al. (1983), (1985a) and Kruger et al. (1994). Analyses were carried out on ®ve sets of three noodles with the data being averaged for each duplicate cooking done on separate days. Statistical analysis All statistical analyses; regression and analysis of variance, were carried out utilizing SAS (SAS Institute, Cary, NC, version 6.10) statistical software.
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RESULTS Blending of rye and wheat ¯ours Selection of mill streams for rye ¯our Examination of Fig. 1 reveals that the levels of amylase and polyphenol oxidase in the rye ¯our mill streams increase considerably in the later mill streams. The same phenomena occurs in wheat and Hatcher and Kruger, (1993) have shown that the levels of PPO are signi®cantly reduced by the degree of ¯our re®nement. The pooling of the rye break ¯ours plus sizings (1±4) suggests a natural break in the distribution of these enzymes although PPO levels are 50 times greater than normally found in a patent wheat ¯our and -amylase levels are three-fold higher. Noodle Color The in¯uence of time dependent color changes in raw noodles prepared by incorporating rye ¯our with either CWRS or CWRW patent ¯ours can be seen in Fig. 2. Signi®cant linear decreases, p40.05, in raw noodle brightness were observed with progressive increases in rye ¯our content for both CWRS and CWRW noodles (Fig. 2 A and D). There were noticeable increases in the rate of change in brightness with increasing levels of rye ¯our. Coincident with this was a general increase in raw noodle redness, a*, (Fig. 2B and E) and decreases in yellowness, b*, (Fig. 2C and F). The observed changes can be attributed to two factors. One is the direct in¯uence of naturally occurring colored components in ryes such as ¯avonoids which increase with higher rye content in the admixture. The second factor is the higher level of PPO activity in rye ¯our which would account for the increased rate of decline in brightness associated with greater rye ¯our content. Previous research with Cantonese noodles has indicated a strong relationship between changes in raw noodle brightness, L*, and PPO levels in wheat ¯ours (Kruger et al., 1994). The above results indicate that in preparing dried white salted noodles containing rye ¯our, the time after preparation of the noodles and before drying should be minimized. However, it is generally not possible to shorten the actual drying regime without some compromise to noodle quality, particularly if stress related cracks occur due to rapid drying. The eect of the 16 h drying under controlled temperature and humidity on dried white salted noodles is shown in Fig. 3. The dried noodles were found to have a decreased brightness compared to their 0 and 2 h raw noodle counterparts but were signi®cantly brighter (Fig. 3a) than those allowed to stand for 24 h as might be expected. Dried noodles prepared with both CWRS and CWRW ¯ours had decreases in brightness with increasing rye content that were signi®cant, p40.05, in most cases. Analysis of the red color component, a*, and the yellow component,
30
J. E. Kruger et al.
b*, indicated that for both CWRS and CWRW, signi®cantly, p40.05, dierent values were only found between the pure wheat ¯our noodles and those containing rye blends. The incremental changes observed above with rye incorporation were also apparent by visual examination. In general the noodles took on a brownish but not undesirable appearance with no obvious green or reddish hues at levels up to 30% rye ¯our in the blends.
Dry noodle breaking strength Noodles with rye ¯our incorporation in the wheat ¯our blend broke more easily than wheat ¯our noodles and the eect was progressive with increasing rye ¯our in the admixtures (Fig. 4A). This was particularly noticeable with CWRS ¯our noodles which although substantially stronger than CWRW ¯our noodles displayed a greater decline with increasing rye ¯our addition. At 50% rye ¯our addition both classes of noodles had approximately equivalent breaking strength.
Fig. 2. Time dependent color changes in raw noodles prepared by incorporating rye ¯our with CWRS and CWRW ¯ours. * 0 h & 2 h ~ 24 h Means (n=2) on the same line with dierent letters are signi®cantly dierent (p40.05).
The eect of incorporation of rye ¯our on the quality of oriental noodles Cooked noodle texture Both cooked noodles' ®rmness, (MCS) and chewiness, (REC), as de®ned by Oh et al., (1983), decreased with increasing rye content in the blends (Fig. 4B and C). For both CWRS and CWRW even as little as 15% rye ¯our addition caused a signi®cant (p40.05) decline in these textural attributes. The explanation for these results and those for decreased breaking strength can be partially explained by the widely dierent nature in the functional proteins of rye and wheat. Examination of the properties of rye ¯our compared to wheat ¯our (Table 1) indicates that the amount of protein is considerably less
31
in the former. Furthermore it is well known that rye proteins cannot form gluten after mixing in water (Drews and Seibel, 1976). In the case of dough sheeting, this means that rye proteins cannot contribute to the overall matrix of proteins that improve noodle textural properties. Oh and co-workers (1985c) for example, have established the strong relationships that exist between the amount of protein, as well as protein strength characteristics, on noodle ®rmness and chewiness. Addition of CWES ¯our to CWRW: rye blended ¯our One remedial way to minimize the eects on breaking strength and texture observed above would be to add wheat ¯our which had increased dough strength. The CWES class is appropriately named to represent those wheat varieties with similar protein content to that of CWRS but having stronger gluten. As indicated in Table 1, it is necessary to mix at 90 rpm rather than 65 rpm in the farinograph to develop this dough fully. Experiments were carried out, therefore, in which varying proportions of CWRW ¯our, previously shown to be easily broken, were substituted with CWES ¯our, in 10% increments, in a 70:30 blend of CWRW and rye. Noodle color To obtain an indication of any potential negative impact on color due to adding CWES ¯our, dried noodles were prepared using this ¯our by itself. Brightness, L*, and redness, a*, of CWES (100%) dry noodles were found to be equivalent to the CWRW and CWRS dried noodles. The CWES noodles, however, were signi®cantly, (p40.05) lower in yellowness b*, than the other two classes. Examination of the dried CWRW: Rye blend noodles with increased substitution of CWES ¯our indicated that there was no signi®cant decrease in noodle brightness until the CWES component reached 40% (results not shown). No discernible dierence on the basis of CWES composition was detected for redness while yellowness, b*, could only be signi®cantly (p40.05) noticed at a level of 70% substitution. These results would suggest that CWES substitution up to at least 50% in a 70:30 CWRW:Rye noodle would not be visually distinguishable.
Fig. 3. In¯uence of increasing rye ¯our incorporation on the color components of dry white salted noodles prepared with CWRS and CWRW ¯ours. Means (n=2) with dierent letters within a wheat class are signi®cantly dierent (p40.05).
Dry noodle breaking strength The eect of substituting CWES for CWRW ¯our in a 70:30 blend of CWRW: rye ¯our is shown in Fig. 5A. At an incorporation levels of 20% CWES, there was a signi®cant (p40.05) increase in breaking strength over the initial CWRW:Rye blend and the 10% CWES sample. Subsequent additions of CWES did not appear to cause any substantial further increases in breaking strength. It can be noted, however, that addition of the CWES ¯our has resulted in a breaking strength similar to
32
J. E. Kruger et al.
the breaking strengthen found for noodles made from CWRW wheat ¯our containing no rye ¯our (Fig. 4A). Noodle texture Cooked noodle ®rmness, expressed as MCS, was found to be extremely responsive to the substitution of CWES ¯our (r=0.99, p=0.0001). Even at the 10% level there was a signi®cant, (p40.05) increase in ®rmness (Fig. 5B). The ability to enhance textural quality was clearly evident at a level of 40% where the MCS value of the blended noodle was greater than that achieved by pure CWRW. Further substitution continued to signi®cantly increase ®rmness.
Fig. 4. In¯uence of increasing rye ¯our incorporation on the textural characteristics of dry white salted noodles prepared with CWRS and CWRW ¯ours. Means (n=2) with dierent letters within a wheat class are signi®cantly dierent (p40.05).
Chewiness (REC) of the blended noodle also behaved in a similar manner signi®cantly increasing with the substitution of CWES ¯our (r=0.97, p=0.001, Fig. 5C). Unlike ®rmness, however, the additions of CWES had a more gradual eect on recovery. A complete replacement of CWRW with CWES was required for the wheat:rye (70:30) blended noodle to achieve a REC value greater than 100% CWRW.
Fig. 5. The eect on the textural attributes of 70:30 CWRW:Rye blended noodles by the substitution of CWES ¯our for CWRW ¯our. Means (n=2) on the same line with dierent letters are signi®cantly dierent (p40.05).
The eect of incorporation of rye ¯our on the quality of oriental noodles
33
In¯uence of peroxide addition Rye ¯our is rich in arabinoxylans and it has been established, with wheat at least, that oxidative gelation results in the cross-linking of these polymers (Neukom and Warkwalder, 1978). Hydrogen peroxide is one oxidant which can eect this reaction resulting in an increase in viscosity (Hoseney and Faubion, 1981). Wheat ¯our peroxidase or tyrosinase are catalysts for the reaction. The eect that such oxidative cross-linking would have in strengthening the gel matrix of noodles is unknown and was evaluated on the 70:30 CWRW:Rye blend and the CWRW control ¯ours. Hydrogen peroxide was added at the mixing stage of noodle processing and the resulting eects on cooked noodle texture examined. Since hydrogen peroxide is also a bleaching agent, it was of interest to see if the color of such noodles might also improve. Noodle color The eect of adding hydrogen peroxide at 0.5, 1.0 and 1.5% levels on the color of dry noodles prepared with a CWRW:Rye (70:30) ¯our and a CWRW control ¯our are shown in Fig. 6. A signi®cant (p40.05) improvement in noodle brightness was achieved, particularly with the wheat:rye ¯our blend. Redness, a* and yellowness, b* on the other hand, showed no signi®cant improvement in the wheat:rye ¯our blend although there was a signi®cant (p40.05) decrease in redness with the CWRW control ¯our. Noodles prepared from both ¯ours at 0.5% hydrogen peroxide concentration displayed large eects on color which were not signi®cantly enhanced at higher concentrations. Dry noodle breaking strength Dry noodle breaking strength was found to be signi®cantly (p40.05) reduced in the presence of hydrogen peroxide (Fig. 7A). Noodle texture The addition of hydrogen peroxide resulted in a signi®cant (p40.05) increase in the ®rmness, MCS, of both the wheat:rye blend and the control CWRW noodles (Fig. 7B). Chewiness, REC, on the other hand, increased signi®cantly (p40.05) only at the 0.5% level (Fig. 7C). Since a concentration of 0.5% hydrogen peroxide seemed sucient to increase ®rmness the extent to which a lower concentration would suce was also evaluated (results not shown). As little as 0.1% hydrogen peroxide was able to exert the same eect on texture as a concentration of 0.5%. In¯uence of peroxidase The enzyme peroxidase, which can catalyze the crosslinking of pentosans through the oxidation their phenolic acids, was added to the 70:30 CWRW:Rye blend
Fig. 6. The eect of hydrogen peroxide additions on the color components of dry noodles prepared with CWRW:Rye (70:30) blended ¯our and CWRW control ¯our. Means (n=2) with different letters, within a ¯our, are signi®cantly dierent (p40.05).
in combination with peroxide to determine if further enhancements of the color and textural traits of the noodles could be improved. Experiments were carried out to determine whether additional peroxidase over and above that present in wheat ¯our would have an additional eect in ®rming noodles prepared with 70:30 wheat:rye ¯our blend. Addition of horseradish peroxidase (25, 000 units) in the presence or absence of a 1% peroxide solution was found, however, to have negligible eects (results not shown).
34
J. E. Kruger et al. Negative eects on textural traits such as ®rmness and chewiness do occur with rye ¯our incorporation but the eects may be minimized or negated by using a wheat ¯our containing good dough strength such as CWES. An improvement in color can also be achieved by the addition of a bleaching agent such as hydrogen peroxide with some concomitant improvement in textural properties. Consumer acceptance studies will be necessary, of course, to evaluate whether noodles made with rye ¯our will ultimately be welcomed in the marketplace. ACKNOWLEDGEMENTS The authors wish to gratefully acknowledge the assistance of: Mr. Ashok Sarkar of the Canadian International Grains Institute for providing us with high quality patent ¯ours prepared on their commercial pilot mill and Helena Facto, GRL, for the preparation of the noodles. REFERENCES
Fig. 7. The in¯uence of hydrogen peroxide addition on the textural attributes of dry white salted noodles prepared with CWRW or CWRW:Rye (70:30) blended ¯ours. Means (n=2) with dierent letters, within a ¯our, are signi®cantly dierent (p40.05).
CONCLUSIONS It is possible to produce noodles of acceptable color and texture from wheat ¯our containing up to at least 30% rye ¯our. In general, additions of rye ¯our will result in noodles with a duller but still acceptable color at a 30% blend. The primary impact on dry noodle color, prepared from wheat:rye blends, is upon brightness, L*, while redness and yellowness, although decreasing upon rye addition, are not in¯uenced by its concentration.
American Association of Cereal Chemists. (1983) Approved Methods of the AACC, 8th edn. Ash Method 08-01, revised 1976; Farinograph Method 54±20, revised 1982; Amylogram Method 22±10, approved 1960. The Association, St. Paul. MN. Baik, B.-K., Czuchajowska, Z. and Pomeranz, Y. (1995) Discoloration of dough for oriental noodles. Cereal Chem. 72, 198±205. Black, H. C. (1980) The GRL pilot mill. Assoc. Oper. Millers Bull. Sept., 3834±3837. Boros, D. (1995) Arabinoxylans: the cell wall components decisive for the nutritional value of rye. In VTT Symposium 161: International Rye Symposium: Technology and Products. eds. K. Poutanen and K. Autio, pp. 111±120. VTT Technical Research Centre of Finland, Espoo, Finland. Drews, E. and Seibel, W. (1976) Bread baking and other uses around the World. In Rye: Production, Chemistry, and Technology, ed. W. Bushuk, pp. 127±1780. American Association of Cereal Chemists, St. Paul, Minnesota Feldheim, W. and Wisker, E. (1995) Nutritional aspects of rye. In VTT Symposium 161: International Rye Symposium: Technology and Products, eds. K. Poutanen and K. Autio, pp. 83±102. VTT Technical Research Centre of Finland, Espoo, Finland. Hallmans, G., Zhang, J., Lundin, E., Landstrom, M., Sylvan, A., Aman, P., Adlercreutz, H., Harkonen, H. and Knudsen, K. N. E. B. (1995) The eect of rye on bile acid metabolism and phyoestrogens. In VTT Symposium 161: International Rye Symposium: Technology and Products, eds. K. Poutanen and K. Autio, pp. 61±760. VTT Technical Research Centre of Finland, Espoo, Finland. Hatcher, D. W. and Kruger, J. E. (1993) Distribution of polyphenol oxidase in ¯our millstreams of Canadian common wheat classes milled to three extraction rates. Cereal Chem. 70, 51±55. Hoseney, R. C. and Faubion, J. M. (1981) A mechanism for the oxidative gelation of wheat ¯our water-soluble pentosans. Cereal Chem. 58, 421±424. Knudsen, K. E. B., Johansen, H. N. and Glitso, V. (1995) Gastrointestinal implication of rye dietary ®ber. In VTT Symposium 161: International Rye Symposium: Technology
The eect of incorporation of rye ¯our on the quality of oriental noodles and Products, eds. K. Poutanen and K. Autio, pp. 83±92. VTT Technical Research Centre of Finland, Espoo, Finland. Kruger, J. E. and Tipples, K. H. (1981) A modi®ed procedure for use of the Perkin-Elmer model 191 grain amylase analyzer in determining low levels of alpha-amylase in wheats and ¯ours. Cereal Chem. 58, 271±274. Kruger, J. E., Matsuo, R. R. and Preston, K. (1992) A comparison of methods for the prediction of Cantonese noodle color. Can. J. Plant Sci. 72, 1021±1029. Kruger, J. E., Anderson, M. H. and Dexter, J. E. (1994) Eect of ¯our re®nement on raw Cantonese noodle color texture. Cereal Chem 71, 177±182. Kruger, J. E., Hatcher, D. W. and Dexter, J. E. (1995) In¯uence of sprout damage on oriental noodle quality. In Seventh International Symposium on Pre-Harvest Sprouting in Cereals, eds. Kaz. Noda and D. J. Mares, pp. 9±180. Center for Academic Societies Japan, Osaka, Japan. Miskelly, D. M. (1984) Flour components aecting pasta and noodle color. J. Sci.Food Agric. 35, 463±471. Miskelly, D. M. and Moss, H. J. (1985) Flour quality requirements for Chinese noodle manufacture. J. Cereal Sci. 3, 379±387. Moss, H. J., Miskelly, D. M. and Moss, R. (1986) The eect of alkaline conditions on the properties of wheat ¯our dough and Cantonese-style noodles. J. Cereal Sci. 4, 261±268. Neukom, H. and Markwalder, H. U. (1978) Oxidative gelation of wheat ¯our pentosans: a new way of cross-linking polymers. Cereal Foods 23, 374±376.
35
Oh, N. H., Sieb, P. A., Deyoe, C. W. and Ward, A. B. (1983) Noodles: I. Measuring the textural characteristics of cooked noodles. Cereal Chem. 60, 433±438. Oh, N. H., Sieb, P. A., Deyoe, C. W. and Ward, A. B. (1985a) Noodles: II. The surface ®rmness of cooked noodles from soft and hard wheat ¯ours. Cereal Chem. 62, 431±436. Oh, N. H., Sieb, P. A. and Chung, D. S. (1985b) Noodles: III. Eects of processing variables on quality characteristics of dry noodles. Cereal Chem. 62, 437±440. Oh, N. H., Sieb, P. A., Ward, A. B. and Deyoe, C. W. (1985c) Noodles: IV. In¯uence of ¯our protein, extraction rate, particle size, and starch damage on the quality characteristics of dry noodles. Cereal Chem. 62, 441±446. Toyokawa, H., Rubenthaler, G. L., Powers, J. R. and Schanus, E. G. (1989a) Japanese noodle qualities: I. Flour components. Cereal Chem. 66, 382±386. Toyokawa, H., Rubenthaler, G. L., Powers, J. R. and Schanus, E. G. (1989b) Japanese noodle qualities: I. Flour components. Cereal Chem. 66, 387±391. Williams, P. C. (1973) The use of titanium dioxide as catalyst for large-scale Kjeldahl determination of total nitrogen content of cereal grains. J. Sci. Food Agric. 24, 343±348.
(Received 26 September 1997; accepted 27 June 1998)
The eect of incorporation of rye ¯our on the quality of oriental noodles J. E. Kruger, D. W. Hatcher* & M. J. Anderson Grain Research Laboratory, Canadian Grain Commission, 1404-303 Main St. Winnipeg, Manitoba, Canada R3C 3G8
Salted noodles were prepared using Canadian Western Red Winter (CWRW) or Canadian Western Red Spring (CWRS) patent ¯ours augmented with 15, 30 and 50% rye ¯our. Addition of incremental amounts of rye ¯our resulted in signi®cant decreases in both raw and dried noodle brightness, L*, and yellowness, b*. In addition, dry noodle breaking strength, cooked noodle ®rmness, (MCS), and chewiness (REC) also decreased with increasing rye content. However, an acceptable wheat:rye noodle was still possible with a rye incorporation of 30%. Proportional substitution of high gluten strength ¯our from the Canadian Western Extra Stron (CWES) class of wheat in exchange for CWRW ¯our had no signi®cant impact on noodle color but did signi®cantly (p40.05) improve the textural attributes, especially ®rmness, of the 70:30 wheat:rye blended noodles. The addition of peroxide at a 0.5% concentration was found to signi®cantly improve wheat:rye blended noodle brightness and ®rmness. The use of peroxidase in the presence or absence of peroxide had no impact on the wheat:rye noodle quality characteristics. # 1998 Canadian Institute of Food Science and Technology. Published by Elsevier Science Ltd. All rights reserved Keywords: rye, noodles, color, texture.
INTRODUCTION
Wisker, 1995). Preliminary ®ndings have also indicated that rye may reduce cancer in laboratory animals (Hallmans et al., 1995). Boros (1995) has stated that the rye arabinoxylans are one of the major components contributing to the nutritional value of this cereal. The objective of this study was to examine the potential of incorporating increasing amounts of rye ¯our with high quality patent wheat ¯ours in order to produce dried salted noodles. Of particular importance were the eects on noodle color and textural attributes, important discriminating criteria which impact heavily on commercial noodle quality (Miskelly, 1984; Miskelly and Moss, 1985; Oh et al., 1983, 1985a; 1985b; Moss et al., 1986; Toyokawa et al., 1989a; Toyokawa et al., 1989b; Kruger et al., 1992; 1994; 1995; Baik et al., 1995). A secondary purpose was to determine the extent to which the properties of such noodles could be modi®ed by the incorporation of selected ingredients such as ¯our from another class, peroxide and peroxide in combination with peroxidase.
The demand for new niche market noodle products continues to increase in south east Asia as the economies of the respective countries improve. As the gross domestic product, GDP, per capita rises, consumers are now considering secondary features such as health and nutritional aspects of the products they eat. Most Asian markets prefer their noodle products to be made from high quality patent wheat ¯ours. However, the Japanese soba noodle, prepared from buckwheat ¯our, is decidedly colored and has established itself as a viable niche market. Rye (Secale cereale L.) ¯our may have many of the potential health bene®ts attributed to oats. This cereal is known to contain many essential and nonessential dietary components and is a particularly important dietary source of ®ber in Northern and Eastern Europe (Knudsen et al., (1995); Feldheim and *To whom corresondence should be addressed. Fax: +1-204983-0724; e.mail:[email protected] Paper #774 of the Grain Research Laboratory. 27
28
J. E. Kruger et al.
METHODS
Noodle preparation
Flours
Noodles were prepared using the method previously described by Kruger et al., (1994). A 1% salt solution (containing hydrogen peroxide and/or peroxidase in selected experiments) was added to 200 g of ¯our in a Hobart N50 mixer (Hobart Canada, North York, ON) over a 30 s interval at the slow speed setting to achieve a ®nal water absorption of 32%. An additional 30 s slow mixing was followed by a 1 min medium setting mix before returning to the slow setting for an additional 3 min. The mixture was then sheeted on an Ohtake laboratory noodle machine (Ohtake, Tokyo, Japan) with an initial gap setting of 3 mm. Two passes were made at this setting with the noodle sheet being folded between passes to ensure homogeneity. A representative 25 cm long section of the noodle sheet was utilized in the subsequent sheeting passes. Seven sheetings with gap settings of 3, 2.55, 2.15, 1.85, 1.57, 1.33 and 1.10 mm were carried out. Total force of individual sheetings was measured via a Labmaster DMA analog-digital board (Scienti®c Solutions, Solon, OH) interfaced to a personal computer using Labtech Notebook software (Laboratories Technologies, Wilmington, MA) to ensure reproducibility between replicate sheetings. The noodle sheet was cut into two portions; one being used for time dependent, raw noodle color measurements while the second portion was passed through the Ohtake cutting blades yielding 2.7 mm wide noodle strands. A portion of these strands were cut into 5 cm lengths, cooked and underwent textural analyses. Dried noodles were prepared in a temperature and humidity controlled drying oven (Conviron, Winnipeg, MB, Canada) for 16 h before being stored a minimum of 2 weeks at 24 C prior to cooking and texture evaluation.
Wheats representing dierent classes of Canadian wheat grown on the Western Prairies; Canadian Western Red Spring (CWRS), Canadian Western Red Winter (CWRW) and Canadian Western Extra Strong (CWES) were milled on the Canadian International Grains Institute (CIGI) pilot mill using a commercial ¯ow operation. Individual streams were composited on the basis of increasing ash to yield high quality patent ¯ours (0.37±0.51% ash). The rye sample was a composite blend of material grown across western Canada, selected from harvest survey samples of 1995, and was milled on the Grain Research Laboratory research mill (Black, 1980). Only breaks and sizings (1±4) from the rye ¯our millstreams were pooled in order to minimize a-amylase and polyphenol oxidase (PPO) activities in the composite rye ¯our (Fig. 1). Analytical results of the ¯ours used in this study can be found in Table 1. Blended ¯ours consisting of 15, 30 and 50% rye ¯our were prepared by incorporating the rye ¯our, on a weight basis, with both CWRW and CWRS ¯ours. A special blend series, composed of 30% rye ¯our and 70% wheat ¯our, in which the composition of CWES and CWRW ¯ours was changed incrementally, was prepared to study the in¯uence of protein strength on noodle quality. Analytical methods Protein content (%N5.7) was determined by the Kjeldahl method, as modi®ed by Williams, (1973); ash content, farinograph and starch damage were determined by AACC methods, (1983) 08±01, 54±21 and 76±30A respectively. Polyphenol oxidase levels were determined by the method of Hatcher and Kruger, (1993) while amylase was determined by the nephelometric method of Kruger and Tipples, (1981).
Table 1. Analytical properties of the ¯ours used in the preparation of oriental noodles Flour Properties Moisture % Protein % Ash % Starch Damagec Farinographb Absorption % Development Time (min) Mix. tolerance Index (B.U.) Stability (min) a
Fig. 1. Levels of polyphenol oxidase (PPO) and amylase activity in the rye ¯our mill streams. *Polyphenol oxidase ~ -amylase.
CWES CWRS CWRW
CWRW: Rye rye blenda
14.2 11.4 0.51
12.5 12.4 0.42
11.8 9.6 0.37
12.1 8.9 0.51
12.8 8.0 0.81
9.0
7.0
5.5
5.3
5.2
59.4
58.1
52.5
52.6
11.50
4.25
2.00
4.25
15 40.0
40 8.50
40 9.00
55 7.00
(CWRW: rye 70:30 blend). Farinograph was carried out at 65 rpm for all samples except CWES where 90 rpm was used. c Starch damage expressed in A.A.C.C. units. b
The eect of incorporation of rye ¯our on the quality of oriental noodles Drying conditions consisted of an initial cabinet temperature of 25 C maintained for the ®rst 1.5 h followed by 2 h at 35 C with the remaining time being spent at 25 C. Relative humidity was maintained at 90% for the ®rst 3 h followed by a 4.5 h linear decline to 60% with the remaining 8.5 h maintained at 55%. Noodle color measurement Noodle color was measured with a Labscan II spectrocolorimeter (HunterLab, Reston, VA) equipped with a D65 illuminant using the CIE 1976 L*, a* and b* color scale. Measurements were made in triplicate at two random locations on the surface for each sample at 0, 2 and 24 h. For white salted noodles, high values of L* are preferred. A consumer preference for a slightly creamy color requires moderate yellow, b*, values while extremes on either side of the red, a*, scale are considered deleterious. Dry noodle breaking strength Breaking strength of individual noodle strands was determined by a 1 mm wide blade ®xture attached to the Instron Universal Testing Machine (IUTM model 4201, Instron, Canton, MA) traveling at 100 mm minÿ1 as per the method of Oh et al. (1985b). Two replications were carried out for each noodle series with each replication being the average of ten individual measurements. Texture measurement Noodles were optimally cooked, cooled for 1 min under running distilled water, drained, and stored for exactly 10 min at 25 C as described by Kruger et al., (1994) prior to textural analysis. The 10 min storage period was utilized as previous work (Kruger et al., 1994) has shown the need to standardize the time after cooking in order to achieve reproducible results. Optimal cook times for the CWRS and CWRW wheat ¯ours, respectively, were 16 and 11 min as determined by the disappearance of the noodle core when squeezed between lexan plates. Cook times decreased with increasing admixtures of rye ¯our. Textural measurements, recovery and maximum cutting strength (MCS) were carried out on cooked noodles using an the IUTM model 4201 with ®xtures and procedures similar to those described by Oh et al. (1983), (1985a) and Kruger et al. (1994). Analyses were carried out on ®ve sets of three noodles with the data being averaged for each duplicate cooking done on separate days. Statistical analysis All statistical analyses; regression and analysis of variance, were carried out utilizing SAS (SAS Institute, Cary, NC, version 6.10) statistical software.
29
RESULTS Blending of rye and wheat ¯ours Selection of mill streams for rye ¯our Examination of Fig. 1 reveals that the levels of amylase and polyphenol oxidase in the rye ¯our mill streams increase considerably in the later mill streams. The same phenomena occurs in wheat and Hatcher and Kruger, (1993) have shown that the levels of PPO are signi®cantly reduced by the degree of ¯our re®nement. The pooling of the rye break ¯ours plus sizings (1±4) suggests a natural break in the distribution of these enzymes although PPO levels are 50 times greater than normally found in a patent wheat ¯our and -amylase levels are three-fold higher. Noodle Color The in¯uence of time dependent color changes in raw noodles prepared by incorporating rye ¯our with either CWRS or CWRW patent ¯ours can be seen in Fig. 2. Signi®cant linear decreases, p40.05, in raw noodle brightness were observed with progressive increases in rye ¯our content for both CWRS and CWRW noodles (Fig. 2 A and D). There were noticeable increases in the rate of change in brightness with increasing levels of rye ¯our. Coincident with this was a general increase in raw noodle redness, a*, (Fig. 2B and E) and decreases in yellowness, b*, (Fig. 2C and F). The observed changes can be attributed to two factors. One is the direct in¯uence of naturally occurring colored components in ryes such as ¯avonoids which increase with higher rye content in the admixture. The second factor is the higher level of PPO activity in rye ¯our which would account for the increased rate of decline in brightness associated with greater rye ¯our content. Previous research with Cantonese noodles has indicated a strong relationship between changes in raw noodle brightness, L*, and PPO levels in wheat ¯ours (Kruger et al., 1994). The above results indicate that in preparing dried white salted noodles containing rye ¯our, the time after preparation of the noodles and before drying should be minimized. However, it is generally not possible to shorten the actual drying regime without some compromise to noodle quality, particularly if stress related cracks occur due to rapid drying. The eect of the 16 h drying under controlled temperature and humidity on dried white salted noodles is shown in Fig. 3. The dried noodles were found to have a decreased brightness compared to their 0 and 2 h raw noodle counterparts but were signi®cantly brighter (Fig. 3a) than those allowed to stand for 24 h as might be expected. Dried noodles prepared with both CWRS and CWRW ¯ours had decreases in brightness with increasing rye content that were signi®cant, p40.05, in most cases. Analysis of the red color component, a*, and the yellow component,
30
J. E. Kruger et al.
b*, indicated that for both CWRS and CWRW, signi®cantly, p40.05, dierent values were only found between the pure wheat ¯our noodles and those containing rye blends. The incremental changes observed above with rye incorporation were also apparent by visual examination. In general the noodles took on a brownish but not undesirable appearance with no obvious green or reddish hues at levels up to 30% rye ¯our in the blends.
Dry noodle breaking strength Noodles with rye ¯our incorporation in the wheat ¯our blend broke more easily than wheat ¯our noodles and the eect was progressive with increasing rye ¯our in the admixtures (Fig. 4A). This was particularly noticeable with CWRS ¯our noodles which although substantially stronger than CWRW ¯our noodles displayed a greater decline with increasing rye ¯our addition. At 50% rye ¯our addition both classes of noodles had approximately equivalent breaking strength.
Fig. 2. Time dependent color changes in raw noodles prepared by incorporating rye ¯our with CWRS and CWRW ¯ours. * 0 h & 2 h ~ 24 h Means (n=2) on the same line with dierent letters are signi®cantly dierent (p40.05).
The eect of incorporation of rye ¯our on the quality of oriental noodles Cooked noodle texture Both cooked noodles' ®rmness, (MCS) and chewiness, (REC), as de®ned by Oh et al., (1983), decreased with increasing rye content in the blends (Fig. 4B and C). For both CWRS and CWRW even as little as 15% rye ¯our addition caused a signi®cant (p40.05) decline in these textural attributes. The explanation for these results and those for decreased breaking strength can be partially explained by the widely dierent nature in the functional proteins of rye and wheat. Examination of the properties of rye ¯our compared to wheat ¯our (Table 1) indicates that the amount of protein is considerably less
31
in the former. Furthermore it is well known that rye proteins cannot form gluten after mixing in water (Drews and Seibel, 1976). In the case of dough sheeting, this means that rye proteins cannot contribute to the overall matrix of proteins that improve noodle textural properties. Oh and co-workers (1985c) for example, have established the strong relationships that exist between the amount of protein, as well as protein strength characteristics, on noodle ®rmness and chewiness. Addition of CWES ¯our to CWRW: rye blended ¯our One remedial way to minimize the eects on breaking strength and texture observed above would be to add wheat ¯our which had increased dough strength. The CWES class is appropriately named to represent those wheat varieties with similar protein content to that of CWRS but having stronger gluten. As indicated in Table 1, it is necessary to mix at 90 rpm rather than 65 rpm in the farinograph to develop this dough fully. Experiments were carried out, therefore, in which varying proportions of CWRW ¯our, previously shown to be easily broken, were substituted with CWES ¯our, in 10% increments, in a 70:30 blend of CWRW and rye. Noodle color To obtain an indication of any potential negative impact on color due to adding CWES ¯our, dried noodles were prepared using this ¯our by itself. Brightness, L*, and redness, a*, of CWES (100%) dry noodles were found to be equivalent to the CWRW and CWRS dried noodles. The CWES noodles, however, were signi®cantly, (p40.05) lower in yellowness b*, than the other two classes. Examination of the dried CWRW: Rye blend noodles with increased substitution of CWES ¯our indicated that there was no signi®cant decrease in noodle brightness until the CWES component reached 40% (results not shown). No discernible dierence on the basis of CWES composition was detected for redness while yellowness, b*, could only be signi®cantly (p40.05) noticed at a level of 70% substitution. These results would suggest that CWES substitution up to at least 50% in a 70:30 CWRW:Rye noodle would not be visually distinguishable.
Fig. 3. In¯uence of increasing rye ¯our incorporation on the color components of dry white salted noodles prepared with CWRS and CWRW ¯ours. Means (n=2) with dierent letters within a wheat class are signi®cantly dierent (p40.05).
Dry noodle breaking strength The eect of substituting CWES for CWRW ¯our in a 70:30 blend of CWRW: rye ¯our is shown in Fig. 5A. At an incorporation levels of 20% CWES, there was a signi®cant (p40.05) increase in breaking strength over the initial CWRW:Rye blend and the 10% CWES sample. Subsequent additions of CWES did not appear to cause any substantial further increases in breaking strength. It can be noted, however, that addition of the CWES ¯our has resulted in a breaking strength similar to
32
J. E. Kruger et al.
the breaking strengthen found for noodles made from CWRW wheat ¯our containing no rye ¯our (Fig. 4A). Noodle texture Cooked noodle ®rmness, expressed as MCS, was found to be extremely responsive to the substitution of CWES ¯our (r=0.99, p=0.0001). Even at the 10% level there was a signi®cant, (p40.05) increase in ®rmness (Fig. 5B). The ability to enhance textural quality was clearly evident at a level of 40% where the MCS value of the blended noodle was greater than that achieved by pure CWRW. Further substitution continued to signi®cantly increase ®rmness.
Fig. 4. In¯uence of increasing rye ¯our incorporation on the textural characteristics of dry white salted noodles prepared with CWRS and CWRW ¯ours. Means (n=2) with dierent letters within a wheat class are signi®cantly dierent (p40.05).
Chewiness (REC) of the blended noodle also behaved in a similar manner signi®cantly increasing with the substitution of CWES ¯our (r=0.97, p=0.001, Fig. 5C). Unlike ®rmness, however, the additions of CWES had a more gradual eect on recovery. A complete replacement of CWRW with CWES was required for the wheat:rye (70:30) blended noodle to achieve a REC value greater than 100% CWRW.
Fig. 5. The eect on the textural attributes of 70:30 CWRW:Rye blended noodles by the substitution of CWES ¯our for CWRW ¯our. Means (n=2) on the same line with dierent letters are signi®cantly dierent (p40.05).
The eect of incorporation of rye ¯our on the quality of oriental noodles
33
In¯uence of peroxide addition Rye ¯our is rich in arabinoxylans and it has been established, with wheat at least, that oxidative gelation results in the cross-linking of these polymers (Neukom and Warkwalder, 1978). Hydrogen peroxide is one oxidant which can eect this reaction resulting in an increase in viscosity (Hoseney and Faubion, 1981). Wheat ¯our peroxidase or tyrosinase are catalysts for the reaction. The eect that such oxidative cross-linking would have in strengthening the gel matrix of noodles is unknown and was evaluated on the 70:30 CWRW:Rye blend and the CWRW control ¯ours. Hydrogen peroxide was added at the mixing stage of noodle processing and the resulting eects on cooked noodle texture examined. Since hydrogen peroxide is also a bleaching agent, it was of interest to see if the color of such noodles might also improve. Noodle color The eect of adding hydrogen peroxide at 0.5, 1.0 and 1.5% levels on the color of dry noodles prepared with a CWRW:Rye (70:30) ¯our and a CWRW control ¯our are shown in Fig. 6. A signi®cant (p40.05) improvement in noodle brightness was achieved, particularly with the wheat:rye ¯our blend. Redness, a* and yellowness, b* on the other hand, showed no signi®cant improvement in the wheat:rye ¯our blend although there was a signi®cant (p40.05) decrease in redness with the CWRW control ¯our. Noodles prepared from both ¯ours at 0.5% hydrogen peroxide concentration displayed large eects on color which were not signi®cantly enhanced at higher concentrations. Dry noodle breaking strength Dry noodle breaking strength was found to be signi®cantly (p40.05) reduced in the presence of hydrogen peroxide (Fig. 7A). Noodle texture The addition of hydrogen peroxide resulted in a signi®cant (p40.05) increase in the ®rmness, MCS, of both the wheat:rye blend and the control CWRW noodles (Fig. 7B). Chewiness, REC, on the other hand, increased signi®cantly (p40.05) only at the 0.5% level (Fig. 7C). Since a concentration of 0.5% hydrogen peroxide seemed sucient to increase ®rmness the extent to which a lower concentration would suce was also evaluated (results not shown). As little as 0.1% hydrogen peroxide was able to exert the same eect on texture as a concentration of 0.5%. In¯uence of peroxidase The enzyme peroxidase, which can catalyze the crosslinking of pentosans through the oxidation their phenolic acids, was added to the 70:30 CWRW:Rye blend
Fig. 6. The eect of hydrogen peroxide additions on the color components of dry noodles prepared with CWRW:Rye (70:30) blended ¯our and CWRW control ¯our. Means (n=2) with different letters, within a ¯our, are signi®cantly dierent (p40.05).
in combination with peroxide to determine if further enhancements of the color and textural traits of the noodles could be improved. Experiments were carried out to determine whether additional peroxidase over and above that present in wheat ¯our would have an additional eect in ®rming noodles prepared with 70:30 wheat:rye ¯our blend. Addition of horseradish peroxidase (25, 000 units) in the presence or absence of a 1% peroxide solution was found, however, to have negligible eects (results not shown).
34
J. E. Kruger et al. Negative eects on textural traits such as ®rmness and chewiness do occur with rye ¯our incorporation but the eects may be minimized or negated by using a wheat ¯our containing good dough strength such as CWES. An improvement in color can also be achieved by the addition of a bleaching agent such as hydrogen peroxide with some concomitant improvement in textural properties. Consumer acceptance studies will be necessary, of course, to evaluate whether noodles made with rye ¯our will ultimately be welcomed in the marketplace. ACKNOWLEDGEMENTS The authors wish to gratefully acknowledge the assistance of: Mr. Ashok Sarkar of the Canadian International Grains Institute for providing us with high quality patent ¯ours prepared on their commercial pilot mill and Helena Facto, GRL, for the preparation of the noodles. REFERENCES
Fig. 7. The in¯uence of hydrogen peroxide addition on the textural attributes of dry white salted noodles prepared with CWRW or CWRW:Rye (70:30) blended ¯ours. Means (n=2) with dierent letters, within a ¯our, are signi®cantly dierent (p40.05).
CONCLUSIONS It is possible to produce noodles of acceptable color and texture from wheat ¯our containing up to at least 30% rye ¯our. In general, additions of rye ¯our will result in noodles with a duller but still acceptable color at a 30% blend. The primary impact on dry noodle color, prepared from wheat:rye blends, is upon brightness, L*, while redness and yellowness, although decreasing upon rye addition, are not in¯uenced by its concentration.
American Association of Cereal Chemists. (1983) Approved Methods of the AACC, 8th edn. Ash Method 08-01, revised 1976; Farinograph Method 54±20, revised 1982; Amylogram Method 22±10, approved 1960. The Association, St. Paul. MN. Baik, B.-K., Czuchajowska, Z. and Pomeranz, Y. (1995) Discoloration of dough for oriental noodles. Cereal Chem. 72, 198±205. Black, H. C. (1980) The GRL pilot mill. Assoc. Oper. Millers Bull. Sept., 3834±3837. Boros, D. (1995) Arabinoxylans: the cell wall components decisive for the nutritional value of rye. In VTT Symposium 161: International Rye Symposium: Technology and Products. eds. K. Poutanen and K. Autio, pp. 111±120. VTT Technical Research Centre of Finland, Espoo, Finland. Drews, E. and Seibel, W. (1976) Bread baking and other uses around the World. In Rye: Production, Chemistry, and Technology, ed. W. Bushuk, pp. 127±1780. American Association of Cereal Chemists, St. Paul, Minnesota Feldheim, W. and Wisker, E. (1995) Nutritional aspects of rye. In VTT Symposium 161: International Rye Symposium: Technology and Products, eds. K. Poutanen and K. Autio, pp. 83±102. VTT Technical Research Centre of Finland, Espoo, Finland. Hallmans, G., Zhang, J., Lundin, E., Landstrom, M., Sylvan, A., Aman, P., Adlercreutz, H., Harkonen, H. and Knudsen, K. N. E. B. (1995) The eect of rye on bile acid metabolism and phyoestrogens. In VTT Symposium 161: International Rye Symposium: Technology and Products, eds. K. Poutanen and K. Autio, pp. 61±760. VTT Technical Research Centre of Finland, Espoo, Finland. Hatcher, D. W. and Kruger, J. E. (1993) Distribution of polyphenol oxidase in ¯our millstreams of Canadian common wheat classes milled to three extraction rates. Cereal Chem. 70, 51±55. Hoseney, R. C. and Faubion, J. M. (1981) A mechanism for the oxidative gelation of wheat ¯our water-soluble pentosans. Cereal Chem. 58, 421±424. Knudsen, K. E. B., Johansen, H. N. and Glitso, V. (1995) Gastrointestinal implication of rye dietary ®ber. In VTT Symposium 161: International Rye Symposium: Technology
The eect of incorporation of rye ¯our on the quality of oriental noodles and Products, eds. K. Poutanen and K. Autio, pp. 83±92. VTT Technical Research Centre of Finland, Espoo, Finland. Kruger, J. E. and Tipples, K. H. (1981) A modi®ed procedure for use of the Perkin-Elmer model 191 grain amylase analyzer in determining low levels of alpha-amylase in wheats and ¯ours. Cereal Chem. 58, 271±274. Kruger, J. E., Matsuo, R. R. and Preston, K. (1992) A comparison of methods for the prediction of Cantonese noodle color. Can. J. Plant Sci. 72, 1021±1029. Kruger, J. E., Anderson, M. H. and Dexter, J. E. (1994) Eect of ¯our re®nement on raw Cantonese noodle color texture. Cereal Chem 71, 177±182. Kruger, J. E., Hatcher, D. W. and Dexter, J. E. (1995) In¯uence of sprout damage on oriental noodle quality. In Seventh International Symposium on Pre-Harvest Sprouting in Cereals, eds. Kaz. Noda and D. J. Mares, pp. 9±180. Center for Academic Societies Japan, Osaka, Japan. Miskelly, D. M. (1984) Flour components aecting pasta and noodle color. J. Sci.Food Agric. 35, 463±471. Miskelly, D. M. and Moss, H. J. (1985) Flour quality requirements for Chinese noodle manufacture. J. Cereal Sci. 3, 379±387. Moss, H. J., Miskelly, D. M. and Moss, R. (1986) The eect of alkaline conditions on the properties of wheat ¯our dough and Cantonese-style noodles. J. Cereal Sci. 4, 261±268. Neukom, H. and Markwalder, H. U. (1978) Oxidative gelation of wheat ¯our pentosans: a new way of cross-linking polymers. Cereal Foods 23, 374±376.
35
Oh, N. H., Sieb, P. A., Deyoe, C. W. and Ward, A. B. (1983) Noodles: I. Measuring the textural characteristics of cooked noodles. Cereal Chem. 60, 433±438. Oh, N. H., Sieb, P. A., Deyoe, C. W. and Ward, A. B. (1985a) Noodles: II. The surface ®rmness of cooked noodles from soft and hard wheat ¯ours. Cereal Chem. 62, 431±436. Oh, N. H., Sieb, P. A. and Chung, D. S. (1985b) Noodles: III. Eects of processing variables on quality characteristics of dry noodles. Cereal Chem. 62, 437±440. Oh, N. H., Sieb, P. A., Ward, A. B. and Deyoe, C. W. (1985c) Noodles: IV. In¯uence of ¯our protein, extraction rate, particle size, and starch damage on the quality characteristics of dry noodles. Cereal Chem. 62, 441±446. Toyokawa, H., Rubenthaler, G. L., Powers, J. R. and Schanus, E. G. (1989a) Japanese noodle qualities: I. Flour components. Cereal Chem. 66, 382±386. Toyokawa, H., Rubenthaler, G. L., Powers, J. R. and Schanus, E. G. (1989b) Japanese noodle qualities: I. Flour components. Cereal Chem. 66, 387±391. Williams, P. C. (1973) The use of titanium dioxide as catalyst for large-scale Kjeldahl determination of total nitrogen content of cereal grains. J. Sci. Food Agric. 24, 343±348.
(Received 26 September 1997; accepted 27 June 1998)