Introduction

Canada has recognized the importance of the Asian marketplace, which has represented greater than 50% of our exports for the last two decades. Depending on the literature source cited, most Asian countries utilize 30-40% of their wheat for the production of noodles. Canadian hard wheats are ideally suited for the production of the dominant noodle type, yellow alkaline noodles, which require elevated protein levels to impart their desired textural attributes.

While Canadian plant breeders have excellent and diverse germplasm to work with, within the last year a concerted effort has been undertaken to assist the assessment of new lines for the Asian market. Three organizations; Agriculture and Agri-Foods Canada (AAFC), the Canadian Grain Commission (CGC) and the Canadian International Grains Institute (CIGI) have adopted a standardized evaluation of breeder lines at all stages of the screening process. The system has adopted a protocol which focuses on the evaluation of new lines of Canada Western Red Spring (CWRS), Canada Western Hard White Spring (CWHWS) and Canada Prairie Spring White (CPSW) wheat for alkaline noodles and bread products. The new protocol encompasses the use of 1% w/w alkali (9:1 sodium:potassium carbonates), 1% w/w NaCl and an absorption level of 34%. Furthermore, the preparation of the noodle crumb has been standardized with the use of an asymmetrical centrifugal mixer. This mixer offers a number of advantages to the plant breeders. One key advantage is the smaller amount of sample required, 50 g, instead of the traditional 200g employed using traditional mixers. An additional benefit is that the mixing time has been significantly reduced, only 30 sec at 3,000 rpm, offering a major time saving over the traditional 5.5 min. Other advantages of this mixer are the small and relatively constant (3mm) dough particles combined with the excellent and uniform hydration of the dough crumb. Subsequent dough sheets exhibit minimal streaking due to non-uniform water distribution. Previous research within our laboratory (Hatcher and Preston, 2004) had demonstrated that the use of the dual pin bowl offered both the same colour and textural attributes as the traditional mixer for both CWRS and CPSW wheat.

Standardising noodle appearance assessment

One of the key issues in achieving a uniform national standardized system for assessing noodle appearance has been addressed within our laboratories using image analysis. A series of papers (Hatcher et al 1999, Hatcher et al 2004) had demonstrated the ability of a CCD camera to offer an objective assessment of noodle appearance aside from L*,a* and b*. Continued advancement within our laboratory has led to the development of an inexpensive scanner based system run off of a laptop computer. The unique feature of this unit is its ability to self correct its image colour components from the scanner to the internationally recognized Kodak Q-60 colour standard prior to providing its unique noodle appearance characterization. (Figure.1) Introduction, image capture, storage and subsequent analysis of the noodle dough image occurs within 30-45 sec depending on the parameters selected by the analyst. The new software offers the analyst the ability to set the parameters for the minimum size of speck that will be detected (3000 um²) and the minimum delta value (2 of 255 units) between the overall background colour of the noodle matrix and a speck itself. Additional features allow the operator to assess the noodle dough sheet at any combination of these parameters such that a grid of values can be easily established in one single analysis pass.

Figure1. Self colour correction using the Kodak Q-60 prior to carrying out in-depth analysis of noodle sheet appearance.

In an effort to improve the efficiency of the scanner based system, artificial neural net based algorithms have been developed which allow L*, a* and b* values to be determined on the 5 x 5 cm dough sheet. These algorithms are based on over 1400 measurements using noodle dough sheets derived from different classes of Canadian wheat flour. Current coefficients of determination (r²) ranged from 0.82-0.97 and due to the nature of neural algorithms are improving with each additional dataset added.

selecting for desired noodle colour attributes

The Colour of alkaline noodles is affected by a variety of biochemical components of which enzymes, polyphenol oxidase and peroxidase are dominant. A rapid (1 min) microplate based assay for peroxidase was developed based on the commercially available substrate ABTS (Hatcher and Barker 2005). The assay is ideally suited for plant breeders as it can be carried out on only 0.5 g of ground grain or flour which is extracted in 5 ml of acetate buffer (pH 4.6 at 4°C) for 30 min. Individual kernels from a single plant can also be analysed following the same procedure adjusting the extracting volume to 1.0 ml. Multiple extracts of wheat and flour carried out over 5 and 3 days respectively displayed an average coefficient of variation of less than 5%. Analyses of individual kernels from different varieties demonstrated significant genotypic influence on peroxidase levels. Examination of varieties over a two year period, grown during western Canadian plant breeding trials, demonstrated significant genotype, environment and genotype x environment interaction influences on peroxidase levels. While the assay was developed to assist plant breeders, it is well adapted for the analysis of individual millstreams allowing millers to select streams to generate high value flours for discoloration sensitive products such as noodles and steam breads (Figure. 2).

Figure 2. Peroxidase activity distribution within CWRS millstreams and corresponding cumulative activity.

Recognizing that plant breeders have limited sample material to evaluate lines, a non-destructive predictive model for the estimation of alkaline raw noodle colour components L*,a *, and b* was developed based upon CWRS, CWHWS and CPSW straight grade flours. The predictive model is based upon NIR spectral data (Perten Model 6500) ranging from 400-2498 nm. The predictive models were developed using 150 flours and yielded minimum r²= 0.85, 0.93 and 0.63 when predicting the L* ,a* and b* respectively for noodles at both 2 and 24 hrs.

Flavonoid compounds found in wheat flour are normally colourless at neutral pH but in the presence of alkali undergo a chromophoric shift to impart the desired yellow colour to alkaline noodles. The current research was undertaken to quantify and determine if there existed differences in flavonoid levels in Canadian wheats. The simple flavonoid extraction procedure, employing 0.1M hydroxyl amine, developed by Wang (1998) was refined by using increased hydroxyl amine (10%w/v) to improve the extraction technique. The result of the extraction of multiple samples using both extracting solutions revealed that the 10%w/v solution consistently yielded higher flavonoid levels based upon narinigin equivalents. Employing CWRS, CWHWS and CPSW wheat variety flours, grown at the same sites in 2003 and 2004, indicated significant varietal and environmental effects. In both years the CWRS variety Neepawa yielded the highest flavonoid levels followed by the CWHWS variety Snowbird. The lowest flavonoid levels were found with the CPSW variety AC Vista. Additional examination of millstreams of individual CWRS varieties Majestic and Katepwa as well as a CWRS export composite sample of many varieties indicated significant differences in the distribution patterns due to their behaviour on the mill (Figure. 3).

Figure 3. Flavonoid distribution (narinigin equivalents) in millstreams of CWRS varieties

Recognizing that flavonoid levels are an important aspect of noodle colour an attempt was made to predict hydroxylamine extracted flavonoid flour content based upon NIR (Model 6500) spectra of CWRS, CPSW and CWHWS straight grade flours. The preliminary results of this work suggest that NIR analysis of the spectra may serve plant breeders as a useful screening tool. A calibration r² of 0.72 was developed on the basis of 150 samples which achieved an r² = 0.63 using 50 additional samples. Further data collection is ongoing to improve the predictive capability of this model.

Market development

Canada has recognized the importance of developing hard white cultivars for the Asian markets and the intrinsic benefits they invoke in the manufacture of Oriental noodles. Working in collaboration with AAFC staff a three year genotype by environment series of experiments were undertaken to compare new hard white wheat lines with traditional CWRS varieties. As anticipated significant variety, environment and variety x environment influences were detected in both the colour and texture characteristics of the alkaline noodles. The study consisted of two CWRS varieties; AC Barrie, the dominant variety in western Canada on the basis of cultivation and AC Domain which was used in the development of the new hard white wheat. Three new hard white wheats; Snowbird, Kanata and BW275 were also grown at the same sites (3). While individual sites and years exhibited varying degrees of variation, all three new hard white lines exhibited excellent noodle characteristics. The white wheat noodles all displayed significantly better brightness at both 2 and 24 hrs than the current dominant CWRS variety Barrie. Significant benefits for all of the white wheats were also observed at both time periods in terms of redness, a*, over Barrie. The yellowness, b*, of Snowbird was equivalent to that of the CWRS varieties at 2 hrs and was significantly better than all varieties when aged for 24 hrs.

While noodle colour is important to the consumers’ perception, appearance is critical for its acceptability. Image analysis of the yellow alkaline noodle speckiness at both 2 and 24 hrs highlighted the significant advantages the new hard white lines have over traditional CWRS varieties. The CWRS variety Barrie consistently displayed a significantly greater number of specks /25 cm² than all other varieties when measured at 1, 2 or 24 hrs after production. Domain, while displaying significantly fewer specks than Barrie also exhibited significantly greater number of specks at each time interval. While no differences were observed within the three white lines at either 1 or 2 hrs, aging for 24 hrs resulted in Snowbird showing significantly fewer specks than either of the other two white lines.

Examination of the cooked noodle texture attributes revealed that both Snowbird and BW275 displayed better bite characteristics, as determined by maximum cutting stress, MCS, (Oh et al 1983) than either of the two CWRS varieties. The white variety Kanata displayed significantly lower average MCS values than the CWRS varieties. Analysis of noodle chewiness via recovery, REC, measurements (Oh et al 1983) indicated that all three white varieties exhibited significantly better values than the dominant CWRS variety, Barrie. Examination of resistance to compression, RTC, (Oh et al 1983) data however revealed that while Kanata and BW275 were equivalent to the CWRS varieties, Snowbird exhibited significantly lower values than all other cultivars. This was the only texture attribute in which Snowbird did not match or exceed the CWRS varieties.

The influence of alkaline carbonate ratios, concentration (1 vs 5 %) and the presence (3%) or absence of salt in the formula on noodle texture attributes has also been investigated. Utilizing straight grade CWRS and CPSW flours a series of experiments indicated that the presence of salt in any formula at the 3% level significantly increased the amount of work required to make noodles. The ratio of sodium:potassium carbonate, 1:9 vs 9:1 at the 1% w/w level, while influencing noodle thickness, did not have any significant impact on MCS, RTC or REC. However, in all cases the presence of 3% NaCl resulted in significantly lower and poorer texture attributes. In general the use of either carbonate ratio at the 5% w/w level resulted in significantly poorer cooked noodle texture than observed at the 1% level. While no significant differences had been observed due to carbonate ratio at the 1% level, at the 5% w/w concentration the 1:9 Na:K carbonate formulas consistently displayed significantly lower texture attributes than the corresponding 9:1 formula.

Further research

Research has been undertaken to investigate the impact of particle size (PS), starch damage (SD) and alkali reagent (1% w/w 1:9 Na:K carbonate versus 1% w/w NaOH) using flours derived from the same CPSW wheat. The alkali reagent significantly influenced cooking loss, with greater loss occurring in noodles prepared using NaOH than carbonate. No influence was observed on the basis of particle size or starch damage, however, water uptake during cooking, exhibited the inverse, as it was not influenced by the alkali reagent but significantly effected by both PS and SD. The resulting cooked noodles’ thickness were found to be significantly influenced by all three parameters. All cooked noodles prepared with NaOH displayed lower texture attributes than those prepared using Na:K carbonate for MCS, RTC and chewiness (with SD and PS influencing these attributes variably.

Canada is subject to varying degrees of frost damage to its wheat crop on a sporadic but consistent basis. Research has been carried out to understand its impact on the quality of alkaline noodles prepared from CWRS. Raw noodle colour was adversely effected when flour from No.3 and Feed grade wheat (downgraded solely on the basis of frost) were used to prepare noodles. Visual inspection and subsequent division of No.3 wheat on the basis of frost damage, prior to milling, offered the ability to discern differences within this grade due to frost damage on noodle texture. Only the most severely damaged No.3 graded CWRS or the Feed grade derived flours exhibited a significant impact on MCS, RTC and REC.

Conclusion

Canada has recognized the importance of the Asian export market and continues to focus its research on this area. At present the breeding program for this marketplace is focused on the further development of hard white wheat while maintaining the benefits inherent in the CWRS class. Areas which have been identified of importance are; wheat seed coat colour stability, flavonoid levels, the composition and profile of phenolics which influence taste and the establishment of effective quality parameters for the Asian marketplace.

References

Hatcher, D.W., Symons, S.J. and Kruger, J.E. 1999. Measurement of the time dependent appearance of discoloured spots in alkaline noodles by image analysis. Cereal Chem. 76:189-194.

Hatcher, D.W. and Preston, K.R. 2004. Investigation of a small-scale asymmetric centrifugal mixer for the evaluation of Asian noodles. Cereal Chem. 81:303-307.

Hatcher, D.W., Symons, S.J. and Manivannan, U. 2004. Developments in the use of image analysis for the assessment of oriental noodle appearance and colour. J. Food Eng. 6l:109-117.

Hatcher, D.W. and Barker, W. 2005. A rapid microsassy for determination of peroxidase in wheat and flour. Cereal Chem. 82:233-237.

Oh,N.H., Seib, P.A., Deyoe, C.W. and Ward, A.B. 1983. Noodles.I. Measuring the textural characteristics of cooked noodles. Cereal Chem. 60:433-438.

Wang, Y.M. 1998. Characterisation of grain constituents responsible for the yellow colour of Asian alkaline noodles. Ph.D. Thesis. University of Sydney.