Department of Agriculture Western Australia, South Perth, W.A. 6151 Australia
The Department of Agriculture Western Australia (DAWA) has had an interest in developing wheat for Asian markets that goes back to the early 1970s. In 1971, W.J. Toms visited S. E Asia and Japan and recognised good opportunities for specialty wheats in these markets. This visit gave impetus for a recently introduced hard wheat segregation and particularly provided incentive for the creation of a soft, biscuit-type wheat segregation in Western Australia. Toms’ report on this trip (Toms 1971) provided valuable technical information that assisted Australian research into wheat quality requirements of Asian foods.
While Western Australia had developed a reputation as a supplier of high quality wheat for the Japanese udon market, it became apparent during the 1980s that this was due to a single variety, Gamenya, and that new varieties of similar quality needed to be bred to maintain this reputation. DAWA recognised a need to develop expertise in noodle quality assessment, and this led to the introduction of a visiting experts program, involving visits by noodle technologists from Nisshin Flour Milling Co. Ltd in 1990 and 1996, and Nippon Flour Mills Co Ltd in 1991 and 1997. This program was arranged through the Japanese Flour Millers Association, which was keen for DAWA to be trained in the use of official Japanese methods as recommended and used by the Association’s Technical Committee. This program enabled DAWA to establish an expert sensory panel for the assessment of udon, so that advanced breeding lines could now be judged in line with the market requirement; it also provided reference methods, for the validation of small-scale prediction tests developed at DAWA.
Research in Japan and Australia during 1977-1980 pointed to importance of starch quality for noodles (Nagao et al. 1977, Shirao and Moss 1978, Oda et al. 1980 and Moss 1980). The research indicated that starch isolation was essential, and for udon, high starch paste peak viscosity, or low stability starch, was needed to achieve the desired texture.
Development of the FSV test
The information on the importance of starch quality was vital, but the test took too long and could only be applied to advanced breeding lines. The introduction of starch pasting tests at DAWA revealed in 1983 that Eradu, released a year earlier, had high starch paste peak viscosity, however Kulin which was about to be released and had been thought of as a potential udon variety was found to have low starch paste peak viscosity (Figure 1). Clearly what was needed was a rapid, small-scale test that was applicable to flour and wheatmeal and the screening of early generation breeding lines.
A breakthrough was the development of the flour swelling volume (FSV) test (Crosbie, 1989, 1991; Crosbie et al. 1992, 1993; Bettge 2003). The test requires less than 0.5 g of flour or wholemeal and can be carried out at a rate of about 100 samples per day. Studies have shown that FSV is highly correlated with boiled noodle yield and the textural components of boiled udon - softness, elasticity and smoothness (Crosbie, 1991; Crosbie et al. 1992; Crosbie and Lambe, 1993). Other features of the FSV test are its relative insensitivity to alpha-amylase (Crosbie and Lambe 1993) and its high heritability (Morris et al 1997). These were features that facilitated the use of the FSV test as a means of identifying and validating the null-4A molecular marker for starch quality developed by Briney et al (1998). The FSV test also proved vital in the development of new udon noodle wheat cultivars, including Cadoux (1992), Arrino (1997) and Calingiri (1997).
Figure 1. The combination of protein quality and starch quality sets varieties Gamenya and Eradu apart from others of historical significance and contributes to the excellence of these varieties for Japanese udon.
Effect of α-amylase on FSV and RVA tests
The relative insensitivity of the FSV test to alpha-amylase is due to the rapid heat inactivation of the enzyme in the test, favoured by a high temperature of the water bath, and thin tubes and initial constant mixing which allow for rapid heat exchange. Although insensitive to low levels of alpha-amylase, the FSV test requires inactivation of the enzyme with 0.5 mM AgNO3 if the wholemeal Falling Number level is below 200 sec. The inactivation treatment allows the inherent starch quality of badly sprouted wheat grain to be revealed (Crosbie and Lambe 1993). This and earlier research (e.g. Hutchinson 1966) pointed the direction towards the use of the Rapid Visco Analyser (RVA) to characterize starch quality of flour and wholemeal. The RVA is very sensitive to alpha-amylase, due to prolonged exposure of the test sample to temperatures favouring alpha-amylase activity; but the RVA can be used to characterise starch in flour and wholemeal if the alpha-amylase is inactivated with 1.0 mM AgNO3 (Crosbie et al 1999).
Starch quality requirements of ramen
FSV and RVA flour pasting characters, peak viscosity and breakdown, assessed with α-amylase inactivated, were found to be negatively correlated with the total texture score of ramen (Crosbie et al 1999). This confirmed earlier work of Shirao and Moss 1978, Miskelly and Moss 1985, Konik et al 1994, Ross et al 1996, and Ross et al 1997, that indicated a preference for high paste stability or low swelling starch in flour for this noodle type.
A key issue for a technical group visit to Japan in 1998 was to clarify the market requirement for noodle colour (Crosbie et al 1990). The group identified that the main market requirement was for udon with a bright, creamy colour; in relation to the creaminess, this meant that the flour should contain a moderate level of yellow pigment. The importance of colour meant that methods were required for the measurement of flour, noodle sheet and boiled noodle colour.
Studies by Crosbie and Chiu (1998) showed that the prediction of raw and boiled noodle colour from flour colour was influenced by particle size effects, but that these effects could be largely eliminated if the flour colour measurements were done on flour-water slurries, rather than dry flour.
A problem in noodle sheet colour measurement is that measurements can be affected by the background colour and variation in sheet thickness (Allen et al 1996; Solah et al 1997). Approaches suggested have included the use of a single noodle sheet on a standard white tile (Allen et al 1996) or vanilla tile (Crosbie et al 1996), or a multi-layer measurement at infinite optical thickness at which background and variation in sheet thickness do not affect the result (Solah et al 1997). In the latter case, infinite optical thickness was reached when measurements on white and black tiles were the same and this equated to 4 x 2.5 mm layers of udon noodle sheet and 5 x 1.4 mm layers of alkaline noodle sheet.
In the measurement of boiled noodle colour, a number of methods have been tried but the method preferred is as follows: after boiling, 60g of noodles are held in a covered plastic jar for 30 min, and then compressed with an Agtron sample cup (internal diameter, 60 mm at the top, 55 mm at the base) fitted with an optical glass base, through which measurements are taken with a Minolta CR310 colour meter.
Colour stability was a term coined in the early 1990s when we observed with our first visiting expert substantial variation in the degree of discoloration with time of raw noodle sheets prepared from different Australian wheat varieties. This was reported for both white salted (Crosbie et al., 1994) and yellow alkaline noodles (Crosbie and Lambe, 1995), and prompted further research and selection for this character in Australian wheat breeding programs.
Colour stability is largely related to polyphenol oxidase (PPO) activity, although other factors also contribute to discoloration. The level of PPO is simply screened for on le grains with rapid tests like the phenol test, and other phenolic substrates such as tyrosine and catechol also work well. More accurate tests for the measurement of PPO activity are available, such as that developed by Anderson and Morris (2001), involving the substrate L-dihydroxy-phenylalanine (L-DOPA).
Gloss and translucency
In recent collaborative studies involving BRI Ltd, Curtin University and DAWA into the effects of vacuum mixing on noodle quality, methods for the measurement of gloss and opacity were developed (Huang et al 2004). Opacity is measured with the use of a Leneta Opacity Chart which involves the measurement of brightness on both black and white backgrounds. Here opacity is calculated from the Y tristimulus value, by the formula:
Opacity (%) = 100*(Yblack/Ywhite).
Recent research includes a re-appraisal of quality objectives for soft wheat breeding in Western Australia. This has included the development of new tests, including a Japanese sponge cake test, which involved the training of food technologist N. Sy in Japan. The study has confirmed the importance of low flour protein and low water absorption for Japanese sponge cakes and sweet biscuits; yet to assess are the effects of protein and starch quality.
A collaborative GRDC-funded research project, which involved contributions from other organisations including BRI Ltd, Sydney University, NSW Agriculture, VIDA and SARDI , has resulted in the successful development of whole-grain calibrations for 5 traits - wheat protein, PSI, Buhler flour yield, CIE b*, and flour water absorption. A feature of the research was the extent to which the calibrations were validated, including confirming that the calibrations gave meaningful results over and above the effects of protein and grain hardness.
The calibrations are regularly being updated and are currently being applied at DAWA to screen early generation breeding lines at a rate of 220 samples per day. In 2004/2005, 15,000 samples were screened between harvesting and seeding. Much of the testing is undertaken as early as F3, which means that screening for quality can be carried out before yield testing. The introduction of the NIR tests has meant a substantial gain in efficiency in the wheat breeding program, because field and laboratory resources are now focused on material having a higher probability of success.
The research has highlighted the importance of proper validation of the new prediction tests, to ensure that the elimination of breeding lines is accompanied by an increased probability of success. NIR is but one of a suite of testing options becoming available to wheat breeders and it will be very important that the options be regularly reviewed, particularly in relation to the extent to which these have been validated for a wide range of genetic diversity.
I thank the Grains Research and Development Corporation for its support of much of the research reported here. I also wish to acknowledge co-researchers including W. Lambe, P. Chiu, Y. Wang and N. Sy of DAWA; A. Ross, formerly of BRI Australia Ltd and Curtin University and now of Oregon State University; K. Quail, S. Huang, B. Osborne and I. Wesley of BRI Australia Ltd; V. Solah and A. Limley of Curtin University; and laboratory staff at DAWA, including P. Freeland, P. Marrett and V. Martinek, for their excellent support.
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