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The relationship between starch swelling properties, paste viscosity and boiled noodle quality in wheat flours
Journal o/Cereal Science 13 (1991) 145-150
The Relationship Between Starch Swelling Properties, Paste Viscosity and Boiled Noodle Quality in Wheat Flours G. B. CROSBIE
Western Australian Department of Agriculture, Baron-Hay Court, South Perth, W.A. 6151, Australia Received 20 March 1990
Selection of wheat breeding lines with improved quality for white, Japanese-style noodles is frequently deferred in Australian wheat breeding programmes until final stages of testing, due to the lack of suitable small-scale tests. In this study, the starch swelling power test was investigated, particularly for its suitability as a small-scale test for predicting noodle eating quality. In addition, two new tests based on the swelling volume of starch and flour are reported. For samples from 13 cultivars at two sites, starch swelling power and starch swelling volume were significantly (P < 0'01) correlated with starch paste peak viscosity (r = 0'80, and r = 0'81, respectively). This suggests that these tests may provide similar information on the starch characteristics of these cuitivars. For starch separated from 13 flours that had previously been evaluated in Japan for noodle eating quality, starch swelling power and starch swelling volume were significantly (P < 0'01) correlated with total texture score of the boiled noodles (r = 0'84, and r = 0'88, respectively). Flour swelling volume was not as highly correlated as starch swelling volume with individual components of the texture of the boiled noodles, but nevertheless variation in flour swelling volume accounted for 48 % of the variation in total texture score.
Introduction About 16 % of flour consumed in Japan is currently used for the production of various forms of the white Japanese noodle and a similar proportion is used for yellow Chinese noodles!. The production of white noodles from a combination offtour, salt and water, is not restricted to Japan. A white noodle is made in Korea, with textural requirements 2 similar to those described for the Japanese noodle 3 • The white noodle is also a major type consumed in The People's Republic of China, although the preferred textural characteristics appear to be different from those for the Japanese noodle 4 • Australian Standard White (ASW) wheat from Western Australia is highly regarded in Japan for its suitability for the production of Japanese noodles. Several studies 3 ,6-7 have indicated that this reputation can be largely attributed to the quality of the starch component of this wheat and its effect on the eating quality or textural characteristics of the boiled noodle. The high quality of this wheat has been associated with two softAbbreviations used: ASW
= Australian Standard White (wheat);
0733-5210/91/020145 +06 $03.00/0
AWB
= Australian Wheat Board. © 1991 Academic Press Limited CER 13
146
G. B. CROSBIE
grained cultivars, Gamenya and Eradu, which are characterized by several common quality traits, but particularly high starch paste peak viscosity as determined on a Brabender Viscograph 8 • Apart from the end-product test, the measurement of starch parte peak viscosity has become the most widely accepted means of selecting for improved quality for Japanese noodles in Australian wheat breeding programmes. However, its application has generally been restricted to later stages of testing, due to the relatively large sample size (34 g, d.b.) and long analysis time (1 h) required. The work of Oda et al,3 and Moss 6 suggests that selection for low amylose content in early generations may prove fruitful but this strategy has not been widely adopted. This may be due, in part, to the difficulty in measuring amylose content accurately9, but some unpublished results in this laboratory have indicated only small differences in amylose content between cultivars differing appreciably in starch paste peak viscosity and eating quality. Clearly there is a need for a more discriminating method which can be used for selecting early generation breeding lines for noodle quality. One test which appears to offer some potential is the measurement of starch swelling power 10 . Starch swelling power is the weight of sedimented starch gel, relative to its dry weight, obtained after gelatinizing a sample of starch in water, at a given temperature for a specified time, and followed by centrifugation. The starch swelling power test has previously been used largely to demonstrate differences between various types of starch, such as potato, sorghum, tapioca, wheat, waxy maize and normal maize 10-12 , and to examine the effects of starch modifiers 13 . However, Endo et al,u reported a difference in swelling power between starches separated from Western Australian ASW and a Japanese wheat cultivar. Recently, Toyokawa et al.? demonstrated a difference between starches from various wheat classes, including Western Australian ASW, in water holding capacity at 75 cC, a measurement closely related to swelling power (water holding capacity was reported as grams of water held per gram of dry sample, under the conditions applied in the test). Also, Crosbie1 5 reported the application of the swelling power test as a relatively simple means of characterizing the starch qualities of different wheat cultivars. He pointed out that the desirably high visco-elasticity of boiled Japanese-style noodles made from flour of the cultivars Gamenya and Eradu may be closely related to the high swelling power of their starch. He also suggested the possible development of a rapid test based on the measurement of starch swelling volume which may have application in wheat breeding programmes concerned with the development of improved quality wheats for noodle manufacture. This paper outlines studies carried out to develop the starch swelling volume test and reports on the application of the test to flour. Further assessment of the swelling power test was also undertaken.
Experimental Source of grain and flour Two sets of wheat samples were analysed. Set I consisted of 13 soft-grained cultivars that were of historical significance to wheat production in Western Australia. Grain samples were obtained from trials conducted at Wongan Hills in 1987 and Merredin in 1988. Each sample was a composite of three replicates. These samples were milled to 60 % extraction according to the method of the Japan Wheat Research Association 16 •
STARCH SWELLING AND NOODLE QUALITY
147
The second set (set 2) were six flours provided by the Australian Wheat Board (AWB) and seven blends of these flours, representing a range of current cultivars of varying quality for the production of white Japanese noodles. The samples had earlier been milled on a pilot-scale mill at the Bread Research Institute of Australia to extraction levels of generally 50 %, but in one case to 60 %. The flours were forwarded by the AWB to Japan in 1988 and evaluated by the Technical Committee of the Flour Millers Association for noodle (udon) quality. This assessment included scores for three textural components of the cooked noodles - softness (maximum 10 points), elasticity (maximum 25 points), and smoothness (maximum 10 points). The flours were also analysed by standard methods 17 for protein and moisture content.
Isolation and assessment of starch Starch was isolated from both sets of flour by the method of Oda et at. a, air-dried to about 10% moisture, coarsely reduced in size with a mortar and pestle, and ground in a Retsch Ultra Centrifugal Mill, Type ZMI, fitted with a 1 mm screen. The moisture content of each starch was determined by drying 1 g at 130°C for 1 h. Re~suspension of samples of these starches, followed by centrifugation, showed no signs of a 'sludge' as described by Medcalf and GilIes 18 • Assessments of starch paste peak viscosity were carried out on a Brabender Visco graph (250 cmg sensitivity cartridge) according to the method described by Oda et af.3, but using 32-4 g (dry basis) starch and 450 ml of distilled waterlOo Swelling power was assessed on a sample of starch (1'0 ± 0·001 g, dry basis) by a method similar to that described by Leach et al. tO • The sample was weighed into a 50 ml Nalgene polycarbonate centrifuge tube to which distilled water (30 ml) was added using a rapid dispensing pipette. The screw cap was quickly applied and the contents of the tube mixed on a vortex mixer; any delay at this stage caused the starch to form lumps. The tube was then placed in a constant temperature water bath at 92·5 ± 0-5 °C and mixed by inverting twice at regular intervals (20 s intervals initially for about the first 3 min until the contents were fully gelatinized, then at 30 s intervals for 2 min, then every 1 min for 5 min, and then every 5 min) for a total time of 30 min. The tube was cooled rapidly in iced water to approximately 25 °e, inverted twice, placed in a 25°C water bath for 5 min and then centrifuged at 1000 g for 20 min. The supernatant was carefully removed by suction, evaporated and dried at 105°C for 5 h. Swelling power was calculated as the weight of sedimented gel, divided by the original dry weight of starch less soluble dry matter. Swelling volume was determined 011 samples of starch (0'35±0'001 g, dry basis) and flour (0'45 ± 0-001 g, dry basis). The samples were weighed into 125 x 16 mm screw-capped culture tubes and distilled water (12'5 ml) added with a rapid dispensing pipette. The caps of the tubes were fitted with non-standard rubber inserts, to eliminate any loss of contents during the test. The method that followed was similar to that for the swelling power test, although the samples were mixed more frequently during the first 2 min of heating. This was because the temperature rose more rapidly and gelatinization occurred more quickly in the narrower bore culture tubes. The tubes were inverted twice every 15 s for 2 min, then every 1 min for 3 min, and then every 5 min for 25 min, for a total time of 30 min. The test was completed after centrifuging at 1000 g for 10 min. The swelling volume of the resultant sedimented gel was calculated from its height (to the nearest mm) in the constant bore tube. All starch and flour tests were carried out at least in duplicate.
Statistical analyses Data from the testing of samples from set 1 were subjected to simple correlation analysis to determine associations between starch paste peak viscosity and the small-scale starch swelling tests. Simple correlation analysis was also applied to the results of tests on the samples from set 2, to test associations between starch and flour measurements and noodle texture scores assessed subjectively by the Technical Committee of the Flour Millers Association of Japan. 6-2
148
G. B. CROSBIE
TABLE 1. Ranges of starch paste peak viscosity, starch swelling power and starch swelling volume values of samples from 13 wheat cultivars grown at two sites (set 1) Wongan Hills, 1987
Merredin, 1988
Range
Range
440-1115 17·0-21·9 7,3-9,2
390-930 14'9-20,6 6'6-8·8
Test Starch peak viscosity (AU)" Starch swelling power (gig) Starch swelling volume (ml) " Brabender Amylograph Units.
TABLE II. Simple correlation coefficients between starch paste viscosity and swelling tests. Based on data from 13 cultivars at two locations - Wongan Hills (1987) and Merredin (1988) Correlation with starch paste peak viscosity
Starch swelling power Starch swelling volume
**p
Wongan Hills
Merredin
Overall
0'88** 0,8.4**
0'82** 0,82**
0,80** 0'81**
< 0'01.
TABLE III. Simple correlation coefficients between starch and flour properties and components of noodle eating quality (set 2, 13 samples) Noodle eating quality parameters
Starch peak viscosity Starch swelling power Starch swelling volume Flour swelling volume
Softness
Elasticity
Smoothness
Total score
0,77** 0.70** 0,85** 0,55*
0,69** 0,79** 0,79** 0,68**
0·34 0'49 0'49 0'36
0,77** 0'84** 0,88** 0,69**
* p < 0'05; ** p < 0·01. Results
The range of values of the various tests carried out on samples from the 13 wheat cultivars at two sites (set 1) are presented in Table I. The swelling power values are higher than those previously reported1S, and probably resulted from a more thorough mixing of the samples before and during heating in the water bath. For set 1, starch paste peak viscosity was highly correlated with starch swelling power and starch swelling volume at each of the two locations and with the data combined (Table II). For set 2, starch and flour measurements were correlated to varying degrees with total texture scores and two ofits components, softness and elasticity (Table III). None of the tests were correlated with the smoothness of the boiled noodles, however the samples
STARCH SWELLING AND NOODLE QUALITY
149
tested had only a narrow range of smoothness values (samples were classified into one of three smoothness groups having values of 6, 6·5 and 7). In this set of samples, starch paste peak viscosity was correlated (P < 0'01) with starch swelling power (r = 0'72) and starch swelling volume (r = 0'90). The protein contents of the flour samples in this set ranged from 8·7 to 11'5 %, on a dry basis. Discussion
Associations between tests
The high correlation coefficients obtained from set 1 indicate that starch swelling power and starch swelling volume may be useful alternatives to starch paste peak viscosity in characterizing the quality of starch isolated from flour of different wheat cultivars. The correlations determined between the results of the various starch and flour tests and the assessments of softness, elasticity and total texture score of the boiled noodles (Table III) support previous studies 3 , 5-7 which have highlighted the importance of starch properties in relation to noodle eating quality. Potential application of the tests
The results indicate that starch swelling power provides an alternative measurement to starch paste peak viscosity for predicting noodle eating quality. The test offers advantages over conventional paste viscosity measurements in terms of analysis time and sample size. Starch swelling volume also gave high correlations with starch paste peak viscosity and important aspects of the texture of boiled noodles. The test can be carried out on a 0·35 g sample and should allow a substantial increase in sample throughput compared with the swelling power test. The measurement of flour swelling volume gave promising results, although not as highly correlated with noodle eating quality as starch swelling volume. Nevertheless, variation in flour swelling volume accounted for 48 % of the variation in total texture score. The interface between supernatant and gel was less clearly defined in the case of the flour swelling volume test, but the problem was minimized when samples were viewed with an adequate background light. The flour samples used in this study were of low extraction and further work is needed to assess the importance of milling method and extraction level in relation to the prediction of noodle eating quality by this test. The author thanks the Australian Wheat Board and the Technical Committee of the Flour Millers Association of Japan for providing flour samples and noodle assessments; also W. K. Anderson and R. F. Gilmour for their helpful suggestions in the preparation of this manuscript. The technical assistance of W. J. Lambe and G. Coupar is gratefully acknowledged. References 1. Nagao, S. in •Proc, 39th Annual Conference, Royal Australian Chemical Institute Cereal Chemistry
Division', RAC.!., Parkville, Australia (1989) pp 54-58. 2. Lee, C-H., Gore, P. J., Lee, H-D., Yoo, B-S. and Hong, S-H. J. Cereal Sci. 6 (1987) 283-297.
150
G. B. CROSBIE
3. Oda, M., Yasuda, Y., Okazaki, S., Yamauchi, Y. and Yokoyama, Y. Cereal Chern 57 (1980) 253-254. 4. Huang, S. and Morrison, W. R. J. Cereal Sci. 8 (1988) 177-187. 5. Nagao, S., Ishibashi, S., Imai, S., Sato, T., Kanbe, T., Kaneko, Y. and Otsubo, H. Cereal Chern. 54 (1977) 198-204. 6. Moss, H. J. Cereal Res. Cornrnun. 8 (1980) 297-302. 7. Toyokawa, H., Rubenthaler, G. L., Powers, J. R. and Schanus, E. G. Cereal Chern. 66 (1989) 387-391. 8. Crosbie, G. B. Cereal Foods World 34 (1989) 678---681. 9. Morrison, W. R. and Laignelet, B. J. Cereal Sci. 1 (1983) 9-20. 10. Leach, H. W., McCowen, L. D. and Schoch, T. J. Cereal Chern. 36 (1959) 534-544. 11. Elder, A. L. and Schoch, T. J. Cereal Sci. Today 4 (1959) 202-208. 12. Doublier, J. L. J. Cereal Sci. 5 (1987) 247-262. 13. Kim, H. O. and Hill, R. D. Cereal Chern. 61 (1984) 432-435. 14. Endo, S., Karibe, S., Okada, K. and Nagao, S. Nippon Shokuhin Kogyo Gakkaishi 35 (1988) 7-14. 15. Crosbie, G. B. in 'Proc. 39th Annual Conference, Royal Australian Chemical Institute Cereal Chemistry Division', R.A.C.I., Parkville, Australia (1989) pp 59---65. 16. Japan Wheat Research Association. 'Tables for the Quality Survey of Imported Wheat Cargoes, 1988 F.Y. " J.W.R.A., Tokyo, Japan (1989). 17. American Association of Cereal Chemists. 'Cereal Laboratory Methods', AACC, St Paul, MN (1978). 18. Medcalf, D. G. and Gilles, K. A. Cereal Chern. 42 (1965) 558-568. 19. Moss, H. J. and Miskelly, D. M. Food Tech. Ausl. 36 (1984) 90-91.
The Relationship Between Starch Swelling Properties, Paste Viscosity and Boiled Noodle Quality in Wheat Flours G. B. CROSBIE
Western Australian Department of Agriculture, Baron-Hay Court, South Perth, W.A. 6151, Australia Received 20 March 1990
Selection of wheat breeding lines with improved quality for white, Japanese-style noodles is frequently deferred in Australian wheat breeding programmes until final stages of testing, due to the lack of suitable small-scale tests. In this study, the starch swelling power test was investigated, particularly for its suitability as a small-scale test for predicting noodle eating quality. In addition, two new tests based on the swelling volume of starch and flour are reported. For samples from 13 cultivars at two sites, starch swelling power and starch swelling volume were significantly (P < 0'01) correlated with starch paste peak viscosity (r = 0'80, and r = 0'81, respectively). This suggests that these tests may provide similar information on the starch characteristics of these cuitivars. For starch separated from 13 flours that had previously been evaluated in Japan for noodle eating quality, starch swelling power and starch swelling volume were significantly (P < 0'01) correlated with total texture score of the boiled noodles (r = 0'84, and r = 0'88, respectively). Flour swelling volume was not as highly correlated as starch swelling volume with individual components of the texture of the boiled noodles, but nevertheless variation in flour swelling volume accounted for 48 % of the variation in total texture score.
Introduction About 16 % of flour consumed in Japan is currently used for the production of various forms of the white Japanese noodle and a similar proportion is used for yellow Chinese noodles!. The production of white noodles from a combination offtour, salt and water, is not restricted to Japan. A white noodle is made in Korea, with textural requirements 2 similar to those described for the Japanese noodle 3 • The white noodle is also a major type consumed in The People's Republic of China, although the preferred textural characteristics appear to be different from those for the Japanese noodle 4 • Australian Standard White (ASW) wheat from Western Australia is highly regarded in Japan for its suitability for the production of Japanese noodles. Several studies 3 ,6-7 have indicated that this reputation can be largely attributed to the quality of the starch component of this wheat and its effect on the eating quality or textural characteristics of the boiled noodle. The high quality of this wheat has been associated with two softAbbreviations used: ASW
= Australian Standard White (wheat);
0733-5210/91/020145 +06 $03.00/0
AWB
= Australian Wheat Board. © 1991 Academic Press Limited CER 13
146
G. B. CROSBIE
grained cultivars, Gamenya and Eradu, which are characterized by several common quality traits, but particularly high starch paste peak viscosity as determined on a Brabender Viscograph 8 • Apart from the end-product test, the measurement of starch parte peak viscosity has become the most widely accepted means of selecting for improved quality for Japanese noodles in Australian wheat breeding programmes. However, its application has generally been restricted to later stages of testing, due to the relatively large sample size (34 g, d.b.) and long analysis time (1 h) required. The work of Oda et al,3 and Moss 6 suggests that selection for low amylose content in early generations may prove fruitful but this strategy has not been widely adopted. This may be due, in part, to the difficulty in measuring amylose content accurately9, but some unpublished results in this laboratory have indicated only small differences in amylose content between cultivars differing appreciably in starch paste peak viscosity and eating quality. Clearly there is a need for a more discriminating method which can be used for selecting early generation breeding lines for noodle quality. One test which appears to offer some potential is the measurement of starch swelling power 10 . Starch swelling power is the weight of sedimented starch gel, relative to its dry weight, obtained after gelatinizing a sample of starch in water, at a given temperature for a specified time, and followed by centrifugation. The starch swelling power test has previously been used largely to demonstrate differences between various types of starch, such as potato, sorghum, tapioca, wheat, waxy maize and normal maize 10-12 , and to examine the effects of starch modifiers 13 . However, Endo et al,u reported a difference in swelling power between starches separated from Western Australian ASW and a Japanese wheat cultivar. Recently, Toyokawa et al.? demonstrated a difference between starches from various wheat classes, including Western Australian ASW, in water holding capacity at 75 cC, a measurement closely related to swelling power (water holding capacity was reported as grams of water held per gram of dry sample, under the conditions applied in the test). Also, Crosbie1 5 reported the application of the swelling power test as a relatively simple means of characterizing the starch qualities of different wheat cultivars. He pointed out that the desirably high visco-elasticity of boiled Japanese-style noodles made from flour of the cultivars Gamenya and Eradu may be closely related to the high swelling power of their starch. He also suggested the possible development of a rapid test based on the measurement of starch swelling volume which may have application in wheat breeding programmes concerned with the development of improved quality wheats for noodle manufacture. This paper outlines studies carried out to develop the starch swelling volume test and reports on the application of the test to flour. Further assessment of the swelling power test was also undertaken.
Experimental Source of grain and flour Two sets of wheat samples were analysed. Set I consisted of 13 soft-grained cultivars that were of historical significance to wheat production in Western Australia. Grain samples were obtained from trials conducted at Wongan Hills in 1987 and Merredin in 1988. Each sample was a composite of three replicates. These samples were milled to 60 % extraction according to the method of the Japan Wheat Research Association 16 •
STARCH SWELLING AND NOODLE QUALITY
147
The second set (set 2) were six flours provided by the Australian Wheat Board (AWB) and seven blends of these flours, representing a range of current cultivars of varying quality for the production of white Japanese noodles. The samples had earlier been milled on a pilot-scale mill at the Bread Research Institute of Australia to extraction levels of generally 50 %, but in one case to 60 %. The flours were forwarded by the AWB to Japan in 1988 and evaluated by the Technical Committee of the Flour Millers Association for noodle (udon) quality. This assessment included scores for three textural components of the cooked noodles - softness (maximum 10 points), elasticity (maximum 25 points), and smoothness (maximum 10 points). The flours were also analysed by standard methods 17 for protein and moisture content.
Isolation and assessment of starch Starch was isolated from both sets of flour by the method of Oda et at. a, air-dried to about 10% moisture, coarsely reduced in size with a mortar and pestle, and ground in a Retsch Ultra Centrifugal Mill, Type ZMI, fitted with a 1 mm screen. The moisture content of each starch was determined by drying 1 g at 130°C for 1 h. Re~suspension of samples of these starches, followed by centrifugation, showed no signs of a 'sludge' as described by Medcalf and GilIes 18 • Assessments of starch paste peak viscosity were carried out on a Brabender Visco graph (250 cmg sensitivity cartridge) according to the method described by Oda et af.3, but using 32-4 g (dry basis) starch and 450 ml of distilled waterlOo Swelling power was assessed on a sample of starch (1'0 ± 0·001 g, dry basis) by a method similar to that described by Leach et al. tO • The sample was weighed into a 50 ml Nalgene polycarbonate centrifuge tube to which distilled water (30 ml) was added using a rapid dispensing pipette. The screw cap was quickly applied and the contents of the tube mixed on a vortex mixer; any delay at this stage caused the starch to form lumps. The tube was then placed in a constant temperature water bath at 92·5 ± 0-5 °C and mixed by inverting twice at regular intervals (20 s intervals initially for about the first 3 min until the contents were fully gelatinized, then at 30 s intervals for 2 min, then every 1 min for 5 min, and then every 5 min) for a total time of 30 min. The tube was cooled rapidly in iced water to approximately 25 °e, inverted twice, placed in a 25°C water bath for 5 min and then centrifuged at 1000 g for 20 min. The supernatant was carefully removed by suction, evaporated and dried at 105°C for 5 h. Swelling power was calculated as the weight of sedimented gel, divided by the original dry weight of starch less soluble dry matter. Swelling volume was determined 011 samples of starch (0'35±0'001 g, dry basis) and flour (0'45 ± 0-001 g, dry basis). The samples were weighed into 125 x 16 mm screw-capped culture tubes and distilled water (12'5 ml) added with a rapid dispensing pipette. The caps of the tubes were fitted with non-standard rubber inserts, to eliminate any loss of contents during the test. The method that followed was similar to that for the swelling power test, although the samples were mixed more frequently during the first 2 min of heating. This was because the temperature rose more rapidly and gelatinization occurred more quickly in the narrower bore culture tubes. The tubes were inverted twice every 15 s for 2 min, then every 1 min for 3 min, and then every 5 min for 25 min, for a total time of 30 min. The test was completed after centrifuging at 1000 g for 10 min. The swelling volume of the resultant sedimented gel was calculated from its height (to the nearest mm) in the constant bore tube. All starch and flour tests were carried out at least in duplicate.
Statistical analyses Data from the testing of samples from set 1 were subjected to simple correlation analysis to determine associations between starch paste peak viscosity and the small-scale starch swelling tests. Simple correlation analysis was also applied to the results of tests on the samples from set 2, to test associations between starch and flour measurements and noodle texture scores assessed subjectively by the Technical Committee of the Flour Millers Association of Japan. 6-2
148
G. B. CROSBIE
TABLE 1. Ranges of starch paste peak viscosity, starch swelling power and starch swelling volume values of samples from 13 wheat cultivars grown at two sites (set 1) Wongan Hills, 1987
Merredin, 1988
Range
Range
440-1115 17·0-21·9 7,3-9,2
390-930 14'9-20,6 6'6-8·8
Test Starch peak viscosity (AU)" Starch swelling power (gig) Starch swelling volume (ml) " Brabender Amylograph Units.
TABLE II. Simple correlation coefficients between starch paste viscosity and swelling tests. Based on data from 13 cultivars at two locations - Wongan Hills (1987) and Merredin (1988) Correlation with starch paste peak viscosity
Starch swelling power Starch swelling volume
**p
Wongan Hills
Merredin
Overall
0'88** 0,8.4**
0'82** 0,82**
0,80** 0'81**
< 0'01.
TABLE III. Simple correlation coefficients between starch and flour properties and components of noodle eating quality (set 2, 13 samples) Noodle eating quality parameters
Starch peak viscosity Starch swelling power Starch swelling volume Flour swelling volume
Softness
Elasticity
Smoothness
Total score
0,77** 0.70** 0,85** 0,55*
0,69** 0,79** 0,79** 0,68**
0·34 0'49 0'49 0'36
0,77** 0'84** 0,88** 0,69**
* p < 0'05; ** p < 0·01. Results
The range of values of the various tests carried out on samples from the 13 wheat cultivars at two sites (set 1) are presented in Table I. The swelling power values are higher than those previously reported1S, and probably resulted from a more thorough mixing of the samples before and during heating in the water bath. For set 1, starch paste peak viscosity was highly correlated with starch swelling power and starch swelling volume at each of the two locations and with the data combined (Table II). For set 2, starch and flour measurements were correlated to varying degrees with total texture scores and two ofits components, softness and elasticity (Table III). None of the tests were correlated with the smoothness of the boiled noodles, however the samples
STARCH SWELLING AND NOODLE QUALITY
149
tested had only a narrow range of smoothness values (samples were classified into one of three smoothness groups having values of 6, 6·5 and 7). In this set of samples, starch paste peak viscosity was correlated (P < 0'01) with starch swelling power (r = 0'72) and starch swelling volume (r = 0'90). The protein contents of the flour samples in this set ranged from 8·7 to 11'5 %, on a dry basis. Discussion
Associations between tests
The high correlation coefficients obtained from set 1 indicate that starch swelling power and starch swelling volume may be useful alternatives to starch paste peak viscosity in characterizing the quality of starch isolated from flour of different wheat cultivars. The correlations determined between the results of the various starch and flour tests and the assessments of softness, elasticity and total texture score of the boiled noodles (Table III) support previous studies 3 , 5-7 which have highlighted the importance of starch properties in relation to noodle eating quality. Potential application of the tests
The results indicate that starch swelling power provides an alternative measurement to starch paste peak viscosity for predicting noodle eating quality. The test offers advantages over conventional paste viscosity measurements in terms of analysis time and sample size. Starch swelling volume also gave high correlations with starch paste peak viscosity and important aspects of the texture of boiled noodles. The test can be carried out on a 0·35 g sample and should allow a substantial increase in sample throughput compared with the swelling power test. The measurement of flour swelling volume gave promising results, although not as highly correlated with noodle eating quality as starch swelling volume. Nevertheless, variation in flour swelling volume accounted for 48 % of the variation in total texture score. The interface between supernatant and gel was less clearly defined in the case of the flour swelling volume test, but the problem was minimized when samples were viewed with an adequate background light. The flour samples used in this study were of low extraction and further work is needed to assess the importance of milling method and extraction level in relation to the prediction of noodle eating quality by this test. The author thanks the Australian Wheat Board and the Technical Committee of the Flour Millers Association of Japan for providing flour samples and noodle assessments; also W. K. Anderson and R. F. Gilmour for their helpful suggestions in the preparation of this manuscript. The technical assistance of W. J. Lambe and G. Coupar is gratefully acknowledged. References 1. Nagao, S. in •Proc, 39th Annual Conference, Royal Australian Chemical Institute Cereal Chemistry
Division', RAC.!., Parkville, Australia (1989) pp 54-58. 2. Lee, C-H., Gore, P. J., Lee, H-D., Yoo, B-S. and Hong, S-H. J. Cereal Sci. 6 (1987) 283-297.
150
G. B. CROSBIE
3. Oda, M., Yasuda, Y., Okazaki, S., Yamauchi, Y. and Yokoyama, Y. Cereal Chern 57 (1980) 253-254. 4. Huang, S. and Morrison, W. R. J. Cereal Sci. 8 (1988) 177-187. 5. Nagao, S., Ishibashi, S., Imai, S., Sato, T., Kanbe, T., Kaneko, Y. and Otsubo, H. Cereal Chern. 54 (1977) 198-204. 6. Moss, H. J. Cereal Res. Cornrnun. 8 (1980) 297-302. 7. Toyokawa, H., Rubenthaler, G. L., Powers, J. R. and Schanus, E. G. Cereal Chern. 66 (1989) 387-391. 8. Crosbie, G. B. Cereal Foods World 34 (1989) 678---681. 9. Morrison, W. R. and Laignelet, B. J. Cereal Sci. 1 (1983) 9-20. 10. Leach, H. W., McCowen, L. D. and Schoch, T. J. Cereal Chern. 36 (1959) 534-544. 11. Elder, A. L. and Schoch, T. J. Cereal Sci. Today 4 (1959) 202-208. 12. Doublier, J. L. J. Cereal Sci. 5 (1987) 247-262. 13. Kim, H. O. and Hill, R. D. Cereal Chern. 61 (1984) 432-435. 14. Endo, S., Karibe, S., Okada, K. and Nagao, S. Nippon Shokuhin Kogyo Gakkaishi 35 (1988) 7-14. 15. Crosbie, G. B. in 'Proc. 39th Annual Conference, Royal Australian Chemical Institute Cereal Chemistry Division', R.A.C.I., Parkville, Australia (1989) pp 59---65. 16. Japan Wheat Research Association. 'Tables for the Quality Survey of Imported Wheat Cargoes, 1988 F.Y. " J.W.R.A., Tokyo, Japan (1989). 17. American Association of Cereal Chemists. 'Cereal Laboratory Methods', AACC, St Paul, MN (1978). 18. Medcalf, D. G. and Gilles, K. A. Cereal Chern. 42 (1965) 558-568. 19. Moss, H. J. and Miskelly, D. M. Food Tech. Ausl. 36 (1984) 90-91.