Westcott Consultants, Greenacre, NSW, 2190
Wheat based foods have been consumed in China for about 3000 years and spread to other Asian countries about 1000 years ago. Northern Asian countries such as China have had an historically high wheat consumption, whereas rice has been staple in the southern parts of Asia (and southern China) because the climate is more suited to rice production.
The past 25 or so years have seen rapid increases in economic prosperity, income, population and urbanisation in developing nations in Asia. This has led to changes in food consumption patterns. Although rice still remains an important part of the diet, consumption is declining. There has been an increase in consumption of wheat based products, accompanied by increased consumption of meat, edible oils, fruit and vegetables and convenience foods. Importantly, there is an increasing demand for better quality food products (DAFT, 2004). Supermarkets are replacing local markets and neighbourhood stores. Western fast food chains such as McDonald’s have expanded rapidly as disposable incomes have risen, and there are many local variations offering Asian menus along similar concept lines.
Asian wheat based foods can be divided in terms of traditional and adaptations of western wheat products. The most important are Asian noodles, western pan or loaf bread, steamed breads, flat breads, dumplings, traditional confectioneries such as moon cake and more western cakes, biscuits (cookies) and crackers.
Asian noodles are made from wheat flour, as distinct from the pastas of Europe, which are made from coarser durum wheat semolina (triticum durum). Asian noodles probably originated in northern China and spread along the Silk Road. Noodles form an important part of the diet in Asia, accounting for up to 40% of flour use in some regions. Noodles mean long life and good health, and are often featured in birthday celebrations.
Several methods of classification of Asian noodles are possible. They can be classified according to major ingredient, and for wheat based noodles, further classification according to salt type (common or alkaline), method of manufacture, post cutting processing and noodle size.
Major ingredients used in noodle making are wheat flour, rice flour, buckwheat flour or starches such as mung bean, potato or corn. Starch and rice-based noodles, which unlike wheat, do not contain gluten, require gelatinisation of the starch during processing to bind them together. Typically, the latter are processed by extrusion or batter cooking methods and will not be considered here.
Method of manufacture
Wheat based noodles were traditionally hand made by processes which involved mixing, rolling and cutting, or by stretching and repeatedly pulling a soft dough to make long strands such as la mian noodles.
The machine made process consists of mixing the raw ingredients - (flour, water, salt or alkaline salt, minor ingredients such as starch, gums, egg, colourings), sheeting to compress the dough crumble, further sheeting to reduce thickness, cutting and forming and may include resting after mixing or between sheeting stages. The process can be completely or semi-automated.
Typical mixing time in a horizontal mixer is 15 min. In the mixing process, the water level is relatively low (32-35%). The aim of mixing is to distribute the ingredients and hydrate the flour particles (Moss et al, 1987). With the advent of vacuum mixers using 40-45% water, some dough development actually occurs in the mixing stage, with subsequent development in the sheeting stages. The dough crumble is passed through 3-7 sheeting rolls. A uniform protein matrix should be obtained before the final cutting (Moss et al, 1987).
The reduced dough sheet is passed through slotted cutting rolls to produce noodle strands. These cutters come in standard sizes with the width of slots varying from 0.6-6mm. Different widths and thicknesses are associated with different noodle types. The noodle profile can be square, rectangular or round. Hokkien noodles, for example, are about 2.5mm square. Japanese style white salted noodles range in width from 0.7-6.0 mm.
Post cutting processing
Further processing stages are boiling, chilling, freezing, pasteurising, drying, steaming, steaming and drying or steaming and frying.
Classification by salt type
The most common system of classification of noodles is based on the presence or salt or alkali in the formulation. White salted noodles (WSN) contain common salt only, whereas yellow alkaline noodles (YAN) contain alkaline salt, with or without common salt.
White salted noodles
Salt level of WSN is typically 1-3%. Salt helps to strengthen the gluten, and inhibit discolouration due to enzymic activity, as well as conferring flavour, and increasing shelf life by inhibiting mould growth.
White salted noodles are usually made from semi-soft wheats or blends with hard wheats in the flour protein range 8-11%. A typical example is Japanese udon, which has a creamy colour and soft, elastic texture and glossy surface appearance. Australia has been supplying ASW (formerly FAQ) wheat to Japan for this product since 1957. Research in Australia and Japan, commencing in the late 1970’s, has established the role of high starch pasting properties and high swelling power in conferring the desirable the soft and elastic textural attributes of udon.
Wheat starch is composed of both linear amylose and branched amylopectin, with approximately 25% being amylose. When heated in excess water, the starch granule swells as it takes up water and gelatinises. A decrease in amylose content is associated with an increase in peak viscosity (Moss 1980, Oda 1980) and increased swelling in starch water suspensions (Crosbie 1991, Konik et al 1993). The flour swelling volume test, a simple test suitable for use in breeding programs was described by Crosbie (1991). It was found to correlate with udon noodle softness (r= 0.55, p<0.05) and elasticity (r=0.68, p<0.01. As with other starch quality measurements, flour swelling volume is highly dependent on cultivar, but is affected by environmental factors such as location and season (Morris et al, 1997).
High swelling starches are associated with a null allele for granule bound starch synthase (GBSS) which controls the biosynthesis of amylose. In wheat, three loci (Wx-A1, Wx-B1 and Wx-D1) encode for GBSS. 40-45% of both Australian and Canadian wheat cultivars lack the Wx-B1 protein (Zhao et al, 1998, Demeke et al 2000). By contrast, only 10% of US hard wheats and 2% of US soft winter wheats lack Wx-B1 (Graybosch et al 1998). Cultivars which have a null allele for GBSS, have higher pasting properties and higher swelling volumes. Wheats with this characteristic form the basis of ASW noodle wheat segregations.
Although starch is an important constituent of flour for white salted noodles, inclusion of non-starch parameters such as protein and grain hardness/softness in predictive multiple linear regression equations with starch swelling power or starch paste viscosity can improve predictions (Konik et al 1992). This is consistent with the market requirements for wheat or flour for white salted noodles in Japan and Korea, which typically specify grain protein content, flour water absorption and paste viscosity. The role of starch is of lesser importance for white salted noodles in countries such as China, where a firmer noodle is preferred. Firmness is governed by both protein content and protein quality (Park et al, 2003).
White salted noodles should be creamy white in colour. This is due to the flour xanthophylls. Noodle b* can be predicted from flour yellow pigment or flour b*, although the latter can be affected by flour particle size. Flour yellowness is under genetic control and quantitative trait loci (QTL) for xanthophylls have been identified (Mares and Campbell 2001).
With increasing globalisation of foods, noodles resembling Japanese udon are beginning to appear in non traditional markets such as China, Taiwan, Australia and the US. Some of these have the typical soft and elastic Japanese style texture, but many are quite firm, although still elastic. It could be speculated that melding of quality preferences may appear with time, or that specific new market segments will develop.
Yellow alkaline noodles
YAN are unique in food systems as they have a pH in the range 9-11. The alkaline salts used include sodium and/or potassium carbonates and are added at 1-1.5% by flour weight. Yellow alkaline noodles are usually manufactured from medium hard to hard wheats in the flour protein range 9-13%. Each noodle type has its own protein range, with regional preferences. They should have a firm, chewy and elastic texture, smooth surface, clean and yellow colour and be free of any darkening or discolouration. The degree of yellow colour is dependent on regional preferences. Examples of YAN are the Asian Cantonese noodle, the partially boiled Hokkien noodle of south Asia and the Chinese noodle of Japan.
Addition of alkali results in noodles which have a characteristic colour, flavour and aroma. Alkaline salts toughen doughs, which become less extensible (Moss et al, 1986). Pasting viscosity is higher under alkaline conditions, due to the swelling of starch. Hence high swelling starch is not necessary for alkaline noodles.
YAN colour is developed as naturally occurring flavonoid compounds which are colourless at neutral pH turn yellow under alkaline conditions. These compounds are found in germ and seed coat (Mares 2003). The xanthophylls, which are unaffected at alkaline pH, act in an additive manner to the pH induced colour change. The yellow colour is often enhanced by the addition of yellow food colourings such as gardenia yellow, tartrazine or sunset yellow. There is an opportunity for wheat breeders to select lines with high flavonoid content while maintaining acceptable levels of xanthophylls (Mares, 2003).
Protein content is an important flour quality determining the firmness of YAN and firmness increases with increasing protein content (Shirao and Moss 1978, Shelke et al, 1990). Protein strength as measured by dough rheological properties and sedimentation volume is also correlated with firmness (Miskelly and Moss 1985, Ross et al 1997).
Ramen, or instant noodles, were first manufactured in 1958 by Nisshin Foods in Japan. Instant noodles are now a popular convenience snack food worldwide. China is the world’s largest instant noodle manufacturer, but per capita consumption is relatively low (15 packs/year). Korea is the world’s largest consumer per capita, with a consumption of 80 packs per year in 2000 (Shin and Kim 2003).
Instant noodles are steamed and fried, or sometimes steamed and dried before packaging. Cup and bagged types may contain dried soup, condiments, dried meats, tofu and vegetables. There is a wide variety of packaging, ranging from premium polystyrene bowls to simple polyethylene wrap. The bagged type are cooked by boiling in water for 2-3 minutes, and the cup type are rehydrated with boiling water for 1-2 minutes.
Instant noodles differ from their alkaline noodle relatives in that the level of alkali is at lower concentration (0.1-0.6%). In addition to sodium and potassium carbonates, instant noodle kansui powder contains other alkalis such as sodium pyrophosphate and sodium metaphosphate. As instant noodles are modern manufactured foods, many other functional ingredients are added. These include modified starches (potato, tapioca), stabilisers (eg guar gum, alginates, carboxymethyl cellulose) and antioxidants. Addition of modified starches allows hydration at a lower temperature and helps prolong bowl life, while conferring an elastic texture. Oil uptake is of vital commercial importance to manufacturers, due to the relatively higher cost of oil compared with flour. The oil content of commercial instant noodles averages around 21% (Gore et al, 1988). Protein content of flour is inversely related to the oil uptake (Gore et al 1988, Park and Baik 2004). During frying, large oil filled voids are distributed uniformly inside the noodles made from lower protein flour, whereas in higher protein noodles, the oil filled voids are much less, particularly at the centre of the noodle (Moss et al 1987).
Higher protein flours tend to produce firmer noodles, with the correlation between flour protein and instant noodle firmness reported at 0.65, P<0.01 by Gore et al (1988). In a survey of commercial instant noodles from different countries, Azudin (1998) found a variation of protein contents (7-12%), suggesting a range of flour types and grists are common across the Asian region. There was a wide variation in the firmness of these noodles. Protein quality also contributes to firmness. Park and Baik (2004) reported a correlation of 0.645 (p<0.05) between SDS sedimentation volume and noodle firmness, indicating that both protein content and quality need to be considered by instant noodle manufacturers.
Flour quality for noodles
Correct wheat selection and milling process will ensure high quality flour for all Asian products, but particularly noodles. Wheat grades from the 3 major wheat exporting countries are used for making noodle in Asia. The Australian Marketing grades for noodles are Australian Prime Hard and ASW (noodle), but noodles are also made from Australian Hard and APW. Noodle segregations contain selected wheat varieties with specific properties. WA ASW (for udon noodle) accepts the varieties Arrino, Cadoux, Calingiri and Eradu and Gamenya. The eastern Australian States udon noodle varieties are Rosella, Sunsoft and Lorikeet. The variety Rosella is used as the basis of an identity preserved class that has been used for production of Japanese udon noodles.
Minimum quality criteria such as test weight, screenings, freedom from contamination and disease, variety and protein content are specified in the grade receival standards of the major wheat exporting countries. A minimum falling number, usually 300 seconds, is important because of the sensitivity of noodles to rain damaged wheat, which include inferior texture (Moss 1980) and dark colour (Edwards et al 1989).
Noodle flour quality is usually defined in terms of protein or gluten content; protein quality as measured by mixograph, farinograph, extensograph or alveograph; flour purity as measured by ash, colour grade, tristimulus colour meter or image analysis; starch quality as measured by Visco/Amylograph, RVA or swelling volume; flour particle size and starch damage.
Most mills producing noodle flours will carry out end product testing in the laboratory. Noodles are assessed in terms of processing quality (water addition, crumb size, sheet stickiness, tearing, strand profile), texture (smoothness, firmness, elasticity, instrumental texture analysis) and colour (fresh and cooked noodle colour, colour stability and specking).
Historically, the success of Australian wheats for Asian noodles has been based on white wheats. Recently, both US and Canada have focused breeding efforts on the development of white wheats, which are specially segregated and marketed. There is also interest in the production of dual purpose white wheats, suitable for both noodles and bread. White wheats have tended to produce noodles with better colour and colour stability. This has been due to the generally lower levels of polyphenol oxidases (PPO) in white wheats but is subject to genotype and environment interactions (McCallum and Walker 1990, Baik et al 1994, Park et al 1997). As PPO is concentrated in the seed coat, good milling protocols to reduce bran contamination and low extraction rates (40-50%) can help minimise bran contamination. Generally an ash of <0.50% is specified, with premium grade noodles having a flour ash of <0.40%.
PPO is under genetic control, and breeding programs look for low PPO levels in wheats destined for noodles, either as grain PPO or noodle color. The latter is measured with a tristimulus colour meter, as L*, a* and b*. Both flour and noodle L* are correlated with protein, ash and starch damage (Miskelly, 1984). Colour stability, expressed as delta L*, is a measure of noodle darkening over time, and is the difference at 24 and 2 (or 0.5) hours. It is correlated with PPO activity (Mares and Campbell, 2001). Noodle colour stability is also affected by non-PPO background darkening. The mechanism is still unidentified (Mares, 2003). Darkening of noodles can be inhibited by salt addition, acid treatment, freezing, cooking and modified atmosphere packaging, which are all used commercially.
Steamed bread originated in China about 1700 years ago. Steamed bread can be plain (mantou), or filled (buns/bao). Generally, steamed breads are consumed fresh daily, but many frozen types are now available as access to domestic refrigerators/freezers is much more common. Huang (1999) has identified three major types of steamed bread, Northern, Southern and Guangdong, differing in fat and sugar content, specific volume and texture.
Doughs are often mixed in low intensity mixers, or traditionally by hand at home. Typically, steamed breads are made at 10-15% lower water additions than pan bread. Sponge and dough, straight dough, no time and short fermentation are used to make the different styles.
After mixing, doughs are divided into pieces of 130-150g by hand, dough moulder or co-extrusion. Proofing is carried out under ambient or controlled conditions for 30-40 min. Steaming can be carried out over a wok containing boiling water, or in commercial steaming cabinets.
Steamed breads should have smooth, white, shiny external skin, free from blisters and blemishes. The crumb should be white and uniform, with texture dense or open, depending on the style. Eating quality should be elastic, with cohesiveness appropriate to the style.
Dough strength is the most important quality parameter in predicting suitability of flours for Northern style steamed bread (Huang et al, 1996), whereas both protein content and strength are important for Southern style steamed bread (Huang and Quail, 1996). As with noodles, use of rain damaged wheats should be avoided for steamed buns.
Dumplings (jiaozi) are another sheeted product popular originating in northern China but now popular thoroughout Asia. The dough is mixed with about 40% water before sheeting, rolling and filling. They can be hand or machine made and are sold as fresh or frozen convenience foods. Dumplings are steamed, boiled or stir fried (Huang 1999). They should have a bright, white colour and a smooth and elastic texture. The wrapper should not split during freezing or cooking. Optimum flour quality for frozen dumplings is 10.5-11% protein, 400-550 Rmax, with high FSV and clean and white colour (Huang et al 2002).
Soft wheat products such as sponge cakes, biscuits, cookies, and crackers are popular in Asia, but may have different flavours and taste preferences. With the increasing globalisation of the food industry, many international biscuit (cookie) companies have set up manufacturing in Asia, utilising modern manufacturing and packaging methods. One aspect of this is the emergence of regionally recognised flour types for biscuit, cookie and cracker flours.
Asia has a wealth of traditional products such as hot cakes, pancakes, fried sticks (you tiao), mooncakes, crispy snack (sa qi ma) traditional cookies, flaky pastries and sesame balls. There is little published in the western literature about specific quality requirements for these products, but this is expected to change as research extends into these product applications.
End product testing
Prior to the late 1970’s, the only end products envisaged in Australian wheat testing were bread and cookies. Research in collaboration with overseas scientists enabled the setting up of appropriate small scale and Asian and Middle Eastern end product tests. Such tests are integral to the wheat classification and testing process, not only in Australia, but in other wheat exporting and importing countries.
End product research has been a feature of our Cereal Conferences over the years, especially in 1988 and 1998, when the fifth Pacific Rim Symposium was held in Cairns. The current Asian Foods Symposium follows in this tradition.
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