Wheat flour noodles are an important part in the diet of many Asians. It is believed that noodles originated in China, then spread to other Asian countries. Today, the amount of flour used for noodle making in Asia accounts for about 40% of the total flour consumed. In recent years, Asian noodles have also become popular in many countries outside of Asia. This popularity is likely to increase. This article is written to provide information on related aspects of noodles.
ASIAN NOODLES VERSUS PASTA
Asian noodles are different from pasta products in ingredients used, the processes involved and their consumption patterns. Pasta is made from semolina (coarse flour usually milled from durum wheat) and water, and extruded through a metal die under pressure. It is a dried product. After cooking, pasta is often eaten with sauces. Asian noodles are characterized by thin strips slit from a sheeted dough that has been made from flour (hard and soft wheats), water and salt— common salt or alkaline salt. Noodles are often consumed in soup. Eggs can be added to each product to give a firmer texture.
WHEAT USED IN NOODLES
The key noodle wheat growers and suppliers are the United States, Australia and Canada. In the US, hard red spring, hard red winter, soft red winter, and soft white wheats are used—alone or blended—for making noodle flour. A new wheat class—hard white— has been expanding in production in recent years, targeting Asian products such as noodles and Chinese steamed breads apart from Western foods. Australian wheat has been known for decades for its superior performance in Japanese type noodle making because it gives desirable noodle color and unique texture. Australian standard white, Australian premium white, Australian hard, Australian prime hard, and Australian noodle wheat are major types of noodle wheats. Canada western red spring, Canada western red winter, Canada prairie spring white and Canada prairie spring red wheats are also competitive in noodle production. In many cases, different classes of wheat are often blended to achieve relatively consistent quality noodle flour. Due to the complexity of noodle types (discussed later), there is no single wheat type that can meet all quality requirements, not to mention that the consistency of wheat quality and supply also varies.
Seven Major Types
Tremendous varieties of Asian noodles exist around the world and within a country (Table I). These varieties are the result of differences in culture, climate, region and a host of other factors. Table II shows the formulation of seven major types of noodles. Both Chinese raw noodles and Japanese udon noodles have the most simplified formulas, containing only flour, water and salt. However, as indicated earlier, Chinese raw noodles are made from hard wheat and medium to high protein flour, and Japanese udon noodles are produced from soft wheat flour of medium protein content. Chinese raw noodles have been shown to be very useful in screening noodle color due to their simple formulation. Chinese wet noodles and chuka-men (alkaline noodle) are characterized by the presence of kan sui (alkali salt), while Malaysian hokkien noodles are characterized by the presence of sodium hydroxide, giving the noodles their characteristic yellowness, alkaline flavor, high pH and improved texture. Both Chinese wet and hokkien noodles are parboiled types, while chuka-men can be either uncooked or cooked. Instant fried noodles usually contain guar gum or other hydrocolloids, making the noodles firmer and easier to rehydrate upon cooking or soaking; polyphosphates allow more water retention on the noodle surface, thus, giving them better mouth-feel. Native or modified potato starch or other equivalent starches are often added in premium instant fried noodles, providing springy texture and improved steaming and cooking quality due to reduced gelatinization temperature. Thailand bamee noodles are characterized by having 10% eggs in the formula. Therefore, egg source and quality are additional variables in bamee noodle quality.
NOODLE PROCESSING TECHNOLOGY
The basic processing steps for machine-made noodles are outlined in Figure 1. These steps involve mixing raw materials, resting the crumbly dough, sheeting the dough into two dough sheets, compounding the two sheets into one, gradually sheeting the dough sheet into a specified thickness and slitting into noodle strands. Noodle strands are further processed according to noodle types.
Mixing formula ingredients (Table III) is often carried out in a horizontal or vertical mixer for 10-15 minutes. Since the horizontal mixer seems to have better mixing results, it is more commonly used than the vertical one in commercial noodle production. Mixing results in the formation of a crumbly dough with small and uniform particle sizes. Since the water addition level is relatively low (vs. bread doughs), gluten development in noodle dough during mixing is minimized. This improves the dough sheetability, sheeted dough smoothness and uniformity. Limited water absorption also slows down noodle discoloration and reduces the amount of water to be taken out during the final drying or frying processes.
Flour proteins and starch (especially damaged starch) determine the flour water absorption level. Even so, the water absorption level in noodle dough is not so sensitive to processing as is that in bread dough. Variation in noodle dough water absorption among different flours is generally within 2-3%, and this is usually determined by dough handling properties. Flour particle sizes and their distribution affect the time water penetrates into the flour. Large particle flours require a longer time for water to incorporate and tend to form larger dough lumps. It is desirable to have relatively fine and evenly distributed particle size flours to achieve optimum dough mixing.
After mixing, the dough pieces are rested for 20-40 minutes before compounding. Dough resting helps water penetrate into dough particles evenly, resulting in a smoother and less streaky dough after sheeting. In commercial production, the dough is rested in a receiving container while being stirred slowly.
Sheeting and Compounding
The rested, crumbly dough pieces are divided into two portions, each passing through a pair of sheeting rolls to form a noodle dough sheet. The two sheets are then combined (compounded) and passed through a second set of sheeting rolls to form a single sheet. The roll gap is adjusted so that the dough thickness reduction is between 20-40%. The combined dough sheet is often carried on a multi-layer conveyor belt located in a temperature and relative humidity controlled cabinet. This step is to relax the dough for easy reduction in the subsequent sheeting operation. The resting time takes about 30-40 minutes.
Sheeting, Slitting and Waving
Further dough sheeting is done on a series of 4-6 pairs of rolls with decreasing roll gaps. At this stage, roll diameter, sheeting speed and reduction ratio should be considered to obtain an optimum dough reduction. Noodle slitting is done by a cutting machine, which is equipped with a pair of calibration rolls, a slitter, and a cutter or a waver. The final dough sheet thickness is set on the calibration rolls according to noodle type (Tables I and VI) and measured using a thickness dial gauge. Noodle width determines the size of noodle slitter to be used (noodle width, mm = 30/slitter number). The sheet is cut into noodle strands of desired width with a slitter. Noodles can be either square or round in shape by using various slitters. Noodle strands are cut into a desirable length by a cutter. At this stage, Chinese raw noodle, Japanese udon noodle, chuka-men and Thailand bamee noodle making is complete. For making instant noodles, noodle strands are waved before steaming and cutting.
Noodle drying can be achieved by air drying, deep frying or vacuum drying. The air drying process has been applied to many noodle types, such as Chinese raw noodles, Japanese udon noodles, steamed and airdried instant noodles, and others. Air drying usually takes 5-8 hours to dry regular noodles (long and straight) and 30-40 minutes to dry steamed and airdried instant noodles. Drying by frying takes only a few minutes. Vacuum drying of frozen noodles is a newer technology making it possible to produce premium quality products. For the manufacture of regular dry noodles, raw noodle strands of a certain length are hung on rods in a drying chamber with controlled temperature and relative humidity. Air drying usually involves multistage processes since too rapid drying causes noodle checking, similar to spaghetti drying. In the first stage, low temperature (15-200 C) and dry air are applied to reduce the noodle moisture content from 40-45% to 25- 27%. In the second stage, air of 400 C and 70-75% relative humidity is used to ensure moisture migration from the interior of the noodle strands to outside surfaces. In the final stage, the product is further dried using cool air. For the manufacture of air-dried instant noodles, wavy noodle-strands are first steamed for 18-20 minutes at 1000 C, then dried for 30-40 minutes using hot blast air at 800 C. The dried noodles are cooled prior to packaging. Air-dried instant noodles have a low fat content so some people prefer them. They also have a longer shelf-life because little fat rancidity is involved. Steaming appears to be very critical to this type of noodle since it affects the water rehydration rate of the product. However, slow output of the process and lack of pleasant shortening taste and mouthfeel make the product less popular in Asia compared with instant fried noodles. Drying by frying is a very fast process. Water vaporizes quickly from the surface of the noodles upon dipping into the hot oil. Dehydration of the exterior surface drives water to migrate from the interior to the exterior of the noodle strands. Eventually, some of the water in the noodles is replaced by oil. Many tiny holes are created during the frying process due to the mass transfer, and they serve as channels for water to get in upon rehydration in hot water. It usually takes 3-4 minutes to cook or soak instant fried noodles in hot water before consumption.
Asian noodles have been in existence for thousands of years. They are now also becoming popular in the Western countries. Several types, mostly machinemade, are produced worldwide. Research on Japanese udon noodles is ahead of other noodle types. Process properties, noodle color and noodle texture are the three key quality attributes in the evaluation of a wheat flour for any noodle making. Noodle process behavior is of particular importance in modern industrial production, but this property is often ignored in laboratory evaluation. In terms of noodle color, brightness is required, and whiteness or yellowness is essential depending on the noodle type. Noodle texture, however, is more complicated in the characterization of each noodle type, and progress can only be made to understand this property by involving Asian flour and noodle industrial representatives. Instrumental measurements of noodle color and texture are important in establishing their relationship to sensory characteristics of noodles.
Extract from intern by Jingcheng Machinery
ASIAN NOODLE TECHNOLOGY
Wheat Marketing Center
Portland, OR 97209