Cooking processes include parboiling, boiling, and steaming. Hokkien noodles and Chinese wet noodles are usually parboiled for 45-90 seconds to achieve 80- 90% gelatinization in starch. The noodles are then coated with 1-2% edible vegetable oil to prevent the strands from sticking together. Parboiled noodles have an extended shelf-life (2-3 days) and high weight gain (60-70%). They are quickly re-cooked by boiling or stir-frying prior to consumption.

Japanese udon noodles are boiled for 10-15 minutes, rinsed and cooled in running water, steeped in dilute acidic water before packing, and further steamed for more than 30 seconds in a pressurized steamer. This type of noodle usually has a shelf-life of 6 months to one year. It is also called longevity noodle.

Several steps can be taken to assure optimal cooking: (a) the weight of cooking water is at least 10 times that of the uncooked noodles, (b) the size of the boiling pot is properly chosen, (c) the pH of the boiling water is 5.5-6.0, (d) the cooking time is precisely controlled to give optimal results to the product, and (e) Page 7 the cooking water temperature is carefully maintained at 98-1000 C throughout the boiling process.

In making instant noodles, the wavy noodle-strands are conveyed to a steamer to cook the noodles. As mentioned earlier, the purpose of steaming is to gelatinize the starch and fix the noodle waves. The steaming time varies according to noodle size, but can be determined by squeezing a noodle strand between two clear glass plates. If the white noodle core disappears, the noodles are well cooked. Steam temperature, steam pressure, and steaming time are key process factors affecting the product quality.

Drying Noodles

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.

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