Frozen noodles and chilled noodles are types of instantly prepared Asian (or European) noodles that are sold frozen or chilled. These products differ from prepackaged dehydrated noodles in a number of ways, both in flavor, texture and in that they normally come pre-prepared with ingredients in addition to the noodles, such as vegetables, meat, and soup stock.
Chilled or frozen applications are applied to both udon and Chinese-style noodles. For either type, the idea is that just 20-60 seconds of immersion in boiling water is necessary to reach a ready-to-eat state. As of 2001, chilled noodles accounted for sales of ¥400 billion yuan wordwide (approximately $8,500,000,000 U.S. as of 2001) while frozen noodles accounted for sales of ¥70 billion yuan worldwide (approximately $48,300,000,000 U.S. as of 2001). A large part of these revenues were accounted for by sale to restaurants.
The production of both chilled and frozen noodle starts with boiled noodles cooked to an optimum state of doneness, generally considered as having a moisture gradient at the surface of the noodles of 80% moisture absorption, and at the core of the noodles of 50% moisture absorption. After boiling, chilled noodles are placed into packaging followed by refrigeration at between 4-10 °C (39.2-50 °F). Frozen noodles, by contrast, are flash frozen using either air blast technology, a contact freezer or a combination of both, usually at -40 °C (-40 °F) for 30 minutes. Both processes induce a swelling of the starch that reduces deterioration and thus extends the noodles' shelf-life.
Frozen noodles have been cited as having advantages over dried noodles, the process tending to make them less sticky, firmer and thicker than their dried counterparts. Both frozen and dehydrated noodles have a longer shelf-life than chilled noodles, which tend to clump after approximately two weeks of refrigeration due to gelatinisation of starch.
While both Frozen and chilled noodles offer convenience for the mass market, and for short preparation times, each have been found to cause loss of optimal texture when tested using alkaline and white salted noodles. In a 2001 published study by D. W. Hatcher and M. J. Anderson of the Canadian Grain Commission, textural attributes of the frozen variety were tested at 1 and 4 weeks after frozen storage, and the chilled variety at the 30 minute and 1, 2 and 7 days marks. Both the frozen and the chilled noodles showed a decline in textural characteristics which increased in severity the further forward in time they were sampled after storage. It was also indicated that the texture of raw frozen noodles, cooked after defrosting, as opposed to precooked and then frozen noodles, fared much better.