Food Product Design: Design Elements - November 2000 - Frozen Pasta and Rice Dishes

November 2000


Frozen Pasta and Rice Dishes

Used as the main course or a side dish, frozen pasta and rice dishes are a quick and easy way to jazz up any meal. Just pop them in the microwave or oven and enjoy homemade taste with little or no work. With choices ranging from ethnic to organic, today’s hungry, hurried consumer can find just about any combination of flavors and ingredients to suit their tastes or dietary requirements.

Pasta’s presence

When it became chic to call spaghetti noodles "pasta," it may have looked like just another fad. But now that noodles appear in the shape of your home state, favorite animal or a Pokémon cartoon character, it’s clear that pasta is an important part of the American diet. Consumers see pasta as easy food — you just boil it. Behind the scenes, however, it is a science of ingredient functionality and processing expertise.

Interestingly, there is no standard of identity for the term pasta. The FDA divides pasta products into either macaroni or egg noodles. Standards of identity, found in Title 21 of the Code of Federal Regulations (CFR) 139.110 to 139.180, have been developed for 15 categories of macaroni and noodle products. The major differences between the two is that macaroni can have added egg white, while noodles must contain egg yolk at a level of 5.5% egg solids on a dry basis in the form of egg yolk, whole egg, or a blend of the two.

Pasta typically starts with dough made from water and durum semolina, a hard spring durum wheat. While the standards of identity permit the use of durum semolina, durum flour, farina, wheat flour or any combination of two or more of these, semolina makes the best pasta. With high levels of the amino acids gliadin and glutenin — required for gluten development — semolina makes pasta that is firm in bite, less starchy and resistant to overcooking. Its natural xanthrophyll and carotenoid pigments give it an amber-yellow color.

Most manufacturers strive to make a quality product. "Quality pasta is one without negative attributes," explains David H. Hahn, Ph.D., director of research and technical service, New World Pasta Company, Harrisburg, PA. "You need a good-quality semolina with at least 12.0% protein. Pasta should not be broken or cracked, so that it holds together in one piece. The dry product color should be yellow to light amber. When cooked, it should be cream to light yellow but not brown or gray, and it should not be sticky. The bite should be clean and not slimy, and have the firmness that the consumer expects." Though easier said than done, a combination of proper ingredient selection and the right processing techniques will achieve this goal.

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Improving pasta

While pasta can be made from just flour and water, functional ingredients used in the basic dough will modify its texture. Protein is the backbone of pasta and so high-protein ingredients are often added. Egg albumin helps maintain a firm texture, and strengthen the network that holds in the starch during cooking. However, due to sanitation and allergen issues, many ingredients have been developed to replace eggs. Their effectiveness in pasta applications varies.

Other firming ingredients include vital wheat gluten and whey-protein concentrate. Midwest Grain Products, Atchison, KS, recommends using a protein fraction of wheat gluten. Labeled as wheat protein isolate, it lends itself well to frozen pasta and can also upgrade lower-quality semolina. Its film-forming capabilities increase dough’s extensibility, reduce stickiness and decrease starch released during cooking. The resulting pasta will be firm, springy and elastic.

Certain gums can help pasta processing. "Propylene glycol alginates (PGA) and PGA/xanthan gum blends are being added to pasta products," says Hahn. "Gums seem to change the texture of pasta and the bite is more firm but much more rubbery. Glyceryl monostearate is used to add process tolerance. Glyceryl monostearate will complex with the amylose and form an insoluble helix that holds in starch and decreases water absorption, thus reducing starchiness and stickiness. Disodium phosphate is used to speed cooking."

To aid the extrusion process add emulsifiers, such as lecithin, or a rice-based emulsifying ingredient from Ribus, Inc., St. Louis. Made from rice bran, this all-natural emulsifier is promoted as improving dough machinability for dry or fresh, sheeted and laminated pasta products.

Many value-added ingredients enhance flavor and color, or boost nutrition rather than provide functionality. Over the last five to seven years, many new products have been introduced with a variety of vegetable powders, seasonings and flavors added, such as roasted garlic, roasted red pepper, tomato basil, pesto, and lemon pepper. As long as addition levels stay below 5%, it will not significantly change the cooking performance of the pasta product. Vegetable macaroni is defined by the CFR and must have a minimum of 3% vegetables; technically only tomato, artichoke, carrot, parsley, spinach and beet are allowed. The standards also cover some spices, however, many of today’s exotic flavor and vegetable combinations do not meet the standard’s requirements.

Egg albumin, nonfat dry milk and soy all raise protein levels. Soy lends a product the advantage of its heightened popularity. Cargill Foods, Soy Protein Products, Cedar Rapids, IA, has developed a pasta that utilizes a high level of soy flour. One serving of pasta provides 6.4 grams of soy protein and meets the criteria for the FDA’s health claim on coronary heart disease. However, care is needed in formulating these products. "Soy protein changes pasta texture and darkens the color," warns Hahn. "The texture is slightly less firm and the bite is less resilient. The pasta breaks when you chew it before you bite all the way through."

Other ingredients can be used to develop health-oriented pasta that stands up to the freezing process. Wheat fiber from J. Rettenmaier USA, Schoolcraft, MI, contributes dietary-fiber enrichment and caloric reduction. Made of cellulose and hemicellulose, it is promoted as having a neutral taste and odor. Pasta with a 5% inclusion can bear the claim "high in dietary fiber." Functionally, it improves the stability of pasta during the freeze/thaw cycle and reduces ice-crystal formation.

Another trend in pasta is wheat-alternative products. Viewed by some as healthier than their wheat-based cousins, their use expands the range of culinary selections from the ordinary to the exotic. For the segment of the population affected by celiac disease who are unable to digest gluten, this is the only choice when the craving hits for a creamy bowl of macaroni and cheese or chicken noodle soup.

Today, pasta-like products can be made from peas, lentils, and other legumes, white and brown rice, corn, potato, amaranth, quinoa, spelt, kamut, Jerusalem artichoke or combination blends. Many claim higher levels of vitamins, minerals and fiber with all the fun of traditional pasta shapes. Unique as they may be, not all of these will perform adequately in a frozen application. Their lack of gluten-forming amino acids results in a softer product that does not hold its shape as well as durum pasta. Because overcooking becomes a problem and freeze/thaw stability may be lacking in glutenless pasta, there is room for ingredient/processing modifications to improve the eating characteristics of frozen pastas.

Processing pasta

Pasta formation has an impact on how it will perform in a frozen application. "The processing alone (blanching, pumping, mixing and packaging) can be tough on the pasta," says Mark Vermylen, vice president, A. Zerega’s Sons, Inc., Fair Lawn, NJ. "Freezing and reheating can result in a pasta that collapses or loses its shape. The frozen-food processor should use somewhat thicker and stronger shapes to withstand the rigors of the frozen-food cycle. A shape just 0.010 in. thicker can make a big difference. Sturdier shapes are less prone to tearing and collapsing. Often a smaller version of a shape will hold up better than the larger, more fragile version. Short goods (such as elbows, penne or shells) are generally easier to use in frozen dishes than are traditional 10 in.-long goods, such as spaghetti or linguine. The long goods are harder to convey and weigh, and often create filling and seal-integrity problems." To use shapes like spaghetti and long goods in frozen dishes, the processor should use custom-made short versions of traditional long goods in lengths of 2 to 5 inches."

Choosing the correct shape can also help produce a better frozen product. "I would choose cut types that hold their shape better, such as a tri-vane rotini rather than a dual-vane rotini, or a smaller diameter tubular shape with ridges, rather than smooth or larger diameter shapes," adds Hahn. "In addition to shape, I would also use cut types that are thicker, such as spaghetti, linguine or fettuccine, rather than vermicelli or angel hair."

According to Vermylen, standard, retail-type pasta may not always meet the needs of the frozen-food processor. "Usually for no added cost, a custom pasta manufacturer that makes a wide variety of shapes can provide a more suitable version for the application," he says. "Additional ingredients can be added as needed."

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Al dente?

When making a prepared frozen pasta dish, the pasta is typically cooked prior to saucing and freezing. When pasta is heated in water, the starch granules hydrate and gelatinize. Starch is embedded in a protein matrix and it is important that it stays within that matrix rather than leaching out. Also, the protein must not be denatured too much or the pasta will loose its integrity.

"Dry pasta should be cooked in plenty of boiling water," says Vermylen. "After cooking, the temperature of the water should be reduced to stop the cooking process. The pasta can also be conveyed under cool water to stop cooking and remove surface starch. Pasta should not be drained to the extent that it begins to dry out. A light coating of vegetable oil can be added to improve handling. The thickness of each pasta shape — generally ranging from 0.020 to 0.060 in. — is the primary determinant of cooking time. Shapes with intricate designs often need extra cooking time. Fragile shapes, such as jumbo shells, are more challenging to cook and handle than sturdy shapes, such as elbow macaroni."

Individually quick-frozen (IQF) pasta is an alternate way to manufacture high-quality frozen pasta dishes. "The operational issues are different with IQF pasta," explains Hahn. "It is more expensive because you are paying someone else to cook it and you are shipping lots of water. You also need frozen storage space at the plant." He cites advantages to using IQF pasta including: eliminating production floor space for cooking, lowering organic content in plant wastewater and reducing negative quality effects of filling/packaging problems."

IQF pasta is usually found as short goods because the long cuts can be very difficult to deal with. Shortened versions of spaghetti, with a length of 3 to 4 in., can be found in IQF form, but is very fragile and requires a tremendous amount of storage space. High-quality meat or cheese frozen tortellini and ravioli are an efficient alternative to manufacturing these cumbersome products. Frozen lasagna sheets cut to the exact size of the pan produce a consistent product with a very homemade appearance.

Wenger Manufacturing, Inc., Sabeta, KS, has developed an extrusion process that actually cooks the pasta before it shapes it. "We use the starch structure to hold the product together as opposed to a gluten matrix," says Gordon Hueber, director of new concept development. "With traditional processing, the functional gluten protein is what holds pasta together. You are not cooking the starch yet, so it is not very functional at that point. When you cook the product, the protein sets, the starch cooks and gelatinizes, and that is what holds the whole structure together. With the precooked process, using twin-screw cooking extrusion, we cook the starch initially. This breaks down the protein structure so it is not as strong and durable, and does not behave like it would in the raw state." The pasta comes out of extruder at a 35% moisture level, is fully cooked and ready to go into a frozen entrée. It requires only hydration, not cooking or boiling. Because it is mixed with a sauce, it will hydrate during the reheating process.

According to Hueber the end product looks like traditional pasta, but with a deeper, richer color because the starch has pregelatinized. "It is more translucent and you see more of the color in the product. It eats very similarly to traditional pasta. There is a shape limitation however, since the starch is cooked before it is formed through the die. This type of dough is very viscoelastic and not as responsive to shaping as standard pasta dough, so the dies need to be made differently. Some of the more intricate and twisted shapes are not possible, but many of the traditional shapes are available."

This process works with a variety of carbohydrate grains, soy or combinations. Because gluten development is not needed for shaping it doesn’t require ingredients that contain gluten proteins. The technology works well for specialized noodles, such as Asian products made from rice, buckwheat or mung bean, or wheat-free varieties that tend to be fragile.

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Rice recap

U.S. consumers’ strong interest in ethnic foods often means formulating with rice, a traditional staple in many of these cultures. "Rice varieties and process types are available in such a wide range that the product developer can find one to fit practically any application," notes Don McCaskill, manager of research and development, Riceland Foods Inc., Little Rock, AR.

Rice consumed in the United States can be divided into three categories based on its size: long, medium and short grain. Long-grain rice is long and slender in shape and the grains cook up to be separate, light and fluffy. Medium-grain rice is plump, becomes moist and tender when cooked and has a tendency to be sticky. Short-grain rice kernels are small and round and absorb more cooking water than long- and medium-grain rice. It becomes very soft with cooking and the individual pieces tend to cling together.

The differences in these characteristics can be explained by the ratio of amylose to amylopectin that make up starch. Long-grain rice has a high level of amylose, while medium- and short-grain rice have increasing levels of amylopectin.

"It is generally accepted that the higher the amylose content, the less sticky the rice when cooked," explains McCaskill. "Rice with a high amylose content also tends to exhibit a drier mouthfeel and firmer bite. Commonly available U.S. rice varieties range from less than 1% (waxy rice) to about 25% amylose. Amylopectin is noted for contributing a soft, gummy texture. The role of protein in rice processing and eating quality is not fully understood. Some believe that rice storage proteins complex with starch and/or lipids as the rice ages, and that these complexes may partially account for the reduced stickiness of aged rice. This concept seems plausible considering the narrow range of protein concentration in milled rice (typically 6% to 7%)."

Other rice varieties are gaining in popularity. Brown rice, with its intact bran layer, contributes a light-brown color, nutty flavor and a chewy texture. Because it provides fiber, has naturally occurring vitamins and offers high levels of protein, brown rice is seen as a more healthful alternative to milled white rice. The high oil content in the bran layer provides essential fatty acids and tocopherols, but also makes it more susceptible to rancidity.

The booming popularity of Asian foods has seen more usage of aromatic rices, including jasmine and basmati. Medium-grain japonica rice and the glutenous short-grain mochi rice are also used in Asian cuisine. While not as popular as pasta, Italian dishes get their creamy texture from aborio rice.

"Any type of rice works well in a frozen entrée," says Nelson Wurth, director of sales and marketing, ACH Food Companies Inc., Memphis, TN. "The choice should be a marketing decision, although some rices process easier than others. It also depends upon the type of equipment and freezing process the manufacturer has."

The frozen-food industry does appear to have a clear favorite. "Parboiled, long-grain rice, from the Southern United States is usually preferred for its superior cooked-kernel integrity and the fact that it is less sticky than regular rice," explains McCaskill. "It is less susceptible to damage during cooking, handling and processing. Furthermore, it presents fewer problems during preparation for freezing."

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Rice on the range

Rice used in frozen foods must be precooked prior to freezing. There is typically not enough moisture, heat or time involved when reheating food to completely gelatinize the rice to a desirable texture. While making rice on the stove seems to be a challenge for most people, the food industry has the process down to a science.

"Cooking rice for prepared frozen entrées is actually quite simple when appropriate equipment is available and a few basic guidelines are followed," says McCaskill. "In contrast to home cooking, rice used in frozen entrées is usually cooked in excess water in a continuous process. Continuous cookers, designed much like vegetable blanchers, are available and do a good job." Typical processing steps include cooking, cooling, dewatering (draining), blending with flavorings and other ingredients, filling, sealing and freezing. The actual cook-time employed is often shorter than that normally stated for the type of rice being used. This compensates for continued softening of the rice during subsequent processing steps and reconstitution by the consumer.

The variety of rice also becomes an important factor. "Processing medium- or short-grain rice on a continuous line presents a challenge," explains Wurth. "Due to the higher amylopectin contents of these rices, the starchiness in the process water sometimes becomes an insurmountable issue."

Rice cooked in a vessel is more like rice made on the kitchen stove. The rice should be brought to a boil, to speed up the transfer of heat and moisture, and then steamed to evenly distribute the moisture within the kernel. Determining the proper rice to water ratio is more critical with rice that is cooked in a closed vessel rather than in a continuous cooker. While the ratio depends upon the desired degree of gelatinization, the general rule of thumb with regular milled-white rice is to use a volumetric ratio of one part rice to two parts water. It really depends, however, on how much water is lost in the cooking process. This is very dependent upon the cooking vessel. If the lid is off, more water is needed, and less for a vessel with a tight-fitting lid. A deep, narrow vessel may require less water than a wide, shallow one due to increased surface area. The age of the rice is another factor. "The age will affect the rice in that it will take up slightly less water during cooking and hence be firmer at the end of the cook cycle," explains Wurth.

Specialty rices offer additional cooking challenges. "Brown rice works very well in frozen applications, especially if it has been parboiled," says Wurth. "Its only drawback is that it takes more than twice the processing time. It cooks slowly due to the intact bran layer on the kernel." Because the bran absorbs water at a slower rate, the starch splits and the cooked product has a characteristic misshapen appearance.

"Basmati, jasmine, and other rice types can be successfully used in frozen foods," says McCaskill. "Since they are not readily available in parboiled form, it is difficult to achieve the same degree of kernel integrity and general appearance that is normally provided by parboiled long-grain rice."

Quick-cooking and intstantized rice, both in white and brown varieties, are another option. These products are cooked and dehydrated and can be prepared anywhere from two to 10 minutes. Cooking times and practices may vary slightly based on the actual instantizing process used. Increased cost and a texture that is softer than traditionally cooked rice is the trade-off for convenience.

If multiple grain varieties are used, as in the case of a pilaf, they should be cooked separately and then blended together, as they may all require different cooking processes and times.

The cooking phase is also a point where flavor can be added. "Instead of cooking in excess water and draining, this would normally require cooking in properly proportioned amounts of rice and liquid so that all the liquid will be absorbed by the rice," says McCaskill. "One alternative that can be used to achieve similar results involves the spraying or blending of a small amount of flavor concentrate to the cooked, slightly warm rice." A light coating of fat or oil will also help to keep the rice separate once it has been cooked.

If cooking rice is not an option due to time or space constraints, the rice industry will do it for you. "With IQF rice, parboiled long-grain rice is again generally considered to be the best starting material," explains McCaskill. "Once cooked, chilled and thoroughly drained, the rice is quickly frozen with liquid nitrogen to keep the individual kernels separate and flowable. More recently, air-impingement freezers have been designed to achieve similar results. Once frozen, the rice is packaged or filled into bulk containers. It must be kept deeply frozen to retain free-flow properties."

Storage and freeze/thaw stability

In a chilled or frozen cooked-rice product, the amylose content plays a significant role in controlling the rate of starch retrogradation. "As starch retrogrades, it returns to a partially crystalline structure similar to that of raw starch," says McCaskill. "As this occurs, water is released (syneresis), and the texture becomes more firm. Since heating reverses retrogradation, this is normally not a problem in rice products that are consumed hot. However, it is an issue that must be addressed in products that will be eaten cold." In the latter case, he recommends using medium-grain rice with its lower amylose content combined with rapid freezing and thawing. Retrogradation occurs much more slowly in amylopectin than in amylose and the rate is most rapid just above 32ºF. The initial cook time may also be extended slightly to result in a softer texture.

Cooked rice will tolerate the freezing process well if the factors affecting retrogradation are well-controlled. The other significant change that can accompany freezing is the loss of structure due to formation of large ice crystals, McCaskill notes. "Like retrogradation, the formation of large ice crystals is promoted by allowing the rice to freeze too slowly. Other changes that can occur, but that are not unique to rice, include freezer burn and oxidation. Both are normally controlled by proper package design."

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A sauce-y complement

Pasta and rice act much like the canvas of a painting, but sauce can make them a work of art. While a chef’s delicate dispersion of cream and stock would be a mouth-watering addition, it would never stand up to the demands of frozen-food manufacturing.

Sauces don’t conform to the rules of culinary past; but they all need to be freeze/thaw stable. The backbone of freeze/thaw stability is often a substituted starch-based stabilizer. Hydrocolloids, such as xanthan gum, carageenan, guar gum and microcrystalline cellulose, can work in conjunction with starch to promote freeze/thaw stability.

Instantized and cold-water swelling starches mean that sauces no longer have to be cooked. A cold mixture can decrease time in the microbial danger zone, reduce required freeze/ thaw cycles and lessen freezing costs. Colder products will not have the flow characteristics of hot ones, which impacts mixing, ingredient dispersion, movement through the plant and depositing. Still, cooking may develop flavors more fully, achieve a desired mouthfeel, keep fats flowing in the liquid state or add an extra food-safety precaution.

Whether the sauce is blended with the pasta or rice or kept separate before freezing is also an important consideration. This not only becomes a question of taste and functionality, but one of economics. There may very good reasons why it might be a better idea to let the starch component defrost, but it is a conclusion that should be arrived at with some consideration. "This decision is often dictated by plant design and equipment limitations," comments McCaskill. "From a product-quality perspective, both concepts have advantages and disadvantages. For example, an entrée product will often look more appealing if packaged just as it will be served. However, separate packaging may enable the development of preparation instructions optimized for each component and will prevent the transfer of moisture between components during reconstitution."

When blending the starch and sauce together, it is important to reduce the temperature of the sauce and starch components before mixing. If the blend is above the gelatinization temperature, the starch component will continue to absorb water and soften and the sauce may thicken too much. If this is not an option, this reaction could be compensated for by undercooking the starch even more and by thinning the sauce.

Some suppliers of rice and pasta will package IQF product in individual pouches so it can just be slipped into the package. Starch packaged separately from the sauce becomes more prone to freezer burn without that extra layer of protection. One option is a protective topical application. Modified food starches can be applied to pasta or rice and form a clear, flexible film, says Michael Kramer, applications scientist, Grain Processing Corporation, Muscatine, IA. "This will partially inhibit moisture transmission and retard water loss which is characteristic of freezer burn."

AGA, Lidingo, Sweden, makes a coating tumbler that is designed to apply the sauce directly to the individual components of a frozen entrée or side dish. Ingredients, such as rice, pasta, meat or vegetables, are loaded into a tumbler and then liquid nitrogen freezes the surface of the ingredients. Sauce is added and the tumbling action rapidly and evenly adheres the ingredients to the frozen product surface. It can deliver an application with a precise weight control variation from 5% to 300%. Sauce hoppers can even be modified for the application of two different sauces on one product. This method is easier and more exact than sauce pellet technology, which is often used today.

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Added features

Many of the most commonly used inclusions, such as meat, vegetables and legumes, can also be found in an IQF form, making them very easy to use. They often require no further cooking or processing and can just be stirred into the finished product. This can be a blessing on the production floor.

Almost every type of meat, from white meat chicken breast to sausage crumbles, can be found in the cooked and ready-to-use form. Convenience is the obvious gain, but the manufacturer loses control over the cuts of meat used and they are also more costly. IQF meat may exhibit "warmed-over flavor," a lack of freshness and fullness in flavor. Also, the juices that form when meat is cooked adds a richness and savoriness that precooked meat doesn’t replicate. They may also have an "institutional look," whether it is the perfect cube shape, or the pellets that don’t look like anything coming out of a kitchen.

Vegetables can be found raw, canned, IQF, dehydrofrozen or dehydrated. Some forms make logical choices for a frozen product. Further processing of raw vegetables can be time-consuming and messy. Canned vegetables are often the solution for hard-to-find ingredients, or those used in small amounts to minimize labor and can disposal. Dehydrated vegetables might be a costly choice for something that is going to be rehydrated and stored frozen. Frozen vegetables are the most logical choice for a variety of reasons. They retain the look, flavor and nutrition of fresh vegetables; are washed, pre-cut and blanched; and depending on the formulation, may not require further cooking. Dehydrofrozen vegetables are also an excellent choice; because of their high solids-to-moisture content, they contribute minimal syneresis. This could be very important when blending a highly colored vegetable into a very light-colored sauce, or in systems that cannot hold in excess free liquid.

Vegetable processors are developing products that are looking more like they were made in our kitchen. Jon-Lin Inc’s, Coltan, CA, frozen foods, line has fire-roasted vegetables roasted over an open flame for authentic roasted flavor with the visual appeal of char-branded marks. The line also includes IQF grilled and sautéed vegetables. These are products that require processing time and capacity that is not typically feasible in the manufacturing setting.

Frozen pasta and rice dishes are catering to more culinary styles than ever before. With the quality of a home-cooked meal, they offer the convenience that is becoming so important. And it is the consumer that is reaping the benefit with their great taste and the goodness of grain-based nutrition.

Lisa Kobs, M.S., is a Minneapolis-based food scientist and technical writer who focuses on new product development.

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