Truth of Grain
December 1995 -- Design Elements

By: Scott Hegenbart
Editor*

*April 1991-July 1996

  For many reasons, product designers are increasingly using whole-grain rice as an ingredient. When the designer is presented with a concept that uses rice, however, the job is only beginning because many different types of rice are grown and suppliers can mill it into many different forms. Understanding the variety of whole-grain rice ingredients is the first step to including them successfully in food product formulations."Rice-ing" to the occasion  Many motivations support formulating with rice. First, consumers continue to want healthier food products. White rice contains only 103 calories per half-cup serving, and brown rice has 106 calories per half-cup serving. Rice contains a very high percentage of carbohydrates with only a trace of fat. The protein in rice is well-balanced because all eight amino acids are present in proper proportions.  Rice also is popular, as indicated by significant consumption increases since 1977. Today, 75% of American households serve rice one or more times per week, versus 46% in 1977. This increase in consumption is thought to be driven by consumers positive perception of rice's nutritional attributes.  In addition to nutritional benefits, rice is a popular ingredient for fulfilling special consumer needs. Rice is a low-sodium food for those with hypertension. For infants, those with celiac disease or gluten sensitivity, rice can be used as a grain substitute for wheat because it is gluten-free and nonallergenic.Variety in the varieties  More than 40,000 different varieties of rice exist worldwide, but only a small number are of acceptable quality for commercial cultivation in the United States. Those that are grown domestically can be divided into three general classifications: long, medium and short grain.Long Grain rice has a long and slender shape, as much as four to five times long as it is wide. Typical long grain rice has a length-to-width ratio of about 3:1. When cooked, long grain rice grains tend to remain separate and are light and fluffy.Medium Grain rice is plump, but not round. When cooked, these grains are more moist and tender than those of long grain and have a greater tendency to cling together. The length-to-width ratio of this type of rice is about 2.0 to 2.9:1. Ninety-six percent of all rice grown in the United States is either long or medium grain.Short Grain rice is almost round, and the grains tend to cling together when cooked. It also is a little softer than medium grain.  Many varieties of rice fall into these general categories. Each has certain attributes that might be more favorable in certain applications. Such specialty varieties include waxy rice, high-amylose rice and aromatic varieties.Waxy rice is short and plump with a chalky white, opaque kernel prior to cooking. It is very low in amylose. After cooking, this rice loses its shape and is very glutinous. This type of rice is used primarily as a functional ingredient. For example, the starch and flour from waxy rice is used as a binder in frozen gravies, sauces and fillings because it helps curb syneresis during freeze/thaw cycles. Waxy rice also serves as the raw material for further processed, rice-based functional ingredients.Aromatic rices have a flavor and aroma similar to that of roasted nuts or popcorn. The natural compound that gives aromatic rice these organoleptic properties is present in all rice, but at much higher concentrations in the aromatic varieties. Two kinds of aromatic rice are grown in the United States: a Della-type, which cooks separate and fluffy; and a Jasmine-type, which cooks more moist and tends to cling together.  A primary difference among the many rice varieties is the starch composition of the grain. Amylopectin -- the type of starch found in the highest proportion in medium, short and waxy rice -- makes these varieties more tender with a greater tendency to cling. Amylose, on the other hand, is the type of starch found in long grain rice. It makes long grain rice cook up fluffier with separate and distinct grains that tend not to cling.  The amylopectin:amylose ratio in rice determines the textural properties of the rice when it is cooked. The greater the percentage of amylopectin, the greater the water absorption capacity of the starch and the lower the temperature at which the starch of the grain will gelatinize. Because rice is available in a range of amylose:amylopectin ratios, an equal range of gelatinization temperatures also exists. This also allows users to select a rice that will retrograde to a lesser degree.Expanding the spectrum  Besides the many types of rice available, several different post-harvest treatments yield even more choices. The exact milling procedure and the degree to which the rice is milled determine the form it takes and how it performs.Rough (paddy) rice is rice as it comes from the field after harvesting. Paddy rice has an inedible hull surrounding the kernel which must be removed before the rice can be consumed. This tough outer covering should not be confused with the bran, which remains even after dehulling.Parboiled rice. For this, the rice mill first removes straw and other foreign material using a series of machines. Some mills then produce parboiled rice using a steam-pressure process. While still in the husk, parboiled rice is soaked, steamed and dried prior to milling. This procedure gelatinizes the starch in the grain to ensure discrete rice kernels when cooked. It also forces nutrients from the bran layer into the center of the grain. The resulting rice is fluffy and separate, and retains more nutrients than unenriched regular-milled white rice. Parboiling is not the same as precooking. In fact, rice that has undergone the parboiling process takes a few minutes longer to cook than non-parboiled rice.  Whether parboiled or not, the rough rice, still in its inedible husk, is then dried and continues through the regular milling sequence.Brown rice. The mill next passes the rough rice through shelter machines which remove only the outer hull to yield brown rice. Brown rice consists of whole or broken kernels that have a slightly chewy texture and a nutlike flavor when cooked. The light brown color is caused by the presence of seven bran layers that are rich in vitamins and minerals -- especially the B-complex group.Regular-milled white rice. Machines further mill brown rice by rubbing the grains together under pressure to remove the bran layers by abrasion. The result of this process is regular-milled white rice, also called milled rice, milled white rice, polished rice or polished white rice. The hulls, bran layers and germ all have been removed and the rice is sorted according to size. Rice can be specified in many sizes, including a range of broken piece (grit) sizes.  "There are not a lot of differences in rice milling that have a functional impact," says Keith Hargrove, director of technology, Farmer's Rice Cooperative, Sacramento, CA. "But the amount of bran remaining, or the degree of milling, can impact the functionality."  During milling, some of the nutrients in non-parboiled rice are lost because they are contained within the bran. For this reason, most rice is enriched with iron, niacin and thiamin. The U.S. Food and Drug Administration specifies the enrichment levels for these nutrients at a minimum of 2 mg of thiamin, 13 mg of iron and 16 mg of niacin per pound of raw rice.Precooked rice has been completely cooked and dehydrated after milling. In the dry form, this rice is more porous so boiling water can penetrate the grains more easily and reduce the necessary cooking time. Instant rice allows complete reconstitution in just a matter of minutes.Rice Flour. In addition to the different sizes and granulations of whole kernels, milled rice often is ground into flour which can be used in many baking applications to replace wheat flour.  Rice flour itself is far from being a standard ingredient according to John Kendell, director of process development, Riviana Rice, Houston. It can be made from any of the different types of rice, such as long or medium grain. It also can be ground from rice that has been processed differently, such as raw, versus parboiled, or even instantized rice. As with any flour, the granulation may vary from a coarse grit or meal, to a fine powder. Even how the flour is ground can make a difference in performance.  "Two conventional methods are used to make rice flour -- roller mills and some form of hammer, or pin mill -- and these can create differences in functionality," says Hargrove. "Hammer/pin mills tend to create more starch damage, which can be either an advantage or a disadvantage, depending on the application."  A large rice supplier can custom-tailor the process to yield a rice flour with the exact functional properties desired.  "If you want to add crispness to a cracker, we may select a specific variety, perform a certain degree of parboiling, and instantize the rice for a specific rehydration time before making the flour," says Kendell.  "We've even worked with baby food companies and those making geriatric foods who are looking for a specific mineral content."  In addition to flour, rice is processed into many derivative ingredients, such as starches and protein isolate. This article, however, focuses only on the primary, whole-grain rice ingredients.Rice in action  No hard-and-fast rules exist on which type or form of rice is best suited for a formula. Much depends on the concept of the product, with consideration given to the desired product configuration. Medium and short grain rice would be good choices for foods that require a creamy, clingy texture, such as molds and desserts. Long grain rice would be better for the separate, distinct grains that are desirable in pilaf or other rice-based side dishes.  Brown rice is well-suited to "good-for-you" products. Many consumers perceive it as more nutritious than white rice because it contains slightly higher levels of protein, calcium, phosphorus, potassium, niacin, fiber and vitamin E.  Brown rice will, however, contribute to higher ingredient costs for several reasons. First, a superior quality -- and, therefore, higher cost -- grain must be used. The bran must be a uniform, characteristic tan color which requires careful selection of the grain varieties because the hull and bran colors may vary. In addition, the grains must go through the milling process at one-third the speed of white rice. Mill operators also must watch the milling more carefully and divert brown rice at the proper time so the bran layer is not milled away inadvertently.  Rice has potential in a wide range of food categories. In a 1993 survey conducted for the USA Rice Council, the top five categories where new product development may include rice are snack foods, prepared/frozen entrees, breakfast cereals, soups, and prepared/packaged side dishes. Here is a look at the specific rice properties each of these categories requires.  Snack foods. Rice's chief advantage in snack foods is its bland flavor. Because many snacks are flavored through a topical seasoning, rice provides a more neutral base that won't interfere with other flavors or contribute flavor of its own.  "Generally, other flours have distinct flavor characteristics, and sometimes that flavor is desired," says Frank Orthoefer, vice president, research and development, Riceland Foods, Little Rock, AR. "Rice flour, for the most part, has very little flavor. You often can use less salt or other flavorings."  Because the starch matrix of rice is different from other grains, it also can contribute light, crispy texture to products. Keep in mind, however, that flour made from waxy rice tends to hold water. If products that contain this flour are not sufficiently dry after baking or extrusion, they may end up with a gummy texture.  The type of rice affects snacks in other ways, too. "In snack foods, puffed products will be expanded by either oven puffing or direct "extrusion," says Don McCaskill, manager, rice research and development, Riceland Foods. "Probably the most common type used will be medium grain, which will be lower in amylose content. But there's no reason why long grain can't be used."  Adds Orthoefer, "Short grain will be predominantly amylopectin. It will behave differently in the extruder, and the finished product will have a finer meltaway. Medium grain will have more residence time in the mouth. Long grain will make an acceptable product, but won't have the fine texture of the short grain."  In addition to type, the milling process also affects rice performance in snacks. The more puffing required of the finished piece, the more gelatinized the raw material should be. Therefore, parboiled rice tends to extrude and puff better than non-parboiled.  The size of the rice after miffing is important. For extruded products made on a cooker-extruder, a coarser rice grit should be used. For formulated snack chips or crackers, a finer rice flour is required.Prepared/frozen entrees. These products most commonly contain whole-grain, cooked rice. Because of this, the appearance of the cooked kernels is the primary selection criteria among the long, medium and short grain rice varieties. Although simply selecting the type of rice that looks good is one method, it is not always sufficient. Medium grain rice, for example, has a starch profile that is much more resistant to retrogradation.  The ethnic tradition of a food also is an influence. Cajun and Creole foods, for instance, are often very spicy. Rice is used as an accompaniment to many such dishes to calm the flavor. Here, a formulator might select a long grain type with the discrete grains desired in side dishes. With other Cajun offerings, rice is an integral part of the dish itself, which affects the type chosen. Jambalaya, for example, usually is served molded by a cup. To duplicate this effect in a packaged product, a product developer would want a rice with more cling and should select a short or medium grain rice. In addition, many Cajun and Creole dishes traditionally use aromatic varieties of rice.  Other examples include Asian and Caribbean cuisine. In these locations, cooks most commonly have short grain rice available, so this type is more appropriate when creating an authentic product from these ethnic categories. Even in these regions, though, the rice cannot be generalized so easily.  "Look at your product characteristics," says Hargrove. "If you're looking for a sticky Japanese or Korean rice, you'd probably go with a medium Japonica rice. If you're looking for a more separate rice with a firmer texture, then you'd go with a long grain."  The way the rice is processed also can make a difference. Parboiling rice gives it better kernel integrity after it's cooked, so it is more resistant to the rigors of handling when processed in the plant. In fact, most prepared, frozen entrees use parboiled long grain rice.  "Parboiled rice has good structural stability; it goes through the processing system very well and gives you a very acceptable product when the consumer heats it" says Orthoefer.  Precooked and instantized rices offer more than mere. convenience, as well. According to Kendell, instant rice tends to be drier and stickier than regular milled rice.  "Precooked or instant can be an advantage from the perspective of preparation time," says Hargrove. "But there also may be better freeze/thaw stability because of the starch's gelatinization."Breakfast cereals. The most familiar rice-based breakfast cereal by far is the expanded rice kernel. Of the types of expanded rice kernel, the oven-expanded version is the most popular in the United States. (Oven-expanded rice has a crispy, open texture that makes noise when milk is added and is commonly found in confections. Gun-puffed rice has a spongy, dense-appearing, yet light texture.) Regardless of expansion method, the predominant type of rice used is medium grain.  "Medium grain has a low amylose content and a high amylopectin content and tends to expand more in the oven puffing process," says McCaskill. "One of the more common classes of medium grain is called 'second heads,' which is the largest fraction of broken kernels."  Rice -- primarily as a grit or flour -- also is used in formulated extruded breakfast cereals. As in snacks, rice's neutral flavor is useful for products that are non-grain flavored, such as a children's fruit-flavored cereal. Rice's water-holding capabilities, however, present some challenges to the very rapid extrusion process.  "Using raw rice flour with totally extruded cereals may result in a product with a slightly gummy texture," says McCaskill. "Using pregelatinized rice flour to make an unfinished pellet, then oven- or gun-puffing the result eliminates this."  Soups. How rice is used in soup differs depending on whether the soup is canned or an instant mix. In canned soup, the rice is exposed to the heat of retorting and is stored in a moist environment for an extended period. This stress causes the rice to "butterfly," or partially split at the ends and fray. Selecting the right variety of rice can prevent this. Rexmont and New Rex are two long grain varieties developed with a higher amylose content so they experience less solids loss and, therefore, resist "butterflying" in conventionally canned products.  The big problem with those is that the production yields and the milling performance have been somewhat poor," says McCaskill. "This has put them in the situation of having to be contracted in order to be grown. This, in turn, runs the price up substantially. To my knowledge, there are no substantial amounts of them available."  The butterfly resistance of canning rice usually is enhanced by parboiling. This often is done with other long-grain rice varieties to improve their butterfly resistance. Unfortunately, while heavy parboiling does help maintain kernel integrity, it doesn't necessarily help the rice retain a firm texture.  "By partially gelatinizing the starch in the rice, then drying it, it will take longer to absorb water when put into a soup," says Orthoefer. "Such rice may go through the entire retort process before it expands,"  For instant dry soups, product designers don't have processing to contend with. Here, the primary goal is to select a rice that will cook up in the same amount of time as the rest of the mix.  "The most popular is an instant parboiled rice based on long grain," says McCaskill. "The product will cook in approximately 5 minutes with moderate preparation."  If a shorter preparation time is needed, the designer may select a freeze-dried rice. Although the preparation time is longer -- 7 minutes -- quick-cooking rice has the advantage of tasting more like cook-up rice than parboiled rice.  Prepared/packaged side dishes. These products have the rice milling requirements of dry soups, but they also require the same variety of rice types as prepared entrees. The type of rice will depend largely on the product concept. For example, if the rice must be fluffy and separate, select long grain. If it should be sticky, choose short grain.  "Medium and short are the types that are best at holding a sauce. You'd use the long grain for a fried rice or something like that," says Hargrove. "Very little instant short or medium grain rice is produced, but some is available. It's growing because of demands for convenience."  As with instant soups, the type of milling the selected rice should have received depends on the cook-up requirements of the product. In the future, however, product designers will be able to select rice that has been processed for specific concepts. One rice supplier has been experimenting with processing long-grain rice so it has a soft risotto-like texture for Italian dishes.  Remember that quick-cooking rices, instant rices, and so on, tend to absorb moisture. This can take place just as easily in a mix's package as it can in a cooking vessel. All of the ingredients in a dry mix should have their water activities selected so they are similar to that of the rice. In some cases, certain ingredients, such as seasonings, will have to be packaged separately to avoid moisture migration. Again, however, one rice processor has been experimenting with producing a low-moisture rice that will equilibrate with the seasonings at a desirable water activity and moisture level.Function follows form  Once the formulator selects the type and form of rice, he or she will undoubtedly start by preparing prototypes and lab samples using it. Here, a proper procedure must be followed to ensure preparation for optimum quality and easier scale-up.  Many manufacturers prepare rice much as a consumer does, only on a larger scale. The procedure starts with accurate measurement of the rice and cooking liquid, as well as the cooling time. For regular-milled white rice, the ratio of liquid to rice is two to one by volume. This varies with the type and form of rice, and with the cooking liquid selected.  When rice is enriched, the nutrients are applied as a topical coating. As a result, rice ordinarily is not prepared in blanchers which cook using large amounts of water that is then drained. Rice also ordinarily is not rinsed before or after cooking. Any of these may result in loss of enrichment and other water-soluble vitamins and minerals. There are, however, specially enriched rices that have water-resistant nutrient coatings. These may be selected if the speed of blanching rice in the plant is desired.  "For many industrial applications, even at the lab scale, I'd suggest cooking in a manner to duplicate the plant operation," says McCaskill. "Blanching by cooling in excess water gives you more control over the residence time as opposed to methods based on home preparation."  In ordinary preparation, rice is cooked by steam, so the system must be closed to prevent steam from escaping. After preparation, the rice should be stirred to allow steam to escape (this prevents over-cooking) and to keep the grains separate.  In general, rice preparation follows this procedure: Rice, liquid salt and fat (butter, margarine, etc., is optional) are added to an appropriately sized vessel. After heating to boiling, the mixture should be agitated slightly and the heat lowered to a simmer. The vessel would then covered and the rice allowed to steam for the appropriate amount of time.  If, after this time has passed, the rice isn't tender or the liquid has not all absorbed, the cover should be replaced and 2 to 4 minutes added to the cooking time.  Parboiled rice takes about 25 minutes to cook, compared with 15 minutes for regular-milled rice. It also requires a greater proportion of cooking liquid. Brown rice has a still longer cooking time of 50 minutes because the outer bran layers act as a barrier to heat and moisture. Like parboiled rice, it requires more cooling liquid than regular-milled rice does.  Rice doesn't have to be prepared in water only. Variations of the ingredients in the cooking medium allow product designers the flexibility to alter the rice's prepared quality. For example:  Acid mediums such as tomato juice, fruit juice and wine tend to make the rice grain cook firmer and to lengthen the cooking time. These liquids should be diluted one-to-one with water.  Milk tends to lengthen the cooking time and may scorch. When preparing rice with milk in the lab, use a double boiler, increase the amount of liquid by up to 75%, and increase the cooling time to 40 minutes for regular-milled rice.  Fat helps keep the grains separate when preparing rice. If raw rice grains are sautéed in fat, the coating of fat not only helps keep the grains separate, it also tends to break down the starch on the rice's surface, resulting in a slightly mealy texture and butterflied grains.  Sugar in the cooking liquid -- especially at higher concentrations -- will result in firmer rice grains. This effect is reduced when using medium or short grain rice.Handling the larger scale  Rice preparation is readily adapted to larger cooking vessels in both the pilot plant and the production facility.  Theoretically, you could work with as little as one rice kernel and -- if you define the parameters of that kernel's treatment -- it should translate well," says Hargrove. "Of course, the thermodynamics will be different, but the general treatment of the rice translates well."  Again, accurate ingredient measurement and timing are critical. Remember, also, that unless you are blanching with a specially enriched rice, use a minimum of liquid to preserve the nutrients.  Among the mechanical requirements to consider, make sure that the cooking system is closed in order to trap the steam which actually cooks the rice. Also, a means of breaking up or "fluffing" the rice after cooking must be accommodated. This is especially true if the rice is to be used in entree-type food products.  If time is a factor in production, quick-cooking or precooked rices are an option for product designers. Many instant rices require only 5 minutes of cooking time after the rice is added to boiling water. Precooked rices require only from 2.5 to 10 minutes of simmering time. Fully prepared, individually quick-frozen (IQF) rice is yet another possibility; it just needs heating prior to use. In fact, many larger rice suppliers will not only precook rice, but package it in individual pouches and freeze it too, so the product manufacturer has only to add a pouch to the finished product package.  In the lab or plant, milled rice -- white, parboiled or precooked -- will keep almost indefinitely in unopened containers. If the original package is opened, the rice should then be stored in a tightly closed container that keeps out dust, moisture and other contaminants.  The production facility should be aware that the oil in brown rice's bran layer can become rancid. This gives it a shorter shelf life than white rice. The shelf life can, however, be extended by keeping brown rice in refrigerated storage.  Indeed, all rice is not alike. By choosing among the different types, forms and preparation options, product designers can achieve a number of flavor and texture effects in the products they create. Proper selection, formulation and preparation is not difficult with rice, and it will result in greater value and quality in the long run.Back to top