Tortilla Chips

  Tortilla chips were originally made from leftover tortillas when the remaining dough was cut into pieces and fried. The tortilla-making process was developed by early Latin American Indians. "Many scholars think that all of the successful ancient cultures in Latin America developed a process like this for corn," says David Jackson, food scientist at the Institute of Agriculture and Natural Resources, University of Nebraska, Lincoln. Possibly one of the reasons is that the alkaline corn-processing method increases the availability of B vitamins and proteins and decreases some toxins. Commercial alkali treatments can also significantly increase calcium content, depending on the number of washing steps and the type of alkali used.

  In the traditional process, corn grain is cooked in boiling lime solution for five to 50 minutes, then steeped overnight. This alkali treatment loosens the pericarp, which generally floats free. It also improves hydration and starch gelatinization characteristics. The steep liquor, or nejayote, is discarded, and the remaining steeped grain and germ mixture is washed. The resulting product, which is called nixtamal (the steeping process is called nixtamalization), can also be referred to as hominy. Kernels should be intact so that damaged kernels do not disintegrate completely during the drying, lime cooking and washing processes.

  The next step is grinding the nixtamal into a dough that is referred to as masa. This grinding process serves to homogenize the mass, gelatinize the starch and denature the protein. Naturally, the conditions of grinding - the gap between the stones, any wearing of the stones, pressure, speed, time, temperature, moisture loss from the masa - will affect the dough, which is where experience with the nuances of the process becomes important. In the last step, the masa is flattened into thin disks, and both sides are baked 30 to 60 seconds on a hot griddle, or comal.

  The industrial tortilla-making method is rapidly overtaking the traditional method in Mexico, and has always been dominant in the United States. It's a scaled-up version of the traditional process in which the masa is dehydrated and packaged as flour, to be wetted later and formed into tortillas. (For more information on tortilla manufacture, see "Viva Tortilla" in the February 1999 issue of Food Product Design.)

  Over the past 10 years, even Mexico's tortilla industry has seen a shift from traditional masa dough to industrial corn flour, from a use level of 21% dry flour in 1991 to 50% in 1997. This is largely due to flour's ease of use and increase in efficiencies, which include: less water consumed; lower industrial waste; better hygiene; extended shelf life (wet dough vs. dry flour); higher yield; lower fuel and labor costs (no cooking facility required); and improved dough consistency (more continuous process, less downtime). Large Mexican manufacturers produce many different types of flour. For example, Grupo Minsa S.A. de C.V., headquartered in Los Reyes Ixtacala, Tlalnepantla, makes 28 different flours, differing in granulation, cooking time/temperature, steeping control, corn hybrids and additives. Hybrids include blue corn, white and yellow. Organic flours come in blue, white and yellow as well. Minsa also produces a dehydrated whole pre-cooked corn-kernel mix for millers to use in masa production.

  In the United States, more than 70% of all corn and tortilla chips start with corn-masa flour, produced by companies such as Grupo Minsa's U.S. operations in Red Oak, IA and Muleshoe, TX; Gruma SA de CV, San Pedro, Garza García, Mexico, (Azteca Milling, Irving, TX); Cargill, Minneapolis; ConAgra, Omaha, NE; and Quaker Oats, Chicago.

  Tortilla chips begin with corn, which contains about 14% moisture, 74% starch and 9% to 10% protein. White and yellow dent corn is the source of most corn flour and meal. The endosperms of these varieties have a hard, glassy surface and soft cores, but manufacturers use other types to achieve product differentiation. In addition to the variations created by the different types of corn - red, blue, white and yellow - the chips themselves can contain less common ingredients such as beans and sesame seeds, and yes, even one brand made with hemp. The type of corn as well as these added ingredients not only provides flavor, but also textural differences. For example, blue-corn flour has a coarser, grainier consistency than yellow or white dent-corn flours, resulting in a denser texture and a sweeter, nuttier taste.

  To make tortilla chips, corn is cooked in steam kettles for better temperature control with dry, powdered lime, Ca(OH)₂. Steam is injected to bring the temperature to about 100°C, and the mixture is circulated by pump, mixing and steam to keep the corn and lime in suspension. This temperature is held for four to eight minutes. Cold water is then added to stop, or quench, the process, and the cooked corn is held at 40° to 45°C for 12 to 16 hours. Insufficient steep time can make the corn difficult to mill and too much steeping can result in a sticky masa.

  Next, the nixtamal is washed by pumping into rotating barrels or onto a washer elevator, and sprayed with water to remove the pericarp, lime and solubles. After a few washing stages, the corn is conveyed to an attrition mill, where lava or aluminum oxide stones cut, knead and mash the corn to form masa. The particle size of the masa is determined by the width of the space between the stones.

  All aspects of this milling process are critical to quality, and the stones require constant maintenance to ensure end-product consistency. As noted for the traditional process, pressure, speed, temperature and moisture must be standardized, which can be achieved by a large, dedicated, continuously running process, as found in corn-flour mills. Smaller operations can look to dry corn masa to achieve consistent quality and to eliminate the complications of making masa in-house.

  The finished masa is conveyed to a sheeter, where it is roll-reduced to the proper thickness - 0.10 in. for standard restaurant "table" tortilla chips, 0.03 in. for a Tostito-type snack chip. The dough is cut into a final shape (e.g. round deli-style vs. wedge-shaped restaurant-style), and conveyed into a triple-pass gas-fired oven, where the chips are baked for 15 to 30 seconds at 575° to 600°F. This removes moisture from the chips, which then enter an equilibrator, allowing residual moisture to evaporate or migrate evenly, and preventing blistering or puffing due to pockets of moisture forming and evaporating when the chips contact the frying oil. Equilibration requires a longer, lower-temperature, multi-pass process than the baking step.

  Frito-Lay and Purdue University, West Lafayette, IN, have developed a quality check at this point in the process, using a sensor to measure in-process moisture before the chip reaches the frying oil. According to Steve Bresnahan, senior project engineer, Frito-Lay: "The result, coupled with a model-based, closed-loop control system, was a more consistent finished product. When we applied a similar sensor and control to our potato-chip process, consumer preference for our chip over our competitors' shot upward from parity to 70% just by making each chip consistently meet product design."

  Once formed, tortilla chips are typically fried in partially hydrogenated soybean oil, cottonseed oil or canola oil. Peanut oil might also be used; it has a high monounsaturated fat level, so it resists oxidation, but it is also less bland in flavor than other oils. With the recent announcement of proposed trans-fat labeling requirements (see this month's "News" section for more details), chip companies may lean toward high-oleic, low-linoleic, low-linolenic oils (sunflower, canola, soybean) to maintain oxidative stability and provide a "healthier" image.

  The frying process typically falls somewhere in the range of 365° to 390°F for approximately 60 seconds. The oil requires filtering to remove impurities from the frying process. This holds down the level of free fatty acids, which contribute to oil degradation.

  Baked tortilla chips bypass the frying operation and will typically bake out in a zone oven with re-circulating air for 10 to 15 minutes at relatively low oven temperatures (300°F) to prevent burning.

  Following the baking or frying process, chips are usually salted, and might also receive a seasoning coat by traveling through a tumbling dryer, which ensures even seasoning dispersion. In the case of a baked chip, there's no residual oil on the surface, so a light oil application or a starch, gum or other tacky coating (such as lecithin, sugars, proteins or composite mixtures) must be applied to allow the seasoning to adhere. Some companies have also used an electrostatic seasoning system to help toppings adhere to baked chips. In this process, the seasoning is run past a charged wire, and the tumbler recieves an opposite charge that is transferred to the chips. This difference in charge helps the seasoning adhere.

  The market share for more healthful chips boomed in the 1990s, led by "better-for-you" snacks such as baked varieties and fat-free products, which drove the market in 1997 and 1998, but have since leveled out. While a large number of regional chip producers entered the baked-chip market, many found that consumers would not compromise on taste, and the market leveled off.

  Probably the biggest changes in the better-for-you category of chips have come as a result of the fat replacer olestra. This heat-stable non-digestable sucrose polyester was approved by the FDA in 1996. A tortilla chip fried in olestra only contains 90 calories per oz. vs. 140 calories per oz. with a chip fried in regular oil. The commercial form has a melt point of 140°F and a smoke point of 480°F, so it can be treated like a fat for frying purposes. The viscosity is greater than that of a triglyceride made of similar fatty acids because of the increased molecule size (six to eight fatty acids plus a sucrose molecule vs. three fatty acids on glycere backbone for a true fat).

  Frito-Lay negotiated exclusive use of Olean®, Procter & Gamble's brand of olestra, in snacks through May 28, 1999. Since exclusivity expired, two regional chippers have debuted new fat-free chips with olestra (so far, no tortilla chips, but further introductions are promised).

  Frito-Lay's Wow!® brand of chips made with olestra was the most successful food introduction of the 1990s, with $350 million in sales in its first year. Sales peaked in 1998, and have since flattened. Sales have disappointed some analysts, but there's no shame in that sales record, since many were doubtful that consumers would give olestra a chance at all, especially given the required labeling information. Cincinnati-based Procter & Gamble has done well with fat-free Pringles®, and hopes to continue with fat-free Eagle snacks.

  The USDA recently published a draft commercial item description, or CID, on tortilla chips. As recommended by SFA, this is a voluntary guideline designed to be flexible enough for the inclusion of new sizes, shapes and flavors.

  Another interesting development, this one from the FDA, permits health claims for lowfat popcorn and baked tortilla chips. Submitted by General Mills, Inc., Minneapolis, the decision means that certain products (containing 51% or more whole grains per reference amount and meeting other conditions related to healthy products, such as fat or sodium content), may carry the following label statement: "Diets rich in whole grain foods and other plant foods and low in total fat, saturated fat and cholesterol, may help reduce the risk of heart disease and certain cancers."

  Differing shapes and new claims represent some of the changes in tortilla chips, but flavors are also a constant topic. A look around the industry reveals cheesy nacho, salsa-and-black-bean, hot-n-spicy, BBQ, cool ranch, smoky red BBQ and lime-flavored varieties from some of the larger companies. According to the SFA's "1998 State-of-the-Industry Report," the top six flavors snack-product manufacturers were interested in for all snacks were: hot-and-spicy, onion-and-garlic, ranch, honey mustard, barbecue and cheese. Other suggested flavors in the SFA survey include chili-and-lime, salsa-and-cheese, cinnamon, hot chicken wing, hot-and-spicy cheese, applesauce, garlic-and-vinegar, crab, honey, coffee, maple barbecue, and roasted garlic.

  "Other natural trends might be cilantro-and-lime, fresh tomato, roasted garlic with butter and herbs, and taco-and-cheese. Since many consumers use the regular flavor with salsa, why not use salsa-associated flavors in the tortilla chip?" says Jeff Gruber, project manager, Kerry Ingredients, Beloit, WI.

  On the demographic side of things, research from the Advertising Research Foundation, New York, NY, indicates that Hispanics are 52% less likely to eat salty snacks, primarily because they are too mild in flavor. The group looked at four products - Dorito's Salsa Verde, Lay's Adobaditas, Frito's Flamin' Hot Sabrosito's, and Lime 'N Chile Sabrosito's - that were introduced in 1997 in San Antonio. The result? Sales of Dorito's increased 32%, with Salsa Verde representing 15% of all sales. When these products were introduced to other largely Hispanic areas in 1998, sales topped $100 million, and Dorito's Salsa Verde represented nearly 50% of that amount.

  As with any other product, quality is the key to tortilla-chip success. What to look for in a tortilla chip? Obvious areas are crispness, color, mouthfeel, consistent flavor and appearance.

  And, while regular tortillas are relatively low in fat, the chips are fried in oil, resulting in a hefty, but desirable, 22% to 25% oil range. Lower-oil chips may be tough and have poor mouthfeel, and over-oiled chips will taste very greasy, so this specification is important. Moisture removal is critical to reaching the target oil range, and is also critical to appearance characteristics - final moisture should be less than 2%.

  Color can be standardized by precise controls in time, temperature and moisture. No consumer is fond of broken, burnt, folded, puffed or pillowed chips, so control of appearance is critical. Flavor is also crucial, so oil quality must be maintained, and salt, seasoning and additional topping-oil percentages must be monitored. As with many products, consistency improves with steady-state processing, so longer runs are favored.

  Ethnic products are "in," so tortilla chips can be thankful for their Latin American heritage. And, as the use of masa derivatives in the United States increases, consumption of their snack cousins will likely also increase, with new flavors and varieties to keep the concept fresh.

Ronald C. Deis, Ph.D., is a consulting food scientist based in West Chester, PA. He specializes in food ingredient technology and process/ingredient troubleshooting, and has a strong formulation background in baked goods and wet systems. He hosts a website at http://hometown.aol.com/rcdeis/deiswebpage.htm.