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Building Better Fried Foods

May 1, 1995

23 Min Read
Building Better Fried Foods

 Building Better Fried Foods
May 1995 -- Design Elements

By: Lynn Kuntz
Associate Editor*

*(Editor since August 1996)

  Maybe people consider fried food a special treat. Or maybe they are just lying to the pollsters about how much fried food they really eat. Despite the current trend toward minimizing fat intake, fried foods retain a high level of popularity. They're quick, convenient, and - let's face it - quite tasty.  While fried foods may make life easy for the consumer, the same does not hold true for those who design these products. Quality, cost, consumer appeal and even health all require careful consideration as a fried product is assembled.  From an ingredient standpoint, most fried foods consist of three major components: the food product, a coating, and the frying fat. Sometimes, as in the case of potato chips and other fried snacks, the coating is optional. Each of these building blocks influences the finished product and often they can be engineered to give the best results.The main attraction  Theoretically, anything can be fried. The most common products for this process include meat, poultry, seafood, vegetables (especially potatoes), and composition products such as egg rolls. While fried salty snacks make up a large category, this article will not focus on those types of products. Still, many of the concepts apply, especially those involving the properties of the coatings and the frying media.  Meat - whether derived from four-legged, two-legged or finned animals - consists mainly of protein and water, with some fat and other constituents. The goal is to retain moisture during frying.  "In the matrix, retaining moisture increases cook yields and improves processing," says Jerry Conklin, development leader, food applications, technology performance products, TS&D, The Dow Chemical Co., Midland, MI. "In most fried foods you want to maintain a high moisture gradient between the inside and outside."  Using polyphosphates can provide several benefits, including moisture retention. Although not clearly understood, it appears the phosphates cause the proteins to swell, which increases their water-binding capacity. The phosphates also can help hold added moisture to a limited extent.  "For years, we believed you lost the effect of phosphates at temperatures over 160°F," says William Swartz, director of technology, Rhône-Poulenc Food Ingredients, Cranbury, NJ. "But we found that the effect was merely reduced compared to lower temperatures. The moisture retention gives you better cooking characteristics, a more uniform product, and better texture."  Using the wrong phosphate can contribute undesirable flavor characteristics. High-pH phosphates, such as tripolyphosphate, can produce a distinctive flavor in mild-flavored meats like poultry and most seafood. Flavor enhancers such as MSG can increase the phosphate flavor. A blend will give a better flavor without sacrificing the protein-binding characteristics needed in a chopped and formed product.  "The small drop in pH resulting from a combination of tripolyphosphate and metaphosphate still promotes good binding but gives a much better flavor than a straight polyphosphate," advises Swartz. "You make a slight compromise between flavor and moisture retention, but nothing significant. Also, when forming patties, if you solubilize too much protein the product will tend to stick to the forming equipment."  Phosphates also help with the manufacture of fish blocks commonly used for fish-stick-type products. These are large, compressed blocks of boneless fish frozen on plate freezers and cut to size or reformed. Without phosphates, the blocks tend to have voids and give off moisture very rapidly as they thaw. According to Swartz, phosphates reduce this effect; there is 10 to 20 times more drip loss without phosphate.  Using phosphates in fish blocks for fried applications can reduce the batter blow off that sometimes results when air is trapped in a void. Those made with phosphate tend to be much more solid and uniform. In addition, with the elimination of voids, the product is less prone to breakage.  Hydrocolloids, usually starch and certain gums, also help retain moisture in the finished product. Their water-binding tendencies help reduce cooking loss. This characteristic also contributes to freeze/thaw stability. Gums and starches work as adhesive agents and as partial fat replacers by forming gels. However, careful consideration of the characteristics of a particular hydrocolloid is needed to make certain it will perform its intended function during processing, frying and storage.  "Many gums are heat reversible and the gel will melt under high temperatures," notes Florian Ward, Ph.D., director of research and development, TIC Gums Inc., Belcamp, MD. "Methylcellulose forms a gel upon heating, an effect known as thermal gelation. Some gums, such as alginates, which are widely used in making onion rings, can form irreversible gels."  If a binder or viscosifier is required for the initial forming process, typically the formula would incorporate a product that works under ambient conditions. To prevent moisture loss during frying, the hydrocolloid must maintain its functionality at high temperatures.  "Methylcellulose builds mash viscosity and firmness, so a product extrudes better and maintains its shape," says Conklin. "Once in the fryer, it gels and provides a nice eating texture, although the texture can soften at room temperature. A formulator can use a little more methylcellulose so the product stays firmer longer."  Often starches act as binders and provide viscosity. This requires a product with a low gelatinizing temperature. The internal temperature attained during the frying process will gelatinize the starch so it holds moisture. Since many of these products will be frozen, freeze/thaw stability is often a requirement.Batter up  Most fried products incorporate some kind of coating. These can take the form of a batter, a breading or a specialized film. Often these coatings are applied in combination to produce the desired effect. Several different types within these categories may go by different names, but they are often classified in the following way:  Adhesion batters adhere some type of dry material to a substrate, such as a crumb onto a fish stick. Typically they are high in starch and quite thin. The heavier the batter, the more crumb will adhere. They may carry flavors, and the thicker batters can be used as stand-alone coatings. These will often contain leavening.  Tempura or puff batters usually consist of flour and a leavening system, which allows the product to puff when exposed to the heat of frying. No breading is required to form a thick coating on the product.  Specialty batters or films are often used on french fries to promote crispness. Sometimes they deliver flavor. Many are being designed either to retain moisture or to reduce fat pickup.  Commodity breading can serve two purposes. It may act as a predust which roughens up the surface and promotes adhesion, or it may serve as a very low cost outside crumb. These products consist of cracker meal, fine granulation breading, or even straight flour. When used as an outside coating, commodity breading tends to give a very dense, very hard coating.  Seasoned flour gives distinct textural and appearance properties, such as a crinkled surface.  Home-style or American bread crumb products come from baked, yeast-raised dough, similar to bread. They have an open structure, contain crust pieces and give a home-style appearance. The color tends to be lighter than commodity breading, with some highlighting due to the crust pieces.  Japanese crumb has a structure that is more delicate and open than the home-style crumb. It has a splintered appearance and is very crisp. Traditional Japanese crumb is baked by a dielectric process. An electric current runs through the loaf and cooks it from the inside out which eliminates the crust. Because of this, the crumb is light in color.
  Specialty breading includes products like corn breading or cornmeal-based crumbs, sweet crumbs, colored crumbs, and other products targeted to specific needs or demographic groups.  These products can have a number of functions, but mainly they provide appearance, texture, flavor and, in some formulations, protection from oil or water migration. They tend to be tailored to a specific product and application, depending on consumer preference and process requirements.  "We make Japanese crumb with a proprietary patented process using microwaves to cook the loaf," explains George Manak, senior marketing manager, Griffith Laboratories USA, Alsip, IL. "It gives the same structure as the dielectric process, but the crumb is more resistant to breakdown during processing, especially when the crumb will be recirculated through a breading applicator in a commercial operation."  While we may initially think of batter and breaded products exclusively in terms of frying, they undergo a variety of processes. They can be raw, breaded and frozen. This is done for some foodservice products, vegetables and cheese. The second method requires coating the product, partially frying it, then freezing it. The customer reheats it in a fryer or even an oven. The third way is to coat it, par-fry it, finish it off in an oven, freeze it, then reconstitute it in the fryer or oven. This method reduces the time in the fryer and minimizes oil pickup while retaining much of the fried character.  "With fried foods, everyone's benchmark is the product that comes immediately out of the fryer," points out Jim Martin, R&D manager, coating systems, at Griffith Laboratories. "If the product is designed to be consumed immediately after frying, that's fairly straightforward. If the product ends up in an oven, you do not get the same fried flavor, so we have to mimic that and develop the color so that it looks and tastes the same. The par-fry will help accomplish that."  Ingredients such as sugars also can be used to hasten the browning. If a product is to be fully cooked, it can be done in two ways: either completely in the fryer, or par-fry and finish off in the oven. If it's done in the oven, flavor and texture are still critical issues. The desired crisp texture also must be developed quickly.Better batters  Batters and breading ingredients provide specific characteristics. The list can be extensive, so we will not look at them all in depth here. However, some - especially the hydrocolloids - can provide unique properties and are worth taking a closer look at.  Flour. Flours provide viscosity and promote adhesion through the formation of gluten. Gluten provides structure and texture and can act as a barrier to fat absorption. Flour contains some reducing sugars that caramelize during frying, contributing to the color and flavor of the coating.  Flour is the main component of most breadings. It can be used as is or baked into a crumb. The porosity of these products affects the oil absorption; the more porous the material, the more oil is absorbed.  Corn flour tenderizes the coating and is added to regulate the amount of gas retained in a coating. It also contributes color due to carotenoids and imparts a characteristic flavor.  Leavening. The gas-release characteristics of the specific leavening affect the texture. If the release is too early, the product texture will be coarse and the coating will absorb excess oil. "If you add leavening, you can change the color and texture of a fried product," explains Swartz. "If you have a corn dog coating, for example, you need a leavening system that gives you very rapid results so that the coating can expand very quickly. It's almost like forming a donut; the gas must form before the coating sets up from the heat. You can also make a batter more brittle by the use of leavening."  Protein. Added protein helps the structure or changes the texture. Often this is added in the form of egg or dairy products.  Sugar. Reducing sugars create Maillard reaction products when exposed to heat. This gives the coating color and flavor. Dairy products such as whey contain high levels of lactose which can contribute to this effect.  Flavors and seasonings. Traditionally, coatings contained seasonings - mainly salt, pepper, and some herbs and spices. Today there is more extensive use of flavoring agents to provide more consumer appeal.  "One of the purposes of a coating is to carry flavor," says Martin. "The closer to the surface the flavor is, the more it will volatilize when you add it to the oil."Hydrocolloid happenings  Product designers are deriving some interesting effects by using hydrocolloids in batter and breading products.  Starches have been used traditionally for certain functions, primarily adhesion. However, we are learning how starches affect the coating - not only its performance and adhesion, but also its appearance and texture, especially crispness. This is an important factor in fast food restaurants. They often cook the product and hold it under a heat lamp. This can soften traditional coatings. Using starches in the batters and breadings makes them more resistant to moisture transfer and keeps the texture crispier for longer periods.  "At first starches were used in smaller quantities because they improved the product" notes Dot Gentile, development chemist, National Starch & Chemical Co., Bridgewater, NJ. "Now some formulations have a significant amount of starch. Some experimental formulas use primarily starch as a carbohydrate base. You can make a very thin, almost film-like coating that protects the identity of the substrate. You're not really changing it, but you are adding certain characteristics, like extending the shelf life and adding crispness. There's growing interest in using coatings on vegetables - not just breadings or tempura batter, but something that will act as a protective coating."  Often several different starches are necessary to provide the desired effect. Some promote adhesion but contribute to a softer texture. Others promote crispness, and some work better at reducing fat pickup. Often when starches are used in combination, there will be tradeoffs - crispness at the expense of adhesion, for example.  "I try to teach customers what a particular type of starch will yield. For instance, we use the high-amylose types for filming properties," says Gentile. "They create a good bond between the coating and the substrate. High amylose seems to keep the coating intact. It allows the substrate to retain moisture and reduces its migration to the coating. Then we might add starches that act as crisping agents, but at a high level they can give you a rougher finish The coating wouldn't stay together as well; it might start getting brittle and flaking off. You have to look at what's optimum for your needs, but you really can't have it all."  The high-amylose starches also help reduce fat pickup. With current technology the reductions are not what the industry is hoping for, but Gentile believes that significant progress in that direction is being made. "There are many new techniques and many new starches, and maybe we are nearing a point where we can find an answer," she says.  Even the traditional views of starch in batters are changing. Historically starch was used with other ingredients to build viscosity by binding water, but that may not be the best way.  "It's not wise to add ingredients that take on a lot of water," warns Gentile. "If you create viscosity in that way, when you put the product in the fryer there will be such a violent exchange of moisture and fat that it takes the coating off. The best way to build viscosity is with solids. That's where starches come into play. Most of the flours will take on water. Starches will take in much less water; they don't function until heat is applied."  For the same reason, using starches in batters can help extend floor time. If flour-based batters sit for extended periods, they absorb too much water and fall apart quickly. With starches, there is some initial hydration of the cold water soluble fractions, but the batter subsequently stabilizes.  Gums are also becoming valuable tools in batter and coating applications. Like starches, their principal role as viscosifiers has changed. They are being used to control water, reduce oil pickup, and provide other unique characteristics.  "More and more of what we sell to the fried food area, in fact to the food industry in general, is not what you would call the classic thickeners," observes Conklin. "It's really the very low viscosity grades. Not only do they hydrate faster because they are shorter chain, they deliver the functionality."  Methylcellulose is particularly suited to fried food application. As mentioned, it displays thermal gelation, so high heat enhances its functionality. Another positive is its speed of hydration. Many batters, especially highly leavened tempura systems, are made up with cold water. High temperatures would make them react prematurely.   Methylcellulose hydrates better in cold water than many other gums, and with gums, proper hydration is the key to functionality. Also, if the water is cold the proteins and starches will hydrate less quickly, reducing their competition for the water.  Excessive use of gums can cause several problems. They can adversely affect the texture. A product with too much gum exhibits a chewy texture. Generally use rates above 0.5% of the total fluid concentration will show this defect. With some gums - such as CMC, guar and xanthan - this can happen at levels above 0.2%. Typically, these thickeners are used at levels below 0.1%.  Off-flavors also can occur with excessive amounts of some gums. "Cellulose gums do not have any flavor after frying," notes Ward. "With something like guar, you have a tendency to affect the taste of the product, especially at the high temperatures used in frying."  Many gums can create films that can be useful in fried foods. One potential application cited is the use of gums in a glaze that may be fried, but there are more practical benefits. These films slow fat absorption and moisture migration. Along with starch and cellulosic gums, konjac also provides these benefits.  "We used konjac to coat french fries," says Kathy Niness, business manager, bakery and confectionery, FMC Corp., Food Ingredients Division, Philadelphia. "We were able to achieve a 10% to 14% fat reduction versus the control, and a gain in moisture retention of 3% to 4%. The texture and appearance of the fries were comparable to the control product. We made a solution of konjac, just under 1%, and dipped the french fries before we fried them."  Still, there has been limited success with hydrocolloids in finding ways to reduce the amount of fat in a product. This may be due in part to the fact that the dynamics of the frying process are not thoroughly understood.  "Typically what we see - and many people report this - is a rough mass balance. The more moisture that leaves, the more fat that comes in," says Conklin. "There are ingredients that can affect that, and perhaps at equilibrium there may be an equal amount (of moisture and fat) going back and forth."  But frying is not really described as an equilibrium process. Methylcellulose may keep moisture in for proteinaceous foods like seafood, chicken and meat, but it still keeps fat out. In vegetable products such as french fries, however, retaining moisture is undesirable because it slows the cooking time.  "We've found, however, that using methylcellulose in french fries has no impact on moisture loss," adds Conklin. "Apparently the interaction also depends on what the chemistry of the substrate is. If it's starchy, with a lot of cellulosic cell structure, then perhaps it doesn't change the moisture egress; but if it is proteinaceous, then perhaps it does."  Moisture retention is one area where gums as well as starches show excellent results. They can help prevent moisture loss and shrinkage during cooking. Additionally, during frozen storage they can reduce moisture migration from the matrix into the batter or moisture into the environment, which is a big problem with seafood. They also retain coating crispness longer after the product is fried.  Lastly, gums - methylcellulose, in particular - can improve batter adhesion. Methylcellulose seems to help make the surface more compatible with the coating, acting similar to a coat of primer paint.  "One of the challenges I have been hearing about lately is the difficulty associated with batter adhesion to peppers, like the cheese-filled versions, eggplant and zucchini," relates Conklin. "The first thing that struck me about that group is they all have a smooth, possibly waxy exterior to which batter coatings adhere poorly."Out of the fire  The final major component of a fried product is the frying fat. We covered the basics in "Selecting a Frying Fat" in the July 1994 issue of Food Product Design. Because fat becomes an integral part of the product during the frying process, it is important to make certain that the fat delivers the correct characteristics - flavor, texture, appearance, and health and content claims.  Besides the basic issues, frying fat must exhibit the ability to carry emulsified materials, according to Michael Blumenthal, Ph.D., program director, Libra Technologies Inc., Metuchen, NJ. Frying oils often contain mono- and diglycerides or other surfactants. These help retain water during the frying process. They can carry special flavoring materials and additives or unusual fractions of oils that may be foreign to the primary oils. These can come from the product fried or they may be a component added to change the characteristics of the oil, such as a stearene.  "We believe there are very minor constituents found in different commercial fractionated products," explains Blumenthal. "Some are accelerators for products found in other oils - causing degradation or instability, or keeping the crystals from remaining in suspension even with added emulsifiers. We're down to the ppb level and still finding activity in some cases."  Oil incompatibility is another consideration when formulating or selecting frying fats, especially if the fat used for par-frying was not compatible with the final frying medium.  "An extreme example would be if you chose to par-fry in coconut fat and then the product went into a restaurant that was frying in soybean oil," says Bob Wainwright, director, R&D, ABITEC Corp., Columbus, OH. "Coconut and soybean fat are not very compatible and they would have a tremendous propensity to foam. I can't imagine that someone would actually do that, but it would be the worst possible scenario."  Oxidation and other breakdown products are big problems in the finished product and the frying oil itself. Although antioxidants can be of some help, the synthetics tend to distill off in the steam generated during frying. Tocopherols have been found to have good carry-through in frying and that positively affects the finished product, but their effect is limited in vegetable frying oils.  "Some people, including ourselves, have experimented with periodically adding antioxidants to the fry kettle to maintain a threshold level of antioxidant activity," says Wainwright. "That gets to be a risky situation because most of the levels, especially with the synthetics, are regulated, and that would provide the opportunity to overdose and create problems. It's pretty tricky to monitor how much is left and how much you need to add back. You're talking about ingredients that are legally limited to 200 ppm, so that doesn't allow much of a margin of error."  The oil breakdown products create many serious problems in the fryer and in the finished product. One way to reduce the severity of these problems is by closely controlling the heat in the fryer. Temperatures in direct-fired industrial fryers can get as high as 500°F in the heat-exchange area, according to some reports. This effect can be moderated by employing indirect systems that use heat-transfer fluids such as mineral oil. These types of fryers heat more evenly and can restore lost heat faster.  Filters also can help maintain oil quality. Generally any process that fries food has some sort of filtration system. Many filter aids not only remove particulates, but the suppliers claim they can remove free fatty acids and degradation products.  "Passive filtration is an entrapment of particles," explains Blumenthal. "In some cases, the trapping agent can act as a desiccant and also will occasionally break emulsions."  Active filtration is where either molecules are removed from fat or an ionic species - such as magnesium cations - is introduced that will interact with a fatty acid. While such a treatment appears to reduce free fatty acids upon titration, the process will have converted the free fatty acids into non-titrated soaps. These cause problems of their own because they are powerful surfactants.  A third option is steering the organic reactions. The actual capacity of any filtering agent that will work in any reasonable time is very small. This is controlled by surface area, molecular sites, etc. Removing some of the catalytic materials may either redirect the reaction or slow its rate.  "The filter aids on the market are not very successful in their industrial applications because the most convenient form is a pad containing the powder. These tend to blind, or become blocked," Blumenthal continues. "If you use a powder alone as a body feed, it blinds typical filters. Some of these products can be beneficial, but the basic research on what they are doing has not been done, even by us."  Besides potentially causing health problems, many of the fat degradation compounds affect the finished product. The most noticeable effect is the formation of off-flavors, but the compounds also can affect the frying process. The polymers that form are not good storers or conductors of heat and affect heat transfer to the food.  The rate of transfer is determined by the small molecules that form as breakdown products in the oil, according to Blumenthal. That establishes the thermal conductivity of the oil. As the oil breaks down and leaches materials from the foods, certain materials act as surfactants or wetting agents and cause the oil to cling longer to the wet surface of the food before steam is formed, thus displacing oil. The residence time of the oil on the surface determines how much energy is delivered.  If the thermal conductivity of the oil and the wetting agents are within normal range, the outside of the product crisps and there is enough energy on the surface to be conducted to the interior of the food. If you have too little surfactant, then neither the outside nor the inside of the food gets cooked. If you have an excess of surfactants and you have a lot of small molecules so the thermal conductivity is high, you will get a burning of the outside and an over hardening or drying out of the crust. There will not be enough energy to go to the interior of the food to finish cooking it.  "Most of the practical engineers came to the conclusion years ago that to get the most production through a fry line they should raise the temperature as high as they could, with the thought that they were pumping a lot of energy into the oil and that the food could extract that energy without going below a good crisping point," Blumenthal adds. "That's not so. Energy flow cannot exceed what the food itself can accept. The food has a certain thermal conductivity and heat capacity which changes dynamically as the food cooks and loses water and as materials move inside to make up for the loss of moisture at the surface."  Having said that, what is the best frying temperature? It turns out if designers understand the thermodynamics and the chemistry simultaneously, they can sit down at a computer and determine through simulation and modeling what the frying temperature should be for a given cross-section of a given type of food in a given moment of the history of the oil. It may sound like Tomorrow Land, but some companies have been doing it for over five years.  Both ingredient and process technology seem poised for significant advances in the near future. However, fried foods tend to be very cost-sensitive and this has a great impact on the technology that will be implemented. Building better fried foods is possible, but first we must pay the price.Back to top

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