December 1996 -- Applications
By: Stuart Cantor
The Unites States Department of Agriculture (USDA) Food Guide Pyramid says we need to eat at least five servings of fruits and vegetables per day. This is not only sound nutritional advice for consumers, it's good news for food processors because fruit can provide functional benefits, too.
Fruit pieces, juices, extracts, pastes and purees are important ingredients with applications in a wide range of food and beverage products. They can contribute sweetness, color, consumer appeal, natural preservatives, and a smooth mouthfeel and texture, which aids in fat replacement. Fruits act as natural humectants which can extend the shelf life of many foods. They also contain many phytochemicals that are important to human health.
Cut the fatFor the past decade, the food industry has rushed to meet the demands of consumers who want low- and no-fat products. According to a 1994 FIND/SVP survey, the market for low-fat and low-cholesterol foods increased from $15.7 billion in 1992 to $23.5 billion in 1993 and is estimated to be $44.9 billion in 1997.
Consumers scan food labels for natural ingredients with names they can recognize, in addition to looking at the fat content of foods. One of the ingredients used to replace fat in high- and intermediate-moisture products is fruit.
Fat provides many functions in food systems. It acts as a carrier for fat-soluble vitamins and provides lubricity, creamy mouthfeel, texture and satiety. But fat also carries a heavy caloric load: 9 kcal/gram. Because fat performs so many roles in foods, it is difficult to create a no-fat product that still tastes great, is low in cost, and satisfies demanding consumers. Fruit-based ingredients can replace many of the functions of fat.
When fat is removed from a food system, other ingredients must be used to control added water and to improve taste, appearance and product texture. Fat mimetics, many of them carbohydrate-based, imitate fat by tying up the excess water and providing smooth body and mouthfeel. Fruit purees and fruit juice concentrates contain natural hydrocolloids, such as pectin, as well as humectants and dietary fiber. Different fruits have different levels of these three constituents which allow them to control moisture.
Low-moisture fruit fibers are available from a variety of fruits, including apple, fig, pear and citrus. These fibers provide bulk and bind water to improve texture in low-fat baked goods and breads.
Water usually makes up the majority of ingredients added back to a formulation after fat has been removed. Water activity (Aw) measures the free unbound water available for microbial growth in foods. It is a very important parameter to consider when designing reduced-fat foods. Most bacteria are unable to grow below a water activity of 0.90. Most spoilage yeasts and molds cannot grow below 0.80 Aw. At the levels they are normally used, hydrocolloids do not significantly reduce the Aw; however, the sugars contained in fruit-based fat replacers can help lower the Aw.
In low-fat desserts and baked goods the excess water added to compensate for fat reduction can dilute the product's sweetness. Adding concentrated fruit juice can help increase the sweetness and aid moisture control. Fructose is a very good humectant. It readily absorbs and retains moisture, which helps maintain freshness in these products.
How sweet it isFruits and fruit products provide sweetness due to their relatively high concentration of sugars. Fructose, a natural monosaccharide, is abundant in fruits and is approximately 20% sweeter than sucrose on an equivalent weight basis. Sucrose is a disaccharide that consists of equal amounts of glucose and fructose. Many consumers look at fruit juice and fructose as "natural" alternatives to processed sugar. A single-strength apple juice would contain, on average, 5.9% fructose, 2.7% sucrose and 2.0% other sugars.
Fruit-based sweeteners tend to be more expensive than high fructose corn syrup and sugar, but they provide several advantages. They add soluble and insoluble dietary fiber, color, a unique flavor profile, several vitamins and minerals, and "label appeal."
The strength of purees, juices and concentrates is measured by their percent soluble solids content, called Brix. Most commercial juice concentrates and purees range from 20 to 70 Brix. Standardizing the Brix with water helps ensure a consistent level of sweetness in the food product.
The sugar content of single-strength fruit juices is too low for them to be used effectively as sweeteners in many food applications. Juice concentrates are prepared by pressing the juice from the fruits and then concentrating it by either heat or vacuum evaporation. The resulting juice can have a slight haze caused by residual pectin, or it can be clarified with a pectinase enzyme.
"With the actual fruit, the sugar level can vary widely depending on things like variety or maturity," says Scott Summers, technical service manager, Industrial Ingredients Division, Treetop Inc., Selah, WA. "Concentrates and purees are standardized in terms of Brix so you get a known sugar content. However there are differences in perceived sweetness because the sugars may display synergistic effects as a result of the actual types present."
Concentrated puree can be manufactured by the same method, but it contains more fruit pulp and fiber. Apple and pear concentrates are most commonly used as sweeteners because of their bland flavor and light color.
Sometimes a food technologist must use a juice concentrate with reduced color, flavor and acidity in order to design products without imparting a characteristic taste of the fruit. Decreased-potency juices can be obtained by carefully selecting ripe fruits and using conventional extraction methods. The juice is further evaporated to the desired Brix under vacuum at low temperature using a multi-effect evaporator with an essence (flavor) stripping apparatus, notes Daniel Song, western sales account manager, American Fruit Processors, Pacoima, CA.
Color my worldThe appearance of a food product can greatly influence a consumer's purchasing decision. Many products -- such as fruit fillings, baked goods and beverages -- look unappealing without additional color. Fruit can impart color to products without the use of artificial ingredients. Consumer interest in the elimination or reduction of artificial colors has spurred growth in the supply of all natural food colors.
The only natural color extracts currently permitted by the FDA for use in food are red cabbage, beet juice or powder, carmine, grape skin extract, and color extractives from grapes. These natural colorants are defined by the FDA as exempt from certification and are listed in Title 21, Code of Federal Regulations (CFR), Part 73.
Grape skin extract, or enocianina, is obtained by the aqueous steeping of fresh deseeded marc (the material remaining after grapes have been pressed to produce grape juice or wine). The FDA restricts the use of grape skin extracts to alcoholic beverages, beverage bases, still and carbonated drinks, and lemonades (21 CFR Sec. 73.170).
Grape color extract is an aqueous solution of anthocyanin grape pigments made from Concord grapes or a dehydrated water-soluble powder of this extract. It is made by extracting the pigments from the precipitated lees formed during the storage of Concord grape juice, and it yields a red color. This can be used to color a number of non-beverage foods, including gelatin desserts, fruit fillings and some confections (21 CFR Sec. 73.169).
"Another product that is commercially available as a fruit juice color additive is hibiscus extract," says Penny Huck, associate director, technical service, Warner-Jenkinson, St. Louis. "Hibiscus extracts typically have very poor color stability and are typically suited for tea-based beverages, where more of a brown-red shade is desirable."
The FDA also allows the use of fruit juice as a color additive (21 CFR Sec. 73.250). According to the regulations, fruit juices used as color additives must be expressed from mature varieties of fresh, edible fruits, or they can be a water infusion of dried fruit.
"Most fruit juices are concentrated for Brix and not for color value," warns Huck. "Therefore, each drum that a manufacturer would use may have a different color strength. Typically, food manufacturers want a color-standardized fruit juice."
Specific shade requirements and the limits on available red colorants suitable for low pH systems have led to increased interest in the potential of anthocyanins as food colorants. Most fruit juice colorants are anthocyanin-based. Anthocyanins are a class of naturally occurring, water-soluble pigments frequently found in the plant kingdom. These chemicals are responsible for the color of grapes, cherries and berries, as well as other fruits and flowers. Their hue can be red, purple or blue, depending on their chemical structure. The shade changes with a change in the pH. High concentrations appear in chokeberries, bilberries, elderberries and cranberries, so these fruits and their derivatives can provide color to food products.
"Anthocyanins are red and most stable at a pH below 3.8," says Huck. "If you increase the pH, they shift toward purple and blue and are less stable. If you put them in a highly alkaline system they would actually be green. But they are not stable under neutral or alkaline conditions."
The consumption of anthocyanins also has been linked to a number of health benefits, including the prevention of atherosclerosis and cancer. They also reportedly exhibit bacteriostatic activity.
Although fruit-based colorants contain anthocyanins, their strength is not specified in terms of anthocyanin content, according to Huck. Instead, spectrophotometric techniques determine color strength. Solutions are buffered to pH 3, and the strength is calculated based on absorbance of an appropriate dilution and then converted to color strength of a 1% solution. (A 1% level would be difficult to measure using the spectrophotometer.)
According to Ed Race, director of research, Canandaigua Concentrates and Colors, Madera, CA, grape juice colorants can replace artificial colors in many products. Carmine, a purple color derived from insects, is not kosher. However, natural grape juice colorants are all kosher and could be used to provide shades similar to carmine for use in beverages, fruit bases and other foods.
Grape juice colorants come in a variety of colors: red (shades of cherry, raspberry or strawberry), purple and yellow. Their optimum pH is between 2.0 and 4.0. The typical usage level of Canandaigua's products is 0.5% or less. At this low concentration, only color and not flavor is contributed. The grape juice concentrates also have residual sulfur dioxide levels of less than 1 ppm.
Race points out that grape juice colorants would be considered grape juice for labeling purposes in a mixture of juices. However, if grape juice colors were used as the sole colorant, such as in pink lemonade, the label declaration would read, "colored with grape juice concentrate."
Like most other natural colors, there are certain conditions in foods where anthocyanins function best. The use of these pigments can be limited by their pH stability and their susceptibility to degradation by heat, light and ascorbic acid. According to Ginny Bank, product development leader at Hauser Food Ingredients, Boulder, CO, Hauser's ColorEnhance™, added as a diluent to these natural colors, helps overcome their traditional limitations.
ColorEnhance is a water-soluble extract of rosemary leaves, Rosmarinus officinalis L., that "can significantly improve the stability and enhance the color of anthocyanin-based natural pigments," says Bank. Because the colors will now appear more intense and their rate of degradation will be decreased, lower usage levels can be used and the product's shelf life can be extended.
The product is kosher, natural-certified, and considered GRAS by the FDA for its intended use under 21 CFR 0182.20. For most applications, levels of between 0.05% and 0.25% of total volume are recommended, providing a mild tea-like flavor. The flavor and aroma of the product will vary somewhat depending on the usage level and application.
Amazin' raisinsBecause fruits consist of a complex mixture of compounds, they can provide a number of different functions to the food products that contain them. The choice of a fruit product in a specific application is often dictated by all the effects it creates.
Raisins are a good example. A grape becomes a raisin when its moisture content drops below 16%. Raisins can function as an intense natural sweetener with a sugar:acid ratio of approximately 40:1. They contain a number of important vitamins and minerals, as well as dietary fiber. Raisins are low in calories (300 kcal/100 grams). At a moisture level of about 14%, California raisins have a water activity of 0.51. Raisins contain tartaric acid (about 2%), which contributes a sweet/tart flavor to foods.
The reducing sugars in raisins undergo a Maillard browning reaction with proteins during heating. More than 50% of the total reducing sugars are present as fructose which, being naturally hygroscopic, helps prolong the shelf life of breads and bakery products. These characteristics make raisins a versatile fat replacer.
Raisin juice is produced by combining raisins with water. The juice is subsequently evaporated under vacuum to a final, shelf-stable concentration of 70 Brix. Raisin juice concentrate contains propionic acid (500 to 600 ppm), a natural mold inhibitor, and has been shown to retard mold growth in bakery products.
Raisin paste functions well as a natural colorant and is an excellent fat replacer in sweet baked goods, according to Marjaneh Ravai, food scientist at Thomas J. Payne Market Development, Burlingame, CA. It is made from choice raisins by extrusion through a fine mesh screen. Afterward, a mild heat treatment produces a smooth and consistent puree. Raisin paste imparts a distinct but pleasant sweet taste and a rich caramel color. It is especially useful for barbecue sauces and salsas and in dark-colored beverages such as chocolate dairy drinks.
Finding a dateDates, another functional fruit, exhibit a multitude of characteristics. They can be pureed to form a paste, or they can be added to foods as chopped pieces. They are low in calories (248 kcal/100 grams) and are fat free. Dates are an excellent source of dietary fiber (9 grams/100 grams). They are high in complex carbohydrates, and they provide several important B vitamins and minerals, such as calcium, phosphorous and iron.
Carole Brownell, marketing director for the California Date Commission, Indio, CA, says that California dates present an attractive nutritional package to consumers, and they have value-added potential for food processors. Dates contribute a naturally sweet, caramel flavor and a rich creamy texture to a wide range of food products such as cookie fillings, snack bars, baked goods and confections.
Dates work well alone in dense products such as brownies or snack bars. They can be added to doughs and batters without reformulating leavening systems due to their low acid content (pH about 5.5). Like raisins, dates possess hygroscopic properties that prolong shelf life.
Plum good ideasDried plum puree is an effective fat replacer due to its high concentrations of sorbitol, pectin and malic acid. It can be used in dense products such as brownies and cake frostings.
Scott Sanders, Ph.D., former consultant for the California Prune Board and president, Creative Food Consultants in Byron, CA, notes that dried plums successfully reduce shortening and refined sugars and replace emulsifiers, caramel color and preservatives such as calcium propionate in bakery products. Salt can be reduced due to the flavor enhancement provided by malic acid. Dried plums contain about 2% malic acid naturally. This organic acid helps inhibit microbial spoilage, and it also can act as the acid component of chemical leavening systems.
Research has shown that prune or raisin juice concentrates, when used at between 4% and 6%, will inhibit mold formation in breads, according to Sanders. He points out that a shorter, simpler ingredient statement, no artificial preservatives, and a lower fat and sodium content provide an edge over the competition in the variety and natural breads markets.
Sometimes a combination of ingredients is synergistic and performs better at reducing or eliminating fat than if the ingredients were used individually, says Martin Silge, director of ingredient sales and marketing for Mariani Packing Co. Inc., Fremont, CA.
Blending plums with other fruits -- such as apples, dates and grapes -- adjusts the moisture-retaining capabilities, color and flavor. Dark-colored fruit ingredients are only suitable for the formulation of dark-colored products. With a fruit blend, the fat can be replaced in a cookie without greatly changing its color, for instance. According to Silge, other combinations of light-colored fruits such as dried pears and golden raisins can lend themselves well in the preparation of white cakes.
Not just for ThanksgivingCranberries are another fruit that provides several value-added ingredients. They have a unique sweet-tart taste that enhances the flavor profile of foods. Cranberries can be used in sauces and poultry glazes, vinaigrettes, sorbets and alcoholic beverages.
Cranberries can take on many forms, according to Martin Starr, director of application sciences at Ocean Spray Cranberries Inc., Middleboro, MA. Currently under development is a scarlet-colored presscake powder made from cranberry skins. It provides an inexpensive source of fiber, flavor and color to baked goods, cereals and granola bars. The dried powder also can be made into a bright red paste for use as a cookie or bakery filling. Spray-dried pink cranberry powder can be used as a natural colorant to provide a pleasant red hue to drink mixes and icings.
Cranberry and other fruit pieces are available in a range of water activities, enabling them to be used in a variety of foods without problems such as moisture migration. The pieces can be used in trail mixes, baked goods and cereals. Starr notes that the moisture, tartness and particle size can be varied depending on the application.
Nibbles 'n' bitsFruit bits or pieces can be prepared by sugar-infusing whole fruit or by pureeing fruit and restructuring it using gelling agents. Sugar infusion involves soaking fruit in a concentrated sugar solution, usually as high as 70 Brix. Through osmosis, where the solvent passes from a dilute solution into a more concentrated one, the water molecules will migrate out of the fruit and the sugar molecules will diffuse from the solution into the flesh of the fruit. The result will be a shelf-stable piece of fruit with a low moisture content and a low Aw.
Mild heat and/or vacuum speeds the infusion process, but care must be taken to ensure the flesh of the fruits are not damaged. Several sugars -- including fructose, glucose or sucrose -- can be used for infusion. Fructose is an excellent humectant, and it is the sweetest sugar of the three. Sucrose increases solids but is not considered a humectant. All three produce shelf-stable, easy-to-handle products using a minimum of additives. A more moist and chewy product would be desired for a bagel or a muffin, while a drier fruit would be more suited for a dehydrated hot cereal mix.
Fruit that has already been sugar-infused and dried also can then be steeped in glycerin, a sweet polyol, until the fruit soaks up from 2% to 5%. Although glycerin can make the fruit softer and extend the shelf life by retaining moisture, it is expensive and sometimes leaves a bitter aftertaste.
Restructured fruit bits are the mainstay of Jasper Wyman & Son, Milbridge, ME. According to Fred Robinson, director of R&D, the company was recently granted a patent for its novel method of producing shelf-stable dried fruit pieces, known as Crafted Fruit™, which retain their natural flavors. This new process is much more efficient and precise than the older technique of sugar infusion. The size and texture of the final product are more uniform and free from seed grittiness.
The process involves mixing pureed fruit with a natural sweetener such as fructose, also a good humectant. A natural gelling system is added to form the pieces, which are extruded and then air-dried. Finally, dusting them with flour or dextrose dries the surface.
Dehydrated fruit bits are available in a range of low water activities, usually 0.3 to 0.6. They can be added to cereals, or they can provide a burst of sweetness in baked goods and frozen desserts such as ice cream and fruit sorbets.
Unique applicationsFruit can be used to extend or replace tomatoes when tomato flavor or color is not desired. Mariani has developed sauce bases that contain either dried plums, apricots, raisins or dates. These fruits act as extenders for more expensive tropical fruits in products such as sweet-and-sour sauces, marinades, ethnic sauces, or dips. Apricots, for example, provide a sweet, tangy flavor, and very bright orange color.
"Fruit-based salsas, featured at this year's IFT in New Orleans, were very well received. There is tremendous growth potential for this category in the years ahead," says Song. "Consumers are more willing today to try exotic flavors such as mango and passionfruit, and they are discovering a whole new sweet taste sensation from these tropical fruits."
The stabilizing system must be selected very carefully when formulating these low-pH products. If starch is used, it could undergo acid hydrolysis and lose its functionality. It may be better to add the juice concentrates after the starch has fully gelatinized.
With the popularity and consumer demand for all natural fruit-based ingredients steadily growing, more food processors are realizing that it is a very good idea to include more of them in their product lines. Food product designers will be busy in the coming years improving their understanding and developing more uses for these wonderful ingredients.
Stuart Cantor is an East Coast-based technical writer with a master's degree in food science and six years of experience in designing low-fat products for the food industry.
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