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Using Highly Expanded Citrus Fiber to Improve the Quality and Nutritional Properties of Food

August 2005     
Brock Lundberg, M.S., P.E. - Fiberstar, Inc. - Vice President of Technology

ABSTRACT
Although functional fibers including citrus fibers have been around for a long time, a unique highly expanded citrus fiber has been developed using patented technology. Due to the large quantity of applications and different types of fibers, using functional fibers can be a complex issue for food formulators. However, detailed formulation guidelines for using highly expanded citrus fiber in two key applications is given: 1) for use as an exceptional moisture management tool to control syneresis by tightly binding excess water and oil and 2) for use as a functional ingredient to replace fat. The key benefits of formulating with highly expanded citrus fiber is its ease of hydration and neutral impact on taste, texture, and cost in a formulation while improving nutrition and/or the quality of the finished food product.

Adding dietary and functional fibers to foods is relatively common. However, properly selecting and incorporating fibers into a food product formulation can still be a challenging issue, especially when a specific functional objective is desired. Many formulators add dietary fibers at rates of up to 10% to increase the dietary fiber content of foods. However, functional fibers are typically used at only relatively low usage levels to perform a specific function and then, only consequentially, to add dietary fiber. For example, functional fibers can be used as a moisture management tool, to thicken, as a gelling agent, for shelf life extension and fat reduction, among many others. Because they have been designed to perform a specific function in a formulation, there are often negative taste, texture, or cost issues associated with their use at higher levels of use. For these reasons, many functional fibers can only be used at low levels in a formula.

Citrus fiber based ingredients have been around as long as citrus fruits have been harvested. Although an orange contains 85% moisture, of the remaining dry matter, two thirds is soluble sugars and 13.3% is fiber (3). In the edible portion of an orange, the commonly eaten fibrous components are the juice sacs and segment membranes (8, 9). One of the more common edible uses of orange peel is in marmalade. The pulp in orange juice is another form of a citrus fiber ingredient that is used to provide a pulpy mouthfeel in orange juice and several other beverage applications. Citrus fibers have also been homogenized to provide synthetic clouding agents to give the same eye appearance and visual quality as naturally cloudy fruit juices (4). Other reports suggest using citrus juice cells to create a dried orange pulp that can be used to enhance mouthfeel in beverages and for thickeners and gelling agents (7).

Although Blake reports using orange juice cells for functional purposes in frostings and icings, he worked only with a pre-dried form of juice sacs and noted the difficulty in attaining a dried product that was as functional as the pre dried form (1). Several dried citrus fiber ingredients have been reported or produced for use as a nutritive fiber for various bakery items (5, 6). Today, there are several dried orange fibers being marketed with varying degrees of taste, aroma, and water holding capacities. Also, pectin, which is derived from citrus fiber, plays an important role in moisture binding or gelling properties in jams, jellies, beverages, dairy, and bakery products.

HIGHLY EXPANDED CITRUS FIBER
A relatively new form of citrus fiber ingredient, referred to as highly expanded citrus fiber, was introduced within the past couple years and has been shown to be effective at binding large amounts of water to improve both product quality and nutrition in a wide variety of foods. The composition of the highly expanded citrus fiber is roughly 70% total dietary fiber and of that, roughly half is soluble fiber and the other half is insoluble. This citrus fiber is also low fat at roughly 1% total fat and contains no trans fatty acids. The typical analytical composition of the highly expanded citrus fiber is shown in the Table 1. Highly expanded citrus fiber is also neutral in terms of taste, odor, and color and is non GMO and considered a non allergen. Additionally, because of the way it is processed, the highly expanded citrus fiber does not need to be sheared in water in order to open up the cell structure before incorporation into the ingredient mix. Rather, the fiber will expand and hydrate by itself once it is exposed to water, which is a notable property for any hydrophilic ingredient.

Due to the large increase in the internal surface area, the water holding capacity of highly expanded citrus fiber and its viscosity in water is substantially higher compared to other common fibers. For example, the water holding capacity of highly expanded citrus fiber is 9.95 ml water / g of fiber or nearly 5 times higher water holding capacity than the other two commonly used fibers, cellulose and oat fiber, which hold 2.78 and 2.32 ml water / g of fiber, respectively,. A comparison of the water holding capacity of two different highly expanded citrus fibers, one being pure citrus fiber and the other co-manufactured with guar gum, to other commonly used fibers is shown in Table 2.

Another important difference in functionality between the highly expanded citrus fibers and other commonly used fibers is that the expanded citrus fibers not only have a high water holding capacity but they also bind the water very tightly. This functionality imparts two very important functional benefits. When water is bound this tightly, there is reduced bake off moisture during a baking or frying process and water activity levels can be maintained when added to a food product. This results in a food product having a similar water activity level even though it may have a higher moisture content as compared to a control formula. Additionally, because the water is so tightly bound, the highly expanded citrus fiber entraps the moisture and holds it in place, including in frozen foods, so that a more uniform product moistness can be maintained even over an extended period of time.

Because functional fibers are generally used at low levels, health benefits are derived from a reduction in the calories or fat content of the ingredients they replace such as fats and oils. One of the unique features of using a functional fiber such as highly expanded citrus fiber for fat replacement is that it enables food manufacturers to accomplish the removal of trans fatty fat without increasing the level of saturated fat while continuing to maintain the same great taste as the full fat version but at a lower cost.

When highly expanded citrus fiber is put into a solution, it will generate a significant amount of viscosity. However, the expanded citrus fiber does not dissolve so it does not form a clear solution but rather generates viscosity as a result of the high degree of hydrogen bonding with water. This viscosity can be used to thicken beverage or other types of water based formulas. Because the expanded citrus fiber has a pseudoplastic rheology curve, meaning it will act less viscous with more shear, it does not have a slimy mouthfeel even at high usage levels.

If increased viscosity is not desired, additional water is added along with the expanded citrus fiber, resulting in being able to maintain or reduce the cost of many formulations. The typical water usage level depends on the specific formulation but varies from 4 – 7 parts of added water per part of expanded citrus fiber used.

REDUCING SYNERESIS
A well suited application for highly expanded citrus fibers is for syneresis control to reduce the amount of free oil or water in a product. Many benefits result from the addition of highly expanded citrus fiber; not only is the water bound resulting in less separation, but typically there is a less oily appearance and more bulk even with a similar Bostwick consistency. The consistency is maintained in the product by adjusting the amount of additional water used in the formulation. Because of the high surface area of the fiber, there are bonding sites for oil to adsorb to the fiber as well, which results in the highly expanded citrus fiber having favorable emulsification properties compared to other fiber ingredients. With improved emulsification, there is typically less separation during processing, which can result in increased processing yields.

The data shown in the Figure 1 is one example of the free water and oil that becomes bound even with the small addition of highly expanded citrus fiber in a filling, which in this case is in an egg roll filling. As the data in Figure 1 show, there is a dramatic improvement in yield, even at the low percentage of use. The amount of free water/oil is reduced from 18.5% in the control to 7% with the addition of only 0.5% of expanded citrus fiber. At usage levels of 1%, the amount of free water/oil is reduced to 2%. This functionality applies to a wide variety of applications, notably any type of wrapped or sauce type products, such as burrito fillings, egg rolls, won ton wraps, chicken wraps, and pizza, among many others.

FAT REPLACEMENT
Because of the moisture entrapping properties and smooth mouth feel of highly expanded citrus fibers, they are effective at mimicking fat without imparting the negative effects on the taste, color, volume, or texture often associated with reduced fat products. Additionally, because highly expanded citrus fiber is able to tightly bind such a large amount of added water, formulations are typically cost neutral or result in an overall cost reduction as compared to the cost of a full fat formula. The use of highly expanded citrus fibers to replace up to 50% of the fat in most formulations offers a non fat solution for fat reduction.

Table 3 shows an example formulation for both a control and reduced fat muffin. This formulation uses a fairly standardized method of reducing the fat or oil when using highly expanded citrus fiber. Highly expanded citrus fiber replaces 1/8th of the amount of oil or shortening that is removed and water replaces the remaining 7/8ths of the amount of oil or shortening that is removed. In this example, 50% of the oil was replaced with the expanded citrus fiber and water. Because of the large amount of water bound by the expanded citrus fiber,, the total ingredient cost for the reduced fat product is actually 2-3% less than the full fat control. The reduced fat muffins were noted to have very similar volume and eating qualities to those of the full fat muffins so that it would be difficult for a person to distinguish one from the other. Table 4 shows the nutritional information for the control and reduced fat muffins, which was calculated using Genesis software. The total fat content of the muffin was reduced by 38% and the saturated fat was reduced by 28%. Additionally, although small, the total dietary fiber content of the reduced fat muffin was increased by 100%.

The control and reduced fat muffins made according the formulas shown in Table 3 have very similar volume, texture, shelf life, and water activity to each other. The specific volume of both the control and reduced fat muffins were measured to be 0.45 g / cc. A photo of each muffin is shown in Figure 2. The muffins were also similar in terms of their taste, grain, and texture over an extended period of time. The texture or hardness of the control and reduced fat muffin was monitored over a two week time period using a texture analyzer (TA-TX2). This data is shown in Figure 3. The hardness data show that the control and reduced fat muffins are near identical to each other in terms of their texture over a two week period of time. This illustrates the ability of the expanded citrus fiber to entrap water so that the finished food product does not dry out or harden over time but actually has near identical eating properties to those of the full fat control.

In addition to having similar texture, the water activity of both the control and reduced fat muffin were found to be near identical to each other as shown in Figure 4. Because the water activities of these two muffins were so similar, no mold growth was noted even beyond the two week shelf life of the muffins.


CONCLUSIONS
Highly expanded citrus fiber provides opportunities for food formulators to improve the nutrition and/or quality of a product without adversely affecting a product’s taste or formula costs. Although more research is being conducted in new areas, two key applications for the use of expanded citrus fiber have emerged: 1) as a moisture management tool to reduce syneresis, add or bind additional water to increase product moistness, retard moisture migration to achieve more uniform moisture distribution and to reduce ice crystal formation during storage and 2) as a relatively simple solution to improve the nutrition of a food product through the replacement of up to 50% of the fat or oil in a food product without negatively affecting its taste, texture, water activity, or cost as compared to the control

REFERENCES
1. Blake, J.R. Citrus Juice Vesicle Containing Frosting Compositions and Method of Preparation. U.S. Patent No. 4,232,049, 1980.

2. Braddock, R.J. Utilization of Citrus Juice Vesicle and Peel Fiber. Food Technology. December. pp85-86, 1983.

3. Braddock, R. J. Handbook of Citrus By-Products and Processing Technology. John Wiley & Sons, Inc. New York, NY, 1999.

4. Crandall, P.G., R.F. Matthews, and R.A. Baker. Citrus Beverage Clouding Agents – Review and Status. Food Technology. Dec., 1983.

5. Ficca, V. G., M. Grossman, and T. Rohman. Method of Making Citrus Fruit Peel Extracts and Flour. U.S. Patent No. 6,183,806, 2001.

6. Lynn, C. Citrus Fiber Additive Product and Process for Making the Same. U.S. Patent No. 4,225,628, 1980.

7. Passy, N., and C.H. Mannheim. The Dehydration, Shelf-life and Potential Uses of Citrus Pulps. Journal of Food Engineering. Vol 2, pp 19-34, 1983.

8. USDA. Chemistry and Technology of Citrus, Citrus Products, and Byproducts. Agriculture Handbook No. 98, 1962.

9. USDA. Composition of Foods. Fruits and fruit juices. Oranges. Agricultural Handbook 8-9, Washington, D.C., 1982.

Component   Results   Units
Calories (FBDG Subtracted)   217   Calories/100g
Total Fat   1.02   %
Saturated Fat   0.28   %
Trans Fat   0.00   %
Monounsaturated Fat   0.32   %
Cis-cis Polyunsaturated Fat   0.36   %
Carbohydrates, Total   81.3   %
Fiber, Total Dietary   70.8   %
Soluble Fiber   33.3   %
Insoluble Fiber   37.6   %
Protein by Dumas   8.17   %
Sodium   18.5   mg/100g
Moisture   6.78   %
Ash   2.68   %
Aerobic Plate Count   <10,000   CFU/g
E. coli   <10   CFU/g
Listeria monocytogenes   Negative per 25g    
Salmonella (Confirmed)   Negative per 25g    
Table I: Typical analytical composition of expanded citrus fiber.


 
WHC
3% Solids
Fiber
(ml water / g fiber)
Viscosity (cP)
Expanded citrus fiber & guar gum
13.35
2437
Expanded citrus fiber
9.95
567
Carrot Fiber
6.54
102
Orange Fiber
5.02
3.3
Wheat Bran
3.82
0
Cottonseed Fiber
3.13
0
Tomato Fiber
2.98
156
Cellulose
2.78
0
Beet Fiber
2.68
0
Soy Fiber
2.48
1
Oat Fiber
2.32
0
Microcrystalline cellulose
1.95
0
Resistant Starch (corn)
0.87
0
Resistant Starch (modified wheat)
0.68
0
Table II: Comparison water holding capacity tests as measured by AACC Standard Method #56-30 and 3% solids viscosity data of various fibers.


  Control Test
Ingredient Name Formula Formula
Cake muffin base 100 100
Eggs, whole 35 35
Oil, veg, pure 30 15
Water, municipal 22 22
Expanded citrus fiber 0 3
Blueberries, fresh, ea 30 30
Water, municipal

0 18
Table III: Example formulation of a control and reduced fat muffin using expanded citrus fiber.


Muffin Nutritionals per 100 g
50% reduced
Nutrients
Control
shortening
Units
Gram Weight
100
100
g
Calories
330
270
kcal
Protein
4
4
g
Carbohydrates
40
41
g
Dietary Fiber
1
2
g
Total Sugars
24
24
g
Fat
18
11
g
Saturated Fat
3
2
g
Trans Fatty Acid
0
0
g
Table IV: Nutritional information for the control and reduced fat muffins made using expanded citrus fiber and water to replace ½ the oil of the control.


Figure 1: An example of the amount of free water and oil expanded citrus fiber is able to bind in a filling or wrap. This particle data was taken on an egg roll filling.



Figure 2: Control (left) and reduced fat muffins (right) made following the formula shown in Table 3.



Figure 3: Hardness data as measured by a texture analyzer over a two week period of time for a control and reduced fat muffin where the 50% of the oil was replaced with expanded citrus fiber and water according the formulation shown in Table 3.



Figure 4: Water activity of the control and reduced fat muffin made according to the formulation shown in Table 3, measured over a two week time period.