RESTITUCIÓN DE DERECHOS
2. PROTECCIÓN DEL DERECHO A LA IDENTIDAD
CONTENTS
Introduction ...63 Types of Soy Ingredients in Baking...64 Functions of Soy Ingredients in Baking ...65 Solubility ... 66 Emulsification...68 Foaming...68 Gelation ...69 Water-Binding Capacity...69 Water-Holding Capacity...69 Color Control ...70 Health Benefits of Soy Ingredients in Baking ... 70 Applications of Soy Ingredients in Baking...71 Nutritional Enhancement of Cereals...71 White Breads, Buns, and Rolls ...74 Variety and Specialty Breads...75 Cakes and Pastry Products ...76 Donuts ...77 Cookies, Biscuits, and Sweet Pastry ...77 Special Applications ... 78 Summary ...79 References ...79
Introduction
Bread is the staff of life, and it has been the cause of wars, peace, and revolutions throughout history. Dr. Norman Borlaug, Nobel Peace Price recipient in 1970, said, “If you desire peace, cultivate justice, but at the same
64 Soy Applications in Food time, cultivate the fields to produce more bread; otherwise, there will be no peace.” Bread is eaten with every meal by every ethnic and age group every
day of the year, regardless of economic level.1 Over the last few decades,
research in the area of baking technology has evolved according to the nutritional concerns, applications of new or improved techniques, and con-
sumer trends at the time.2 These trends have led us to use soy ingredients
extensively in baking. Soybeans have been used as human food for nearly 5000 years, and the first soy protein food ingredients were soy flours, used primarily in breads and other bakery products in the United States in the 1940s. Since then, because of their excellent functional and nutritional char- acteristics, soy ingredients have been used in baking at an increasing rate due to the U.S. Food and Drug Administration’s approval in 1999 of the health claim that the consumption of soy protein can reduce the risk of coronary heart diseases. This chapter discusses the utilization of soy ingre- dients in baking, emphasizing the types of soy ingredients, the functions of these soy ingredients, and the application of soy ingredients in bakery prod-
ucts. Because the term baking does not apply only to the production of bread,
the chapter covers not only bread and variety breads but also cakes, pastries, cookies, biscuits, donuts, and special applications.
Types of Soy Ingredients in Baking
Soy ingredients that have unique functional and nutritional properties have found wide application in bakery products. These soy ingredients include soy flours, soy grits, soy protein concentrates, soy protein isolates, textured soy protein, soy brans, and soy germs. Soy flour can be defined as flour produced from soybean seeds that have been hulled and are then ground into a fine granulation. Soy flours can also be classified as defatted soy flour, enzyme-active soy flour, low-fat soy flour, high-fat soy flour, full-fat soy flour, and lecithinated soy flour. Defatted soy flour is a finely granulated product obtained by grinding hulled soybeans after oil extraction. Enzyme- active soy flour is a flour produced from defatted soybeans that have been processed in such a manner as to preserve the activity of the enzyme lipoxi- dase (lipoxygenase). Full-fat soy flour is obtained from hulled soybeans and retains all of the original fat content of the soybean. Lecithinated soy flour is soybean flour for which the normal lecithin content of 0.5 to 1.5% has been
augmented to 15% in order to increase its emulsifying properties.3 Soy grits
are identical to soy flours, the only difference being a larger particle size; they are used to enhance the nutritional and textural quality of cookies,
crackers, and specialty breads.4 Soy protein concentrate is a protein produced
by the extraction of sugars, soluble carbohydrate material, mineral matter,
and other minor constituents from defatted soy flour.3 Obtaining higher
protein fortification levels is generally the only reason to use soy protein
Soy Ingredients in Baking 65
concentrates in bakery products; nutritionally and functionally, soy flours do
the same job more economically.5 Soy protein isolates are proteins separated
from soybeans by various methods and often modified chemically or enzy- matically to impart certain desirable functional properties. Soy bran is pro-
duced by toasting and grinding the seed coat portion of the soybean.3,6 Soy
germ, which comprises only 2% of the total soybean, can be used in baked and extruded products and is widely used in cereal-based products as an adjunct to other soy ingredients to increase overall isoflavone levels. Because of the relatively high proportion of isoflavones found within soy germ, inclu-
sion rates are typically 1 to 2% of the total formulation of the product.7
Recently, the first soy flour to be recognized as whole grain, according to the definition of the American Association of Cereal Chemists (AACC) for whole grains, was introduced in the United States. The new whole-grain soy flour features 80% more dietary fiber than whole wheat and can be used at inclusion levels that support claims of the product being a “good source” or
“excellent source” of FDA protein and fiber.8 Table 4.1 provides the compo-
sition of soy ingredients used in bakery products. Soy protein products
(SPPs) are also covered by a Codex General Standard.9 According to the
standard, soy protein products must conform to the essential compositional requirements shown in Table 4.2.
Functions of Soy Ingredients in Baking
The functional properties of proteins are a result of their physicochemical properties and their interactions with other food components. Functional properties are important not only in determining the quality of the final
TABLE 4.1
Proximate Composition of Some Soy Ingredients per 100-g Edible Portion
Ingredient Moisture (g) Protein (N ×××× 6.25) (g) Total Lipids (Fat) (g) Total Dietary Fiber (g) Ash (g) Soy flour: Defatted 7.25 51.46 1.22 15.5 6.15 Low-fat 2.70 50.93 6.70 10.2 6.09 Full-fat 5.16 37.80 20.65 9.6 4.46
Soy protein concentrate (by acid wash)
5.80 63.63 0.46 5.5 4.70
Soy protein isolate (potassium type)
4.98 88.32 0.53 2.0 3.58
Source: USDA National Nutrient Database for Standard Reference, Release 17, Nutrient
Data Laboratory (http://www.nal.usda.gov/fnic/foodcomp/search/). 2981_C004.fm Page 65 Wednesday, September 28, 2005 12:50 PM
66 Soy Applications in Food
product but also in facilitating processing (e.g., improved machinability of cookie dough). In order to utilize soy ingredients effectively, food processors should have detailed information regarding the methods of preparation and processing of the soy products they are using because these affect the com-
position and functional properties of the component proteins.10 Although
soy ingredients have many functional properties in food systems, only the effects of soy protein preparations in bakery products are addressed in this chapter (Table 4.3).
Solubility
Solubility is one of the most basic physical properties of proteins and a prime requirement for any functional application. To obtain optimum functionality in uses where gelation, solubility, emulsifying activity, foaming, and lipoxy- genase activity are required, a highly soluble protein is required. Soluble protein preparations are also easier to incorporate into foods. Proteins with low solubility indices have limited functional properties and more limited uses. The solubility of soy protein is also significantly affected by the method used for its production. The extent of heat treatment during processing determines the use of soy proteins in bakery products (Table 4.4). Heat treatment, especially moist heat, rapidly insolubilizes soy proteins; however, heat treatment is necessary to desolventize, to inactivate antinutrient com- pounds, and to improve the flavor of soy flours. Nonheated soy flours, while possessing high lipoxygenase activity, have a bitter, beany flavor and limited applications. To balance enzyme activity, flavor quality, and solubility crite- ria, processors produce defatted soy flours with a range of solubilities. Con- centrates and isolates are prepared from minimally heat-treated flours and generally possess good solubility.
Protein solubility is a measure of the percentage of total protein that is soluble in water under controlled conditions and is a measure of the degree of heat treatment to which the soy flake has been subjected. The protein solubility is closely related to the functional properties for bakery food
TABLE 4.2
Codex General Standard for Soy Protein Products
Component
Soy Protein Flour (% dry weight basis)
Soy Protein Concentrate (%) Soy Protein Isolate (%) Moisture (maximum) 10 10 10 Crude protein (N× 6.25) 50 to <60 65 to <90 90 Ash (maximum) 8 8 8
Crude fiber (maximum) 5 6 0.5
Source: CAC, Codex General Standard for Soy Protein Products, Codex Standard 175- 1989, Codex Alimentarius Commission, Rome.
Soy Ingredients in Baking 67
TABLE 4.3 Selected Functional Characteristics of Soy Pr
otein in Baking Systems
Functional Property
Mode of Action
Baking System
Protein Form Used
Emulsification Formation
Formation and stabilization of fat emulsions
Br eads, cakes Flour , concentrates, isolates
Fat Adsorption Prevention
Binding of fr ee fat Donuts, pancakes Flour , concentrates W
ater Absorption and Binding
Uptake
Hydr
ogen bonding of water
, entrapment of water , no drip Br eads, cakes Flour , concentrates Retention Hydr
ogen bonding of water
, entrapment of water , no drip Br eads, cakes Flour , concentrates Dough formation — Baked goods Flour , concentrates, Isolates Cohesion–adhesion Pr
otein acts as adhesive material
Baked goods
Flour
, concentrates,
isolates
Elasticity
Disulfide links in deformable gels
Baked goods Flour , isolates Flavor -binding Adsorption, entrapment, r elease Baked goods
Concentrates, isolates, hydr
olyzes
Foaming
Forms stable films to trap gas
Whipped
toppings,
chif
fon
desserts, angel cakes
Isolates, soy whey
, hydr olyzes Color Contr ol Bleaching Bleaching of lipoxygenase Br eads Flour Br owning Maillar d, caramelization Br
eads, pancakes, waf
fles Flour Sour ce: Adapted fr om Kinselle, J.E., J. AOCS , 56, 242, 1979; Stauf fer , C.,
Milling & Baking News
, January 23, 2001.
68 Soy Applications in Food
applications. Several methods are used to determine protein solubility: nitrogen solubility index (NSI), the protein dispersibility index (PDI), and the protein solubility index (PSI). Each of these tests indicates the percentage
of total soluble nitrogen in water, with a range of values from 0 to 100.6 The
PDI decreases with higher levels of heat treatment. The more dispersible types of soy flours (high NSI or PDI) are used in bakery and cereal products
and are added directly to the dough.4 Enzyme-active soy flour has a mini-
mum water solubility of 70%.11 Soy flours subjected to minimal heat treat-
ment (PDI 80) show high lipoxygenase activity and are used at 0.5% to bleach flour and improve the flavor of bread. Flours with a PDI of approx- imately 60 are most commonly used (1 to 2% in bread, 10% in waffles and pancakes), as they markedly improve the water-binding capacity of these
products (Table 4.4).10,12
Emulsification
The ability of protein to aid in the formation and stabilization of emulsions is critical for many food applications, including cake batters. In general, the emulsifying capacity of soy protein products increases with increasing sol- ubility. Accordingly, soy proteins progressively reduce interfacial tension as
concentration is increased.10,12
Foaming
Foaming, the capacity of proteins to form stable foams with gas by forming impervious protein films, is an important property in some food applica- tions, including angel and sponge cakes. Soy protein exhibits foaming prop- erties closely correlated to its solubility. Studies have revealed differences in the foaming properties of various soy protein products, and soy isolates are
superior to soy flours and concentrates.10,12
TABLE 4.4
Soy Protein Solubility Requirement for Selected Bakery Applications Application Protein Dispersibility Index (PDI) Emulsifying, foaming >90
Lipoxygenase bleaching of flour and bread >85
Water absorption in bakery products 60
Waffles 30
Crackers, cereals 15
Source: Adapted from Kinselle, J.E., J. AOCS, 56, 242, 1979. 2981_C004.fm Page 68 Wednesday, September 28, 2005 12:50 PM
Soy Ingredients in Baking 69 Gelation
Protein gels are three-dimensional networks in which water is entrapped. Gels are characterized by a relatively high viscosity, plasticity, and elasticity. Whereas soy flour and concentrates form soft, fragile gels, soy isolates form firm, hard, resilient gels. Protein gelation is concentration dependent; a min- imum of 8% protein concentration is necessary for soy isolates to form a gel. The general procedure for producing soy protein gel involves heating the protein solution at 80 to 90°C for 30 minutes followed by cooling at 4°C. The ability of the gel structure to provide a matrix to hold water, fat, flavor, sugar,
and other food additives is very useful in a variety of food products.10,12
Water-Binding Capacity
Bound water includes all hydration water and some water loosely associ- ated with protein molecules following centrifugation. The amount of bound water generally ranges from 30 to 50 g/100 g protein. Soy isolate has the highest water-binding capacity (about 35 g/100 g) because it has the highest
protein content among soy protein products.12 Soy concentrates contain
polysaccharides, which absorb a significant amount of water. Processing conditions can affect the amount of water that can be absorbed. In fact, these conditions can be varied to influence how tightly the water is bound
by the protein in the finished food product.4 Soy proteins differ considerably
from wheat protein in their chemical composition as well as in their physical properties due to their total lack of elasticity. The addition of soy proteins to wheat flour thus dilutes the gluten proteins and starch. Soy proteins exhibit a strong binding power that provides some resistance to dough expansion, the effect being somewhat proportional to the level of soy flour employed. This can be partially overcome by increasing the amount of water used in dough making and by a longer proofing time. The binding power of soy flour is closely related to its high water absorption capacity, which, in the case of the defatted product, is equivalent to 110% by weight. Hence, soy flour will absorb an amount of water equal to its weight when mixed with wheat flour to normal dough consistency. With full-fat flour, however, no measurable increase in dough absorption results from normal use levels
of the soy product.13
Water-Holding Capacity
Water-holding capacity is a measure of entrapped water that includes both bound and hydrodynamic water. The literature reveals some variability in data regarding water-holding capacity which may have resulted from varia- tions in the methods of determination. The water-holding capacities of soy flour, concentrate, and isolate were reported as 2.6, 2.75, and 6.25 g/g of solids, respectively. Because heat treatment enhances this functional property, soy
70 Soy Applications in Food flours with PDIs of 15, 55, 70, and 85 had water-holding capacities of 209, 307, 308, and 207 g water per g flour, respectively. The water-holding capacity of protein is very important because it affects the texture, juiciness, and taste. Also, the ability of soy protein to bind and retain water enhances the shelf
life of bakery products.10,12 All soy protein concentrates, regardless of the
process used, do have certain fat- and water-holding characteristics.4
Color Control
Soy flour is rich in the enzyme lipoxygenase, which plays a major role in its bleaching action. Soy flour contains a type-1 (LOX-1) and a type-2 lipoxy- genase (LOX-2), and earlier studies have shown that purified LOX-2, but not LOX-1, bleaches flour pigments. Lipoxygenase oxidizes carotenoid and chlo- rophyll pigments in flour to their colorless form, a bleaching action that whitens flour and bread crumbs; however, because LOX-2 lipoxygenase also oxidizes fatty acids, achieving a whiter flour increases the risk of rancidity. For this reason, the amount of enzyme-active flour is restricted to approxi-
mately 1% flour weight.14–18
Health Benefits of Soy Ingredients in Baking
The health benefits of soybeans have been recognized for millennia. Soyfoods and their isoflavones appear to have clear protective effects related to coro- nary heart disease and probable protective and therapeutic effects related to osteoporosis. The effects on the kidneys are clear, and these protective effects are under study. While the greatest interest may lie in their chemopreventive effects related to cancer, much more research is required. The effects of soyfoods on cognitive function are unclear and also require further research. The use for menopausal symptoms appears promising, and postmenopausal women who cannot or choose not to take hormone replacement therapy may
be ideal candidates for daily soyfood use.19 It should also be mentioned here
that some concern has been raised with regard to allergies to soyfoods and soy-based infant formulas, as well as potential soybean antinutrients; how- ever, soy protein is ranked 11th in allergenicity, with 0.5% of young children having an allergy to soy. The incidence of soy protein allergy among older
children and adults is extremely rare.19 As mentioned earlier, the FDA’s
approval of a health claim based on the association between consumption of soy protein and a reduced risk of coronary heart disease has significantly increased the demand for soy ingredients by the food industry. The govern- ment-approved health claim adds legitimacy to soy protein products, has helped to increase the awareness of soyfoods, and has created an incentive for food processors to add soy protein to foods; consequently, the number
of soyfood products available has increased significantly.20
Soy Ingredients in Baking 71
Applications of Soy Ingredients in Baking
Soyfoods may be divided into four classes: soy ingredients, traditional soy- foods, second-generation soyfoods, and foods where soy is used as a func- tional ingredient. Soy ingredients include raw (or unprocessed) soybeans, soy flours (defatted and full-fat), soy concentrates, soy isolates, texturized vegetable soy protein, and hydrolyzed soy protein. Foods in which soy is used as a functional ingredient include baked goods to which soy flour is
added.21 Soy ingredients having unique nutritional and functional properties
have found wide application in bakery products. The effects of soy ingredi- ents in bakery products are summarized in Table 4.5, and bakery food appli- cations of soy ingredients are provided in Table 4.6.
Nutritional Enhancement of Cereals
In recognition of the many advantages of soy flour as a protein supplement, considerable effort has gone into blending soy flour with cereals. These mixtures, when suitably fortified with vitamins and minerals, have great potential for feeding people of all ages in developing areas of the world. In addition to their significant levels of high-quality protein, the calcium and phosphorus levels of soy ingredients are also considerably higher than those of any other cereal grain, and soy flour is an excellent source of available iron. Furthermore, soy flour is considerably richer in vitamins than unen-
riched patent wheat flour and somewhat richer than enriched white flour.13
During the 1950s and 1960s, nutritionists sought to increase the adequacy and amount of dietary protein in developing countries. Soy-fortified grain products were seen as one way to accomplish this, and much work was done on incorporating soy into bread and pasta. Soy protein is relatively rich in
TABLE 4.5
Effects of Soy Flour on Bakery Applications
Absorption facilitates greater water incorporation. Improves dough handling.
Improves machineability of cookie dough. Improves moisture retention during baking.
Improves cake tenderness, crumb structure, and texture. Enhances rate of crust color development.
Retards fat adsorption by donuts. Prolongs freshness and storage stability. Bleaches crumb color to produce white bread. Improves nutritional quality.
Functions much like nonfat dry milk in bread and rolls, at about half the cost. Source: Kinselle, J.E., J. AOCS, 56, 242, 1979. With permission.
72 Soy Applications in Food
TABLE 4.6 Bakery Food
Applications for Soy Ingr
edients
Ingredient
White Bread and Rolls Specialty Breads and Rolls
Cakes Cake Donuts Y east Donuts Sweet Goods Cookies and Biscuits
Defatted soy flour
XXXXXXX
Enzyme-active soy fl
our
X
Low-fat soy flour
X
X
X
High-fat soy flour
X
X
X
Full-fat soy flour
X X X Lecithinated soy fl