Advances in formulating gluten-free products

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Advances in formulating gluten-free products: as awareness of gluten

intolerance and Celiac Disease grows, companies look to ingredients

and processes as tools to replace gluten, a structure-building

protein in products

BY Eimear Gallagher, Prepared Foods > June, 2005

Celiac Disease is a life-long intolerance to the gliadin fraction of

wheat and the prolamins of rye (secalins), barley (hordeins) and

possibly oats (avidins). The condition is the end result of three

processes: Genetic predisposition, environmental factors and

immunogically-based inflammation that culminate in intestinal

mucosal damage. Sufferers have small intestine inflammation that

leads to malabsorption of nutrients such as iron, folic acid,

calcium and fat-soluble vitamins. The only effective treatment is

strict adherence to a gluten-free diet throughout life, resulting in

mucosal recovery.

A gluten-free diet excludes foods made with wheat, rye, barley,

triticale, dinkel, kamut and oat flour as well as byproducts made

from those grains. Other excluded foods are those that use wheat-

and gluten-derivatives as thickeners and fillers, for example, hot

dogs, salad dressings, canned soups/dried soup mixes, processed

cheese and cream sauces.

Prevalence and Labeling

Epidemiological studies in 1950 first estimated relatively low

incidences of Celiac Disease. However, by the 1960s, more specific

tests became available and it is now possible to determine

accurately the true prevalence. While a biopsy remains the

definitive test, antigliadin antibody serological tests have

resulted in substantially increased diagnosis rates. Screening with

modern serological tests places incidence of Celiac Disease in the

U.S. at 1/111.

The iceberg model often is used to explain prevalence (See

chart " The Tip of the Iceberg " ). Properly diagnosed cases form a

small, visible tip while many more " silent " cases exist.

In 1976, the Codex Alimentarius Commission of the World Health

Organization (WHO, Geneva) and the Food and Agricultural

Organization (FAO, Rome) adopted The Codex Standard for gluten-free

foods. In 1981 and in 2000, draft-revised standards stated that so-

called " gluten-free foods " are described as: (a) consisting of, or

made only from ingredients which do not contain any prolamins from

wheat or all Triticum species such as spelt, kamut or durum wheat,

rye, barley, oats or their crossbred varieties with a gluten level

not exceeding 20ppm; or ( consisting of ingredients from wheat,

rye, barley, oats, spelt or their crossbred varieties, which have

been rendered gluten-free; with a gluten level not exceeding 200ppm;

or © any mixture of two ingredients as in (a) and ( mentioned

with a level not exceeding 200ppm.

In this context, the WHO/FAO standard gluten was defined as a

protein fraction from wheat, rye, barley, oats or their crossbred

varieties (e.g., Triticale) and derivatives thereof, to which some

persons are intolerant and that are insoluble in water and 0.5M

NaCl. Prolamins are defined as the fraction from gluten that can be

extracted by 40%-70% aqueous ethanol. The prolamin from wheat is

gliadin, from rye is secalin, from barley is hordein and from oats

is avenin. The prolamin content of gluten is generally taken as 50%.

However, there are discrepancies in labeling foods " gluten-free "

because the exact amount of prolamins that individuals with Celiac

Disease may consume without damaging the mucosa has not been

scientifically determined. It had been thought that the protein

component in wheat starch could be completely removed, but it is now

known that some protein will remain. In the U.S. and Canada, gluten-

free diets are devoid of any wheat starch, and are based on

naturally gluten-free ingredients such as rice.

Formulating Gluten-free, Cereal-based Products

On a dry matter basis, gluten contains 75%-86% protein (as glutenin

and gliadin fractions). The remainder is made up of carbohydrates

and lipids that are held strongly within the gluten-protein matrix.

Upon full hydration, glutenin is a rough, rubbery mass, while

gliadin produces a viscous, fluid mass. Gluten, therefore, exhibits

cohesive, elastic and viscous properties that combine the extremes

of the two components. The gluten matrix is a major determinant of

the important properties of dough (such as extensibility, resistance

to stretch, mixing tolerance and gas-holding ability), which

encloses the starch granules and fiber fragments.

Gluten can be termed the " structural " protein in bread. Its absence

often produces a liquid bread batter rather than dough. The final

baked bread may have a crumbling texture, poor color and other

quality defects. One researcher concluded that bread dough without

gluten could only retain gas if another gel replaces the gluten. In

pasta, gluten contributes to a strong protein network that prevents

product dissolution during cooking.

Additional difficulties occur when alternative gluten-free

ingredients are used, since modifications to traditional production

processes may be required. One exception is in the manufacture of

gluten-free cookies. The development of a gluten network in cookie

dough is minimal and undesirable (apart from certain semi-sweet

cookies, which may have a developed gluten system); the texture of

baked biscuits cookies is primarily attributable to starch

gelatinization and super-cooled sugar rather than a protein/starch

structure.

The formulation of gluten-free bakery products presents a formidable

challenge to both the cereal technologist and the baker. Recently,

there has been significantly more R & D on gluten-free products,

resulting in diverse approaches. These include the use of starches,

dairy products, gums and hydrocolloids, and other non-gluten

proteins and prebiotics as gluten alternatives to improve the

structure, mouthfeel, acceptability and shelflife of gluten-free

bakery products. Extensive R & D is ongoing at the authors'

laboratories at The National Food Centre (Dublin, Ireland) and at

University College (Cork, Ireland) in a joint project using

a " bioengineering " approach. This term describes the building of

texture in gluten-free, cereal-based products using a range of

ingredients.

Starches and Gums

Starches and hydrocolloids are widely used in baked goods to impart

texture and appearance properties. These are useful for gluten-free

products as well.

An early study published in 1954 on the role of starch in

breadmaking showed that breads could be prepared from starch and gel-

forming substances. Rice starches offer an option in that they do

not have gluten, have low levels of sodium and have high amounts of

easily digested carbohydrates, which are desirable for special

diets. However, the absence of gluten causes problems in

breadmaking. A 1997 study showed that many gum types including

hydroxypropylmethylcellulose (HPMC), locust bean, guar, carrageenan,

xanthan and agar successfully formed rice bread. HPMC gave optimum

volume expansion. A 2001 study found that 1.7% HPMC and 0.4%

carboxymethylcellulose (CMC), as gluten substitutes, contributed

better bread characteristics than 0.7% guar gum in a 50:50 wheat

flour/rice flour formulation. The researchers also concluded that

replacing 30% of the wheat flour with rice flour was the maximum

possible level for acceptable bread quality without the addition of

a gluten substitute, and brown rice flour was unsuitable for baking

rice bread. In another paper, researchers found that fine white and

ground rice flours gave good quality, gluten-free breads when used

in combination with 0.8% CMC and 3.3% HPMC.

Two papers published in 1996 investigated the use of different

binding agents (xanthan, guar gum, locust bean gum and tragant) as a

gluten substitute in gluten-free bread formulations based on

cornstarch. The binding agents resulted in a highly significant

increase in loaf volume and loosening of the crumb structure. The

highest quality, gluten-free bread contained xanthan gum at levels

of 1%-3%.

An early 1975 article discussed the application of soy protein in

the manufacture of gluten-free breads. The authors formulated wheat

starch-based gluten-free breads with 20%, 30% and 40% soy protein

isolate (containing 88% protein). The breads had more protein and

fat than wheat bread, and showed satisfactory baking

characteristics. The authors of a 2000 article on the production of

gluten-free breads and other baked goods in South America used

fermented cassava starches. By increasing the proofing time of

gluten-free bread dough (based on potato/corn/rice starches, pectin,

emulsifiers and lactose-free margarine), one author of a 1980

article obtained high-quality gluten-free yeast breads and

gingerbreads.

Gums and thickeners are used for a variety of purposes, including

gelling and thickening, water retention and texture improvement. A

study published in 1996 used combinations of guar gum and locust

bean gum to partially replace flour in bread. The use of guar gum

resulted in a crumb structure with a more even cell size

distribution, while locust bean gum inclusion increased bread loaf

height. Both gums retarded bread staling. Optimum levels for locust

bean gum and guar gum were 2%-4%.

A study published in 2002--whose authors included two from this

article--investigated the application of novel rice starches

(manufactured with low to high degrees of starch hydrolysis) on a

replacement basis for wheat starch in gluten-free bread

formulations. The inclusion of the rice starches at 3%-9% levels

resulted in gluten-free loaves with less yellow crumb appearance

(Minolta b* value), and darker crust colour (Minolta L*). Crust

hardness was unaffected, but crumb hardness (measured by Texture

Profile Analysis) was reduced, as was the rate of staling. The

optimum level for rice starch inclusion was 6%; this also doubled

the dietary fiber content of the loaves. Extensive tests also are

being carried out at University College (Cork, Ireland) on the

formulation of gluten-free loaves based on corn, potato, buckwheat,

with blends of gums and dairy ingredients.

Dietary Fiber

Dietary fiber's role in contributing to a healthy intestine has long

been recognized. Since gluten-free products generally are not

enriched or fortified and frequently are made from refined flour or

starch, they may not contain the same nutrient level as the gluten-

containing counterparts they are replacing. Celiac patients living

on gluten-free products may not be ensured a nutritionally balanced

diet. In one recent study, researchers screened the intake of

nutrients of 49 adults diagnosed with Celiac Disease that were

following a gluten-free diet. They were found to have a lower intake

of fiber compared to a control group of people on a normal diet.

Several research studies, including one on celiac adolescents,

concluded that adherence to a strict gluten-free diet worsens the

already nutritionally unbalanced diet of adolescents (their dietary

levels of nutrients and fiber were found to be low).

Enriching gluten-free baked products with dietary fibers is an

interesting topic of research. Inulin acts as a prebiotic by

stimulating the growth of " healthy " bacteria in the colon. When

added to wheat bread, it improves loaf volume and slice-ability,

increases dough stability and produces a uniform and finely grained

crumb texture. Two authors of this article incorporated inulin (8%

inclusion level) into a wheat starch-based, gluten-free formulation.

The bread's dietary fiber content increased from 1.4% (control) to

7.5% (control with added inulin), and crust color also was enhanced.

The latter was due to the enzymes in the yeast hydrolyzing part of

the inulin, resulting in the formation of fructose and causing crust

browning.

In a study published in 2002, amaranthus flour replaced cornstarch

to enhance the protein and fiber contents of gluten-free breads. At

a 10% replacement level, protein and fiber levels increased by 32%

and 152% respectively, while sensory quality was unaffected. Another

2002 paper discussed the application of quinoa as a novel

application in the production of enriched, gluten-free bakery goods.

An older 1996 article described the use of amaranth in gluten-free

products. The researchers formulated a gluten-free mix using

wholemeal amaranthus flour. Both quinoa and amaranth

are " pseudocereals " that have a high nutritional value. One study

looked at both quinoa and amaranth as a 40% replacement for wheat

flour in a yeast bread formulation. The bread quality (loaf volume

and crumb softness) and nutritional aspects, including dietary fiber

content, were improved when the dough moisture was increased to 65%.

Dairy Ingredients

Dairy proteins may be used in bakery products for both nutritional

and functional benefits--including flavor and texture enhancement,

and storage improvement. Dairy products may be used in gluten-free

bread formulas to increase water absorption and, therefore, enhance

the handling properties of the batter. However, supplementation of

gluten-free breads with high lactose-content powders is not suitable

for celiacs who have significant damage to their intestinal villi;

they may be intolerant to lactose due to the absence of the lactase

enzyme, which is generated by the villi.

In a study published in 2003, the authors of this article applied

seven dairy powders to a gluten-free bread formulation. In general,

the powders with a high-protein/low-lactose content (sodium

caseinate, milk protein isolate) gave breads an improved overall

shape and volume, and a firmer crumb texture. (See chart " Dairy

Proteins and Loaf Volume. " ) The breads had an appealing dark crust

and white crumb appearance, and received good acceptability scores

in sensory tests. When optimal water was added to the gluten-free

formulation, the breads exhibited increased volume and a much softer

crust and crumb texture than the controls. Supplementing the gluten-

free formulation with high protein-content dairy powders doubled the

protein content of the breads.

Other Tools

One statistical tool, response surface methodology (RSM), is

particularly useful for product development. A study published in

1991 used RSM to evaluate gluten-flee breads based on three types of

rice flour. Optimal loaves were formulated with medium-grain, finely

ground rice flour, low levels of HPMC and low levels of CMC. A

second trial used the same rice flours, but the breads were based on

formulas of 80% rice flour and 20% potato starch. Using sensory

measurements from a trained panel, RSM was used to find optimal CMC,

HPMC and water combinations for the different rice flours. Gluten-

free loaves made with medium-grain rice flours were of a higher

standard with respect to moistness, cohesiveness, flavor, color and

cell structure than those made from long-grain rice flour.

Another study investigated optimal proportions of cornstarch,

cassava starch and rice flour in gluten-free breads that also had

0.5% soy flour for improved bread crumb characteristics. The optimal

formulation was calculated as 74.2% cornstarch, 17.2% rice flour and

8.6% cassava starch. Unusually large gas cells were rectified by the

addition of soy flour.

RSM has been employed at the authors' laboratory at The National

Food Centre (Dublin, Ireland) to develop and optimize a gluten-free

bread formulation based on rice flour, potato starch, skim milk

powder and HPMC. (See chart " Optimizing a Formula. " )

RSM has been used to analyze the effects of methylcellulose, gum

arabic and egg albumen on the sensory properties of gluten-free flat

breads based on corn flour and pre-gelatinized rice flour and

cornstarch. Methylcellulose and egg albumen were the major

determinants of product sensory quality.

A novel approach at The National Food Centre (Cork, Ireland) looked

at supplementing a control gluten-free bread formula based on rice

flour and potato starch with fish surimi at a 10% level (of starch

weight). Surimi, a concentrate of myofibrillar proteins, is a highly

functional ingredient with excellent gel-forming properties. Frozen

surimi of four species was evaluated. Texture profile analysis (post-

baking) indicated that three of the surimi breads had a softer

(P<0.001) crust and crumb than the controls. These breads also

revealed higher (P<0.001) loaf volumes than the controls.

The greater awareness of the prevalence of Celiac Disease will

continue to drive interest in gluten-free products. A common

approach is to use a variety of ingredients to mimic gluten.

However, more research is needed in this area.

The original, heavily referenced article has been condensed and

adapted by Dziuk O'Donnell, Chief Editor, Prepared Foods

from the following source: Trends in Food Science & Technology,

Volume 15, E. Gallagher(1), T.R. Gormley(1) and E. K. Arendt(2),

Recent Advances in the Formulation of Gluten-free Cereal-based

Products, Pages 143-152, Copyright 2004 with permission from

Elsevier. www.sciencedirect.com/science/journal/09242244

(1) Teagasc, The National Food Centre, Ashtown, Dublin 15, Ireland

(2) Department of Food and Nutritional Science, National University

of Ireland, Cork, Ireland

* Corresponding author: egallagher@...

Website Resources: www.celiac.org--Celiac Disease Foundation

www.celiaccenter.org--The University of land Celiac Center

www.niaid.nih.gov/fadsheets/food.htm--National Institute of Health

(NIH) site on food allergy and intolerance

http://digestive.niddk.nih.gov/ ddiseases/pubs/celiac/index.htm--

Another NIH site

www.GFlinks.com--A large collection of links to Celiac

Disease/gluten intolerance sites

Referenced Pizza, Pasta and Cookie Information

One paper (Huang JC, et al., 2001. Journal of Food Quality, 24, p.

495) reported on a study where non-gluten pasta had sensory

properties and pasta stickiness closest to wheat-based pasta when

higher levels of modified starch, xanthan gum and locust bean gum

were used. In 1999, Wang N, et al. (Journal of Food Science, 64, p.

671) found that pasta of 100% pea flour and made on a twin-screw

extruder exhibited improved texture and flavor after cooking, when

compared with the same product prepared using a conventional pasta

extruder.

The effects on a gluten-free cookie formulation using six different

starch sources in combination with four different types of fat

sources was studied by Arendt EK, et al. (2002, Farm and Food, 12,

p. 21). Among other findings, rice, corn, potato and soy with high-

fat powders produced sheetable cookie doughs that resulted in

finished products of comparable quality to wheat-based cookies. They

also found that cornstarch, guar gum and high-fat powder produced

acceptable gluten-free pizza bases.

In 1996, Tosi, E.A., et al. (Alimentaria, 34, p. 49) reported that

the addition of 0.1% BHT to the fat for gluten-free cookies of

wholemeal amaranthus flour extended the shelflife without enhancing

[changing] flavor.