C EREAL -B ASED F OODS

1.8.1 C EREAL -B ASED F OODS

Oatmeal, oat flakes (rolled oats), and oat bran have found a substantial number of applications in breakfast hot cereals, and oat flour is a frequently used ingredient in cold cereals and oatmeal in granola cereals and bars. The high fat of oat flour tends to restrict its utilization in highly expanded extruded cereal products because of oxidative rancidity problems. 191 On the other hand, barley is an excellent material for extrusion into ready-to-eat (RTE) cereal products. 27,186 Barley flour from four cultivars and a hulless waxy cultivar (Wanubet) was incorporated into extruded rice

products. 27 Consumer sensory panelists rated cereals extruded from the four 50:50 barley–rice blends and the 65:35 Wanubet barley–rice blend higher than the 100% rice cereal for crispness and color, and rated them similar to the rice cereal for flavor and overall acceptability; these products contained >2% (w/w) β-glucans. Instead, cereals produced by 100% barley flour had limited expansion and high bulk densities.

In the past, oat and barley flours have not been extensively used in yeast-leavened bread, since they are less desirable than wheat flour due to the lack of gluten and their higher soluble fiber content leading to greater water retention. 186,191 In addition to undesirable effects on crumb texture and loaf volume, incorporation of whole oat or barley flour or fiber-rich fractions from cereals into bread makes the color of the

end product darker. Bhatty, 22 studying the bread-making properties of hulless barley, suggested that 5% or possibly 10% barley flour could be added without seriously

affecting loaf volume and bread appearance. However, the renewed interest in high- fiber foods has expanded the utilization of cereal fractions enriched in β-glucans.

Several bakery products have been prepared using oat and barley high β-glucan fractions such as bran, and shorts or even water-extracted fractions. Delcour et al. 192 reported that addition of oat β-glucan increases the volume of gluten–starch loaves, most likely by increasing the viscosity of dough, while Wang et al. 193 claimed that

42 Functional Food Carbohydrates

β-glucan might play a role in improvement of bread crumb grain by stabilizing air cells in the dough and preventing their coalescence. Recent investigations on the contribution of β-glucans to the pasting characteristics of oat flours indicate the

influence these polysaccharides have on such properties. 194,195 Significant correla- tions have been established between β-glucan concentration and the pasting param-

eters, such as pasting peak viscosity after amylolysis, which might be explained by an increase of water-binding capacity of oat flours with high β-glucan concentra-

tion. 194 However, research on experimental foods in which wheat flour was replaced by enriched β-glucan fractions revealed some difficulties in bread manufacturing. Krishnan et al. 196 substituted white wheat flour at 10 and 15% levels with commercial oat bran and found that the dough properties and bread quality were dependent on substitution levels and particle size reduction of bran; the water absorption require- ments of oat bran doughs increased and the loaf volume decreased with increasing levels of bran and reduction of bran particle size. The 10% blends (large- and intermediate-size bran) produced doughs of good stability, and the 10% bran breads had better loaf volume, grain, and texture than 15% breads. A taste panel preferred the 15% bran breads made with large-size bran and 10% bran breads made with

intermediate-size bran. Newman et al. 29 observed that incorporation at 28% of a fiber-rich fraction from waxy hulless barley cultivar in wheat flour depressed the

loaf volume of yeast pan bread dramatically, although sensory analysis rated the fiber-enriched bread equal to a bread made from the same base wheat flour enriched

with 50% whole wheat flour. The potential of fiber-rich fractions (β-glucan content,

8.1 to 15.2% total, 2.8 to 7.3% soluble) from hulless barley cultivars produced by

a simple roller-milling procedure 72 as functional bread ingredients has recently been examined. 197,198 The added fiber-rich fraction was adjusted from 11 to 12%, depend- ing on the barley genotype (waxy, high amylose, normal starch), to result in a constant addition of 2.5 g of β-glucans and arabinoxylans per 100 g of flour. A sponge-and-dough process using a high-protein-content wheat flour supplemented with xylanase resulted in breads with reasonable quality; bread made with the fiber- rich fraction from waxy barley exhibited the best volume and crumb structure, whereas bread with added fiber-rich fraction from the high-amylose genotype was

the worst. Knuckles et al. 28 reported an increase in water absorption in bread dough, time to peak at farinograph, and mixing time by addition of β-glucan-enriched barley fractions. However, bread in which a dry-milled/sieved barley fraction containing 19% β-glucans replaced 20% of the standard flour was judged acceptable in labo- ratory acceptance tests, although the loaf volume was reduced and the color was slightly darker than the control. Moreover, for breads in which the wheat flour was substituted by 5% with a water-extracted barley fraction, containing 33% β-glucans, the color scores and acceptability improved over those breads made with the dry- milled/sieved barley fraction; the former and the latter breads contained 3.6 w/w (1.1% soluble) and 1.9% w/w (0.9% soluble) β-glucans, respectively. Similarly,

Cavallero et al. 31 produced bread with a high amount of β-glucans by replacing the wheat flour with 50% whole-grain flour (4.6% β-glucan content), a 50% dried sieved

fraction (8.5% β-glucan), or a 20% water-extracted fraction (33.2% β-glucan) from barley. The bread with the 20% water-extracted barley fraction, despite its highest β-glucan content (6.3% total, 5.7% soluble) among all the experimental breads,

Cereal β -Glucans: Structures, Physical Properties, and Physiological Functions 43

showed the best scores for sensory attributes (color, flavor/aroma, texture), even comparable to the control.

Muffins prepared using 100% barley flour exhibited equal or higher overall acceptability scores than the control wheat muffins, although volume and density were influenced by barley cultivar; the average muffin contained about 0.8 to 1 total

and 0.4 to 0.5 g soluble β-glucans. 25 Hudson et al. 26 replaced the wheat flour in a traditional muffin recipe by oat bran (-glucan content = 9.3%) and a dry-milled/sieved

high β-glucan barley fraction (-glucan content = 18.9%) at levels of 100 and 40%, respectively, and the resulting products were acceptable. These higher-fiber muffins

contained more β-glucans (3.8 to 4.5%), moisture, protein, and minerals, and had

20 to 30% fewer calories than the commercial muffins. In a later study, 29 barley shorts obtained from roller milling of a waxy hulless cultivar and containing 18%

dietary fiber were incorporated into baked products, such as muffins, biscuits, and sugar cookies, at 23 to 30% of the wheat flour, to double the soluble dietary fiber content without sacrificing product quality; the overall acceptability scores of the baked products prepared with the barley milling fraction were similar to those for the standard products.

Barley fractions, enriched in β-glucan, have been used in mixtures with semolina to produce pasta with acceptable sensory properties. Pastas in which a dry-milled/sieved barley fraction containing 19% β-glucans replaced the wheat sem- olina by 20% provided increased amounts of β-glucans (4.1 total and 2.1% w/w soluble); the fortified products had acceptable sensory quality scores, although they were darker in color than the control. Moreover, substitution of semolina by 20% with a water-extracted barley fraction containing 33% β-glucans yielded β-glucan- enriched pastas (7.1 total and 6.3% w/w soluble) with quality characteristics com-

parable to the control. 28 Functional pastas were also prepared by replacing 50% of durum wheat semolina with dry-milled/sieved barley pearling by-products enriched in β-glucans (9.1 to 10.5% db), adding 5% vital wheat gluten and adopting a high- temperature drying processing. Although the products were darker and less yellow than those of durum wheat pasta, the modified barley pastas had good cooking qualities with regard to stickiness, bulkiness, firmness, and total organic matter released in rinsing water, as well as a much higher β-glucan content (4.3 to 5.0%

db). 30 Recently, roller-milling fractions prepared by Izydorczyk and coworkers 72 from hulless barley genotypes with variable amylose content were added to pasta 34 and noodles, 35,36 resulting in products with satisfactory textural attributes. When hulless barley flour replaced wheat semolina at 40%, color of pasta was adversely affected. However, when barley was pearled 15% before milling, the color of barley flour–semolina blends was reasonably acceptable. Replacing 40% of semolina with high-amylose or normal starch hulless barley flours made spaghetti slightly less firm, whereas replacement by zero amylose hulless barley flour made spaghetti substan- tially firm. Addition of the fiber-rich fraction derived from roller milling (10.3 to 18.3% β-glucans) did not impact spaghetti firmness. Color was unfavorably affected by incorporation of the fiber-rich barley fractions into pastas, but when a sufficient fraction from the high or zero amylose cultivar (11%) was added to increase the

β-glucan content by 2%, the color was reasonably acceptable. 34 Yellow alkaline noodles containing a blend of wheat flour and the hulless barley flour (20 and 40%)

44 Functional Food Carbohydrates

were prepared with minimal processing difficulties. The addition of any barley flour changed noodle appearance due to significant decreases in noodle brightness and yellowness, combined with increased redness and “speckiness.” The addition of flour to a 40% level increased water absorption, cooking time, and cooking losses, as well as firmness. Moreover, the starch characteristics (amylose/amylopectin ratio) seemed

to play an important role in altering the texture of noodles. 35 Replacement of 25% wheat flour to white salted and yellow alkaline noodles with the fiber-rich fraction

obtained from roller milling posed no problem in noodle processing, although water absorption had to be substantially increased; however, the products were significantly

darker and contained more brown specks than the wheat flour control noodles. The addition of the fiber-rich fraction improved the cooked yellow alkaline noodles’ texture, as evidenced by increased firmness and chewiness. Overall, fresh yellow alkaline and white salted noodles enriched by fiber-rich barley fraction offer conve- nience due to short cooking time, improved nutritional quality, and acceptable cooking quality, particularly when intended for health-conscious consumers. 36