Effect of Nutrim Oat Bran and Flaxseed on Rheological Properties of Cakes

Cake shortening contents were replaced with Nutrim oat bran (OB) and flaxseed powder, and the effects of these substitutions on the physical and rheological properties of cakes were investigated. Cakes with shortening replaced up to 40% by weight possessed a volume similar to that of the control cake produced with shortening. Replacement using Nutrim OB and flaxseed powder revealed significant color changes in both the cake crust and crumb. At high levels of substitution, the cake crust became lighter, while the crumb darkened. At >40% by weight substitution with either Nutrim OB or flaxseed, the cakes displayed increased hardness; however, cohesiveness and springiness increased gradually with increasing substitution. Increased substitution with Nutrim OB caused an increase in the measured shear viscosity and oscillatory storage and loss moduli of the cakes. Increased substitution with flaxseed caused decreases in these rheological parameters. Additional rheological experiments were performed to elucidate changes in the formulations during the baking process and indicated an increase in the elasticity of the baked batter with decreasing shortening.     

Glycemic Response to Extruded Oat Bran Cereals Processed to Vary in Molecular Weight

Oat β‐glucan enriched extruded cereals with molecular weights (MWs) ranging from 2,180,000 to 326,000 were produced. Test meals composed of 31 g of available carbohydrate, 8.3–8.7 grams of β‐glucan, and milk were administered to subjects and their postprandial blood glucose levels monitored for 2 hr. White bread plus milk and a control wheat bran cereal plus milk were administered, and white bread alone served as a reference food for estimation of glycemic index (GI) of the cereals, after adjusting for the effect of adding milk to white bread. Both oat bran and wheat bran cereals significantly reduced peak blood glucose rise (PBGR) and area under the curve (AUC) versus white bread alone or white bread plus milk. There was a significant inverse relationship between AUC and log₁₀[weight average MW] (r² = 0.96, P = 0.0192). There was a significant inverse relationship between PBGR and log₁₀[viscosity] of in vitro extracts from all cereals, including the wheat control (r² = 0.96, P = 0.0031). However, no significant differences in glycemic responses among the oat bran cereals were found with pairwise comparisons. All cereals were low GI (<55) and were significantly lower than white bread alone or white bread plus milk. Among the oat bran cereals, palatability was positively correlated with MW (r² = 0.98, P = 0.0110).     

Preparation of High‐Quality Protein‐Based Extruded Pellets Expanded by Microwave Oven

The aim of this work was to study the effects of extrusion barrel temperature (75–140°C) and feed moisture (16–30%) on the production of third‐generation snacks expanded by microwave heating. A blend of potato starch (50%), quality protein maize (QPM) (35%), and soybean meal (SM) (15%) was used in the preparation of the snacks. A laboratory single extruder with a 1.5 × 20.0 × 100 mm die‐nozzle and a central composite routable experimental design were used. Expansion index (EI) and bulk density (BD) were measured in expanded pellets, viscosity at 83°C (V₈₃), thermal properties, and relative crystallinity were measured in extruded pellets. EI increased and BD decreased when the barrel temperature was increased, while the feed moisture effect was not significant. V₈₃ increased when feed moisture increased. Extrusion modified the crystalline structures of the pellets and the X‐ray data suggests the formation of new structures, probably due to the development of amylose‐lipid complexes. The maximum expansion of pellets was found at barrel temperatures of 123–140°C, and feed moisture of 24.5–30%. It is possible to obtain a functional third‐generation snack with good expansion characteristics using a microwave oven, and this snack has health benefits due to the addition of QPM and SM.     

超细粉碎辅助提取裸燕麦多糖工艺研究

以燕麦麸皮为原料,研究了超细粉碎辅助提取裸燕麦多糖的工艺技术。对裸燕麦麸皮进行超细粉碎,采用X射线小角散射法检测了麸皮的粒度分布,并通过单因素实验和正交实验优化了裸燕麦多糖的提取条件。确定超细粉碎后的燕麦麸皮的平均粒度为397.6nm,中位粒径为408.9nm,分布散度为134.8nm;裸燕麦多糖的提取条件为:提取时间0.5h,料液比为1:20,提取4次,提取温度60℃;该工艺条件下多糖的得率为0.126 g·g-1。本研究为裸燕麦的精深加工提供了理论依据,并为进一步研究裸燕麦多糖的结构效应关系奠定了基础。     

Development and Characterization of Extruded Pellets of Whole Potato (Solanum tuberosum L.) Flour Expanded by Microwave Heating

In various Latin American countries, large volumes of potato are classified as unsuitable for use as food and destined for use as feed. This raw material has a high starch and fiber content that could be used in the production of different kinds of food. The objective of this research was the preparation and characterization of extruded whole potato pellets expanded by microwave heating. A 3³ central composite routable experimental design and response surface methodology were used. The barrel temperature (BT, 93–127°C), feed moisture (FM, 19–29%), and corn starch concentration (CS, 3–37%) in the blends were evaluated. CS was the most important variable affecting the functional properties of the expanded pellets. Adding CS to the blends increased the expansion index and viscosity and improved luminosity, decreasing the apparent density and breaking force of the products. Low BT and especially high FM increased the luminosity of the expanded pellets. Increasing FM content increased the viscosity of the expanded pellets. The best functional characteristics for the expanded pellets were obtained using a blend of 63% potato flour and 37% CS, extruded at 110°C BT with 24% FM content. Nonfood-grade whole potato flour showed good potential for use in the production of expanded pellets with acceptable functional properties.     

Physical and Sensory Characteristics of Extruded Products Made from Two Oat Lines with Different β‐Glucan Concentrations

The impact of extrusion on physical and sensory properties and on the in vitro bile acid (BA) binding was examined for N979 and Jim oat (Avena sativa) lines with 8.1 and 4.8% β‐glucan, respectively. Based on hardness and edibility of products made from Jim oats, moisture concentrations of 16–25% and temperatures of 165–180°C were selected for N979 extrusion. Jim‐based cereal had a significantly greater (P < 0.05) expansion ratio than did N979‐based cereal at most moistures. N979 cereal was browner, but not harder, than Jim cereal. Extruded products from N979 and Jim oats had 5.29–5.99% and 3.38–3.94% β‐glucan, respectively. Changing extrusion temperature or moisture content did not affect β‐glucan concentration in the products. N979 cereal made at 165°C and 16% moisture had greater BA binding than at other conditions, and had crunchiness comparable to cereals made at other conditions. BA binding of Cheerios brand breakfast cereal was close to that of N979 cereal made at 180°C and 18% moisture, but lower than cereals made at other conditions. Cereals made from Jim and N979 oats were browner, harder, coarser, and crunchier than Cheerios breakfast cereal. Proper processing and preparation techniques should be considered when producing extruded products from high β‐glucan oats.     

Polar Lipids from Oat Kernels

Oat (Avena sativa L.) kernels appear to contain much higher polar lipid concentrations than other plant tissues. We have extracted, identified, and quantified polar lipids from 18 oat genotypes grown in replicated plots in three environments to determine genotypic or environmental variation in these lipids. Validation experiments indicated a solid phase silica gel extraction step elution provided excellent and clean separation of extracted lipids into neutral lipid, glycolipid, and phospholipid fractions. Analysis of phospholipids by HPLC (normal phase, diol column) indicated phosphatidylethanolamine, phosphatidylcholine, phosphatidic acid, phosphatidylglycerol, phosphatidylinositol, and lyso‐ forms but very little genotypic or environmental variation. Di, tri and tetragalactosyl‐diacylglycerols were quantified in the glycolipids, along with their mono‐, di‐, and triacyl estolides. Most of these exhibited significant genotypic variation. Molecular species analysis of the glycolipids in the Morton cultivar by direct infusion electrospray ionization tandem mass spectrometry confirmed the enormous diversity of galactosyl‐lipids in oats. Analyses indicated total lipid of ≈8.3% (dry weight basis), of which ≈10% was phospholipid and 11% was glycolipids. These results indicate that oats are a rich source of polar lipids and contain an extremely rich diversity of galactosyl‐lipids.     

Effects of Gelatinization and Moisture Content of Extruded Starch Pellets on Morphology and Physical Properties of Microwave‐Expanded Products

Extruded pellets were prepared from normal corn starch using a corotating twin‐screw extruder (25:1 L/D ratio, 31 mm diameter screw), and then expanded by heating in a conventional microwave oven for 70 sec. The effects of gelatinization level and moisture content of the extruded pellets on the morphology and physical properties of the microwave‐expanded products such as puffing efficiency, expansion bulk volume, and bulk density were investigated. The expanded shape and air cell structure differed according to the degree of gelatinization of the pellets. Maximum puffing efficiency and expansion volume with the pellets containing 11% moisture were achieved at 52% gelatinization. For this level of gelatinization, starch was extruded at 90°C barrel temperature. In addition, the moisture content of the pellets critically affected the expansion behavior. The maximum puffing efficiency and expansion volume were achieved in a moisture range of 10~13%. For optimum product shape and uniform air cell distribution, the pellets should undergo sudden release of the superheated vapor during the microwave‐heating. The expansion by microwave‐heating was optimized at ≈50% gelatinization.     

Comparative Biomass Production of Six Oat Varieties in a Saline Soil Ecology

Oat is widely used as a food source in human and animal diets. In China, supplementary cultivation of oat has recently been extended into marginal saline soils, due to its extensive use. The goal of the present study was to explore and compare the agronomic characteristics, biomass production, and distribution of oat in coastal saline soil. A single-factor randomized block design experiment with six naked and husked oat varieties [Bayou-1 (BU-1), Baiyan-2 (BY-2), Baiyan-7 (BY-7), Huawan-6 (HW-6), Huazao-2 (HZ-2), and Pin-16 (P-16)] as treatments was conducted in the Hebei Province of China. The growth period (77 to 88 days) of the six oat varieties were shorter in saline soil than their original breeding region. Moreover, the plant was shorter, with a lower grain number per plant and seed setting. Grain weight increased and no change was observed in the floret number in coastal saline soil relative to the original habitats. The BY-7 variety produced the highest biomass value of 7.0 t ha^?1 compared to the other five varieties. Compared with two active growth points, most varieties in the present study showed just one growth activity point between elongation and heading. Two fast growth periods for the six oat varieties were due to the high total leaf biomass growth rate (BGR) from elongation to heading and panicle BGR from heading to maturity. The biomass growth ratio (BGO) during elongation to heading was the largest among the four growth stages of the oat varieties. The number of kernels per spike decreased at the research site, but grain weight increased. Substantial differences were observed for growth periods, biomass, BGR, BGO, and other agronomic characters in the coastal saline soil of North China, but the BY-7 variety was the most suitable variety for the study site.     

Characterization of Oat Endoproteinases that Hydrolyze Oat Avenins

During oat seed germination, the insoluble storage proteins must be solubilized and transported to the embryo for use by the developing plantlet. We showed earlier that pH 6.2 active serine and metalloproteinases were the predominant gelatin‐hydrolyzing enzymes of oats, while the oat globulins were degraded by pH 3.8 active cysteine proteases. The pH of the endosperms of germinating oats is 6.2. We have continued our characterization of the germinated oat proteinases by determining which hydrolyze avenins, the oat storage prolamins. Avenins of resting seeds were purified and hydrolyzed with proteinases that were extracted from oat seeds that were germinated for various periods. The peptides released were analyzed using SDS‐PAGE. The α‐avenins were hydrolyzed at pH 3.8 by cysteine proteinases from four‐day germinated seeds and the β‐avenins were hydrolyzed by similar enzymes from eight‐day germinated seeds. At pH 6.2 or pH 5.0, the avenins were not degraded by any of the germinated oats endoproteinases. It is probable that some kind of pH compartmentalization occurs within germinating oat seed. After four days of germination, either new proteinases form or some preexisting proteinases are activated. The cysteine proteinases are apparently responsible for the majority of the storage protein hydrolysis that occurs during oat germination.     

Characterization of Oat Endoproteinases that Hydrolyze Oat Globulins

During the germination of oats, the major seed storage proteins (globulins) are hydrolyzed by endoproteinases. We have used two methods to characterize these endoproteinases. A qualitative PAGE method that used oat globulins as gel‐incorporated substrates was used to determine which enzymes hydrolyzed the globulins. The proteolytic hydrolysis products were studied by hydrolyzing the globulins in vitro with the endoproteinases and analyzing the products by SDS‐PAGE. Class‐specific proteinase inhibitors were used to show that the globulin hydrolyzing enzymes were cysteine‐class proteinases. The proteinases were active at pH 3.8. Using the gel analysis method, a little activity was present at the beginning of seed germination, but the major activity only appeared on the sixth day of germination. Extracts from four‐day germinated oats contained cysteine proteinases that hydrolyzed the globulins in vitro to form a polypeptide of intermediate size (MW ≈34,500). Cysteine proteases from an eight‐day germinated sample totally hydrolyzed the globulins in <1 hr. Very little hydrolysis occurred at pH 6.2, the pH of germinated oats endosperm tissue. The fact that hydrolysis occurred quickly at pH 3.8 implies that there is probably pH compartmentalization within the endosperm, with some areas of the seed having a low pH value where the globulins can be degraded.     

Flavor Retention and Physical Properties of Rice Cakes Prepared from Coated Rice Grain

Flavored rice cakes are produced commercially by spraying a flavor coating on the cake surface. This study describes a method of making a flavored coating that is applied to individual rice grains before puffing and results in a more uniform flavor distribution. Rice was coated at 5% or 10% levels with coating materials made of jet‐cooked (JC) starch or starch cooked in a water bath (WB), corn starch powder, salt, and a flavor compound. The viscosity of coating materials made with WB starch was twice that of coatings made of JC starch. Rice coated at 10% level had decreased specific density of rice cakes. Rice cakes made from coated grain were similar in appearance to cakes made from uncoated rice but had higher flexural strength. Retention of flavor volatiles after puffing the coated grain was 82.8–56.8% for apple, 72.5–40.3% for anise, and 52.5–24.8% for onion flavor. The flavor volatiles measured in the rice cakes decreased during a three‐month storage period to 49.3% for apple, 25.8% for anise, and 10.1% for onion flavor. Slightly higher retention of flavor volatiles was observed in cakes made with WB starch than in cakes made with JC starch. The difference in retention of flavor volatiles between starch slurry or starch‐oil emulsion treatments was small.     

Stability of Oat Avenanthramides

The three main oat avenanthramides, N‐(4′‐hydroxy)‐(E)‐cinnamoyl‐5‐hydroxyanthranilic acid ( Bp ), N‐(4′‐hydroxy‐3′‐methoxy)‐(E)‐cinnamoyl‐5‐hydroxyanthranilic acid ( Bf ), and N‐(3′,4′‐dihydroxy)‐(E)‐cinnamoyl‐5‐hydroxyanthranilic acid ( Bc ), and their corresponding cinnamic acids, p‐coumaric ( P ), ferulic ( F ), and caffeic ( C ), were investigated for stability to pH, temperature, and UV‐light treatment. The retention of the avenanthramides after processing of oat‐based food products was also analyzed. The avenanthramide Bc and the cinnamic acid C were sensitive to alkali and neutral conditions, especially in combination with heat treatment, whereas the other compounds studied were more stable. The cinnamic acids but not the avenanthramides were isomerized when irradiated with UV‐light. The avenanthramides were restored after processing of oat‐based products.     

The Impact of Oat Quality on White Salted Noodles Containing Oat Flour

This research compared the physicochemical properties of six milling oat cultivars from Western Australia over two growing seasons (2011 and 2012). Variations among the cultivars in physicochemical properties, particularly β‐glucan content, were assessed to determine their suitability for incorporation into white salted noodles at a level of 30% of the flour component. The average across six oat cultivars grown in 2012 was significantly higher (P < 0.05) for protein content, lipid content, and volume of smaller sized particles (<100 µm) and significantly lower for ash content, starch damage, and volume of larger particles (>100 µm) in comparison with the average across the same oat cultivars grown in 2011. The year of cultivation by cultivar interaction was significant (P < 0.05) for ash content, protein content, β‐glucan content, starch damage, and particle size. Oat cultivar Mitika had the highest peak viscosity for 100% oat flour (whole groat) and 30% oat–wheat (OW) flour blend, which may be owing to lower amylose percentage, high protein content, and greater volume of smaller particles. The effect of growing season had greater impact on OW noodle firmness than the genetic effect of cultivars. The eating and cooking quality attributes of OW noodles, such as color, color stability, firmness, and cooking solid loss were superior for those incorporated with 2012 oat flour (whole groat) compared with 2011 oat flour. Among the six oat cultivars, Williams produced noodles with poor cooking and eating quality, and Mitika was easier to handle during processing and produced noodles with superior brightness and color stability in comparison with other oat cultivars evaluated.     

Effects of Waxy Rice Moisture Content and Rate of CO2 Injection on Characteristics of Extruded Pellets and Vacuum‐Puffed Yukwa (a Korean Traditional Snack)

Extrusion with CO₂ injection was developed to simplify the process of producing vacuum‐puffed yukwa (rice snacks). The effects of feed moisture content and CO₂ injection on the characteristics of extruded pellets (maximum viscosity and degree of gelatinization) and vacuum‐puffed yukwa (expansion ratio, bulk density, hardness, and color) were investigated. Higher feed moisture increased the size of vacuum‐puffed yukwa and the degree of gelatinization, whereas the maximum viscosity decreased. Maximum viscosity and gelatinization degree of extruded pellets were highly correlated with expansion ratio, bulk density, hardness, and color values of vacuum‐puffed yukwa. Increasing feed moisture content significantly increased expansion ratio but decreased bulk density and hardness. CO₂ injection decreased bulk density and hardness of vacuum‐puffed yukwa.     

Evaluation of a Two-Step Baking Procedure for Convenience Sponge Cakes

Typical examples of convenience foods in the bakery section include partially baked bread, rolls, croissants, and crumpets. The effects of processing variables on sponge cake characteristics were studied in a two-step baking procedure. A fractional two-factorial design was applied to describe the effects of the predictor variables on product properties. Flour type, oven type, and baking time in each baking phase were selected as categorical predictor variables on the basis of preliminary baking tests. The performance of a microwave oven was compared with that of a conventional oven. The properties of the new twice-baked products were characterized and compared with those of a standard product by using the results derived from baking tests, color measurements, and texture analyses. Correlation analysis was used to detect relationships between the response variables. Significant relationships between baking test values and texture analysis values closely related to aspects of microwave cooking were found.     

Replacement of Shortening in Yellow Layer Cakes by Corn Dextrins

Shortening in a conventional yellow layer cake was replaced by maltodextrin (MD), amylodextrin (AD), octenyl succinylated amylodextrin (OSAD), or mixtures (MD+AD and MD+OSAD). The physical and sensory characteristics of the shortening‐free cakes were investigated. The specific gravity and viscosity of the cake batter, and the volume index of the baked cake were significantly reduced by MD, whereas the cake with added AD or OSAD showed a higher volume index than the control cake containing the shortening. An equivalent mixture of MD and AD, or MD and OSAD, however, produced cakes with a volume index and color defined as ΔE*(ab) that was similar to the control cake. Sensory evaluation revealed that the cakes containing AD or OSAD had significantly higher firmness than the control, but the cakes containing a mixture of MD and AD had firmness, springiness, and overall flavor scores similar to that of the control cake. According to instrumental texture profile analysis (TPA), MD addition, either alone or mixed with AD or OSAD, reduced firmness, whereas AD addition made the cake significantly firmer. When the shortening‐free cakes were stored for eight days at 4°C, TPA revealed greater changes in cake firmness and adhesiveness for MD alone. Cakes made from mixtures of dextrins (MD+AD and MD+OSAD) showed textural change with storage similar to that of the control cake, although the MD+AD cake remained softer than the control.     

Creep Deformation Modeling of Glutinous Rice Cakes (Mochi)

The viscoelastic properties of glutinous rice cakes (mochi) made by extrusion at different conditions (water contents of 45–55% and barrel temperatures of 75–95°C) and commercial rice cakes were studied by a creep test. The maximum compliances of extruded mochi were 0.15–4.23 1/kPa. Among the extruded samples, the mochi extruded at 75°C with a water content of 55% was the one that yielded the largest maximum compliance. At the same barrel temperature, the creep compliance increased with the water content. Four models with different numbers of elements (spring and dashpot) were employed to fit the experimental data. The model coefficients were able to provide the corresponding elastic and viscous behavior of the sample. The 3‐element model (a spring in series with a Kelvin‐Voigt model) did not exhibit steady‐state compliance as observed in the experimental data. The 4‐element (Burger's model), modified 4‐element (an approximation of Burger's model), and 6‐element model (adding one more Kelvin model to the Burger's model) yielded R² > 0.99. Results showed that the 4‐element model was adequate to describe the creep behavior of mochi.     

Physical Properties of Extruded Wheat Starch-Additive Mixtures

The effects of the addition of fatty acids, monoglycerides (MG), and wheat germ oil (WGO) on the level of crystallinity and the crystalline structure of extrusion-cooked wheat starch have been studied using twin-screw extruders. Measurements of water solubility and water absorption indices were made on the extrudates, together with specific mechanical energy (SME) consumption and die pressure for the extruder. MG and the fatty acids added to a level of 4% caused an increase in V_hydrate type crystallinity. WGO addition to a level of 8% caused no change in crystallinity, although the E_hydrate type was favored at lower moisture contents. All additives caused a decrease in SME and an increase or maximum in die pressure. WGO behaved differently than MG and fatty acids in that its addition caused the water solubility index and expansion to increase, as previously observed for other oils added to flours.     

Application of Oat Oil in Breadbaking

Lipids, especially polar lipids, can improve loaf volume, grain and texture, and delay staling in bread. Oats (Avena sativa L.) are rich in total and polar lipids. We have investigated the effect of oat lipids in a bread formulation on loaf volume, appearance, and bread staling. Oat oil was fractionated into polar and nonpolar fractions by water‐degumming. Crude oat oil and shortening (at 3%) increased loaf volume by ≈11% over the zero lipid formulation. The polar lipid fraction increased loaf volume by nearly the same amount when added at only a 0.5% level. The addition of 3% crude oat oil or 0.7% oat oil polar fraction significantly delayed bread firming and starch retrogradation; the difference between oat lipids and shortening was more evident at the end of a four‐day storage period. Oat lipids had a stronger relative effect on bread from a weak flour (10% protein) than from a strong flour (14% protein). The effects of oat oil in the bread formulation could be related to the amphipathic character of polar lipids in oats that enables them to interact with starch, proteins, and other bread components.