Lower Water Absorption Index Research Articles

English

Selected physical properties of white maize meal, obtained by different dry-milling techniques were evaluated and correlated to the texture of stiff and thin porridge. Sifted or par-cooked maize meals had finer particles than hammer-milled maize meals. Hammer-milled maize meals had lower water absorption indices (17-38%) and higher water solubility indices (WSI, 4-5%) than sifted (41-42 and 2-3%, respectively) or par-cooked (114 and 2%, respectively) maize meals. Sifted or par-cooked maize meals had lower breakdown viscosities (0-19 BU) and higher final viscosities (818-1925 BU) than hammer-milled maize meals (89-173 BU and 530-780 BU, respectively). Stiff porridge prepared from par-cooked maize meal (34% w/v), and thin porridge from dehulled and hammer-milled maize meal (10% w/v) had the firmest textures at 80.93 and 1.28 N, respectively. There was a negative correlation (P < 0.05, r = -1.00) between the WSI and total shearing force of stiff porridge prepared from par-cooked maize meal.    Key words: Maize, porridge, texture, Pearson correlation coefficient.

분쇄 방법이 품종이 다른 쌀가루의 품질에 미치는 영향

국내에서 육종된 8가지 품종의 쌀을 습식과 건식제분하여 제분 방법에 따른 쌀가루의 품질변화를 품종별로 분석하고 이를 바탕으로 제분 방법에 비교적 민감하지 않고 일정한 품질의 가루를 생산할 수 있는 국내산 쌀 품종을 찾고자 하였다. 건식제분은 예상한 바와 같이 낟알의 경도가 높은 품종이 전분 손상도가 높았으나 습식제분에서는 Chenmaai와 같이 불린 쌀의 경도가 높더라도 전분의 손상도는 상대적으로 낮았다. 건식제분에 따른 손상 전분 함량의 증가는 쌀가루의 수분 흡수력을 급격히 증가시켰으며 습식제분은 낟알의 경도보다는 아밀로오스 함량에 따라서 수분 흡수력에 차이를 나타내었다. 가루의 수분 흡수력과 반비례하여 반죽의 질척한 정도가 나타나지만 고 아밀로오스 함량의 Suweon 517과 Milyang261은 제분 방법에 관계없이 수분 흡수력이 매우 높아서 빵이나 국수 등의 제품을 생산할 때 반죽에 더 많은 양의 물을 첨가해야 할 것으로 생각된다. 또한 건식제분된 가루가 습식제분된 가루에 비하여 수분 흡수력이 크기 때문에 반죽 과정에서 수분 첨가량을 증가시켜야 할 것이다. 건식제분은 품종 모두에서 최고 점도에 이르는 시간이 짧아지고 점도 붕괴가 증가하므로 습식 가루에 비하여 조리시간을 단축하고 호화 후 점도 조절이 필요하다. Hanareumbyeo, Manmibyeo, J insumi , Goamibyeo 등은 건식제분과 습식제분에 따른 호화 특성의 변화가 다른 품종에 비하여 크며, Suweon517과 Milyang261은 건식제분하면 setback 값이 증가하는 것으로 미루어 건식제분된 가루를 이용한 제품의 노화가 더 클 것으로 예측된다. 이상의 결과에 따라서 Chenmaai는 건식과 습식제분 모두에서 손상 전분의 함량이 낮고, 건식제분에 따른 수분 흡수율 증가가 적으며 제분에 따른 호화 점도 특성의 변화가 상대적으로 적어서 제분에 유리한 품종이다. 반면 Seolgaeng와 Suweon517은 낟알의 경도가 부드러운 분상질일지라도 건식과 습식제분 모두에서 손상전분 함량이 높고 수분 흡수력과 호화 점도의 특성 변화가 심하여 쌀가루로 분쇄하는 제분 적성이 좋지 않았다.

Rice varieties in relation to rice bread quality

It is difficult to predict rice bread quality only from the amylose content (AC) or dough characteristics of new lines produced by rice breeding programmes. This study investigated the AC relative to bread baking quality of rice varieties developed in Korea, and identified specific characteristics that contribute to rice bread quality. Manmibyeo, Jinsumi, Seolgaeng and Hanareumbyeo were classified as low AC, YR24088 Acp9, Suweon517, Chenmaai and Goamibyeo as intermediate AC and Milyang261 as high AC. Suweon517, Milyang261 and Manmibyeo had a high water absorption index (WAI), while Goamibyeo, YR24088 Acp9, Jinsumi, Seolgaeng, Hanareumbyeo and Chenmaai had a low WAI. The gelatinisation enthalpy of flour varied from 9.2 J g(-1) in Milyang261 to 14.8 J g(-1) in YR24088 Acp9. After 7 days of storage the rate of flour retrogradation and crumb firmness were weakly correlated, with the exception of Jinsumi. Bread volumes of Jinsumi, Chenmaai, YR24088 Acp9 and Goamibyeo were comparable to that of wheat flour, but the rest were unsuited to bread making because of their low volume and hard crumb texture. Based on volume, texture and crumb firmness ratio, Chenmaai and Goamibyeo were the most appropriate varieties for making bread. An intermediate AC and low WAI were the primary indicators of rice bread flour quality.

Effects of the addition of hemp powder on the physicochemical properties and energy bar qualities of extruded rice

Extruded rice/hemp mixtures were prepared by mixing defatted and whole hemp powders with rice flour at varying hemp levels (0%, 20%, 30% and 40%). The influence of hemp powder type and level on physicochemical and antioxidant properties was studied. The bulk densities of the extruded rice/hemp samples increased with increase in levels of added hemp powder. The extrudates blended with hemp powder had a lower water absorption index than the control (extruded rice without hemp). The extruded rice/whole hemp had more total phenolics and flavonoids and had a better scavenging effect on DPPH radicals than extruded rice/defatted hemp. The highest potential to inhibit β-carotene oxidation was found in extruded rice/40% whole hemp. Increasing amounts of hemp powder resulted in lower equilibrium moisture content of energy bars. The energy bar made with extruded rice/20% whole hemp was preferred for colour, taste and overall acceptability.

Particle size of milled barley and sorghum and physico-chemical properties of grain following extrusion

Milled barley and sorghum grains were separated into three size fractions (fine, <0.5 mm; medium, 0.5–1.0 mm; coarse, >1.0 mm) and extruded at two maximum temperatures (100 °C; 140 °C). Mechanical resistance and specific mechanical energy during extrusion was significantly higher for fine fractions, and extrusion at high temperature resulted in higher mechanical resistance. Pressure generated during extrusion was higher for the fine fraction in sorghum but lower in barley. Expansion index was highest for the fine fraction for barley, but did not differ significantly between sorghum fractions or with extrusion temperature. For all samples, extrusion at low temperature resulted in a higher final paste consistency and lower water absorption index, but there was no significant effect on water solubility index (WSI). Fraction size showed a significant effect on WSI in sorghum but not in barley. The results are rationalised in terms of differences in grain composition between sorghum and barley.

EFFECTS OF STARCH, LIPID AND MOISTURE CONTENTS ON EXTRUSION BEHAVIOR AND EXTRUDATE CHARACTERISTICS OF RICE‐BASED BLENDS PREPARED WITH A VERY‐LOW‐COST EXTRUDER

ABSTRACT Response surface methodology with a 3 × 3 factorial plan design was used to investigate the effects of starch content (60–70 g/100 g dry matter [DM]), lipid content (6.2–10.2 g/100 g DM) and moisture content (10–16 g/100 g wet matter [WM]) on extrusion behavior of rice‐based blends, on the physicochemical properties of extrudates, and the apparent viscosity of resulting gruels. The increase in starch content increased the loss of lipid, the expansion ratio, the degree of gelatinization (DG) of starch, and the water absorption index (WAI). Increasing lipid content resulted in higher loss of lipids and a lower WAI and water solubility index (WSI). Water content had the most influence. Increasing water content resulted in increased loss of lipids, higher moisture content of extrudates, and in lower die temperature, expansion ratio, DG, WAI and WSI. The high DG (≥91%) of all extrudates demonstrated that the very‐low‐cost extruder manufactured in Vietnam is suitable for the production of ready‐to‐eat infant flour.PRACTICAL APPLICATIONSThis work tested and optimized the effect of blend composition on the characteristics of rice‐based extrudates obtained using a very‐low‐cost extruder (VLCE) manufactured in Vietnam and on derived gruels. Our results enable prediction of the characteristics of extruded products, when the starch, lipid and water contents of the blends are known. Thus, VLCE users will be able to choose the nature and relative proportion of ingredients to obtain extrudates with specific targeted characteristics. In addition, this study demonstrated that serious loss of lipids occurs during extrusion of blends with high lipid contents. To obtain the lipid content recommended for complementary food, it is thus preferable to add ingredients with high lipid content after extrusion. We conclude that this kind of VLCE manufactured in Vietnam is suitable for low‐cost production of instant flour with all the required characteristics for use as complementary foods for infants and young children after the age of 6 months.

Crystallinity and Rheological Properties of Pregelatinized Rice Starches Differing in Amylose Content

AbstractThree rice starches with different amylose contents (Glutinous: 1.4%, Jasmine: 15.0% and Chiang: 20.2%) were pregelatinized in a double drum dryer at 110, 117 and 123°C. Starch crystallinity was determined by X‐ray diffractometry and Fourier transform infrared (FTIR) spectrometry. Rheological properties were assessed by a Rapid Visco Analyser (RVA) and rheometer. Pregelatinized starches obtained from Glutinous (PGS) and Jasmine rice (PJS) gave an RVA pasting profile with cold peak viscosity. At drum temperature 110°C, PGS and PJS showed X‐ray patterns that were indicative of amorphous structures. However, pregelatinized Chiang rice starch (PCS) exhibited RVA hot peak viscosity and the presence of an amylose‐lipid complex with remaining granule structure. The PCS had a lower water absorption index (WAI) and water solubility index (WSI) than PJS and PGS. After pregelatinization at increased drum temperature (117, 123°C), the PGS had a lower WAI, whereas PCS showed an opposite trend indicating lower degree of granule disruption. In addition, the cold peak viscosity of PGS and PJS decreased with increasing drum temperature. For all drum temperatures, the apparent viscosity at 25°C for PGS and PJS decreased with increasing shear rate, indicating shear‐thinning behavior.

Resistant starch production from mango starch using a single‐screw extruder

AbstractResistant starches were prepared from mango starch by extrusion. An experimental design with independent variables temperature, screw speed and moisture content produced 20 samples that were studied to determine the effect of these variables on resistant starch (RS) content, water absorption index (WAI) and water solubility index (WSI). RS content was affected by moisture content and temperature. Screw speed and temperature also influenced RS content, the highest level (97 g kg−1) being obtained at low screw speed and high temperature, this pattern can be associated with a longer residence time, which gives rise to more opportunity for amylose chain association. The regression model fitted to the RS experimental results showed a good correlation coefficient (0.80). When moisture content and temperature decreased, WAI increased (105–142 g kg−1), but low WAI values (70–77 g kg−1) were obtained at moisture contents between 200 and 300 g kg−1 and high temperatures (140–150 °C). When moisture content and temperature increased, WSI increased (222–332 g kg−1), but at high temperature value (120 °C) assayed and the lowest moisture content (150 g kg−1), WSI also increased. In the range of moisture contents tested and at low temperatures, only partial gelatinisation occurred and low solubility was obtained. Copyright © 2005 Society of Chemical Industry

The effect of extrusion conditions on the functional and physical properties of wheat-based expanded snacks

The effect of extrusion conditions, including feed rate (20–32 kg h −1), feed moisture content (14–22%), screw speed (180–320 rpm), and barrel temperature (100–140 °C) on the functional properties (density, expansion, water absorption index (WAI), and water solubility index (WSI)) and physical properties (density, expansion and textural characteristics) of an expanded wheat snack was investigated. Increasing feed rate results in extrudates with a higher hardness and lower energy to puncture the samples. Increasing feed moisture content results in extrudates with a higher density, lower expansion, lower WAI, higher WSI, higher hardness and lower puncture energy. Increasing screw speed caused slight reduction of density and hardness of wheat extrudate. Higher barrel temperature reduced density, WAI, and hardness, but increased the WSI and puncture energy of extrudate.

Extruding Foams from Corn Starch Acetate and Native Corn Starch

Because of the hydrophilic characteristics of native starch foams and the cost of modifying starch, the uses of starch and modified starch foams are hindered. To decrease hydrophilicity and cost of starch foams, native corn starch was blended with starch acetate and extruded. A twin-screw mixing extruder was used to produce the foams. Native starch content, screw speed, and barrel temperature had significant effects on molecular degradation of starches during extrusion. The melting temperature of extruded starch acetate/native starch foam was higher (216 degrees C) than that for starch acetate (193.4 degrees C). Strong peaks in the X-ray diffractograms of extruded starch acetate/native starch foam suggested new crystalline regions were formed. Optimum conditions for high radial expansion ratio, high compressibility, low specific mechanical energy requirement, and low water absorption index were 46.0% native starch content, 163 rpm screw speed, and 148 degrees C barrel temperature.

Extrusion of Regular and Waxy Barley Flours for Production of Expanded Cereals

ABSTRACTGrains of two regular and two waxy barley cultivars were milled into break and reduction stream flours using a wheat milling mill, granulated to facilitate feeding and flow through the barrel, and extruded to form expanded products using a modified laboratory single‐screw extruder. As moisture content of barley granules decreased from 21 to 17%, the expansion index of extrudates increased from 1.81 to 2.68, while apparent modulus of compression work (AMCW) decreased from 17.1 × 104 to 7.8 × 104 N/m2. Break stream flours of both regular and waxy barley produced extrudates with higher expansion index (2.72–3.02), higher water absorption index (WAI), and lower AMCW than extrudates from reduction stream flours. Extrudates produced from regular barley had generally higher expansion and lower density than those produced from waxy barley. The specific mechanical energy (SME) was greater during extrusion of regular than of waxy barley. Barrel temperatures of 130, 150, and 170°C for the feeding, compression, and metering sections, respectively, resulted in higher SME, higher expansion index, lower water absorption index and lower AMCW of extrudates compared with a constant extruder barrel temperature of 160°C. Increased screw speed generally resulted in larger expansion index and increased WAI of extrudates. With increased feed rate from 89 to 96 g/min, the expansion index of extrudates decreased from 3.20 to 2.78 in regular barley and 3.23 to 2.72 in waxy barley, and harder extrudates were produced.

Extrusion-cooking of cassava starch as a pre-treatment for its simultaneous saccharification and fermentation for ethanol production

Single screw extrusion of cassava starch was evaluated as a pre-treatment for the enzymatic hydrolysis of the extrudate and fermentation to yield alcohol. The acid concentration, barrel temperature and moisture content showed that all the variables were significant. Increasing acid concentration or barrel temperature induced starch depolymerisation with a higher water solubility index and lower water absorption index. At 20 and 24% moisture contents the cold paste viscosity decreased. As a result of the addition of acid during extrusion cooking the degree of starch hydrolysis resulted in low hot paste viscosity. Acid concentration was significant in the production of reducing sugars. At concentrations above 0.024 N, as the temperature increased, the reducing sugar content also increased. Nevertheless, at concentrations below 0.024 N, the reducing sugar content showed the opposite result. The best yield of alcohol obtained from the extruded starch was 98.7% (0.56 g of ethanol/g starch), which, on average, ...

Effect of processing conditions on some functional characteristics of extrusion‐cooked cassava starch/wheat gluten blends

AbstractExtrusion‐cooked blends of cassava starch (CS) and wheat gluten (WG) were studied. The data were analysed using response surface methodology. The results showed the formation of new structures characterised by lower radial expansion (RE) and specific volume (SV) when gluten was added to CS. WG content was the most important variable affecting RE, water absorption index (WAI), water solubility index (WSI), SV and difference in colour (ΔE) of the extruded products, but feed moisture content and barrel temperature also influenced RE. WAI was affected by a significant interaction between WG content and barrel temperature. The extruded products had lower WAI values and higher WSI values than WG‐free products. Heat, high shear rate and high pressure during extrusion cooking caused mechanical destruction or denaturation of the WG and gelatinisation and dextrinisation of the starch components. The extruded blends could have diverse applications.© 2002 Society of Chemical Industry

The single screw extruder as a bioreactor for sago starch hydrolysis

Simultaneous pregelatinization and preliquefaction of sago starch with a thermostable α-amylase was carried out in a Brabender single screw extruder. Response surface methodology was employed to study the effects of processing conditions; feed moisture content (21–38%), enzyme concentrations (1.48–6.52%) and mass temperatures in the compression and die zones (70.5–97.5 °C), on the properties of the extrudates. Twenty runs were performed based on a multifactorial composite rotatable design. Changes in the dextrose equivalent (DE), water solubility index (WSI), water absorption index (WAI), degree of gelatinization (DG) and high performance size exclusion chromatography (HPSEC) profiles were assessed. From the HPSEC profiles, the degree of degradation (DGR) and oligosaccharide content were calculated. Feed moisture content and enzyme concentration were found to be the most significant variables affecting most of the measured physicochemical properties. Hydrolysis of starch granules was the fundamental reaction occurring during the extrusion process as indicated by the higher DE, WSI, oligosaccharide content and correspondingly lower WAI, DG and DGR. Product spectra from HPSEC showed that the amylopectin (Ap) was preferentially degraded and amylose (Am) was apparently protected. The predominant oligosaccharide species were G3, G5 and G6.