Physico-chemical properties of the flours and starches of two cowpea varieties (Vigna unguiculata (L.) Walp)

The physical and chemical properties of the starches and flours of whole grain and decorticated two cowpea varieties (Vigna unguiculata (L.) Walp) were investigated. The two cowpea varieties were: C-152-White, having big grain and S-1552-White, having small grain with black eye. Results showed that starch yields were 19.2 and 16.4 g/100 g grain for C-152 and S-1552, respectively. Statistical analysis shows that the total amylose contents of the starch of the two cowpea varieties were significantly higher (P ≤ 0.05) than that of the whole grain and decorticated flours. The swelling power of C-152 starch was significantly higher than that of S-1552 starch. The water-binding capacity (WBC) for S-1552 starch was higher than for C-152 starch. The results of pasting profile of both the flour and the starch showed that the two cowpea varieties possess different properties in relation to gelatinization temperature(GT), peak viscosity (PV), hot paste viscosity (HPV), cold paste viscosity (CPV), break down (BD), set back (SB), total set back (SBt) and relative breakdown (BDr). The information generated in this study on the properties of the starch could provide guidance on possible industrial uses of starches of these two varieties.Industrial relevanceThis work showed the peculiar characteristics (solubility, water-binding capacity, amylose content, carbohydrate composition, granules characteristics and behaviour in Brabender viscoamlograph) of pure cowpea starch. The results that we obtained could be very valuable in decision making for industries that want to take advantage of cowpea starch as alternative or supplement to cereal/tuber starch. Cowpea starch could be useful in the manufacture of thickeners, gelling agent, extenders and texture modifiers in food formulation.     

The use of the rapid visco analyser (RVA) to sequentially study starch properties in commercial malting barley (<Emphasis Type="Italic">Hordeum vulgare</Emphasis>)

The aim of this study was to evaluate the use of the rapid visco analyser (RVA) instrument as a tool to sequentially analyse barley (Hordeum vulgare) malting varieties in order to visualise and interpret the effect of amylose and amylose complexes on its pasting properties. The RVA sequential profiles derived from the barley samples analysed showed a large peak (peak viscosity, PV) at the start of each cycle alternating with viscosity troughs during the hot paste viscosity cycle. The sequential cycles caused a slight decrease in both PV and (final) FV values in all barley varieties analysed. The addition of silver nitrate to the barley flour samples tends to slightly increase the PV value independently of the time of the analysis. The development of this methodology will provide with better tools to study starch pasting properties as well as to study the interactions between amylose and amylopectin with other compounds in various malting varieties.     

Pasting characteristics of wheat flour-based batters containing cellulose ethers

The effects of type, molecular weight and concentration of cellulose ethers [methylcellulose (MC) and hydroxypropyl methylcellulose (HPMC)] on pasting properties of wheat flour-based batters were characterized using Brabender Visco-Amylograph. First, three types of cellulose ethers (A4M, E4M, and K4M) were studied. Addition of A4M (methylcellulose) had the strongest effect on pasting properties. There was no significant difference in hot paste stability (HPS) among types of cellulose ethers. Next, MC (1 g/100 g flour) with three distinct numbers average molecular weight (M_n) was further studied. M_n of MC did not affect pasting temperature (PT) and HPS. Conversely, M_n increase up to 41,000 resulted in higher paste viscosity values. Additionally, increase in the concentration of MC resulted in lower PT and higher paste viscosity values; with the exception of viscosity after holding period of slurries containing A4M, which were not significantly different. Only HPS of slurries containing A15 decreased with increase in the concentration.     

Pasting behaviour, textural properties and freeze-thaw stability of wheat flour-crude malva nut (Scaphium scaphigerum) gum system

The effect of replacement of crude malva nut gum (CMG) at 0%, 2.5%, 5%, 7.5% and 10% w/w on pasting behaviour, textural properties and freeze-thaw stability of wheat flour was investigated. Replacement of wheat flour by CMG significantly elevated (p < 0.05) the peak viscosity (128-669 RVU), hot paste viscosity (77-363 RVU), breakdown (51-306 RVU) and final viscosity (157-557 RVU) of wheat flour pastes. Pasting temperature (59-85 °C) of the flour decreased with increasing CMG content. The textural parameters including hardness, springiness, cohesiveness, gumminess and chewiness of the mix gels decreased with higher level of CMG. Freeze-thaw stability measurement revealed that wheat gel mixtures containing higher level (7.5% and 10%) of CMG decreased syneresis more than 80% after 3 freeze-thaw cycles, when compared to non-CMG sample. The rate of syneresis depended on CMG concentration and number of freeze-thaw cycles. The results demonstrated that higher viscosity, softer texture and lower syneresis of wheat gel could be attained using CMG.     

Pasting,thermal, gel texture,resistant starch and colour properties of unripe banana flour from 10 desert banana varieties cultivated in South Africa

Unripe banana flour is a potential commercial ingredient in various food products for increased resistant starch and reduced gluten contents. In the present study, the pasting (rapid visco-analysis), gel texture (penetration test), thermal (differential scanning calorimetry), colour (tri-stimulus colour indices) and the resistant starch properties of unripe banana flour produced from different dessert banana varieties (n?=?10) cultivated in South Africa, were analysed and juxtaposed to wheat and maize flour. The functional properties varied significantly (p?≤?0.05) between banana varieties, and from wheat and maize flours, to various extents. Selected functional property ranges of unripe banana, wheat and maize flours, respectively included; flour colour index (63.16–76.42, 77.34 and 80.96), paste viscosity (405.5–556.6, 124.7 and 115.6 RVU), gelatinization temperature (64.67–71.21, 71.11 and 69.95?°C), gel firmness (7.24–11.44?×?10^??2 N, 3.49?×?10^??2 N and 6.56?×?10^??2 N) and resistant starch content (19.9–47.4, 2.8 and 2.2% w/w). Multivariate analysis (principle component analysis) showed that the unripe banana flours from different varieties were distinguished from each other based on the pasting temperature. The unripe banana flours were distinguished from both wheat and maize flour based on breakdown and peak paste viscosities. The breakdown viscosity was the most positively related measure to the resistant starch content with a linear regression R-squared value of 0.898, indicating a significant role played by granule structure in resistance to enzymatic hydrolysis. The present research demonstrates that selection of appropriate dessert banana variety is important when replacing staple flours (wheat and maize) with unripe dessert banana flour as a functional ingredient.     

The effect of rice variety and starch isolation method on the pasting and rheological properties of rice starch pastes

The effect of rice variety and starch isolation method on the pasting and rheological properties of rice starches was evaluated. One waxy and three non-waxy rice varieties from California with a range of amylose contents of 1.6–26.5% and four methods of isolation were evaluated. A rotational rheometer (RR) was used to measure the pasting and rheological properties of starch dispersions (8% w/w). The RR pasting curves had similar shapes to those from a rapid visco-analyzer (RVA). The four treatments used for isolating starch were a protease, NaOH (0.1% and 0.4%), or sodium dodecyl sulfate (SDS) (1.0%). The NaOH (0.4%) and SDS treatments were found to reduce the peak pasting temperatures of the non-waxy starches as compared with the protease and NaOH (0.1%) treatments. The same trend of the treatments was found with the elastic moduli, low shear viscosities, and yield stresses of the non-waxy starch pastes measured at 65 °C, immediately after pasting. The elastic moduli of the waxy starch pastes appeared to be least affected by method of starch isolation, but the low shear viscosity and yield stress of the protease starch paste was significantly higher than the paste from the other three treatments. Overall, the method of rice starch isolation was found to affect the gelatinization and rheological characteristics of hot rice starch paste.     

Physicochemical characteristics of starches and flours from cassava varieties having different cooked root textures

Starches and flours from 12 cassava varieties having differences in cooked root texture - mealy, firm and mealy & firm - were investigated, with a particular focus on aspects of physicochemical characteristics. It was found that chemical composition (protein, lipid, fiber, ash), pasting properties, firmness of gel, thermal properties, morphology and granular size distribution and crystalline pattern of starches from the 12 varieties were not significantly different. On the contrary, cassava flours which consisted of both starch and non-starch components exhibited wider variations in these properties, especially pasting properties and firmness of gel, than the starches. All flour samples had lower paste viscosities than their corresponding starches. Pasting temperatures of flours were in a range of 70-74 ^°C, which was higher than those of starches (67-70 ^°C). Fluctuation in the values of pasting parameters of flours among the varieties was associated with the variations in the chemical composition and α-amylase activity, i.e. paste viscosity and setback were positively correlated to starch content and negatively correlated to α-amylase activity, while protein, lipid and fiber did not show correlation with pasting parameters. Cassava starches from all varieties, except the F-18 variety, had higher firmness of gels than their corresponding flours. Firmness values (except the F-18 variety) of starches were in a range of 149-207 g, whereas those of flours were 75-163 g. Firmness of flour gels was negatively correlated to lipid and fiber content, while strong positive correlation was found with the amylase activity.     

Quality Evaluation of Maize Chips (Kokoro) Fortified with Cowpea Flour

Quality evaluation of “kokoro” fortified with cowpea flour (0, 10, 20, 30, and 40 %) was studied. The blends were reconstituted into a thick paste, manually moulded into kokoro stick and deep fried in hot vegetable oil at about 170°C for 5 minutes. These flour blends were analyzed for pasting, proximate and functional properties. The result showed that there was significant difference (p < 0.05) in the proximate composition in all the bends. The protein content ranged from 15.20 – 23.03% while ash content was between 1.29 – 1.90%, which increased with increase in cowpea flour. The carbohydrate, fat and fiber contents decreased with values ranging from 59.17 – 65.00%, 3.24 – 4.40% and 2.23 – 2.96%, respectively. The pasting characteristics of the maize cowpea blends gave a peak viscosity ranging from 510 – 702 cp. There was no significant difference (p > 0.05) in the pasting time and temperature. The functional properties reflected that water absorption, oil absorption and foaming capacity significantly increased with increase in cowpea flour with their values ranging from 186.67 – 210.00 g/100 g, 163.33 – 195.00 g/mg and 30.73 – 39.27% respectively. Bulk density also followed the same trend. Sample CAF (100% maize) reflected the highest dispersibility value (6.63%). No significant difference (p > 0.05) was observed in the swelling capacity and least gelatinization concentration. Although the sensory result indicated that increase in cowpea flour does not show a significant difference (p > 0.05) in the sensory parameters, the overall acceptability of the samples was highly rated.     

Use of Rapid Visco Analyser (RVA) for measuring the pasting characteristics of wheat flour as influenced by additives

The influence of additives on the pasting characteristics of wheat flour was measured using a Rapid Visco Analyser (RVA) by making use of two different quality wheat flours. Incorporation of potassium bromate or ascorbic acid did not influence the pasting characteristics. Reducing agents like L -cysteine hydrochloride however, reduced the peak viscosity from 263 to 255 RVU when 0.060 g kg⁻¹ was added. On the other hand, the reduction in the peak viscosity was 79.03% in weak flour having a protein content of 81 g kg⁻¹ and a falling number of 545 s as compared with 49.0% for medium strong flour having a protein content 108 g kg⁻¹ and a falling number of 426 s when 1 g kg⁻¹ fungal α-amylase was used. Use of this enzyme reduced the cold paste viscosity, breakdown and total setback value in both the flours but to a greater extent in weak flour than in medium strong flour. Sodium stearoyl lactylate (SSL) increased the peak viscosity as well as hot paste viscosity in both flours. Emulsifiers like glyceroyl monostearate (GMS) or surfactants like sodium stearoyl lactylate (SSL) or diacetyl tartaric acid esters of monoglycerides (DATEM) alter the pasting properties of flour. Of the surfactants, greater change was observed with SSL followed by GMS and DATEM, of the flours, the weak flour responded more than the medium strong flour. © 1999 Society of Chemical Industry     

蜡质玉米粉的糊化特性研究

为了解蜡质玉米粉及其不同制粉方法对糊化特性的影响,测定了干磨、湿磨、挤压制蜡质玉米粉以及蜡质玉米淀粉、糯米粉的溶胀度和RVA参数。结果表明:蜡质玉米粉糊化进程中溶胀度高,水合能力强,具有较高的糊化参数。不同品种蜡质玉米粉的破损值、谷值、峰值和终黏度的变异程度较大,蜡质玉米粉的峰值与谷值、终粘度和回生值、谷值与回生值、谷值与终粘度、终粘度与回生值均呈极显著正相关。湿法制粉糊化进程中水合能力强,主要RVA参数显著高于干法制粉和挤压制粉,具备很强的成糊能力和黏滞性,干法制粉成糊后稳定较好,抗老化性较强,挤压制粉的糊化进程不明显。     

关中小麦品种籽粒糊化特性研究

以参加陕西省关中小麦品种区域试验的15个小麦品种(品系)为材料，研究了全麦粉、小麦粉和淀粉的粘度参数和膨胀体积，及各参数间的相关性。结果表明：样品不同处理形式和添加AgNO3对糊化特性有较大影响。全麦粉与小麦粉峰值粘度呈极显著正相关；加AgNO3小麦粉与淀粉、加AgNO3全麦粉的峰值粘度显著正相关。小麦粉与全麦粉的膨胀体积呈显著正相关，但淀粉与小麦粉、全麦粉的膨胀体积不相关。全麦粉和淀粉的膨胀体积与其粘度参数不相关；小麦粉膨胀体积与其峰值粘度、冷糊稳定性、热糊稳定性呈极显著或显著正相关；加AgNO3小麦粉膨胀体积与其回生值呈显著正相关。以全麦粉、小麦粉和淀粉的膨胀体积和粘度参数进行聚类分析，结果表明：不同处理形式下所得小麦品种聚类结果并不一致。这说明，小麦籽粒中其它组分或样品粒度对淀粉糊化特性有重要影响。     

Use of Seed Sprouting in Modification of Food Nutrients and Pasting Profile of Tropical Legume Flours

The study investigates the effect of seed sprouting on minerals, anti nutrients and pasting characteristics of flours produced from some tropical legume seeds. Samples were collected from cowpea (Vigna ungulculata); red kidney beans (Phaseolus vulgaris), and Pigeon pea (Cajanus cajan) and each sample was divided into two portions. A portion was sprouted while the other portion served as the control. The flours from sprouted and non-sprouted seeds were analyzed for the minerals, anti nutritional and pasting properties. The samples were found to differ significantly (p < 0.05) in the minerals, anti nutritional composition and pasting properties of the flours. Sprouting increased the mineral contents of the flours generally the calcium content of non-sprouted red kidney beans (13.8 mg/100 g) increased to 16.1 mg/100 g in the sprouted flour. The haemagglutinin decreased from 40.6 HU/mg in non sprouted red kidney to 6.4 HU/mg in the sprouted. The final viscosity of the non sprouted flours were higher than those of the sprouted, with non sprouted cowpea scoring the highest, 272 RVU, while sprouted red kidney beans had the least, 109.06 RVU, which implies that sprouting caused a reduction in the gel strength and elasticity of the samples. Seed sprouting effectively increased the mineral nutrients and lowered the anti nutrients, but produced steamed paste with poor gel strength.     

Effect of hydrocolloids on the rheological, microscopic, mass transfer characteristics during frying and quality characteristics of puri

Effect of hydrocolloids such as guar gum (GG), arabic gum (AG), carrageenan (CG), locust bean gum (LBG), xanthan gum (XN), hydroxypropyl methylcellulose (HPMC) and carboxymethylcellulose (CMC) at 0.5% w/w level on rheological and quality parameters of puri from whole wheat flour was studied. Hydrocolloids like CMC, XN and HPMC increased the water absorption of puri dough, while it decreased in all other samples. The dough development time and mixing tolerance index values increased, while dough stability did not get affected. On addition of hydrocolloid, there was a reduction in the pasting temperature, while the peak viscosity, hot paste viscosity and cold paste viscosity values increased. Hardness, cohesiveness and adhesiveness properties of the puri dough increased with the addition of hydrocolloids. All the hydrocolloids used in general helped in retention of moisture in the puri and hence remained softer and pliable, while there was a significant reduction in the oil content of puri samples containing hydrocolloids. Among the different hydrocolloids used, addition of guar gum at 0.5% w/w level led to puris having improved quality characteristics to a greater extent with respect to moisture retention, lowering of oil content upon frying with softer and pliable texture and better keeping quality. The mass transfer studies confirmed that the mass transfer co-efficient values for moisture loss and oil uptake were lower in puris with guar gum than control.     

蛋白组分对籼米粉糊化特性的影响机理探讨

通过逐一去除蛋白组分的方法研究了蛋白组分对籼米粉糊化特性的影响,并分析了影响这些变化的蛋白结构基础。RVA和DSC分析结果表明,不同组分的蛋白在去除之后,峰值粘度、热糊粘度和最终粘度均有不同程度的升高,崩解值、回生值及糊化温度均有不同程度的降低。SDS-PAGE和显微结构分析表明,各组分对糊化特性的影响机理应有差异:谷蛋白通过与纤维素类物质的紧密结合,在糊化过程中阻碍淀粉粒的溶胀;醇溶蛋白可能是通过蛋白体自身的溶胀与淀粉相互作用而影响;清、球蛋白通过活性蛋白对籼米成分的水解或合成等改变而影响;淀粉粒结合蛋白则可能对籼米的基础糊化特性影响较大。与分离重组法比较,逐一去除蛋白组分的方法因为蛋白组分之间的相互作用影响较大,对糊化特性的影响与分离重组法略有差异。     

Effect of steaming on the rheological characteristics of wheat flour dough

 The effect of steaming on the various rheological characteristics of wheat flour dough was studied. Steaming of flours at atmospheric pressure for 15 min completely denatured the gluten and reduced the water absorption capacity from 58.4% to 45.0%. Even steaming for just 5 min increased the resistance to extension considerably from 500 BU (Brabender Units) to 1000 BU and the ratio figure (resistance to extension/extensibility) from 4.2 to 27.4, indicating stiffening of the dough. The dough made from steamed flour had a higher hardness value of 91.1 N than the dough made from raw wheat flour which had a value of 51.1 N. The pasting characteristics of flour steamed for 15 min measured in a Rapid Visco Analyser showed increased peak viscosity from 218 rapid visco units (RVU) to 257 RVU as well as increased cold paste viscosity from 175 RVU to 200 RVU and increased hot paste viscosity from 94 RVU to 108 RVU for flour steamed for 15 min. Received: 4 August 1998 / Revised version: 23 October 1998     

Effect of blending of raw and steamed wheat flour on the rheological characteristics of dough

 The blended dough made from raw wheat flour and wheat flour steamed for 15 min at a ratio of 1 : 1, along with minor ingredients (salt, oil) showed reduced farinograph water absorption capacity. The stability of the blended dough with oil was reduced while the mixing tolerance index increased. The inclusion of salt in the blend increased the resistance to extension and also the area under the curve. The hardness and cohesiveness measured by means of texture profile analysis decreased with the inclusion of oil in the blend, while increasing with the addition of salt. The Rapid Visco Analyser used to measure pasting characteristics showed a peak viscosity which increased for the blend with salt, but decreased for that with oil. Similarly, the hot paste viscosity, cold paste viscosity and area under the curve increased for the blend with salt, but decreased for the blend with oil. Received: 5 February 1999 / Revised version: 21 April 1999     

Effects of hydrothermal treatment on the physicochemical properties of pregelatinized rice flour

Effects of hydrothermal treatment on the pasting, thermal and hydration properties of rice flour prepared from three Indica varieties of milled rice [Taichung Sen Glutinous (TCSW) 1, Taichung Sen (TCS) 10, and TCS 17], which contained 1.2, 17.9 and 28.8% amylose, were studied. Three hydrothermally-treated factors, soaking time, steaming temperature and steaming time were investigated. From the statistical results of an experimental design of L₂₇ orthogonal array, the soaking time is a significant factor that affects the pasting properties of three varieties of rice with various degrees of influence. However, the increase of pasting temperature, reduction of peak viscosity and elevation of final viscosity were investigated for all treated non-waxy rice and resulted in the reduction of its breakdown and total setback. The differences of pasting and hydration properties of treated rice flour were attributed to the changes of rigidity of starch granules under treatment. The results of DSC showed that the degree of gelatinization was higher in waxy rice than in non-waxy rice when subjected to the same hydrothermal conditions.     

Effect of fertiliser on functional properties of flour from four rice varieties grown in Sri Lanka

BACKGROUND: Fertiliser is an essential agro‐chemical input in modern rice farming. Fertiliser affects the grain quality and yield of rice. Although much research has been carried out to investigate the influence of fertiliser (recommended NPK addition) on yield and quality of rice grain, little is known about the effect of fertiliser on thermal, pasting, gelling and retrogradation properties of rice flour. The aim of this study was to investigate the influence of recommended fertilisation on functional properties of rice flour from four popular high yielding rice varieties grown in Sri Lanka. RESULTS: Fertiliser (recommended NPK addition) increased the protein content but reduced the apparent amylose content in rice flour except in BG 357. Swelling power and amylose leaching of rice flour were also increased. Pasting onset temperature, cold paste viscosity and setback were increased but peak viscosity and granular breakdown decreased. In response to the fertiliser application, gelatinisation peak temperature was reduced in all varieties except BG 300. However, compared to pasting properties, gelatinisation parameters were not much affected by fertilisation. The extent of amylopectin retrogradation was decreased by fertiliser in BG 305 and BG 352 but unchanged in the other two varieties. Except in BG 305, fertiliser reduced the gel hardness of rice flour but increased the gel cohesiveness. CONCLUSION: It is apparent that the increased protein and reduced amylose content caused by fertiliser affect the functional properties of rice flour. Copyright © 2011 Society of Chemical Industry     

Physicochemical properties of rice flour as affected by alkaline soaking and washing treatments

Effects of alkaline [NaOH, saturated Ca(OH)₂ and/or limewater] soaking and subsequent washing (with water vs. without washing) treatments on physicochemical properties of rice flour were investigated. Alkaline soaking treatment generally caused a loss of granule angularity but some birefringence was observed for unwashed alkali-soaked flour granules. After soaking, protein content of the flours significantly (P < 0.05) decreased but swelling power significantly (P < 0.05) increased compared to the control (soaked in water). The washed flours had lower protein content than unwashed flours (3.77–6.87% vs. 5.26–7.87%). The NaOH-soaking treatment yielded higher swelling power and solubility, respectively, for unwashed and washed flours. Alkaline soaking increased breakdown but decreased pasting temperature, trough viscosity, final viscosity and setback of the paste compared to the control. Compared to the control, hardness of soaked flour paste was lower due to lower final viscosity and setback. Overall, physicochemical properties of rice flour could be modified by alkali-soaking and washing treatments.     

Milling and flour pasting properties of waxy endosperm mutant lines of bread wheat (Triticum aestivum L)

Two waxy endosperm mutant lines, K107Wx1 and K107Wx2, derived from a bread wheat cultivar, Kanto 107, had a lower flour yield in test milling and a lower peak temperature in flour pasting measurement than their parent. Starch content in the kernel of waxy mutants was low, while fat and (1→3),(1→4)‐β‐D‐glucan content was high compared with cv Kanto 107, but protein content was similar for all of them. Waxy mutants had less α‐amylase activity than their non‐waxy parent, and had lower peak viscosity of flour paste in the pasting medium of water. A pasting test in silver nitrate solution increased peak viscosity in both waxy and non‐waxy flours. The viscosity of waxy flour paste rapidly increased above 60°C, while that of non‐waxy flour paste increased gradually at 60–80°C. The difference in pasting behaviour was attributed to the presence of amylose in starch granules. © 1999 Society of Chemical Industry