Effect of Milling Method (Wet and Dry) on the Functional Properties of Cowpea (Vigna unguiculata) Pastes and End Product (Akara) Quality

ABSTRACT: Akara, deep-fat fried cowpea paste, is a very popular snack and breakfast food in Africa. Traditional cowpea paste processed by wet-milling of soaked, decorticated seeds exhibited excellent foaming ability, high water-holding capacities (WHC), and low hardness value for akara. Intense dry-milling that generated a fine flour adversely affected its functionality and akara-making quality. Wet-milling of hydrated cowpea meal significantly improved its foamability (as indicated by reduction in specific gravity) and WHC but showed only a marginal improvement in akara texture.     

Effect of Hydration of Cowpea Meal on Physical and Sensory Attributes of a Traditional West African Food

Effects of water level (56, 58 and 60%) and hydration time (0, 30, and 60 min) on apparent viscosity of cowpea paste and physical-sensory attributes of akara, a finished food made from paste, were determined. Water level had a greater effect than hydration time on paste viscosity and on crude fat content, shear force, lightness (L), and saturation index (ΔE) of akara. Apparent viscosity of cowpea paste was the only parameter significantly affected by the interaction of water level and hydration time. Overall, the 60% water level produced paste with flow properties and akara with physical characteristics most like the traditional product. Sensory attributes of mealased products were acceptable.     

Puffing Effects on Functional Properties of Amaranthus paniculatas (Rajgeera) Seed Flour

Among functional properties studied, water- anf fat-holding capacities were higher for puffed grain flour. Gelation was not affected, while foaming was adversely affected by puffing. A decrease in viscosity of flour pastes also resulted due to puffing.     

EFFECT OF PROCESSING VARIABLES OF COWPEA (VIGNA UNGUICULATA) MEAL ON THE FUNCTIONAL PROPERTIES OF COWPEA PASTE AND QUALITY OF AKARA (FRIED COWPEA PASTE)

The importance of particle size distribution in conjunction with milling method (dry‐milled hammer‐milled meal [HM] or wet‐milled freeze‐dried meal [FD]) on the functionality of cowpea paste and textural characteristics of akara produced from dry meal was investigated. All meal samples contained a minimum of 65% by weight medium‐sized particles and different combinations of large and fine particles to compose the balance. With the exception of the pastes made from meal consisting of 35% fine particles, all pastes had good foaming ability and handling characteristics. However, akara made from the HM and FD blends with 35% large particles had hardness values not significantly different from the traditionally prepared (wet‐milled) akara (5.317, 4.048 and 5.341 N, respectively), indicating that the meal blends had the potential to produce akara acceptable to consumers.     

Effect of milling method on selected physical and functional properties of cowpea (Vigna unguiculata) paste

Particle size distribution (PSD) of cowpea meal is an important determinant of paste functionality and end product quality. Samples from various mills and screen sizes were used to determine PSD, water‐holding capacity (WHC) and swelling capacity (SWC). Hammer mill (1.73 mm screen) meal had a geometric mean diameter (d_gw) of 221 microns, whereas PM‐360 [plate mill with one complete turn (360°) of clearance] meal had a d_gw of 1559 microns. All other milling processes resulted in meal with an intermediate particle size. To reduce the particle size of cowpea pastes, cowpea meals were hydrated to pre‐determined moisture contents, held for 15 min, and then blended in a blender before whipping. Blending increased the WHC and SWC of all samples.     

Effect of saponins on the physical characteristics, composition and quality of akara (fried cowpea paste) made from non-decorticated cream cowpeas

Changes in the foaming capacity and viscosity of cowpea paste, affected by the addition of saponins, were investigated, as well as the subsequent effect on the texture and oil content of Akara (fried cowpea paste). Two saponins, Quillaja and Yucca, were used. Results showed a significantly greater decrease in the specific gravity after whipping (39.9-52.9%), of the paste prepared with saponins compared to that prepared without saponins (25.1-32.9%). This demonstrated the increase in foaming capacity of the paste prepared with saponins. The results also showed a higher foaming capacity for the Yucca saponin compared with the Quillaja saponin. Subsequently, there was a significant decrease in the apparent viscosity of the paste prepared with saponins and a decrease in the firmness (6.51-7.78 N) of the fried product compared to that prepared without saponins (10.89-11.58 N). These results suggest that saponins can be used to increase the foaming capacity of cowpea paste resulting in a more desirably soft, spongy-textured product. There was a significant increase in the fat content of the samples produced with saponins (25.1-42.0 g/100 g) compared to the control (18.8-19.6 g/100 g) due to the formation of more air spaces in the cowpea paste.     

Effect of Natural Fermentation on the Functional Properties of Protein-Enriched Composite Flour

The functional properties of a naturally fermented composite flour made up of 30% edible defatted groundnut flour and 70% sorghum meal were compared with conventionally fermented sorghum meal. Fermentation increased the nitrogen solubility of the composite flour in the alkaline pH region. The increased protein of the composite flour (23%) improved the functionality of the meal as reflected in its better water-absorption capacity, its water-retention capacity, and its fat-absorption capacity compared to values obtained with sorghum meal for the three functional properties, respectively. Natural fermentation resulted in the improvement of the water-absorption capacity of the composite flour but decreased its water-retention capacity and its fat-absorption capacity. The fermented composite flour showed better foaming capacity and emulsification capacity than fermented sorghum meal. Fermentation helped to stabilize the foaming properties of the composite flour; however, it did not improve its emulsion stability.     

VISCOSITY CHARACTERIZATION OF UNMODIFIED CASSAVA STARCH PASTE

Unmodified cassava starch paste was characterized on the basis of its paste viscosity as affected by drying, cooking, and paste temperatures at different paste concentrations The paste exhibited plastic fluid flow with high hot-paste peak viscosity. The temperature of the peak viscosity decreased with increasing concentration. Drying temperature had statistically significant effects on the paste viscosity; the higher the temperature at which the starch was dried, the lower was the paste viscosity over the levels of concentration and cooking temperature. Starch drying temperature and paste concentration significantly affected the paste stability as measured by freeze-thaw tests and paste retrogradation tendencies.     

Hydration of muscle proteins of Bombay duck (Harpodon nehereus) during acetic acid-induced gelation and characteristics of the gel dispersion

Washed fillets of Bombay duck (Harpodon nehereus), a fish having unusually high moisture content (above 90%), were held overnight in cold, 2% (v/w) aqueous acetic acid, which resulted in gelation associated with a 33% increase in weight due to water uptake by the proteins. Gamma irradiation at 3 kGy or repeated freezing and thawing did not affect protein hydration. The presence of sodium chloride in the acid adversely affected protein hydration. The effects of urea, dithiothreitol and o-phenanthroline on water uptake suggested that the imbibed water was held by non-covalent interactions with the fish proteins. Water homogenates of the gel had higher apparent viscosities than native muscle. Temperature significantly influenced the apparent viscosity of the gel. Unlike water homogenates of washed fish, heating of the gel dispersion at 100 °C did not cause precipitation of the proteins. However, the stability of the proteins in the dispersion was adversely affected by sodium chloride or by increase in pH above 5.0. The acid-induced gel was very weak; its hardness could be enhanced by incorporation of certain food additives.     

Rheological Characterization of Grain Legume Pastes and Effect of Hydration Time and Water Level on Apparent Viscosity

An extrusion capillary viscometer was employed to obtain shear stress-shear rate data of two types of cowpea pastes, traditional and experimental. The power law model was found to describe adequately flow behavior of the pastes with consistency coefficients of 77.45 and 59.02, and flow behavior indices of 0.456 and 0.458 for experimental and traditional pastes, respectively. Effect of hydration time (0 - 180 min) and water level (54 - 62%) on the apparent viscosity of experimental paste was determined by extrusion capillary and Brookfield viscometers with correlation coefficient of 0.953. Water level had a significantly greater effect than hydration time on apparent viscosity of cowpea paste.     

Rheological characterization and electrokinetic phenomena of charged whey protein dispersions of defined sizes

A multi-step processing technique produced large colloidal particles from whey proteins, prompting instantaneous thickening upon hydration. Analysis of the rheological characteristics and zeta potential of the modified whey suspensions of defined particle sizes allowed investigation into the role of size on ingredient functionality. Preliminarily, the modified protein powders were sieved to achieve three size ranges, and analyzes were conducted on each of the three distributions and the non-sieved fractions. Following hydration, steady and oscillatory shear analyzes were performed using a controlled stress rheometer to determine rheological characteristics. Intrinsic viscosity was determined with a capillary viscometer and application of the Huggins equation. Zeta potential was calculated from colloidal electrophoretic mobility, measured with a ZetaPALS analyser. After thorough hydration, particle-size analysis revealed a size increase of >1.3 times for each fraction. When analysed on a protein basis, increasing particle size yielded an increase to intrinsic viscosity, flow behavior index, zero shear viscosity, and a decreased zeta potential and consistency coefficient. Knowledge of the interrelationship between zeta potential, rheological properties, and particle size of the modified whey ingredient will further advance an understanding of the functionality of this protein ingredient.     

黑粒小麦76号的营养品质及其几个理化特性

分析了黑粒小麦７６号和我国春麦推广品种晋春九号及两个美国面包品种Ｋｌａｓｉｃ和Ｙｅｃｏｒａ的营养品质和几个理化特性。结果表明,黑粒小麦７６号的灰分、脂肪、蛋白质及必需氨基酸含量占总氨基酸含量的比例高于晋春九号和Ｋｌａｓｉｃ及Ｙｅｃｏｒａ,并且富含钙、磷、硒和脂溶性维生素ＶＫ。它的面筋含量高,但沉降值和面筋指数比Ｋｌａｓｉｃ和Ｙｅｃｏｒａ低,面筋强度差。其面粉膨胀体积比Ｋｌａｓｉｃ和Ｙｅｃｏｒａ小,     

Effect of saponins on the foam/flow properties of paste and physical characteristics of akara made from decorticated black‐eyed cowpeas

Akara, a deep‐fat‐fried cowpea paste product, is a popular snack food in West Africa. Foaming capacity of the cowpea paste is important for achieving a spongy light‐textured fried product. The effect of two saponins, Yucca and Quillaja, on the foaming capacity of cowpea paste was investigated. Results showed that an increase in the amount of saponin added (1, 2, 4%) resulted in a decrease in specific gravity and apparent viscosity of the cowpea paste. Addition of saponin also significantly reduced the firmness and increased the cohesiveness of the akara compared with the control. Akara made using the Quillaja saponin was less firm and more cohesive than akara made using the Yucca saponin. An increase in the amount of saponin added to the cowpea paste resulted in a darker (lower L*) and browner colour of akara. However, akara containing 1% Yucca saponin had similar colour attributes to the control but was less firm and more cohesive. Copyright © 2005 Society of Chemical Industry     

Influence of drier inlet temperature during pilot-scale manufacture of rennet casein on the hydration behaviour of the rennet casein in disodium orthophosphate solution

Rennet casein curds were dried in a pilot-scale fluidized bed drier at air-inlet temperatures of 80, 90, 110, 120 or 140°C. As the drier air-inlet temperature was increased, there was a significant increase in hydration time and a significant decrease in hydrated viscosity and viscosity stability following hydration of the dried rennet caseins in 0.4% (w/w) disodium orthophosphate (DSP). The influence of air-inlet temperature during drying on composition, the extent of Maillard reaction, the resolution of the proteins on urea–polyacrylamide gel electrophoresis (PAGE) and cation-exchange fast protein liquid chromatography (FPLC), the dialysability of calcium and phosphorous from a 6  m urea dispersion at pH 4.6, and the particle-size parameters of milled rennet caseins were determined. Relationships between all these latter parameters and the hydration behaviours of the rennet caseins in DSP solution were also studied. Results suggest that the increase in drier air-inlet temperature resulted in a reduction in the mean particle size of milled casein, which was significantly correlated to the changes in hydration behaviour. Hydration times increased significantly and hydrated viscosities decreased significantly with increasing levels of fluorescent Maillard reaction products (MRPs) and with increasing levels of nondialysable calcium and phosphorous in the caseins. It appears that the increase in air-inlet temperature during drying reduced the solubility of colloidal calcium phosphate (CCP), possibly through binding of CCP to the increased levels of MRPs. This change in CCP solubility led to increased difficulty in sequestering CCP from the curd when the pilot-scale rennet caseins were dispersed in the DSP solution, leading to the changes in hydration behaviour.     

Functional modification of vital wheat gluten with corn syrup using hydrothermal treatment

Functional properties of gluten modified using hydrothermal treatment were compared with those of vital wheat gluten (VWG). Gluten slurry was jet cooked under pressure in the presence of corn syrup (CS) at different temperatures (121 and 149 °C) for different times and then spray dried. Foaming properties for all samples (treated and untreated) at different pHs showed that, although the optimum pH was 5, at this pH the treated gluten samples displayed reduced foaming properties as compared with the control, whereas at all other pHs there was an increase in foaming properties. The sample treated with CS at 121 °C (JC121w/cs) showed the highest viscosity and elasticity increase among all treated samples. Emulsifying properties were adversely affected by an increase in temperature of treatment, whilst addition of CS helped to restore emulsion stability (ES). The sample VWG with CS (Cont.w/cs) at pH 3 showed maximum ES. In general, samples after treatment showed increased solubility. The hydrophilic but non‐ionisable sugar hydroxyl groups affected the functionality at lower pH. Molecular changes were followed by size exclusion high‐performance liquid chromatography (SE‐HPLC) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE). Samples subjected to the lower temperature (121 °C) showed a shift of the molecular weight distribution to higher values in the HPLC profile, consistent with higher viscosities for this treatment. For the same samples, SDS‐PAGE of the reduced protein exhibited a decrease in the intensity of bands corresponding to high‐molecular‐weight glutenin subunits, complementing the fact that large‐molecular‐size polymers are involved during protein modification. Copyright © 2005 Society of Chemical Industry     

Physicochemical and functional properties of barley β-glucan as affected by different extraction procedures

Four methods were evaluated for extraction of β-glucan from barley. Gum pellets obtained by respective methods were examined for yield, purity and various physicochemical and functional characteristics. Highest yield and recovery was found in samples that were extracted by hot water treatment. This method also removed the maximum impurities from gum pellets and contained highest amount of soluble fibre, while alkali-extracted sample contained highest amount of insoluble fibre. All samples contained an appreciable amount of calcium and phosphorus. Extracted pellets had good water retention and foaming capacity. A significant variation in extraction methods was observed with respect to water binding capacity and foaming capacity. However, the same level of foaming stability was observed in all extraction methods. Alkaline and acidic extraction methods adversely affect the viscosity properties of the samples. A significant affect of extraction methods was also observed on colour parameters of β-glucan. A negative correlation exists between foaming capacity and viscosity, whereas a positive correlation observed between soluble fibre and viscosity.     

泡沫涂层工艺制备功能性窗帘面料

采用泡沫涂层工艺制备具遮光阻燃和防静电等多功能窗帘面料,考察了氨水添加量、发泡比和填充材料对涂层浆性能的影响。结果表明,填充材料的添加量越大,遮光性越好;发泡比直接影响涂层产品的厚度和遮光性;冷轧工艺有助于提高泡沫涂层织物表面的平整性和遮光性能。优化的泡沫涂层浆处方为:每100g涂层浆加2滴氨水,填充材料TiO215%,发泡比1∶5,发泡稳定剂(硬脂酸胺)2%～3%,阻燃剂20%,抗静电剂1%。     

Effect of pH and the presence of NaCl on some hydration properties of collagenous material from trout (Salmo irideus Gibb) muscle and skin

Various hydration properties (solubility, water binding capacity and viscosity) of collagenous material from muscle connective tissue and skin are analysed in terms of pH and NaCl concentration in the medium. In general terms it is found that functionality is at its greatest where pH is between 2 and 4, and that the addition of NaCl reduces functionality, except in the case of viscosity. Both collagenous materials react similarly to changes deriving from pH and the addition of NaCl. The data are relevant to the possible utilisation of waste products from the fish industry as functional ingredients in other foodstuffs.     

Protein Nutritional Quality of Traditional and Novel Cowpea Products Measured by In Vivo and In Vitro Methods

Effect of processing on nutritional quality of cowpea meal protein was determined by in vivo and in vitro methods. Uncooked meal and meal which had been extruded at various temperatures and moistures; slurried, steamed, and drum-dried (SDP); and hydrated to a paste and deep-fat fried (akara) were studied. PER values of extrudates (1.81–1.97), and akara (1.89) were higher than those of raw meal (1.44) or steamed, drum-dried paste (1.63). The saturation kinetics model showed similar trends but differences were not significant. In vitro digestibility was highest for extrudates (83–85%), intermediate for akara and SDP (82.8%, 81.2%), and lowest (77.8%) for raw meal. C-PER/DC-PER gave differing and contradictory results.     

Rheological behaviour and colour changes of ginger paste during storage

Ginger paste was prepared from fresh ginger by addition of 8% common salt and citric acid. The paste was thermally processed and packed in glass, polyethyleneterephthalate or high‐density‐polyethylene containers and stored at 5 ± 1 and 25 ± 1 °C for 120 days. The rheological characteristics of the paste were studied by using a computer controlled rotational viscometer over the temperature range of 20–80 °C. Samples were subjected to a programmed shear rate, increasing linearly from 0 to 200 s^?1 in 3 min, followed by a steady shear at 200 s^?1 for 3 min and finally decreasing linearly from 200 to 0 s^?1 in 3 min. Ginger paste exhibited pseudoplasticity with yield stress and flow adequately described by the Herschel–Bulkley model. The yield stress decreased exponentially with process temperature and ranged between 3.86 and 27.82 Pa. The flow behaviour index (n) varied between 0.66 and 0.82 over the temperature range. Both consistency index and apparent viscosity decreased with increase in temperature and the process activation energies were found to be in the range of 16.7 to 21.9 kJ mol^?1. The effect of temperature was significant (P < 0.05) on the Hunter colour combination value of the paste during storage; however it was not affected by type of packaging material (P > 0.05). It is recommended that ginger paste is stored at 5 ± 1 °C in polyethyleneterephthalate or glass containers.