Certain functional properties of defatted pumpkin seed flour

Defatted pumpkin (C. pepo andC. maxima) seed flour has potential food uses because of its high protein content, 61.4±2.56%. The functional and electrophoretic properties of the defatted flour were investigated. Polyacrylamide gel electrophoresis and electrofocusing indicated 14 bands of water-soluble protein subunits with isoelectric points between 3.81–8.08 and apparent molecular weights between 19,200 and 97,000 daltons. Minimum nitrogen solubility was observed at pH values between 3.0–7.0 and exceeded 90% at pH above 9.0. Solubility was a function of ionic strength. It appeared that, even at the pH of minimum solubility, the pumpkin seed proteins could be dissolved up to high concentrations by increasing NaCl molarity. The viscosity of flour-water dispersion was affected by flour and salt concentrations, and temperature. The least gelation concentration was 8% (w/v) and the water and oil absorption 24.8±2.03 and 84.4±4.05 g/100 g respectively. Sorption isotherms, BET monolayer moisture and binding energy of sorption were also calculated. Both foam capacity and stability were pH dependent.     

Rheological properties of starches with different amylose/amylopectin ratios

The rheological properties of corn starches with different amylose/amylopectin ratios (80/20, 50/50, 23/77, and 0/100) were systematically studied by Haake rheometry. The starches were initially pre-compounded with water to designated moisture content levels using a twin-screw extruder. A single-screw extruder with a slit capillary die was then used to characterize the shear stress and melt viscosity characteristics of sample pellets, as a function of both moisture content (19–27%) and extrusion temperature (110–140 °C). The melts exhibited shear thinning behavior under all conditions, with the power law index (0 < n < 1) increasing with increasing temperature and moisture content in the majority of cases. The higher the amylose content, the higher is the viscosity (for example, η increases from 277 Pa s to 1254 Pa s when amylose content increases from 0% to 80% under a certain condition), which is opposite to the sequence of molecular weight; amylopectin-rich starches exhibited increased Newtonian behavior. These rheological behaviors are attributed to the higher gelatinization temperature of amylose-rich starches, and in particular the multiphase transitions that occur in these starches at higher temperatures, and the gel-ball structure of gelatinized amylopectin.     

Effect of the Extrusion on Functional Properties and Mineral Dialyzability from <Emphasis Type="Italic">Phaseolus Vulgaris</Emphasis> Bean Flour

The effects of extrusion conditions on cooking degree, flour dispersion viscosity and mineral potential availability of extruded bean flour were studied. Phaseolus vulgaris beans of the agronomic cultivar “Flor de mayo” were ground and dehulled to obtain grits and then extruded at different temperatures (140, 160 and 180 °C) and moisture contents (17, 20 and 23%), according to a bifactorial experimental design. Degree of cooking was estimated by water solubility (WS) and specific mechanical energy (SME). The effect of variables on WS and SME were analysed by surface response methodology. Flour dispersion viscosity and mineral availability (estimated by in vitro dialyzability), were also evaluated on selected samples. Results showed that, within the ranges of the variables used for this study, only the effect of temperature was significant on the degree of cooking. No direct correlation was observed between water solubility and SME, although a maximum value of WS corresponded to a range of SME values of 400–500 J/g was observed. Dispersion viscosity decreases as WS increases, so if high calorie density is desired, for instance in order to produce a cream soup formula, bean grits should be extruded at high temperature and as low moisture as possible, in our case 180 °C and 17% moisture. On the other hand, the effects of extrusion variables on iron and zinc dialyzability were not much affected.     

Quality evaluation of commercial chile-based salsas

A standardized extrusion cooking process was developed for production of a high protein weaning food based on peanuts, maize and soybeans. Major factors evaluated included the effects of blend formulation, extrusion temperature and feed moisture content on ease of extrusion and product quality characteristics. Results showed bulk density and hardness increased while expansion index decreased with increase in feed moisture content. At a fixed range of feed moisture content, product bulk density and firmness decreased while expansion index increased with increasing extrusion temperature. For ease of extrusion and best product quality in terms of sensory attributes and cooking properties, the following extrusion parameters were established for a blend formulation of 75% maize, 10% peanut and 15% soybean: feed particle size of 300–400 m extruded using a screw speed of 500 rpm, with a feed rate of 4.6 kg/min, feed moisture content of 16–18%, and extrusion temperature of 100 ,°C–105,°C. Pair-wise comparison of the sensory attributes of porridges prepared from milled samples of the weaning foods showed significant differences between extruded products and existing traditional counterparts, with very high scores for all sensory attributes of the extruded products, especially extruded raw (non-roasted) blend samples. In the Home-Use-Test, at least 92% of respondents in two out of the three major ecological zones of Ghana placed overall sensory and functional characteristics of extruded raw blend samples as highly acceptable. About 7% of respondents scored sensory and functional quality attributes as acceptable.     

Extrusion processing characteristics of quinoa (Chenopodium quinoa Willd.) var. Cherry Vanilla

Extrusion processing characteristics of Cherry Vanilla quinoa flour (Chenopodium quinoa Willd) were investigated using a three factor response surface design to assess the impact of feed moisture, temperature, and screw speed on the physicochemical properties of quinoa extrudates. Specific mechanical energy (SME) required to extrude this quinoa variety was higher (250–500 kJ/kg) than previously reported for quinoa. The following characteristics of the extrudates were observed: expansion ratio (1.17–1.55 g/cm³), unit density (0.45–1.02 g/cm³), water absorption index (WAI) (2.33–3.05 g/g), and water solubility index (WSI) (14.5–15.87%). This quinoa flour had relatively low direct expansion compared to cereal grains such as corn or wheat, suggesting that it is not well suited for the making of direct expanded products. The study further suggests that there is a need to understand the processing characteristics of new quinoa varieties for cultivation. Understanding extrusion and other quality traits in advance will help to select the appropriate varieties that would allow food processors to meet consumer needs.     

Sodium hydroxide and trimetaphosphate levels affect properties of starch extrudates

In addition to being consumed as food, starch is considered for replacement of petroleum-based plastics, but imparts negative effect like water absorption and solubilization in water. In this study, the effects of sodium hydroxide and sodium trimetaphosphate concentrations on the water absorption and solubility indices of starch cross-linked by sodium hydroxide and sodium were evaluated. Starch was granulated, and 0.3 kg granulated starch was mixed with 65 ml sodium hydroxide at three concentrations (0.2, 0.6, and 1.0 M), sodium trimetaphosphate at two levels (0.015 and 0.045 kg sodium trimetaphosphate corresponding to 5 and 15% of starch), and water to adjust moisture content to 40% (dry basis). The samples were extruded in a single-screw extruder at a barrel temperature of 130 °C and screw speed of 140 rpm. Phosphorus content and pasting viscosity of starch extrudates showed that starch was cross-linked with phosphorus that was incorporated into starch during extrusion. The extrusion and cross-linking of starch with 5% sodium trimetaphosphate reduced water absorption index, and increasing sodium trimetaphosphate percentage reduced water absorption index further at high levels of sodium hydroxide. On the other hand, the reduction in water solubility of starch extrudates required the extrusion of starch with more than 5% sodium trimetaphosphate, but increasing the sodium hydroxide level increased the water solubility index of extrudates.     

Effect of blanching and ripening on functional properties of plantain (Musa aab) flour

Flours were prepared from raw and blanched samples of and ripe mature plantain Musa aab and examined for theirproximate composition, physical characteristics and functionalproperties. The plantain flours contained 3.5 g crude protein,2.5–3.5 g crude fat, 5.7–7.1 g moisture, 1.33–2.0 g crudefiber, 1.66–2.0 g ash, and 82.25–86.07 g carbohydrate per 100 gsample. The flours had bulk densities between 0.42–0.72 g/ml,emulsion capacities of 4.7–14.7%, water absorption capacitiesof 250–338%, oil absorption capacities of 214–371%,foaming capacities of 1.90–5.79%, least gelation concentrationsof 6–8%, and viscosities of 23.7–46.7 CP at 2% slurry concentration. Foaming capacity increased with increasing flourconcentration. Blanching considerably reduced the emulsion capacity and viscosity, while bulk density, water and oilabsorption capacities were increased by blanching. Ripening wasfound to have a negative effect on all the functional propertiesexamined except the bulk density, and gelation property. Unripe plantain could be used as an emulsifier and thickener in a foodsystem.     

Triticale extrudates – Changes of macrostructure,mechanical properties and molecular water dynamics during hydration

The effect of hydration (in the range of aw 0.981–0.090) on changes of macroscopic and mechanical features of triticale snacks produced in different conditions (feed moisture - 16 and 20%; extrusion temperature - 135 and 175 °C) was analysed. Changes of snacks depended both on the hydration level and the extrusion process conditions.As a result of storage at the highest hydration level (aw = 0.981) contraction of snacks was observed. The shrinkage was more pronounced in case of extrudates obtained from raw material containing 16% of water regardless of the extrusion temperature. The hardness of extrudates depended both on the feed moisture and hydration. Samples obtained from the raw material containing 20% moisture were harder than those prepared at the feed moisture of 16%. Based on the results of molecular dynamics study by low field NMR technique, a model of hydration was developed and critical hydration value of extruded snacks was calculated. Higher values of the critical hydration were obtained for snacks extruded at temperature 135 °C than for those obtained at 175 °C. The feed moisture level affected critical hydration values to a lesser extent. Obtained results suggest that the state of water in extrudates depends on extrusion process conditions.     

Relationship between the glass transition temperature and the melt flow behavior for gluten, casein and soya

The effects of moisture content (25–45% wwb) and temperature (75–120 °C) on the viscosity of gluten, soya and rennet casein systems was studied using a capillary rheometer. An attempt was made to relate the viscosities to the glass transition temperature measured by differential scanning calorimetry, dynamic mechanical thermal analysis and the phase transition analyzer. The temperature where the material flowed was also determined by the latter technique. All three-protein systems showed shear and extension thinning. Over the shear rate range investigated (1–10³ s⁻¹), gluten had a substantially lower viscosity than the other two proteins, although the difference was less pronounced at the highest temperature studied. This low viscosity is reflected by lower values of the glass transition temperature, the melt flow temperature and the dynamic moduli E′ and E″ in the rubbery state. The results are discussed in terms of the structure and heat induced changes for the three proteins and their relevance to food processing considered.     

Cultivar and processing effects on the pasting characteristics,tannin content and protein quality and digestibility of cowpea (Vigna unguiculata)

Four popular West African local cultivars of cowpea (Vigna unguiculata), with distinctly different seed coat colors, were evaluated for their relative amylograph pasting characteristics, condensed tannin content, in vitro protein digestibility and Tetrahymena protein efficiency ratio (t-PER). The effects of roasting and dehulling on these properties were also determined. There were wide variations in the hot paste viscosity characteristics of the different cultivars studied. The raw cowpea flour samples exhibited maximum paste viscosities ranging between 260 Brabender Units (BU) for the Mottled cultivar and 460 BU for the cream-colored Blackeye cultivar. Cowpea cultivars with the greatest peak viscosities showed low stabilities to extended cooking. Roasting depressed paste viscosity properties of all the cowpea cultivars studied. Tannin concentrations were 0.3–6.9 and 7.2–116 mg CE/g flour from whole cowpea seeds and seed coats respectively, increasing with intensity of seed color. Although dehulling removed 98% of the tannin content of raw cowpeas, improvement in protein quality as a result of dehulling was observed for only the highly-pigmented Maroon-red variety. Roasting significantly improved digestibility and more than doubled the t-PER of all cowpea cultivars studied. Roasted cowpeas possess adequate nutritional and functional qualities as protein supplements in cereal-based weaning foods. However, it appears that dehulling is necessary to enhance the nutritional quality of the highly pigmented cultivars of cowpea.     

Determination of the Extraction,Physicochemical Characterization,and Digestibility of Sulfated Polysaccharides in Seaweed—Porphyra haitanensis

The aim of the study was to extract Porphyra haitanensis polysaccharides (PHPs) using the water extraction and alcohol precipitation methods and explore their antioxidant activity and physicochemical properties. The single-factor and Box-Behnken response surface methodologies were used to optimize the extraction of polysaccharides from Porphyra haitanensis. Our results showed that the polysaccharide yield was as high as 20.48% with a raw material to water ratio of 0.04, and extraction time of 3 h at 80 °C. The extraction rate observed was similar to the actual extraction rate, thus proving the reliability of the optimization model. The extracted polysaccharides primarily consisted of galactose, glucose, and fucose in the molar ratio 76.2:2.1:1, respectively. The high performance gel permeation chromatography (HPGPC) results showed that the molecular weight of the PHPs obtained was 6.3 × 10⁵ Da, and the sulfate content was 2.7 mg/mL. Fourier infrared spectroscopy was used to analyze the functional groups and structures of the polysaccharides. The effect of concentration, temperature, and pH on the apparent viscosity of the PHPs solution were studied using rheology experiments, which revealed that PHPs were a “non-Newtonian fluid” with shear-thinning behavior. The viscosity of the PHPs gradually increased with increasing sugar concentration, and decreased with increasing temperature, acidity, and alkalinity. Detection of the antioxidant activity of OH*, DPPH*, and ABTS* revealed that the scavenging activity of ABTS* was higher than that of OH* and DPPH* in the concentration range of 1–5 mg/mL. In the experiments of simulating gastric juice and alpha amylase in vitro, it was found that PHPs can better resist digestion of alpha amylase, and have better resistance than fructooligosaccharide (FOS), so PHPs have potential prebiotic activity. These findings demonstrate the potential of PHPs for use in the food and cosmetic industries.     

Nutrient composition of the leaves and flowers ofColocasia esculenta and the fruits ofSolanum melongena

The nutrient composition, ofColocasia esculenta flowers (CF) and leaves (CL), and the green fruits ofSolanum melongena (SM) were carried out as a means to determine their nutritional potential. Results showed that these food materials had high moisture and fiber levels which ranged between 888 and 906 g·kg^–1; and 204 and 303 g·kg^–1 dry weight (dw) for moisture and fiber respectively. The calorific values were between 3889 and 4001 kcals·kg^–1 dw, while the total lipids ranged from 53 in CF to 71 g·kg^–1 dw in SM. The leaves ofColocasia esculenta had the highest crude protein value of 307 g·kg^–1 dw. The flowers had 149 g·kg^–1 dw while SM had 138 g·kg^–1 dw. The amino acid profile in the flowers and leaves ofColocasia esculenta in contrast to SM were balanced comparable to the reference FAO pattern. Ash values were high (ranging from 76 in SM to 98 g·kg^–1 in CL) with potassium being the principal element. Iron and Zinc levels were also high especially in CF (with 303 and 82 mg·kg^–1 dw respectively). These foods also contained moderate quantities of calcium, phosphorus and magnesium but were poor in manganese and copper.     

Effects on Maize Starch Properties of Heat-treatment with Water–ethanol Mixtures

Maize starch (1 part) was heated at 120 °C for 20 min in water–ethanol mixtures (5 volumes), in which the water content varied over the range 0–70%, and the product solvent-exchanged with acetone. On treatment with mixtures containing 40–60% water, the swelling power and solubility at 97 °C decreased and the differences between these values measured at 25 and 97 °C narrowed. The properties of starch treated with a mixture containing 30% water resembled those of heat–moisture treated starch. The values of ΔH and ΔS for swelling were greatly decreased by treatment in mixtures with a water content greater than 20–40% (0·39–0·63 mole fraction). Furthermore, the digestibility ratio ofalpha-amylase (endo-type) to glucoamylase (exo-type) was at a maximum after treatment with a mixture containing 30% water. These findings suggest that rearrangements between the amylose and amylopectin in starch granules are occurring after treatment with mixtures containing more than 30% water. These changes in the starch granule are enhanced when the treatment temperature is increased to 100–130 °C.     

Characteristics of destarched corn fiber extrudates for ethanol production

The effect of extrusion on characteristics of destarched corn fiber was investigated. Extrusion was conducted at a screw speed of 300 rpm, feed rate of 100 g/min, feed moisture content of 30%, melt temperature of 140 °C and die diameter of 3 mm. After extrusion, characteristics of raw and extruded destarched corn fiber were compared. Raw and extruded destarched corn fibers were enzymatically saccharified and fermented using Saccharomyces cerevisiae (ATCC 24858). Extrusion pretreatment resulted in low crystallinity index, significant decrease in degree of polymerization and microstructure disruption of destarched corn fiber for enzymatic saccharification. This provides a significant increase in xylose yield for fermentation. Significant increase in protein digestibility and free amino nitrogen were additional benefits of extrusion for yeast nutrient in fermentation. Therefore, extruded destarched corn fiber significantly increased (p < 0.05) ethanol yield (29.08 g/L) and higher conversion (88.79%) by improving the physiochemical and functional properties for saccharification and fermentation.     

Effect of storage temperature on tuber composition,extrusion force,and Brabender viscosity

Kennebec potatoes were evaluated for the effect of storage temperature and time on tuber composition and on mealiness as measured by extrusion force of baked potato and Brabender viscosity of raw, lyophilized tissue. Potatoes from three specific gravity classes, 1.072, 1.082, and 1.090 (±0.001), were evaluated initially and after storage at 1.7°C for 2 and 3 mo., 7.2°C for 2 and 3 mo., 1.7°C for 2 mo. followed by 7.2°C for 1 mo., and 7.2°C for 2 mo. followed by 1.7°C for 1 mo. There were highly significant differences in mealiness associated with the storage treatments and with specific gravity. Mealiness decreased as temperature decreased. Mealiness estimates of tubers from the storage temperature reversal treatments were intermediate to those of the 7.2°C and 1.7°C treated tubers. Simple correlation analysis showed extrusion force and Brabender viscosity to be significantly and positively related to each other, to total starch and to swollen starch and significantly but inversely related to glucose and to the sum of glucose plus sucrose. Specific gravity and total solids were significantly but less highly positively correlated with both physical measurements. Multiple correlation-regression analysis showed only total starch to be significantly related to mealiness independent of the other compositional variables.     

Hydrothermal modification of wheat starch part 1. Effect of particle size on the viscosity of formed pastes

Aqueous starch suspensions (8 g/100 g) were prepared in a measuring flask of a Brabender viscograph and heated to temperatures of 74.0, 76.5, 79.0, 81.5, 84.0, 86.5, 89.0, 91.5 or 94.0 °C under continuous stirring. The resultant solution was cooled and frozen, and then defrosted and subjected to re-pasting in the Brabender viscograph.The heating and freezing of wheat starch suspension evoked changes in its properties, with the tendency and extent of these changes dependent on the pre-heating temperature. During re-pasting of the produced starch preparations in a Brabender viscograph, an increase occurred in particle size of the granules—and 8-fold increase in paste viscosity—compared with pastes produced from native starch. The viscosity of pastes was positively correlated with the size of formed gel sacks determined using a laser particle size analyzer. This was also found to depend on pre-heating temperature and changed according to a determined quadratic function. The strength of produced gels, measured with the oscillating–rotating viscometer, was higher than that of the gel produced from native starch and depended on the pre-heating temperature; however, these changes followed a determined quadratic function.     

Effects of Restricted Water Availability and Increased Temperature on the Grain Filling, Drying and Quality of Winter Wheat

Experiments in controlled environments examined the effects of the timing and severity of drought, and increased temperature, on grain development of Hereward winter wheat. Environmental effects on grain specific weight, protein content, Hagberg Falling Number, SDS-sedimentation volume, and sulphur content were also studied. Drought and increased temperature applied before the end of grain filling shortened the grain filling period and reduced grain yield, mean grain weight and specific weight. Grain filling was most severely affected by drought between days 1–14 after anthesis. Protein content was increased by stresses before the end of grain growth, because nitrogen harvest index was less severely affected than was dry matter harvest index. Hagberg Falling Number was increased to the greatest extent by stresses applied 15–28 days after anthesis. Treatment effects on grain sulphur content were similar to those on protein content, such that N:S ratio was not significantly affected by drought nor temperature stresses. The effects of restricted water on grain yield and quality were linearly related to soil moisture between 44 and about 73% field capacity (FC) from days 15–28. Drought stress (but not temperature stress) before the end of grain filling decreased SDS-sedimentation volume relative to drought applied later.     

Some observations on the toxic effects of the seed extract ofSphenostylis stenocarpa (Hochst ex A. Rich) Harms. on intestinal muscle

The effects of the water extract ofSphenostylis stenocarpa were observed on the guinea pig ileum and rabbit jejunum. The extract produced dose dependent — contractions of the guinea pig ileum with an ED₅₀ of 3.664×10^–5 g/ml and a calculated dose ratio of 1.25. The extract specifically stimulated muscarine receptors. Atropine (8×10^–7 g/ml) caused a parallel shift to the right of the log dose — response curve in the guinea pig ileum suggesting a competitive antagonism. Boiling for about 12 h did not affect the contractile action of the extract on tissue preparations. However, boiling for 12–14 h completely abolished its contractile effect. Incubation of the extract with cholinestrerase at 37°C for 1 h did not abolish its contractile action on the intestine.     

Effects of selected extrusion parameters on physicochemical properties and in vitro starch digestibility and β-glucan extractability of whole grain oats

Whole grain oat flour was extruded under different moisture contents (15%, 18%, 21%), barrel temperatures (100 °C, 130 °C), and screw speeds (160 rpm, 300 rpm, 450 rpm), and selected physicochemical properties, in vitro starch digestibility, and β-glucan extractability of the extrudates were analyzed. An increase in screw speed resulted in an increase in radial expansion index, water absorption index, and water solubility index. Screw speed significantly affected slowly and rapidly digestible starch. Moderate screw speed (300 rpm) led to higher slowly digestible starch with an accompanying decrease in rapidly digestible starch. Low moisture conditions (15%) resulted in the highest resistant starch and water-extractable β-glucan. Under the conditions used in this study, extrusion did not result in changes in water-extractable β-glucan molecular weight. Thus, extrusion might be beneficial in improving functionality and consumer acceptability by affecting physicochemical properties, in vitro starch digestibility, and β-glucan extractability of oat extrudates.     

Microscopical Study of the Destructuring of Waxy Maize and Smooth Pea Starches by Shear and Heat at Low Hydration

Smooth pea and waxy maize starches were processed under controlled temperature (<160 °C) conditions at low moisture content (30%) using a rheometer with pre-shearing, to simulate extrusion. Specific mechanical energy was measured and remained lower than 10³J/g. Starch modification was analysed at different structural levels by differential scanning calorimetry (DSC), X-ray diffractometry, light microscopy and at the granular level by transmission electron microscopy (TEM). Thermal inputs induced crystallite melting and internal disorganisation of granular structure, whereas mechanical input (SME>10²J/g) induced granule fragmentation. Under shearing and heating, the concomitant destructuring mechanisms led to a higher rate of modification. Fragmentation itself induced only partial loss of crystallinity (<50%). Small fragments finally melted due to a local temperature increase contributed by interparticular friction. Susceptibility to fragmentation was related to the mechanical properties of starch granules associated with their architecture and botanical origin.