Native Flour Research Articles

Materials based on maize biopolymers: Effect of flour components on mechanical and thermal behavior

AbstractThe present study describes the effects of glycerol, relative humidity (RH) and the minor components of corn flour on mechanical and thermal properties of native flour, defatted flour, and starch‐based materials. The kinetic of retrogradation for these different materials were dissimilar. For all samples, strain at break shows a maximum value as a function of RH followed by a decrease, explained by the appearance of water and glycerol clusters. Starch controls the mechanical properties of corn flour‐based material and their variations with temperature and humidity. Lipid and protein have negative effect on mechanical properties of thermoplastic flour toward starch but they did not have a plasticizing effect on the physicochemical behavior of the matrix. Tgs decreased as a result of water content increase.

Nutritional, Functional and Physical Properties of Extrudates from Blends of Cassava Flour with Cereal and Legume Flours

Low protein and poor functionality limit the use of cassava flour in snack foods, which were modified using blends with cereal and/or legume flours. Native, malted (using alpha-amylase) as well as malted and pre-gelatinized was blended with cereal (finger millet and whole wheat flours) and/or legume (chick pea flour). Extrudates were prepared at a screw speed of 100 rpm and die temperature of 180 °C. Malted flour based extrudates had lower starch content than native flour. Gram malted cassava based blends gave products with the highest protein. In vitro starch digestibility was the highest for pre-gelatinized flour based mixes. Extrudates with low fat and energy have scope as low calorie snacks for obese and diabetic people.

Production of High Fructose Syrup from Cassava and Sweet Potato Flours and their Blends with Cereal Flours

Despite being a rich source of starch, root crops such as cassava and sweet potato have not been widely exploited for the production of high fructose syrup (HFS), which is a highly valued sweetener for the food and beverage industries. The major factors contributing to the cost of production of HFS are the cost and labor-intensive steps in the production of starch, different processing temperatures and pH for the enzyme reactions, poor extractability of starch, etc. With the objective of overcoming the cost associated with the preparation of starch, the feasibility of using native cassava/sweet potato flours and their blends with rice flour and wheat flour, as the raw material for HFS production was investigated. The saccharified slurry from cassava--rice flour blends contained 70-72 g reducing sugars/100 g, which was higher than that released from native cassava flour (~69%). Blends of sweet potato with rice or wheat yielded saccharified mash with lower content of reducing sugars (60-66%). Although the percentage conversion to fructose after isomerization was similar for cassava/sweet potato or their blends with cereal flours (42-43%), fructose yield was higher in native cassava flour and cassava-rice blends (28-29 g/100 g) than the other flour blends.

Effect of pre-soaking treatments on the nutritional profile and browning index of sweet potato and yam flours

Abstract The use of sweet potato and yams for product development is hindered by the discoloration from enzymatic and non-enzymatic browning. The effect of pre-soaking treatments on the nutritional changes and browning index (BI) of sweet potato and yam (greater yam and white yam) flours was investigated. Ascorbic acid (AsA), citric acid (CA), acetic acid (AA) and sodium metabisulfite (SMS) were used for soaking at three concentrations (0.25%, 0.50% and 1.00%) and two durations (1 h and 2 h). AsA and SMS removed more starch during soaking of sweet potato, while CA and AA removed more starch from greater yam and CA removed more starch from white yam. Highest removal of reducing sugars was observed in sweet potato in AA, while CA removed maximum reducing sugars from both the yams. Phenol and total free amino acid (TFA) levels were more in SMS treatment than the control sweet potato flour, and least in AA (2 h). Whilst AsA raised the phenols and TFA in greater yam, it removed phenols to the maximum in white yam. Maximum BI was in AsA treatment for the three crops, and least for flour from CA (0.25%) treated yams and AA (1.00%) treated sweet potato. Industrial Relevance Browning resulting from enzymatic and non-enzymatic reactions is a major drawback in the processing of sweet potato and yams for product development. The study showed that this could be successfully tackled through soaking the slices in low cost chemicals like acetic acid or citric acid and sodium metabisulfite at low concentrations. The treated slices yielded flour with very low browning indices compared to the respective native flours, which could enhance the potential of such flours in the development of food products.

The Effect of Cooking on the Nano-Sized Crystallites in Finger Millet and Barley Using Waxs Data

Finger millet and barley malt flours, as well as their blends, were cooked and the hydrolysates were spray dried. These samples along with native millet and barley flours were used for recording X-ray diffraction data in the range 2θ = 2 to 40°. Using an in-house line profile analysis (LPA) program based on the Fourier method, the nano-sized crystallite dimension along with the intrinsic strain present in these cereals have been estimated for the first time. The effects of hydrolyzing the malts and their blends on the nano-sized crystallites have been discussed.

Fractionation of cereal flour by sedimentation in non-aqueous systems. II. Rheological characterisation and baking performance of the protein fraction

A previously described method for the non-aqueous fractionation of cereal flours by sedimentation in non-aqueous solvents was carried out using flours of three wheat cultivars differing in baking performance, as well as one rye and one barley flour. The method was based on differences in the densities of starch (higher) and protein (lower). Thus, suspending finely milled flour in an inert solvent mixture with a density in between the densities of starch and protein yielded a sedimented starch fraction and a protein-rich fraction at the surface of the solvent. Further purification of this upper fraction provided a protein fraction, a middle fraction, and a lipid fraction. The protein fractions were examined by means of rheological methods such as micro-extension tests and creep-recovery tests. They also were reconstituted to standard flour with a protein content of 13.5%, which was used for micro-scale baking tests. Compared to aqueous isolated gluten, the hydrated protein fractions from wheat were much more extensible and had a lower resistance to extension. The baking performance of the wheat protein fractions was superior to gluten and comparable to the native wheat flours. The protein fraction from rye gave a wheat-like bread crumb, whereas the barley protein was not suited for bread making.

Effect of Heat-Moisture Treatment on the Digestibility and Viscous Characteristics of Hard Wheat Flour and Separated Wheat Starch

The effects of heat-moisture treatment on the digestibility and viscous characteristics of hard wheat flour and separated wheat starch were examined to obtain basic data and information on texture modifier materials in food. From SEM, starch granules of heat-moisture-treated wheat flour appeared to change so as to have a flattened shape and showed adherence to other starch granules. The protein content and moisture content were not changed by heat-moisture treatment. The rate of protein degradation by pronase and the solubility of flour proteins in 0.5 M sodium chloride and water were markedly lower for the heat-moisture-treated wheat flour than for untreated native flour. The heat-moisture-treated wheat flour and separated wheat starch showed distinct peak viscosities in particular, native and heat-moisture-treated starch showed considerable differences; in their pasting temperature and peak viscosity. The apparent activation energy of native wheat flour paste at 14.7 kJ /mol was greater than that of the heat-moisture-treated wheat flour paste at 13.4 kJ/mol. In terms of starch pastes, the apparent activation energy of the heat-moisture-treated starch sample was 10.5 kJ/ mol, whereas that of the native sample was 25.9 kJ/mol.

Semi-sweet biscuit making potential of soft wheat flour patent, middle-cut and clear mill streams made with native and reconstituted flours

The influence of patent, middle-cut and clear flour grades as native or reconstituted flour blends on both the rheological properties of the dough and the quality of semi-sweet biscuit (flour/sugar/fat/water ratio of 100/30/8/36) was studied. Moving from the central portion (patent) to the peripheral portion (clear) of the grain endosperm increased the dough hardness from 3.77 to 4.84 N, consistency from 19.3 to 25.5 N s, elongational viscosity from 4.13×10 −5 to 5.54×10 −5 Pa s, half-relaxation time from 0.45 to 0.59 s, but decreased the rate of relaxation from 4.51 to 3.09 s −1 of the biscuit's dough produced with the native flours due to the wide variation in the physico-chemical properties of these fractions. Quantitatively, the fractionation/reconstitution procedure reduced moderately these rheological parameters, and the flour functionality could not be restored completely. Biscuits produced with the patent flour showed the largest length and lowest thickness, whilst the clear fraction led to production of denser biscuits with greater cohesion (mean tearing force) of the biscuit inner structure and also contain more grains or group of grains per unit of penetration (number of spatial ruptures). The biscuits made with the reconstituted flour fractions had almost equivalent dimensional characteristics, and excellent surface appearance, but were also darker in colour than their native flour counterparts. The half-relaxation time (Tla) and the rate of relaxation ( k) obtained from the biscuit's dough relaxation curves were excellent predictors of the biscuit's quality (length, density, structural cohesion and resistance to solicitation). Dough hardness was correlated positively with elongational viscosity, half-relaxation time and consistency and negatively with the rate of relaxation, whilst some of the biscuit's characteristics such as density correlated positively with structural cohesion and resistance to solicitation.

Cooperation of phosphatidylcholine with endogenous lipids of wheat flour for an increase in dough volume

Phosphatidylcholine (PC) increases the gas-retaining ability of dough, the dough volume on fermentation and the loaf volume of bread. The cooperation of wheat flour endogenous lipids with PC was examined. More than 90% of the total wheat flour lipids were extracted with chloroform, the extracted lipids comprising glycolipids (33 wt%), non-polar lipids (56 wt%), and phospholipids (11 wt%). The increase in the specific volume of dough with delipidated wheat flour by the addition of PC was smaller than the increase in the specific volume of dough with native wheat flour. The addition of the extracted lipids to delipidated wheat flour restored the increase in dough volume by the addition of PC. The glycolipid fraction of the extracted lipids was most effective for enhancing the action of PC. The results suggest that interaction of PC with wheat flour glycolipids may synergistically increase foam stability to enhance the gas-retaining stability of dough.

Effect of Vital Gluten and Gum Arabic on the Textural Properties of Pasta Made from Pre-gelatinised Broken Rice Flour

Broken rice flours of three indigenous rice cultivars were utilised for the formulation of tube type pasta (Ziti-cut) using four levels of vital gluten (14-20%, flour weight basis) and gum Arabic (0.5-2.0%, flour weight basis). The textural qualities of pasta were analysed using a texture analyser (TAXT-2i) and by descriptive sensory analysis. The pasta made from native broken rice flour and pre-gelatinised broken rice flour supplementing with vital gluten to obtain 14% protein content were compared for their instrumental texture qualities (hardness and shear strength of raw pasta as well as stickiness and adhesiveness of cooked pasta) and sensory texture analysis (colour, hardness, chewiness, smoothness and grittiness). The pre-gelatinised broken rice flour was found suitable for pasta preparation based on its firmer, larger shear strength and less stickiness and adhesiveness than its native broken rice flour. Among the three varieties, the pre-gelatinised broken rice flour of variety PR-114 with 14% protein content (supplemented by vital gluten) and 1.5% gum Arabic has been found most suitable for the pasta preparation with desirable quality attributes on the basis of instrumental and sensory textural characteristics.

Changes in characteristics of sweet potato flour prepared by different drying techniques

The changes occurring in the characteristics of sweet potato flour as a result of processing were investigated. Pasting behaviour of drum dried and hot air-dried sweet potato flour was determined using Rapid Visco-Analyser. The pasting characteristics decreased due to gelatinization of starch during processing. The degradation of starch by amylases during hot air drying further lowered the water binding capacity/viscosity and total amylose and increased the digestibility compared to those of drum dried and native flour. Swelling power and solubility of the flours increased as a result of processing which subsequently increased with increase in temperature. Scanning electron micrographs of starch granules showed tendency of clustering, especially in drum dried samples. X-ray diffraction patterns showed alteration from Ca-type to V-type with a marked reduction in crystallinity index as a result of processing. The 13C NMR spectra of processed starches showed reduced peak intensities and line widths due to depolymerizing effects, and also pointing to their change in crystallinity.

The effect of extrusion cooking on resistant starch formation in waxy and regular barley flours

Hull-less barley flours from CDC-Candle (waxy) and Phoenix (regular) were extrusion cooked under various combinations of temperature (90, 100, 120, 140 and 160 °C), moisture content (20%, 25%, 30%, 35% and 40%) and screw speed (60, 80 and 100 rpm). The effect of processing on the formation of resistant starch (RS3) in the extruded flour was determined by a technique that involved a step in which the flour were heated at 100 °C in the presence of thermostable α-amylase which was expected to destroy all the RS1 and RS2. Literature on resistant starch has suggested that RS3 forms only during heat treatment of moist starchy materials. In contrast, when determined by using the same methodology, the native (unprocessed) flours that is supposed to be free of RS3, showed resistant starch value of 40–60 mg/100 g. This indicated that RS1 and RS2 are not totally destroyed by the heat treatment step of the methodology used in determining RS3. Extrusion cooking did not significantly ( P <0.05) alter the RS3 content of native flours, the RS3 contents generally decreased. Refrigeration at 4 °C for 24 h before oven drying of extruded flour samples slightly increased the RS3 content. An attempt was made to isolate the RS3 from the extruded flour using enzymes. The methodology involved sequential enzymatic treatments to flours with lichenase, β-glucosidase, protease, thermostable α-amylase and amyloglucosidase. The RS3 content in the isolates ranged between 6–34 mg/100 g which was lower than that of the raw materials (extruded samples) before enzymatic isolation. This was unexpected but indicated that the RS3 did not concentrate, suggesting that hydrolysis of the other grain components such as β-glucan and proteins may have exposed the RS1 and RS2, that initially escaped hydrolysis to α-amylase.

The effect of extrusion cooking on resistant starch formation in waxy and regular barley flours

Hull-less barley flours from CDC-Candle (waxy) and Phoenix (regular) were extrusion cooked under various combinations of temperature (90, 100, 120, 140 and 160 °C), moisture content (20%, 25%, 30%, 35% and 40%) and screw speed (60, 80 and 100 rpm). The effect of processing on the formation of resistant starch (RS3) in the extruded flour was determined by a technique that involved a step in which the flour were heated at 100 °C in the presence of thermostable α-amylase which was expected to destroy all the RS1 and RS2. Literature on resistant starch has suggested that RS3 forms only during heat treatment of moist starchy materials. In contrast, when determined by using the same methodology, the native (unprocessed) flours that is supposed to be free of RS3, showed resistant starch value of 40–60 mg/100 g. This indicated that RS1 and RS2 are not totally destroyed by the heat treatment step of the methodology used in determining RS3. Extrusion cooking did not significantly ( P<0.05) alter the RS3 content of native flours, the RS3 contents generally decreased. Refrigeration at 4 °C for 24 h before oven drying of extruded flour samples slightly increased the RS3 content. An attempt was made to isolate the RS3 from the extruded flour using enzymes. The methodology involved sequential enzymatic treatments to flours with lichenase, β-glucosidase, protease, thermostable α-amylase and amyloglucosidase. The RS3 content in the isolates ranged between 6–34 mg/100 g which was lower than that of the raw materials (extruded samples) before enzymatic isolation. This was unexpected but indicated that the RS3 did not concentrate, suggesting that hydrolysis of the other grain components such as β-glucan and proteins may have exposed the RS1 and RS2, that initially escaped hydrolysis to α-amylase.

P14 Hydrolysed wheat protein: a new allergen in cosmetics and food

For the pas few years, mainly because of mad cow disease, hydrolysed wheat proteins (HWP) have been used in cosmetics and food as emulsifiers and stabilizers in replacement of bovine collagen. We report here contact urticaria to cosmetics induced by these HWP in 7 patients of which 6 had food allergy to modified gluten and the results of their immunological testing. These cases were regrouped through the french network REVIDAL‐GERDA.All 7 women developped contact urticaria immediatly after applying cosmetics (mainly facial cream), from different brands, containing HWP. Six of them had also anaphylactic reactions or urticaria after eating preserved foods or delicatessen which contained modified gluten. Neither had allergic reaction after eating broad or bread.Skin tests were positive with the cosmetics, HWP contained in them and, in case of food allergy, modified gluten. They were negative with natural wheat flour. Despite that, specific IgE to wheat flour were positive in 2 cases. Specific IgE to gluten were positive in 3 patients.Sera were also investigated for their specificity toward wheat proteins and various preparations of gluten. Individual variations of specificity were observed. All sera contained IgE reacting with both hydrolysed peptides and some native flour proteins.It appears that, from the medical history, allergy to cosmetics preceeded food allergy. In view of these elements, may be the use of HWP in cosmetics should be questionned.

Physico‐chemical properties of flour and starch from jackfruit seeds (Artocarpus heterophyllus Lam.) compared with modified starches

SummaryJackfruit (Artocarpus heterophyllus Lam.) is one of the most popular tropical fruits grown in Asia. The objective of this study was to compare physico‐chemical properties of native flour and starch from jackfruit seeds (A. heterophyllus) to commercially modified starches (Novation 2300 and Purity 4). The colour of jackfruit seed starch was lighter than the Novation 2300 starch but darker than the Purity 4 starch. The jackfruit seed starch had a narrower gelatinization temperature range than Purity 4 and required less gelatinization energy compared with modified starches. The peak viscosity of jackfruit seed starch was lower than commercially modified starches. Likewise, setback viscosity, swelling power and solubility of jackfruit seed starch showed similar trends. Results from this study suggest that native starch from jackfruit seed could be used as an alternative for modified starches in a system needing starch with a high thermal and/or mechanical shear stability.

Fractionation and reconstitution of wheat flour – effect on dough rheology and baking

A method for the fractionation and reconstitution of wheat flour, which makes it possible to investigate the contribution of flour fractions to baking performance and dough rheology, is presented. Micro-scale rheological methods and a micro-scale baking test on the basis of 10 g flour were used. Two wheat cultivars with different baking performances were studied. Fractionation involved defatting of flour by dichloromethane, formation of a dough, isolation of gluten by washing the dough with distilled water in a glutomatic at 15 °C, collection of the aqueous suspension and separation into a soluble fraction and two starch fractions (upper and lower layer) by centrifugation. Reconstitution of flour gave reproducible results. The baking volumes of the reconstituted flours decreased by a factor of 0.95, and the respective doughs and glutens had higher resistances than the native flours. Mixing of reconstituted flour in the presence of reduced glutathione (0–150 nmol g–1) decreased the dough resistance but the native values could not be established. An increase of the total protein content of the reconstituted flour (8–16 g 100 g–1 flour) was proportional to the baking volume. Increasing amounts of the soluble fraction led to more extensible, weaker doughs. Gliadin and glutenin had a weakening and a strengthening effect on the dough, respectively. The addition of reoxidised high molecular weight (HMW) subunits of glutenin caused an increase in dough extensibility and resistance, whereas with reoxidised low molecular weight (LMW) subunits of glutenin, only the dough resistance was increased. Micro-scale baking tests showed that HMW subunits increased the loaf volume strongly, while the opposite effect was observed for the addition of LMW subunits. Interchange of fractions between the two wheat cultivars showed that gluten was most important for the baking performance, followed by the starch and the soluble fractions.

Biochemical Studies of Proteins in Nondeveloped, Partially Developed, and Developed Doughs

ABSTRACTNondeveloped, partially developed with shear and extensional deformations, and developed doughs represent different stages of dough development. To understand the relationship between gluten proteins and dough rheology, this study used disulfide‐sulfhydryl analyses, gel filtration chromatography, SDS‐PAGE, acid polyacrylamide gel electrophoresis (A‐PAGE), and densitometry to examine proteins in the four types of doughs mentioned. Free sulfhydryl content was the lowest in native flour and nondeveloped dough, and the highest in partially developed doughs, while a reverse trend was observed for disulfide content. For each flour sample, the protein elution profile from gel filtration chromatography shifted with the level of dough development. With respect to the smallest sized molecules, native flour had the most, followed by nondeveloped, partially developed, and then developed doughs. SDS‐PAGE and A‐PAGE exhibited similar protein patterns among the same chromatographed protein fractions of each native flour and its different doughs. Densitometric data showed that the amount of high molecular weight (HMW) glutenins increased and the amounts of low molecular weight (LMW) glutenins, gliadins, and albumins/globulins decreased with progressive stages of dough development. In conjunction with previously published results, indications are that the increase in the size and the amount of HMW glutenins is related to the strength of dough and the amount of protein matrix present in the dough.

Wheat Bread Quality as Influenced by the Substitution of Waxy and Regular Barley Flours in Their Native and Extruded Forms

The substitution of wheat flour with barley flour (i.e. native or pretreated/extruded) reduced the loaf volume. Depending on the barley variety and flour pretreatments, the colour and firmness/texture of the bread loaves were altered. Amongst the barley breads prepared from native flours (at 15% barley flour substitution level), Phoenix had higher loaf volume and lower crumb firmness than Candle. However, amongst the barley breads prepared from extruded flours, CDC-Candle had higher loaf volume and lower crumb firmness than Phoenix. The lower loaf volume and firmer crumb texture of barley breads as compared with wheat bread may be attributed to gluten dilution. Also, the physicochemical properties of barley flour components, especially that of β-glucan, can affect bread volume and texture. β-glucan in barley flour, when added to wheat flour during bread making, could tightly bind to appreciable amounts of water in the dough, suppressing the availability of water for the development of the gluten network. An underdeveloped gluten network can lead to reduced loaf volume and increased bread firmness. Furthermore, in yeast leavened bread systems, in addition to CO2, steam is an important leavening agent. Due to its high affinity for water, β-glucan could suppress the amount of steam generated, resulting in reduced loaf volume and greater firmness. In the present study, breads made with 15% HTHM CDC-Candle flour had highly acceptable properties (loaf volume, firmness and colour) and it indicated that the use of extruded barley flours would be an effective way to increase the dietary fibre content of barley breads.

Measurement of glass transition in native wheat flour by dynamic mechanical thermal analysis (DMTA)

Summary This work describes a method to study glass transition on native starch powders, based on dynamical mechanical thermal analysis using compression tests, and was applied to wheat flour (13.5% water content). This method will allow the determination of Tg in native (unprocessed) starchy materials, with minimal disturbance of the natural structures. The influence of the test conditions (heating rate, frequency and strain) on the glass transition measurements was determined using factorial designs. The values of Tg determined as the maxima of the energy dissipation (peaks in E″) of native flour and of freeze‐dried pre‐gelatinized flour were not statistically different (around 64 °C). The heating rate did not affect the measurements in the range tested (0.25 to 1 °C min−1). An interactive effect of the strain amplitude and the frequency was detected. The significance of this interaction can be caused by differences in mechanical energy dissipation, which would indicate that not only temperature but also the total energy input may affect this transition. Slight effects of phase separation between gluten and starch were found on native flour.

Effect of extrusion cooking on structure and functional properties of pea and kidney bean proteins

Pea (Pisum sativum L cv Ballet) and kidney bean (Phaseolus vulgaris L cv Pinto) seeds were extruded at 148 and 156 °C respectively. Protein solubility at various pH values and in various solvents was determined and analysis of protein fractions was carried out by SDS-PAGE. Also, sulphhydryl and disulphide groups, water-holding capacity (WHC), water solubility index (WSI) and oil absorption capacity (OAC) were determined. No changes in total nitrogen content of pea and kidney bean seeds occurred as a result of thermal treatment. Protein solubility from raw and extruded legumes was significantly higher in saline solutions than in water in the pH range 2–10. The solubility of proteins from extruded pea and kidney bean flours was greatly decreased with respect to native flours when extraction was in buffer (pH 7.0) alone. Extraction with buffer containing 2-mercaptoethanol (2-ME) or sodium dodecyl sulphate (SDS), alone or in combination, greatly increased protein extractability. As a result, the relative solubility was nearly 100% in buffer with SDS and 2-ME for both raw and extruded samples. Total and free sulphhydryl group and disulphide contents decreased significantly (P < 0.05) after extrusion cooking. Moreover, extrusion treatment caused major changes in the band patterns of the albumin and globulin fractions obtained by SDS-PAGE. WHC and WSI of extrudates increased significantly in both peas and kidney beans. A significant reduction in OAC was observed in extruded kidney bean flour. © 2000 Society of Chemical Industry