Effect of alternative processes on the yield and physicochemical characterization of protein concentrates from Amaranthus cruentus

Three different processes for the preparation of amaranth protein concentrates (APCs) were investigated with respect to the yield and physicochemical characteristics. The first was the conventional process for isolating protein (standard process), the second included an acid washing step prior to protein extraction (acid washing process) and the third included heating (50 °C) during the alkaline extraction step (thermal process). The protein yields were 17.8 and 25.6% for the acid washing and thermal processes, respectively. The concentrates were analyzed by SDS-PAGE, free sulfhydryl groups (SH), differential scanning calorimetry (DSC), size-exclusion high performance liquid chromatography (SE-HPLC), solubility in water and in 0.05 mol L⁻¹ NaCl at pH 3.0, 4.5 and 7.0, phenolic compounds content and color parameters. The results indicated that the acid washing process had positive effects on the composition, color parameters, protein solubility and thermal stability of the concentrates. The thermal process also brought about positive effects on the characteristics of the proteins and color parameters although it negatively affected solubility due to the formation of high molar mass aggregates. The conventional process, when compared with the thermal and acid washing processes, adversely affected the properties evaluated.     

Development of novel ultrathin structures based in amaranth (Amaranthus hypochondriacus) protein isolate through electrospinning

Amaranth protein isolate (API) ultrathin structures have been developed using the electrospinning technique. The effects of pH, type of solvent and surfactant addition on the spinnability, morphology and molecular organization of the obtained structures have been studied. Regarding the effect of pH on API electrospinning, capsule morphologies were only obtained at extreme pH values (i.e. pH 2 and pH 12), which allowed the solubilisation of the proteins, and the process was favoured when the solutions were previously heated to induce protein denaturation. Fibre-like morphologies were only obtained when the solvent used for electrospinning was hexafluoro-2-propanol, as this organic solvent promotes the formation of random coil structures and, thus, an increase in the biopolymer entanglements.     

Production of acidic extruded rice flour and its influence on the qualities of gluten-free bread

One of the greatest technological challenges in the production of gluten-free bread (GFB) is to find a low-cost ingredient capable of retaining gas during fermentation and the baking process. The use of gelatinized starch appears to show promise for this purpose. In this study, GFB was made using raw rice flour (100 g) with the addition of 10 g acidic extruded rice flour (AERF). The AERF was produced in a single-screw extruder, varying the extrusion temperature and lactic acid concentration. Response surface methodology (RSM) and the principle components analysis (PCA) were used to analyze the results. The results of RSM showed no significant difference, but the mean volume obtained with the AERF (1.95 mL g⁻¹) was still low when compared with that of wheat bread (6 mL g⁻¹). The crust and crumb colors and the texture (hardness = 173 g; chewiness = 90.5 and fracturability = 178) presented results similar to those of wheat bread and better than other GFB found in the literature. When analyzed by PCA the AERF obtained at 150 °C-0.5 mol L⁻¹ lactic acid, showed the best results for the GFB obtained. IR spectroscopy showed that no bands were found for esters (1740 cm⁻¹) in the AERFs, which could indicate that no new bonds were formed between the rice flour and the lactic acid.     

Development of extruded snacks using taro (Colocasia esculenta) and nixtamalized maize (Zea mays) flour blends

Extruded snacks were prepared from flour blends made with taro and nixtamalized (TF-NMF) or non-nixtamalized maize (TF-MF) using a single-screw extruder. A central composite design was used to investigate the effects of taro flour proportion in formulations (0-100 g/100 g) and extrusion temperatures (140-180 °C) on the following indices: expansion (EI), water solubility (WSI), water absorption (WAI) and fat absorption (FAI). Moreover, selected TF-NMF and TF-MF extruded products were partially characterized through proximate chemical analysis, resistant starch, color, pH, water activity, apparent density, hardness, and sensory analysis. Results indicated that EI and WSI of both TF-MF and TF-NMF extrudates were significantly increased by the use of higher proportions of taro flour, while the opposite behavior was observed for the FAI (p < 0.05). Taro flour at higher proportions in both extrudates did not produce a significant change of WAI, while the use of higher extrusion temperatures only caused a significant increase of FAI in TF-MF extrudates (p < 0.05). This study showed that flour mixtures made from taro and nixtamalized maize flour produced puffed extruded snacks with good consumer acceptance.     

Optimization of amaranth flour films plasticized with glycerol and sorbitol by multi-response analysis

The optimal formulation for the preparation of amaranth flour films plasticized with glycerol and sorbitol was obtained by a multi-response analysis. The optimization aimed to achieve films with higher resistance to break, moderate elongation and lower solubility in water. The influence of plasticizer concentration (Cg, glycerol or Cs, sorbitol) and process temperature (Tp) on the mechanical properties and solubility of the amaranth flour films was initially studied by response surface methodology (RSM). The optimized conditions obtained were Cg 20.02 g glycerol/100 g flour and Tp 75 °C, and Cs 29.6 g sorbitol/100 g flour and Tp 75 °C. Characterization of the films prepared with these formulations revealed that the optimization methodology employed in this work was satisfactory. Sorbitol was the most suitable plasticizer. It furnished amaranth flour films that were more resistant to break and less permeable to oxygen, due to its greater miscibility with the biopolymers present in the flour and its lower affinity for water.     

Diversity in seed and flour properties in field pea (Pisum sativum) germplasm

The genetic diversity in agronomic, seeds (physicochemical, hydration, textural and cooking) and flour (pasting and gel texture) characteristics amongst 71 field pea lines was studied. L∗-, a∗-, b∗-values, seed weight, density, hydration capacity, swelling capacity and cooking time ranged between 43.6 and 67.1, −2.3 and 6.2, 5.8 and 17.4, 4.26 and 25.65 g/100 seeds, 0.55 and 2.01 g/ml, 0.05 and 0.31 g/seed, 0.02 and 0.76 ml/seed and 45 and 81 min, respectively. Amylose content of starch ranged between 21.4% and 58.3%. Pasting temperature, peak viscosity, breakdown, final viscosity and setback of flours from different lines ranged from 73.5 to 81.5 °C, 533 to 3000, 8 to 187, 121 to 2276, and 183 to 998 cP, respectively. The frequency distribution and principal component analysis revealed significant variation in quality traits amongst the 71 field pea lines.     

赤拟谷盗对小麦粉品质的影响

赤拟谷盗是小麦粉加工及储存过程中的重要害虫之一。选用普通小麦粉180g,向其中投入赤拟谷盗成虫,研究小麦粉在感染头数分别为0、10、30、60、100、200,感染时间为0、15、25、35、45d时的品质变化。实验表明:随着虫口密度的增大和感染时间的延长,小麦粉的水分稍有上升,灰分变化不大;粗淀粉含量降低,粗蛋白质含量升高,湿面筋含量和面筋指数则呈现不规律的波动;清蛋白、球蛋白、谷蛋白含量下降,醇溶蛋白的含量上升;降落数值下降明显。在较低虫口密度下时,小麦粉的峰值黏度、最低黏度、黏度破损值和最终黏度有升高趋势,但随着虫口密度的增大又逐步降低。     

Gelation,thermal and pasting properties of pigeon pea (Cajanus cajan L.), dolichos bean (Dolichos lablab L.) and jack bean (Canavalia ensiformis) flours

This study evaluated the rheological, thermal and pasting properties of pigeon pea (PP), dolichos bean (DB) and jack bean (JB) legume flours and gels. Starch and protein contents were also measured and its molecular weight distribution was determined by electrophoresis. PP and DB showed the highest viscosities while JB had the highest pasting temperature. The minimum flour concentrations for gel formation were estimated at 6–8% for DB and PP and 10% for JB. Above these concentrations all flour suspensions heated to 95 °C led to gels with a solid-like behavior. Differential scanning calorimetry showed two endothermic peaks in all flours at 80–89 °C and 96–100 °C. Avrami model was successfully fitted to the hardening kinetics of PP and DB gels stored at 4 °C. The half-life times were 22 and 6 h for PP and DB respectively. PP and DB flours were able to form self-supporting gels and could be applied in the formulation of gel-like foods.     

Effect of some traditional processing operations on the functional properties of African breadfruit seed (Treculia africana) flour

The effect of germination, fermentation, roasting and defatting on the proximate composition, water absorption capacity (WAC), oil absorption capacity (OAC), foaming capacity (FC), foaming stability (FS), emulsion capacity (EC), emulsion stability (ES), packed bulk density (PBD), least gelation concentration (LGC) and protein solubility (PS) of breadfruit seed flour (BSF) was investigated. WAC, OAC, FC, EC, PBD and LGC obtained are 190-380%; 130.3-200.5%; 2.3-60.4%; 12.4-52.9%; 0.4-0.6 g/ml; 6-12% (w/v) and 200-420%; 176.4-320.6; 4.2-70.8%; 20.2-60.4%; 0.5-0.7 g/ml; 0.5-0.8% (w/v) in the full fat and defatted flours respectively. Foams were more stable in the untreated; least in fermented and roasted samples. Defatting improved the FC, FS and EC; roasting and fermentation reduced EC of full fat BSF; Processing and defatting had no effect on the PBD; roasting and germination increased LGC while defatting and fermentation reduced it. Full fat flours had the lowest PS at pH 4 and the highest at pH 8. Fermented full fat BS flour had the highest PS at pH 5 and 8. Defatted germinated, raw dried and roasted BSF had lowest PS at pH 4; PS of fermented BSF is lowest at pH 3 and highest at pH 2.     

Thermophysical properties of mango pulp (Mangifera indica L. cv. Tommy Atkins)

The density, heat capacity and thermal conductivity of mango pulp (Mangifera indica L. cv. Tommy Atkins) were determined at moisture contents of between 0.9 and 0.52 kg kg⁻¹ (w.b.) and temperatures of between 20 and 80 °C. The experimental data were satisfactorily fitted (explained variation values >99.1%) as functions of the moisture content and temperature by using multivariate linear models. In the range of conditions considered, the moisture content exhibits a greater influence on the studied properties than temperature.     

Development of extruded snacks using jatobá (Hymenaea stigonocarpaMart) flour and cassava starch blends

The use of the jatobá trees (Hymenaea stigonocarpa Mart) by the timber industry poses an ecological problem in Brazil. The objective of this research was to investigate the use of jatobá flour for the production of snacks by the thermoplastic extrusion of a composite flour consisting of jatobá and cassava starch. Chemical analysis showed that the jatobá fruit provides high-fibre flour (486 g kg⁻¹) with 66 g kg⁻¹ protein, and 398 and 88 g kg⁻¹ of insoluble and soluble fibre, respectively. Such flour is of potential use for the production of high-fibre snacks, allowing for the economical exploitation of the jatobá while preserving the tree. Composite flours with jatobá flour and cassava starch mixtures (150: 850, 300: 700, 450: 550), conditioned to moisture levels of 170, 200 and 230 g kg⁻¹ were processed in a Brabender single-screw extruder. The extrusion conditions were 150 rpm screw speed, 4 mm die diameter and 125, 150 and 175°C of barrel temperatures. The snacks produced were evaluated as to their sensory characteristics and response surface methodology was used to optimise the extrusion process. Response surface and contour diagrams revealed that all mixtures conditioned to 170 g kg⁻¹ moisture and extruded at 150°C produced snacks of acceptable quality, higher levels of jatobá flour leading to significant quality losses with respect to sensory characteristics. © 1998 Society of Chemical Industry.     

Relationship between physicochemical and functional properties of amaranth (Amaranthus hypochondriacus) protein isolates

Protein isolates from six amaranth lines/cultivars (APIs) were evaluated to study their physicochemical (hunter colour, protein content and zeta potential), structural (thermal and conformational) and functional (emulsification, foaming, water and fat absorption) properties. APIs had protein content, whiteness index and gel temperature in range of 79.4–85.4%, 41.17–54.26 and 87.8–91.8 °C, respectively. The Fourier‐transform infrared spectra of APIs revealed α‐helix, β‐sheets and random coil conformations in the secondary structure. APIs with higher relative proportion of β‐sheets had higher Differential Scanning Calorimeter denaturation temperature and gel temperature. Minimum protein solubility (PS) was observed at pH 5.0, indicating isoelectric point (pI) of amaranth proteins. The PS, emulsifying activity index (EAI), emulsifying stability index (ESI), foaming capacity (FC) and foam stability (FS) of APIs at neutral pH were related to their zeta potential (ζ). The emulsifying and foaming properties were also determined at different pHs (between 2.0 and 9.0). The EAI‐pH profile of APIs confirmed close relationship between the emulsifying ability and PS.     

Structural,functional, thermal and rheological properties of nixtamalised and extruded blue maize (Zea mays L.) flour with different calcium sources

The effects of different concentrations of calcium hydroxide [Ca(OH)₂] and calcium lactate [C₆H₁₀O₆Ca] on the functional and physical properties of extruded (EF) and nixtamalised (NF) blue maize flours were evaluated. Calcium source and concentration showed no significant effects on the EF expansion index. The water absorption index (WAI) of EF decreased as the concentrations of both calcium sources increased, and NF with C₆H₁₀O₆Ca had the lowest WAI. The thermal and pasting properties of NFs were higher than those of EF. NF with C₆H₁₀O₆Ca showed the highest final viscosity (FinV), indicating less damage to the starch granules, and this was correlated with microscopic analysis. In contrast, the FinV of EFs was significantly affected by calcium source and concentration. Extrusion with 0.3% and nixtamalisation at 2.95% of C₆H₁₀O₆Ca yielded high WAI value and the best rheological properties in maize flour, respectively. These results suggest the use of C₆H₁₀O₆Ca in extrusion or nixtamalisation to produce blue maize flours for tortilla or snacks with antioxidants.     

Physical properties and sensory acceptability of cookies made from chickpea addition to white wheat or whole wheat flour compared to gluten‐free amaranth or buckwheat flour

The effects of chickpea addition (0–100%) on the physical properties and sensory attributes of cookies based on white or whole wheat compared to gluten‐free amaranth or buckwheat flour were studied. The physical properties determined were spread factor, colour and hardness. Sensory evaluation was conducted for colour, taste, texture and overall impression. Chickpea addition decreased the lightness in white wheat cookies while increasing it in whole wheat and amaranth cookies and it significantly increased yellowness in all cookies. Spread factor of the gluten‐free cookies was reduced by chickpea addition and hardness was increased in white wheat and buckwheat cookies, and decreased in whole wheat and amaranth cookies. Sensory evaluation demonstrated that chickpea addition increased the acceptability of all cookies, in particular of the gluten‐free cookies. Optimal levels of chickpea addition were 20–40% in wheat cookies and 60–80% for amaranth and buckwheat cookies.     

Functional,biochemical and pasting properties of extruded bean (Phaseolus vulgaris) cotyledons

Response surface methodology was used to investigate the effects of extrusion conditions – namely moisture content (12.3–23.7 g 100 g^?1) and temperature (150–178 °C) – on physicochemical, antinutritional compounds, functional and pasting properties of extruded bean cotyledons. Results indicated that extrusion cooking did not change the chemical composition of bean flours, but completely eliminated the activity of the trypsin and α‐amylase inhibitors and haemagglutinins. The extrusion significantly improved starch and protein digestibility, water solubility and absorption of bean cotyledon. In addition, extrusion conditions significantly affected pasting properties, resulting in extrudate flours with different peaks and final viscosity values. From the results obtained in this work, it is possible to design a product with specific physicochemical, functional and nutritional properties using the appropriate moisture and temperature during extrusion.     

Mitigating effect of amaranth (Amarantus hypochondriacus) protein on acrylamide formation in foods

The effect of addition of amaranth flour and amaranth protein isolate to both a glucose/asparagine model system and real foods (cookies, fried tortilla chips, and baked tortilla chips) was studied to analyse the acrylamide mitigating potential of this underexploited plant with attractive nutraceutical properties. Addition of amaranth flour, with a relatively low protein content (16.45%), did not mitigate acrylamide in either the model system or the studied foods. On the contrary, addition of amaranth protein isolate decreased acrylamide content by 35–40% in the model system, 89% in cookies, 51% in fried tortilla chips, and 62% in baked tortilla chips. This acrylamide reduction was obtained without change in the colour or the texture of the cookies. On the contrary, colour remained unchanged in tortilla chips, but the addition of amaranth protein isolate increased the hardness (16–36%) of the produced tortillas. Although a much more detailed sensory evaluation of cookies and tortilla chips prepared using amaranth protein isolate is needed, the above results suggest that the use of amaranth protein may be an interesting way to both mitigate acrylamide formation and improve nutritional properties of foods.     

Comparisons of physicochemical properties and antioxidant activities among pumpkin (Cucurbita moschata L.) flour and isolated starches from fresh pumpkin or flour

Physicochemical properties (pasting and thermal properties, swelling power, water solubility and antioxidant activities) and chemical composition of pumpkin flour (PF) and starches, isolated from fresh pumpkin (SFF) or flour (SFP) were compared. SFP and SFF had similar proximate composition and amylose content. Drying process during PF preparation modified starch properties. PF exhibited greater antioxidant activities (DPPH, ABTS and FRAP), but had lower β‐carotene than fresh pumpkin. SFF and SFP had higher amylose content than PF, and exhibited a B‐type X‐ray diffraction pattern with spherical and dome‐like starch granules. Peak viscosity of SFP was relatively higher than that of SFF, probably due to lower swelling power and water solubility, which indicated increased granular rigidity in the SFP starch structure. Compared with SFF and SFP, PF had significantly higher onset (T_o), peak (T_p) and conclusion (T_c) temperatures due to a lower starch content and relatively higher fibre content, which resulted in lower gelatinisation enthalpy (ΔH).     

Nixtamalised flour and tortillas from transgenic maize (Zea mays L.) expressing amarantin: Technological and nutritional properties

Nixtamalised flour from transgenic maize (genetically modified maize with the cDNA of amarantin) and its tortillas were evaluated for some technological and nutritional properties and compared to the commercial brand MASECA^™. Nixtamalised transgenic maize flour (NTMF) showed higher protein content, total colour difference, pH, water solubility index, essential amino acids content and lower Hunter “L” value, water absorption index, resistant starch and retrograded resistant starch than MASECA^™ flour. Tortillas from NTMF had higher protein content (12.64% vs 8.93%, db), essential amino acids content and calculated protein efficiency ratio (C-PER; 2.05 vs 1.04) than tortillas from MASECA^™. Tortillas from both nixtamalised transgenic maize and MASECA^™ flours showed similar sensory properties (puffing and acceptability). The use of transgenic maize for flour and tortilla preparation may have a positive impact on the nutritional status of people from countries where maize is the basic staple food.     

Effect of acid treatment on structural and foaming properties of soy amaranth protein mixtures

To obtain a food ingredient composed of soybean and amaranth proteins with better functionality, the proteins were subjected to an acid treatment followed by neutralization. The native and treated proteins, amaranth (A and TA), soybean (S and TS) and the 1:1 mixture (M and TM) were studied. The structural characteristics and surface tension and foaming properties of the proteins were analyzed.     

In vitro inhibition of dipeptidyl peptidase IV by peptides derived from the hydrolysis of amaranth (Amaranthus hypochondriacus L.) proteins

Bioactive compounds present in foods could potentially have beneficial effects on human health. In this study we report the in vitro inhibitory capacity of peptides released from amaranth seed proteins after enzymatic digestion, against dipeptidyl peptidase IV (DPPIV); an enzyme known to deactivate incretins, hormones involved in insulin secretion. Other seeds, such as soybean, black bean, and wheat were also tested. The highest inhibition of DPPIV was observed with amaranth peptides released after simulated gastrointestinal digestion, showing an IC₅₀ of 1.1 mg/mL in a dose-dependent manner. In silico tryptic digestion of amaranth globulins was carried out releasing peptides larger than 13 residues. Some of these peptides were used for the in silico prediction of their binding modes with DPPIV. Docking models showed that the possible mechanism of globulin peptides to inhibit DPPIV was through blocking the active dimer formation. Peptides were also found inside the major cavity where the natural substrates reach the catalytic site of the enzyme. This is the first report of the identification of inhibitory DPPIV peptides from amaranth hydrolysates and the prediction of their binding modes at the molecular level, leading to their possible use as functional food ingredients in the prevention of diabetes.