Andrea K. Stone

Functional properties of protein isolates from different pea cultivars

Surface characteristics and functional attributes of protein isolates prepared from different pea cultivars using isoelectric precipitation were investigated. Protein levels of isolates ranged from 81–89% with isoelectric points occurring between pH 4.7–4.9. Surface hydrophobicity values differed among cultivars with CDC Dundurn and CDC Striker isolates having the lowest and highest values, respectively. Protein solubility values at pH 7.0 varied with MFR042 and CDC Dundurn isolates displaying the lowest (approximately 54%) and highest (approximately 76%) values, respectively. No significant (p>0.05) differences existed between cultivar isolates for water hydration and oil holding capacity values. Cooper and CDC Dundurn isolates had significantly (p<0.05) lower emulsifying activity indices (EAI) (approximately 31–33 m2/g) than the other cultivars. Emulsifying stability index values were all similar. EAI values were positively correlated with surface hydrophobicity values and negatively correlated with solubility values. Varietal differences for the functional attributes of solubility and emulsification were identified.

Formation and functional attributes of electrostatic complexes involving napin protein isolate and anionic polysaccharides

The formation of electrostatic complexes involving a napin protein isolate (NPI) and carboxylated alginate (AL) and sulfated (κ-, ι-, λ-type carrageenan) (CG) polysaccharides was investigated at a biopolymer mixing ratio of 10:1 (NPI/polysaccharide) as a function of pH (4.0–12.0) using turbidity and electrophoretic mobility. The functionality of the ensuing complexes was tested on the basis of their solubility, emulsion stability and foaming capacity and stability relative to NPI alone. Complexation follows two pH-dependent structure forming events associated with the formation of ‘soluble’ and ‘insoluble’ complexes. Soluble and insoluble complexes for NPI–AL, NPI–κ-CG, NPI–ι-CG and NPI–λ-CG mixtures occurred at pHs 7.1 and 6.2, 8.6 and 7.0, 9.5 and 9.3, and 9.0 and 8.7, respectively. Complexation resulted in a shift in net neutrality from 5.0 for NPI alone to pH 4.2, 3.7, 3.2 and 2.3 in the presence of κ-CG, ι-CG, λ-CG and AL, respectively. Solubility and foaming capacity of NPI were reduced with the addition of polysaccharide. Foaming stability was similar for NPI–κ-CG and NPI–λ-CG mixtures relative to NPI, but increased and decreased for NPI–ι-CG and NPI–AL mixtures, respectively. Emulsion stability was found to be similar for all mixtures relative to NPI, except for the NPI–ι-CG mixture which had reduced emulsion stability.

Formation and functionality of canola protein isolate with both high- and low-methoxyl pectin under associative conditions

Electrostatic interactions within mixtures of a canola protein isolate (CPI) and both low (LMP) and high-methoxyl (HMP) pectin were investigated as a function of mixing ratio (1:1 to 30:1; CPI-pectin) and pH (8.0-1.5) using turbidity and electrophoretic mobility measurements during an acid titration. The rheological (flow behavior) and functional (solubility, foaming, and emulsifying properties) attributes of CPI-pectin complexes were also studied. Increasing biopolymer mixing ratios shifted critical pH values associated with formation of soluble and insoluble complexes to higher values until plateauing at approximately 10:1. Maximum coacervation of CPI-HMP and CPI-LMP mixtures occurred at pH values of 5.3 and 4.8, respectively, and at a 10:1 mixing ratio. The functionality of formed complexes was similar to CPI alone, except for a slight increase in solubility for the CPI-HMP system and a reduction in foaming capacity for CPI-LMP mixtures. For both mixed systems, viscosity was enhanced relative to CPI alone, showing greater pseudoplastic behavior.

Influence of the extrusion parameters on the physical properties of chickpea and barley extrudates

In this research, the effects of extrusion processing [exit-die temperature (120–150°C), moisture content (20–24% wet basis), and screw speed (260–340 rpm)] on the specific mechanical energy and physical properties (expansion ratio, bulk density, and hardness) of desi chickpea and hullless barley extrudates were estimated using response surface methodology. Exit-die temperature and feed moisture content, as well as the interaction between them were the factors that affected the product responses the most. Significant correlation was found between the hardness and bulk density (positive), hardness and expansion ratio (negative), and bulk density and expansion ratio (negative) for both chickpea and barley extrudates. Desirable characteristics (high expansion, low bulk density, and hardness) for chickpea were obtained at high exit-die temperature, relatively high moisture, and high screw speed. As for the barley extrudates, high exit-die temperature, low moisture, and moderate to high screw speed were identified as optimal.

Nature of protein-protein interactions during the gelation of canola protein isolate networks

The nature of interactions involved during the gelation of a canola protein isolate was investigated using rheology and fractal imaging at neutral pH as a function of protein concentration (5.0-9.0% w/w). The onset of denaturation and the denaturation temperature by differential scanning calorimetry for canola protein isolate (CPI; 98.2% protein) was 78.6°C and 87.1°C, respectively. Rheological testing determined the gelation temperature (Tgel) to be ~87-90°C for all concentrations. The log % strain at break increased from 1.70 to 1.80 as CPI concentration increased from 5.0 to 7.0% (w/w). Rheological testing of CPI in the presence of destabilizing agents, NaCl (0.1 and 0.5M), urea (0.1, 0.5, 1 and 5M) and 2-β-mercaptoethanol (0.1 and 2%), was performed. Samples with NaCl and urea (0.1-1M) had similar temperature profiles and Tgel values to CPI alone whereas no gel was formed with the addition of 5M urea and 2-β-mercaptoethanol reduced the strength of the gel network. Fractal dimension and lacunarity was analyzed using CLSM imaging. The fractal dimension value for all CPI concentrations was ~1.5. The lacunarity of the gel decreased from 0.62 to 0.41 as the concentration of CPI increased from 5 to 7% (w/w). Mechanistic understanding of CPI aggregation and network formation will enable the food industry to better tailor food structure when CPI is present as ingredient.

Extractability and Molecular Modifications of Gliadin and Glutenin Proteins Withdrawn from Different Stages of a Commercial Ethanol Fuel/Distillers Dried Grains with Solubles Process Using a Wheat Feedstock

ABSTRACT Extractability and molecular modifications of gliadin and glutenin proteins withdrawn from different stages of a commercial ethanol fuel/distillers dried grains with solubles (DDGS) process using a wheat feedstock were investigated. Materials were taken postliquefaction (PL), postdistillation (whole stillage), and postdrying (DDGS) during the process and then fractionated to separate the gliadins and the soluble high- and low-molecular-weight glutenins following a modified Verbruggen extraction method. Each fraction was characterized based on the extraction efficiencies within various aqueous alcohols of propan-1-ol, electrophoretic patterns, intrinsic and extrinsic fluorescence, free and total sulfhydryl content, and total disulfide bond levels. Findings indicated significant changes to the composition of extracted proteins and modifications to the protein structure (i.e., surface properties and conformation) throughout the ethanol/DDGS process, beginning with the first step of production (PL, ≈...

Effect of the degree of esterification and blockiness on the complex coacervation of pea protein isolate and commercial pectic polysaccharides

The complex coacervation of pea protein isolate (PPI) with commercial pectic polysaccharides [high methoxy citrus pectin (P90, 90 representing DE), apple pectin (P78) sugar beet pectin (P62), low methoxy citrus pectin (P29)] of different degrees of esterification (DE) [and galacturonic acid content (GalA)] and blockiness (DB), was investigated. The maximum amount of coacervates formed at a biopolymer weight mixing ratio of 4:1 for all PPI-pectin mixtures, with the exception of PPI-P29 where maximum coacervation occurred at the 10:1 mixing ratio. The pH at which maximum interactions occurred was pH 3.4-3.5 (PPI: P90/P78) and 3.7-3.8 (PPI: P62/P29). PPI complexed with pectins with high levels of DE (low levels of GalA) and DB displayed greater interactions at optimal mixing conditions compared to pectin having lower levels of esterification and blockiness. The addition of P78 to PPI greatly increased protein solubility at pH 4.5.

Effects of Salt, Polyethylene Glycol, and Water Content on Dough Rheology for Two Red Spring Wheat Varieties

In this research, the relationship between dough rheology and water behavior was investigated in response to two osmotic regulators, salt (NaCl) and polyethylene glycol (PEG), using two Canadian Western Red Spring (CWRS) wheat varieties (Harvest and Pembina). The effects of NaCl (0.5, 1.0, and 1.5 g/100 g of flour) and PEG 400 (2.5, 5.0, and 7.5 g/100 g of flour) on dough rheology (oscillatory and creep) were estimated by using a central composite design. Variation of NaCl showed a significant effect on the phase angle δ, indicating that increasing the NaCl resulted in a more elastic dough. The opposite trend was observed with the addition of PEG. PEG 400 exerted a softening effect owing to plasticization, so that a more compliant liquid-like dough was produced. The effects of water content (±10% of farinograph absorption) and PEG molar mass on dough rheology and freezable water content were estimated by using a full factorial design. PEGs with different molar mass (400, ≈1,600, and 3,350 g/mol) were adde...

Reduction of off-flavours and the impact on the functionalities of lentil protein isolate by acetone, ethanol, and isopropanol treatments

The changes of flavour profiles in lentil protein isolate (LPI) in response to organic solvent treatments (acetone, ethanol, and isopropanol; 35-95% v/v), and the resulting impacts on the isolate colour and physicochemical and functional attributes were investigated. The major constituents of volatile compounds were aldehydes (∼46.59%) and (E,E)-3,5-octadien-2-one (∼31.79%) in the untreated LPI. Acetone treatment greatly raised ketones by ∼79.59%. In contrast, ethanol and isopropanol, except at 95% (v/v), significantly lowered total volatile compounds and had higher protein contents (∼84.55%) than the others (∼76.98%); surface charge, surface hydrophobicity, solubility and emulsion stability of these LPIs were examined. LPIs obtained from 75% (v/v) ethanol and isopropanol treatments showed slightly lower solubility but improved surface hydrophobicity to produce emulsions with a similar stability as compared with the untreated LPI. Overall, ethanol and isopropanol treatments (75% v/v) produced high quality off-flavour-reduced LPIs which may be used in various food systems.

Effect of Lactobacillus plantarum Fermentation on the Surface and Functional Properties of Pea Protein-Enriched Flour

Summary The effect of Lactobacillus plantarum fermentation on the functional and physicochemical properties of pea protein-enriched flour (PPF) was investigated. Over the course of the fermentation the extent of hydrolysis increased continuously until reaching a maximum degree of hydrolysis of 13.5% after 11 h. The resulting fermented flour was then adjusted to either pH=4 or 7 prior to measuring the surface and functional attributes as a function of fermentation time. At pH=4 surface charge, as measured by zeta potential, initially increased from +14 to +27 mV after 1 h of fermentation, and then decreased to +10 mV after 11 h; whereas at pH=7 the charge gradually increased from –37 to –27 mV over the entire fermentation time. Surface hydrophobicity significantly increased at pH=4 as a function of fermentation time, whereas at pH=7 fermentation induced only a slight decrease in PPF surface hydrophobicity. Foam capacity was highest at pH=4 using PPF fermented for 5 h whereas foam stability was low at both pH values for all samples. Emulsifying activity sharply decreased after 5 h of fermentation at pH=4. Emulsion stability improved at pH=7 after 5 h of fermentation as compared to the control. Oil-holding capacity improved from 1.8 g/g at time 0 to 3.5 g/g by the end of 11 h of fermentation, whereas water hydration capacity decreased after 5 h, then increased after 9 h of fermentation. These results indicate that the fermentation of PPF can modify its properties, which can lead towards its utilization as a functional food ingredient.