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Influence of temperature and ionic conditions on the rheology and droplets characteristics of winged bean protein stabilized oil-in-water emulsion

DOI:10.1007/s11694-018-9922-1
Authors:
Mohammad Makeri
Mohammad Makeri
Mohammad Makeri
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Kharidah Muhammad at Universiti Putra Malaysia
Kharidah Muhammad
Hasanah Mohd Ghazali at Universiti Putra, Malaysia
Hasanah Mohd Ghazali
  • Universiti Putra, Malaysia
Abdulkarim Mohammed at The Federal University Dutse
Abdulkarim Mohammed
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Abstract and Figures

To explore the potential of winged bean seed protein as a food ingredient, an oil-in water emulsion, [25% (w/w), pH 3] stabilized by the protein (5% solution) was prepared by high-pressure homogenizer and subjected to heat (35–75 °C), cold (4–8 °C) and NaCl (1–4%) conditions alone or in combination, and their physicochemical stability to the treatments was assessed by measuring creaming, droplets characteristics and rheology. Result showed a slight increase in mean droplet size at treatment up to 35 °C and 1–2% NaCl. At treatment of ≥ 55 °C and ≥ 3% NaCl, significant increases in mean droplet size were observed, droplet distribution changed from monomodal to bimodal, advanced flocculation and coalescence up to 75 °C, leading to poly-disperse distribution. No flow was observed until a yield value (σ0) was overcome. At 1% NaCl, the σ was 13 Pa s compared to 21 Pa s at 3–4% NaCl, and above 35 °C treatment, emulsions had high apparent viscosity and exhibited Bingham plastic model resulting from increased droplets sizes.
Creaming stability as a function of NaCl concentration (left) and superimposed size distribution curves on micrographs (right) of the WBP-stabilized oil-in-water emulsions (at pH 3) in 0% NaCl solution. The salt-treated emulsion (left) was stored (5 days) and subjected to centrifugal force of 1000×g for 20 min. Droplet size (d4,3) distribution (in volume, %) curves of the emulsions were determined by laser light scattering techniques. Emulsion samples (at pH 3) were treated with 0% NaCl solution, and kept (in 15 mL tubes) at ambient temperature (25 ± 1 °C) for 5 days in a vertical position. After storage, samples were analyzed for droplet characteristics using light scattering instrument and reported as droplet size (d4,3) distribution volume (%) by particle size (µm). As shown above, the respective droplets curves were superimposed over the droplets optical micrographs (scale = 50 µm) observed under polarized light microscopy at ambient temperature
Creaming stability as a function of NaCl concentration (left) and superimposed size distribution curves on micrographs (right) of the WBP-stabilized oil-in-water emulsions (at pH 3) in 0% NaCl solution. The salt-treated emulsion (left) was stored (5 days) and subjected to centrifugal force of 1000×g for 20 min. Droplet size (d4,3) distribution (in volume, %) curves of the emulsions were determined by laser light scattering techniques. Emulsion samples (at pH 3) were treated with 0% NaCl solution, and kept (in 15 mL tubes) at ambient temperature (25 ± 1 °C) for 5 days in a vertical position. After storage, samples were analyzed for droplet characteristics using light scattering instrument and reported as droplet size (d4,3) distribution volume (%) by particle size (µm). As shown above, the respective droplets curves were superimposed over the droplets optical micrographs (scale = 50 µm) observed under polarized light microscopy at ambient temperature
… 
Superimposed optical micrographs of droplets size distribution of WBP-stabilized emulsion droplets (at pH 3) in different (1–4%) NaCl solution and heated at 35 °C for 30 min. Scale = 50 µm
Superimposed optical micrographs of droplets size distribution of WBP-stabilized emulsion droplets (at pH 3) in different (1–4%) NaCl solution and heated at 35 °C for 30 min. Scale = 50 µm
… 
Superimposed optical micrographs and droplets size distribution curves of WBP stabilized emulsions (at pH 3) in different (1–4%) NaCl solution and heated at 55 °C for 30 min. Scale = 50 µm
Superimposed optical micrographs and droplets size distribution curves of WBP stabilized emulsions (at pH 3) in different (1–4%) NaCl solution and heated at 55 °C for 30 min. Scale = 50 µm
… 
Superimposed optical micrographs and droplets size distribution curves of WBP-stabilized emulsions (at pH 3) in different (1–4%) NaCl solution heated at 75 °C. Scale = 50 µm
Superimposed optical micrographs and droplets size distribution curves of WBP-stabilized emulsions (at pH 3) in different (1–4%) NaCl solution heated at 75 °C. Scale = 50 µm
… 
Rheological properties of the WBP-stabilized emulsion at shear rate of 0–100 s⁻¹ and 25 °C (above). The yield stress (σ0) is the shear stress (σ) at shear rate (γ) zero and the viscosity (η) is the slope of the curve at stresses above the yield stress. [For brevity of the diagrams the shear stress-shear rate curves (passing through the intercept) was removed]. Below: Changes in the viscosity of the WBP-stabilized emulsion as a function of salt concentration (1–4%) and aged for 5 days
Rheological properties of the WBP-stabilized emulsion at shear rate of 0–100 s⁻¹ and 25 °C (above). The yield stress (σ0) is the shear stress (σ) at shear rate (γ) zero and the viscosity (η) is the slope of the curve at stresses above the yield stress. [For brevity of the diagrams the shear stress-shear rate curves (passing through the intercept) was removed]. Below: Changes in the viscosity of the WBP-stabilized emulsion as a function of salt concentration (1–4%) and aged for 5 days
… 
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Vol.:(0123456789)
1 3
Journal of Food Measurement and Characterization (2019) 13:97–106
https://doi.org/10.1007/s11694-018-9922-1
ORIGINAL PAPER
Influence oftemperature andionic conditions ontherheology
anddroplets characteristics ofwinged bean protein stabilized oil-in-
water emulsion
MohammadMakeri1,2· KharidahMuhammad1· HasanahGhazali1· AbdulkarimMohammed3
Received: 25 June 2018 / Accepted: 29 August 2018 / Published online: 3 September 2018
© Springer Science+Business Media, LLC, part of Springer Nature 2018
Abstract
To explore the potential of winged bean seed protein as a food ingredient, an oil-in water emulsion, [25% (w/w), pH 3]
stabilized by the protein (5% solution) was prepared by high-pressure homogenizer and subjected to heat (35–75°C), cold
(4–8°C) and NaCl (1–4%) conditions alone or in combination, and their physicochemical stability to the treatments was
assessed by measuring creaming, droplets characteristics and rheology. Result showed a slight increase in mean droplet
size at treatment up to 35°C and 1–2% NaCl. At treatment of ≥ 55°C and ≥ 3% NaCl, significant increases in mean droplet
size were observed, droplet distribution changed from monomodal to bimodal, advanced flocculation and coalescence up to
75°C, leading to poly-disperse distribution. No flow was observed until a yield value (σ0) was overcome. At 1% NaCl, the
σ was 13Pas compared to 21Pas at 3–4% NaCl, and above 35°C treatment, emulsions had high apparent viscosity and
exhibited Bingham plastic model resulting from increased droplets sizes.
Keywords Oil-in-water emulsion· Lipid oxidation· Physicochemical properties· Droplet size· Rheology
Introduction
Several plant proteins have been tested for their dual proper-
ties of surface activity as well as stabilizers of food emul-
sion. Plant proteins such as flax seed [1], soybean proteins
[2, 3], pea isolate and concentrates [2, 4], whey protein [5, 6]
have been studied, and the influence(s) of pH, ionic strength
and thermal processing on the stability of many protein-sta-
bilized emulsions have also been investigated [7–9]. The use
of protein in stabilizing food emulsions depends on under-
standing the interfacial behavior of the adsorbed proteins,
and the relationship between interfacial characteristics and
the bulk physicochemical properties of the emulsion [10].
Isolated plant protein are employed in food products such
as salad dressing, mayonnaise, spreads, dressings and other
products as ingredients with surface-active properties and as
stabilizers. The stability of emulsions with desirable physic-
ochemical, microstructural and rheological characteristics is
essential for used as delivery vehicle for photosensitive lipid-
soluble micronutrients. According to German, O’Neill [11],
a perfect amphiphile should be soluble and flexible enough
to rapidly absorb, coat fresh surfaces as they are exposed and
then interact sufficiently among adjacent droplets to form
a stable film. However, not all proteins possess this capac-
ity, and different proteins of varying sizes, structures and
flexibilities differ dramatically in their ability to emulsify
and stabilize emulsions [12–14]. At pH values below their
isoelectric points (pI), proteins produce cationic emulsion
droplets that protects unsaturated lipids and micronutrients
such as β-carotene from oxidation by inhibiting ferrous and
ferric-lipid interactions than do non-ionic surfactants [8, 9,
15–17]. The choice of the fat phase is also critical and is
usually selected based on nutritional profile, solid fat content
(SFC), crystallization behavior, oxidative stability, flavor
release and density and viscosity of the intended molecules
[16, 18, 19]. Though soybean oil has been employed due in
* Mohammad Makeri
makeri50@yahoo.com
* Kharidah Muhammad
kharidah@upm.edu.my
1 Faculty ofFood Science andTechnology, Universiti Putra
Malaysia, 43400Serdang, Selangor, Malaysia
2 Food Technology andHome Economics Department,
NAERLS, Ahmadu Bello University, Zaria, Kaduna, Nigeria
3 Department ofBiotechnology andMicrobiology, Federal
University Dutse, Dutse, Jigawa, Nigeria
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
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Protein-stabilized emulsions
Article
Proteins are widely used as emulsifiers to facilitate the formation, improve the stability and provide specific physicochemical properties to oil-in-water emulsions. There have been a number of recent advances in the understanding of the ability of various types of proteins to provide these functional properties. This article focuses on the influence of solution composition (pH, ionic strength, sugars, polyols, surfactants, biopolymers) and environmental stresses (heating, chilling, freezing, drying) on the stability of globular protein stabilized emulsions.
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