Browsing by Author "Hemar Y"

Now showing 1 - 4 of 4
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    Formation and properties of highly concentrated oil-in-water emulsions stabilized by emulsion droplets
    (Elsevier Ltd, 2023-12) Cheng L; Ye A; Yang Z; Hemar Y; Singh H
    70% (v/v) concentrated emulsion has been prepared using Ca2+-cross-linked sodium caseinate particles (Ca-CAS) or Ca-CAS coated nano-sized primary emulsion droplets as emulsifiers. The primary droplet-stabilised emulsion (DSE) was compared with the conventional Ca-CAS stabilised-emulsion (PSE) in terms of viscoelasticity as affected by aging (30 days) and heating (80 °C, 30 min) at pH 5.8 and 7.0. DSE at pH 5.8 showed the highest complex modulus (G* = 1174 ± 39 Pa), approximately was six-times higher than other emulsions (G* ≤ ∼250 Pa) due to the thick emulsifier layer consisting of primary droplet increasing the effective volume faction of core droplets by a factor of ∼1.21. After aging, G* of DSE at pH 5.8 increased to 1685 ± 68 Pa, while G* of other three emulsions were ∼400 Pa. After heating, G* of DSE reached 1801 ± 69 Pa and 1312 ± 205 Pa at pH 5.8 and pH 7.0, respectively, while G* of PSE were ∼600 Pa at both pHs. The possible mechanism for aging-induced gelation was the gravity-driven microphase separation, in which the droplets flocculate together with the entrapped aqueous phase increasing the effective volume fraction. The heat-induced gelation was attributed to the increase in droplet interactions through protein aggregates and/or primary droplets forming three-dimensional networks at elevated temperature. This study suggests that the mechanical strength of food-grade concentrated emulsions can be effectively improved using nano-sized primary emulsions as emulsifying agent and can be further modulated by aging or
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    Formation of by high power ultrasound aggregated emulsions stabilised with milk protein concentrate (MPC70)
    (Elsevier BV, 2021-12-03) Zhang R; Luo L; Yang Z; Ashokkumar M; Hemar Y
    In this work, oil-in-water emulsions stabilised by milk protein concentrate (MPC70) were investigated. The MPC70 concentration was kept constant at 5% (close to the protein content found in skim milk) and the oil volume fraction was varied from 20 to 65%. Sonication was performed at 20 kHz and at a constant power of 14.4 W for a total emulsion volume of 10 mL. Under certain oil concentration (≥35%) and sonication times (≥3s) the emulsion aggregated and formed high-viscosity pseudo plastic materials. However, the viscosity behaviour of the emulsion made with 35% oil reverted to that of a liquid if sonicated for longer times (≥15 s). Confocal laser scanning microscopy showed clearly that the oil droplets are aggregated under the sonication conditions and oil concentrations indicated above. An attempt to explain this behaviour through a simple model based on the bridging of oil droplets by the MPC70 particles and, taking into account the oil droplet and MPC70 particle sizes as well as the oil volume fraction, was made. The model fails to describe in details the aggregation behaviour of these emulsions, likely due to the inhomogeneous protein layer, where both free caseins and casein micelles are adsorbed, and to the packing of the oil droplets at concentrations ≤55%. Nonetheless, this work demonstrates the potential of ultrasound processing for the formation of dairy emulsions with tailored textures.
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    Impacts of sonication and high hydrostatic pressure on the structural and physicochemical properties of quinoa protein isolate dispersions at acidic, neutral and alkaline pHs
    (Elsevier BV, 2022-12) Luo L; Yang Z; Wang H; Muthupandian A; Hemar Y
    Herein, 1 wt% quinoa protein isolate (QPI) was exposed to sonication using a 20 kHz ultrasonicator equipped with a 6 mm horn (14.4 W, 10 mL, up to 15 min) or high hydrostatic pressure (HHP, up to 600 MPa, 15 min) treatments at pH 5, pH 7, and pH 9. The changes to physicochemical properties were probed by SDS-PAGE, FTIR, free sulfhydryl group (SH), surface hydrophobicity (H0), particle size and solubility. As revealed by SDS-PAGE, substantial amounts of 11S globulin participated in the formations of aggregates via Ssingle bondS bond under HHP, particularly at pH 7 and pH 9. However, protein profiles of QPI were not significantly affected by the sonication. Free SH groups and surface hydrophobicity were increased after the sonication treatment indicating protein unfolding and exposure of the embedded SH and/or hydrophobic groups. An opposite trend was observed in HHP treated samples, implying aggregation and reassociation of structures under HHP. HHP and sonication treatments induced a decrease in ordered secondary structures (random coil and β-turn) accompanied with an increase in disordered secondary structures (α-helix and β-sheet) as probed by FTIR. Finally, the sonication treatment induced a significant improvement in the solubility (up to ∼3 folds at pH 7 and ∼2.6 folds at pH 9) and a reduction in particle sizes (up to ∼3 folds at pH 7 and ∼4.4 folds at pH 9). However, HHP treatment (600 MPa) only slightly increased the solubility (∼1.6 folds at pH 7 and ∼1.2 folds at pH 9) and decreased the particle size (∼1.3 folds at pH 7 and ∼1.2 folds at pH 9). This study provides a direct comparison of the impacts of sonication and HHP treatment on QPI, which will enable to choose the appropriate processing methods to achieve tailored properties of QPI.
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    Predicting milk-derived hydrogel-forming peptides with TANGO
    (Elsevier Ltd, 2024-06) Khan MA; Hemar Y; Cheng K-W; Stadler FJ; De Leon-Rodriguez LM
    The uncovering of single peptides derived from food sources that can form hydrogels is of great relevance for several applications. However, identifying single peptide hydrogels from food is a daunting task given the complex nature of the food systems. The proof of concept of the applicability of TANGO, a statistical mechanical-based algorithm that predicts the β-aggregate propensity of peptides, as a tool to uncover peptides derived from milk that can form hydrogels is reported. Using TANGO in conjunction with a set of defined criteria we discovered that from a group of thirteen peptides derived from milk proteins, seven formed hydrogels at a concentration of 2 wt% and pH 7 at room temperature. Three more peptides formed aggregates and appeared to go through the syneresis process, and three additional peptides remained liquid under the experimental conditions. This result sets the basis of a simple methodology for unveiling peptide hydrogels from food and other natural sources.