| 1. |
- Abdul Hadi, Nabilah Binti
(författare)
-
Short-Chain Fatty Acid Starch Stabilized Pickering Emulsions : Design, Properties and Applications
- 2021
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Pickering emulsions are emulsions stabilized by solid particles. Particles with optimal dual wettability toward both of the oil and water phases, can be adsorbed onto the interface, thereby providing the stability of the emulsions. Starch granules have attracted attention due to their positive characteristics, such as being widely available, inexpensive, biodegradable, and non-allergenic. Due to a relatively low degree of hydrophobicity, chemical modification of starch can improve starch hydrophobicity by esterification with a short-chain fatty acid (SCFA) group. The aim of this thesis was to perform SCFA starch modification by means of esterification of rice and quinoa starches with different SCFA groups and levels of modification. The physicochemical and functional properties of SCFA starches were investigated. As one of the future applications, the emulsifying capacity of SCFA starches was evaluated and in vitro digestion was carried out. Until recently, there have been no studies evaluating the effect of different types of SCFA starches and the levels of modification to the physicochemical properties, emulsification and digestibility. The rationale behind the selection of different types of SCFA starches at different levels of modification and the application of these to stabilize Pickering emulsions were discussed. The esterification of starch with short-chain fatty acids group was successfully quantified by direct stoichiometry, FTIR and 1H-NMR. SCFA starches have shown a different properties compared to their native forms. Native and SCFA-rice starches have a larger particle size compared to native and SCFA-quinoa starches. Both types of starches displayed a polyhedral shape. Upon modification, no changes in particle size were observed. SCFA starches exhibited a reduction in protein and amylose content. SCFA starches demonstrated low gelatinization and pasting temperature. The highest level of resistant starch was observed in the starches with the highest level of modification. Principle component analysis revealed that the physicochemical and functional properties of SCFA starches are highly influenced by the level of modification. SCFA starches were able to perform as a stabilizer in Pickering-type emulsions. The emulsifying capacity was improved by increasing SCFA chain length and levels of modifications. SCFA-quinoa starch Pickering emulsions were observed to have smaller droplet sizes, higher emulsification index, better Turbiscan stability index, and more stable droplet sizes that remained below 50 µm during 50 days of storage. This indicated that Pickering emulsions stabilized by SCFA-quinoa starches were more stable than SCFA-rice starches. In vitro digestion of SCFA starch Pickering emulsions showed that increasing SCFA chain length and modification level reduced the extent of starch hydrolysis. The results of this PhD project implied that increasing the chain length and modification level improved the overall hydrophobicity of the granules and hence improves the emulsification capacity and stability. Improved hydrophobicity resulted in a higher adsorption degree (less free starch) and a denser layer of particles at the interface. Hence, this dense layer protects the oil droplets and prevents the enzyme from getting access to the oil droplets. However, particle coverage was not complete due to the large sizes of the particles. There were therefore still small gaps between starch particles, resulting in lipolysis not being completely arrested. In future research, formulation of SCFA starch Pickering emulsions can be used to investigate the capacity of these emulsions to serve as a carrier for controlled release and targeted delivery of bioactive compounds to a specific location of the gastrointestinal tract, such as the distal locations of the small intestine or the colon.
|
|
| 2. |
- Boostani, Sareh, et al.
(författare)
-
The influence of emulsion parameters on physical stability and rheological properties of Pickering emulsions stabilized by hordein nanoparticles
- 2020
-
Ingår i: Food Hydrocolloids. - : Elsevier BV. - 0268-005X. ; 101
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, the effect of pH (3–8), ionic strength (I, 0.01–1 M), protein particle concentration (C, 0.5%–2%), and dispersed phase volume fraction (Φ, 0.25–0.8) on the efficacy of hordein-based colloidal nanoparticles in the stabilization of Pickering structures was investigated. Colloidal particles were synthesized via anti-solvent method. Depending on pH and I, the average size and zeta-potential of hordein particles ranged from 425 to around 4000 nm, and +27.5 to −15.63 mV, respectively. The intense aggregation of particles at pH close to isoelectric point and also at high I led to poor formation and stability of Pickering emulsions. The overrun value was influenced by various emulsion parameters. At pH 3, triphasic (with the overrun value of 75%) and high internal phase (HIP) emulsions with an average droplet size of 15.6–86.7 μm were formed at Φ 0.25 and 0.8, respectively. At Φ 0.5 and 0.8, an elastic gel-like behavior (i.e., storage modulus (G′) > loss modulus (G″)) was observed over the applied frequency range. At Φ 0.25, a predominant viscous character (G">G′) was observed at low frequencies; while, at higher frequencies, G′ exceeded G″ due to the foam collapse. The morphology was studied by optical microscopy and confocal laser scanning microscopy (CLSM). Monitoring the physical stability using static multiple light scattering (MLS) revealed three destabilization profiles of foam-like, emulsion-foam and gel-like structures. The results of this study might help in designing triphasic Pickering systems (using plant-based proteins) and developing solid-like structured vegetable oils from the gel-like HIP emulsions.
|
|
| 3. |
- Hadi, Nabilah Abdul, et al.
(författare)
-
Comparison of three methods to determine the degree of substitution of quinoa and rice starch acetates, propionates, and butyrates : Direct stoichiometry, FTIR, and 1H-NMR
- 2020
-
Ingår i: Foods. - : MDPI AG. - 2304-8158. ; 9:1
-
Tidskriftsartikel (refereegranskat)abstract
- Rice and quinoa starch esters were prepared by acylation using short-chain fatty acid anhydrides with different chain lengths (acetic, propionic, and butyric anhydride). A direct stoichiometric method based on the acylation reaction was used to determine the degree of substitution (DS) and acyl content (AC). In addition, Fourier-transform infrared spectroscopy (FTIR) was used to validate the conformational changes of acylated starch and 1H-NMR was used as a DS reference method. DS by stoichiometric calculation was shown to be in agreement with FTIR and was comparable with DS obtained from Proton nuclear magnetic resonance (1H-NMR). Based on this study, stoichiometric calculation allows rapid and direct determination of substitution levels and acyl content without the loss of samples, which provides efficiency and optimization of manufacturing procedures in producing the desired level of esterified starches.
|
|
| 4. |
- Marefati, Ali, et al.
(författare)
-
In vitro intestinal lipolysis of emulsions based on starch granule Pickering stabilization
- 2019
-
Ingår i: Food Hydrocolloids. - : Elsevier BV. - 0268-005X. ; 95, s. 468-475
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of barrier properties on in vitro intestinal lipolysis of three different types of emulsions based on oil-in-water starch granule Pickering stabilization has been investigated including non-heat treated, heat treated (gelatinized) and heat treated and stored (retrograded) emulsions. The stability of starch covered oil-water interfaces towards in vitro intestinal lipolysis was correlated to the rate of lipid hydrolysis using a pH-stat method. The results were compared with a sodium caseinate stabilized emulsion. The shape and size of the starch granules were characterized by scanning electron microscopy and light scattering. The physical properties of the emulsions were characterized by a light scattering particle size analyzer and light microscopy. In all cases, Pickering emulsions showed lower extents of lipolysis compared to the protein stabilized emulsion. In addition, heat treated starch Pickering emulsions were more susceptible to lipolysis compared to freshly prepared emulsions with no heat treatment. This was thought to be due to the gelatinized starch barrier being more susceptible to amylase present in the pancreatin. The results of this study demonstrate the interfacial layer properties can affect the rate and extent of lipolysis.
|
|
