Evaluation of native and modified Dioscorea hispida starches for use in Pickering emulsion stabilisation

Design and synthesis of modified and resistant starch-based oil-in-water emulsions

Waxy and non-waxy rice starches from japonica type Korean rice varieties were esterified with different levels of octenyl succinic anhydride (OSA), and the molecular structure of amylopectin (AP), digestibility, and emulsion stability were investigated. As OSA levels increased, the degree of substitution, granule size, peak and final viscosities, emulsion stability, and short chain of AP increased. However, the gelatinization temperature and enthalpy, and digestibility decreased. All OSA esterified starches showed a new band at 1723 cm−1, but maintained A-type crystallinity. The DP6-12 of AP in waxy rice starch (WRS) was higher than that in non-waxy rice starch (NRS) with increasing OSA levels. Because the amylose and long chain of AP accessed easily with OSA groups, the digestibility of NRS was lower than that of WRS. The emulsion stability was higher in WRS than in NRS. From the above results, it is suggested that amylose should have a higher affinity with OSA esterification than AP and that the emulsion stability should increase in WRS, but the digestibility should decrease in NRS after OSA modification.

Characterization and emulsifying properties of octenyl succinate anhydride modified Acacia seyal gum (gum arabic)

Surfactants are used to reduce surface and interfacial tension to form emulsions. Polysaccharides such as Porang Glucomannan (PG) with high viscosity can be used as surfactants. This research aimed to optimize the concentration of sodium carbonate (Na2CO3) and octenyl succinic anhydride (OSA) in modifying PG using a microwave. The optimization process is carried out using response surface methodology (RSM) with a two-factor central composite design (CCD), namely concentration of Na2CO3 (0.17–5.834%) and OSA (2.17–7.83%). The result showed that the concentration of Na2CO3 and OSA strongly influences emulsion capacity and stability. The optimum conditions that resulted in the highest emulsion capacity and stability were obtained at concentrations of Na2CO3 and OSA which were 2.25% and 6.19%, respectively. Degree of Substitution (DS), FTIR analysis, contact angle, and increased viscosity confirmed that OSA substitution occurred in PG. The characteristics of OSA-modified porang glucomannan (PGOS) such as: emulsion capacity and stability, Degree of Substitution (DS), contact angle, and viscosity increased to 34.6% and 32.5%, 1.02%, 92o, 5720 cP, respectively. FT-IR analysis confirmed the presence of OSA substitution at 1734 cm−1. PGOS can be used as a surfactant or gelator in oleogel production.

Preparation and characterization of emulsion stabilized by octenyl succinic anhydride-modified dextrin for improving storage stability and curcumin encapsulation

This work investigates the stability of emulsions prepared by using octenyl succinic anhydride (OSA)-modified waxy maize starch in the form of granules, dissolved starch, and non-solvent precipitated starch as Pickering emulsion stabilisers. The aim of this study was to investigate the effects of different forms of starches on the stability of emulsion using light microscopy, light scattering, and static multiple light scattering. All starch samples were hydrophobically modified with 3% (w/w) n-octenyl succinyl anhydride (OSA). Starch polymer solutions were prepared by dissolving OSA- modified starch in water in an autoclave at 140°C. Non-solvent precipitates were obtained through ethanol precipitation of dissolved waxy maize. The stability of the oil/water emulsions were different for the three forms of starches used. The granule-based emulsions were unstable, with only a small proportion of the granules adsorbed onto oil droplets, as viewed under a light microscope. The emulsions were observed to cream after 2 hours. The dissolved starch and non-solvent precipitate-based emulsions were stable towards creaming for months, and they had almost 100% emulsifying index (EI = 1) by visual observation and EI ~ 0.9 by multiple light scattering measurements. The results from light microscopy and multiple light scattering measurements indicated the occurrence of coalescence for all three types of emulsions. The coalescence was fastest within days for the granule stabilised system while it was slower both for the dissolved starch and non-solvent precipitate-based emulsions. The latter demonstrated the least degree of coalescence over time. Thus, it was concluded that differences in starch particle size and molecular structure influenced the emulsion droplet size and stability. A decreased particle size correlates to a decrease in droplet size, thus increasing stabilisation against creaming. However, stability towards coalescence was low for the large granules but was best for the non-solvent precipitate starch indicating that there is a window of optimal particle size for stability. Thus, best emulsifying properties were obtained with the non-solvent precipitates (~ 120 nm particle size) where the emulsions remained stable after one year of storage. In conclusion, this study illustrated the potentiality of non-solvent precipitated starch as emulsion stabilizers.

Controlling the structure and Pickering emulsion stability of OSA starch nanoparticles by varying the ratio of choline glycine ionic liquid.

The reaction between starch granules and octenyl succinic anhydride (OSA) is regularly retarded due to the low breakthrough of large oily OSA droplets into starch granules in an aqueous reaction system. Furthermore, high-speed shearing is widely used in the food industry, demanding high shear, cavitation, and collision force. In this sense, high-speed shearing could reduce the size of OSA droplets and promote a more homogeneous distribution of groups in the starch granule. The aim of this study was to evaluate the impact of OSA potato starch synthesis assisted by high-speed shear on structure (SEM and FTIR), gelatinization, rheology, and emulsifying activity (ES and AS) was investigated. The results showed a gradual increase in DS proportional to the applied speed. Likewise, the OSA starches showed a slight alteration in the shape of the granules (SEM), and FT-IR spectroscopy showed a characteristic absorption of the ester carbonyl groups in the OSA starch at 1724 cm-1. The high-speed shear-treated starches exhibited a significant change in the reduction of the initial gelatinization temperature, although not in the enthalpy. All the gels presented rheology adjusted to the Herschel-Bulkley model with variations in the initial shear stress. Changes in the viscoelastic behavior are proportional to the shear rate detected. High-speed shear treatment did not show a significant effect on emulsion stability (ES) and emulsion activity (EA). Consequently, applying high shear rates allows having OSA starches with different uses.

Changing the physicochemical properties of starch by chemical modification is a common process. Starches can be modified to alter their hydrophobicity by treatment with octenyl succinic anhydride (OSA). The physicochemical properties of OSA starches from corn, tapioca, rice, potato and wheat were studied. The increase of swelling volume and pasting properties in OSA starches was observed and attributed to the introduction of OSA groups into the starch. However, the botanical source also played a key role in starch swelling and pasting properties. The OSA modification improved the textural properties, while not significantly (P < 0.05) affecting the thermal properties. Therefore, it was found that the level of OSA substitution and the botanical sources affected the physicochemical properties. However, it will be important to investigate the chemical properties and starch backbone structure of the modified starches, factors that play an important role in the physicochemical properties. Practical Applications Modified starches are important in development of new food products with regards to both processing properties and end-product properties. Esterification of starch with octenyl succinic anhydride (OSA) alters the swelling power, paste viscosity, gel texture and retrogradation of starches. OSA starches also have emulsification capacity which makes them useful as emulsion stabilizers, texturizers and fat-replacers in food systems. However, the botanical source of the starch plays a key role in the functionality of both native and modified starches. It is important to ascertain the properties of OSA modified starches prepared from various botanical sources to determine how the interaction of OSA esterification and botanical source will affect the functionality of the starches.

This thesis is the first comprehensive study into the relationship between starch structure and the functional properties of its derivatives made by modification with octenylsuccinic anhydride (OSA). Several new methods have been developed in the process of this work, using a range of purposefully created octenylsuccinylated (OS) starches with controlled structures. Chapter 1 is a general introduction to the science involved and the state of the art. Chapters 2 to 4 explore methods in the development of structurally targeted OS starches. Chapters 3, 5 and 6 report the results from some analyses. As outlined in Chapter 1, OS starches represent an economically important product that has existed for many decades, but has recently shown significant growth in interest as seen in scientific literature. The reasons for this impressive surge in interest reflects the wide range of applications and versatility OS starches, determined primarily from the structural properties of the starch substrate. With that in mind, it is surprising that, to date, most interest has been focussed on conditions of the OSA modification process, rather than the structure-function relationships. After a comprehensive state-of-the-art review, this thesis has identified the important areas where structure-function research of OS starches should focus in-depth to provide the most thorough innovation in the field. Throughout, size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) have been used for structural analysis, while gel properties and emulsion function have been determined using a wide range of methods. Chapter 2 outlines NMR methods that were developed specifically for this project. It has been determined that the ideal system for analysing OS starches by NMR utilises 64 to 128 scans in deuterated dimethylsulfoxide (DMSO-d6) of at least 50 °C containing at least 22 mg mL-1 deuterated trifluoroacetic acid (TFA-d1), as has been published and improved upon during the course of this thesis. The method utilises the signal from the proton attached to the 5th Carbon residue of the octenyl tail to determine the number of OS groups, and compares that to the total number of monomers by the addition of α-(1→4), α-(1→6) and reducing end signals. The signal of the 5th proton is unique, because it neighbours the double bond. Due to the susceptibility of the double bond to the effects of TFA-d1, the analysis must be performed very quickly for best results. By this method it is possible to determine the degree of branching (DB) and the degree of OS substitution (DS) using the one simple analysis. Because it also accurately measures DB, the same method has proven useful for non-OSA-modified starches. Chapter 3 is an overview of the development and initial application of a method to determine the critical aggregation concentration (CAC, sometimes called “critical micelle concentration”, though the aggregates formed by OS starches are not by definition micelles). The method uses pyrene fluorescence and can be adapted for other polymeric surfactants, and has been used in this first instance to investigate a range of acid-hydrolysed starches. These starches were prepared by reaction with HCl in various alcoholic solvents. Acid hydrolysis has been found to be ideal for creating starch substrates of tailored hydrodynamic volume (Vh), with fairly low dispersity. The values determined by CAC analysis reflect the capacity of the surfactant to interact with itself and with interfaces, and are a useful and simple method of comparing surfactants; however, the results do not always translate directly into emulsion stability or overall quality. As outlined, OS starches from highly branched substrates show similar CAC characteristics to those seen with more linear synthetic polymer surfactants. Chapter 4 deals with the β-amylolysis of OS starch, particularly the effect of OS groups on the β-amylase activity. To achieve this, starches from waxy sorghum and waxy maize were modified with OSA to a range of DS, including very high levels beyond those used in industry. Hydrolysis by β-amylase was performed on both granular and gelatinised starches. Because the OSA modification process is on starch in granular form the reaction is heterogeneous with those areas accessible to the solvents more readily accessible; similarly, β-amylolysis in granular form restricted access of the enzyme to many of the same areas of the granule in which the esterification had predominantly occurred, whereas in gelatinised form the β-amylase activity was much more unhindered. The activity of the enzyme was somewhat diminished by the presence of OS groups, though the results were not so conclusive as to indicate complete blocking of the enzyme activity along individual branches. Chapter 5 introduces the critical test of emulsion capacity and stability, as well as an important method for determining the breakdown of β-carotene in the oil phase of emulsions. The method is an accelerated test at high storage temperature that can determine the oxidative effects on any labile components in the oil phase. The methods of acid hydrolysis used in Chapter 5 are similar to those in Chapter 3; however, the spectrum of samples is more broad and encompasses a range of structural variables. Amylose/amylopectin ratio is used as a simple method of controlling the DB, and the molecules are reduced to controlled sizes through the use of acid hydrolysis in alcohols. Methods for determining the quality of starch surfactants in the formulation and stabilisation of emulsions use high-pressure homogenisation (HPH) and track the development of pigment and droplet size during incubation at 55 °C over 20 days. The results of these tests indicate that samples containing many short branches from amylopectin are more stable than those containing longer amylose chains, regardless of the overall degree of branching (DB) of the surfactant. The effects of shear scission during HPH are also elucidated in this chapter to a greater extent than has previously been demonstrated with OS starches. Chapter 6 brings together the methods from all previous chapters to determine the CAC, emulsion capacity and stability and oxidative stability of β-carotene dissolved in the oil phase of several waxy maize and sorghum starches, after they were modified with OSA, structurally modified with β-amylase or pullulanase, and characterised using SEC and NMR. The size of oil droplets in emulsion can be higher in samples of larger Vh without any sacrifice to emulsion stability, probably due to the layer thickness at the interface. Larger molecules of amylopectin also result in better chemical stability of β-carotene and lower CAC; however, attempts to artificially increase DB by treatment with β-amylase have a detrimental effect to emulsion stability, while lowering the degree of branching with pullulanase does not show the inverse effect. As a result of this thesis, several advances have been made in the field of OS starch science. The common empirically based tendency of industrially prepared OS starches to be based on waxy starches and prepared by HPH has been validated by the findings that hydrodynamic size and short branch length contribute to the quality of emulsion formulations. Treatment of industrial starches with β-amylase does not lead to useful surfactant properties, and from the results of this study such methods can be excluded from future consideration. This thesis is the first document in the field to indicate that higher DB does not directly lead to better emulsions, rather than the presence of short linear branches in a mix also containing larger, branched molecules. Waxy sorghum has been established as a viable source of OS starch substrate, opening up opportunities for future research and industrial production in the Australian market.

Characteristics of low-fat mayonnaise using different modified arrowroot starches as fat replacer

Preparation and characteristics of octenyl succinic anhydride-modified partial waxy rice starches and encapsulated paprika pigment powder

Dynamic high-pressure microfluidization assisting octenyl succinic anhydride modification of rice starch

Atmospheric pressure plasma jet pretreatment to facilitate cassava starch modification with octenyl succinic anhydride

Fabrication and characterization of pickering emulsions stabilized by octenyl succinic anhydride -modified gliadin nanoparticle