Characterisation of low fat instant creamy emulsions : effects of different types and concentrations of hydrocolloids and emulsifiers : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Auckland, New Zealand

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Instant creamy oil-in-water (O/W) emulsions prepared by a low shear (i.e. hand shaking) without using high shear forces (e.g. high-pressure homogeniser, microfluidizer, ultrasonicator, etc.) have not been well investigated. This research study was focused initially on the characterisation of instant creamy O/W low shear emulsions containing 40% oil prepared from a base formulation consisting of dry ingredients (starch, xanthan gum, citric acid, egg yolk powder), aqueous liquid (water, Tween 80) and oil (canola oil). The preparation of instant emulsions was conducted by a method called “instantaneous emulsification process” involving simply adding cold water to an oil mixture containing emulsifiers and thickening agents. More specifically, dry ingredients were mixed together (starch, xanthan gum, citric acid, egg yolk powder) and then added into canola oil to form an oil slurry by hand shaking. Then, cold water added with Tween 80 was added into the oil slurry and mixed with a moderate shear generated by hand shaking to form an instant creamy O/W emulsion. Different types and concentrations of starches (Ultra-Tex-4, Ultra- Sperse M, Purity HPC, Novation 5600, Quik-Tex 3331, Instant FTD 176, N-Creamer 46L), hydrocolloids as a cold-hydratable thickening agent (starch, xanthan gum, guar gum, carboxymethyl cellulose, carrageenan) and emulsifier ingredients (egg yolk powder, Tween 80, alpha-cyclodextrin and OSA modified starch) were used to determine their impact on the formation, properties and stability of instant emulsions. The instant emulsion samples prepared were analysed for their appearance, pH, mean particle size and particle size distribution, rheological and textural properties, microstructure (confocal microscope and light microscope images) and emulsion stability (creaming, phase separation, etc.). The results revealed that starch plays an important role on the formation and properties of the instant creamy emulsions. All the physicochemical properties of the instant emulsions characterised by this study were found to be significantly influenced by the types and concentrations of starches that the emulsions were formed with. The most appropriate starch used in this application was found to be a cold water swelling waxy maize starch which was modified chemically by crosslinking and etherification (Ultra-Tex-4). The instant emulsion prepared with 4% w/w of this starch showed desirable viscosity and texture attributes with the pseudoplastic flow behaviour and a relatively small mean particle diameter of 50 µm. In addition, a non-starch hydrocolloid was incorporated into the formulation to enhance the properties of instant emulsions. Carboxymethyl cellulose (CMC) was suitable to be used at a concentration of 0.2–0.4% w/w. The use of CMC aided the formation of instant emulsions with a smaller particle mean diameter of 45 µm and more uniform particle size distribution, and stabilised the instant emulsions by further increasing the viscosity of the emulsions, as well as enhancing the texture attributes and stability of the emulsions. The considerable potential of octenyl succinic anhydride (OSA) modified waxy maize starch (N-Creamer 46L) to emulsify and stabilise the instant emulsions was investigated in this project. It was found that the oil droplets with the smallest particle mean diameters at 45–50 µm could be formed and stabilised in the instant emulsions when prepared with OSA starch at a concentration above 0.1% w/w. However, the possible synergistic effects between the modified starch “Ultra-Tex-4”, CMC and emulsifying OSA starch in instant emulsions at their appropriate concentrations were not investigated in this study, which is recommended for future research. This study provides an important insight into the preparation and characterisation of instant creamy emulsions for applications in food.
Figures 2.1 & 2.8 are re-used with permission. Figures 2.5, 2.6, 2.7 are re-used under a CC Attribution License (CC BY-ND 4.0) and Figure 2.11 under a CC Attribution License (CC BY-NC-SA 3.0). Permission for Figures 2.4 (=Perez et al., 2009 Chapter 5 Fig 5.2) & 2.10 (=Murray, 2009 Chapter 25 Fig 25.2) has not been sought. Other Figures are composite or in the public domain.