Preparation and characterisation of a novel emulsifier system based on glycerol monooleate by spray-drying

Dedicated to the memory of E. John Birch, who tragically passed away in March 2019
https://doi.org/10.1016/j.jfoodeng.2020.110100Get rights and content

Highlights

  • Spray-drying turned oil-soluble glycerol monooleate (GMO) to an instantised powder.

  • All GMO powders were soluble and easy to disperse in water.

  • GMO powders formed stable droplets with no phase separation after reconstitution.

Abstract

Glycerol monooleate (GMO) improves creaming stability in protein-stabilised emulsions but is unsuitable for direct aqueous applications due to its low solubility in water. Encapsulation could transform waxy solid GMO into a water-dispersible powder. This study assessed spray-drying to produce instantised GMO powders, and investigated emulsion formulation (GMO concentration (33.6%, 47.0%); dextrose equivalent (DE) values of maltodextrin (DE 10, 18)) on emulsion and powder properties. Results showed that all homogenised emulsions were suitable for spray-drying due to their high emulsion stability, monomodal droplet size distributions (150–180 nm) and low viscosity (20–65 mPa s). All instantised powders exhibited good dispersibility (65–90%) in water. The instantised powder with low GMO levels showed high encapsulation efficiencies (93–94%) with low surface oils (3%) and uniform droplet size distributions when reconstituted. Results demonstrated that spray-drying can successfully produce instantised powders for food applications to improve product quality.

Introduction

Monoglycerides are common food emulsifiers typically used in foods and beverages such as coffee creamers, creams, margarine, ice cream and dairy beverages (Kantekin-Erdogan et al., 2019; Moonen and Bas, 2007). Monoglycerides are amphiphilic molecules with one hydrophobic fatty acid esterified to hydrophilic glycerol, making them surface-active molecules (Krog and Vang Sparsø, 2003). Monoglycerides are readily adsorbed to the oil-water interface and lower the interfacial tension to facilitate emulsion formation. However, monoglycerides are oil-soluble molecules with poor dispersion in water, which limits their application in the industry.

While there is a wide range of commercial monoglycerides available, glycerol monostearate (GMS) and glycerol monooleate (GMO) are both typically used as emulsifiers (Miao and Lin, 2019). GMS is a saturated monoglyceride (mostly comprised of stearic acid and palmitic acid) and can be easily incorporated with co-emulsifiers such as sodium stearate to improve dispersion in water (Krog and Vang Sparsø, 2003). In contrast, GMO is an unsaturated monoglyceride comprised of oleic acid that is waxy solid at room temperature and has been under-utilised in food formulations due to poor dispersibility in water. In our previous study (Loi et al., 2019), results showed the potential use of GMO to achieve both good physicochemical properties and creaming stability in protein-stabilised emulsions. Thus, there is a need to transform GMO into a powder with good dispersibility in water for use in food formulations.

Spray-drying is a process widely used in the food industry for encapsulation of oils rich in unsaturated fatty acids (Carneiro et al., 2013; Jafari et al., 2008b; Turchiuli et al., 2005b). The dried powder results in low water activity, easy handling and storage, good stability and uniform dispersion into food formulations (Bae and Lee, 2008; Vega and Roos, 2006). Maltodextrin is commonly used as a wall material in spray-drying due to its relatively low cost, neutral odour and taste, minimal effect on viscosity, and good protection against undesired reactions, such as oxidation (Carneiro et al., 2013; Vega and Roos, 2006). Due to the weak emulsifying properties of maltodextrin, it is usually used together with sodium caseinate to improve the emulsifying and interface properties of lipophilic core materials (Hogan et al., 2001b).

A review paper by Lee et al. (2018) summarised the effect of emulsifier type and concentration on the spray-drying process and resulting powder properties, but to the authors best knowledge no published research article has specifically examined the encapsulation of emulsifiers, especially monoglycerides. The encapsulation of emulsifiers such as GMO has the potential to produce valuable ingredients to the food and ingredient industries. In this study, we report on the feasibility of using spray-drying for the preparation of a novel emulsifier system based on GMO. This study also compares the effect of two GMO levels and two types of maltodextrin on emulsion and particle properties of an instantised GMO. As the main aim of this experiment was to evaluate the feasibility of producing an encapsulated emulsifier system rather than optimising the spray-drying formulation and process, the two-level design is sufficient to compare these parameters on emulsion and particle properties.

Section snippets

Materials

Glycerol monooleate (Radiamuls MG 2905K) (containing at least 90% monoglyceride) was a gift from Oleon (Klang, Malaysia). Sodium caseinate was provided by Tatua Co-operative Dairy Company Ltd. (Morrinsville, New Zealand), while sodium stearate was supplied by Peerage Product Limited (Christchurch, New Zealand). Maltodextrin with dextrose equivalent (DE) values of 10 and 18 were purchased from Hawkins Watts Ltd. (Auckland, New Zealand) and Davis Food Ingredients (Auckland, New Zealand),

Droplet size

Table 2 shows the resistance to phase separation, rheological properties, droplet size and polydispersity index of all pre-drying emulsions. Droplet size of the emulsions (initial and aged for 24 h) was not affected by the DE value of maltodextrin but was dependent on the GMO level. Droplet size increased significantly when GMO level increased from low to high. The increase in the ratio of core to wall material from 0.95 to 2.13 may lead to coalescence or merging of oil droplets during

Conclusions

This study compared the DE value of two maltodextrins and two GMO levels on emulsion and particle properties of an instantised GMO powder prepared by spray-drying. The DE value of maltodextrin had a smaller effect on the emulsion and powder properties compared to the GMO level. Comparing the low GMO (33.6%) level to the high GMO (47.0%) showed that high GMO level in emulsions resulted in larger droplets and higher viscosity and dried powders with lower encapsulation efficiency, higher surface

CRediT authorship contribution statement

Chia Chun Loi: Conceptualization, Methodology, Formal analysis, Investigation, Writing - original draft, Writing - review & editing. Graham T. Eyres: Conceptualization, Writing - original draft, Writing - review & editing, Supervision. Pat Silcock: Conceptualization, Writing - original draft, Writing - review & editing, Supervision. E. John Birch: Conceptualization, Supervision.

Declaration of competing interest

The authors declare that there are no conflicts of interest.

Acknowledgements

Chia Chun Loi would like to acknowledge a University of Otago Doctoral Scholarship towards his PhD study and a University of Otago Doctoral Postgraduate Publishing Bursary. Thanks to Nerida Downes and Roy Ma from the University of Otago, Product Development Research Centre for their assistance in the preparation of instantised GMO powders by spray-drying.

References (38)

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