Article pubs.acs.org/JAFC
Formation of Oil-in-Water Emulsions from Natural Emulsifiers Using Spontaneous Emulsification: Sunflower Phospholipids Jennifer Komaiko,† Ashtri Sastrosubroto,† and David Julian McClements*,†,§ †
Department of Food Science, University of Massachusetts, Amherst, Massachusetts 01003, United States Department of Biochemistry, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia
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ABSTRACT: This study examined the possibility of producing oil-in-water emulsions using a natural surfactant (sunflower phospholipids) and a low-energy method (spontaneous emulsification). Spontaneous emulsification was carried out by titrating an organic phase (oil and phospholipid) into an aqueous phase with continuous stirring. The influence of phospholipid composition, surfactant-to-oil ratio (SOR), initial phospholipids location, storage time, phospholipid type, and preparation method was tested. The initial droplet size depended on the nature of the phospholipid used, which was attributed to differences in phospholipid composition. Droplet size decreased with increasing SOR and was smallest when the phospholipid was fully dissolved in the organic phase rather than the aqueous phase. The droplets formed using spontaneous emulsification were relatively large (d > 10 μm), and so the emulsions were unstable to gravitational separation. At low SORs (0.1 and 0.5), emulsions produced with phospholipids had a smaller particle diameter than those produced with a synthetic surfactant (Tween 80), but at a higher SOR (1.0), this trend was reversed. High-energy methods (microfluidization and sonication) formed significantly smaller droplets (d < 10 μm) than spontaneous emulsification. The results from this study show that low-energy methods could be utilized with natural surfactants for applications for which fine droplets are not essential. KEYWORDS: spontaneous emulsification, emulsion, natural surfactants, sunflower, phospholipids, low-energy methods
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INTRODUCTION Oil-in-water emulsions can be found in a variety of food and beverage products, including creams, desserts, dressings, dips, milks, sauces, and soft drinks.1 These emulsions can be formed using either high-energy or low-energy methods. High-energy approaches, such as colloid mills, high-pressure homogenizers, sonicators, and microfluidizers, rely on specialized equipment to disrupt and intermingle the oil and water phases, thereby forming small droplets.2 In contrast, low-energy approaches require no specialized equipment and utilize the physicochemical properties of the surfactant, oil, and water system to spontaneously generate emulsion droplets by simple mixing procedures or by simply changing environmental conditions such as temperature.3,4 High-energy methods are currently the most commonly used in the food industry because they are already well-established, are capable of large-scale production, and can produce emulsions and nanoemulsions from a range of components.5 Low-energy methods, however, are of growing interest due to their low cost and ease of implementation.6 A major drawback of high-energy methods is the requirement for relatively expensive specialized equipment, such as colloid mills, sonicators, high-pressure homogenizers, or microfluidizers.7 Sonication has been used to form emulsions from a variety of different oils and surfactants.8−11 It has advantages such as requiring low surfactant concentrations, being fairly energy-efficient, having low production costs, and being easy to operate, clean, and control.2 However, scaling up from the laboratory to an industrial-scale food processing operation has been a major challenge.12 High-pressure homogenization can be achieved using specialized equipment such as high-pressure valve homogenizers (HPVHs) and microfluidizers. HPVHs are currently the most common method of producing fine © 2015 American Chemical Society
emulsions in the food industry and involve forcing a coarse emulsion through a narrow gap at high pressure. Microfluidizers have been shown to be one of the most efficient systems for producing fine emulsions13 and are therefore gaining increasing application within the food industry. Inside a microfluidizer, an emulsion is split into two channels, and then the two channels are directed toward each other in an interaction chamber. As a result, intense disruptive forces are generated within the interaction chamber that lead to highly efficient droplet fragmentation.5 Whereas high-energy approaches are based on the utilization of specialized mechanical homogenizers, low-energy approaches require only a simple low-intensity mixer. Numerous lowenergy methods are available that can be broadly categorized into two classes: thermal methods, which rely on a change in temperature; and, isothermal methods, which rely on a change in system composition.6 On an industrial scale, the isothermal methods are likely to be easy to implement because rapidly changing the temperature of large volumes of fluids, which is required for the thermal methods, may be difficult and expensive. Of the isothermal methods, spontaneous emulsification has the most potential for commercial applications. When an oil-in-water emulsion is made, the volume of the organic phase is usually less than that of the aqueous phase. In spontaneous emulsification, where the organic phase is added into the aqueous phase, this makes the technique easier to Received: Revised: Accepted: Published: 10078
August 17, 2015 October 30, 2015 November 3, 2015 November 3, 2015 DOI: 10.1021/acs.jafc.5b03824 J. Agric. Food Chem. 2015, 63, 10078−10088
Article
Journal of Agricultural and Food Chemistry Table 1. Properties of the Sunflower Phospholipids Used in This Study (As Provided by the Manufacturer) wt %a
a
phospholipid
Sunlipon 50
phosphatidylcholine 1-lysophosphatidylcholine 2-lysophosphatidylcholine phosphatidylinositol lysophosphatidylinositol phosphatidylserine-sodium lysophosphatidylserine sphingomyelin phosphatidylethanolamine lysophosphatidylethanolamine acyl-phosphatidylethanolamine phosphatidylglycerol phosphatidic acid lysophosphatidic acid other
58 1 3 1 − − − − 5 1 3 1 − 0.2 2
total 14:0 15:0 16:0 16:1 17:0 18:0 18:1 18:2 18:3 20:0 20:1 22:0 24:0
59.3 0.1 0.02 5.8 0.04 0.1 1.6 9.8 40.8 0.1 0.1 0.1 0.2 0.1
fatty acids myristic pentadecanoic palmitic palmitoleic heptadecanoic stearic oleic linoleic α-linolenic arachidic eicosenoic behenic lignoceric
Sunlipon 65
(a) Phospholipid Information 65 1 5
