Modulation of caseinate-stabilized model oil-in-water emulsions with soy lecithin

Accepted Manuscript Modulation of caseinate-stabilized model oil-in-water emulsions with soy lecithin

Cheryl Chung, Charmaine K.W. Koo, Alexander Sher, Jun-Tse R. Fu, Philippe Rousset, David Julian McClements PII: DOI: Reference:

S0963-9969(19)30264-9 https://doi.org/10.1016/j.foodres.2019.04.032 FRIN 8413

To appear in:

Food Research International

Received date: Revised date: Accepted date:

29 November 2018 24 January 2019 15 April 2019

Please cite this article as: C. Chung, C.K.W. Koo, A. Sher, et al., Modulation of caseinatestabilized model oil-in-water emulsions with soy lecithin, Food Research International, https://doi.org/10.1016/j.foodres.2019.04.032

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ACCEPTED MANUSCRIPT Modulation of Caseinate-stabilized Model Oil-in-Water Emulsions with Soy Lecithin Cheryl Chung1, Charmaine K. W. Koo1, Alexander Sher2, Jun-Tse R. Fu2, Philippe Rousset2, David Julian McClements1*

Nestlé Development Center Marysville, 809 Collins Avenue, Marysville, OH, 43040, USA

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University of Massachusetts, Department of Food Science, Amherst, MA, 01003, USA.

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Journal: Food Research International

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Submitted: November 2018

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To whom correspondence should be addressed.

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Tel: (413) 545-1019; Fax: (413) 545-1262.

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E-mail: [email protected]

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Abstract Demands for plant-based food and beverage products have escalated in recent years. However, many commercial coffee creamers are still being made using dairy derivatives such as sodium caseinate. Therefore, there is a need to investigate the replacement of dairy based proteins with plant-based alternatives. This study was carried out to systematically investigate the

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properties of model O/W emulsions stabilized by either sodium caseinate (0.25 to 1.5%) or soy

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lecithin (0.5 to 1.5%). The model emulsions were made of 10% medium chain triglyceride (MCT)

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oil-in-water emulsions at pH 7. All model O/W emulsions exhibited whitish appearances similar to that of commercial creamers and were effective at lightening black coffee, except those

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containing the lowest emulsifier concentrations i.e., 0.25% caseinate or 0.5% lecithin. The lightness of the model emulsions depended on the type and level of emulsifier used, with soy

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lecithin-stabilized emulsions having similar lightening power compare to that stabilized by sodium caseinate. No feathering or free oil were observed in the whitened coffees at the highest emulsifier level used. Mixtures of caseinate and lecithin emulsifiers were also used and model O/W emulsions

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with similar physical properties to that stabilized by sodium caseinate alone were produced. The

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mixed emulsifier-stabilized model emulsions had similar lightness when added to coffee than those stabilized by the individual emulsifiers, suggesting similar stabilization mechanisms using these

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emulsifiers alone or in combination.

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Feathering

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Keywords: Emulsion; Coffee Creamer; Sodium Caseinate; Soy Lecithin; Plant-Based Emulsifier;

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1. Introduction Consumers are demanding more natural plant-based food products for various reasons, including personal health, ethics, and environmental sustainability (Cliceri, Spinelli, Dinnella, Prescott, & Monteleone, 2018; de Boer, de Witt, & Aiking, 2016; Hedenus, Wirsenius, & Johansson, 2014; Stubbs, Scott, & Duarte, 2018). In response, manufacturers are reformulating

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many of their products to replace synthetic or animal-based ingredients with plant-based

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alternatives. Extensive research and development are required to understand the properties of these

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less commonly used plant-based ingredients and their potential impact on the properties of final products.

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Creamers containing oil-in-water (O/W) emulsions are usually stabilized by dairy-based proteins, such as sodium caseinate, generally in combination with low molecular weight

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emulsifiers (Abdullah, Malundo, Resurreccion, & Beuchat, 1993; Golde & Schmidt, 2005). However, plant-based alternatives to milk and cream have already gained widespread acceptance

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in the market, such as soy, almond, coconut, rice, and oat milks. These plant-based milks, however, often have physical and sensory properties that are not perceived as being as desirable as dairy-

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based creamers (Jeske, Zannini, & Arendt, 2017; Sethi, Tyagi, & Anurag, 2016). More recently, plant-based natural emulsifiers were used to stabilize oil-in-water emulsion in model coffee

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creamers (Chung, Sher, Rousset, Decker, & McClements, 2017a; Chung, Sher, Rousset, & McClements, 2017b). There is therefore a search for plant-based emulsifiers to replace caseinate,

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but still provide the required physicochemical properties, sensory attributes, and stability in the final product (Makinen, Wanhalinna, Zannini, & Arendt, 2016; Sethi et al., 2016).

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The aim of this study was to study the properties of model emulsions stabilized fully or partially with plant-based emulsifiers. Initially, we systematically characterized the physical properties of model oil-in-water emulsions stabilized with sodium caseinate. Subsequently, we fabricated model oil-in-water emulsions using soy lecithin as a plant-based alternative emulsifier to sodium caseinate. In the final part of the study, we examined the possibility of using mixtures of sodium caseinate and soy lecithin in different ratios to stabilize the oil-in-water emulsions. Previous researchers have investigated the use of caseinate and/or soy lecithin for formulating emulsions but these studies were not focused on the potential application of these emulsions in

ACCEPTED MANUSCRIPT coffee systems (Golde & Schmidt, 2005; Rosida, Mulyani, & Septalia, 2016; Xue & Zhong, 2014; Yesiltas, Garcia-Moreno, Sorensen, Akoh, & Jacobsen, 2019). The results from this investigation provide valuable information for the more rational design of plant-based alternatives to O/W emulsions stabilized using dairy-based emulsifiers, as well as for creamers that contain lower

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amounts of milk-based protein.

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2. Materials and methods

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2.1 Materials

NZMP sodium caseinate (Alanate™ 180) was obtained from Fonterra (Rosemont, IL, USA). Soy lecithin (Solec® F), reported to have a Hydrophilic-Lipophilic Balance (HLB) of around 7 and

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to contain around 97% of surface active component, was kindly provided by DuPont Danisco (St. Louis, MO, USA). Medium chain triglyceride was purchased from the Warner Graham Company

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(Miglyol 812N, Cockeysville, MD, USA). A dark roast grade instant coffee powder (Nescafe Clásico, Dark Roast, Nestlé, Switzerland) was purchased from a local supermarket. The chemicals

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used, including hydrochloric acid, sodium hydroxide, potassium phosphate, calcium chloride, and magnesium chloride were of chemical grade and purchased from Fisher Scientific Company LLC

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(Pittsburgh, Pennsylvania, USA). Other chemicals, namely Nile red and fluorescein isothiocyanate isomer 1 were obtained from Sigma-Aldrich (St. Louis, MO, USA). All solutions prepared in this

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study were carried out on weight per weight basis and represented as percentage (%).

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2.2 Preparation of model oil-in-water emulsions Model oil-in-water emulsions containing varying concentrations of individual emulsifiers

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[sodium caseinate (0 to 1.5%) or soy lecithin (0 to 1.5%)] or combinations of sodium caseinate (0.25 to 1.5%) and soy lecithin (0.5 to 1.5%) were prepared with 10% medium chain triglyceride (MCT). Weighed amounts of the water-soluble sodium caseinate powder and oil-soluble lecithin powder were reconstituted in the aqueous phase (0.4% potassium phosphate solution pH 7) and oil phase (MCT), respectively and stirred at room temperature (20 – 22C) until fully dissolved. The oil phase was then blended with the caseinate solution using a high shear mixer (15,000 rpm for 1 min) (Bamix, Biospec Products, Bartlesville, Oklahoma, USA) to produce coarse emulsions. These coarse emulsions were further processed by passing them once through a high pressure microfluidizer (Microfluidizer M-110P, Microfluidics, Newton, MA, USA) at 5000 psi. The pH

ACCEPTED MANUSCRIPT of the model oil-in-water emulsions was adjusted to pH 7 with solution of sodium hydroxide or hydrochloric acid, if required.

2.3 Preparation of coffee solutions A black coffee solution (1%) containing 270 ppm water hardness (commonly expressed as ppm equivalent of calcium carbonate, CaCO3) was prepared. A calculated amount of calcium

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chloride (1.95 mM) and magnesium chloride (0.62 mM) were dissolved in boiled deionized water

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to prepare mineral solution to imitate tap water with high hardness CaCO3 found in some areas in

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the USA. Then a calculated amount of instant coffee powder was dissolved in the hard water to prepare black coffee solution. An aliquot (10 mL) of model O/W emulsion was dispensed immediately into 60 g of freshly prepared hot (~ 85C) black coffee solution. The pH of the coffee

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drinks was determined after they were cooled to room temperature.

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2.4 Characterization of creamer emulsions and coffee solutions 2.4.1 Photography and color measurements

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The appearance of the model oil-in-water emulsions and coffee solutions was documented using a digital camera. The color of the model emulsions and white coffee drinks was also

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determined and represented as the tristimulus color coordinates, L*, a*, b*. The lightness (L*, 0 for black to 100 for white), red to green coordinates (a*, positive for red and negative for green),

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and yellow to blue coordinates (b*, positive for yellow and negative for blue) of the samples were determined using HunterLab colorimeter (ColorFlez EZ, HunterLab, Reston, VA, USA). Samples

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(10 mL) were loaded into a measuring cup and a black background was used for all readings. 2.4.2 Particle size distribution

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The particle size profile of the creamer emulsions and coffee solutions was characterized using a laser diffraction particle size analyzer (Beckman Coulter LS 12 320, Brea, CA, USA). Aliquots (0.5 to 1.0 mL) of sample was added into the measurement cell that contained either 0.4% potassium phosphate solution (pH 7.0) for the creamer emulsions or distilled water containing 270 ppm CaCO3 hardness at the corresponding pH of the white coffees until optimum obscuration rate of 40 to 55% was produced. For all measurements, a refractive index of 1.333 was used for the aqueous phase and 1.448 for the oil (MCT) phase. The results of the particle size measurements

ACCEPTED MANUSCRIPT are reported as surface-weighted mean diameters (d3,2) and were based on an analysis of the measured angular light scattering pattern using Mie theory. 2.4.3 Microstructure analysis Confocal laser scanning microscopy was used to record the microstructure of the model creamer emulsions and coffee solutions. A bright field microscope fitted with a 10x eyepiece and

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a 60x objective lens was used (Nikon D-Eclipse C1 80i, Nikon, Melville, NY, USA). All samples

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were stained with Nile red solution (1 mg Nile red in 1 mL of ethyl alcohol) for the oil (stained

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red) and fluorescein isothiocyanate isomer 1 (FITC, 1 mg FITC in 1 mL dimethyl sulfoxide) for the protein (stained green). 1 mL of sample was mixed with each fluorescent dye (0.2 mL) and a small drop (0.1 mL) of the dyed sample was loaded on a glass slide and covered with a cover slip.

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The excitation and emission spectrum for the Nile red were 543 nm and 605 nm, respectively and for the FITC were 488 nm and 515 nm, respectively. All images were taken using an image

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analysis software (EZ-CS1, Nikon, Melville, NY, USA).

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2.4.4 Electrical charge measurement

The electrical potential (zeta potential) of the particles in the model O/W emulsions and in the

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coffee solutions was determined with a particle electrophoresis instrument (Zetasizer Nano ZA series, Malvern Instruments Ltd., Worcestershire, UK). Samples were diluted 20- to 40-fold using

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0.4% potassium phosphate buffer or boiled water containing 270 ppm CaCO3 hardness (at the same pH as the samples) to obtain attenuation values around 6 to 11 to reduce particle interaction

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during measurements.

2.5 Statistical analysis

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All model O/W emulsions and coffee systems were prepared in replicates and triplicate measurements were made for each replicate (n = 6). The average and standard deviation were calculated from all six readings.

ACCEPTED MANUSCRIPT 3. Results and discussion 3.1 Effect of emulsifier type and level In the first part of the study, we investigated the effect of emulsifier type and level on the physical properties of model O/W emulsions to determine the feasibility of reducing and/or replacing the use of dairy-based proteins by a plant-based emulsifier.

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3.1.1 Appearance and color

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The appearance and color of creamers are important factors that influence their consumer

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acceptance when added to coffee or tea. Oil-in-water emulsions of creamers are responsible for these properties of the creamers. Figure 1a shows the visual appearance of the model O/W

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emulsions stabilized by either sodium caseinate (0.25 to 1.5%) or soy lecithin (0.5 to 1.5%). All model O/W emulsions had a whitish color that was similar to that previously reported for milk and

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commercial creamers made with sodium caseinate (Chung et al., 2017b). The addition of model O/W emulsions to hot, acidic black coffee (1%) produced white coffees with similar appearances as those obtained using commercial creamers. However, the white coffee solutions prepared with

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the model O/W emulsions containing the lowest emulsifier levels (0.25% caseinate or 0.5%

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lecithin) had an oil layer and some “feathering” on their surfaces (Figure 1a). This destabilization was attributed to coalescence of oil droplets and oiling off resulting from the fact that there was

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insufficient emulsifier in the O/W emulsions to form a complete interfacial layer around the oil droplet. Oiling-off and feathering in coffee drinks are unappealing product flaws that should be

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avoided (Burgwald, 1923; Golde & Schmidt, 2005). This result highlights the importance of adding sufficient emulsifier within the initial system to form a complete and robust interfacial layer

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around the oil droplets.

The tristimulus color coordinates of the model O/W emulsions and white coffees were also obtained. Lightness is one of the chief factors determining the acceptance of these products (Jeske et al., 2017). All model O/W emulsions stabilized with sodium caseinate had lightness values around 87 to 88, while those stabilized with soy lecithin had lightness values that increased from around 81 to 87 with increasing emulsifier level (Table 1a). The lightness values measured in these model O/W emulsions were lower than the whiteness index of commercial creamers made with sodium caseinate (L*: 91 to 93) and lower or similar to creamers made with plant ingredients (L*: 51 to 81) (Chung et al., 2017b; Jeske et al., 2017). The increase in lightness with increasing

ACCEPTED MANUSCRIPT lecithin content was due to a decrease of oil droplet size (section 3.1.2), as previous studies have found that droplets in the size range from around 100 to 200 nm scatter light waves most efficiently (McClements, 2002; Zhang & Reineccius, 2016). Both types of O/W emulsions had green (-a* values), which increased with increasing emulsifier content. The O/W emulsion stabilized by sodium caseinate had blue tint (-b* values) while those stabilized by soy lecithin had yellow tint due to the inherent color of lecithin (Table 1a). The lightening power of the model emulsions in

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coffee was also determined. As expected, addition of the creamer emulsions stabilized with sodium

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caseinate lightened the black coffees, with the L* values increasing from around of 4.3 for black

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coffee to around 48 for the whitest coffee (Table 1a). The soy lecithin-stabilized oil-in-water emulsions could also lighten black coffee but with lesser lightening power than sodium caseinate

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at the same emulsifier concentration, which is mainly attributed to the different particle sizes of the oil droplets (see next section). All white coffees had a red and yellow tint (+a* and +b* values)

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mainly due to the inherent brownish hue of the coffee solutions themselves. 3.1.2 Particle size profile and microstructure

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The average particle diameter (d3,2) and particle size distributions of the model O/W emulsions were also measured. The mean diameter of the droplets in the model emulsion decreased from

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around 0.56 m to 0.22 m as more caseinate was added and from around 2 m to 0.56 m as more lecithin was added (Table 1b). These results show that caseinate was a more effective

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emulsifier than soy lecithin when used at the same level, which could be due to differences in the adsorption and packing of the protein and lecithin emulsifiers at the oil-water interfaces (Chung et

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al., 2017a; Fang & Dalgleish, 1996; Wilde, Mackie, Husband, Gunning, & Morris, 2004). Indeed, previous studies have reported that caseinate has a lower surface load than lecithin and so requires

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a smaller amount of emulsifier to cover the same surface area (McClements, Bai, & Chung, 2017). All model O/W emulsions had bimodal particle size distributions, except the one stabilized by 0.5% caseinate (Figure 1b). The monomodal peak observed at this caseinate level suggests that an optimum concentration of emulsifier was reached to produce small oil droplets of uniform size. Addition of more caseinate simply led to the formation of casein micelles in the aqueous phase, which contributed to the light scattering pattern (Dickinson, 2010; Dickinson, Golding, & Povey, 1997). The model O/W emulsions stabilized with lecithin always had bimodal particle size distributions, however increasing the lecithin level produced smaller oil droplets with the larger peak almost disappearing in the model creamer containing 1.5% lecithin (Figure 1b). It is possible

ACCEPTED MANUSCRIPT that there were also some phospholipid vesicles present in these emulsions but these could not be seen in the microscopy images. Moreover, the lecithin concentration used in this study was fairly low (1.5%), while another study reported no evidence of phospholipid vesicle formation even at higher levels (5%) (Chung et al., 2017a). Similar mean particle diameters (Table 1b) and particle size distributions (data not shown) were also measured in the corresponding white coffee solutions, indicating that the oil droplets were stable after being incorporated into the hot acidic coffee,

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despite the feathering observed in the 0.25% caseinate- and 0.5% lecithin-stabilized model

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emulsions.

The confocal micrographs of the systems also showed that small oil droplets (stained in red) were present in all model O/W emulsions and coffee solutions, as well as a decrease in oil droplet

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size with increasing emulsifier level (Figure 1c). The oil droplets remained stable after being added to the coffee solution, with no evidence of extensive flocculation or coalescence. This

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suggests that they were relatively stable to aggregation in a hot, acidic environment, such as that

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found in coffee. 3.1.3 Zeta potential

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The electrical characteristics (zeta-potential) of the model creamers were also measured. The caseinate-stabilized O/W emulsions had surface potentials ranging from around -28 mV to -33 mV

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while the lecithin-stabilized ones had values ranging from about -38 mV to -35 mV (Table 1b). The high zeta potential of the droplets in all model emulsions causes strong electrostatic repulsions

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between oil droplets and may account for their good stability to aggregation, as evidenced from the particle size measurement and microstructure images. After adding the model O/W emulsions

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to black coffee solutions, the overall zeta potential of the oil droplets was reduced to around -19 to -21 mV, while the black coffee itself had a zeta potential around -7.3 mV (Table 1b). The reduction in the zeta potential observed for the oil droplets after being incorporated into the black coffee could be due to several effects: (a) the pH of the overall solutions was lower (pH 5.6 – 5.7) than that of the model O/W emulsions (pH 7) (Table 1b) and this may have decreased the negative charge on the droplets; (b) the positively charged calcium and magnesium ions in the hard water may have partially shielded the negative charges on the oil droplets through ion adsorption; and (c) the phenolic, fatty acids, caffeine and organic compound in the coffee (Clemente, Martinez, Pedrosa, Neves, Cecon, & Jifon, 2018; Hendon, Colonna-Dashwood, & Colonna-Dashwood,

ACCEPTED MANUSCRIPT 2014; Kitzberger, Scholz, Pereira, & Benassi, 2013; Oliveira-Neto, Rezende, de Fátima Reis, Benjamin, Rocha, & de Souza Gil, 2016; Tran, Vargas, Lee, Furtado, Smyth, & Henry, 2017) may have contributed to the electrical charge of the coffee solutions.

3.2 Effect of emulsifier mixture and content In the final part of the study, we investigated the effect of using mixtures of caseinate and

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lecithin emulsifiers to compare with performance of O/W emulsions stabilized by sodium

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caseinate or soy lecithin emulsifiers alone.

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3.2.1 Appearance and color

Figure 2a shows the appearance of the model O/W emulsions stabilized with different

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mixtures of emulsifiers. It is apparent from the photos that as the lecithin content increased, the model O/W emulsions gained an increasingly intense yellow tint. This was because soy lecithin

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itself has a strong yellow color. All model emulsions were stable and had similar appearances to commercial creamers. Selected emulsions were added to black coffee solutions (1%) and they were

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able to whiten the black coffee without any destabilization being observed (Figure 2a). The measured tristimulus color coordinates showed that the lightness (L*) of the O/W

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emulsions decreased with increasing caseinate and lecithin content (Figure 2b), which could be due to a decrease in droplet size that led to less light scattering (section 3.2.2). The green tint (-a*

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values) and yellow tint (+b* values) of the model emulsions increased with increasing lecithin content, which was also observed when lecithin alone was used as the emulsifier, was due to the

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inherent color of the lecithin powder. The model O/W emulsions stabilized by mixed emulsifiers produced slightly whiter coffees (L*  50) than those stabilized by sodium caseinate alone (L* 

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48) (Figure 2c and Table 1a). Overall, these results suggest that the level of caseinate required to produce a given appearance in the model emulsions and coffees could be reduced by incorporating some lecithin.

3.2.2 Particle size profile and microstructure The particle size measurements showed that the mixed emulsifiers produced model O/W emulsions containing smaller droplets than those containing 0.25% caseinate alone, and similar to those with higher level of sodium caseinate (Figure 3a). Other studies (Xue & Zhong, 2014; Yesiltas et al., 2019) have also demonstrated a reduced particle size when a combination of

ACCEPTED MANUSCRIPT caseinate and lecithin was used to stabilize oil-in-water emulsions. Similar results were also found in white coffee (Figure 3a). The particle size distributions showed that addition of lecithin to caseinate changed the distribution profile (Figure 3b). Almost all model O/W emulsions had bimodal or skewed distributions except for those stabilized with 0.5% caseinate alone or 0.5% caseinate / 0.5% soy lecithin. At 0.25% sodium caseinate, there was insufficient emulsifier to stabilize the 10% oil in the system hence both small and large droplets were formed. For systems

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containing 0.75% caseinate and above, there could be excess emulsifier in the systems and casein

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aggregates may be formed, which resulted in the small shoulder shown in particle size

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distributions. Slightly larger droplets were measured in all the systems containing caseinate and 0.5% lecithin when added to black coffee solutions (Table 1b). This increase in particle size could

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be due to some droplet aggregation and emulsifier displacement at the droplet surfaces. Despite the slightly larger mean particle diameters, there were no pronounced changes in the particle size

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distributions (compare Figure 3b and Figure 3c).

The microstructure of selected model O/W emulsions showed that small oil droplets (stained

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in red) were produced and they looked similar to the corresponding systems containing caseinate alone (stained in green) (Figure 4). After addition to hot acidic black coffee, the oil droplets were

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still homogenously dispersed, without any obvious changes in their particle size.

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3.2.3 Zeta potential

The model creamer emulsions stabilized with mixed emulsifiers had zeta potentials ranging

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from around -30 mV to -33 mV (Figure 5). Overall, the zeta potential values had fairly large standard deviations, which may be due to the presence of two types of colloidal particles with

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different charges in the system, such as oil droplets and unabsorbed emulsifiers (Figure 5). Nonetheless, all model O/W emulsions had relatively high zeta-potentials (around -30 mV), which should lead to a strong electrostatic repulsion between the droplets and help to reduce droplet association. The white coffee solutions containing model emulsions stabilized with mixed emulsifiers had zeta potentials around -17 mV to -19 mV (Figure 5). These values were slightly less negative than those measured in the corresponding creamer systems stabilized by caseinate alone (-19 to -20 mV), which indicates that the mixed emulsifier model emulsions had different compositions and/or arrangements of emulsifiers at the interfacial layer. Despite the lower

ACCEPTED MANUSCRIPT electrical potential measured in the white coffee systems containing model O/W emulsions, no destabilization (feathering, creaming or sedimentation) was observed.

Conclusions The present study examined the potential of using a plant-based emulsifier, soy lecithin, to

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fully or partially replace sodium caseinate in O/W model emulsions. All model O/W emulsions

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stabilized by either caseinate (0.25 to 1.5%) or lecithin (0.5 to 1.5%) had similar whitish appearances. The model emulsions stabilized by sufficiently high emulsifier levels (0.5% to 1.5%

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caseinate or 1% and 1.5% lecithin) had the ability to whiten black coffee with no feathering or oiling off occurring. However, these forms of emulsion instability were observed when model o/w

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emulsions containing lower emulsifier levels were added to black coffee. This effect was due to insufficient emulsifier concentration to form a complete interfacial layer around the oil droplets.

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Blends of caseinate and lecithin were able to produce model O/W emulsions with similar appearances, colors, particle sizes, and electrical properties as those stabilized by the individual

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emulsifiers. The mixed emulsifier model emulsions were also able to whiten black coffee with slightly higher whitening power than those stabilized with caseinate alone. Overall, our results

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demonstrate that soy lecithin can be used to fully or partially replace sodium caseinate in model O/W emulsions. Further work is required to establish the impact of processing and storage

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conditions that the O/W emulsions may experience throughout their lifetimes.

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Reference

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Abdullah, A., Malundo, T. M. M., Resurreccion, A. V. A., & Beuchat, L. R. (1993). DESCRIPTIVE SENSORY PROFILING FOR OPTIMIZING THE FORMULA OF A PEANUT MILK-BASED LIQUID COFFEE WHITENER. Journal of Food Science, 58(1), 120-123. doi: 10.1111/j.1365-2621.1993.tb03224.x Burgwald, L. (1923). Some factors which influence the feathering of cream in coffee. Jour. Agr. Res, 26(11). Chung, C., Sher, A., Rousset, P., Decker, E. A., & McClements, D. J. (2017a). Formulation of food emulsions using natural emulsifiers: Utilization of quillaja saponin and soy lecithin to fabricate liquid coffee whiteners. Journal of Food Engineering, 209, 1-11. doi: 10.1016/j.jfoodeng.2017.04.011 Chung, C., Sher, A., Rousset, P., & McClements, D. J. (2017b). Use of natural emulsifiers in model coffee creamers: Physical properties of quillaja saponin-stabilized emulsions. Food Hydrocolloids, 67, 111-119. doi: 10.1016/j.foodhyd.2017.01.008 Clemente, J. M., Martinez, H. E. P., Pedrosa, A. W., Neves, Y. P., Cecon, P. R., & Jifon, J. L. (2018). Boron, Copper, and Zinc Affect the Productivity, Cup Quality, and Chemical Compounds in Coffee Beans. [Article]. Journal of Food Quality, 14. doi: 10.1155/2018/7960231 Cliceri, D., Spinelli, S., Dinnella, C., Prescott, J., & Monteleone, E. (2018). The influence of psychological traits, beliefs and taste responsiveness on implicit attitudes toward plant- and animal-based dishes among vegetarians, flexitarians and omnivores. [Article]. Food Quality and Preference, 68, 276-291. doi: 10.1016/j.foodqual.2018.03.020 de Boer, J., de Witt, A., & Aiking, H. (2016). Help the climate, change your diet: A cross-sectional study on how to involve consumers in a transition to a low-carbon society. Appetite, 98, 19-27. doi: 10.1016/j.appet.2015.12.001 Dickinson, E. (2010). Flocculation of protein-stabilized oil-in-water emulsions. Colloids and Surfaces B-Biointerfaces, 81(1), 130-140. doi: 10.1016/j.colsurfb.2010.06.033 Dickinson, E., Golding, M., & Povey, M. J. W. (1997). Creaming and flocculation of oil-in-water emulsions containing sodium caseinate. Journal of Colloid and Interface Science, 185(2), 515-529. doi: 10.1006/jcis.1996.4605 Fang, Y., & Dalgleish, D. G. (1996). Competitive adsorption between dioleoylphosphatidylcholine and sodium caseinate on oil-water interfaces. Journal of Agricultural and Food Chemistry, 44(1), 59-64. doi: 10.1021/jf950330g Golde, A., & Schmidt, K. (2005). Quality of coffee creamers as a function of protein source. Journal of food quality, 28(1), 46-61. Hedenus, F., Wirsenius, S., & Johansson, D. J. A. (2014). The importance of reduced meat and dairy consumption for meeting stringent climate change targets. [journal article]. Climatic Change, 124(1), 79-91. doi: 10.1007/s10584-014-1104-5 Hendon, C. H., Colonna-Dashwood, L., & Colonna-Dashwood, M. (2014). The role of dissolved cations in coffee extraction. Journal of agricultural and food chemistry, 62(21), 49474950. Jeske, S., Zannini, E., & Arendt, E. K. (2017). Evaluation of Physicochemical and Glycaemic Properties of Commercial Plant-Based Milk Substitutes. [journal article]. Plant Foods for Human Nutrition, 72(1), 26-33. doi: 10.1007/s11130-016-0583-0

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Kitzberger, C. S. G., Scholz, M. B. d. S., Pereira, L. F. P., & Benassi, M. d. T. (2013). Chemical composition of traditional and modern Arabica coffee cultivars. Pesquisa Agropecuária Brasileira, 48(11), 1498-1506. Makinen, O. E., Wanhalinna, V., Zannini, E., & Arendt, E. K. (2016). Foods for Special Dietary Needs: Non-dairy Plant-based Milk Substitutes and Fermented Dairy-type Products. [Review]. Critical Reviews in Food Science and Nutrition, 56(3), 339-349. doi: 10.1080/10408398.2012.761950 McClements, D. J. (2002). Theoretical prediction of emulsion color. Advances in Colloid and Interface Science, 97(1), 63-89. McClements, D. J., Bai, L., & Chung, C. (2017). Recent Advances in the Utilization of Natural Emulsifiers to Form and Stabilize Emulsions. In M. P. Doyle & T. R. Klaenhammer (Eds.), Annual Review of Food Science and Technology, Vol 8 (Vol. 8, pp. 205-236). Oliveira-Neto, J. R., Rezende, S. G., de Fátima Reis, C., Benjamin, S. R., Rocha, M. L., & de Souza Gil, E. (2016). Electrochemical behavior and determination of major phenolic antioxidants in selected coffee samples. Food chemistry, 190, 506-512. Rosida, D. F., Mulyani, T., & Septalia, L. R. (2016). A Comparative Study of Non-Dairy Cream Based on the Type of Leguminosae Protein Source in Terms of Physico Chemical Properties and Organoleptic. Agriculture and Agricultural Science Procedia, 9, 431-439. Sethi, S., Tyagi, S. K., & Anurag, R. K. (2016). Plant-based milk alternatives an emerging segment of functional beverages: a review. [Article]. Journal of Food Science and TechnologyMysore, 53(9), 3408-3423. doi: 10.1007/s13197-016-2328-3 Stubbs, R. J., Scott, S. E., & Duarte, C. (2018). Responding to food, environment and health challenges by changing meat consumption behaviours in consumers. [Editorial Material]. Nutrition Bulletin, 43(2), 125-134. doi: 10.1111/nbu.12318 Tran, H. T. M., Vargas, C. A. C., Lee, L. S., Furtado, A., Smyth, H., & Henry, R. (2017). Variation in bean morphology and biochemical composition measured in different genetic groups of arabica coffee (Coffea arabica L.). [Article]. Tree Genetics & Genomes, 13(3), 14. doi: 10.1007/s11295-017-1138-8 Wilde, P., Mackie, A., Husband, F., Gunning, P., & Morris, V. (2004). Proteins and emulsifiers at liquid interfaces. [Article; Proceedings Paper]. Advances in Colloid and Interface Science, 108, 63-71. doi: 10.1016/j.cis.2003.10.011 Xue, J., & Zhong, Q. X. (2014). Thyme Oil Nanoemulsions Coemulsified by Sodium Caseinate and Lecithin. [Article]. Journal of Agricultural and Food Chemistry, 62(40), 9900-9907. doi: 10.1021/jf5034366 Yesiltas, B., Garcia-Moreno, P. J., Sorensen, A. D. M., Akoh, C. C., & Jacobsen, C. (2019). Physical and oxidative stability of high fat fish oil-in-water emulsions stabilized with sodium caseinate and phosphatidylcholine as emulsifiers. [Article]. Food Chemistry, 276, 110-118. doi: 10.1016/j.foodchem.2018.09.172 Zhang, J., & Reineccius, G. A. (2016). Factors controlling the turbidity of submicron emulsions stabilized by food biopolymers and natural surfactant. LWT-Food Science and Technology, 71, 162-168.

ACCEPTED MANUSCRIPT Table 1a: Effect of emulsifier type and concentration (sodium caseinate: 0.25 to 1.5%) and soy lecithin: 0.5 to 1.5%) on the tristimulus color coordinate of the model O/W emulsions and white coffee solutions.

White

O/W

emulsion

Coffee

emulsion

-

4.26

-

46.19

 0.46

 0.33

CE

Sodium caseinate

AC

1.00

1.25

1.50

Coffee

3.88

-

4.93

 0.34

 0.33 -1.21

29.87

 0.04

 0.08

 0.09

 0.15

48.4

-1.08

9.44

-1.66

28.01

 0.58

 0.30

 0.07

 0.13

 0.07

 0.66

88.32

48.20

-1.24

8.95

-1.78

26.71

 0.46

 0.07

 0.03

 0.04

 0.05

 0.25

88.18

48.32

-1.42

8.52

-2.19

25.60

 0.30

 0.27

 0.06

 0.16

 0.02

 0.76

87.86

48.16

-1.6

8.34

-2.41

25.34

 0.20

 0.21

 0.06

 0.07

 0.06

 0.21

87.63

48.23

-1.75

8.12

-2.51

24.59

 0.15

 0.21

 0.04

 0.13

 0.05

 0.66

PT

0.75

emulsion

10.55

88.41

0.50

Coffee

-0.80

AN

88.05

M

0.25

White

ED

 0.28

-

O/W

White

CR

Black Coffee

O/W

b*

T

Content (%)

a*

IP

L*

Emulsifier

US

Emulsifier Type

1.00

32.16

-1.19

13.78

1.65

32.70

 0.06

 1.16

 0.03

 0.01

 0.01

 0.89

86.53

42.72

-1.66

11.46

3.93

31.99

 0.08

 0.54

 0.02

 0.03

 0.01

 0.40

87.55

46.81

-1.88

5.90

30.32

 0.58

 0.52

 0.-3

 0.10

 0.02

 0.21

10.32

CE

PT

ED

M

AN

US

CR

1.50

81.57

IP

0.50

AC

Soy Lecithin

T

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT Table 1b: Effect of emulsifier type and concentration (sodium caseinate: 0.25 to 1.5%) and soy lecithin: 0.5 to 1.5%) on the averaged particle size diameter and zeta potential of the model O/W emulsions and white coffee solutions.

pH

Emulsifier

Size, d3,2 (m)

Content (%) emulsion

Coffee

emulsion

-

4.80  0.01

7.0

5.59

ED

CE

Sodium caseinate

7.0

PT

0.75

7.0

1.25

7.0

AC

1.00

1.50

7.0

Coffee

emulsion

Coffee

-

-

-7.30  0.34

-28.15

-19.68

 0.01

 0.00

 2.25

 0.44

5.65

0.36

0.37

-34.25

-20.27

 0.01

 0.02

 0.00

 1.90

 0.89

5.70

0.26

0.26

-34.53

-19.32

 0.01

 0.06

 0.02

 2.49

 0.56

5.74

0.26

0.26

-34.40

-19.03

 0.01

 0.01

 0.02

 2.66

 0.48

5.77

0.23

0.22

-33.43

-18.65

 0.01

 0.01

 0.00

 1.84

 0.64

5.81

0.22

0.22

-33.37

-18.68

 0.01

 0.01

 0.00

 2.15

 0.72

M

7.0

White

0.57

 0.01

0.50

O/W

0.56

AN

0.25

-

White

IP

O/W

CR

-

White

US

Black Coffee

O/W

Zeta Potential (mV)

T

Emulsifier Type

7.0

1.00

7.0

2.00

1.73

-38.49

-20.85

 0.01

 0.14

 0.13

 0.74

 0.40

5.56

0.83

0.83

-32.25

-21.18

 0.01

 0.03

 0.00

 0.89

 0.79

5.57

0.56

-34.80

-21.65

 0.01

 0.01

 0.00

 1.22

 0.40

0.58

CE

PT

ED

M

AN

US

CR

1.50

5.53

IP

7.0

0.50

AC

Soy Lecithin

T

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT

AC

CE

PT

ED

M

AN

US

CR

IP

T

Figure 1: Effect of emulsifier type and concentration (sodium caseinate: 0.25 to 1.5% and soy lecithin: 0.5 to 1.5%) on the appearance (a) , particle size distribution (b) and microstructure (c) of the model O/W emulsions and white coffee. Scale bar on bottom right of confocal images (60 x magnification) represents 20 m. Oil droplets were stained with Nile Red (0.1%) in red color and protein was stained with fluorescein isothiocyanate isomer I (0.1%) in green color. Figure 2: Effect of emulsifier mixture content (sodium caseinate: 0.25 to 1.5% with soy lecithin: 0.5 to 1.5%) on the appearance (a) and tristimulus color coordinate (b and c) of the model creamers and white coffee. Figure 3: Effect of emulsifier mixture content (sodium caseinate: 0.25 to 1.5% with soy lecithin: 0.5 to 1.5%) on the particle size diameter (a) and particle size distribution (b and c) of the model O/W emulsions and white coffee. Figure 4: Effect of emulsifier mixture content (sodium caseinate: 0.25 to 1.5% with soy lecithin: 0.5 to 1.5%) on the microstructure of the model O/W emulsions and white coffee. Scale bar on bottom right of confocal images (60 x magnification) represents 20 m. Oil droplets were stained with Nile Red (0.1%) in red color and protein was stained with fluorescein isothiocyanate isomer I (0.1%) in green color. Figure 5: Effect of emulsifier mixture content (sodium caseinate: 0.25 to 1.5% with soy lecithin: 0.5 to 1.5%) on the electrical potential of the model O/W emulsions and white coffee.

ACCEPTED MANUSCRIPT Highlights “Modulation of Caseinate-stabilized Model Oil-in-Water Emulsions with Soy Lecithin” by Chung et al. Food Research International

Demands for plant-based milk and creamer products have escalated recently.



Model creamers were fabricated using soy lecithin and/or sodium caseinate



These creamers had similar physical properties to conventional dairy-based creamers.



The creamers were stable to aggregation and feathering after added to hot, acidic coffee.

AC

CE

PT

ED

M

AN

US

CR

IP

T

