Progress in natural emulsifiers for utilization in food emulsions

Progress in natural emulsifiers for utilization in food emulsions

Accepted Manuscript Title: Progress in natural emulsifiers for utilization in food emulsions Author: Bengu Ozturk David Julian McClements PII: DOI: Re...

571KB Sizes 3 Downloads 209 Views

Accepted Manuscript Title: Progress in natural emulsifiers for utilization in food emulsions Author: Bengu Ozturk David Julian McClements PII: DOI: Reference:

S2214-7993(15)00100-9 http://dx.doi.org/doi:10.1016/j.cofs.2015.07.008 COFS 81

To appear in: Received date: Accepted date:

8-7-2015 24-7-2015

Please cite this article as: Ozturk, B., McClements, D.J.,Progress in natural emulsifiers for utilization in food emulsions, COFS (2015), http://dx.doi.org/10.1016/j.cofs.2015.07.008 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

“Progress in natural emulsifiers for utilization in food emulsions”

cr

Bengu Ozturk and David Julian McClements

ip t

Highlights

us

Current Opinion in Food Science.



an

The food industry requires natural emulsifiers for more consumer friendly labels



M

Proteins, polysaccharides, phospholipids, and

saponins can be used as natural emulsifiers 

d

Each emulsifier has particular advantages and

This article reviews recent progress in the

development and testing of natural emulsifiers

Ac ce p



te

disadvantages for particular applications

1 Page 1 of 26

Progress in natural emulsifiers for utilization in food emulsions Bengu Ozturka and David Julian McClementsb,c* Food Institute, TÜBİTAK Marmara Research Center, P.O. Box 21, 41470 Gebze-Kocaeli,

ip t

a

b

cr

Turkey

Department of Food Science, University of Massachusetts, Chenoweth Laboratory, Amherst,

Production of Bioproducts for Industrial Applications Research Group, Department of

an

c

us

MA, USA

Biochemistry, Faculty of Science, King Abdulaziz University, P. O. Box 80203 Jeddah 21589

Ac ce p

te

d

M

Saudi Arabia

*Corresponding Author

Address: Department of Food Science, University of Massachusetts, Chenoweth Laboratory, Amherst, MA, 01003 USA

Tel: 413 545 1019; Fax: 413 545 1262; E-mail: [email protected]

2 Page 2 of 26

ip t

Abstract

There is growing demand in the food industry for natural ingredients to fabricate “clean

cr

label” products. This article provides a review of recent studies on the identification,

us

characterization, and utilization of natural food-grade emulsifiers, such as proteins, polysaccharides, phospholipids, and saponins.

Particular emphasis is given to relating the

an

structural properties of these emulsifiers to their ability to form and stabilize emulsions. The influence of environmental stresses, such as pH, ionic strength, and temperature, on the

M

performance of natural emulsifiers is discussed. This information should facilitate the rational

te

pharmaceutical products.

d

selection of natural emulsifiers for applications in emulsion-based food, beverage, cosmetic, and

Ac ce p

Keywords: natural emulsifier; stability; phospholipids; polysaccharide; protein; saponins.

3 Page 3 of 26

Introduction One of the most critical aspects in the formation of successful emulsion-based products is the selection of an appropriate emulsifier [1].

Emulsifiers are surface-active substances that

ip t

play two key roles in the creation of emulsions: (i) they facilitate emulsion formation; (ii) they

cr

promote emulsion stability. In general, there are many numerous kinds of synthetic and natural emulsifiers that can be utilized in the food industry, including proteins, polysaccharides,

us

phospholipids, and surfactants [2]. Nevertheless, consumers are increasingly demanding “clean”

an

labels on food and beverage products, and so the food industry is trying to replace many synthetic surfactants with natural alternatives, or to formulate new products entirely from natural

M

ingredients.

This article highlights recent research on the identification, characterization and utilization

d

of natural emulsifiers suitable for application in the food industry, and highlights the structural

te

for their functional performance. This information should aid in the identification of new types

Ac ce p

of natural emulsifiers for use in foods and beverages.

Overview of natural food-grade emulsifiers Proteins

Many proteins are surface active because they contain a mixture of hydrophilic and hydrophobic amino acids along their polypeptide chains [3]. Consequently, they can adsorb to oil-water interfaces and coat the oil droplets formed during homogenization. They may also stabilize droplets from aggregation because they contain amino acids that possess negative (– COO-) or positive (-NH3+) charges, and can therefore generate an electrostatic repulsion [4, 5]. In addition, they may inhibit aggregation through steric repulsion by forming thick interfacial layers 4 Page 4 of 26

or by having carbohydrate moieties attached [6].

There has been considerable interest in

identifying and characterizing glycoproteins that naturally have these carbohydrate moieties [7],

ip t

or in attaching carbohydrate moieties to proteins e.g., by the Maillard reaction [8, 9]. Currently, the most commonly used natural protein-based emulsifiers in the food industry Caseins are a group of

cr

are derived from bovine milk: caseins and whey proteins [10].

amphiphilic proteins with flexible structures (ɑs1, ɑs2, β, and κ -caseins), whereas whey proteins

us

are a group of globular proteins with fairly rigid structures (ɑ-lactalbumin, β-lactoglobulin, BSA,

an

and immunoglobulins). Gelatins extracted from cow, pig, or fish also have flexible structures and exhibit surface activity, but they are typically not good at stabilizing emulsions [11]. One of

M

the most interesting areas of current research is the identification of protein-based emulsifiers from plant sources [3]. This research is largely driven by the desire to replace animal proteins in

d

vegetarian or vegan products, as well as to improve food sustainability and security [12].

te

Numerous plant-based proteins have been shown to be promising emulsifiers, including pea

Ac ce p

proteins [13], lupin proteins [14], soy proteins [15], and corn germ proteins [16]. The major challenges in this area are (i) identification of economically viable protein sources; (ii) establishment of effective methods for protein isolation, fractionation and purification; (iii) characterization of emulsifier functionality in terms of emulsion formation and stability. Polysaccharides

Most polysaccharides are highly hydrophilic molecules that are not particularly surfaceactive, and are therefore not good emulsifiers [17]. Instead, they tend to stabilize emulsions by increasing aqueous phase viscosity and thereby inhibiting droplet movement [1]. These types of polysaccharides can often be made surface-active by chemically or enzymatically attaching nonpolar groups or protein molecules to their hydrophilic backbones, but then the resulting 5 Page 5 of 26

emulsifier would not be considered natural. The main examples of this kind of molecule are modified starches [18] and Maillard complexes of proteins and carbohydrates [19].

ip t

Some natural polysaccharides have good emulsifying properties because they already have non-polar groups or proteins attached to their hydrophilic carbohydrate chains [17]. The most

cr

common examples of this type of surface-active polysaccharide are gum arabic, pectin, and galactomannans. Currently, gum arabic is by far the most widely used natural polysaccharide-

us

based emulsifier in the food industry [20], particularly in beverage emulsions [21]. However, the

required to form stable emulsions [22, 23].

an

major disadvantage of gum arabic is that a relatively high emulsifier-to-oil ratio (≈ 1:1) is Recent studies have shown that citrus pectins can

M

also be used as emulsifiers, with their efficacy at forming and stabilizing emulsions depending on their molecular weight and degree of methoxylation [24]. Other studies have shown that

d

polysaccharides isolated from basil seed were good emulsifiers, with the surface activity being

te

attributed to the presence of protein moieties and non-polar groups on the carbohydrate backbone

Ac ce p

[25]. Corn fiber gum has also been shown to have good emulsifying properties also attributed to the presence of protein moieties [26, 27]. As with proteins, there is need for more research on identifying, isolating, and characterizing the properties of polysaccharide-based emulsifiers from natural sources in an economic manner [28]. Phospholipids

Phospholipids are natural amphiphilic molecules found in the cell membranes of animal, plant, and microbial species [29]. These phospholipids can be isolated, purified, and utilized as surface-active ingredients in the food industry, where they are typically referred to as lecithin [2]. The lecithin used in the food industry is usually extracted from soybeans, egg yolk, milk, sunflower kernels, or rapeseeds [30]. Lecithin ingredients are typically mixtures of different 6 Page 6 of 26

phospholipids,

with

the

most

common

being

phosphatidylcholine

(PC),

phosphatidylethanolamine (PE) and phosphatidylinositol (PI). Phospholipids are surface active

phosphoric acid esterified with glycerol and other substitutes [2, 30].

ip t

because they have hydrophobic fatty acid tail groups and hydrophilic head groups containing

cr

Despite being surface-active, phospholipids are often not good emulsifiers because they form interfacial layers that are prone to coalescence [31]. Nevertheless, certain types of lecithin

us

do appear to be effective at forming and stabilizing emulsions depending on the blend of

an

phospholipids they contain [30]. Lecithin may also be used in combination with other natural emulsifiers to form emulsions, e.g., proteins [32]. Research on the emulsification properties of

M

lecithin is likely to continue as fractions with more well-defined and novel phospholipid blends

te

Saponins

d

are introduced commercially.

Saponins are water-soluble small amphiphilic molecules that can be isolated from various

Ac ce p

natural sources [33]. The surface activity of saponins is due to the fact they contain hydrophilic sugar groups attached to non-polar agylcone groups. Recently, a food-grade ingredient (QNaturale, Ingredion) has become commercially available that consists of saponins isolated from the bark of the Quillaja saponaria tree [34]. These quiillaja saponins have been shown to be particularly effective at forming emulsions with small droplets that are stable to a wide range of environmental stresses [35, 36], and are therefore likely to find increasing use in the food industry.

7 Page 7 of 26

Emulsion Formation Factors affecting emulsion formation

to be effective at forming small droplets during homogenization [1]:

ip t

An effective emulsifier must have a number of physicochemical characteristics if it is going

cr

(i) Surface-activity: Emulsifiers must be capable of adsorbing to oil-water interfaces, which

us

means that they must have an appropriate ratio of polar and non-polar groups on their

an

surfaces.

(ii) Adsorption kinetics: Emulsifiers must rapidly adsorb to droplet surfaces during

M

homogenization so they can quickly reduce the interfacial tension and prevent droplet aggregation.

d

(iii)Interfacial tension reduction. Adsorbed emulsifiers should effectively decreasing

te

interfacial tension as this facilities droplet disruption within homogenizers.

Ac ce p

(iv)Stabilization: Adsorbed emulsifiers should protect droplets from aggregating during droplet-droplet encounters by generating strong repulsive interactions, such as steric or electrostatic repulsion.

(v) Surface coverage: The amount of emulsifier required to stabilize an emulsion depends on the surface load, which is the mass of emulsifier per unit surface area at saturation. The higher the surface load, the more emulsifier required to stabilize a given emulsion. Natural emulsifiers vary considerably in the above characteristics, which means that there are large differences in their ability to form emulsions. 8 Page 8 of 26

Comparison of different natural emulsifiers The efficacy of emulsifiers at forming emulsions can be compared by measuring the change in mean droplet diameter (d32) with emulsifier concentration (C) [1]. An emulsifier can then be

emulsifier required (Cmin) to produce small droplets (Figure 1).

ip t

characterized by the minimum size of the droplets produced (dmin) and the minimum amount of Natural emulsifiers have

us

reduce interfacial tensions, and prevent droplet aggregation.

cr

different abilities to form emulsions because of differences in their ability to adsorb to surfaces,

an

Proteins: Proteins are usually relatively small molecules (≈ 10 - 50 kDa) that rapidly adsorb to droplet surfaces and form thin electrically charged interfacial layers [11] (Figure 2). Proteins

M

may adopt various interfacial conformations depending on their molecular structures and interactions [37]. Flexible proteins (such as casein or gelatin) rapidly undergo conformational

d

changes so that the hydrophilic groups protrude into water and the hydrophobic groups protrude

te

into oil. Rigid globular proteins (such as whey, egg, soy, or pea proteins) may partially unfold

Ac ce p

after adsorption and form cohesive viscoelastic layers. Polysaccharides: Polysaccharides are usually relatively large molecules (≈ 100 - 1000 kDa) that adsorb relatively slowly to droplet surfaces and form thick hydrophilic interfacial layers [11] (Figure 2). The large size of polysaccharide molecules means that they also tend to have higher surface loads than proteins, so more emulsifier is required to cover the droplet surfaces [35]. Saponins:

Saponins are usually more effective at forming small droplets at low

concentrations than biopolymers [35, 36]. Their relatively low molecular weight (≈ 1.67 kDa) means that they tend rapidly adsorb to droplet surfaces and form thin interfacial layers (Figure 2). In addition, they tend to have higher surface activities than biopolymers because of the

9 Page 9 of 26

higher proportion of non-polar to polar groups, and they are more effective at reducing the interfacial tension because they are able to pack more efficiently at oil-water interfaces. Consequently, saponins typically produce smaller droplets during homogenization than

ip t

biopolymers (Figure 3).

cr

Phospholipids appear to exhibit behavior somewhere between saponins and polysaccharides despite their relatively low molecular weights (≈ 0.760 kDa) (Figure 3). This may be because

us

they tend to form large supramolecular structures, such as bilayers or vesicles, in solution rather

an

than existing as individual molecules.

Factors affecting emulsion stability

M

Emulsion Stability

Emulsions may breakdown due to various destabilization mechanisms

te

intended shelf-life.

d

Once an emulsion has been formed it is important that it remains stable throughout its

Ac ce p

including creaming, flocculation, and coalescence [1]. The nature of the emulsifier surrounding the droplets may impact these instability mechanisms [21].

First, the size of the droplets

produced during homogenization influences the tendency for creaming to occur, with smaller droplets moving more slowly.

Consequently, emulsifiers produce small droplets during

homogenization will give better stability to gravitational separation. Second, the emulsifier layer impacts the relative strength of the attractive and repulsive interactions between the droplets. Emulsifiers that generate strong repulsive interactions tend to be better at inhibiting droplet aggregation. The two major stabilization mechanisms generated by emulsifiers are steric and electrostatic stabilization.

10 Page 10 of 26

Steric stabilization is a short range repulsive interaction that arises when the interfacial layers on two approaching droplets overlap [1].

The strength of this interaction typically

ip t

increases as the thickness and hydrophilicity of the interfacial layers increases [17]. Electrostatic stabilization is a short-to-long range interaction that arises when droplets carry

cr

electrical charges [1]. When the droplets have similar charges there is an electrostatic repulsion

us

between them, whose magnitude and range depend on the surface charge density and the ionic strength of the surrounding solution [31]. The strength of the electrostatic repulsion tends to

an

decrease as the number of charge groups on the surfaces decreases and the ionic strength of the surrounding solution increases.

M

Steric stabilization is often the preferred mechanism because it tends to be less sensitive to

d

environmental conditions (such as pH and ionic strength) than electrostatic stabilization.

te

Commercial oil-in-water emulsions may be exposed to various environmental stresses (such

Ac ce p

as pH, ionic strength, mechanical forces, temperature changes, and enzyme activities) during their manufacture, transport, storage, utilization, and ingestion. It is therefore important that an emulsifier is able to maintain emulsion stability under all the conditions the product may experience throughout its lifetime. Consequently, it is necessary to understand how specific environmental conditions alter the various types of colloidal interactions acting between emulsion droplets stabilized by different kinds of natural emulsifiers.

Comparison of different natural emulsifiers Proteins: Protein-coated lipid droplets are typically stabilized against aggregation through a combination of electrostatic and steric repulsion [4, 38]. Long-range electrostatic interactions 11 Page 11 of 26

are more important for protecting droplets against flocculation, whereas short-range steric interactions are more important for protecting them against coalescence. Some of the major

ip t

factors that may promote aggregation of protein-coated droplets are: pH changes: Protein-coated lipid droplets tend to flocculate when the pH is close to the

cr

protein isoelectric point (Figure 4) because this reduces the magnitude of the charge [38, 39].

us

High ionic strength: High salt levels (particularly multivalent counter-ions) promote flocculation by screening the electrostatic repulsion between charged protein-coated droplets [35,

an

40].

M

Elevated temperatures: Holding an emulsion above the thermal denaturation temperature of adsorbed globular proteins may promote flocculation due to an increased hydrophobic attraction

te

d

when non-polar surface groups are exposed [41-43]. Protease activity: The presence of proteases, such as gastric pepsin, may promote droplet

Ac ce p

aggregation by hydrolyzing adsorbed interfacial protein layers [44, 45]. Polysaccharides: Polysaccharide-coated lipid droplets are mainly stabilized by steric repulsion because they have large hydrophilic groups that protrude into the aqueous phase [17]. Consequently, polysaccharide-stabilized emulsions tend to be relatively stable to changes in pH (Figure 4), ionic strength, and temperature [22, 23, 39, 46]. Nevertheless, many polysaccharides have some electrical charge, which may impact their ability to interact with other charged substances, such as transition metals, colloidal particles, or biopolymers.

12 Page 12 of 26

Phospholipids: Lecithin-coated droplets are mainly stabilized against aggregation by electrostatic repulsion due to the electrical charge on the phospholipid head groups [35]. At low ionic strengths, lecithin-coated droplets tend to be stable at neutral pH due to their high negative

ip t

charge, but unstable under acidic conditions due to the reduction in surface charge and electrostatic repulsion (Figure 4) [35, 47]. The addition of high levels of salts may also promote

cr

extensive droplet aggregation in lecithin-stabilized emulsions through electrostatic screening

us

effects [35]. Lecithin-coated droplets tend to be relatively stable to droplet aggregation at high

an

temperatures due to the strong electrostatic repulsion between them [35].

Saponins: Saponin-coated droplets are also mainly stabilized against flocculation due to

M

their electrical charge, which is mainly due to the presence of glucuronic acids (pKa ≈ 3.25) [34, 36]. Consequently, they tend to be highly charged at neutral pH, but progressively lose their

d

charge as the pH is reduced. The importance of electrostatic repulsion is highlighted by the

te

sensitivity of saponin-coated droplets to pH and ionic strength [35, 36]. At low ionic strengths,

Ac ce p

they are stable to droplet aggregation from pH 8 to 3 due to their high charge, but they flocculate at pH 2 due to the loss of charge (Figure 4). At neutral pH, they tend to flocculate at high salt concentrations due to electrostatic screening effects [35]. Saponin-coated droplets tend to be stable to incubation at high temperatures because of the strong electrostatic repulsion between them [35, 36]. Saponins appear to be highly effective at forming small droplets that are stable over a wide range of conditions, and so it would be interesting to identify other commercially viable sources of them.

13 Page 13 of 26

Conclusions There is considerable interest in formulating food products using all-natural ingredients to

ip t

satisfy consumer demand for cleaner labels. A variety of natural emulsifiers can be used by the food industry to stabilize emulsions each with its own advantages and disadvantages in terms of A better understanding of the molecular basis of

cr

emulsion formation and stabilization.

us

emulsifier performance will enable the selection of the most appropriate natural emulsifier for a particular application, as well as facilitating the identification of new natural materials that may

an

prove to be highly effective emulsifiers.

M

Acknowledgements

This material is partly based upon work supported by the United States Department of

d

Agriculture, NRI Grants (2011-03539, 2013-03795, 2011-67021, and 2014-67021). This project

te

was also partly funded by the deanship of scientific research (DSR), King Abdulaziz University,

Ac ce p

Jeddah, under grant numbers (330-130-1435 and 299-130-1435). The authors, therefore, acknowledge with thanks DSR technical and financial support."

References and Recommended Reading **[1] McClements D. Food Emulsions: Principles, Practices, and Techniques. Third Edition ed. Boca Raton, FL: CRC Press; 2015.

- Updated version of a book that covers all aspects of emulsion formation, stability, characterization, and peformance in the food industry, including a review of emulsifier properties.

14 Page 14 of 26

[2] Kralova I, Sjoblom J. Surfactants Used in Food Industry: A Review. Journal of Dispersion Science and Technology. 2009;30:1363-83.

structure-function approach. Food Chemistry. 2013;141:975-84.

ip t

**[3] Lam RSH, Nickerson MT. Food proteins: A review on their emulsifying properties using a

- A nice review of the strucutural basis for the abilty of proteins to act as emulsifiers

cr

[4] McClements DJ. Protein-stabilized emulsions. Current Opinion in Colloid & Interface

us

Science. 2004;9:305-13.

[5] Dickinson E. Flocculation of protein-stabilized oil-in-water emulsions. Colloids and Surfaces

an

B-Biointerfaces. 2010;81:130-40.

[6] Wooster TJ, Augustin MA. beta-Lactoglobulin-dextran Maillard conjugates: Their effect on

M

interfacial thickness and emulsion stability. Journal of Colloid and Interface Science.

d

2006;303:564-72.

te

[7] McCarthy NA, Kelly AL, O'Mahony JA, Fenelon MA. Sensitivity of emulsions stabilised by bovine beta-casein and lactoferrin to heat and CaCl2. Food Hydrocolloids. 2014;35:420-8.

Ac ce p

[8] Cheetangdee N, Fukada K. Emulsifying activity of bovine beta-lactoglobulin conjugated with hexoses through the Maillard reaction. Colloids and Surfaces a-Physicochemical and Engineering Aspects. 2014;450:148-55. [9] Zhang J, Wu N, Lan T, Yang X. Improvement in emulsifying properties of soy protein isolate by conjugation with maltodextrin using high-temperature, short-time dry-heating Maillard reaction. International Journal of Food Science and Technology. 2014;49:460-7. [10] Wilde PJ. Emulsions and nanoemulsions using dairy ingredients. Dairy-Derived Ingredients: Food and Nutraceutical Uses. 2009:539-64.

15 Page 15 of 26

[11] Bouyer E, Mekhloufi G, Rosilio V, Grossiord J-L, Agnely F. Proteins, polysaccharides, and their complexes used as stabilizers for emulsions: Alternatives to synthetic surfactants in the pharmaceutical field? International Journal of Pharmaceutics. 2012;436:359-78.

ip t

[12] Day L. Proteins from land plants - Potential resources for human nutrition and food security. Trends in Food Science & Technology. 2013;32:25-42.

cr

[13] Stone AK, Avarmenko NA, Warkentin TD, Nickerson MT. Functional properties of protein

us

isolates from different pea cultivars. Food Science and Biotechnology. 2015;24:827-33. [14] Benjamin O, Silcock P, Beauchamp J, Buettner A, Everett DW. Emulsifying Properties of

an

Legume Proteins Compared to beta-Lactoglobulin and Tween 20 and the Volatile Release from Oil-in-Water Emulsions. Journal of Food Science. 2014;79:E2014-E22.

M

*[15] Nishinari K, Fang Y, Guo S, Phillips GO. Soy proteins: A review on composition,

d

aggregation and emulsification. Food Hydrocolloids. 2014;39:301-18.

te

- An nice review of the utilization of soy proteins as emulsifiers in the food industry [16] Hojilla-Evangelista MP. Improved Solubility and Emulsification of Wet-Milled Corn Germ

Ac ce p

Protein Recovered by Ultrafiltration-Diafiltration. Journal of the American Oil Chemists Society. 2014;91:1623-31.

[17] Dickinson E. Hydrocolloids at interfaces and the influence on the properties of dispersed systems. Food Hydrocolloids. 2003;17:25-39. *[18] Sweedman MC, Tizzotti MJ, Schaefer C, Gilbert RG. Structure and physicochemical properties of octenyl succinic anhydride modified starches: A review. Carbohydrate Polymers. 2013;92:905-20. - A comprehensive review of the ability of modified starches to form and stabilize oil-in-water emulsions suitable for use in foods

16 Page 16 of 26

*[19] Evans M, Ratcliffe I, Williams PA. Emulsion stabilisation using polysaccharide-protein complexes. Current Opinion in Colloid & Interface Science. 2013;18:272-82. - A short review highlighting the potential of combinations of proteins and polysaccharides to be

ip t

used as emulsifiers

[20] Williams PA, Phillips GO. Gum arabic. Handbook of Hydrocolloids, 2nd Edition.

cr

2009:252-73.

us

*[21] Piorkowski DT, McClements DJ. Beverage emulsions: Recent developments in formulation, production, and applications. Food Hydrocolloids. 2014;42:5-41.

an

- A comprehensive review of the beverage emulsions, with a section on the utilization of food-

M

grade biopolymers

d

*[22] Charoen R, Jangchud A, Jangchud K, Harnsilawat T, Naivikul O, McClements DJ.

te

Influence of Biopolymer Emulsifier Type on Formation and Stability of Rice Bran Oil-in-Water Emulsions: Whey Protein, Gum Arabic, and Modified Starch. Journal of Food Science.

Ac ce p

2011;76:E165-E72.

- A comparison of the ability of different types of emulsifiers to form and stabilize oil-in-water emulsions

*[23] Qian C, Decker EA, Xiao H, McClements DJ. Comparison of Biopolymer Emulsifier Performance in Formation and Stabilization of Orange Oil-in-Water Emulsions. Journal of the American Oil Chemists Society. 2011;88:47-55. - A comparison of the ability of different types of emulsifiers to form and stabilize oil-in-water emulsions

17 Page 17 of 26

[24] Schmidt US, Koch L, Rentschler C, Kurz T, Endress HU, Schuchmann H. Effect of Molecular Weight Reduction, Acetylation and Esterification on the Emulsification Properties of Citrus Pectin. Food Biophysics. 2015;10:217-27.

ip t

[25] Osano JP, Hosseini-Parvar SH, Matia-Merino L, Golding M. Emulsifying properties of a novel polysaccharide extracted from basil seed (Ocimum bacilicum L.): Effect of polysaccharide

cr

and protein content. Food Hydrocolloids. 2014;37:40-8.

us

[26] Yadav MP, Cooke P, Johnston DB, Hicks KB. Importance of Protein-Rich Components in Emulsifying Properties of Corn Fiber Gum. Cereal Chemistry. 2010;87:89-94.

an

[27] Yadav MP, Moreau RA, Hotchkiss AT, Hicks KB. A new corn fiber gum polysaccharide isolation process that preserves functional components. Carbohydrate Polymers. 2012;87:1169-

M

75.

d

[28] Filotheou A, Ritzoulis C, Avgidou M, Kalogianni EP, Pavlou A, Panayiotou C. Novel

te

emulsifiers from olive processing solid waste. Food Hydrocolloids. 2015;48:274-81. [29] Erickson MC. Chemistry and Function of Phospholipids. In: Akoh CC, editor. Food Lipids.

Ac ce p

Boca Raton, FL.: CRC Press; 2008. p. 39-62. *[30] Klang V, Valenta C. Lecithin-based nanoemulsions. Journal of Drug Delivery Science and Technology. 2011;21:55-76.

[31] Israelachvili J. Intermolecular and Surface Forces, Third Edition. Third Edition ed. London, UK: Academic Press; 2011.

[32] Mantovani RA, Cavallieri ALF, Netto FM, Cunha RL. Stability and in vitro digestibility of emulsions containing lecithin and whey proteins. Food & Function. 2013;4:1322-31. [33] Osbourn A, Goss RJM, Field RA. The saponins - polar isoprenoids with important and diverse biological activities. Natural Product Reports. 2011;28:1261-8.

18 Page 18 of 26

[34] Mitra S, Dungan SR. Micellar properties of quillaja saponin .1. Effects of temperature, salt, and pH on solution properties. Journal of Agricultural and Food Chemistry. 1997;45:1587-95. [35] Ozturk B, Argin S, Ozilgen M, McClements DJ. Formation and stabilization of

ip t

nanoemulsion-based vitamin E delivery systems using natural surfactants: Quillaja saponin and lecithin. Journal of Food Engineering. 2014;142:57-63.

cr

[36] Yang Y, Leser ME, Sher AA, McClements DJ. Formation and stability of emulsions using a

us

natural small molecule surfactant: Quillaja saponin (Q-Naturale (R)). Food Hydrocolloids. 2013;30:589-96.

an

[37] Singh H. Aspects of milk-protein-stabilised emulsions. Food Hydrocolloids. 2011;25:193844.

M

[38] Delahaije R, Wierenga PA, van Nieuwenhuijzen NH, Giuseppin MLF, Gruppen H. Protein

d

Concentration and Protein-Exposed Hydrophobicity as Dominant Parameters Determining the

te

Flocculation of Protein-Stabilized Oil-in-Water Emulsions. Langmuir. 2013;29:11567-74. [39] Ozturk B, Argin S, Ozilgen M, McClements DJ. Formation and stabilization of

Ac ce p

nanoemulsion-based vitamin E delivery systems using natural biopolymers: Whey protein isolate and gum arabic. Food chemistry. 2015;188:256-63. [40] Zhai JL, Wooster TJ, Hoffmann SV, Lee TH, Augustin MA, Aguilar MI. Structural Rearrangement of beta-Lactoglobulin at Different Oil-Water Interfaces and Its Effect on Emulsion Stability. Langmuir. 2011;27:9227-36. [41] Tokle T, McClements DJ. Physicochemical properties of lactoferrin stabilized oil-in-water emulsions: Effects of pH, salt and heating. Food Hydrocolloids. 2011;25:976-82.

19 Page 19 of 26

[42] Ye A. Surface protein composition and concentration of whey protein isolate-stabilized oilin-water emulsions: Effect of heat treatment. Colloids and Surfaces B-Biointerfaces. 2010;78:249.

ip t

**[43] Delahaije RJBM, Wierenga PA, Giuseppin MLF, Gruppen H. Comparison of HeatInduced Aggregation of Globular Proteins. Journal of Agricultural and Food Chemistry.

cr

2015;63:5257-65.

us

- A comprehensive study of influence of colloidal interactions on the stability of globular proteincoated lipid droplets

an

[44] Li J, Ye A, Lee SJ, Singh H. Influence of gastric digestive reaction on subsequent in vitro intestinal digestion of sodium caseinate-stabilized emulsions. Food & Function. 2012;3:320-6.

M

[45] Sarkar A, Goh KKT, Singh H. Properties of oil-in-water emulsions stabilized by beta-

d

lactoglobulin in simulated gastric fluid as influenced by ionic strength and presence of mucin.

te

Food Hydrocolloids. 2010;24:534-41.

[46] Nakauma M, Funami T, Noda S, Ishihara S, Al-Assaf S, Nishinari K, et al. Comparison of

Ac ce p

sugar beet pectin, soybean soluble polysaccharide, and gum arabic as food emulsifiers. 1. Effect of concentration, pH, and salts on the emulsifying properties. Food Hydrocolloids. 2008;22:1254-67.

[47] McClements DJ, Decker EA, Choi SJ. Impact of Environmental Stresses on Orange Oil-inWater Emulsions Stabilized by Sucrose Monopalmitate and Lysolecithin. Journal of Agricultural and Food Chemistry. 2014;62:3257-61.

20 Page 20 of 26

Graphical Abstract

ip t

“Progress in natural emulsifiers for utilization in food emulsions” Bengu Ozturk and David Julian McClements

Ac ce p

te

d

M

an

us

cr

Current Opinion in Food Science.



Proteins, polysaccharides, phospholipids, and saponins can be used as natural emulsifiers in the food industry

21 Page 21 of 26

Figure 1. The effectiveness of emulsifiers can be compared by plotting mean particle diameter (d32) versus emulsifier concentration (C) under standardized

ip t

homogenization conditions (pressure and number of passes).

cr

Figure 2. Proposed interfacial structures of different kinds of natural emulsifiers.

us

Figure 3. The effectiveness of different emulsifiers can be compared by plotting

an

mean particle diameter (d32) versus emulsifier concentration.

Figure 4. The effectiveness of different emulsifiers at stabilizing oil droplets

M

against pH-induced aggregation: particle diameter/initial particle diameter versus

Ac ce p

te

d

pH.

22 Page 22 of 26

us

cr

i

*Manuscript

1

Droplet size limited by homogenizer

M an

Droplet size limited by emulsifier

0.6

Ac

0.2

ed

0.4

Emulsifier-poor Regime

Emulsifier-rich Regime

ce pt

d32 (mm)

0.8

dmin

Cmin

0

0

0.5

1

1.5

2

C (wt%) Figure 1. The effectiveness of emulsifiers can be compared by plotting mean particle diameter (d32) versus emulsifier concentration (C) under standardized homogenization conditions (pressure and number of passes).

Page 23 of 26

i cr us

-

-

M an

-

-

-

-

-

ed

-

-

-

-

ce pt

-

-

-

Globular Proteins

-

Flexible Proteins

-

Polysaccharides

Ac

Saponins

Phospholipids

Figure 2. Proposed interfacial structures of different kinds of natural emulsifiers. Page 24 of 26

i cr us M an

Formation

Lecithin Saponins

5 D32 (µm)

Gum Arabic

ce pt

ed

Whey Protein

Ac

0.5

0.05 0

2

4

6

8

10

C (%)

Figure 3. The effectiveness of different emulsifiers can be compared by plotting mean particle diameter (d32) versus emulsifier concentration. Page 25 of 26

i cr M an

us

Stabilization

1000

10

Gum Arabic

ed

Whey protein

Ac

1

Saponins

ce pt

d/dinitial

100

Lecithin

0.1 2

3

4

5

6

7

8

pH Figure 4. The effectiveness of different emulsifiers at stabilizing oil droplets against pH-induced aggregation: particle diameter/initial particle diameter versus pH.

Page 26 of 26