Emulsifiers+Q&A

by Tan Lee Hoon
 * Emulsifiers Q&A**

**1.** **Describe the chemical structure of emulsifiers that influence their functionality in food systems.** An emulsifier consists of two parts: a lipophilic hydrocarbon chain and a hydrophilic polar group. Many substances, monoglyceride being the most common example, exhibit this combined hydrophilic/lipophilic nature. Many chemical variations of the basic emulsifier structure exist. Some are chemical modifications of monoglycerides such as ethoxylated monoglycerides, or organic acid esters of monoglycerides, while others are totally different substances. One such group of emulsifiers is the stearoyl lactylates made by combining either calcium or sodium with stearic and lactic acids. Natural emulsifying ingredients exist as well, such as lecithin which is derived from soybean oil. The functional component of lecithin is a mixture of phospholipids. Like the basic emulsifier structure, these phospholipids have a hydrophilic polar head. The lipophilic portion of the molecule, however, has two fatty acid tails. The various phospholipids can be separated out through fractionation to give specific functional properties to the lecithin. In addition, the lecithin can be modified in many other chemical ways similar to the way monoglycerides are altered.

**2.** **What are the general classifications of emulsifiers?** a. HLB. The HLB or hydrophilic/lipophilic balance ranges from zero to 20. This scale indicates an emulsifier's relative overall attraction to either oil or water. A low HLB indicates a strongly lipophilic emulsifier, while a high HLB indicates one that is strongly hydrophilic. b. Ionic charge. When dispersed in an aqueous medium, certain emulsifiers will exhibit a negative (anionic) charge. These ionic emulsifiers, including the stearoyl lactylates and diacetyl tartaric acid esters of monoglycerides, have a carboxylic acid group on the molecule's ester. c. Crystal stability. Like the fats many emulsifiers are made from, emulsifiers have polymorphic properties that allow them to exist in different crystal forms: (alpha), (beta) and (beta prime). Like fats, most emulsifiers will crystallize in the less stable (alpha) form initially, then transform to one of the more stable (beta) forms. The stability of the crystals increases in the following order:

(alpha) < (beta prime) < (beta) **3.** **Briefly describe the basic functions of emulsifiers in food systems.** -At the interface between the emulsifier droplets and the continuous phase, the lipophilic portion of the molecule orients towards the oil phase whereas the hydrophilic portion orients towards the water phase -Droplets are thus prevented from coalescing with one another and from breaking the emulsion || -When starch is dispersed in water and heated, the granules absorb water and swell (gelatinization) -Once gelatinization is complete and heat is removed, the starch molecules gradually associate more closely with one another, forcing the absorbed water out until the starch recrystallizes (retrogradation) -Emulsifiers complex with the amylose in starch by "docking" their lipophilic tails inside the linear amylose’s helical structure, thus inhibiting retrograding || -Mixer blades break the surface more easily to incorporate air || -Emulsion is de-stabilized and fat agglomerates into clusters -The liquid cream’s viscosity increases and aeration is promoted, while the agglomerates stabilize the air cells once the air is incorporated || -Emulsifier used must not be polymorphic -Emulsifier used should also be lipophilic enough to be fully soluble in the food product's fat system -The emulsifier must have a higher melting point and crystallize more rapidly than the product's fat does || -The lipophilic portion of the emulsifier’s molecules align with the fat in a fat-containing mix and leave the hydrophilic portion of the interface exposed, thus giving the particle greater affinity for water to aid dispersion -Emulsifier levels range from 0.3% to 0.7% -Lecithin is the most commonly used emulsifier because it is inexpensive || -Lecithin is the most commonly used emulsifier because it is inexpensive ||
 * **Function** || **Description** ||
 * Emulsification || - Emulsifiers help maintain emulsions created by mechanical energy
 * Starch complexing || -Emulsifiers help inhibit retrogradation
 * Foam stabilization/ aeration || -Emulsifiers increase the whipping rate of cake batters by reducing the surface tension of their aqueous phase
 * ^  || -Emulsifiers stabilize the foam in ice cream and whipped toppings by displacing the protein from the fat globule surface to the aqueous phase
 * Protein interaction || -Emulsifiers, especially the ionic ones such as the stearoyl lactylates, interact with gluten proteins in baked products to build a stronger gluten network ||
 * Crystal modification || -Emulsifiers are used to modify the fat crystals in fat-containing food products so that large crystal formation can be inhibited, thus yielding ifiera product with much smoother texture
 * Instant mixes || -Emulsifiers improve the dispersion of instant mixes by counteracting with the oil on the surface of the powder
 * Release agents || -Emulsifiers are used as lubricants to help curb the sticking of food products to the equipments in food processing plants

**4. How are emulsions formed?** Emulsions are formed when one immiscible phase is dispersed in another through mechanical action such as homogenization. Oil-in-water (O/W) emulsions are formed when oil is dispersed in an aqueous phase (e.g., mayonnaise) while water becomes the dispersed phase in water-in-oil (W/O) emulsions (e.g., margarine). Emulsions are also called surface active agent or surfactant because they help keep the immiscible phases in an emulsion together. This is because emulsions are amphiphilic and thus have properties that are compatible with both the hydrophilic and lipophilic portion of the mixture. Non-polar ends of an emulsifier align themselves within the lipid phase, while the polar ends align in the water phase. As a result, an electrically charged surface forms between the two immiscible phases, or at the interface, causing particles to repel one another rather than coalesce.

**5. What is the difference between protein-based emulsifier and lipid-based emulsifier?** In protein-based emulsifier, proteins adsorbed at the interface between the two immiscible phases. It is during the adsorption process that the protein begins to unfold, thereby exposing its more hydrophobic groups to the hydrophobic phase of the emulsion. Therefore protein form a viscoelastic gel at the interface as they interact with one another. This viscoelastic gel stretches and deforms as it accommodates deformations in the interface, thus preventing coalescence. In lipid-based emulsifiers, lipids provide stability by causing the rapid diffusion of liquid from areas of high surface tension to regions of low tension, which occurs when there is a gradient in the surface tension at the interface. This phenomenon is known as the Gibbs-Marangoni effect.

**6. Describe the ways in which an emulsion can be destabilized.** Destabilization of an emulsion can occur in various ways, such as: a. Creaming. A gravitational separation of phases (i.e., oil phase floats to the surface). b. Flocculation. Clumping without a disruption to the interfacial film. A reversible process. c. Coalescence. The interfacial film is disrupted as droplets collide and form a separate phase. An irreversible process.

**7. ****List the factors that could influence the stability of an emulsion. ** a. Interfacial tension b. Viscosity of the continuous phase c. Density differences between phases, e.g. ester gum is added to flavour oil in beverages to “weight it” and prevent ringing d. Droplet size in the internal phase, i.e. the smaller the size, the more stable the emulsion e. Temperature extremes f. The presence of solids i. Finely divided solids “wetted” equally well by both phases at the interface stabilize the emulsion. ii. A higher percentage of solids dispersed in the internal phase destabilize the emulsion.

**8. ****Determine the type of hydrophilic/lipophilic balance (HLB) that you would select for (a) an oil/fat continuous product and (b) an aqueous system. Give reason(s) for your answer. ** a. Low HLB. Low HLB ingredients are more oil-soluble b. High HLB. High HLB ingredients are more water-soluble.

**9. ****Explain the Gibbs-Marangoni effect in emulsifiers. ** <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">Emulsions can be stabilized by both proteins and low-molecular weight surfactants (LWS) such as monoglycerides. LWS stabilize an emulsion by congregating at the surface interface between an aqueous and air or oil phase. <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">When oil droplets (e.g. in a salad dressing) or air cells (e.g. in a whipped cream) are made smaller and more numerous, the film (e.g. aqueous inter-lamellar phase) thins and the interface surface area increases. LWS molecules are thus thinly spread at the interface surface, and surface tension increases. <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">The **“Gibbs effect”** occurs when surface tension equilibrium is restored as more LWS are pulled from the interior of the aqueous phase to the interface surface. The **“Marangoni effect”** occurs when surface tension equilibrium is restored by the LWS moving sideways or diffusing along the interface surface to help fill in the thinning ranks of LWS, therefore dragging along the aqueous liquid with which each LWS molecule is associated.

**<span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">10. ****<span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">What are the properties that manufacturers will look for in a good emulsifier? ** <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">A good emulsifier must have the following characteristics: a. Ability to reduce interfacial tension b. Rapid absorption at the interface c. Proper balance of hydrophilic and hydrophobic groups to stabilize different kinds of emulsions d. Functions effectively at low concentrations e. Ability to resist chemical changes f. No odour or colour g. Non-toxicity h. Economy

**11.** **How are emulsifiers useful in the bakery industry?** Emulsifiers may be used in doughs for breads and cakes to enhance dough conditioning, ensure the product rises properly and inhibit staling. The emulsifier (e.g. a mono- or diglyceride) reacts with the protein component in the flour to make the bread rise smoothly. At the same time, it reacts with the starch to ensure the bread is soft.

**12.** **Briefly describe the properties of whey proteins which make it useful in food emulsifier applications.** <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">Whey adds texture, water binding, opacity and adhesion. It also serves as a fat mimetic, by providing efficient fat dispersion and stable emulsions.

**<span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">13. ****<span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">How does an emulsion get broken down? ** <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">The breakdown of an emulsion occurs because of the gravitational forces acting on phases of different densities. The breakdown occurs through a variety of different mechanisms, such as: a. **Creaming**. Creaming occurs when non-crystallized, liquid-oil droplets have a lower density than the surrounding water phase. As a result, these lighter particles drift upward toward the surface of the emulsion, where they aggregate. b. **Sedimentation**. Sedimentation occurs when droplets with a higher density fall downward to the bottom. The form of aggregation can be further divided into flocculation and coalescence: i. **Flocculation** – The dispersed droplets clump together but maintain individual identity. ii. **Coalescence** – The droplets collide and become one big particle.

**14.** **How do colloidal interactions determine the behavior of emulsion droplets in a food product?** Colloidal interactions such as van der Waals, steric, electrostatic, depletion, and hydrophobic interactions determine whether emulsion droplets aggregate or remain as separate entities, thereby impacting the characteristics of any aggregates formed including their size, shape, porosity and deformability. Generally, droplets tend to aggregate when attractive interactions dominate, but remain as individual entities when repulsive interactions dominate.

**15.** **Briefly describe the formation of a two-layer interfacial membrane.** A two-layer interfacial membrane is formed in two steps. First, the primary emulsion is created by homogenizing an oil-in-water emulsion with a charged emulsifier. Then, a secondary emulsion is developed by adding a biopolymer to the primary emulsion. The biopolymer and the droplets in the primary emulsion should be oppositely charged. Mechanical agitation may be necessary to disrupt any aggregated particles created by the formation of the second layer. Each individual emulsifier or biopolymer may react differently as processing parameters change. Also, the magnitude of the electrical charge might influence long-term stability of the membrane. The type and magnitude of the electrical charge can be controlled by varying the emulsifier selection and/or altering the pH above or below the isoelectric point of a protein-stabilized emulsion.

**16.** **Discuss the functionalities of and misconceptions about emulsifiers used in yeast-raised and chemically leavened products in the bakery industry.** -Emulsifiers increase the amount of binding sites that gluten strands have to each other and/or form bridges to supplement disulfide linkages, thus improving the binding of wheat flour gluten strands to each other, which results in a stronger gluten film. -E.g. sodium- and calcium stearoyl lactylate (SSL and CSL), ethoxylated mono- and diglycerides (EMG), polysorbates (PS), succinylated monoglycerides (SMG), and diacetyl tartaric acid esters of monoglycerides (DATEM) || 1. __As aeration/foam stability__ <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">-Emulsifiers: <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">a. coat the air cells in foams to provide foam stabilization; and <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">b. increase the amount of air that can be whipped into the batter by decreasing the surface tension of the aqueous phase, thereby increasing the whipping rate of batters. <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">-Emulsifiers enable more uniform air cells to be generated which act as nucleation sites for the dissolved carbon dioxide gas (a leavener) to form bubbles in the cake batter resulting in a cake with improved grain, more even cell structure, and increased volume. -E.g. Monoglycerides, lactic acid esters, propylene glycol esters, polyglycerol esters, and polysorbates. || <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">-Emulsifiers form complexes with amylose, a linear polysaccharide within the starch molecule, which interferes with the recrystallization (or retrogradation) of amylose, therefore retarding the firming rate. -E.g. dispersible forms of monoglycerides (saturated types), typically used at 0.5% to 1.0% of the flour weight; CSLs, SSLs, DATEMs, and SMG || <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">2. __For emulsification__ <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">-Emulsifiers, especially hydrophilic types, aid in fat dispersion by breaking the fat into a large number of small particles so that the fat phase could mix with the other ingredients. -Emulsifiers coat the fat particles' exterior surface, providing protection to the protein film cell walls and eliminating film disruption that would be cause by shortening ingredients (antifoaming agents) in the cake batter. || <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">-Emulsifiers aid in moisture retention and efficiency of shortening action, as well as starch complexing, thus providing a cake with higher volume, a more tender and uniform crumb, better crust appearance and increased shelf life. <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">-E.g. monoglycerides, polyglycerol esters, or SSLs (used in combination with "alpha-tending" emulsifiers such as PGME, acetylated mono glycerides, or lactylated monoglycerides). ||
 * **<span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">Yeast-raised products ** ||  **<span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">Chemically Leavened Products **  ||
 * 1. __As dough conditioners/strengtheners (protein interaction)__
 * 2. __As crumb softeners (starch complexers)__
 * ^  || 3. __As crumb softeners__

**17.** **What are the benefits of dough conditioners used in baked products?** <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">a. Compensation for variations in raw materials (e.g. flour quality). <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">b. Improved dough machinability by gluten complexing. <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">c. Greater tolerance to production abuse of dough by providing a drier, less sticky dough. This reduces tearing and facilitates processing. <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">d. Ease of formulating low-fat products; reduction in shortening or oil with no loss of volume, tenderness, or slicing ease. <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">e. Increased gas retention, resulting in lower yeast requirements, improved oven spring, shorter proof times, and increased volume. <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">f. Better texture of finished product - i.e., finer grain. <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">g. Stronger side walls, improved symmetry, and reduction of deformed products. <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 115%;">h. Improved hydration rate of the flour and other ingredients.

**18.** **Briefly describe the functions and use of the various types of dough conditioning ingredients in bread.** <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">E.g.: <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">-Azodicarbonamide (ADA) <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">-L-ascorbic acid (LAA) or vitamin C || <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">-Strengthens the dough by "stripping" the hydrogen atoms from the sulfur-hydrogen (sulfhydryl) linkages on protein molecules to make more sulfur available for the gluten-strengthening disulfide bond <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">-Shortens makeup times or compensates for low protein in the flour || <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">E.g.: <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">-L-cysteine <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">-Sulfites <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">-Reduced glutathione (in the form of deactivated yeast) || <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">-Encourages gluten development by disrupting the disulfide bonds between and within protein molecules, weakening the protein structures and allowing the oxidizer to rebuild the disulfide bonds between the now-unfolded proteins <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">-Shortens the mixing time and decreases the amount of mixing energy that is needed || E.g.: -Diacetyltartaric acid esters of monoglycerides (DATEM) -Stearoyl lactylates (SSL) -Lecithin || <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">-Strengthens the dough by making it more extensible so that is could trap more gas in smaller bubbles and becomes more tolerant to over- or under-mixing. <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">-Reduces proofing time; gives a softer, more even-textured bread; give improved mixing and handling tolerance; increase loaf volume; improve mechanical slicing characteristics; and can retard staling || E.g.: -Amylase -Protease -Lipoxygenase || <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">-Enhance gas production by yeasts and can help control the strength of the dough <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">-**Amylase** converts starch to sugar for the yeast, which increases gas production. Amylase will also delay the gelatinization of the starch during baking, giving more "oven spring." Both of these effects result in increased loaf volume. <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">-**Protease** irreversibly weakens the gluten strands, thus breaking down protein and can be used to counteract very strong flours, i.e. flours with very high protein content. <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">-**Lipoxygenase** releases oxidizers which bleaches the flour’s natural pigments, making a whiter loaf. The oxidizers also increase the gluten strength in the same manner as ascorbic acid or ADA. ||
 * **Type** ||  **Function/use**  ||
 * **<span style="font-family: "Times New Roman","serif"; font-size: 12pt;">Oxidizing agents **
 * **<span style="font-family: "Times New Roman","serif"; font-size: 12pt;">Reducing agents **
 * **Emulsifiers**
 * **Enzymes**