Mayonnaise production method

Objective:

1. To determine the type of food emulsion obtained by varying the mixture sequence

2. To produce the home made mayonnaise

Introduction:

Mayonnaise is a creamy, pale yellow, and mild-flavored food product which is frequently used in preparation of salads, sandwiches, and many other food products. Although the production of mayonnaise consisting of relatively few ingredients and processing steps, but successful formulation and processing are required an understanding of the role of each ingredient and the critical processing steps in order to create the delicate structure of mayonnaise. Mayonnaise is a unique emulsion which contains the mixture of water and oil. The major component in the mayonnaise is oil which dispersed throughout the lesser amount of continuous aqueous phase (water). The structure of mayonnaise is easily disrupted because of this unusual relationship between the oil and aqueous phase. Integration of processing and colloid chemistry is essential to understanding the formation and stabilization of the mayonnaise.

In this experiment, the mayonnaise is made by using 75% of oil, 8% of fresh egg yolk, 1% of mustard powder, 1.5% of salt, 1.3% of distilled water, and 13.2% of vinegar in producing mayonnaise. In a colloidal system, the minor component (dispersed phase) is usually being dispersed throughout the dispersion medium. However, the major component in mayonnaise (oil) is forced to be fine droplets to disperse throughout the lesser amount of continuous aqueous phase (dispersed medium). Mayonnaise is known as an oil-in-water (o/w) emulsion. When the emulsion of mayonnaise breaks, the water (dispersed phase) does not dispersed in oil (dispersed medium) and hence this allows the phenomenon of creaming formation to occur.

In order to maintain the stability of emulsion in mayonnaise, emulsifier acts as the most important role to stabilize the unique emulsion since the high amount of oil in water does not favor the formation of o/w emulsion. An emulsifier works at the surface of two immiscible liquids and tends to reduce to interfacial tension between two different liquids by reinforcing the in contact surface between them. The larger the ratio of surface area to volume of oil, the smaller the oil droplets dispersed in the water. Finer dispersion of oil droplets is required more emulsifier to surround them and thus this can maintain the stability of emulsion in the system. If emulsifier is not added, the two immiscible liquids will quickly separate after they mixed. Thus, emulsifiers are liaisons between the two liquids and serve to stabilize the mixture. In producing the mayonnaise, artificial emulsifier is not allowed. So, the source of emulsifier is normally obtained from egg yolk for stabilization of mayonnaise. The egg must be totally dissolved in the water before the addition of oil begins so that to achieve more efficient emulsion. Lecithin is a low molecular mass surfactant that can be found in egg yolk which acts as a hydrophilic effective emulsifier in oil-in-water emulsion.

Emulsion activity of emulsifier is based on its molecular structure. There is a hydrophobic part with a good non-aqueous solubility and hydrophilic part that is soluble in water. The hydrophobic part of the molecule is generally a long chain alkyl residue while the hydrophilic part of the molecule consists of a dissociable group. In a system containing two immiscible liquids such as oil and water, the emulsifier is located in the interface between two liquids which tends to reduce the interfacial tension of each liquid. The alkyl residues are solubilized in the oil droplets whereas the negatively charge of end group projected to the water. It maintains the stability of emulsion by involving the double electrostatic layer. The adsorption of negatively charge end group on the surface of oil globules causes the formation of a negative layer around them. Eventually, the oppositely charge particles will tend to approach to the particular negative layer and hence forming the second layer. This is known as double electrical layer. The electrical double layer creates repulsive forces greater than the attractive forces between the oil droplets. Hence, it can maintain the oil droplets from combining to each other in the emulsion.

Scattering light is one of the characteristics of colloidal system. Emulsion always exhibits the similar characteristic with colloidal suspension which is scattering the light. The oil-in-water emulsion present as a cloudy and turbid because of the existence of oil droplets dispersed in the aqueous phase. This is because the many phase interfaces between the two liquids scatter the light which passes through the emulsion system. The basic colour of emulsion is white. The Tyndall effect will scatter the light and distort the colour to blue if the emulsion is dilute. In a concentrated emulsion, the colour of emulsion system will scatter light and then distort the colour to yellow.

Several ways have been proposed to determine type of emulsion formed. The drop-dilution method can be used to determine the type of emulsion. To a small portion of the emulsion, add some water and stir slightly. If the water blends with the emulsion, it is an oil-in-water emulsion, but if oil blends with the outside phase it is a water-in-oil emulsion.

Another method of determining the type of emulsion is to use Sudan III, red dyes soluble in the oil but not in the water. A small portion of the finely powdered dye is dusted over the surface of the emulsion. If oil is the external phase the color gradually spreads throughout the emulsion. But if water is the external phase the color does not spread but is confined to the oil with which it comes in contact on the surface.

The microscope may be used to determine the type of emulsion formed. If the oil is dyed red, a red field with clear globules indicates a water-in-oil emulsion; red globules in a clear field show an oil-in-water emulsion. Sometimes a multiple emulsion is obtained, for example, a dispersed phase dispersed within a dispersed phase. The only means of identifying a multiple emulsion is by using the microscope.

Apparatus: beaker, measuring cylinder, glass rod

Materials: oil, egg yolk, salt, mustard powder, distilled water, vinegar

Procedure:

Three manufacturing procedures were investigated in order to illustrate the importance of the manufacturing procedure on emulsion stability.

Ingredients	%	Weight or volume
Oil	75.0	75 g
Egg yolk	8.0	8 g
Salt	1.5	1.5 g
Mustard powder	0.1	0.1 g
Distilled water	1.3	1.3 ml
Vinegar, distilled 5% acetic acid	13.2	13.2 ml
Total	100.0	100 g

In this formula, 30% of the aqueous ingredients equals to 99g water. In all the cases, make a paste of the mustard in a little water before using.

Procedure A

All the ingredients were mixed well in a beaker and stirred by using glass rod for 30 minutes.

Procedure B

1. The mustard powder, salt, water, vinegar, and egg yolk were mixed in a beaker.

2. The oil was slowly added into the mixture while stirring. Stir for 30 minutes.

Procedure C

1. Egg yolk was added to the beaker and blended thoroughly.

2. In a separate beaker, the mustard powder, 1.3g of water, 3.2g of vinegar, and salt were blended.

3. The mixture was stirred until all the salt dissolved.

4. The mixture was added into the egg yolk and was stirred for 5 minutes.

5. At this point, the oil was slowly added while stirring.

a. First 5 minutes, 10-15% of oil was added. The first addition should be small and gradual. Wait about 1 minute between additions.

b. During the next 15 minutes, 50% of oil was added.

c. During last 5 minutes, the remaining of oil was added.

6. Gradually add the remaining vinegar and stir for 5 minutes.

Take the observation on the three different mixtures on viscosity and dilution test.

Results:

Mixture	Procedure A	Procedure B	Procedure C
Viscosity	Low viscous	Moderately viscous	Highly viscous
Dilution test	Water in oil (W/O)	Water in oil (W/O)	Oil in water (O/W)

Suspension-sedimentation

Objective:

1. To obtain a good formulation in controlling the rate of flocculation and sedimentation

2. To study the formation of flocculation

3. To study the relationship between flocculation and sedimentation

Introduction:

In colloid chemistry, a heterogeneous mixture contains the solid particles with a diameter more than 1μm which are large enough to settle out from the liquid through sedimentation is known as suspension. Suspension is a coarse dispersion in which the insoluble particles dispersed in a liquid medium and it will settle out of the liquid after left for some time. Suspension shows difference with a solution in which the solute does not exist in the solid form and the solvent and solute are homogeneously mixed. Suspension is thermodynamically unstable due to the properties of suspension is always changing with time as they will undergo sedimentation. Suspension may be flocculated or deflocculated.

Sedimentation is a process of the particles settle down to the bottom of the solution. This is due to the instability of the particles in the system. The factors that affect the sedimentation are particles size, densities of dispersed phase and dispersed medium, temperature of liquids and the viscosity of the liquid. In a colloidal system, the particles are apart from each other due to their double layer charge. In suspension, the particles also possess the particular surface charges, but the attractive force in between the suspending particles are greater (after flocculating agent was added) than the repulsive force causes the particles to bind together and form larger particles. Usually, the forces acting on the particles that cause sedimentation occurs due to the gravity. The larger particles will sink to the bottom through sedimentation process which will accumulate in the bottom and the particles stack on the sediment. The sedimentation rate can be calculated by using the formula as shown in the following:

The second factor is the densities between the dispersed phase and dispersed medium. Generally, the density of dispersed phase (particles) is greater than the dispersed medium, however in certain cases particle density is less than dispersed phase, so suspended particle floats is difficult to distribute uniformly in the system. If density of the dispersed phase and dispersion medium are equal, the rate of settling becomes zero hence sedimentation does not occur. Temperature and viscosity of liquid are highly in related in which the temperature might affect the viscosity of the liquid. If the liquid is highly viscous, the sedimentation rate of the particles will be slower compared to the less viscous liquid. This is because when the terminal velocity decreases, the dispersed phase will settle at lower rate which may remain dispersed for longer time. The viscosity is known as the resistance of a substance to motion under an applied force.

Flocculation is a process of destabilizing the suspending particles in suspension by adding in certain chemicals called flocculating agent. In industry, this process is purposely used to cause the particles suspended in solution to aggregate into clumps or masses that then sink or else it can be removed easily by filtering. The formation of floc is due to the decrease in Zeta potential (in slipping plane) between the particles until Van der Waals forces predominate. Usually, the larger particles are known as floccules. The floc may float on the surface of liquid instead of sediment at the bottom if the density of floc is less dense than liquid’s density. This is known as creaming. The flocculating agent are includes neutral electrolyte (eg: KCl, NaCl), surfactant, and polymers. When the neutral electrolyte added into the suspension, it will affect the electrical barrier between the particles and hence the Zeta potential could be altered. For surfactant, the cationic and anionic surfactant could bring about the flocculation of suspended particles. However, optimum concentration is necessary because these compounds acting as the wetting agents to achieve dispersion. Surfactant decreases the surface energy by reducing the interfacial tension between the particles which attracted by van der Waals force and the solvent-particles’ interfacial tension. Besides, the addition of polymeric flocculating agents can induce the floc formation. The polymers possess long chain in their structure. The long chain will adsorb on the surface of the particles and the remaining part projecting out into the dispersed medium. The formations of bridging between these later portions tend to cause the formation of floc.

The flocculation process is reversible if the interaction forces between the floc are not strong. Floccules form when weak van der Waals forces are holding the particles together. However, the floccules are easily to re-suspend by shaking. If the floccules trap solvent during sedimentation, they are easily to be broken apart. Otherwise, the flocculation is considered as non reversible if the particles settle into a tighter aggregate by the strong interaction force without trapped solvent. Most of the flocculants are multivalent cation and anion which are able to neutralize the different charges (positive charge or negative charge) of the particles suspended in liquid. After overcome the surface charges of the suspending particles, the particles can easily to form floccules since their barrier have been minimized. Other than that, the deflocculation to form may be occurred once the magnitude of Zeta potential of the particles achieve sufficiently positive or negative (usually more than +30mV or less than -30mV). Thus, the phenomenon of flocculation and deflocculation depends on zeta potential carried by particles.

Apparatus: boiling tube, stopwatch, test tube rack

Materials: potassium dihydrogen phosphate, purified water, bismuth subnitrate, methylcellulose, parafilm

Procedure:

1. 40ml of flocculating reagent (potassium dihydrogen phosphate) was prepared which will be used in four of five suspensions.

2. Five 25ml graduated cylinder were assembled and were numbered consecutively. 2g of bismuth subnitrate was added to each boiling tube.

3. Sufficient water was added to make the 25ml of suspension in the 1^st boiling tube.

4. 10ml of anionic flocculating reagent solution was added into the 2^nd boiling tube and enough water was added to make 25ml.

5. 10ml of anionic flocculating reagent solution was added into the 3^rd boiling tube and 0.5% methylcellulose was added to make 25ml.

6. 10ml of anionic flocculating reagent solution was added into the 4^th boiling tube and 1.0% methylcellulose was added to make 25ml.

7. 10ml of purified water was added into the 5^th boiling tube and sufficient 0.5% methylcellulose was added to make 25ml.

8. All the boiling tubes were covered with parafilm.

9. Each of them was inverted for several time to mix tehm well. The height of suspension were measured and recorded after 15minutes, 60minutes, and 120minutes.

Results:

Table 1 The height of sedimentation in each boiling tube over the time

Number of boiling tubes	Mixture in the boiling tubes	0min	15mins	60mins	120mins
First	2g bismuth nitrate + water	6.5cm	0.3cm	0.3cm	0.5cm
Second	2g of bismuth subnitrate+10ml of flocculating agent+water	6.5cm	1.2cm	1.5cm	1.6cm
Third	2g of bismuth subnitrate+10ml of flocculating agent+0.5% methylcellulose solution	6.5cm	2.0cm	1.2cm	1.6cm
Fourth	2g of bismuth subnitrate+10ml of flocculating agent+1% methylcellulose solution	6.5cm	1.4cm	1.5cm	1.3cm
Fifth	2g of bismuth subnitrate+10ml of purified water+0.5% methylcellulose solution	6.5cm	0.0cm	0.0cm	0.0cm

Table 2 The height of suspension in each boiling tube over the time

Number of boiling tubes	Mixture in the boiling tubes	0min	15mins	60mins	120mins
First	2g bismuth nitrate + water	0.0cm	6.2cm	6.2cm	6.0cm
Second	2g of bismuth subnitrate+10ml of flocculating agent+water	0.0cm	5.3cm	5.0cm	4.9cm
Third	2g of bismuth subnitrate+10ml of flocculating agent+0.5% methylcellulose solution	0.0cm	4.5cm	5.3cm	4.9cm
Fourth	2g of bismuth subnitrate+10ml of flocculating agent+1% methylcellulose solution	0.0cm	5.1cm	5.0cm	5.2cm
Fifth	2g of bismuth subnitrate+10ml of purified water+0.5% methylcellulose solution	0.0cm	6.5cm	6.5cm	6.5cm

Precaution steps:

1. Do not shake or move the boiling tubes consist of suspension.

2. Make sure the content in each boiling tube is mixed well.

3. Make sure all the boiling tube are properly covered by parafilm

Verification of the Henderson-Hasseblach Equation Using Buffer Solution

Objectives:

1. To study the validity of Henderson-Hasseblach equation to a buffer system

2. To determine the buffer capacity of a buffer solution

Introduction:

Buffers are solutions that maintain a relatively constant pH when an acid or a base is added into a buffer solution. They protect other molecules in solution from the effects of the added acid or base. Buffer solution contains either a weak acid (HA) and its conjugate base (A^-) or a weak base (B) and its conjugate acid (BH⁺). They are extremely important for the proper functioning of biological systems such as blood, which is a natural example of buffer solution.

An acid is defined as a substance that can dissociate in water to produce hydrogen ions, H⁺ while a base is a substance that can dissolve in water to produce hydroxide ions, OH^-. The acid is categorized into two groups which are strong acid and weak acid. Strong acid is the acid that dissolves completely in water to produce a lot of H⁺ ions whereas weak acid is the acid that ionizes partially in water to produce less H⁺ ions.

An important characteristic of weak acids and weak bases is their ability to form buffer systems. The action of a buffer is caused by the presence of both the weak acid and its anion or the weak base and its cation. These are known as conjugate acid-base pair. If strong base is added into a weak base, it will dissociate into OH^- and conjugate acid. The conjugate acid produced will neutralize the base added and hence control it pH. On the other hand, if string acid is added, the weak base will react with the strong acid by neutralizing it. So, the pH of the solution can be maintained. This is same applied by the acid buffer system with H⁺ ion and its conjugate base.

Consider a sodium acetate-acetic acid buffer system in which containing the same amounts of acetic acid (CH₃COOH) and its conjugate base, acetate ion (CH₃COO^-). When the addition of a strong acid hydronium ion (H₃O⁺) to the solution. The acetate ion (base form) in the buffer reacts with the hydornium ion to neutralize it.

In the same way, the addition of the strong base provide hydroxide ion, OH^- to the solution, then the acetic acid will reacts with this ion and neutralize it.

The amount of strong acid or base can be added to a given volume of a buffer system without a significant change in pH in +/- 1.0 unit. This is known as the buffer capacity of a buffer system.

The strength of acid is depends on the degree of H⁺ ionization in the water. For base, its strength is depends on the degree of OH^- ionization in the water.

The magnitude of the equilibrium constant for an ionization reaction can be used to determine the relative strengths of acids and bases. The equilibrium constant for acid dissociation is

The equilibrium constant for base dissociation is

In order to obtain Henderson Hasselbalch equation, rearrange the following equation:

Buffer capacity of a buffered solution is defined as in terms of the amount of protons or hydroxide ions it can absorb without a significant change in buffer. A buffer with a large capacity contains large concentration of the buffering components and thus can absorb a relatively large amount of protons or hydroxide ions and show little pH change. The pH of a buffer system is determined by the ratio [A^-]/[HA]. The capacity of a buffer system is determined by the magnitude of [A^-] and [HA]. Buffer capacity is also depends on the concentration of the solution. The greater the concentration of a weak acid and its conjugate base, the greater the buffer capacity. Buffer capacity may expressed as

A buffer solution has the maximum buffer capacity when the ratio or = 1 for acidic buffer and basic buffer respectively. In such a solution pH = pK_a for acidic buffers and pOH= pK_b for basic buffers. A solution can act as buffer only if the ratio of salt to acid or base is between 0.1 and 10. Thus, the pH of an acidic buffer can have the range from pK_a - 1 or pK_a + 1. Similarly, a basic buffer can act as buffer in the pOH range from pK_b – 1 to pK_b + 1.

Materials: standard buffer solution (pH= 4.00), 1 M aqueous sodium hydroxide, 1 M aqueous acetic acid

Apparatus: burettes, beaker (100cm³), pH meter

Procedure:

1. The pH meter is calibrated by standard buffer solution, pH=4.00.

2. 50cm³ of the 1 M acetic acid and 1 M sodium hydroxide are pipetted into a 100cm³ beaker.

3. The solution is mixed thoroughly and pH of the solution is measured.

4. The pH measurement is repeated for further 1 cm³ addition each up to a total of 5cm³ of 1 M sodium hydroxide.

5. The pH of the solution is measured for further 5cm³ additions each up to a total of 45cm³ of 1 M sodium hydroxide.

6. The pH measurement is repeated for further 1 cm³ addition each up to a total of 50cm³ of 1 M sodium hydroxide.

Result and calculation:

Table 1 The average pH value of buffer solution

Volume of aqueous 1 M CH3COOH (X) ,cm3	Volume of aqueous 1 M NaOH (Y), cm3	pH	[ Salt ] / [ Acid ] = y/(x-y)	Log10 ( [ Salt ] / [ Acid ]
50	1	2.97	0.0204	-1.690
50	2	3.26	0.0417	-1.380
50	3	3.45	0.0638	-1.195
50	4	3.58	0.0870	-1.060
50	5	3.69	0.1111	-0.954
50	10	4.06	0.2500	-0.602
50	15	4.32	0.4286	-0.368
50	20	4.54	0.6667	-0.176
50	25	4.74	1.0000	0.000
50	30	4.95	1.5000	0.176
50	35	5.21	2.3333	0.368
50	40	5.65	4.0000	0.602
50	45	10.03	9.0000	0.954
50	46	11.76	11.5000	1.061
50	47	12.03	15.6667	1.195
50	48	12.19	24.0000	1.380
50	49	12.29	49.0000	1.690
50	50	12.37	-	-

Turning point at pH

= (5.65+10.03)/ 2

= 7.84