Lipid Characteristic Lak

CHARACTERISTICS OF LIPID

Name: T.L.V.Peiris

Index No: GS/MSc/Food/3630/08

University : University of Sri Jayawardenapura

Introduction

Lipids are formed from structural units with a pronounced hydrophobicity. This solubility characteristic, rather than a common structural feature, is unique for this class of compounds.Lipids are soluble in organic solvents but not in water. Water insolubility is the analyticalproperty used as the basis for their facile separation from proteins and carbohydrates.Some lipids are surface-active since they are amphiphilic molecules (contain both hydrophilicand hydrophobic moieties). Hence, they are polar and thus distinctly different from neutral lipids.The majority of lipids are derivatives of fatty acids. In these so-called acyl lipids the fatty acids are present as esters and in some minor lipid groups in amide form. The acyl residue influences strongly the hydrophobicity and the reactivity of the acyl lipids.

Primarily triacylglycerols (also called triglycerides) are deposited in some animal tissues and organs of some plants. Lipid content in such storage tissues can rise to 15–20% or higher andso serve as a commercial source for isolation of triacylglycerols. When this lipid is refined, it isavailable to the consumer as an edible oil or fat.The nutritive/physiological importance of lipidsis based on their role as fuel molecules (37 kJ/gor 9 kcal/g triacylglycerols) and as a source ofessential fatty acids and vitamins. Apart from these roles, some other lipid properties are indispensable in food handling or processing.These include their melting behavior and the pleasant creamy or oily taste that is recognized by a receptor, which has recently been identified.Therefore, there are all together six taste qualities. Fats also serve as solvents for certain taste substances and numerous odor substances. On the whole, fats enrich the nutritional quality and are of importance in food to achieve the desired texture, specific mouthfeel and aroma, anda satisfactory aroma retention. In addition, foods can be prepared by deep frying, i. e. by dipping the food into fat or oil heated to a relatively hightemperature.The lipid class of compounds also includes some important food aroma substances or precursors which are degraded to aroma compounds. Some lipid compounds are indespensable as food emulsifiers,while others are important as fat- or oilsolublepigments or food colorants.

4.1. Specific gravity of oils

4.1.1. MaterialsOil samplesSpecific gravity bottlesWeighing scale

4.1.2. MethodPre weighed specific gravity bottle of 50 mL capacity was filled with distilled water at 30 ºC tooverflow and inserted the stopper. After inserting the stopper the bottle was immersed in a waterbath at 30 ºC for 30 minutes. After 30 minutes bottle was removed from the water bath andwiped till it became completely dry.Weight of the bottle and contents was taken.Oil samples were cooled to 30 ºC and filled with oil (coconut oil) to the dried specific gravitybottle as before. Then the stopper was inserted and bottle was wiped off. Weight of the bottle andpalm oil was taken.

Lipid Characteristics

Then the specific gravity of oil was calculated using following formula.

Specific Gravity = W3-W1

W2-W1

Where,W1= Weight of empty SG bottleW2= Weight of SG bottle + WaterW3 = Weight of SG bottle + oil

4.1.3. ResultsFor palm oil


W2-W1

= 73.3815g-29.4648g 77.7672-29.4648g = 43.9167 48.3024 = 0 .91For soya oil


W2-W1

= 74.7305g-28.3128g 79.1478g-28.3128g = 46.4177g 50.8350g = 0.91

4.2. Viscosity of oils

4.2.1. MaterialsViscometer [canon fenska viscometer]Oil samplesWater4.2.2. MethodViscosity of oil samples were measured using Canon Fenska viscometer.100 ml of distilled water was added to the left arm of the viscometer. Time taken for water tomove from lower mark to the upper mark of the right arm was noted. Experiment was repeatedfor five times with water.Same procedure was followed for the oil samples and experiments were repeated for five timesto get an average value.Viscosity was calculated using following formula

Time = Viscosity Density


Results

For palm oil

Time = Viscosity Density55 X60 = Viscosity 0.91 X1000Viscosity = 3003000

For water

Time = Viscosity Density2 X 60 = Viscosity 1000Viscosity = 2 X60 X1000

= 120000

4.3. Saponification value4.3.1. MaterialsWeighing scaleBeakersBurettesPipettesConical flaskPumice stonesAlcoholic KOH0.5 M HCL4.3.2. Method2g of sample was weighed into conical flasks.25 mL of alcoholic KOH and few pieces of pumice stones were added to both samples.Another conical flask was taken and 25mL of alcoholic KOH and few pieces of pumice stoneswere added in order to carry out the blank test.Air flux condensers were fixed to all flasks and allowed them to boil for an hour, shaking flasksfrequently.After one hour samples were titrated with 0.5M HCl.Saponification values of samples were calculated using following formula.

Saponification Value = (b-a) X 28.05 Weight in grams of sample

b – mL of HCl acid used in the blank titrationa – mL of HCl acid used for the sample


Results

For palm oil

Saponification Value = (b-a) X 28.05 Weight in grams of sample = (40.60ml-27.70ml) X 28.05 2.0489 g = 176.60

For Soya oil

Saponification Value = (b-a) X 28.05 Weight in grams of sample = (40.60ml-27.75ml) X 28.05 2.0847 g = 172.89

4.4. Iodine value

4.4.1. MaterialsBeakersIodine titration flaskBurettesPipettesWeighing scaleWij’s solution containing iodine monochlorideKI, 100g/liter solutionSodium thiosulphate 0.1M – 500gCarbon tetra chloride solutionDistilled waterStarch solution

4.4.2. MethodSamples were weighed into small tubes (melting point tubes). For palm oil 0.35 g were taken.Sample containing small tubes were kept in the iodine flasks separately and 20 mL of CCl4 wasadded to each flask. Flask was shook well until the oil gets mixed thoroughly. 20 mL of Wij’sreagent was added to all the flasks. A blank test was also carried out. All the flasks were kept indark for 30 min. After 30 min. 20 mL of 10% KI and 150 mL of distilled water was added toeach flask and titrated with 0.1M sodium thiosulphate solution. Few drops of starch were addedwhen the colour of the solution turned into straw color while titrating. Titration was continuedtill the blue colour turned into colourless.Iodine values for the two oil samples were obtained using the following formula.

Iodine Value = (b-a) X 1.269 Weight of the sample


Where,b - Volume of sodium thio sulphate solution required for the blank testa – Volume of the sodium thio sulphate solution required for the sample

Results

For Palm oil

Iodine Value = (48.40ml-12.01ml) X 1.2690.7951g

= 58.07For Soya oil

Iodine Value = (48.40ml-3.40 ml) X 1.2690.7269g

= 78.56

.5. Acid value

4.5.1. MaterialsConical flasksPipetteWater bathBuretteWeighing scaleHot neutral alcoholIndicator (phenolphthalein)0.5M Sodium hydroxide

4.5.2. Method5 g from sample was weighed into conical flasks and 75-100 mL of hot neutral alcohol wasadded to each flask. Then 0.5 mL of indicator (phenolphthalein) was added and titratedimmediately with 0.5M sodium hydroxide while shaking to the first pink colour which willpersist for 30 seconds.Acid value was calculated using the following formula.

Acid Value = Titrated volume (ml) X M X 56.10 Weight of the sampleResults

For Palm oil

Acid Value = Titrated volume (ml) X M X 56.10 Weight of the sample

= 0.1 ml X 0.5X 56.10 6.4932


= 0.43For Soya oil

Acid Value = Titrated volume (ml) X M X 56.10 Weight of the sample

= 0.1 ml X 0.5X 56.10 5.9546 = 0.47

4.6. Peroxide value

4.6.1. MaterialsBoiling tubeConical flaskPipettesBurettesWeighing scalePowdered potassium iodideGlacial acetic acidChloroform5% potassium iodide solutionDistilled water0.002M sodium thiosulphate solution

4.6.2. Method1g from sample was weighed out into clean dry boiling tubes. 1g of powdered potassium iodideand 20 mL of solvent mixture (2 volumes of glacial acetic acid + 1 volume of chloroform) wereadded to both sample containing boiling tubes and placed them in a water bath in order to makethe solutions boiling within 30 seconds.Then the contents were poured in to a flask containing 20 mL of 5% potassium iodide solution.Tube was washed twice with 25mL of water and titrated with 0.002M sodium thiosulphatesolution using starch as the indicator. Same procedure was done to for the blank.Peroxide value was calculated using the following formula.

Peroxide value = (v-v0) X 1000 meq/kg MWhere,m = weight of the sampleVo = volume of sodium thio sulphate blank readingV = volume of sodium thio sulphate for sample


Results

For palm oilPeroxide value = (v-v0) X 1000 meq/kg M = ( 10.30ml-0.00ml) 0.002 X 1000 meq/Kg

1.0120g= 20.355 X 1000

For soya oil

Peroxide value = (v-v0) X 1000 meq/kg M = ( 18.50ml-0.00ml) 0.002 X 1000 meq/Kg

1.0230g = = 36.17 X1000 Discussion

According to codex standards the values and determination method of some parameters are as below.

Parameter Determination Method ValueDetermination of iodine value Wijs - ISO 3961: 1996; or

AOAC 993.20; or AOCS Cd 1d-1992 (97); or NMKL 39(2003)

Palm oil 50-55

Palm kernel oil 14.1-21.0

Determination of peroxide value

According to AOCS Cd 8b-90 (03); or ISO 3960: 2001

Refined oils up to 10 milliequivalents of active oxygen/kg oil

Cold pressed and virgin oils

up to 15 milliequivalents of active oxygen/kg oil

Determination of acidity According to ISO 660: 1996, amended 2003; or AOCS Cd 3d-63 (03)

Refined oils 0.6 mg KOH/g Oil Cold pressed and virgin oils

4.0 mg KOH/g Oil

Virgin palm oils 10.0 mg KOH/g Oil

Determination of relative density

According to IUPAC 2.101, with the appropriate conversion factor.

Palm oil 0.891-0.899 (500C)

Palm kernel oil 0.

Determination of saponification value

According to ISO 3657: 2002; or AOCS Cd 3-25 (03)

Palm oil 190-290 mg KOH/g oil

Palm kernel oil 230-254mg KOH/g oil


Below are some important definitions given on codex standards.

Edible vegetable oils are foodstuffs which are composed primarily of glycerides of fatty acids being obtained only from vegetable sources. They may contain small amounts of other lipids such as phosphatides, of unsaponifiable constituents and of free fatty acids naturally present in the fat or oil. Virgin oils are obtained, without altering the nature of the oil, by mechanical procedures, e.g. expelling or pressing, and the application of heat only. They may have been purified by washing with water, settling, filtering and centrifuging only. Cold pressed oils are obtained, without altering the oil, by mechanical procedures only, e.g. expelling or pressing, without the application of heat. They may have been purified by washing with water, settling, filtering and centrifuging only.

**The slight higher value for specific gravity in our result must be due to temperature difference. Since we have conducted this in room temperature at about 30oC. The codex value is given in 50 oC.

Palm oil is derived from the fleshy mesocarp of the fruit of the oil palm (Elaeis guineensis).

Palm oil is naturally reddish because it contains a high amount of beta-carotene (though boiling palm oil destroys the beta-carotene, rendering the oil colourless). Palm oil is one of the few vegetable oils relatively high in saturated fats (like palm kernel oil and coconut oil). It is thus semi-solid at typical temperate climate room temperatures, though it will more often appear as liquid in warmer countries.

Palm oil contains several saturated and unsaturated fats in the forms of lauric (0.1%, saturated), myristic (0.1%, saturated), palmitic (44%, saturated), stearic (5%, saturated), oleic (39%, monounsaturated), linoleic (10%, polyunsaturated), and linolenic (0.3%, polyunsaturated) acids. Like any vegetable oils, palm oil is designated as cholesterol-free, though saturated fat intake increases both LDL and HDL cholesterol.

Palm oil is a very common cooking ingredient in southeast Asia and the tropical belt of Africa. Its increasing use in the commercial food industry in other parts of the world is buoyed by its cheaper pricing and the high oxidative stability of the refined product

Palm oil contains more saturated fats than some other vegetable oils. The palm fruit yields two distinct oils - palm oil and palm kernel oil.


Fatty acid content of palm oil


Type of fatty acid

pct

Palmitic C16 44.3%

Stearic C18 4.6%

Myristic C14 1.0%

Oleic C18 38.7%

Linoleic C18 10.5%

Other/Unknown 0.9%

green: Saturated; blue: Mono unsaturated; orange: Poly unsaturated

Fatty acid content of palm kernel oil

Type of fatty acid

pct

Lauric C12 48.2%

Myristic C14 16.2%

Palmitic C16 8.4%

Capric C10 3.4%

Caprylic C8 3.3%

Stearic C18 2.5%

Oleic C18 15.3%

Linoleic C18 2.3%

Other/Unknown 0.4%

green: Saturated; blue: Mono unsaturated; orange: Poly unsaturated

Reference

1. CODEX STANDARD FOR NAMED VEGETABLE OILS CODEX STAN 210-19992. wikepedia

3. H.-D. Belitz · W. Grosch · P. Schieberle, Food Chemistry 4th revised and extended ed.


Lipid Characteristic Lak

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