Oil and Fat Analysis

OIL AND FAT ANALYSIS NOORHIDAYAH ISHAK

Oil and Fat Analysis Analysis •

Why oil and fat products need to be analyze before it been distribute to the consumer? –

To ensure the quality control in the process

–

To determine the cause of product failures

–

To ensure products function and design

Oil and Fat Analysis Analysis 8 types of oil and fat analysis: 

Non fatty impurities



Melting, solidification and consistency



Composition analysis



Flavorr, randicity Flavo randicity and stability stability



Color and appearance



Refining and bleaching



Performance testing



Nonsta Non stand ndard ardize ized d met method hodss

on a y mpur

es Non fatty impuritie s

Impuritie s analysis

Insoluble

Filterable Hot plate

Soap analysis

Moisture analysis

Trace material analysis

Turbidimeter

Air oven

Karl Fisher

Vacuum oven

Non fatty impurities (Moisture analysis)



Hot plate method

- 10 g sample heated in beaker with gentle agitation on hot plate until smoking begins 

Moisture and volatile matter = The loss in weight between the beginning and the ending sample

Non fatty impurities (Moisture analysis)  Air

oven method



accurate, more reliable than hot plate



time consuming  approximately

5 grams of a representative sample is weighed into a dried,

 tared

moisture dish and dried in the oven for 30 minutes at 101°C (± 1°C). This

 procedure

is repeated until a constant weight is determined

 The

loss in weight is calculated as the moisture and volatile matter




Vacuum oven method

-similar to air oven method except -vacuum method no to exceed 100 mm of Hg at temperature 20 – 25 deg above b.p of water at the operating pressure until constant weight is obtained in successive 1h drying periods.




Karl Fischer method

-Karl Fischer is an analytical technique used to determine moisture

Non fatty impurities (Moisture analysis) 

Karl Fischer method

The titration endpoint is a color change from yellow to brown. brown.

on a y mpur



Insoluble


Soap analysis

Moisture analysis


Turbidimeter

Air oven

Karl Fisher

Vacuum oven

Non fatty impurities (Impurities analysis) 

Foreign material in incoming crude edible oils must be removed to produce an acceptable finished product



Methods to remove impurities: 

insoluble impurities



filterable impurities



turbidimeter impurities

Non fatty impurities (Impurities analysis) Insoluble impurities - Dirt, seed fragments and etc insoluble in kerosene or petroleum ether Utilizes the residue from the moisture and volatile matter •

•

-After wash with warm kerosene, the crucible is dried and weighed


Filterable impurities evaluation method

-During processing, undissolved impurities might be present such as salt which formed after the reaction -Methods: filter a standard quantity (500 g) of heated (70 – 90 deg.) oil sample with vacuum suction funnel through Whatman No. 2 filter disc.

Non fatty impurities (Impurities analysis)



Turbidimeter impurities

-Amount of undissolved impurities in oil can be determined using this method -method: sample will be poured into prescribed sample bottle to eliminate air bubbles. Then the sample will be heated to 70oC and allowed to stand at 5 – 10 mins in controlled temp. oven


Turbidimeter impurities cont.

-The turbidimeter readings can be converted to ppm of impurities using a calibration curve 

No suitable for meat fats and products containing emulsifiers – contain impurities that cannot be effectively measured by this method

on a y mpur



Insoluble


Soap analysis

Moisture analysis


Turbidimeter

Air oven

Karl Fisher

Vacuum oven




Metals in oils and fats can cause the deterioration of the product quality



Metals usually present in edible oils and fats through the processing level



Most prevalent metals found: copper, iron, calcium, magnesium, sodium, lead, zinc, and nickel



Can be trace by analysis using ICP (Plasma emission spectroscopy

on a y mpur



Insoluble


Soap analysis

Moisture analysis


Turbidimeter

Air oven

Karl Fisher

Vacuum oven

Soap analysis 

In caustic refining, NaOH is added into the oil to react with free fatty acid and produce soaps



Traces of soap in oil after refining and bleaching could poison hydrogenation catalyst.



2 methods available for determining soaps:

-

Conductivity procedure (Cc 15-60)

-

Titration procedure (Cc 17-79)

Oil and Fat Analysis 8 types of oil and fat analysis: 










Flavor, rancidity and stability









Performance testing



Nonstandardized methods

Melting, solidification and consistency 

Most frequently and routinely analysis performed



Helps with quality control and product development – good indications of the mouth feel, overall general behaviour at cool, ambient and elevated temperature

Melting point analysis 

Natural fats do not have true melting points



Melting range or melting interval is most appropriate terms



Several melting point procedures have been standardized by AOCS

Melting point analysis

Melting Point Analysis

Capillary melting point

Wiley melting point

Mettler dripping point



-

Similar with procedure used to determine the melting point of pure organic compound

-

Heated until the fat become clear



Wiley melting point



Wiley melting point:

-A tube of 3.5 cm internal diameter is half-filled with boiled water then cautiously topped –off with boiled alcohol so that the latter remains above the water which it forms an interface. -A cold disc of fat added to the tube and when disc softens to become spherical globule –melting point


Wiley melting point cont:

-

Disadvantages:

-

-> subjective interpretation in order to determine end point

-

-> Constant attention needed to determine the endpoint



Wiley melting point


Melting point analysis  Dripping

point

-use METLLER TOLEDO instrument -Method: 17 drops of melted fats will be put in the sample cup -Put in a freezer for 15 mins -Cold solidified sample warm through the furnace until it becomes fluid enough to flow -When the sample flow, it trip a photoelectric circuit that records the temperature on digital read out.

Melting point analysis •

Dripping point

Melting point analysis



Advantaged of Dripping point 

had become a standard in most fats and oil laboratory



fast, reliable result



good correlation with Wiley result



ability to analyse products with low melting points

Solidification Analysis 

Solidification of mixed fatty acids: point where a balance is attained between the heat generated and heat lost, which will vary according to rate of crystallization.



Types of evaluation:

Solidification Analysis

Titer test

Cloud point

Cold test




Titer test: measure the solidification point of fatty acid

-

For edible oils and fats, commonly specified for low iodine values hard fat refers to as titer stocks



For inedible fats, used for soap making or as a raw material for fatty acid manufacture


Titer test

Cloud point

Cold test




Cold test: the ability of an oil to resist crystallization by determining the time (in hours) required for the oil to become cloudy at 0°C (32°F).



Method: dry filtered oil is placed in a sealed 4-ounce bottle and submerge into an ice bath.

If the oil remains clear for 5.5 h, the oil pass the cold test.


Titer test

Cloud point

Cold test

Solidification Analysis •

•

Cloud point: is obtained by stirring a sample of fat while it is being cooled until the oil has clouded enough to block a light beam of known intensity. The cloud or congeal point values are more closely related to consistency than melting points

Consistency Analysis 

Consistency: impression of resistance



Plasticity: relates to the capacity of the product to be molded



Fat become firmer as the solid content increases



Butter and margarine depends upon the consistency of fat portion and its ability to spread on bread

Consistency Analysis  Consistency

evaluation method:

-consistency ratings -penetrations


Consistency rating:

-pressing a finger into the product/ squeeze the product in the hand -Still applicable and effective -required an experienced evaluator


Penetration

-

Widely used method to measure the consistency of plasticized shortening or margarine

-

Using grease penetrometer

-

Measured at different temp. to determine the plastic range of the sample

-

Perfect plastic range: penetration at all temp

same




















Performance testing




Composition analysis 

Usually done by using wet chemical analysis (classical method)

Saponification value Iodine value refractive index


fatty acid composition calculated iodine value Emulsifier analysis

Tocopherol analysis Antioxidant analysis


Saponification value

-

Measure the alkali-reactive groups in fats and oils

-

Useful in predicting type of glycerides

-

Glyceride with short-chain fatty acid have higher saponification values than long-chain fatty acid

-

Example: vegetable oils and animal fats has same range of saponification value: 180 - 200

Saponification Value Saponification - hydrolysis of ester under alkaline condition. O H2 C

O

HC H2 C

C O

R

O

C O

R

O

C

R

H2 C

OH O

+

3 KOH

HC

OH

H2 C

OH

+

3R

C

OK


Iodine value

-

Measure the unsaturation of fatty acid

-

But, cannot define specific fatty acid



Refractive index

-measure the change in unsaturation as the fat or oil is hydrogenated -A refractometer with temperature control at 25 deg. is used -A refractive index decrease with no. of double bonds present in fatty acids

Differential between saturate and unsaturated fatty acid Saturate

Unsaturated

Fatty acid chain are straight

Fatty acid chain are bent in some place

No double bond

Contain double bond

Solid in room temperature

Liquid in room temperature

Palmitic fatty acid

Oleic fatty acid

Butter, palm nut oils, coconut

Olive oil, fish oils, peanut, linseed, and cottonseed oils


Fatty acid composition

-

Determined by using GC



Calculated iodine value

-

Measure the unsaturation in fatty acid

-

Calculated from fatty acid composition analysis


Triglyceride structure 

HPLC procedures used to determine relative amounts of glycerides present in a fat

O

O H2C

OH

HC

OH

H2 C

OH

Glycerol

+

HO

C O

R

HO

C O

R

HO

C

R

3 Fatty Acids

H2 C

O

C O

R

HC

O

C R O

H2 C

O

C

R

+ 3 H2O


Antioxidant analysis

-To measure the amount of synthetic antioxidant used in fat and oil products -Ensure the amount of synthetic antioxidant is beyond the safety limit (e.g: US FDA allow max. limit of 100 ppm for meat products) -Use GC or HPLC for analysis


Tocopherol analysis 

Vegetable oils contain tocopherols, which are natural antioxidants that retard oxidative rancidity.



The instrumentation and procedures evaluated have involved colorimeters, paper chromatography (PC), TLC, column chromatography (CC), GLC, GLC/mass spectrometry (GLC/MS), and HPLC separation techniques




















Performance testing




Flavor, rancidity and stability 

Customer use organoleptic evaluations to judge the quality of fat and oil



Organoleptic: 

evaluation of oil products has long been recognized as the most sensitive method of assessing quality, but it is also recognized that these evaluations generally lack precision and reproducibility

avor, ranc 

Flavor analysis method

-

Sensory evaluations

-

Volatile flavor analysis

y an s a

y

Flavor analysis method 

Sensory evaluations

-most common method of grading finished oil quality -Experienced taster/ flavorist rate the flavor of the oil according to established intensity scale. -time consuming, expensive

avor ana ys s me o 

Volatile flavor analysis

-

Use GC analysis

-

E.g:

Besides lactic acid, acetaldehyde, acetone, and 2-butanone contribute most to the typical aroma and flavor of yogurt. Extended storage of yogurt causes off-flavor development, which is mainly attributed to the production of undesired aldehydes and fatty acids during lipid oxidation

Rancidity analysis 

The major cause of rancidification of oil and fats are:

1)

Oxidation

2)

Hydrolysis



Factors that contribute to the rancifidication and formation of off-flavors:

1)

Temperature

2)

Light

3)

Moisture

4)

Metals

5)

Oxygen

Rancidity The sharp pungent odours mixed with stale and musty odours (unpleasant smell) 

Hydrolytic Rancidity .

Hydrolytic rancidity results in the formation of free fatty acids and soaps (salts of free fatty acids) and is caused by either the reaction of lipid and water in the presence of a catalyst or by the action of lipase enzymes.



Oxidative Rancidity .

Oxidative rancidity results from more complex lipid oxidation processes which involve free radical reactions. The processes are generally considered to occur in three phases: 1) initiation or induction phase, 2) propagation phase, and 3) termination phase.

Rancidity 

Analysis to measure:

a)

Peroxide value

b)

Anisidine value

c)

Free fatty acid and acid value

Rancidity analysis 1.

Peroxide Value •

•

–

major cause by oxidation of lipid

Hydroperoxides formed by the reaction between oxygen and the unsaturated fatty acids are the primary products of this reaction. Hydroperoxides have no flavor or odour but break down rapidly to form aldehydes, which have a strong, disagreeable flavour and odour

Rancidity analysis 2. •

•

•

Anisidine value The anisidine value measures the amount of α and β unsaturated aldehyde present in the oil. The method is based on present of acetic acid, panisidine reacts with aldehydic compound in an oil, producing yellowish reaction products. The color intensity depend on the amount of aldehydic compound present.

3.

Acid Value •

•

The flavors resulting from FFA developed depend on composition of fat thus, rancidity analysis can be measure by FFA Number of mgs of KOH required to neutralize the Free Fatty Acids in 1 g of fat.

AV =

ml of KOH x N x 56 Weight of Sample

= mg of KOH

Oil and Fat Analysis

Recommend Documents