FOod analysis

1. Session 1:
1. Explain the roles of analytical chemistry in food science and
food technology.
2. Describe the reasons for determining composition and
characteristics of food.
Session 2:
1. Explain sampling procedure.
2. Explain factors affecting sampling.
3. Explain the risks associated with sampling.
Session 3:
1. Describe sample preparation.
2. Describe critical factors affecting sample quality during
preparation.
Session 4:
1. Describe the importance of analytical data evaluation.
2. Evaluate replicate analyses of the same sample for accuracy
and precision.
3. Determine the best line fits for standard curve data.
Session 5:
1. Explain about forms of water in foods.
2. Explain about water activity.
3. Name and describe methods to measure moisture/water
activity.
Session 6:
1. Describe the importance of ashing.
2. Recall the characteristics of various ashing procedures.
3. List the types of ashing equipment.
Session 7:
1. Describe the content of lipids in foods.
2. Describe solvent extraction methods.
3. Describe non-solvent wet extraction methods.

2. SESSION 1
1. Trends and demands of
Consumers:
● high quality, safe and nutritious foods
● Nutrition labelling is used as a guidance to choose food
● Health claim food preference
Food Industry:
● produce high quality food in order to meet consumer
demand (production - processing - kill pathogen - final
preparation & cooking)
Government Regulations:
● Nutrition labelling regulations
● Good manufacturing practice
● Hazard analysis and critical control point (HACCP
● Codex Alimentarius Commission (CAC)
● SNI – Badan Standardisasi Nasional
2. Reasons for analysing foods
Done by:
● Government Laboratory
● Food Manufacturers
● Ingredients Suppliers
● Analytical Laboratory Services
● University Research Laboratories
Government regulations
- maintain the quality
- ensure the food industry provides consumers with
wholesome and safe foods
- inform consumers about the nutritional composition of
foods
- enable fair competition amongst food companies
- eliminate economic fraud
a) Standards
● Standards of identity: type and amounts of ingredients that
certain foods must contain
● Standards of quality: to set minimum requirements on the
color, tenderness, mass and freedom from defects (e.g. canned
fruits)
● Standards of fill-of-container: how full a container must be to
avoid consumer deception
● Standards of grade (voluntary); A number of foods, including
meat, dairy products and eggs, are graded according to their
quality, e.g. from standard to excellent. For example meats can
be graded as “prime”, “choice”, “select”, “standard” etc.
b) Food inspection and grading
- Government's Food Inspection and Grading Service: routinely
analyses the properties of food products to ensure that they
meet the appropriate laws and regulations
- Hence, both government agencies and food manufacturers
need analytical techniques to provide the appropriate
information about food properties
Food safety
● Analyze foods to ensure that they are safe
● To know if a food manufacturer sold a product that was harmful
or toxic, e.g. allergens, pesticides residues, microbial
● Food manufacturers must ensure that these harmful
substances (harmful microorganisms {salmonella, etc.}, toxic
chemicals {herbicides, pesticides} or extraneous matter {glass,
wood, metal, insect}) are not present, or that they are effectively
eliminated before the food is consumed
Quality control
● Characterization of raw materials
● Monitoring of food properties during processing
● Characterization of final product
● Hazard Analysis and Critical Control Point (HACCP)

3. Characterization of raw material
- Coloration: the color of potato chips depends on the
concentration of reducing sugars in the potatoes that
they are manufactured from - the higher the
concentration, the browner the potato chip
(discoloration)
- On frying, the potatoes darken due to the reaction
between the reducing sugars and amino acids: Maillard
reaction.
- A reducing sugar is any sugar that is capable of acting as
a reducing agent because it has a free aldehyde group or
a free ketone group. All monosaccharides are reducing
sugars, along with some disaccharides, oligosaccharides,
and polysaccharides.
- Benedict’s Test: Benedict’s reagent BGYOR
Research and development
● Many scientists working in universities, government
research laboratories and large food companies carry out
basic research
● Scientists working for food companies or ingredient
suppliers usually carry out product development
3. Properties analyzed
a) Composition
Most foods are compositionally complex materials made up of a
wide variety of different chemical constituents specified
depending on the property:
• specific atoms (e.g., Carbon, Hydrogen, Oxygen, Nitrogen,
Sulfur, Sodium, etc.);
• specific molecules (e.g., water, sucrose, tristearin,
β-lactoglobulin),
• types of molecules (e.g., fats, proteins, carbohydrates, fiber,
minerals)
• specific substances (e.g., peas, flour, milk, peanuts, butter)
b) Structure
- Structural organization of the components within a food plays a
large role in determining the physicochemical properties, quality
attributes and sensory characteristics
- Hence, two foods that have the same composition can have very
different quality attributes if their constituents are organized
differently
- The structure of a food can be examined at a number of different
levels:
- Molecular structure ( 1 - 100 nm): overall physicochemical
properties depending on type of molecules present, their 3D
structure and their interactions with each other.
- Microscopic structure ( 10 nm - 100 mm): regions in a material
where the molecules associate to form discrete phases, e.g.,
emulsion droplets, fat crystals, protein aggregates and small air
cells.
- Macroscopic structure ( > 100 mm): structure that can be
observed by the unaided human eye, e.g. sugar granules, large
air cells, raisons, chocolate chips.
c) Physicochemical properties
The physicochemical properties of foods are used to determine their
perceived quality, sensory attributes and behavior during
production, storage and consumption.
Optical properties
● The optical properties of foods are determined by the way that they
interact with electromagnetic radiation in the visible region of the
spectrum, e.g., absorption, scattering, transmission and reflection
of light.
● For example, full fat milk has a “whiter” appearance than skim milk
because a greater fraction of the light incident upon the surface of
full fat milk is scattered due to the presence of the fat droplets

4. Rheological properties
● Study of the flow and deformation of the materials in response
to some applied force.
d) Sensory attributes
● Ultimately, the quality and desirability of a food product is
determined by its interaction with the sensory organs of human
beings, e.g., vision, taste, smell, feel and hearing.
e) Stability properties
● a measure of its ability to resist changes in its properties over
time.
● changes may be:
- Chemical: chemical or biochemical reactions, e.g., fat
rancidity or non-enzymatic browning.
- Physical: changes in the spatial distribution of the molecules
present e.g., droplet creaming in milk.
- Biological: change in the number of microorganisms
present, e.g., bacterial or fungal growth.
4. Types of samples analyzed
Importance of chemical analysis of food:
- For quality assurance program
- Formulating and developing new products
- Evaluating new processes for making food products
- Identifying the source of problems with unacceptable
products
Samples to be analyzed:
● Raw materials
● Process control samples
● Finished product
● Competitor’s sample
● Complaint sample
5. Steps in analysis
1. Select and Prepare Sample
• Obtaining a representative sample and converting the sample to
a form than can be analyzed
• Example: To determine TAG composition in palm olein, you need
to dissolve the sample in acetone.
2. Perform the Assay
• Assay for each analysis for different components or characteristics
or specific type of product is unique.
• Example: Methods to determine fatty acid and amino acid are
different.
3. Calculate and Interpret the Results
• Important to make appropriate calculations to interpret the data
correctly.
• Example: Calculation of total protein. Choosing the right factor is
important.
6. Choice and validity of method

5. Summary
● Consumer, food industry, and government concern for food
quality and safety has increased the importance of analyses to
determine composition and critical product characteristics.
● Chemical and physical analyses are part of quality
management, product development, or research activities.
SESSION 2: SAMPLING PROCEDURES
Sample: small portions taken for analysis
Population: The entire lot or the entire production for a certain
period of time, in the case of continuous processes
Sampling: The process of taking samples from a population
Benefits of sampling:
● A quality estimate can be obtained accurately, quickly, less
expense and timesaving.
● Food products: analyzing a whole population would be
practically impossible because of the destructive nature of most
analytical methods.
Selection of sampling procedures
1. Define the target population
2. Determine the sampling frame
3. Select a sampling technique
4. Determine the sample size
5. Conduct the sampling process
Nature of the population
It is extremely important to clearly define the nature of the population
from which samples are to be selected.
● A population may be either finite or infinite.
● A population may be either continuous or compartmentalized.
● A population may be either homogeneous or heterogeneous.
1. Selection of sampling procedures
•Once sampling is conducted, a series of stepwise procedures – from
sample preparation, laboratory analysis, data processing, and
interpretation – is needed to obtain data from the samples.
The final result depends on the cumulative errors, described as
variance (estimate of the uncertainty).
• The total variance of the whole testing procedures (sum of variance)
represents
the precision of the process.
• Precision is a measure of the reproducibility of the data.
• In contrast, accuracy is a measure of how close the data are to the
true value.
Sampling plan
● Most sampling is done for a specific purpose, and the purpose
may dictate the nature of the sampling approach.
● Two primary objectives of sampling:
○ To estimate the average value of a characteristic.
○ To determine if the average value meets the
specifications defined in the sampling plan.

6. 1.1 Nature of the population
● A population may be either finite or infinite
○ Finite → if it is possible to count its individuals (countable)
■ has a definite size
■ E.g. the books in a library
○ Infinite → cannot be calculated easily (uncountable)
■ E.g. the number of germs in patient’s body
● A population may be either continuous or compartmentalised
○ Continuous → there is no physical separation between the different parts of the
sample
■ E.g. liquid milk or oil stored in a tanker.
○ Compartmentalised → split into a number of separate sub-units, e.g.,
■ E.g. boxes of potato chips in a truck, or bottles of tomato ketchup moving
along a conveyor belt
● A population may be either homogeneous or heterogeneous
○ Homogeneous → the properties of the individual samples are the same at every
location within the material
■ E.g. a tanker of well stirred liquid oil
○ Heterogenous → the properties of the individual samples vary with location
■ E.g. a truck full of potatoes, some of which are bad
1.2 Sampling Plan
● Most sampling is done for a specific purpose, and the purpose may dictate the nature of
the sampling approach.
● Two primary objectives of sampling
○ To estimate the average value of a characteristic.
○ To determine if the average value meets the specifications defined in the
sampling plan
● Sampling purposes vary widely among different food industries:

7. ● Sampling purposes vary widely among different food industries:
○ Nutritional labeling
○ Detection of contaminants and foreign matter
○ Statistical process control (Quality Assurance)
○ Acceptance sampling (raw materials, ingredients or products)
○ Release of lots of finished products
○ Detection of adulterations
○ Microbiological safety
○ Authenticity of food ingredients
● A sampling plan should be a well-organized document that
establishes the goals of the sampling, factors to be measured,
sampling point, sampling procedure, frequency, size, personnel,
preservation of samples, etc.
● Some of the features that are commonly specified in the
sampling plan: sample size, sample location, and sample
collection.
Factors affecting the choice of sampling plans
Sampling by attributes and sampling by variables
Sampling plans are designed for examination of either attributes
or variables.
● Attribute sampling: to decide the acceptability of a population
based on whether the sample possesses a certain characteristic
or not, e.g. evaluation of bacterial contamination.
● Variable sampling: to estimate quantitatively the amount of
substance (protein content, moisture content, etc.) or
characteristic (color, texture, etc.) on a continuous scale. Usually
produces data that have a normal distribution.
● Acceptance sampling: to accept or reject a product based on a
random sample of the product. Acceptance sampling plans do
not improve product’s or process’ quality.
Before sampling,
specify the plan (n, a) given N
N, population (or lot) size
n, sample size
a, acceptance numbers
d, number of defective items
Risks associated with sampling
● Consumer’s risk
○ the probability of accepting a poor quality of population
○ poor quality should happen rarely (<5% of the lots).
○ actual acceptable probability (β) of a consumer risk
depends on the consequences associated with accepting
an unacceptable lot
● Producer’s risk
○ the probability of rejecting (α) an acceptable product.
○ acceptable probability of producer’s risk is usually 5-10%
Operating characteristic curve

8. Sampling procedures
● There are many sampling procedures that have been developed
to ensure that a sample adequately represents the target
population.
● Two standard categories of the sampling method exist. These
two categories are called probability sampling and
nonprobability sampling.
Probability sampling
● Probability sampling prescribe the selection of a sample from a
population based on chance.
● Thus, every member of the population will have a known,
nonzero probability of being selected.
● It provides a statistical basis for obtaining representative
samples with elimination of human bias.
● Sampling error can be calculated.
Simple
random
sampling
● no of units in the population is known, each unit
is assigned an identification number
● a certain number of identification numbers are
selected according to the sample size.
● sample size is determined according to the lot
size and potential impact of a consumer or
vendor error.
● Random selection of the individual units done
by using random number tables or
computer-generated random numbers.
● Units selected are analysed, results considered
as an unbiased estimate of the population.
Systematic
sampling
● used when a complete list of sample units is not
available, but when samples are distributed
evenly over time or space, such as on a
production line. (e.g. take from line every 30 mins)
● First unit is selected at random (random start)
and then units are taken every nth unit
(sampling interval) after that.
Stratified
sampling
● Dividing the population (size N) into a certain
number of mutually exclusive homogeneous
subgroups (size N1, N2, N3, etc.) and then
applying random or another sampling
technique to each subgroup.
● Used when subpopulations of similar
characteristics can be observed within the whole
population.
Cluster
sampling
● Population divided into subgroups/clusters, a
certain number of clusters selected randomly
only for analysis.
● Sampling may be either totally inspected or
subsampled for analysis.
● More efficient & less expensive than simple
random sampling, since populations divided into
clusters
Composite
sampling
● To obtain samples from bagged products such
as flour, seeds, butter and larger items in bulk.
● Small aliquots are taken from different bags, or
containers, and combined in a simple sample
(the composite sample) that is used for analysis.
Non-probability sampling
● Randomization is always desired but not always feasible, or even
practical, to take samples based on probability methods.

9. ● Units of the sample are chosen on the basis of personal
judgement or convenience.
● Probability of selecting any particular member is unknown.
Judgement
sampling
● Solely at the discretion of the sampler and
therefore is highly dependent on the person
taking the sample.
● Used when it is the only practical way of
obtaining the sample.
● may result in a better estimate of the
population than random sampling if sampling
is done by an experienced individual and the
limitations of extrapolation from the results
are understood.
Convenience
sampling
● Performed when ease of sampling is the key
factor
● Requires little effort, the sample obtained will
not be representative of the population
Restricted
sampling
● May be unavoidable when the entire
population is not accessible
● Sample will not be representative of the
population
Quota
sampling
● Division of a lot into groups representing
various categories, samples are then taken
from each group.
● Less expensive than random sampling but less
reliable.
Problems in sampling
● Sampling bias → due to non-statistically viable convenience,
may compromise reliability
● Not understanding the population distribution
● Sample storage → sample degradation
● Mislabeling of samples → causes mistaken sample identification
Summary
• Sampling is a vital process, as it is often the most variable step
in the entire analytical procedure.
• The selection of the sampling procedure is determined by the
purpose of inspection, the food product, the test method, and
the characteristics of the population.
SESSION 3 - SAMPLE PREPARATION
1. General size reduction considerations
● Sample particle size or mass is too large for analysis
● Solid sample = grinding and cutting.
○ Sample can be spread on a clean surface and divided into
quarters.
○ The two opposite quarters are combined.
○ If mass is still too large for analysis, the process is
repeated until an appropriate amount is obtained.
● Liquid sample = emulsification or atomization.
● AOAC International provides details on the preparation of
specific food samples for analysis, which depends on the nature
of the food and the analysis to be performed.
● Solids: grind, if necessary, and mix to uniformity. Thoroughly mix
raw sugars with spatula in minimum time (rapidly). Break up
any lumps either on a glass plate with a glass or iron rolling pin,
or in a large, clean, dry mortar pestle.
● Semisolids: weigh 50 g sample, dissolve crystals of sugar in
minimum volume of H2O, wash into 250mL volumetric flask,
dilute to volume and mix thoroughly; or weigh 50g sample and
dilute with H2O to 100g. If insoluble material remains, mix
uniformly by shaking before taking aliquots or weighed
portions for determinations.
● Liquid: mix materials thoroughly. If crystals of sugar are present,
dissolve them by heating gently (avoiding loss of H2O by
evaporation). Or by weighing whole mass then adding H2O
heating until completely dissolved, and after cooling,

10. reweighing. Calculate all results to weight the original
substance.
2. Grinding and cutting
● Grinding and cutting reduce the size of solid materials by
mechanical action, dividing them into smaller particles
● To achieve sample homogenization.
Grinding
● crush or break (something) into very small pieces by rubbing it
against a rough surface or using a special machine.
● important for sample preparation prior to analysis and for food
ingredient processing.
● Some foods are more easily ground after drying.
● Grinding wet samples may cause significant losses of moisture.
● The grinding process should not heat the sample, and therefore
the grinder should not be overloaded → heat will be produced
through friction.
● Grind frozen foods reduce the likelihood of undesirable
heat-initiated chemical reactions during milling.
● Preferred to conduct sample prep for proximate analysis
Cutting
● To open, incise, or wound in (something) with a sharp-edged
tool or object (e.g. knife).
● A dull knife can cause unnecessary and unwanted damage.
Determination of particle size
● Particle size is controlled in certain mills by adjusting the
distance between burrs or blades or by screen mesh
size/number
● Mesh number is the number of square screen openings per
linear inch of mesh.
● Final particle for dried foods should be 20 mesh for moisture,
total protein, or mineral determination.
● Particle size is often related to product quality.
Methods:
➢ Stacked sieves
➢ Surface area and zeta potential (electrical charge on a particle)
○ Zeta potential is measured by an electroacoustic method
whereby particles are oscillated in a high frequency
electrical field and generate a sound wave whose
amplitude is proportional to the zeta potential.
➢ Optical and electron microscope
➢ Dynamic light scattering
3. Enzymatic inactivation
● Food materials often contain enzymes that may degrade the
food components being analysed.
● Enzyme activity must be eliminated or controlled.
● Heat denaturation and freezer storage (-20oC to -30oC) are
common methods.
● Some enzymes are more effectively controlled by changing pH,
or by salting out.
● Oxidative enzymes may be controlled by adding reducing
agents.
4. Lipid oxidation protection
● High-fat foods are difficult to grind (may need to grind frozen)
● Unsaturated lipids are sensitive to oxidative degradation and
should be protected by storing under nitrogen or vacuum.
● Antioxidants may stabilise lipids.
● Phototoxidation of unsaturated lipids should be avoided.
● Ideally, unsaturated lipids should be extracted prior to analysis.
● Low-temperature storage is generally recommended to protect
most foods.
5. Microbial growth and contamination
● Microorganisms are present in almost all foods and can alter the
sample composition.

11. ● Freezing, drying, and chemical preservatives are effective
controls. • Preservation methods used are determined by the
probability of contamination, storage conditions, storage time,
and analysis to be performed.
SESSION 4: STATISTICS
1. Central Tendency Measurement:
● Do replicates to increase accuracy and precision
● Mean: to expect the value closest to the true value
● Can also use median
2. Reliability of Analysis
● Accuracy: how close a particular measure is to the true value.
○ determining accuracy problem: most of the time we are
not sure what the true value is.
● Precision: how reproducible or how close replicate
measurements become.
○ Repetitive testing yields similar results = good precision
○ Evaluating precision:
■ Range: difference between the largest and
smallest observation
■ Standard deviation: spread of the experimental
values
Sources of error:
● Systematic error (determinate): e.g. a pipette that consistently
delivers the wrong volume of reagent will produce a high
degree of precision yet inaccurate results
● Random error (indeterminate): These errors fluctuate in a
random fashion and are essentially unavoidable For example :
reading an analytical balance, judging the endpoint change in a
titration, and using a pipette all contribute to random error
● Gross error (blunder): wrong reagent or wrong instrument
Specificity of a particular analytical method: detects only the
component of interest
Sensitivity: magnitude of change of an instrument with changes in
compound concentration. E.g.: differentiate between 0.0010 vs 0.0011
Limit of detection: lowest possible increment that we can detect with
some degree of confidence (or statistical significance).
3. Curve Fitting: Regression Analysis
● Curve fitting: generic term to describe the relationship and
evaluation between two variables.
● Standard curve or calibration curve: to determine unknown
concentrations based on a method that gives some type of
measurable response that is proportional to a known amount of
standard.
4. Reporting results
● Significant figures: some judgement of the number of
reportable digits in a result, to give an indication of the
sensitivity and reliability of the analytical method.
● Rejecting data
○ Q-Test:

12. Summary
• It is important to determine a mean, standard deviation, and CV
when evaluating replicate analyses of an individual sample.
• In evaluating linear standard curves, best line fits should always be
determined along with the indicators of the degree of linearity
(correlation coefficient or coefficient of determination).
SESSION 5 - MOISTURE ANALYSIS
Total solids: dry matter that remains after moisture removal
1. Importance of moisture assay
- Moisture is used as a quality factor.
● Preservation and stability
○ Dehydrated vegetables and fruits
○ Dried milks
○ Powdered eggs, etc.
● Prevent sugar crystallisation
○ Jams and jellies
- Reduced moisture for convenience in packaging or shipping.
○ Concentrated milks
○ Liquid cane sugar (67% solids), etc.
- Moisture (or solids) content is often specified in compositional
standards (i.e., Standards of Identity).
● a. Cheddar cheese must be ≤ 39% moisture.
● b. Enriched flour must be ≤ 39% moisture.
- Computations of the nutritional value of foods require
moisture content.
- Moisture data used to express results of other analytical
determinations on a uniform basis (i.e., dry weight basis).
2. Moisture content of foods
3. Forms of water in foods
● Free water: retains its physical properties and thus acts
as the dispersing agent for colloids and the solvent for
salts.
● Adsorbed water: held tightly or is occluded in cell walls
or protoplasm and is held tightly to proteins.
● Water of hydration (entrapped water): bound
chemically, for example, lactose monohydrate.
Sample collection and handling
• the greatest potential source of any error in any analysis.
• Precautions must be taken to minimise inadvertent moisture
losses or gains that occur during these steps.
• Any exposure of a sample to the open atmosphere should be
as short as possible.
• Any heating of a sample by friction during grinding should be
Minimised.
4. Methods used to measure moisture
● Direct & Indirect

13. Calculation
Removal of moisture
● Any oven method used to evaporate moisture foundation:
boiling point of water is 100◦C; However, this considers only pure
water at sea level.
● Free water is the easiest of the three forms of water to remove.
● However, if 1 molecular weight (1 mol) of a solute is dissolved in
1.0 L of water, the boiling point would be raised by 0.512˚C. This
boiling point elevation continues throughout the moisture
removal process as more and more concentration occurs.
● Moisture removal is sometimes best achieved in a two-stage
process.
● Liquid products (e.g. juices, milk) are commonly pre-dried over a
steam bath before drying in an oven.
● Products such as bread and field-dried grain are often air dried,
then ground and oven dried.
● The moisture content is calculated from moisture loss at both
air and oven drying steps.
Factors influencing the rate and efficiency of moisture removal
● Particle size
● Particle size distribution
● Sample sizes
● Surface area during drying
Decomposition of other food component
● Moisture loss from a sample during analysis is a function of time and
temperature.
● Decomposition enters the picture when time is extended too much or
temperature is too high → should compromise
● major problem in physical process: all the moisture must be
separated without decomposing any of the constituents that could
release water.
● less serious problem, consistent error: loss of volatile constituents, such
as acetic, propionic, and butyric acids; and alcohols, esters, and
aldehydes among flavour compounds.
Temperature control
● Consider the temperature variation in three types of ovens:
Convection (atmospheric), Forced draft, Vacuum
● greatest temperature variation = convection oven. hot air slowly
circulates without the aid of a fan.
Direct:
Types of Ovens
Forced dried oven
● sample is rapidly weighed into a pre-dried moisture pan
covered and placed in the oven for an arbitrarily selected time if
no standardised method exists.
● Drying time period: 0.75–24 h
Vacuum oven
● drying under reduced pressure (25– 100 mm Hg), obtain more
complete removal of water and volatiles without decomposition
● 3–6-h drying time.
● need a dry air purge in addition to temperature and vacuum
controls to operate within method definition.
● Microwave oven
● Infrared drying → forced ventilation to remove moisture; drying
time 10 – 25 min.

14. ● Rapid moisture analyzer → Widely used (fast, accurate, and easy)
Other methods
Distillation procedure
● codistilling the moisture in a food sample with a high boiling
point solvent that is immiscible in water
● Principle: different liquids boil at different temperatures
● collecting the mixture that distils off
● measuring the volume of water
Chemical method → Karl Fischer titration (used for sample low in
moisture)
● Karl Fischer reagent: reacts quantitatively and selectively with
water, to measure moisture content.
● especially useful for foods with very low moisture content and
for hygroscopic foods that are difficult to dry using conventional
methods.
● Karl Fischer reagent consists of iodine, sulfur dioxide, a base and
a solvent, such as alcohol.
○ Coulometric titration:
■ Uses a coulometer to measure small amounts of
moisture as low as 0.1 microgram (µg) of water, normally
used for moisture content below 1%
■ reagent and solvent are combined in the titration cell.
When a sample is introduced into the titration cell and
dissolved, reagent is released by the induction of an
electrical current.
○ Volumetric titration:
■ moisture determination based on the amount, or
volume, of reagent used to convert the water.
■ samples dissolved in a solvent before the titration begins.
A reagent is added until the water is removed.
■ ideal when working with samples containing higher
levels of moisture (generally over 1% or 2%) but also when
samples may contain ketones and or aldehydes.
Physical method:
Hydrometer (gravity and density): determine specific gravity (the ratio
of a substance's weight to the weight of the same volume of water)
Refractometer (liquid moisture): measure the extent of light refraction
(as a part of a refractive index) of transparent substances
Indirect:
- NMR spectroscopy
- NIR absorption
- Infrared absorption
5. Water activity
● Water content alone is not a reliable indicator of food stability,
since foods with the same water content differ in their
perishability.
● Water in food which is not bound to food molecules can
support the growth of bacteria, yeasts and moulds (fungi).
● The term water activity (aw ) refers to this unbound water.
● Aw is a better indication for food perishability than is water
content.
• As a food analyst, you are given a sample of condensed soup to
analyze to determine if it is reduced to the correct concentration.

15. • By gravimetric means, you find that the concentration is 26.54%
solids. The company standard reads 28.63%.
• If the starting volume were 1000 gallons at 8.67% solids and the
weight is 8.5 pounds per gallon,
• How much more water must be removed?
Answer
• The weight of the soup initially is superfluous information.
• By condensing the soup to 26.54% solids from 8.67% solids, the volume
is reduced to 326.7 gal [(8.67%/26.54%) × 1000 gal].
• You need to reduce the volume further to obtain 28.63% solids
[(8.67%/28.63%) ×1000 gal] or 302.8 gal.
• The difference in the gallons obtained is 23.9 gal (326.7 gal − 302.8 gal),
or the volume of water that must be removed from the partially
condensed soup to comply with company standards.
SESSION 6: ASH ANALYSIS
Ash: inorganic residue remaining after either ignition or complete
oxidation of organic matter in a foodstuff.
Two major types of ashing:
Dry ashing, primarily for proximate composition
Wet ashing (oxidation), as a preparation for the analysis of certain
minerals
Dry Ashing
● utilises a muffle furnace capable of maintaining temperatures of
500- 600o
C.
● Water and volatiles vaporised, organic substances burned in the
presence of oxygen in air to CO2 and oxides of N2
● Most minerals are converted to oxides, sulfates, phosphates,
chlorides, and silicates.
● Elements such as Fe, Se, Pb, and Hg may partially volatilize
● ஃ, total ash content provides information on salt, minerals and
silica.
Wet Ashing
● oxidising organic substances by using acids and oxidising agents or
their combinations.
● Minerals are solubilized without volatilization (no heat).
● Wet ashing often uses a combination of acids and requires a
special perchloric acid hood if said acid is used.
1. Importance of ash in food analysis
● a part of proximate analysis for nutritional evaluation.
○ Proximate analysis:
● water (moisture), ash, fat, protein and fibre
● Grinding is the preferred sample prep
● Ashing is the first step in preparing a food sample for specific
elemental analysis (sample of some material analysed for its
elemental and sometimes isotopic composition)
2. Ash content in foods
3. Methods
● A 2-10 g sample generally is used for ash determination.
● Plant materials ( ≤15% moisture) generally dried prior grinding.

16. ● Animal products, syrups, and spices require treatments prior to
ashing because of high fat, moisture (spattering, swelling), or
high sugar content (foaming) that may result in loss of sample.
3.2. Wet ashing
● Wet ashing is primarily used in the preparation of samples for
subsequent analysis of specific elemental analysis.
● It breaks down and removes the organic matrix surrounding the
minerals so that they are left in an aqueous solution.
● A dried ground food sample is usually weighed into a flask
containing strong acids and oxidising agents (e.g., nitric,
perchloric* and/or sulfuric acids) and then heated.
● Heating is continued until the organic matter is completely
digested, leaving only the mineral oxides in solution.
● *extremely dangerous → has a tendency to explode
3.3. Microwave ashing
● Both wet ashing and dry ashing can be done using microwave
○ Microwave wet ashing (Closed or open-vessel microwave
digestion systems)
○ Microwave dry ashing (Microwave muffle furnace)
● Microwave muffle furnaces can reach temperatures of up to
1200o
C.
4. Comparison of methods
● Dry ashing requires expensive equipment.
● Wet ashing requires a special hood (if perchloric acid is used),
corrosive reagents, and constant operator attention.
Practice problems
1. You wish to have at least 100 mg of ash from a cereal grain.
Assuming 2.5% ash on average, how many grams of the grain
should be weighed for ashing?
2. You wish to have a coefficient of variation (CV) below 5% with
your ash analyses. The following ash data are obtained: 2.15%,
2.12%, 2.07%. Are these data acceptable, and what is the CV?
Summary

17. ● Two major types of ashing, dry ashing and wet ashing, can be
done by conventional means or microwave system.
● Conventional dry ashing is based upon incineration at high
temperatures in a muffle furnace.
● Wet ashing (oxidation) often is used as a preparation for specific
elemental analysis by simultaneously dissolving minerals and
oxidising all organic material.
SESSION 7 - FAT
● Lipid can be defined as a fatty or waxy organic compound that,
in general, are soluble in ether, chloroform, or other organic
solvents but sparingly soluble in water.
● Still, there exists no clear scientific definition of lipid, primarily
due to the water solubility of certain molecules that fall within
one of the variable categories of food lipids.
● Other lipids, such as di- and monoacylglycerols, have both
hydrophobic and hydrophilic moieties in their molecules and
are soluble in relatively polar solvents.
● SCFA such as C1 – C4 are completely miscible in water and
insoluble in non-polar solvents.
● [formic acid (C1), acetic acid (C2), propionic acid (C3), butyric acid
(C4), isobutyric acid (C4), isovaleric acid (C5), hexanoic acid (C6)]
● Triacylglycerols are fats and oils that represent the most
prevalent category of the group of compounds known as lipids.
● The term lipids, fats, and oils are often used interchangeably.
● Fats generally refer to those lipids that are solid at room
temperature and oils generally refer to those lipids that are
liquid at room temperature.
2. General classification of lipids
1. Simple lipids
a. Fats
b. Waxes
2. Compound lipids
a. Phospholipids
b. Cerebrosides
c. Sphingolipids
● Derived lipids, such as fatty acids, long-chain alcohols, sterols,
fat soluble vitamins.
3. Content of lipids in food
Importance of Lipid Analysis
● Economic: not to give away expensive ingredients
● Legal: to conform to standards of identity and nutritional
labelling laws
● Health: development of low fat foods
● Quality: food properties depend on the total lipid content
● Processing: processing conditions depend on the total lipid
content
Some of the most important properties of concern to the food analyst
are:
1. Total lipid concentration.
2. Type of lipids present.
3. Physicochemical properties of lipids.
4. Structural organization of lipids within a food.
Sample selection and preparation
Depends on
1. Type of food – meat, milk, margarine

18. Session 7 - Lipid Analysis
Lipid: a fatty or waxy organic compound that generally are soluble in chloroform for other
organic solvents but sparingly soluble in water
Diacylglycerols and monoacylglycerols have both hydrophobic and hydrophilic moieties in
their molecules → soluble in a relatively polar solvents
Short chain fatty acids (SFCA) (C1-C4) are completely miscible in water and insoluble in
non-polar solvents
- C1: formic acid
- C2: acetic acid
- C3: propionic acid
- C4: butyric acid
- C5: isovaleric acid
- C6: hexanoic acid
Triacylglycerols: fats and oils that represent the most prevalent category of lipid
Fats: lipid that is solid at room temperature
Oils: lipid that is liquid at room temperature
Simple lipids Compound lipids Derived lipids
Fats Phospholipids Fatty acids
Waxes Cerebrosides Long chain alcohols
Sphingolipids Sterols
Fat soluble vitamins
Types of sterols:
- Cholesterol → animal
- Ergosterol → fungal
- Stigmasterol → plant
Importance of Lipid Analysis
- Economic → not to give away expensive ingredients
- Legal → conform to standards of identity and nutritional labeling law
- Health → development of low fat foods
- Quality → food properties depend on the total lipid content

19. 2. The nature of the lipid component – volatility, physical state
3. Type of analytical procedure used – solvent extraction, instrumental
Technique
4. Solvent extraction methods
• The fact that lipids are soluble in organic solvents, but insoluble in
water, provides a convenient method of separating the lipid
component in foods (from water soluble components, such as
proteins, carbohydrates and minerals).
• But, the wide range of relative hydrophobicity of different lipids
makes the selection of a single universal solvent impossible for lipid
extraction of foods.
• In addition, for nutrition labelling purposes, total fat is commonly
determined by gas chromatography.
Drying sample
- solvent cannot easily penetrate foods
containing water
- Drying at elevated temperatures is
undesirable → some lipids become
bound to proteins and carbohydrates
Particle size reduction – finely ground
(solvent can dissolve ez)
Acid hydrolysis – to release bound lipids
into easily extractable forms
Solvent selection – choose the best
solvent for the extraction
• Acid hydrolysis can break
both covalently and ionically
bound lipids into easily
extractable lipid forms
• The sample can be
predigested by refluxing for 1
h with 3N HCl.
• For example, the acid hydrolysis of two eggs requires 10 ml of HCl and
heating in a water bath at 65OC for 15 – 25 min or until the solution is
clear.
Digestion breaks down other components, not only lipids!
Solvent selection
● Solvent selection is important since a solvent that is too polar
will poorly extract non-polar lipids and will extract non-lipid
materials (i.e carbohydrates)
● Too non-polar will be inefficient for more polar lipids.
Ideal Solvent For Fat Extraction
Usually a combination of these 2 are used:

20. Batch Solvent Extraction
● Mixing sample with organic solvent in separating funnel
● Shake vigorously and allow the separation either by gravity or
centrifugation
● Aqueous phase is decanted off and the concentration of lipid in
the solvent is determined by evaporating off the solvent and
measure the mass lipid remaining
● Have to be repeated a few times
Semi-continuous solvent extraction
● Used to increase efficiency of lipid extraction from foods
● Common method: Soxhlet extraction
● Solvent extracts the lipids and carries them into the flask
● The lipids still remain in the solvent due to low volatility
Soxhlet programmable, set how long sample heated
Continuous solvent extraction
● Commonly used is Goldfish method
● Similar to soxhlet method except the extraction chamber is
designed.
● Solvent trickles through the sample rather than building up
around it
● Disadvantage: channelling of the solvent can occur
● i.e. solvent may take certain routes through the sample
Accelerated solvent extraction
● • By increase the temperature and pressure normally used
● • The effectiveness of the lipid extraction increases as its
temperature
● increases, but the pressure must also be increased to keep the
● solvent in the liquid state.
● • Advantage: reduce the amount of solvent
Non-solvent liquid extraction methods
A number of liquid extraction methods do not rely on organic solvents,
but use other chemicals to separate the lipids from the rest of the
food.

21. - Sulfuric acid + isomyl alcohol
- Isomyl alcohol prevents sugar charring
- Sugar charring could cause difficulty of fat content reading
- Slightly different shaped bottle
- Faster and simpler than Babcock method
Non-solvent extraction: Detergent method
- Overcome the inconvenience and safety concerns of sulfuric acid
- Uses a combination of surfactants
- Fat globule membrane is displaced by surfactants, causing the emulsion droplets to
coalesce and separate
- Amount of fat is read after centrifugation
Semi continuous solvent extraction
- Increase efficiency of lipid extraction from foods
- Solvent extracts the lipids and carries them into the flask
- Lipids still remain in the solvent due to low volatility
Semi continuous solvent extraction: Soxhlet
- Weigh pre dried sample into a pre dried extraction thimble
- Weigh pre dried boiling flask
- Put anhydrous ether (or petroleum ether) in the boiling flask
- Assemble boiling flask, Soxhlet flask, and condenser
- Extract in a Soxhlet extractor by heating the solvent in boiling flask
- 5 to 6 drops/second for condensation for 4 hrs, or
- 2 to 3 drops/second for condensation for 16 hrs
- Dry boiling flask with extracted fat by oven at 100℃ for 30 minutes
- Cool in desiccator
- Weigh
Continuous solvent extraction: Goldfish method → similar to Soxhlet
- Weigh pre dried porous ceramic extraction thimble
- Place vacuum oven dried sample in thimble, weigh
- Weigh pre dried extraction beaker
- Place ceramic extraction thimble into glass holding tube then up into condenser
- Place anhydrous ethyl ether (or petroleum ether) in extraction beaker
- Put beaker on heater
- Extract for 4 hours
- Lower the heater and let sample cool
- Remove the extraction beaker and let air dry overnight, then 100℃ for 30 minutes
- Cool in desiccator
- Weigh

22. Babcock Method
● H2SO4 is added to a known amount of milk in the Babcock
bottle.
● The sulfuric acid digests protein, generates heat, and releases
the fat.
● Centrifugation and hot water addition isolate fat for
quantification in the graduated portion of the test bottle.
● The fat is measured volumetrically, but the result is expressed as
percent fat by weight.
Gerber method
● Used mixture of sulfuric acid and isomyl alcohol and a slightly
different shaped bottle.
● Isomyl alcohol: prevent charring of the sugars by heat and
sulfuric acid
● Difficult to read the fat content from graduated flask
● Faster and simpler than the Babcock method.
Detergent Method
● Developed to overcome the inconvenience and safety concerns
associated with sulfuric acid.
● A sample is mixed with a combination of surfactants.
● Surfactants displace the fat globule membrane which
surrounds the emulsion droplets in milk and causes them to
coalesce and separate.
● Amount of fat is read after centrifugation.
6. Instrumental methods
There are a wide variety of different instrumental methods available
for determining the total lipid content of food materials.
These can be divided into three different categories according to their
physicochemical principles:
1. measurement of bulk physical properties
2. measurement of adsorption of radiation
3. measurement of scattering of radiation
6.1. measurement of bulk physical properties
● Density
● Electrical conductivity
● Ultrasonic velocity
6.2. measurement of adsorption of radiation
● Nuclear magnetic resonance
● Infrared (IR):
○ absorption of IR energy by fat = wavelength of 5.73 μm
○ more energy absorbed at 5.73 μm, higher fat content of the
sample.
● UV-visible
● X-ray absorption
Summary
● Lipids are generally defined by their solubility characteristics.
● Lipids in foods can be classified as simple, compound, or
derived lipids.
● The total lipid content of foods is commonly determined by
organic solvent extraction methods, which can be classified as
continuous (e.g., Goldfish), semicontinuous (e.g., Soxhlet),
discontinuous (e.g., Mojonnier, Folch).

23. Accelerated solvent extraction
- Increase the temperature and pressure
- Temp increase: Increase in lipid extraction effectiveness
Pressure increase: keep the sample liquid
- Advantage: reduce amount of solvent
Calculation:
Weight of fat in sample = (beaker + fat) − beaker
% Fat on dry weight basis
= (g of fat in sample/g of dried sample) × 100
Instrumental Methods
3 different categories according to their physicochemical principles:
- Measurement of bulk physical properties
- Density
- Electrical conductivity
- Ultrasonic velocity
- Measurement of adsorption of radiation
- UV-visible
- Infrared
- Wavelength 5.73 μm
- More energy = higher fat content
- Nuclear magnetic resonance
- X-ray absorption
- Measurement of scattering of radiation
- Light scattering
- Ultrasonic scattering
Summary
- Lipids are generally defined by their solubility characteristics.
- Lipids in foods can be classified as simple, compound, or derived lipids.
- The total lipid content of foods is commonly determined by organic solvent extraction
methods, which can be classified as continuous (e.g., Goldfish), semicontinuous (e.g.,
Soxhlet), discontinuous (e.g., Mojonnier, Folch).