Transcript Week 2-3 - Portal UniMAP

NUTRITION &
FOOD ANALYSIS
ERT 426 Food Engineering
Semester 1 Academic Session 2014/15
1
SUBTOPICS
1. Nutrition
1.1 Introduction
1.2 Nutrients
2. Food analysis
2.1 Introduction
2.2 Stages in food analysis
2.3Carbohydrate analysis
2.3.1 Introduction
2.3.2 Sample preparation
2.3.3 Methods of analysis
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SUBTOPICS
2.4 Protein analysis
2.4.1 Introduction
2.4.2 Methods of analysis
2.5 Fat analysis
2.5.1 Introduction
2.5.2 Sample preparation
2.5.3 Methods of analysis
2.6 New techniques for food analysis
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1. NUTRITION
1.1 Introduction
 Nutrition
– the science that studies food
and how food nourishes our bodies and
influences our health.
 Wellness
– A multidimensional lifelong
process that includes physical,
emotional and spiritual health.
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1.1 INTRODUCTION
Nutrition
is one of several factors
contributing to wellness.
Many factors contribute to an individual’s wellness.
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1.1 INTRODUCTION

Factors contribute to an individual’s wellness.



nutritious diet
regular physical activity.
The goals of a healthful diet are:


To prevent nutrient deficiency diseases (e.g.
scurvy, pellagra etc).
To lower the risk for chronic diseases (e.g.
diabetes, heart disease etc).
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1.2 NUTRIENTS
 Nutrients
– Chemicals found in foods
that are critical to human growth and
function.
 Six groups of nutrients found in the
foods we eat are:
Nutrients
that
provide
energy
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1.Carbohydrate
4. Vitamins
2. Fats & oils
3. Proteins
5. Minerals
6. Water
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1.2 NUTRIENTS
 Organic
 free
from non-natural fertilizers or chemicals.
 A substance or nutrient that contains the element
carbon (-C-).
 Scientists
described individual nutrients
as organic.
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1.2 NUTRIENTS
Carbohydrate
 Primary source of energy for body.
 Composed of carbon, hydrogen &
oxygen
Fats & Oils
 Important source of energy at rest
during low-intensity exercise.
 Composed of carbon, hydrogen &
oxygen.
 Food containing fats also provide
fat-soluble vitamins & essential
fatty acids.
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1.2 NUTRIENTS
Proteins
 Support tissue growth, repair &
maintenance.
 Composed of carbon, hydrogen
oxygen & nitrogen.
Water
 Inorganic nutrient that support all
body functions.
 For regulating nervous impulses,
muscle contractions, nutrient
transport, excretion of waste
products.
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1.2 NUTRIENTS
 Micronutrients
 needed
in relatively small amounts to support
normal health and body functions.
 Vitamins
 Organic
compounds that assist in regulating our
bodies processes.
 Vitamins assist in breaking down the
macronutrients for energy
 maintaining the health of body tissues, the
immune system & vision.
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1.2 NUTRIENTS

Vitamins
 do
not contain energy, but they are essential to
energy metabolism.

Metabolism –

A process by which large molecules (e.g.
carbohydrates, fats & proteins) are broken down
via chemical reactions into smaller molecules
that can be used as fuel, stored, or assembled
into new compounds the body needs.
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1.2 NUTRIENTS
 Overview
Type
of vitamins:
Distinguishing features
Fat soluble:
 A, D, E, K
 Soluble in fat
 Stored in the human body
 Toxicity can occur from consuming
excess amounts, which accumulate in
the body.
Water soluble:
 C, B (thiamin,
riboflamin, niacin,
B6, B12, pantothenic
acid, biotin &
folate)
 Soluble in water
 Not stored to any extent in the human
body
 Excess excreted in urine
 Toxicity generally only occurs as a result
of vitamin supplementation
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1.2 NUTRIENTS
 Minerals:
 inorganic
substances (NO carbon, -C-) that
maintain their structure throughout the processes
of digestion, absorption & metabolism.
 play critical roles in virtually all aspects of human
health & function.
 classified according to the amounts needed in diet
& the amount found in our bodies.
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1.2 NUTRIENTS
Type
Major minerals:
Calcium,
phosphorus,
sodium, potassium,
chloride,
magnesium, sulfur.
Trace minerals :
 Iron, zinc, copper,
manganese,
fluoride, chromium,
molybdenum,
selenium, iodine
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Distinguishing features
Needed in amounts >100mg/day in
our diets
Amount present in the human body
is > 5g (or 5,000 mg).
 Needed in amounts <100mg/day in
our diets
 Amount present in the human body
is < 5g (or 5,000 mg).
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2. FOOD ANALYSIS
2.1 Introduction

Food:
 maintenance
of normal health in adults
 supporting standard growth in children,
the nutritive quality of foods is an important
aspect in evaluating foods.
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2.1 INTRODUCTION
Growing knowledge of human nutrition and its
dissemination  demands have been made
by consumers for nutrient details to be
included on labels of marketed food products.
 Any nutritional claims made on the label need
to be substantiated by data on nutrient
content.

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2.1 INTRODUCTION

Nutritive quality:
 Nutrients : differ in their stability; processing and
storage conditions (consumer requires nutritional
information about the final ready to-eat food
product).
 measurement
of the nutritive quality of foods in all these
aspects have been developed.
 Proteins
 calorigenic
components
 Vitamins
 minerals.
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2.1 INTRODUCTION
 The Association of Official Analytical Chemists
(AOAC):
 Developed
standard specifications for food
commodities and manufactured products
 Methods for evaluating food samples to enable
comparison with such standards.
 These methods, now accepted as official or
standard, may be categorized as physical
instrumental, chemical, nutritional,
microbiological and sensory analytical methods.
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2.1 INTRODUCTION
 In general, stages that may be required in the
analysis of foods are:
1. Setting the protocol.
2. Sampling the food.
3. Preparing the sample in readiness for analysis,
including standardisation.
4. Analyse the sample.
5. Identification and/or quantification of the
sample.
6. Recording the information.
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2.2 STAGES IN FOOD ANALYSIS
1. Protocol.
 clearly defined protocol and to adhere to it. Thus



analysis can be reported unambiguously
verified by the analyst
reproduced for verification by other analysts.
2. Sampling.
 Process of preparing a representative portion of the
whole food for analysis.
 If quantitative results are required, an internal
standard may be added to allow any subsequent
losses to be compensated for during the analysis.
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2.2 STAGES IN FOOD ANALYSIS
3. Analyze the sample:
 A food analyst often has a large number of
different analytical procedures.
 Selection of the most suitable = the key to the
success of an analysis.
 Important factors that should be considered are
as follows:
i) Precision.
 A measure of the ability to reproduce an
answer between determinations performed by
the same scientist (or group of scientists)
using the same equipment and experimental
approach.
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2.2 STAGES IN FOOD ANALYSIS
ii) Reproducibility.
 A measure of the ability to reproduce an answer by
scientists using the same experimental approach but
in different laboratories using different equipment.
iii) Accuracy.
 A measure of how close one can actually measure
the true value of the parameter being measured.
iv) Simplicity of operation.
 A measure of the ease with which the analysis may
be carried out by relatively unskilled workers.
v) Economy.
 The total cost of the analysis, including the reagents,
instrumentation, and time.
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2.2 STAGES IN FOOD ANALYSIS
vi) Speed.
 The time needed to complete the analysis.
vii) Sensitivity.
 A measure of the lowest concentration of material
that can be detected or quantified by a given
technique.
viii) Specificity.
 A measure of the ability to detect and quantify
specific components within a food material, even in
the presence of other similar components.
ix) Safety.
 A measure of the potential hazards associated with
reagents and procedures used in the analysis.
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2.2 STAGES IN FOOD ANALYSIS
x) Destructive /nondestructive.
 Whether the sample is destroyed during
the analysis or remains intact.
xi) Official approval.
 Various international bodies have given
official approval to methods that have
been comprehensively studied by
independent analysts and shown to be
acceptable to the various organizations
involved, e.g. AOAC.
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2.3 CARBOHYDRATE ANALYSIS
2.3.1 Introduction
 Ingested carbohydrates are almost exclusively of plant origin,
with milk lactose being the major exception.
 Monosaccharides:
 sometimes called simple sugars
 only D-glucose and D-fructose are found in other than
minor amounts.
 the only carbohydrates that can be absorbed from the
small intestine.
 Higher saccharides (oligo- and polysaccharides) must first be
digested (i.e., hydrolyzed to monosaccharides) before
absorption and utilization can occur.
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2.3 CARBOHYDRATE ANALYSIS
2.3.1 Introduction
 oligo- and polysaccharides






Most sources consider an oligosaccharide to be a carbohydrate
composed of from 2 to 10 sugar (saccharide) units.
A polysaccharide usually contains from 30 to at least 60,000
monosaccharide units.
At least 90% of the carbohydrate in nature is in the form of
polysaccharides.
Starch polymers are the only polysaccharides that humans can
digest and use as a source of calories and carbon.
All other polysaccharides are nondigestible.
Humans can digest only sucrose, lactose,
maltooligosaccharides /maltodextrins, and starch.
 All are digested with enzymes found in the small intestine.
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2.3 CARBOHYDRATE ANALYSIS
2.3.1 Introduction
Table: Occurrences of Some Major Carbohydrates in Foods
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2.3 CARBOHYDRATE ANALYSIS
2.3.1 Introduction
Table: Occurrences of Some Major Carbohydrates in Foods
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2.3 CARBOHYDRATE ANALYSIS
2.3.1 Introduction
Total
Carbohydrate
Contents of
Selected Foods
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2.3 CARBOHYDRATE ANALYSIS


2.3.2 Sample preparation
Raw material, ingredient, or food product being
analyzed and the specific carbohydrate being
determined.
Drying:




First step used for most foods analysis
used to determine moisture content / total solid content.
Other than beverages, drying is done by placing a weighed
amount of material in a vacuum oven and drying to
constant weight at 55◦C and 1mm Hg pressure.
Then, the material is ground to a fine powder, and lipids
are extracted using 19:1 vol/vol chloroform–methanol
in a Soxhlet extractor.
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2.3 CARBOHYDRATE ANALYSIS
2.3.2 Sample preparation
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Figure 2.1 Soxhlet extractor
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2.3 CARBOHYDRATE ANALYSIS
2.3.2 Sample preparation
 Moisture and total solids contents of foods can be
calculated:
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2.3 CARBOHYDRATE ANALYSIS
2.3.2 Sample preparation
Prior extraction of lipids makes extraction of
carbohydrates easier and more complete.
 However, other sample preparation schemes may
be required.
 For example, the AOAC International method for
pre-sweetened, ready-to-eat breakfast cereals
calls for removal of fats by extraction with
petroleum ether (hexane) rather than the
method described above and extraction of
sugars with 50% ethanol (AOAC Method
982.14).

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2.3 CARBOHYDRATE ANALYSIS
2.3.2 Sample preparation
Figure 2.2: Flow diagram for sample preparation and
extraction of mono- and disaccharides.
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2.3 CARBOHYDRATE ANALYSIS

2.3.3 Method of Analysis
Chromatographic methods:


To determine low-molecular-weight carbohydrates,
To replace
classical colorimetric methods for total carbohydrate
 various reducing sugar methods
 physical measurements


The classical chemical methods:
i)
Total Carbohydrate:
a)
Phenol-Sulfuric Acid Method



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Carbohydrates are destroyed by strong acids and/or high
temperatures.
It is simple, rapid, sensitive, accurate, specific for
carbohydrates, and widely applied.
The reagents are inexpensive, readily available, and stable.
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2.3 CARBOHYDRATE ANALYSIS
2.3.3 Method of Analysis



ii.
All classes of sugars (including sugar derivatives and
oligo- and polysaccharides) can be determined with this
method.
A stable color (yellow-orange) is produced, and results
are read from a spectrometer (Absorbance) and they are
reproducible.
Under proper conditions, this method is accurate to
±2%.
Total Reducing Sugar:
a)

Somogyi–Nelson Method
Reducing sugars are those sugars that have an aldehydo
group (e.g. aldoses) that can give up electrons (i.e., act as a
reducing agent) to an oxidizing agent, which is reduced by
receiving the electrons.
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2.3 CARBOHYDRATE ANALYSIS
2.3.3 Method of Analysis
Total Reducing Sugar:
ii.
a)





Somogyi–Nelson Method
Reducing sugars are those sugars that have an aldehydo group
(e.g. aldoses) that can give up electrons (i.e., act as a reducing
agent) to an oxidizing agent, which is reduced by receiving the
electrons.
reduction of Cu(II) ions to Cu(I) ions by reducing sugars.
Cu(I) ions  reduce an arsenomolybdate complex, prepared by
reacting ammonium molybdate and sodium arsenate in sulfuric
acid.
Reduction of the arsenomolybdate complex produces an
intense, stable blue color that is measured
spectrophotometrically.
This reaction is not stoichiometric and must be used with a
standard curve of the sugar(s) being determined or D-glucose.
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2.3 CARBOHYDRATE ANALYSIS
2.3.3 Method of Analysis
iii) Dinitrosalicylic acid (DNS)method:
 measures reducing sugars naturally occurring in
foods or released by enzymes, but is not much used.
 3,5-dinitrosalicylate  reduced to the reddish
monoamine derivative.
In general,
 The classical chemical methods:

Disadvantage:


Not stoichiometric. Therefore, require standard curves.
This makes them particularly problematic when a
mixture of sugars is being determined.
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2.3 CARBOHYDRATE ANALYSIS
2.3.3 Method of Analysis
Physical methods:
(i) Microscopy
 [light, fluorescence, confocal scanning laser (CSLM), Fourier
transform infrared (FTIR), scanning electron (SEM), and
transmission electron (TEM) microscopies].
(ii) Mass and NIR Transmittance Spectrometry
 to determine sugar content.
(iii) Specific gravity
 To determine the concentration of a carbohydrate solution
 It is accurate only for pure sucrose or other solutions of a single
pure substance.
 The most common is use of a calibrated hydrometer either in
◦Brix, which corresponds to sucrose concentrations by weight, or
in Baumé Modulus (Bé).

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2.3 CARBOHYDRATE ANALYSIS
2.3.3 Method of Analysis
(iv) Refractive Index
 electromagnetic radiation.
 The ratio of the sine θ of incidence to the
sine θ of refraction.
 To determine total solids in solution.
 It is accurate only for pure sucrose or other
solutions of a single pure substance
 In general, physical measurements are not
specific for carbohydrates.
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2.3 CARBOHYDRATE ANALYSIS
2.3.3 Method of Analysis

Chromatographic methods (HPLC and GC)
separate mixtures into the component sugars
 identify each component by retention time
 provide a measurement of the mass of each
component.
 HPLC is widely used for identification and
measurement of mono- and oligosaccharides.


Enzymatic methods
specific and sensitive
 but seldom, except in the case of starch,
 determination of only a single component desired.

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2.4 PROTEIN ANALYSIS
2.4.1 Introduction

Protein analysis :
1. Total protein content
2. Content of a particular protein in a mixture
3. Protein content during isolation and purification of
a protein
4. Nonprotein nitrogen
5. Amino acid composition
6. Nutritive value of a protein
Protein content in food varies widely.
 Foods of animal origin and legumes are excellent
sources of proteins

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2.4 PROTEIN ANALYSIS
2.4.1 Introduction

Protein Content of
Selected Foods
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2.4 PROTEIN ANALYSIS
2.4.1 Introduction

Proteins





an abundant component in all cells
and almost all except storage proteins are important for
biological functions and cell structure.
Food proteins are very complex.
vary in molecular mass, ranging from approximately 5000 to
more than a million Daltons.
composed of elements including hydrogen (-H-), carbon (-C-),
nitrogen (-N-), oxygen (-O-), and sulfur (-S-).
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2.4 PROTEIN ANALYSIS
2.4.1 Introduction

Nitrogen
 the
most distinguishing element present in
proteins.
 content in various food proteins ranges from 13.4 to
19.1% due to the variation in the specific amino
acid composition of proteins.
 Generally,
proteins rich in basic amino acids
contain more nitrogen.
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2.4 PROTEIN ANALYSIS
2.4.2 Methods of Analysis

There are several methods of protein analysis:
(a) Kjeldahl method
(b) Dumas method (N combustion)
(c) Infrared spectroscopy
(d) Biuret method
(e) Lowry method
(f) Bradford method
(g) Bicinchoninic acid (BCA) method
(h) Absorbance at 280nm
(i) Absorbance at 220nm
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2.4 PROTEIN ANALYSIS
2.4.2 Methods of Analysis
1. the Kjeldahl method:
proteins and other organic food
components in a sample are digested
with sulfuric acid in the presence of
catalysts.
 The total organic nitrogen is converted
to ammonium sulfate.
 The digest is neutralized with alkali and
distilled into a boric acid solution.

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2.4 PROTEIN ANALYSIS
2.4.2 Methods of Analysis
 The
borate anions formed are titrated with
standardized acid, which is converted to
nitrogen in the sample.
 The result of the analysis represents the
crude protein content of the food since
nitrogen also comes from nonprotein
components
 The Kjeldahl method also measures
nitrogen in any ammonia and ammonium
sulfate.
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2.4 PROTEIN ANALYSIS
2.4.2 Methods of Analysis
Kjeldahl method: General Procedures and Reactions
i) Sample Preparation:
 Solid foods are ground to pass a 20-mesh screen.
 Samples for analysis should be homogeneous.
 No other special preparations are required.

ii) Digestion:
 Place sample (accurately weighed) in a Kjeldahl flask.
 Add acid and catalyst; digest until clear to get
complete breakdown of all organic matter.
 Nonvolatile ammonium sulfate is formed from the
reaction of nitrogen and sulfuric acid.
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2.4 PROTEIN ANALYSIS
2.4.2 Methods of Analysis
 During
digestion, protein nitrogen is liberated
to form ammonium ions;
 sulfuric acid oxidizes organic matter and
combines with ammonium formed;
 carbon and hydrogen elements are converted
to carbon dioxide and water.
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2.4 PROTEIN ANALYSIS
2.4.2 Methods of Analysis
iii) Neutralization and Distillation:
 The digest is diluted with water.
 Alkali-containing sodium thiosulfate is added to
neutralize the sulfuric acid.
 The ammonia formed is distilled into a boric
acid solution containing the indicators
methylene blue and methyl red.
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2.4 PROTEIN ANALYSIS
2.4.2 Methods of Analysis
iv) Titration:
 Borate anion (proportional to the amount of
nitrogen) is titrated with standardized HCl.
v) Calculation:

A reagent blank should be run to subtract
reagent nitrogen from the sample nitrogen.
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2.4 PROTEIN ANALYSIS
2.4.2 Methods of Analysis

where:
N HCl = normality of HCl, in mol/1000 ml
Corrected acid vol. = (ml std. acid for sample) –
(ml std. acid for blank)
14 = atomic weight of nitrogen
 A factor is used to convert % N to %crude protein.
 Most proteins contain 16% N, so the conversion
factor is 6.25 (100/16 = 6.25).
or
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2.4 PROTEIN ANALYSIS
2.4.2 Methods of Analysis

Conversion factors for various foods are:
Table: Nitrogen to Protein Conversion Factors for Various Foods
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2.4 PROTEIN ANALYSIS
2.4.2 Methods of Analysis

Advantages of the Kjeldahl method :
1. Applicable to all types of foods
2. Inexpensive (if not using an automated system)
3. Accurate; an official method for crude protein
content
4. Has been modified (micro Kjeldahl method) to
measure microgram quantities of proteins

Disadvantages the Kjeldahl method :
1. Measures total organic nitrogen, not just protein
nitrogen
2. Time consuming (at least 2 h to complete)
3. Poorer precision than the biuret method
4. Corrosive reagent
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2.4 PROTEIN ANALYSIS
2.4.2 Methods of Analysis
2. The Lowry method :


combines the biuret reaction with the reduction of
the Folin–Ciocalteau phenol reagent
(phosphomolybdic-phosphotungstic acid) by tyrosine
and tryptophan residues in the proteins.
 Biuret reaction: A violet-purplish color is produced
when cupric ions are complexed with peptide
bonds (substances containing at least two peptide
bonds) under alkaline conditions.
The bluish color developed is read at 750nm (high
sensitivity for low protein concentration) or 500nm
(low sensitivity for high protein concentration).
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2.4 PROTEIN ANALYSIS
2.4.2 Methods of Analysis
 A standard curve based on the linearity of the color
response to protein concentration is needed.
 Due to its simplicity and sensitivity, the Lowry method
has been widely used in protein biochemistry.
 However, it has not been widely used to determine
proteins in food systems without first extracting the
proteins from the food mixture.
 Color is not strictly proportional to protein
concentration.
 The reaction is interfered with to varying degrees by
sucrose, lipids, phosphate buffers, monosaccharides,
and hexoamines.
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2.4 PROTEIN ANALYSIS
2.4.2 Methods of Analysis
3. Bicinchoninic Acid (BCA)Method:
 Proteins and peptides (as short as dipeptides)
reduce cupric ions to cuprous ions under
alkaline conditions.
 The cuprous ion then reacts with the applegreenish bicinchoninic acid (BCA) reagent to
form a purplish complex.
 The color measured at 562nm is near linearly
proportional to protein concentration over a wide
range of concentration from micrograms up to
2mg/ml.
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2.4 PROTEIN ANALYSIS
2.4.2 Methods of Analysis

Advantages of the BCA method:
1. Sensitivity is comparable to / better than that of the Lowry
method
2. One-step mixing is easier than in the Lowry method.
3. The reagent is more stable than for the Lowry reagent.
4. Nonionic detergent and buffer salts do not interfere with the
reaction.
5. Medium concentrations of denaturing reagents do not interfere.

Disadvantages of the BCA method :
1. Color is not stable with time.
2. Any compound capable of reducing Cu2+ to Cu+ will lead to color
formation.
3. Reducing sugars interfere to a greater extent than in the Lowry
method. High concentrations of ammonium sulfate also
interfere.
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2.5 FAT ANALYSIS
2.5.1 Introduction
Lipids are a group of substances that, in general,
are soluble in ether, chloroform, or other organic
solvents but are sparingly soluble in water.
 The terms lipids, fats, and oils are often used
interchangeably.
 The term “lipid” commonly refers to the broad,
total collection of food molecules.
 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.
 FDA has defined total fat as the sum of fatty acids
from C4 to C24, calculated as triglycerides.

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2.5 FAT ANALYSIS
2.5.1 Introduction
Fat Content of Selected Foods
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2.5 FAT ANALYSIS
2.5.1 Introduction
Fat Content of Selected Foods
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2.5 FAT ANALYSIS
2.5.2 Sample preparation
The sample preparation for lipid analysis
depends on the type of food and the type and
nature of lipids in the food.
 The extraction method for lipids in liquid milk is
generally different from that for lipids in solid
soybeans.
 To analyze the lipids in foods effectively:

knowledge of the structure
 the chemistry
 the occurrence of the principal lipid classes and
their constituents is necessary.

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2.5 FAT ANALYSIS
2.5.2 Sample preparation



No single standard method for the extraction of all
kinds of lipids in different foods.
Sample preparation should be carried out under an
inert atmosphere of nitrogen at low temperature to
minimize chemical reactions such as lipid oxidation.
Several preparatory steps are common in lipid analysis.
 These act to aid in extraction by removal of water
(pre-drying), reduction of particle size, or separation
of the lipid from bound proteins and/or carbohydrates
(by acid hydrolysis).
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2.5 FAT ANALYSIS
2.5.2 Sample preparation
Acid Hydrolysis:
 A significant portion of the lipids in foods such as dairy,
bread, flour, and animal products is bound to proteins
and carbohydrates, and direct extraction with nonpolar
solvents is inefficient.
 Such foods must be prepared for lipid extraction by acid
hydrolysis.

The inaccuracy that can occur if samples are not
prepared by acid hydrolysis.
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2.5 FAT ANALYSIS
2.5.2 Sample preparation
Acid Hydrolysis:
 can break both covalently and ionically bound
lipids into easily extractable lipid forms.
 sample can be pre-digested by refluxing for 1 h
with 3N hydrochloric acid.
 Ethanol and solid hexametaphosphate may be
added to facilitate separation of lipids from
other components before food lipids are
extracted with solvents
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2.5 FAT ANALYSIS
2.5.3 Methods of Analysis


The total lipid content of foods is commonly determined by
organic solvent extraction methods, which can be classified
as:
i)
continuous (e.g., Goldfish),
ii)
semicontinuous (e.g., Soxhlet),
iii) discontinuous (e.g., Mojonnier, Folch), or
iv) by GC analysis.
v)
Nonsolvent wet extraction methods, (e.g. the Babcock or
Gerber)
vi) Instrumental methods, (e.g. NMR, infrared)
vii) Foss-Let method (specific gravity)
These methods are rapid and so may be useful for quality
control but generally require correlation to a standard
solvent extraction method.
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2.5 FAT ANALYSIS
2.5.3 Methods of Analysis

Solvent selection:
Ideal solvents for fat extraction should have a high
solvent power for lipids and low or no solvent
power for proteins, amino acids, and
carbohydrates.
 evaporate readily and leave no residue, have a
relatively low boiling point, and be nonflammable
and nontoxic in both liquid and vapor states.
 penetrate sample particles readily, be in single
component form to avoid fractionation, and be
inexpensive and nonhygroscopic.

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2.5 FAT ANALYSIS
2.5.3 Methods of Analysis

It is difficult to find an ideal fat solvent to meet all
of these requirements.
 Ethyl ether and petroleum ether are the most
commonly used solvents, but pentane and
hexane are used to extract oil from soybeans.
 Ethyl ether has a boiling point of 34.6◦C and is
a better solvent for fat than petroleum ether.

It is generally expensive compared to other
solvents, has a greater danger of explosion and
fire hazards, is hygroscopic, and forms peroxides.
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2.5 FAT ANALYSIS
2.5.3 Methods of Analysis

Petroleum ether is the low boiling point
fraction of petroleum and is composed mainly
of pentane and hexane.
 It has a boiling point of 35–38◦C and is
more hydrophobic than ethyl ether.
 It is selective for more hydrophobic lipids,
cheaper, less hygroscopic, and less
flammable than ethyl ether.
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2.5 FAT ANALYSIS
2.5.3 Methods of Analysis
1. Continuous Solvent Extraction Method: Goldfish Method
i. Principle and Characteristics
 For continuous solvent extraction, solvent from a boiling
flask continuously flows over the sample held in a
ceramic thimble.
 Fat content is measured by weight loss of the sample or
by weight of the fat removed.
 The continuous methods give faster and more efficient
extraction than semi-continuous extraction methods.
 However, they may cause channeling which results in
incomplete extraction.
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2.5 FAT ANALYSIS
Goldfish Method
2.5.23 Methods of Analysis
Goldfish fat extractor.
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2.5 FAT ANALYSIS
Goldfish Method
2.5.3 Methods of Analysis
ii) Goldfish Method & Procedures:
1. Weigh pre-dried porous ceramic extraction thimble. Place
vacuum oven dried sample in thimble and weigh again.
2. Weigh pre-dried extraction beaker.
3. Place ceramic extraction thimble into glass holding tube
and then up into condenser of apparatus.
4. Place anhydrous ethyl ether (or petroleum ether) in
extraction beaker and put beaker on heater of apparatus.
5. Extract for 4 h.
6. Lower the heater and let sample cool.
7. Remove the extraction beaker and let air dry overnight,
then at 100◦C for 30 min. Cool beaker in desiccators and
weigh.
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2.5 FAT ANALYSIS
Goldfish Method
2.5.3 Methods of Analysis
iii) Calculation:
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2.5 FAT ANALYSIS
Soxhlet Method
2.5.3 Methods of Analysis
2. Semicontinuous Solvent Extraction Method:
Soxhlet Method
i) Principles and Characteristics:
 For semicontinuous solvent extraction, the solvent
builds up in the extraction chamber for 5–10 min and
completely surrounds the sample and then siphons
back to the boiling flask.
 Fat content is measured by weight loss of the sample or
by weight of the fat removed.
 This method provides a soaking effect of the sample
and does not cause channeling.
 However, this method requires more time than the
continuous method.
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2.5 FAT ANALYSIS
Soxhlet Method
2.5.3 Methods of Analysis
ii) Calculation
% Fat on dry weight basis
= g of fat in sample
g of dried sample
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2.5 NEW TECHNIQUES FOR FOOD ANALYSIS

With the success in the application of
molecular biology and genetics technology in
clinical diagnostics, their use has been applied
actively in food analysis to the identification of
species, varieties, geographical origin,
admixtures and adulterations, microbial
pathogens and contaminants of starter
cultures and so on.
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2.5 NEW TECHNIQUES FOR FOOD ANALYSIS

The new techniques of genetic engineering:
 gene
isolation
 Splicing
 introduction into recipient bacteria
 Cloning the hybridoma technique
 recombinant DNA

The result is success in the application of
immunochemical techniques, biosensors, DNA
probes and the polymerase chain reaction for
rapid and foolproof analysis of foods.
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2.5 NEW TECHNIQUES FOR FOOD ANALYSIS
Caffeine Test Strips & Kits
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Biosensor that detects pathogens
in poultry
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Nutrient deficiency diseases
Scurvy
Pellagra
(Deficiency of vitamin (Niacin, one of the B vitamins
C in the diet)
is deficient in the diet)
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ERT 426 Food Engineering Semester 1 Academic Session 2014/15
Kjeldahl method
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