Contents 314 (new).pdf · Contents # Title Page 1 ... Phenol-Sulfuric Acid Colorimetric Method 11 ... as wheat bran or corn bran, xylose should be used to construct the standard curve

2 Organized by: Dalal Al-Saedi & Salha Al-Shamrani‏

Contents

# Title Page

1 Energy Balance and Body Weight Control 3

2 Colorimetric Determination of Sugars in Dates: Phenol-Sulfuric Acid Colorimetric

Method 11

3 Qualitative Estimation of Fructose in Biological Material 16

4 Extraction of Total Lipids by Bligh and Dyer Method 20

5 Determination of Fat in Potato Chips 25

6 Determination of protein in milk using formaldehyde method 31

7 Determination of chloride content in cheese 35

8

Determination of Vitamin C in Foods by Iodometric Assay 40

Total acidity of fruit juices 46

9 Determination of nicotinic acid in food 50

10 Determination of Tannins in Tea 55

11 Estimation of water content in cow‟s milk 59


Energy Balance and Body Weight Control

Nutritional Assessment

Nutrition assessment evaluates a person’s health from a nutrition perspective by:

- History taking.

- Physical examination

- Biochemical analysis.

- Anthropometric measurements.

There are different methods that can help you evaluate the health of your current body weight.

1) Body Mass Index

Body Mass Index (BMI) is a number calculated from a person‟s weight and height. BMI is used

as a screening tool to identify possible weight problems for adults. However, BMI is not a diagnostic

tool. For example, a person may have a high BMI. However, to determine if excess weight is a health

risk, a healthcare provider would need to perform further assessments. BMI is calculated as:

Methods

Body Mass Index

(BMI) Body Composition Fat Distribution Pattern

BMI =𝐵𝑜𝑑𝑦 𝑤𝑒𝑖𝑔ℎ𝑡 (𝑘𝑔)

𝐻𝑒𝑖𝑔ℎ𝑡𝟐(𝑚)


BMI for adults are interpreted as follows:

BMI Weight Status Comment < 18.5 Under weight Associated with increased risk of

health problems and death

18.5 to 24.9 Normal Healthy weight-for-height

25 to 29.9 Over weight

30 to 39.9 Obese Increased health risk

≥40 Morbid obesity Major health risk

Note: Adult BMIs should not be applied to children, still growing

adolescents, older people, pregnant and lactating women and high muscular

.

Exercise (1):

Calculate your BMI? What your value

shows?


2) Body Composition

Body composition is the proportion of fat and fat-free mass (muscle, bone, organs,

and water) that make up a person‟s total body weight. Direct measures of body

composition are impossible in living human beings. Instead, researchers assess body

composition indirectly based on the following assumption

Body weight = Fat + Lean tissue (including water)

Healthy body composition involves a high proportion of fat-free mass

and an acceptably low level of body fat, adjusted for age and gender.

Figure 1: Body Composition


How is Body Composition Measured?

There are several different methods used to determine how much

fat your body is carrying

Skinfold measurement

Girth measurements

Body Weight

Hydrostatic Weighing (also known

as underwater weighing)

How many factors influence body composition

Gender, age, diet, activity level, and genes

*Some aspects of your body composition are genetic (where you store fat), but

most fat increase is related to lifestyle

How to lose fat?

Through a lifestyle that includes a sensible diet and exercise.

How to add muscle mass?

Through resistance training/strength training.


3) Fat distribution patterns:

The prevalence of abdominal obesity exceeds that of general obesity. Obesity is

associated with an increased risk of multiple cardio-metabolic risk factors. To evaluate

the health of your body weight, it is also helpful to consider the way fat is distributed

throughout your body. This is because your fat distribution is known to affect your risk

for various diseases. Some people store fat in upper- body areas whereas others stores fat

lower on the body.

Types of fat patterning

Figure 2: Types of fat patterning.

Pear

shaped

Doesn't‏seem‏to‏

significantly‏increase‏a‏

person's‏risk‏for‏chronic‏

disease‏


To determine the type of fat patterning, flow these steps:

1-Measure your circumference of natural waist in inches

(i.e. the narrowest part of your torso from the front).

2- Measure your hip circumference (in inches).

3- Divide the waist value by the hip value. This

measurement is called “waist-to- hip ratio”.

A ratio higher than 0.90 (in men) and higher than 0.80 (in women) is an

apple shaped fat distribution pattern.

Exercise (2):

A 45 years old man, his waist

circumference is 50 inches and his hips

are 40 inches: calculate his hip-to-waist

ratio?

What type of fat patterning does he have?

Is he in risk for chronic disease? Why?

Exercise (3):

- Calculate your waist-to-hip ratio? - What type of fat patterning do you have? - Are you at risk for chronic disease?


The energy content of

each food is comes from

Carbohydrates

provides 4 Kcal/g

Fat

provides 9 Kcal/g

Alcohol

provides 7 Kcal/g

Protein

provides 4 Kcal/g

Energy Balance

To achieve or maintain a healthy body weight you must pay more attention to the

important concept of Energy Balance, that is the relationship between “energy in”

(food calories taken into the body through food and drink) and “energy out” (calories

being used in the body for our daily energy requirements).

Energy intake

The value of energy intake includes all foods and beverages, expressed as calories

or kilocalories per day (cal/day or Kcal/day).

Energy intake = Energy expenditure


References

Wardlaw, G. and Smith, A. (2009): Contemporary Nutrition. Seventh edition.

McGrowHill.USA. (chapter 7) How the number of calories in a certain food is

determined with a bomb calorimeter instrument

Thompson, J. and Manore, M. (2009): Nutrition an applied approach. Second edition.

Pearson Benjamin cummings. USA.(chapter 11) various methods for the determination

of body composition.

‏)األولي الطبعث الغذائية. الوجباخ جخطيظ ( 2004) نحس بي عصام ،ةعويض ‏الحاسع الفصل. ىزأخ قزط (

‏.ةالكلي ةالطاق تإححياجا إجوالي زيذلحق

Exercise (4):

One cup of oatmeal contains 6 gm of protein, 25 gm

of carbohydrates and 2 gm of fat. Calculate the total

energy content of this oatmeal?


Colorimetric Determination of Sugars in Dates: Phenol-

Sulfuric Acid Colorimetric Method

Background

Dates are a good source of various vitamins and minerals. It‟s a

good source of energy, sugar and fiber. Essential minerals such as

calcium, iron, phosphorus, sodium, potassium, magnesium and zinc are found in dates. It

also contains vitamins such as thiamin, riboflavin, niacin, folate, vitamin A and vitamin

K.

The phenol-sulfuric acid is simple and rapid colorimetric method to determine total

carbohydrates in a sample. The method detects virtually all classes of carbohydrates,

including mono-di-,oligo- and polysaccharides.

In this method, the concentrated sulfuric acid breaks down any

polysaccharides, oligosaccharides, and disaccharides to monosaccharides. Pentose’s

carbon compounds) are then dehydrated to furfural, and hexoses(6-carbon

compounds) to hydroxyl methyl furfural. These compounds then react with phenol to

produce a yellow-gold color. For products that are very high in xylose(a pentose), such

as wheat bran or corn bran, xylose should be used to construct the standard curve for the

assay, and measure the absorption at 480 nm. For products that high in hexose sugars

glucose is commonly used to create the standard curve and the absorption is measured at

490 nm.

http://ndb.nal.usda.gov/ndb/foods/show/2498?fg=&man=&lfacet=&format=Abridged&count=&max=25&offset=&sort=&qlookup=dates


The color for this reaction is stable for several hours and the accuracy of the

method is within ±2% under proper conditions.

Carbohydrates are the major source of calories in soft drinks, beer and fruit

juices, supplying 4 Cal/g carbohydrate.

Objective

Determine the carbohydrate concentration of dates and soft drinks, then calculate the

calorie content those samples.

Principle

Principle of this method carbohydrates(simple sugars oligosaccharides polysaccharides,

and their derivatives) react in the presence of strong acid and heat to generate furan

derivatives that condense with phenol to form stable yellow-gold compounds that can be

measured spectrophotometrically,

Chemical & Material Hazards

Phenol [C6H6O] 5%: dissolve 50gm of redistilled phenol in water

and dilute to 1-L

Toxic

Sulfuric acid [H2SO4], concentrated, 96% Reagent grade. Corrosive

Sugar solution, fructose, 0.3g/l.

Arabinose or fructose Dates Distilled water


Equipment

Mortar Laboratory balances

Volumetric flask (100ml) Vortex mixer

Conical (Erlenmeyer)flask (100ml) Water Bath

Volumetric Cylinder Spectrophotometer or colorimetric

Filter Paper

Funnel

Pipette 1ml & 5ml

Cuvette

Test Tube

Method

A. Preparation of date’s homogenate

1- Weigh accurately 1gm of dates.

2- Homogenize in 50ml of distilled water in a warring blender.

3- Boil for 10min.

4- Cool, and filter in a 100ml volumetric flask, and complete to volume with water.

Shake well to mix. Decolorize with charcoal if necessary.

5- Dilute 1ml of the above solution to 100ml and use it as unknown.

B. Preparation of date’s homogenate

1- Prepare sugar standard curve from 10-70 μg/ml (0.075-0.15-0.225-0.3 mg/ml).

2- Pipette 0.5ml of aqueous sample solution of sugar into colorimetric tube (cuvette) .

3- Add 0.5ml of 5% phenol and mix.

4- Add 2.5ml of sulfuric acid from a fast-flowing dispenser to each tube in

order to produce good mixing and even heating.

5- Mix the contents of each tube by the same technique and let stand in air for 10 min.

6- Cool to room temperature.

7- Read the absorbance of the yellow-orange color at 490 nm for hexsose and 480 nm for

pentoses.

8- Plot a standard curve of sugar ranging from 10-70 μg/ml of sugar


Calculation

Determine the concentration of the sugar from the standard curve or by the

equation as follow.

=

References

Nielsen, S. (2003): Food Analysis. Third Edition. Kluwer Academic/Plenum Publishers .

والحوسيع للنشز الفجز دار .األولي الطبعة .األغذية جحليل ( 2002 ) أنور عاطف أبوعزب، دمحم، إبزاهين حسن،


Result Sheet

* Fill the table with your results

* Draw a standard curve of Conc. vs. Abs.??

* Determine the concentration of the sugar from the standard curve ?

Concentration

(Conc.)

Absorbance

(Abs(


Qualitative Estimation of Fructose in Biological

Material

Background

Fructose, the sweetest of sugars, is a simple carbohydrate also

known as fruit sugar. It is found mainly is fruits, from which it gets its

name, or in honey. Honey therefore is a form of sugar and cannot be

used as a sugar substitute. The amount of fructose in fruits depends on the degree of

ripeness.

As the fruit ripens, some of the stored starch turns to sugar. High fructose corn

syrups are increasingly being used in processed food products, and contribute a major

source of increases sugar intake. Fructose is the sweetest simple sugars.

Objective

Estimation amount of fructose in different types of food.

Principle

The fructose sugar is dehydrated in the presence of concentrated HCI to form

hydroxymethyl furfural. The formed furfural derivative then condenses with resorcinol

to yield a cherry red colored product that is measured spectrophotometrically at 470nm.


Method

1-In each tube(standard, unknown and blank*) place the following:

(2 ml sample -2 ml reagent A -6 ml reagent B), then mix

2-Let stand in a water bath for 8 min. at 80oC. Cool to room temperature and read at

530nm.

* Can be use water as blank.


Fructose standard solution: 2mg/ml, 2g/l, or 0.2g/l if it is so concentrated

you can use 1mg/ml).

Fruit juice: Make decolorization by charcoal, filtrates, and then dilutes

1ml juice with 100ml-distilled water.

Honey: 0.4g/100ml.

Reagent (A): freshly prepared: 50mg resorcinol (0.05g) dissolved up to

50ml with 95% ethanol. Store in a dark bottle at 4oC.

Reagent (B): 50ml conc. HCl is added carefully to 10ml water. Corrosive

Equipment

Conical (Erlenmeyer) flask (200ml) Laboratory balances Pipette (5ml) Centrifuge and its tubes

Backer (50ml) Hot Plate

Mortar

Volumetric Cylinder

Dropper

Funnel

Filter Paper


Abs= Absorbance

Conc.= Concentration

Unk= Unknown

St= Standard

Calculation

Determine the concentration of the fructose

=

Reference

Fasman, G. D. (1989). Practical handbook of biochemistry and molecular biology. CRC

press.‏


Result Sheet

Calculate the concentration of the fructose in your sample?


The mixture of organic

solvent used to

prevent any

hydrolysis

or oxidation for lipid

Extraction of Total Lipids by Bligh and Dyer Method

Background

Lipids form a heterogeneous group of hydrocarbon

containing organic compounds which categorized by the fact that

they are soluble in nonpolar solvents (such as alcohol, acetone,

chloroform, benzene, ether and hexane) and are relatively insoluble

in water. Lipid molecules have these properties because they consist largely of long

hydrocarbon tails which are hydrophobic in nature.

Other than this hydrophobicity, no other common features can be attributed to

their structure. This property of specific solubility is made use of in extracting lipids from

tissues; free from any water-soluble matter but the subsequent analytical methods are

largely individualistic.

For general extraction of almost all lipids from biological samples, either a

mixture of ethanol and ethyl ether or a mixture of chloroform and methanol is used. The

lipids are generally bound to proteins in the biological samples and in that situation (as

lipoprotein) cannot be efficiently extracted by non-polar organic solvents alone. The

inclusion of methanol or ethanol helps in breaking the bonds

between the lipids and proteins.

Objective

Extraction of total lipids in different of sample (milk, coffee mate,

chips and chocolate).


Principle

Lipids are soluble in organic solvents and insoluble in water.

Therefore, water insolubility is the essential analytical property used as the basis for the

separation of lipids from proteins, water, and carbohydrates in foods.


Chloroform carcinogen

Ethanol Flammable liquid and vapor

Samples such as (milk, coffee mate, chips and chocolate)

Distilled water

Equipment


Backer (50ml) Hot Plate

Mortar

Volumetric Cylinder

Dropper

Funnel

Filter Paper


Method

1- Weigh 1g of sample.

2- Grind it with 5ml of distilled water

3- Transfer in conical flask with 15ml of chloroform and ethanol mixture (2:1 v/v) and

mixed well.

4- For complete extraction, it is advisable to keep this for 30 minutes at room

temperature in dark place.

5- At the end of this period centrifuge for 10 minutes at 2000-3000 rpm.

6- Generally 3 layers are seen, a clear lower layer of chloroform containing the entire

lipid.

7- The methanol layer is discarded and the lower layer is carefully collected free of inter

phase either by sucking out with a fin capillary or by filtration through glass wool.


8- The organic layer "lower layer" is taken in a pre-weighed beaker (W1) and carefully

evaporated by keep the sample in warm water bath. It is also advisable to keep the sample

covered with a dark paper to protect from light, because some lipids get polymerized or

decomposed on exposure to light and heat.

9- When the solution is free of organic solvents, the weight is determined again (W2).

Calculation

The weight of lipids =W2 – W1= Z gm of lipids

G% =

The kcal provided by the sample

1 gm of lipid 9 kcal

z gm ??

The Kcal provided by the sample= Z × 9= Y Kcal

References

Nielsen, S. (2003): Food Analysis. Third Edition. Kluwer Academic/Plenum Publishers .


Result Sheet

Calculate the weight of lipid and the kcal provided by the sample


Determination of Fat in Potato Chips

Background

Recently, there has been a lot discussion of calories and

fats in our foods in the news media. Most food labels list

recommended serving sizes, sometimes with unrealistic

quantities, of the food product and then lists the nutritional

information based on that serving, assuming a 2,000 calorie per day diet.

Nutritional information usually includes calories, total fat, saturated fat, cholesterol,

sodium, total carbohydrate (with separate listing of dietary fiber and sugars), and protein.

The label information may also include vitamins and minerals. Nutritionists recommend

that no more than 30% of our daily 2000 calories come from fat. However, in our snack

food and fast food world, we often eat a diet that contains a larger percentage of fat. So,

the question arises, how much fat is in a snack bag of a food such as potato chips, or a

standard serving of French fries?

Objective

Determining the fat content of several different brands of potato chips using a technique

called extraction.


Principle

Extract the fat from food. Extraction is the process of dissolving one substance

from a mixture of chemicals and separating it from the rest of the mixture. Fat is soluble

in organic solvents but not water. Adding an organic solvent to a mixture will separate

the fat from the rest of the chemicals. You can then evaporate the solvent (these are

almost always low boiling liquids) to leave the fat behind.

Method

1. Take amount of potato chips. Place them in a small plastic bag and crush them.

2. Weigh 2g of potato chips

3. Transfer them in round bottom flask and weigh (W1)

4. Add 4 mL of hexane to the flask.

5. Mix the hexane with the crushed chips by gently swirling the flask for about 1

minute.


Hexane [C6H14] Flammable

Chips

Equipment

Conical (Erlenmeyer)flask (250ml) Laboratory balances

Pipette (5ml) Water Bath

Beaker (30ml) Hot plate

Small plastic bag


6. Carefully, pour off the hexane into a waste container, without pouring any pieces

of the crushed chips. A small amount of hexane will remain in the flask.

7. Add 2 mL of hexane to the flask.

8. Mix the hexane with the crushed chips by gently swirling the flask for about 1

minute.

9. Carefully, pour off the hexane into a waste container, without pouring any pieces

of the crushed chips. A small amount of hexane will remain in the flask.

10. Repeat steps 7,8 and 9

11. Heat the flask, with the crushed chips, in the hot water bath for about 5 minutes to

evaporate any residual hexane.

12. Remove the flask from the water bath, allow it to cool and wipe any drops of

water from its outer surface.

13. Determine the mass of the flask and the rinsed crushed chips(W2).

14. Calculate the amount of fat in your sample of chips. Share your results with your

class.


Calculation

Mass of fat in the chip sample: W1-W2= X g

The percent of fat in a sample:

% Fat = ( )

( )

× 100= Z g%

Total fat at bag: X 2 g of chips

Y Weigh of chips in bag

Kilocalories: 1g of fat 9 kcal

X ? kcal

References

David A. Katz. (2013). Determination of Fat in Potato Chips and French Fried Potatoes

https://www.pdffiller.com/en/project/50436156.htm?form_id=25636407

Determining How Much Fat is in Food -Austin Peay State University Department of

Chemistry - CHEM 1021

https://www.apsu.edu/sites/apsu.edu/files/chemistry/SP11_1021_DETERMINING_HO

W_MUCH_FAT_IS_IN_FOOD.pdf

https://www.pdffiller.com/en/project/50436156.htm?form_id=25636407

https://www.apsu.edu/sites/apsu.edu/files/chemistry/SP11_1021_DETERMINING_HOW_MUCH_FAT_IS_IN_FOOD.pdf

https://www.apsu.edu/sites/apsu.edu/files/chemistry/SP11_1021_DETERMINING_HOW_MUCH_FAT_IS_IN_FOOD.pdf


Result Sheet

Calculations

Brand of chips used __________________

Mass of chips _________________ g

Mass of flask and crushed chips _______________g

Mass of flask and the rinsed crushed chips _________________ g

Mass of fat in the chip sample _________________ g

Percent of fat in the chip sample _________________ %

Share your results with your class of another brand of chips

Brand of chips Mass of fat in 5 g of chips Percent of fat in the chip sample


Result Sheet

Answer the following

1. How much fat is in one recommended serving of the chips you tested.

2. How do your results compare with the fat content as listed on the label of the

chips?

3. What sources of error may have occurred in this experiment. (Do not include

calculation error.)

4. Why is hexane used to extract the fat from the chips? Why was water not

used?

5. Why was the hexane added in three separate portions and not in one portion?


Determination of protein in milk using formaldehyde

method

‏

Background

On addition of formaldehyde to milk. Aldehyde group and free

amino group present in protein combines together these group exist for

this reaction. Due to that the basic character of the amino group and due

to enters the reaction with formaldehyde → media for the reaction

becomes acidic rather than neutral (due to a produce of carboxylic

acidic group)

When neutralizing the acidity results for formaldehyde addition → we can

estimate the amount of the amine group and there for the protein content of the milk is

determined.

Objective

Determination of protein in milk

Protein (neutral) (Acidic)

Formaldehyde



NaOH 0.1- 0.5 N Corrosive/ irritant

Phenolphthalein (indicator) Harmful/ irritant

Formalin 40% highly flammable

Milk

Method

1- Pipette 5ml of milk in conical flask then add 2 drops of ph.ph.

2- Titer with NaOH until pink color produced

3- Add 2 ml formalin then shake (pink color disappear)

4- Titer by NaOH pink color will appear.

5- Prepare the blank ( 5ml H2O and 2 drops of ph.ph).

6- Titer with NaOH to produced pink color.

Equipment

Conical flask (250ml) Small beaker (50ml)

Pipette (10ml) Measuring cylinder (25-50 ml)

Dropper

Burette and stand


T= test

B= Blank

Calculation

Protein = T-B x factor

Cow milk factor = 1.67gm%

Baffle milk factor = 1.66gm %


Result Sheet


Determination of chloride content in cheese

Background

Sodium chloride is added to cheese to enhance its

taste, and also as a preservative so that some types of

cheese will keep well at room temperature. In the

industrial preparation of certain cheeses, such as

mozzarella, it is important to check that the quantity of salt added is of an optimum

concentration.

Objective

Determine the concentration of chloride ions in cheeses

Principle

Sodium chloride is precipitated in acidic solution with excess silver nitrate; the

excess unreacted silver nitrate is determined by back titration with a thiocyanate

solution.

Before the titration an excess volume of a silver nitrate solution is added to the

solution containing chloride ions, forming a precipitate of silver chloride. The term

„excess„ is used as the moles of silver nitrate added are known to exceed the moles of

sodium chloride present in the sample so that all chloride ions present will react.

Ag+(aq) + Cl–

(aq) → AgCl(s)


The indicator Fe+3

(ferric ion) is then added and the solution is titrated with the

potassium thiocyanate solution. The titrate remains pale yellow as the excess (unreacted)

silver ions react with the thiocyanate ions to form a silver thiocyanate precipitate.

Once all the silver ions have reacted, the slightest excess of thiocyanate reacts with

Fe+3

to form a dark red complex.

Ag+(aq) + SCN–(aq) → AgSCN(s)

Fe3+(aq) + SCN–(aq) → [FeSCN]2+

(aq)

Left flask: before the titration endpoint, addition of SCN-

ions leads to formation of silver thiocyanate precipitate,

making the solution cloudy. Here the solution also takes a

faint yellow color due to the color of the cheese extract.

Centre flask: at the endpoint all the free silver ions have

been precipitated by SCN-. The slightest excess of SCN-

forms a dark red colored complex with theFe3+ ions from

the ferric ammonium sulfate indicator, giving the solution a

slight orange/ red coloration

Right flask: If addition of SCN- is continued past the

endpoint, further ferric thiocyanate

complex is formed and a stronger dark red color results.


Method

1- Weigh accurately a sample of cheese (about 0.5g) into a conical flask.

2- Add 3.5 ml water and heat the flask to about 75oC in water bath for 10 minutes.

3- Add 8.5 ml of standard 0.05 M silver nitrate (in hood).

and add 1.7 ml conc. nitric acid (HNO3) (in hood)

4-Digest the cheese curd by boiling gently for 10 minutes.

5-Cool, filter in conical flask then add about 16.5 ml water.

6-Titrate with standard potassium thoicyanate using iron (III) alum (Ferric alum)

indicator (0.6 ml).

7-The end-point is an dark red tint, which should persist for fifteen

seconds. Record the volume of KSCN as volume.

8- The experiment can be repeated with different cheese for comparison. For each

calculate the percentage of chloride (expressed as NaCl).


Concentrated nitric acid [HNO3-] Corrosive

Silver nitrate [AgNO3], (0.05N) Corrosive

Potassium thiocyanate [KSCN]

Ferric alum [Fe+] indicator

Cheese

Distilled water

Equipment

Conical (Erlenmeyer)flask (50-100ml) Laboratory balances

Volumetric Cylinder Water Bath

Filter Paper Hot plate

Funnel

Pipette 10ml & 2ml

Burette and stand


Calculation

1L 1N of silver nitrate= M.Wt. of sodium chloride

1 ml (0.05N) of silver nitrate=

of NaCl

1 ml (0.05N) of silver nitrate = 0.0029 g of NaCl

(8.5 ml - Titer No.) = ??

Number of grams of sodium chloride = ( )

= Y gm

% NaCl =

( )

× 100= Z g%

References

Determination of Chloride Ion Concentration by Titration (Volhard’s Method).

University of Canterbury- College of Science-Christchurch-New Zealand

http://www.outreach.canterbury.ac.nz/chemistry/documents/chloride_volhard.pdf

If the cheese contain more than 30%

Salt, required add more AgNO3

http://www.outreach.canterbury.ac.nz/chemistry/documents/chloride_volhard.pdf


Result Sheet

Calculate the concentration of sodium chloride in the different types of

cheese as grams of salt per 100 g cheese (% salt).


Determination of Vitamin C in Foods by Iodometric

Assay

Background

Vitamin C, is a water soluble vitamin that is an essential

antioxidant necessary for normal growth and development.‏ It more

properly called ascorbic acid. Deficiency of vitamin C can lead to a

disease called scurvy, which is characterized by abnormalities in the bones and teeth. It is

important to consume it every day, because the body excretes it regularly and can‟t be

stored for later use.

Many fruits and vegetables such as (green peppers, broccoli, citrus fruits,

strawberries, tomatoes and white potato ) contain on vitamin C, that destroy by cooking,

so raw citrus fruits and their juices are the main source of ascorbic acid for most people.

Also the fish and milk contain small amounts vitamin C.

Objective

Determine the amount of vitamin C in different types of juice.

Principle

Vitamin C can be assayed by a redox titration using iodine. As the iodine is added

during the titration, the ascorbic acid is oxidized to dehydroascorbic acid, while the

iodine is reduced to iodide ions.

Recommended daily allowance (RDAs) of vitamin C is = 70mg/day.


Due to this reaction, the iodine formed is immediately

reduced to iodide as long as there is any ascorbic acid present.

Once all the ascorbic acid has been oxidized, the excess iodine

is free to react with the starch indicator, forming the blue-

black starch-iodine complex. This is the endpoint of the

titration.

‏


Iodine I2 (0.1 N), keep in a dark glass bottle(Amber) to protect form light

Standard ascorbic acid 0.1 gm/100 ml

Starch indicator (1%)

+ I2 Oxidation

Reduction

2 I- 2 e- 2 H+ + ++

Ascorbic Acid

(Vitamin C)

Dehydroascorbic Acid

(Oxidized form)

Iodine Iodide

Figure: Redox Reaction


Method 1- Measure 10ml of juice in the flask

2- Add 10 drops of starch, mix well and cover the flask by aluminum foil to prevent

oxidation by atmospheric oxygen.

3- Titer with 0.1 N iodine to obtain → blue color

4- Repaid the experiment and take the average number

Equipment

Conical (Erlenmeyer) flask (250ml) Small beaker (50ml)

Pipette (10ml)

Dropper

Burette and stand


Calculation

1L 1N of iodine (I2) = M.Wt. of vitamin C (ascorbic acid) (179.14g/mol)

1 ml (0.01N) of iodine (I2) =

of ascorbic acid

1 ml (0.01N) of I- = 0.0088 g of ascorbic acid

Titer no. of iodine (I-) = T

No. of grams of ascorbic acid =

= Y gm

% Ascorbic acid =

( )

× 100= Z g%

References

Determination of Vitamin C Concentration by Titration

University of Canterbury- College of Science-Christchurch-New Zealand

http://www2.moh.gov.my/images/gallery/rni/8_chat.pdf

Official Methods of Analysis. 1999. 16th Edition, 5th Reversion, AOAC International,

Gaithersburg, MD, method 967.21.



Result Sheet

Calculations

1. Calculate the average volume of iodine solution used from your concordant

titers?

2. Calculate the moles of iodine reacting.


Result Sheet

3. Share your results with your class of another types of juices

Type of juice G % of vitamin C

4. Which is the type of juice rich with vitamin C ? and which is type have

the least amount of it ?


Total acidity of fruit juices

Background

The acidity of natural fruit juices is the result mainly of their content of organic acids. For

example, most fruits contain the tricarboxylic acid (citric acid) whereas grapes are rich in

tartaric acid & peaches, apricots & plums in malic acids. Both tartaric & malic acids are

dicaroxylic acids.

Objective

To determine the total acidity in various fruit juice samples by titration with alkali

Principle

The acidity of fruit juice may be determined by simple direct titration with 0.1M sodium

hydroxide, using phenolphthalein as an indicator.



Sodium hydroxide NaOH (0.1 M) Corrosive/irritant

Phenolphthalein 1% Harmful/ irritant

Fresh fruit juice ( orange or lemon )

Method

1. Weight 10ml of sample in conical flask & add 25ml distilled water

2. Titrate using 0.1M NaOH and add phenolphthalein as an indicator

3. Calculate the total acidity of your fruit juice.

Equipment

Conical flask (250ml) Small beaker (50ml)

Pipette (10ml) Measuring cylinder (25-50 ml)

Dropper

Burette and stand


Calculation

Calculate the total acidity:

eq . OH (moles) = 0.1 ×vol.ofNaOH (ml) ×10-3

g. citric acid = ( ) -

g. tartaric acid = ( ) -

g. malic acid = ( ) -

% acidity =

References

http://www.hawkinswatts.com/documents/OECD%20fruit%20acid%20determination%2

0method.pdf

https://www.flinnsci.com/media/620683/91263.pdf

http://www.hawkinswatts.com/documents/OECD%20fruit%20acid%20determination%20method.pdf

http://www.hawkinswatts.com/documents/OECD%20fruit%20acid%20determination%20method.pdf

https://www.flinnsci.com/media/620683/91263.pdf


Result Sheet

Calculations

Calculate the total acidity from your concordant titers?


Determination of nicotinic acid in food

Background

Niacin is a water-souluble vitamin, also known as vitamin B3. Niacin is

the generic term for nicotinic acid and nicotinamide with pyridine as the basic

structure. Nicotinic acid and nicotinamide function mainly as precursors of the

co-enzymes NAD and NADP. Thus, nicotinamide has physiologically critical

roles in mitochondrial respiration and in the metabolism of carbohydrates, lipids, and

amino acids.

Nicotinic Acid

(pyridine 3-carboxylic acid)

Nicotinamide

(pyridine 3-carboxylic amide)

Figure: Structural formula of niacin forms

Clinical evidence of niacin deficiency includes fatigue, poor appetite, diarrhea,

irritability, headache, emotional instability and possible memory loss. These may lead to

changes in the skin, mucosa of the mouth, stomach and intestinal tract and the nervous

system. These changes are called “pellagra”, which means “raw skin” and are most

pronounced in the parts of the skin exposed to sunlight. Other signs and symptoms

include dizziness, vomiting, constipation or diarrhea, and inflammation of the tongue and


gastric mucosa. The neurological symptoms can include fatigue, sleeplessness,

depression, memory loss and visual impairment. If untreated, pellagra is ultimately fatal.

Important sources of preformed niacin include beef, liver, fish, peanuts and other

nuts, whole grains and whole-meal wheat flour. In general, food rich in protein, with the

exception of tryptophan-poor grains, can satisfy some of the requirement for niacin.

Human milk contains a higher concentration of niacin than cow‟s milk. Besides dietary

niacin as a source for the synthesis of NAD, it may also be synthesized in the liver from

tryptophan, an essential amino acid.

Objective

Determine the amount of nicotinic acid in dried yeast

Principle

Nicotinic acid is pyridine-3-carboxylic acid, and can be determined by direct titration

with carbonate-free 0.1 N sodium hydroxide using phenol red or phenolphthalein as

indicator.


Sodium hydroxide [ NaOH ] (0.1 N)

Yeast

Distilled water

Phenol red or phenolphthalein


Method

1- Weigh accurately about 2g of sample.

2- Grind thoroughly in a mortar with about 10 ml of distilled water

3- Centrifuge at 3000 rpm for 10 min.

4-Transfer supernatant into conical flask for titration

3- Add about 2-3drops of either phenol red or phenolphthalein.

4- Titrate with 0.1 N NaOH until the end point is reached.

Equipment


Dropper Burette and stand

Mortar

Phenolphthalein is a

complex organic dye that is

colorless in acidic solutions

and pink in solutions that are

slightly alkaline, or basic


Calculation

1L 1N of NaOH = M.Wt. of nicotinic acid (123.11 g/mol)

1 ml (0.01N) of NaOH =

of nicotinic acid

1 ml (0.01N) of NaOH = 0.0123 g of nicotinic acid

Titer no. of NaOH = T

No. of grams of nicotinic acid =

= Y gm

% Nicotinic acid =

( )

× 100= Z g%

References

Benelux. L., (2012) Scientific Opinion on the safety and efficacy of niacin

(nicotinic acid and nicotinamide) as a feed additive for all animal species based

on a dossier. European Food Safety Authority Journal 10(7):2788




Result Sheet

.

Calculations

Calculate the weight of nicotinic acid in yeast as G% and mg%


Determination of Tannins in Tea

Background

The word tannin is very old and reflects a traditional technology.

"Tanning" (waterproofing and preserving) was the word used to describe

the process of transforming animal hides into leather by using plant extracts

from different plant parts of different plant species. Many food products

contain tannins in their consumable forms e.g.:

• Tea, Cocoa and Walnuts

• Unripe fruits (apples, cherries, strawberries, bananas)

• Plant parts containing tannins include bark, wood, fruit, fruit pods, leaves, roots,

and plant galls.

One of the most satisfactory definitions of tannins was given by Horvath (1981): "Any

phenolic compound of sufficiently high molecular weight containing sufficient hydroxyls

and other suitable groups (i.e. carboxyl‟s) to form effectively strong complexes with

protein and other macromolecules under the particular environmental conditions being

studied". Tannins can complex with: Proteins, starch, cellulose and minerals.

Tannins are phenolic compounds that precipitate proteins. There is some confusion

about the terminology used to identify or classify a substance as tannin, in fact.

Astringency is the contracting or drying taste, which results from coagulation of the


proteins of saliva and the mucous epithelium of the mouth, causing a reduced lubricant

action.

Objective

Determine the tannic acid concentration in different types of tea.

Principle

Tannins are water-soluble so they are extracted from tea by boiling with water.

Ferric chloride reagent gives a green-blue color with tannins under acidic conditions.

The color is measured spectrophotometrically at 540 nm and compared with the color

obtained with a standard tannins solution.

Chemical & Material Hazards Tannic acid solution, 0.2 g/100 ml irritation

ferric chloride reagent irritation

Tea (red- green) Distilled water

Equipment

Beaker (100-200 ml) Laboratory balances

Volumetric flask (100ml) Vortex mixer

Pipette 1ml & 5ml Hot palate

Volumetric Cylinder Spectrophotometer or colorimetric

Filter Paper Cuvette

Funnel Test Tube

Conical (Erlenmeyer)flask (100ml)

Method


B. Preparation of tannic acid(unknown solution)

1- Weigh accurately 0.5g of tea.

2- Add 75ml of water and boil for 30min.

3- Filter in a 100ml-measuring flask and complete to volume with water, Shake well to

mix (use it as unknown).

C. Determination of tannic acid

1- Take 0.5ml of unknown solution; add 0.5ml of ferric chloride reagent and 4ml of

water and mix.

5- The standard is prepared by adding in a tube 0.5ml of standard, 0.5ml of

reagent and 4ml of water and mix.

6- Read the absorbance of unknown and standard against blank at 540 nm

Calculation

The concentration of the tannic acid in tea by the equation as follow.

=

Reference

Salunkhe, D. K., & Chavan, J. K. (1989). Dietary tannins: consequences and remedies.

CRC Press.‏


Result Sheet

* Fill the table with your results

* Determine the concentration of the tannic acid in tea samples and which is type

have the least amount of it ?

Sample Concentration

(Conc.)

Absorbance

(Abs( Red tea

Green tea

Standerd


Estimation of water content in cow’s milk

Background

The quantities of the main milk constituents can vary considerably

depending on the individual animal, its breed, stage of lactation, age and health

status. The average composition of cow‟s milk is shown in table (1).

Table (1): composition of cow’s milk

Main constituent Range %

Water 85.5 –89.5

Fat 2.5 –6.0

Proteins 2.9 –5.0

Lactose 3.6 –5.5

Minerals 0.6 –0.9

Objective

Estimation of water content in milk

Principle

Water is the main constituent of milk. The water can be easily

extracted from the sample, and therefore determined, by using acetone. This

is because: acetone is miscible with water and both have lower boiling

points which mean they will be evaporated before any other major components such as

lipids, proteins, carbohydrates and minerals.


Method

1. Pipette 5ml of milk into beaker and weight it = (X1)

2. Add 1ml acetone and heat to evaporate the milk to dryness on a hot plate

3. After complete evaporation of water, weigh the crucible again (X2)

Calculation

Weight of water= weight of crucible with milk (X1) –weight of crucible with dry milk

(X2)

Water % = ( )

Reference http://www.ilri.org/InfoServ/Webpub/Fulldocs/ILCA_Manual4/Milkchemistry.htm http://en.wikipedia.org/wiki/Acetone

http://www-unix.oit.umass.edu/~mcclemen/581moisture.html

Chemical & Material Hazards 0.1 M NaOH Corrosive/irritant

Acetone Flammable/Toxic

Milk

Equipment

Small beaker (50ml) Hot plates

Pipette (1ml & 5ml)

http://www.ilri.org/InfoServ/Webpub/Fulldocs/ILCA_Manual4/Milkchemistry.htm

http://en.wikipedia.org/wiki/Acetone

http://www-unix.oit.umass.edu/~mcclemen/581moisture.html


Result Sheet

Calculations

Documents

Contents 314 (new).pdf · Contents # Title Page 1 ... Phenol-Sulfuric Acid Colorimetric Method 11 ... as wheat bran or corn bran, xylose should be used to construct the standard curve