food analysis subject notes

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ANALYSIS OF FERMENTATION PRODUCTS OF
SPIRITS
Presented by:
M.B.Rahul Reddy
Parma. Analysis
J.S.S.C.P, MYSORE -
15
Facilitator:
J.C.Thejaswini,
Assist. Professor,
J.S.S.C.P,
Mysore.

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INTRODUCTION TO SPIRITS:
 Spirits are produced by the distillation of fermented liquors
(distilled ethanol) such that most of the alcohol and various
other volatile substances pass over into the distillate.
 Spirits will not undergo microbial spoilage due to the high alcohol
content.
 Spirits of commercial importance are Brandy, Gin, Rum, Whisky
and Vodka.

4. LEGISLATION:
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 According to section 3(4) of the Food & Drug act 1955, say
that a minimum of 65% proof spirit must be there in
preparations like whisky, rum, gin, vodka and brandy

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PRINCIPLE CONSTITUENTS OF SPIRITS:
 As spirits are produced by distillation they contain less
extractive than other alcoholic liquors.
 They does not contain glycerin, but a high percentage of
alcohol together with certain esters which though present
in small amount are of much importance as they
characteristic flavor of the particular spirit.

7. The principle constituents detected by GLC in potable spirits
are listed below:
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ALCOHOLS ACIDS ESTERS ALDEHYDE,
ESTERS
Methanol
Propan-1-ol
2-methyl propan-
1-ol*
Butan-2-ol
2-methyl butan-1-
ol*
3-methyl butan-1-
ol*
Pentan-1-ol
Pentan-2-ol
Hexan-1-ol
2-phenyl ethanol
Acetic*
Propionic
Iso-butyric
n-butyric
iso-valeric
hexonic
heptonic
octanoic
decanoic
octadeconic
Ethyl formate
Ethyl acetate*
Ethyl isobutyrate
Ethyl isovalerate
Ethyl hexanoate
Ethyl octanoate
Ethyl decanoate
Ethyl
dodecanoate
Ethyl
tetradecanoate
Iso-butyl acetate
Acetaldehyde*
Propionaldehyde
Isoburyaldehyde
Iso-pentanal
Furfural
Acetone
Acetoin
Diacetyl
diethylacetal

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1} BRANDY:
 Brandy is the spirit distilled from wine made of the skins of
selected grape varieties, principally the folle Blanche, a non-
sweet type grown in the charenet area of France. The
resultant wine is slowly distilled in pot stills to produce
brouills, several of which are combined and redistilled.
 The composition of brandy varies widely, but the specific
gravity is usually about 0.94 and the total solids between 0%
and 0.7%. Brandy generally contains 36%-60% alcohol by
volume and is typically taken as an after dinner drink.

9. Composition of Brandy (all results expressed as g per 100
liters ethanol)
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 Total acidity (as acetic acid) 5-100
 Esters 70-100
 Aldehyde(mainly acetaldehyde) 2-35
 Furfural 2-3
 Methanol 20-50
 Diacetyl 0.5-3
 Acetoin 2-8
 Butane 2-3diol 3-10

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2} GIN:
 Gin is a diluted highly rectified spirit, flavored with juniper
berries and extracts from other plants.
 The basic spirit is made from maize and rye grains together
with malted barley or rye. The fermented mass is distilled in a
still. The juniper berries together with materials such as
coriander, cassia and orange peel are added to the still prior to
second distillation.
 *Gin has a specific gravity of about 0.955 and the total solid of
unsweetened gin seldom exceeds 0.1%.

11. Chemical composition:
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Parameter Unit Minimum Maximum
1. Alcohol content °Gay Lussac @
15°C
39 50
2. Total acids, as
acetic acid
mg/100 ml
anhydrous
----------- 10
(100 p.p.m)
3. Esters, as ethyl
acetate
mg/100 ml
anhydrous
----------- 3
(30 p.p.m)
4. Aldehydes, as
acetaldehyde
mg/100 ml
anhydrous
----------- 0.5
(5 p.p.m)
5. Furfural mg/100 ml
anhydrous
----------- 0
6. Higher Alcohols mg/100 ml
anhydrous
----------- 2
(20 p.p.m)
7. Methanol mg/100 ml
anhydrous
----------- 4
(40 p.p.m)
8. Dry extract mg/100 ml
anhydrous
----------- 500
(5000 p.p.m)

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3} RUM:
 Rum is a distilled beverage made from sugar cane by
products such as molasses (molasses is a viscous by
product of the processing of sugar cane into sugar).
 The quality of molasses depends on the maturity of the
sugar cane, the amount of sugar extracted and the
method of extraction and sugar cane juice by a process
of fermentation and distillation.
 * Rum has a specific gravity of about 0.87-0.94 and the
total solids of 0.4%-3.0%.

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Composition of Rum
Jamaican Rum
Age (years) 0 3
Constituents Concentration g/100L
% alcohol 80.1 78.2
Total solids (extract) 0 87.6
Fixed acids 0.9 8.8
Volatile acids 1.1 20.9
Total acids 2.0 (pH=4.9) 29.7 (pH=4.5)
Esters (for years,
erroneously called ethers)
9.7 37.5
Aldehydes 1.9 4.7
Fusel oils (higher
alcohols)
48 66
Furfural 0 1.6
Tannins 0 33.0

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 Grades of rum:
Depending on the location of production they are graded as 1)
light rum 2) gold rum 3) spiced rum 4) flavored rum 5) over
proof rum 6) premium rum
4} VODKA:
 Vodka is a liquor originally produced in Russia and
neighboring countries from potato, rye and possibly maize.
.

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 A common property of vodka production in the US and EUROPE
is the extensive use of filtration prior to any additional
processing, such as addition of flavoring agents. Vodka is
colorless because the distilled vodka is filtered through charcoal
and other media.
 Vodka is a mixed distilled beverage. It is a clear liquid
consisting mostly of water and ethanol purified by distillation,
often multiple distillations from a fermented substance, such as
grain, potatoes or sweet beet molasses.

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5} WHISKY:
 Whisky refers to a broad category of alcoholic beverages that are distilled
from fermented grain. Whisky usually has a specific gravity of 0.94-0.95 the
total solids varies from 0.05%-0.3%.
 Composition of whisky:
Parameter Mature grain whisky Mature malt whisky
Obscuration(%v/v ether) Up to 0.7 0.6-2.0
Total aldehyde (as g
acetaldehyde/100 liters
ethanol)
2-5 6-25
Total esters (as g ethyl
acetate/100liters ethanol)
10-16 37-85
Furfural (g/100 liters
ethanol)
Up to 0.1 1.7-8.5
Total higher alcohols
(g/100 liters ethanol)
70-150 300-450
Total acidity (g acetic
acid/100 liters ethanol)
3.5-8.0 11-28

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 Different analytical tests prescribed for the analysis of spirits by the
Research Committee on the Analysis of Potable Spirits (RCAPS)
are:
1)GLC method
2)Test for alcohol content
3)Test for methanol
4)Test for total solids (extract)
5)Test for acidity
6)Test for esters
7)Total aldehyde
8)Test for furfural

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1} GLC METHOD:
 Although classical methods give useful information on the
components of potable spirits such as total acids, esters and
higher alcohols individual components can better isolated by
gas chromatography (refer to the first table).Standardization of
GLC methods between different laboratories varies.
2} ALCOHOL:
 The alcohol contents of spirits are best determined by direct
distillation of 50mlof sample. By determining the specific
gravity of the distillate at 20˚c or 15.5c after making up to the
original volume. The percentage of alcohol in the sample can
be found by reference to the customs and excise tables.

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Specific
gravity in
air at
15C and
20C
Reading at 60F (15.5C) Reading at 20C, % alcohol
Proof
Spirit %
By
Weight
By
Volume
Proof
Spirit %
By
Weight
By
Volume
0.7904 - - - 175.35 100.00 100.00
0.7936 175.35 100.00 100.00 174.25 98.98 99.37
0.8100 169.13 94.50 96.45 167.77 93.38 95.68
0.8300 159.73 87.11 91..11 158.08 85.89 90.18
0.8500 148.62 79.18 84.78 146.76 77.89 83.75
0.8700 136.16 70.88 77.69 134.16 69.60 76.59
0.8900 122.56 62.38 69.95 120.47 61.12 68.80
0.9800 27.99 12.14 25.83 43.34 20.28 24.88
0.9900 12.53 5.76 7.18 12.44 5.7 7.16
1.000 0.00 0.00 0.00 0.00 0.00 0.00

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 The source of error in measuring the strength of alcohol in
distillates can be done by various types of pyknometer. {A
pycnometer (from Greek: πυκνός (puknos) meaning "dense"),
also called pyknometer or specific gravity bottle, is a device
used to determine the density of a liquid.}.

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 If the total solid matter is small such as in gin and vodka
the alcohol content can be assessed approximately by
determining the specific gravity of the sample .
 But is more accurate to make a suitable correction. The
soluble matter increases the gravity of the sample.
 This difference between the apparent and real alcohol
contents is referred to as the” obscuration”. each 1% of
extract increases the specific gravity by 0.004%.

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 Thus for whisky:
extract( total solids)=0.20%
 Specific gravity of sample at 15.5°c= 0.9565= 64.48%v/v
ps (proof spirit)
 Correction extract = 0.20 x 0.0041 =0.0008
 Spec. gravity of alcohol in sample = 0.9557 =65.4%v/v ps

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 If the sample is measured at temperature other than 15.5°c a
correction of 0.0006 per ° c should be applied.
 OBSCURATIONS OF SPIRITS:
SPIRIT OBSCURATION
Brandy 2-4
Gin Usually negligible
Rum 2-6
Whisky 0.1-1.5
Vodka Less than 1

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4} TOTAL SOLIDS:
 Wash the residue in the flask after the distillation of the alcohol into
a weighed platinum dish. Evaporate on the water bath and then in
the 100° C oven. Cool and weigh ash. Ignite the residue for the
determination of extract at a dull red flame.
5} ACIDITY:
 The acidity in spirits is determined by the determination of end
point with the help of a PH meter or a suitable visual indicator
like phenolphthalein.

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 TOTAL ACIDITY: To 300ml water adjust to PH 7.8 add 50ml
of sample and titrate to ph 7.8 with 0.1M sodium hydroxide
(titre v1 ml) calculate the total acidity as both acetic acid and
tartaric acid.
 FIXED ACIDITY: Evaporate 50ml of sample to dryness in a
flat shallow dish on a boiling water bath and heat the residue.
Then stir in 50ml of water (ph 7.8) and titrate to ph 7.8 with
0.1M sodium hydroxide (titre v2 ml). Calculate the fixed acidity
as tartaric acid.

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VOLATILE ACIDITY: from the above titers
 Volatile acidity (g acetic acid/100 liters of alcohol in sample)
=1200(v1-v2)/s..
 Where S = the percentage of alcohol (v/v) in the sample.
 Using this method the committee reported the following results
whisk (4 samples) 25-28; rum (4samples) 9-63; brandy (3samples)
21-38.
 Using GLC showed that rum contained more volatile acids than
whisky or brandy.
 Also the proportion of acetic acid in the volatile acids tended to be
higher in whisky and rum than in brandy.

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6} ESTERS:
 Principle: the esters are hydrolyzed with alkali and the
excess is titrated with acid.(simple acid base titration)
 Procedure: fill a 250ml volumetric flask to the mark with the
sample at 20°C and transfer to a distillation flask with the aid
of 20ml water. Collect nearly 250ml of distillate in the same
flask and make up to volume at 20°C with water. Then take 2
flasks (300-500ml) fitted with reflux condensers. To one flask
add 100ml water. Then treat both sample and blank as follows
 add 3 drops phenolphthalein and titrate with 0.1M sodium
hydroxide. Then add exactly 10.0 ml of the alkali.

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 Add glass beads and heat under reflux for one hour. Cool
rapidly and titrate with 0.05M (0.1N) sulphuric acid. Let the
difference in titrate be V ml.
 Using this method the committee reported the following
results. Whisky ( 5 samples) 26-36; rum (6 samples ) 8-76;
brandy ( 5 samples) 73-84.

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3} METHANOL:
 Minute traces of methanol are naturally present in spirits.
 Formerly much large amounts were occasionally found due
to adulteration. A colorimetric procedure is described.
 The methanol is separated from most of the ethanol by
fractional distillation.
 Methanol is oxidized by acid permanganate to formaldehyde,
which reacts with chromotropic acid (OH)2C10H4(SO3)2 and
the red colour formed is measured at 575nm.

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7} TOTAL ALDEHYDES:
Special reagents:
A) Mix 15 g potassium metabisulphate (k2S2O3) with 70ml
con.Hcl and dilute to a liter with water.
B) Dissolve 200g sodium phosphate (Na2PO4) and 4.5 g
EDTA in water and dilute to a liter.
C) Dilute 250ml con Hcl to one liter with water
D) Mix 100g boric acids with 170 g sodium hydroxide add
water to dissolve and dilute to one liter.

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Procedure:`
 Boiled and cooled water in a large flask. Add 10ml of A and by pipette
50ml of a distillate of the sample containing about 50% alcohol, stopper
swirl to mix and allow to stand for 15 minutes.
 Then add 10ml of B, swirl to mix and allow to stand for 10 minutes in a
Stopered flask.
 Add 10ml of C and 10ml fresh starch solution and swirl to mix. Add
enough iodine (approx. 0.1M) .the end point is appearance of faint blue
colour.
 Add 10ml of D and titrate the liberated bisulphate with 0.05M iodine to
the same faint blue end point.
 Total aldehyde (including acetal) = titre x M x 22.0 x 100/ml sample

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 Results whisky (4samples) 10.2-15.2; rum (4samples) 22.6-
31.2; brandy (3samples) 22.1-29.6
 8} FURFURAL:
is a industrial chemical compound derived from a variety of
agricultural products, it is a aromatic aldehyde with a ring
structure C5H4O2 .

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 Principle: the amount of furfural is based on the pink the
pink colour produced with aniline acetate.
Special reagents:
 Aniline acetate solution: mix equal volumes of redistilled
aniline, glacial acetic acid and water, prepare as required.
 Standard furfural solution: from 1% solution of furfural in
50% alcohol prepare 0.1%, 0.01% and 0.001% solution,
also in 50% alcohol.

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Method:
 Place 10ml of sample distillate containing 50% alcohol in a
colorimeter tube. Prepare similar tubes containing 0.5ml upwards of
the standard 0.001% furfural solution.
 The volume in each case being made up to 10ml with 50% alcohol.
 Add 0.5ml aniline acetate solution to each tube and mix. Match the
pink colour of the sample against the standards exactly 15 minutes
after adding the reagent.
 A standard disc for furfural is available for use with the Lovibond
comparator (instrument used to match both the colors)

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References:
 Food analysis by David Pearson – page no: 334-346.
 www.wikipedia.search

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