1. SATISH PRADHAN DNYANASADHANA COLLEGE- THANE-400604
DEPARTMENT OF CHEMISTRY
INTRODUCTION TO
FOOD CHEMISTRY by
Dr.G.R.Bhagure
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2. Contents Introduction to food chemistry (10L)
2.1.1 Food processing and preservation: Introduction, need
Methods of food processing and preservation
Chemical methods :
1)Use of chemicals as preservatives(volatile fatty acids in Bakery products, Benzoic acid in jam and jellies, Acetic acid in pickles, Lactic acid in poultry, sulfite in fruits)
2)Role of pH on the preservation of foods
Physical methods :1) Pasteurization 2) Irradiation
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3. Examples of Food Processing
Chopping
Mixing
Homogenizing
Cooking
Pasturing
Emulsifying
Spary drying
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4. Need of Food Processing1
Prevent, reduce and eliminate infestation of food with microbes 2
Prevent microbial growth or toxin productions by microbes 3
Stop or slow down deteriorative chemical or biochemical reactions 4
Maintain or to improve nutritional properties of food 5
Increase storage stability or shelf life of food 6
Make food more palatable and attractive 7
Make food for special group of people
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5. Why foods spoil Yeast Molds Bacteria Enzymes
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6. To avoid / stop Food Spoilage To inhibit growth of bacteria
degradation ---
To avoid / stop Food Spoilage
To inhibit growth of bacteria
Removal of organism
Killing of organism
Inactivating enzymes:
Principles of Food Preservation
technique
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7. Drying Cold Heat Fermentation
Chemicals
&
Radiation
Fermentation
Food Preservation
Is achieved by
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8. Types of Preservatives Natural preservatives
Chemical
preservatives
Physical
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9. Natural preservatives
Sugars,
Salts
acids
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10. Chemical preservatives
Organic
Inorganic
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11. Salicylates, Formic acids Sweeteners: Sacharin, dulcin
Organic
preservatives
Benzoates
Formaldehyde,
Salicylates, Formic acids
Formic acids
Easters,
Hydroxy benzoic acids,
propionic acids,
thiourea,
Sweeteners: Sacharin, dulcin
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12. free Chlorine hypochlorite's,
Nitrates ,
nitrites
sulphates,
sulphorous acids,
borates,
iodates,
free Chlorine hypochlorite's,
peroxides
Inorganic
preservatives
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13. Physical preservatives Pasteurization Irradiation
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14. 1
Chemicals as preservatives
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15. Chemical preservatives
Organic
Inorganic
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16. Sodium Chloride
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17. Sugars
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18. Effective against yeast & bacteria than Mould
Acetic Acid
Effectiveness increases with decrease in pH
Effective against yeast & bacteria than Mould
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19. Benzoic Acid
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20. Benzoic acid Antimicrobial agent Used in acidified fruits
Its ineffective at pH near neutrality
Effectiveness increases with increase in acidity
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21. Sorbic acid & its sodium, pottassium, and Calcium salt
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22. Sorbic acid & its sodium, pottassium, and Calcium salt
Mould & yeast inhibition
Most effective at low pH up to pH 6.5
Its preferred because of its stability, easy preparation, and water solubility
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23. Nitrate & Nitrite
Meat & meat Products
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24. Carbon dioxide Use as solid
(dry ice) to maintain low temperature storage and transportation of food products
Inhibition of growth of microorganism & prevents the spoilage of fruits and vegatables.
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25. Boric acid Less effective against moulds & bacteria
Effective against yeast
Less effective against moulds & bacteria
Use to preserve food products
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26. 2
pH control
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27. Survival of microorganism
pH control
minimum
optimum
maximum
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28. pH 4.6 Prevent the growth and toxin production for pathogens
It is divider between
High acid food and low acid food
High acid food
Peaches ( pH 4.0)
Orange juice ( pH 3.5)
Peaches ( ph 4.0)
Fresh fish (6.3)
Canned green beans (pH 5)
Bread (pH 5.5)
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29. Determination of Boric acid in Food Sample
Food Sample 10 gm
Make it ash by heating
Treat ash with lime water, 2.5 M NaOH and H2SO4
Add mannitol to convert boric acid into strong monobasic boric acid
Titrate this aliquot with standardized M NaOH using Phenolphthalein Indicator
1 Cm3 of 0.2 M NaoH = gm of H3BO3
Determination of Boric acid in Food Sample
This will convert boric acid into free boric acid
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30. REAGENTS AND STANDARDS
D.W. AR grade 99 % reagent
Conditions : IonPac AS18 Analytical or IonPac AG18 Guard
Eluent: 35mM KOH Time: 0-20 min.
Flow Rate Rate: 1.0 cm3 /Min
Temperature: 30 OC
Injection : 25 ul, Run time: 20 min.
Determination of Sodium Benzoate in Food Sample
Preparation of Standard Solution:
10000mg /L of Benzoate Standard Solutions: Dissolve gm sodium benzoate in 100 cm3 of D.W.
Preparation of Sample Solution:
5 gm of sample is dissolved in D.W. and homogenized for 10 min.
The extraction of sodium benzoate is made with methanol. The mixture is mixed with 35 cm3 of methanol
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31. Physical preservatives Pasteurization Irradiation
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32. Pasteurization of Milk
Temperature of Pasteurization
Holding time
Total number of Bacteria
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33. Irradiation of Fruits and Vegetables
In 1991 the Atomic Energy Act was amended and Atomic Energy (Control of Irradiation of Food) rules were notified. In 1994, Government of India amended Prevention of Food Adulteration Act (1954) Rules and approved irradiation of onion, potato and spices for domestic market. Additional items were approved by notifications published in 1998 and 2001
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34. Irradiation of Fruits and Vegetables
Beef and Pork.
Crustaceans (e.g., lobster, shrimp, and crab)
Fresh Fruits and Vegetables.
Lettuce and Spinach.
Poultry.
Seeds for Sprouting
Shell Eggs.
Shellfish - Molluscan.
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35. Irradiator RCC SHIELD RCC SHIELD DLEIHS X-Rays, Gamma Rays (CO 60),
Electron
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36. Irradiation of Fruits and Vegetables
Disinfestations of insect pests in stored products
Disinfestations of quarantine pests to overcome international trade barriers
Delay in ripening and senescence in fruits and vegetables
Inhibition of sprouting in tubers, bulbs and rhizomes
Destruction of microbes responsible for food spoilage
Elimination of parasites and pathogens of public health importance in food
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37. Type of food sample
doses and purpose
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38. Small onions, garlic, ginger Insect disinfestations
0.03
0.09
Sprout Inhibition
Potato
0.05
0.15
Small onions, garlic, ginger
Rice
0.25
1.0
Insect disinfestations
Wheat aatta &Rava
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39. Insect disinfestations Shelf life extension & pathogen control
pulses
0.25
1.0
Insect disinfestations
Dried sea food
Dried dates .
Mango
0.75
Shelf life extension
Meat & meat products
2.5
4.0
Shelf life extension & pathogen control
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40. Study and Analysis of Food Products:
Coffee
MilK
Honey
Tea
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41. Proteins (Casein & Albumin ) 2.9- 5.0 % Carbohydarates (lactose)
Composition of Milk
Proteins (Casein & Albumin ) %
Water %
Total Solids %
Fat %
Carbohydarates (lactose) %
Minerals %
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42. Proteins (Casein & Albumin ) 2.9- 5.0 %
Nutrients in Milk
Proteins (Casein & Albumin ) %
Casein ,globulin Lacto albumin
The above three proteins contains some 20 amino acids
Carbohydarates %
(lactose)
Minerals %
Na,K,Ca,P,Cl, &
S in substantial quantity
Mg,Cu,Fe,Zn,I in Smaller quantity
Vitamins
Vit.A, thiamin, Ascorbic acid, D,E
Riblflavin, niacin,pridoxine,enzymes,
Amylase, lipase, galactase,
And reductase
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43. Types of Milk Fat free milk Whole milk Lactose free milk 3.5 % fat
Reduced fat milk
2 % fat
Low fat milk
1 % fat
Organic milk
Lactose free milk
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44. Analysis of Milk Determination of Lactose Cole’s Ferricynide method
Principle
Standardization
Estimation
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45. Principle The redox reaction involved during estimation of Lactose.
This method includes addition of lactose to hot solution of Ferricynide under alkaline condition.
During the course of titration to hot Ferricynide solution lactose is added .
Lactose is oxidized to lactic acid and ferrocynide is reduced to ferric cyanide.
Redox reaction continues to till entire Ferricynide is consumed.
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46. Standardization
Definite volume of 1 % potassium ferrocynide is taken in evaporating dish and titrated under boiling conditions against standard lactose solution by using methylene blue as an indicator
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47. Estimation
Preparation of Milk Sample: definite quantity of milk is taken in 250 ml of beaker. 5ml of AR grade acetic acid is added and is stirred . The proteins get coagulated, are separated using what man filter paper no.42
Definite volume of 1 % potassium ferrocynide is titrated against sample solution using methylene blue as an indicator under boiling conditions
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48. Study and Analysis of Food Products: Honey
2.1.4 Study and analysis of food products: Honey (1 L)
Study and analysis of food products: Honey
Composition
Analysis of reducing sugars in honey – Lane Eynon Method

49. COMPOSITION OF HONEY Water 17.2 % 38.19 % High Sugars 1.49 % Dextrose
Laevulose
38.19 %
Dextrose
31.28 %
Sucrose 1.3 %
Maltose 7.3 %
Others
3.24 n%
High Sugars 1.49 %
Water
17.2 %
Honey
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50. Analysis of reducing sugars in honey – Lane Eynon Method
Principle:
Methylene blue is used as internal indicator for detection of end point while titrating fehlings solution with reducing sugars. Copper ions (II) from Fehlings solution get reduced to Copper ions (I) in alkaline condition, when all Copper ions (II) reduced, added sugars reacts with Methylene blue converting it to leuobse, for minting Copper ions (I),the titration is carried out in boiling condition
Chemicals:
Fehlings solution-A Copper Sulphate
Fehlings solution-B KOH + Sodium tartarate
Methylene blue
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51. Standardization of Fehling's solution
Equal quantity / volume of Fehling's solution-A & B is taken in evaporating dish and titrated under boiling conditions against standard Glucose solution by using methylene blue as an indicator, added glucose reacts with Methylene blue converting it to leuobase.
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52. Estimation of Reducing sugars
Inversion: During hydrolysis non- reducing sugars re converted to reducing sugars (dextrose and fructose)
Estimation of Reducing sugars
Before Inversion
After Inversion
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53. Estimation of Reducing sugars before Inversion
Definite volume of Fehling's solution-A & B is taken in evaporating dish and titrated under boiling conditions against honey solution by using Methylene blue as an indicator.
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54. Estimation of Reducing sugars after Inversion1
Definite volume of honey sample is taken in round bottom flask and reflux for 90 minutes in presence of 5 N HCl on boiling water bath. 2
After refluxing acidity is neutralized by adding sodium carbonate . 3
Definite volume of Fehling's solution-A & B is taken in evaporating dish and titrated under boiling conditions against inverted honey sample solution by using methylene blue as an indicator.
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55. 2.1.5 Study and analysis of food products: Tea (1 L)
Components in Tea (Polyphenol, amino acids, enzyme pigment, volatiles, minerals)
Types of Tea (Black, Green & Mixed Tea)
Estimation of Tannin in Tea (By potassium permanganate method)
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56. Study and Analysis of Food Products: Tea
Protein
24.50 %
Caffine
4.70 %
Tannin
26.13 %
Ash
8.37 %
Essential oil
0.68 %
Water
9.51 %
Tea
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57. Types of
Tea
Black Tea)
Green Tea
Mixed Tea
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58. Black Tea
Tea leaves obtained from plant Camellia
(China, India Srilnka and Kenya)
Tea leaves are plucked and weathered to reduced moisture , whole levees re collected & rolled.
Finally levees are oxidized & dried
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59. Green Tea
Tea leaves obtained from plant Camellia
(China, India Srilnka and Kenya)
Tea leaves are harvested and quickly heated by pan firing or stemming and dried to prevent to much oxidation
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60. Mixed Tea Black Tea or green tea is prepared by above methods
Black Tea or green tea is mixed with various ingredients to give typical flavour and aroma to it this is called s mixed tea
For Ex. Flowers ,herbs, spices,
Flavored Tea ,
Cardamom Flavored Tea ,
Masala Tea
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61. Method
Estimation of Tannin in Tea (By potassium permanganate method)
Principle
Tannin in Tea can be estimated by determining its oxidisbility by potassium permanganate solution.
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62. Chemicals
Oxalic acid, std.potassium permanganate solution, indigo solution, gelatin solution, acidified sodium chloride
Sample preparation
Boil 5-10 gms. of tea sample for 30 min. with 50 cm3 of distilled water, cool, filter and dilute to 250 cm3 with distilled water
PART-A
Take 10 cm of above solution, add 25 cm3 of indigo solution and 750 cm3 of distilled water and titrate against std.potassium permanganate solution till the colour becomes bright yellow or faint pink let this Reading = A cm3
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63. PART-B
Mix 100 cm3 of clear infusion of tea with 50 cm3 of gelatin solution.
Step-1
Add 100 cm3 of acidified sodium chloride & 10 gm of powdered kaolin ,shake several mints in stoppered bottle and allow to separate .
Step-2
Take 10 cm3 of above filtrate with 25 cm3 of indigo solution and 750 cm3 of distilled water and titrate against std.potassium permanganate solution till the colour becomes bright yellow or faint pink let this Reading = B cm3
Step-3
The volume potassium permanganate solution required for oxidation of tannin =( B-A) = C cm3
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64. 2.1.6 Study and analysis of food products: Coffee (1 L)
Composition (Caffeine, anti-oxidants, furan, diterpene, etc)
Determination of Caffeine content (Bailey Andrew Method)
Chicory in Coffee (Qualitative method)
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65. Raw Coffee Caffeine Fat Water 8-12% Reducing Sugar 5.8-7.8 % Cellulose%
Fat %
Reducing Sugar %
Cellulose %
Total Nitrogen %
Ash %
Volatiles %
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66. Compounds Contained in Coffee
Antioxidants
Diterpenes
Acryl amide
Furan
Ochartoxin
Caffeine
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67. Determination of Caffeine content (Bailey Andrew Method)
Chemicals
MnO2 powder, H2SO4Chloroform KOH, Vaseline, NaOH, Methyl Red Indicator
Apparatus
Erlenmeyer flask, Reflux Condenser, Filter paper, 50 cm3 of Volumetric flask , 125 cm3 Separatory funnel, Kjeldahals flask, distillation flask, burette ,graduated pipette
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68. 1
Weigh bout 5 gm of sample and transfer it in to Erlenmeyer flask, add 3 gm MnO2 powder & 100 cm3 of distilled water. 2
Weigh the flask with content and boil under reflux condenser for 45 min. shaking occasionally. 3
Cool & Weigh the flask again and add water till original weight is obtained 4
Mix well & filter through dry filter paper in directly 50 cm3 of volumetric flask till it completely filled up to mark. 5
Transfer the above 50 cm3 of solution to sepertory funnel, add 4 cm3 of H2SO4(1:9 cm3) to it 6
Extract with five 10 cm3 portions of chloroform shaking vigorously 1 min. for each extraction.
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69. Add 5 cm3 of KOH solution , shake vigorously for 1 min7
Let the emulsion break ,then drain chloroform in to 125 cm3 separator . 8
Add 5 cm3 of KOH solution , shake vigorously for 1 min 9 10 11 12
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70. Determination of Caffeine content (Bailey Andrew Method)
Weigh accurately about 5 gm of sample, transfer to a 250 ml Erlenmeyer
flask, add 3 gm of magnesium oxide and 100 ml of distilled water.
Weigh the flask with contents and boil under a reflux condenser for 45 minutes shaking occasionally.
Cool and weigh the flask again and add water till the original weight is obtained.
Mix well and filter through a dry filter paper directly into a 50 ml graduated flask until exactly 50 ml of the solution (equivalent to half the quantity of the sample taken for test) is obtained.
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71. Transfer the solution to a 125 ml separator
Transfer the solution to a 125 ml separator. Wash the graduated flask with 2 ml of water and add the washings to the separator.
Add 4 ml of dilute Sulphuric acid (1: 9). Extract with five 10 ml portions of chloroform shaking vigorously for 1 minute for each extraction.
Let the emulsion break, then drain the chloroform into a 125 ml separator. Add 5 ml of Potassium hydroxide solution (1%). Shake vigorously for 1 minute,
let the emulsion break and drain the chloroform through a cotton plug into a 100 ml Kjeldahl flask.
Extract the Pot hydroxide solution with 5 ml of chloroform and add to the Kjeldahl flask. To the digestion flask add 1.3± 0.5 gm of potassium sulphate and 40 ± 5 mg mercuric oxide. Rinse down the neck of the flask with 3 ml chloroform
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72. Add 2 ± 0.1 ml conc. sulphuric acid of sp gr.1.84
Place the flask on the digestion rack and concentrate chloroform to about 20 ml. Distill off chloroform.
Add 2 ± 0.1 ml conc. sulphuric acid of sp gr.1.84
digest for 1 hour after the acid begins to boil. Cool and add minimum quantity of water to dissolve the solids.
Cool and place a thin film of vaselin at the rim of the flask. Transfer the digest with a few boiling chips to the distillation apparatus and rinse the flask 5 –6 times with 1–2 ml water .
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73. Place a 125 ml beaker containing a known quantity of standard sulphuric acid (0.05N). Add 6 ml of conc sodium hydroxide solution ( 1+ 2) carefully through the side of the still so that it does not mix, and assemble the distillation apparatus taking care that the dip tube extends well within the standard sulphuric acid solution contained in the beaker.
Mix the contents of the distillation flask and distill until all ammonia has passed over into the standard sulphuric acid. Shut off the heater and immediately detach the flask from the condenser.
Rinse the condenser thoroughly with water into the beaker. Wash the dip tube carefully so that all traces of the condensate are transferred to the beaker.
When all the washings have drained into the beaker, add 2-3 drops of methyl red indicator and titrate with standard sodium hydroxide solution (0.1N).
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74. 486.96 (B-A) N% BY WEIGHT W(100-M)
Carry out a blank determination using reagents in the same proportion without the sample.
(B-A) N% BY WEIGHT W(100-M)
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75. N = Normality of standard sodium hydroxide solution
Where,
B = volume of standard sodium hydroxide used to neutralize acid in the blank determination
A = volume of standard sodium hydroxide used to neutralize the excess acid in the test with the sample
N = Normality of standard sodium hydroxide solution
W = weight in gm of the sample in the aliquot
M = Percentage of moisture in the sample
Note: -
For soluble coffee (instant coffee) the quantity of sample taken fo
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76. Principle:
Chicory is a root and contains inulin, hydrolysis of which gives fructose. Coffee does not contain inulin. Therefore, this method can be used to test the presence of Chicory in coffee.
Reagents:
(a) Neutral lead acetate – Prepare 10% solution in water.
(b) Conc. HCl.
(c) Seliwanoff reagent – Dissolve 0.05 g of resorcinol in 100 ml of 1:2 HCl.
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77. Procedure:
Clarify 25 ml of 2% aqueous extract of the sample with neutral lead acetate and filter. To 5 ml of filtrate add 5 ml of Seliwanoff reagent and 1 ml of conc. HCl. Boil for 2 minutes. Appearance of distinct red colour on standing shows the presence of Chicory in coffee.
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78. Thank you
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