fabioclass

HOW TO TEST FOR FOOD SUBSTANCES


HOW TO TEST FOR FOOD SUBSTANCES

The chart below represents the tests for various classes of food substances such as starch, protein, simple sugars, reducing sugars, fats and oil and water.







1. HOW TO TEST FOR PROTEINS IN FOOD

(a) The Biuret’s test.

Process
i. Take a small quantity of milk or egg white solution
ii. Add 1cm of protein and sodium hydroxide and 1% copper (11) solution in drops
iii. Shake the mixture after each drop.
iv. Do not heat

OBSERVATION
The mixture will turn purple or violet colour.

INFERENCE
Protein is present

(b) Millon’s test

i. Put 3cm of protein food inside a test tube, e.g. fresh egg white
ii. Add 3cm of Millon’s reagent
iii. Warm the mixture in a water bath for few minutes
iv.
v.
xi.
xiv.
xv.

OBSERVATION
A red precipitate would appear

INFERENCE

Protein is present



(c) XANTHOPROTEIC TEST

i. Put 2cm of egg white or milk solution in a test tube
ii. Add about 1cm of concentrated trioxonitrate (v) acid and 3cm of ammonium hydroxide solution
iii. Heat the solution
iv. Allow it to cool down

OBSERVATION

A white precipitate forms, which turns yellow on heating. On cooling the content after adding excess NH4OH, the solution becomes orange in colour

INFERENCE
Protein is present






2. FOOD TEST FOR STARCH

I. collect any starch material like bread or yam
II. Add a few drops of dilute Iodine solution

OBSERVATION
I. The colour will change to blue-black
INFERENCE
Starch is present


3. FOOD TEST FOR SIMPLE SUGARS e.g. glucose and fructose

i. Put a small quantity of glucose solution in a test tube
ii. Add 2% Benedict solution
iii. Boil the mixture for 4-6 minutes

OBSERVATION

A brick-red or orange precipitate is seen

INFERENCE
Glucose is present








4. FOOD TEST FOR REDUCING SUGARS e.g. sucrose, lactose or maltose

i. Put a small quantity of sucrose solution in a test tube
ii. Add a few drops of Benedict’s solution or Fehling solution
iii. Add a few drops of Hel:
iv. Boil the mixture for a few minutes
Dilute Hcl and boiling will help to hydrolyze the sucrose to simple sugars e.g. glucose

OBSERVATION
A yellow precipitate is observed

INFERENCE
Sucrose or non-reducing sugars is present



5. TEST FOR FATS AND OILS

(a) Translucent test
i. Drop oil on a spot on a filter paper
ii. Observe the spot against a source of light
OBSERVATION
The drop of oil becomes more translucent. Which means it allow more light to pass through it when held in front of it

INFERENCE
The translucency shows the presence of fats and oils


(b) SUDAN (iii) TEST

i. Add a few drops of Sudan (iii) solution to in a test tube
ii. Then boil the solution
OBSERVATION
i. A red colouration appears before boiling.
ii. A black precipitate is form on boiling

INFERENCE

Fats and oil is present


(6) TEST FOR WATER
i. Dip a blue, dry cobalt chloride paper in a food item
OBSERVATION
The colour of the paper changes from blue to pink

INFERENCE

Water is present





agricultural biology topics
You can read some of most interesting topics below
Agricultural biology topics


HERE YOU WILL FIND EVERY AVAILABLE TOPICS ABOUT AGRICULTURAL SCIENCE AND BIOLOGY. AND THE LINKS TO THEIR VARIOUS SOURCES.

1. DEVELOPMENT OF AGRICULTURE
2. IMPORTANCE OF AGRICULTURE
3. SUBSISTENCE AGRICULTURE
4. COMMERCIAL AGRICULTURE
5. PROBLEM OF AGRICULTURAL DEVELOPMENT
6. SOLUTIONS TO POOR AGRICULTURAL DEVELOPMENT
7. AGRICULTURAL LAWS AND REFORMS
8. ROLES OF GOVERNMENT IN AGRICULTURAL DEVELOPMENT
9. AGRICULTURAL POLICIES
10. PROGRAM PLANNING IN AGRICULTURE
34.
FORESTRY
35. WILDLIFE CONSERVATION
36. FACTORS AFFECTING LAND AVAILABILITY
37. TOPOGRAPHY
38. SOIL
39. BIOLOGICAL FACTORS
40. SOCIAL-ECONOMIC FACTORS
41. ENVIRONMENTAL FACTORS AFFECTING AGRICULTURAL PRODUCTION
42. CLIMATIC FACTORS AFFECTING AGRICULTURAL PRODUCTION
43. TEMPERATURE
44. RAINFALL
45. WIND
46. SUNLIGHT
47. SOLAR RADIATION
48. BIOTIC FACTOR AND AGRICULTURAL PRODUCTION
49. PESTS
50. BIRDS
51. DISEASES
52. SOIL MICRO-ORGANISMS
53. SOIL PH
54. ROCK FORMATION
55. IGNEOUS ROCK
56. SEDIMENTARY ROCKS
57. METAMORPHIC
58. SOIL AND ITS FORMATION
59. FACTORS OF SOIL FORMATION
60. LIVING ORGANISM
61. PARENT MATERIALS
62. SOIL FORMATION TOPOGRAPHY
63. PROCESS OF SOIL FORMATION
64. WEATHERING
65. PHYSICAL WEATHERING
66. CHEMICAL WEATHERING
67. PRESSURE
68. WATER
73. BIOLOGICAL WEATHERING
74. CHEMICAL AND BIOLOGICAL COMPOSITION OF THE SOIL
75. SOIL WATER
76. MICRO AND MACRO NUTRIENTS
77. SOIL MICRO ORGANISM
78. PROPERTIES OF SOIL
79. SOIL STRUCTURE
80. SANDY SOIL
81. CLAY SOIL
82. LOAMY SOIL

83. SOIL TEXTURE
84. IDENTIFICATION OF SOIL TYPES THROUGH EXPERIMENTS
85. RETENTION OF WATER BY VARIOUS SOIL TYPES
86. DETERMINATION OF SOIL PH REACTION
87. COLORIMETRIC DETERMINATION OF SOIL PH LEVEL
88. PH SOIL TEST
89. PLANT NUTRIENTS
90.
MACRO NUTRIENTS IN GENERAL
112.
THE MAINTENANCE OF SOIL FERTILITY
113. CROP ROTATION
114. APPLICATION OF ORGANIC MANURES
115. FARM YARD MANURE
116. APPLICATION OF INORGANIC MANURE

117. LIMING
118. FARMING PRACTICES
119. BUSH BURNING
120. CLEARING

121. FERTILIZER APPLICATION
122. ORGANIC MANURING
123. FARM YARD MANURE

124. HUMUS
125. COMPOST
126. CROP ROTATION
133. FARM POWER AND MACHINERY
134. SOURCES OF FARM POWER
135. HUMAN SOURCE
149.
PLOUGHS
142.
FIELD MACHINES
157.
PLANTERS
164.
SIMPLE FARM TOOLS
165. AGRICULTURAL MECHANIZATION
166. THE CONCEPT OF MECHANIZATION


oppurtunities

ADVANTAGES AND DISADVANTAGES OF MECHANIZATION

ADVANTAGES OF MECHANIZED AGRICULTURE Farm mechanization has the following advantages 1. TIMELINESS OF OPERATION farm mechanization ensure...

popular post of all time