from soil elements to food nutrients · 2018-12-19 · the human body requires about 42 different...
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FROM SOIL ELEMENTS TO
FOOD NUTRIENTS:
Joyce Kinabo
Dept. of Food Science and Technology, Sokoine
University, Tanzania
All forms of life are directly dependent on
plants for food
Plant foods contain almost all of the inorganic
and organic nutrients (minerals, carbohydrate,
protein, fat and vitamins)
Organic phytochemicals that have been linked
to the promotion of good health
The human body requires
about 42 different essential
nutrients
Plants extract elements from
the soil to make the food
nutrients contained in grains,
tubers, roots,
vegetables, and fruits
Therefore, soil is the primary
source of all nutrients for
plants, humans and animals
• Nutrients contained in foods depend on the quantity and chemical forms of the elements present in the soil
• The extent to which plants are able to extract nutrients from the top soil
• Health of top soil is critical for people’s nutrition and health
• Good quality food depends on soil health and agricultural practices.
WHAT DETERMINES SOIL HEALTH?
Soil characteristics:
Texture: proportion of sand, silt and clay
Sandy: low cation exchange capacity (CEC)
Low nutrient holding capacity
High leaching
Low nutrient availability
Clay: High CEC
High nutrient holding capacity
Low nutrient leaching
WHAT DETERMINES SOIL HEALTH?...
Structure: arrangement of soil particles into
aggregates
Large particles:
Large spaces between particles, high water and nutrient
movement resulting into leaching
Very small particles:
Lead to soil compaction, hence enhanced water runoff
Medium size particles:
Allows good space between particles for water, nutrient
and roots movement; less leaching occurs
WHAT DETERMINES SOIL HEALTH?....
Acidity (pH): soil acidity or alkalinity for nutrient adsorption or desorption, precipitation,
mineralization, or immobilization
For example: when the soil is alkaline (pH > 7) solubility of iron and zinc decreases hence become unavailable to the plant
Many nutrients are more available in slightly acid soils (pH 6 – 6.5)
Moisture
Temperature
WHAT DETERMINES SOIL HEALTH?....
Low nutrient contents in plants are due to
inherently low content of such nutrients in soils
and/or low availability due to low solubility
caused by inherent physico-chemical properties
of soils as well as moisture levels
PLANT GROWTH AND DEVELOPMENT
Plants require 16 essential elements as well as
light, heat and water for:
growth and development
synthesis of nutrients
Each plant has an optimum range of
requirements (minimum and maximum)
Each essential element has a specific role to
play
FUNCTIONS OF ELEMENTS IN PLANTS Element Function Effect of Deficiency
Nitrogen Low protein content
Reduction in yield
Phosphorus Stunted growth & Delayed
maturity
Poor seed/grain & fruit
development
Potassium Reduces size & quantity of
fruits and seeds
Iron Chlorosis & reduced dry
matter production and yield
Calcium Poor cell membrane
formation
Zinc Reduced fruit formation in
citrus
Reduced pod filling
(legumes)
LOCATION OF NUTRIENTS IN PLANT FOODS
Roots extract elements from the soil to supply
to the leaves and later used to make the
nutrients, which are then located in various
parts of plants.
However, location of nutrients in the plant and
eventually in the grain, fruit or tuber is not the
same
LOCATION OF NUTRIENTS IN PLANT FOODS...
• A study by Wada & Lott, (1997) on nutrient storage in embryo and aleurone layer of rice showed that: – P, Mg, and K were located in all globoids
– Ca, Mn, Fe, and Zn were present in specific tissues and regions
• Calcium was mainly detected in globoids/granules of the aleurone layer.
• Iron was mostly found in globoids of radicle tissue.
• Zinc was commonly found in globoids of the scutellar epithelium and in provascular tissues of the mesocotyl, coleoptiles, and radicle.
• Manganese was distributed throughout most of the tissues, but was highest in globoids from the coleoptiles tip regions and the plumule.
STRUCTURE OF A RICE GRAIN
• Pericarp - protein, cellulose and hemicellulose
• Tegmen - fatty material
• Aleurone - protein and partially oil, cellulose and hemicellulose
• Endosperm - complex carbohydrates and some proteins
• Embryo - protein and fat
LOCATION OF NUTRIENTS IN PLANT FOODS....
Horvatić, Gačić, & Vedrina-Dragojević (2001)
showed that accumulation of iron, copper,
manganese and nickel in aleurone layer of
maize grain was positively and significantly
correlated with deposition of total dry matter,
total ash and crude proteins.
LOCATION OF NUTRIENTS IN PLANT FOODS
• Micronutrients and
phytochemicals are
located in the bran and
germ
• Starch is located in the
endosperm
Maize grain
ELEMENTS UPTAKE BY AMARANTHS
0
1
2
3
4
5
Mazimbu LITI Fungafunga
0.16 0.24 0.37
3
3.9
4.6
Pe
rce
nta
ge
Nitrogen content
Soil Amaranth
0
0.5
1
1.5
2
2.5
3
3.5
Mazimbu LITI Fungafunga
1.33
2.71
3.17
1 0.9
1.3
mg
/1
00
g
Calcium
Soil Amaranth
0
0.5
1
1.5
2
Mazimbu LITI Fungafunga
0.27
1.02
1.55
0.04 0.2 0.25
mg
/1
00
g
Zinc
Soil Amaranth
CALCIUM, ZINC AND IRON UPTAKE
0
2000
4000
6000
8000
10000
12000
14000
16000
Calcium Zinc Iron
g/k
g
Amaranth Chinese Cabbage Sweet potato Leaves
FOOD PROCESSING
• Food processing and preparation contribute to quality of foods (nutrient content)
• Peeling: most phytochemicals are located in the skin or outer layer of fruits and vegetables (non-leafy); removal of skin or outer layer reduces the amount of phytochemicals
• Milling: the aleurone layer and embryo contain most of the minerals, vitamins and proteins in cereals • Refining of maize and rice reduces micronutrients and phytochemicals levels
• If maize or rice is grown in poor soils, it means less nutrients in the final product after processing
Drying: Removal of water from foods reduces the amount of water soluble vitamins. The
extent of loss depends on the amount originally present in the food item.
How often do food industries analyse the nutrient content of foods before processing?!!!!
Does food processing really add value or reduce value??!!!
CONCLUSION
If the soil has adequate amounts of elements, and good agricultural practices are followed then there will be no need of fortification or supplementation. Plants are the best manufacturers of nutrients
However, it is important that food processing is done in such a way to protect the nutrients and not to remove them, not after the plants have laboured so much to put them in foods in the first place.
There is a need to reconceptualise food
processing so as to ensure that nutrients
originally present in foods are not removed but
conserved.
Agriculturalists, food scientists and nutritionists
should work together to ensure
wholesomeness of foods we consume.
CONCLUSION.....
WORK IN PROGRESS
From Soil Elements to Food Nutrients: Improving The Nutrient Content of Foods for Human Consumption Through Agriculture
link between soil elements, agriculture practices, nutrient content and nutrition
Maize
Rice
Round potato
Common beans
Amaranth
Sweet potatoes leaves
Package of recommendations for optimal soil elements uptake by crops and improved yield;
Data base of soil elements and nutrient composition of foods;
Information package of soil suitability for high nutrient crop production;
Package of information on conditions and practices for optimal soil elements uptake by plants;
Best practices of agricultural crop production for optimal nutrient content
WORK IN PROGRESS
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