storage is the process in which both cooked and raw materials are stored in appropriate conditions for future use without any entry or multiplication of microorganisms

1. Effect of Storage on The
Nutrients of Processed Foods
Submitted by
Towkir Ahmed Ove
M.Sc. In Food Science & Nutrition

2. Food Storage
Food storage is the process in which both cooked and raw materials are
stored in appropriate conditions for future use without any entry or
multiplication of microorganisms.
Types of Storage
1. Dry storage
Dry storage is meant for longer holding of non- and semi-perishable
foods, the latter being stored for a shorter time. It is the space designed
for the storage of foods usually at room temperatures ranging 20-25°C
with the relative humidity maintained at 60-65%.
2. Low temperature storage
Low temperature storage is further divided into three types based on
temperature requirement.

3. • Refrigerated storage is a storage space maintained at temperature between 3 to
10°C. It is used to store perishable foods for short term say 3-5 days. Beyond this
period, certain changes in foods take place due to enzymatic or microbial activity.
Milk and eggs are generally stored under refrigerated storage.
• Cold storage is one in which temperature is maintained between 0 and 3°C. Such
storage spaces are also called as chill rooms. These can hold perishables over a
week and in the case of fruits and vegetables, even up to a month depending
upon variety and stage of maturity. Fruits and vegetables are usually stored in this
type of storage.
• Freezer storage is apt for long term storage of perishable foods and the
temperature ranges from -20°C to 0°C. Pretreatments like blanching, quick cooling
to freezing temperature and packing in air tight containers are necessary for
successful freezing. Generally, frozen foods are kept under this type of storage.

4. Essential features of food Storage Areas
• It should be fit for purpose (dry store, chill, frozen etc.) i.e. it must provide proper
temperatures and humidity for prolonging shelf life of foods
• The separate area could be designated for different types of food. For example
raw and cooked should be stored separately.
• It should be able to provide protection from contamination/ infestation.
• It should be weatherproof.
• It should be able to keep out direct sunlight/ heat
• It should have suitable space and structural arrangement for providing sufficient
light and ventilation.
• It should be easily cleanable.
• It should provide easy access to materials.
• It should be accessible for transport of food.

5. Factors that affect food storage
 Temperature:
The temperature at which food is stored is very critical to shelf life. United States
Department of Agriculture, USDA, states that for every 10.8 degrees in temperature
rise you decrease the shelf life of stored food by half. The best range for food storage
is a constant temperature between 40-60 degrees. Avoid freezing temperatures.
 Moisture:
It is recommended to remove moisture when storing foods. For long term storage
foods should have a 10% or less moisture content.

6. • Atmosphere the product is stored in:
Foods packed in air don't store as well as in oxygen free gasses. This is because air
contains oxygen which oxidizes many of the compounds in food. A high oxygen
environment causes oxidation, which leads to discoloration, flavor loss, odors,
rancidity and the breakdown of nutritional value in foods.
• Container:
Store foods in food grade plastic, metal or glass containers indicating that the
container does not contain chemicals that could be transferred to food and harmful
to your health. For best storage life, use containers with a hermetic (air tight) seal.

7. Changes during storage
• Meat and meat products
Meat is a highly perishable product and must be stored under refrigerated conditions to
control microbiological growth and other deteriorative changes.
I. Chilled Storage
High pH (6.0 or higher) meat will spoil quicker than meat with a pH of 5.3 to 5.7. Also,
high initial levels of bacterial contamination on the surface of the meat will reduce the
storage life because spoilage numbers of bacteria are reached sooner.
Microbiological spoilage is characterized by off-odors, slime formation and
discoloration, and generally, spoilage occurs when the microbial population reaches
around 100 million per cm₂.
For these two reasons, beef will keep longer than lamb, because lamb has a higher pH
and because of differences in the slaughter and dressing process, lamb carcasses tend
to have higher numbers of initial bacteria.

8. II. Frozen Storage
During frozen storage microbiological growth is arrested, but meat will slowly
deteriorate due to oxidative and other changes.
It has been reported that freezing brings about a definite increase in the pH of the
meat which has been attributed to the suppression of acidic groups through
molecular changes in the proteins.

9. • Milk and milk products
Milk and milk products should be stored in a refrigerator to slow down the growth of
micro-organisms, such as mold on cheese.
UHT milk is packed into sterilized containers and is shelf-stable for six months. After six
months, the flavor and color begin to change and the product thickens.
Butter can be stored for up to two weeks at refrigerator temperatures (below 40 °F).
Higher temperatures cause off-flavors and unpleasant odors to develop.
Yogurt may be kept well covered in the refrigerator for seven to 10 days past the "sell-
by" date. If it is kept longer, it will develop a stronger taste.
Freezing yogurt is not recommended because of the variable results in texture.
Freezing affects texture of cheese (makes it crumbly).

11. • Fish and fish products
However, psychotropic bacteria will still thrive at 00Cand can cause spoilage relatively
fast also under chilled conditions.
In fish and seafood, deep chilling has been applied successfully and shown to retard
microbial growth and extend shelf life of, e.g., prawn, squid, salmon and cod.
Freezing can also negatively influence structural and chemical properties of muscle,
e.g., increase content of free fatty acids (FFA) and lipid oxidation products.
Freezing minimizes microbial and enzymatic activity and hence preserves the flavor and
the nutritional properties better than chilled storage.
However, the formation of ice crystals during freezing is a critical point and the larger
the ice crystals are formed, the higher is the risk of texture damage and membrane
disruption resulting in increased oxidation.

12. • Cereal products
Nutritional changes in cereal grains occurred, to various extents, during storage
at different temperatures.
 A decrease in pH and an increase in titratable acidity started appearing after
three months of storage at 25°C.
The increase in the acidity of the stored grains could be attributed to the
increasing concentration of the free fatty acid and phosphate, which resulted
from increased grain deterioration.
Total soluble sugars in rice, maize and wheat decreased by 36.4%, 44.4% and
37.2% at 45°C during six months of storage.

13. Decrease in total available lysine at 25°C and 45°C was significant while it was found
to be non-significant at 10°C during six months of storage.
Nutritional quality of cereal gains was adversely affected as a result of storage at
elevated temperatures.
Significant losses of lysine and thiamine occurred on storage of cereal grains at 25
and 45°C.

14. • Fruit and vegetable products
Total phenolics, antioxidant activity, anthocyanins and pH of orange fruits and fruit
jams during 5 months of storage showed that total phenolics decreased.
Antioxidant activity did not change in strawberry jam; on the other hand,
anthocyanins and pH were reduced in apricot and fig jams during 5 months of
storage.
The ascorbic acid progressively decreases during storage, the rate of destruction
being more rapid at higher storage temperatures.
Blasco et al., (2004) had also reported two different degradation pathways of
vitamin C during storage. Aerobic degradation was observed in the beginning due
to presence of oxygen in the bottle but after prolonged heating the bottle
becomes saturated with vapor and becomes oxygen deficient which induced
anaerobic degradation.

15. Browning of fruit juice during storage is result of a non-enzymatic chemical
reaction between amino acids and reducing sugars called as Maillard
reaction.
Ahmed et al.,(2008) reported that a significant increase in reducing sugar
during storage of citrus juice which may be due to acid hydrolysis of sucrose
(non-reducing sugar) to glucose and fructose.
Hashmi et al., (2007) reported that the mango pulp stored at ambient
temperature (30°C -36°C) with 0.2% KMS showed negligible microbial growth.
Chauhan et al., (2002) reported that microbiological population (total plate
counts, and yeast and mold counts) increased during storage of sugarcane juice at
room temperature in comparison to storage at refrigeration temperature.

16. Thank you