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Lecture 5: Food Storage and Food Packaging (Methods to prolonged storing…
Lecture 5: Food Storage and Food Packaging
Main purposes of storing food
Reducing kitchen waste
by preserving unused or uneaten food for later use.
Preserving
pantry food (spices) or dry ingredients (rice and flour) for eventual use in cooking.
Enabling a
better balanced diet
throughout the year.
Preparedness
for catastrophes, emergencies and periods of food scarcity or famine.
Storage
of harvested and processed plant and animal food products for
distribution to consumers
.
Protection
from animals or theft.
Conditions after harvesting
Growth of roots
- vegetables
Hardening
- green peas, corn; at
high temperature
Elongation
- asparagus, red carrot
Rotting and molding
Germination
- onion, garlic, potatoes
Main factors of food spoilage during storage
Weather
- rate of UV rays, oxygen, moisture, temperature difference
Contamination
- from microbe, insects, soil
Mechanical force
- shaking, compression, peeling, impact
Mishandling of food items by workers
Methods to prolonged storing duration
Using chemical actions.
Radiation.
Controlling the spread of disease.
Cooling.
Controlling the air or atmosphere.
Modern packaging.
Harvesting at the right time.
Factors influencing stores products
Temperature
low temperature - products become frozen and wounded due to coldness.
high temperature - spoilage occur and reduce the market duration.
Relative humidity
between 90-95%.
low humidity - product loses moisture, dry and wrinkle.
high humidity - encourage the growth of microbe.
Sunlight
food stuffs are kept in dark place or less light - to prevent photosynthesis from happening and alter the taste and smell of fruit.
some lipids are sensitive to light and may oxidize in the presence of UV.
Atmosphere content
modified atmosphere - to reduce the oxygen concentration and increase the carbon dioxide concentration
gas carbon dioxide are allowed to enter/exit the storage - for best result; to control total of respiration.
carbon dioxide - prevents insects, and depending on concentration, mold, and oxidation from damaging the grain.
Food Packaging
Objectives
Information transmission
Technical information
weight
instruction
manufacturing/expiry dates
Nutritional information
content
calories
nutrition
serving size
General information
product name
manufacturer
place of manufacturing
Marketing
Packaging and labels - to encourage potential buyers to purchase the product
Marketing communications and graphic design - applied to the surface of the package and the point of sale display
Containment or agglomeration
Security
Engineered to help reduce the risks of package pilferage
May include
authentication seals
- to help indicate that the package and contents are not counterfeit
Made with:
improved
tamper resistance
- to deter tampering
tamper-evident features
- to help indicate tampering
Barrier and physical protection
- to control the amount of light, heat, moisture and gas, and presence of microbe
Heat
depend on the
ability to transfer heat
or possess specific
thermal conductivity
characteristic
low thermal conductivity
- paper box, polysterene and polyurethane
glittering material
(aluminium foil) - could reverse radiation heat
Moisture and gas
for dry food and food sensitive to gas (oxygen, ethylene)
for frozen and modified atmosphere food, duration in market depend on the rate of heat, carbon dioxide and oxygen transfer through package material
Light
transparent
container
polyethylene
- could be penetrated by UV rays and visible light
poly-vinylidine
- could not be penetrated by UV light
Presence of microbes
good package material - prevent the entrance of microbe
main source of microbe contamination -
packaging without sterilization
other sources - entrance of
contaminated air or water
through small pores on surface of food; not suitable
covering/sticky
;
damaged
on packaging - tear, broken;
unhygienic packaging environment
Presence of desiccants/oxygen absorbers
- help extend shelf life; keep the contents fresh and safe for the intended shelf life
Convenience
Characteristics of materials used for food packaging
No side-effect
produced when in-contact with product.
Not toxic
or a
source of contaminant
to product.
Safe
to the product.
Durable, not easily tear, not fragile or dented
Labeling - properly and clearly
Types of Food Packaging
Shipping containers
protect the product during delivery and distribution
built from wood, steel, tank etc
Retail containers
protect and display of product for sale
products are kept in volume/bulk for consumers
made from tin, bottle, tubes, paper boxes etc
c)
Glass
Advantages:
does not penetrated by humidity, gas, smell and microbe
does not react with food
filling rate is as rapid as filling the cans
suitable for heat processing
penetrated by micro waves and light to display its content
hard, can be arranged by stacking
reusable
Disadvantages:
heavy - increase output cost
easily broken/fragile, crack - risky to consumer
Made by heating mixture of
sand (73%), NaOH (13%) and CaO (12%)
e)
Paper and boxes
paper to make boxes - made from wood which is hydrolyzed with acid (sulphate pulp) or alkaline
sulphite pulp - lighter and softer, useful for food and sweets packaging for retail shops
can also be constructed heavy and hard
important to make strong paper
specialized paper packaging - grease proof paper to pack fish and meat
b)
Steel
Disadvantages
expensive and heavy
Types of steel packaging
2-piece cans
made with DWI (draw and wall iron) method or DRD (draw and redraw)
DWI - produce thin and soft cans; suitable for gaseous drink - gas pressure in the can helps to retain the shape
DRD cans - heavier and thicker; suitable for sterilized food
a layer of lacquer (
epoxy phenolic
) is applied - prevent interaction between food and tin
Aerosol can/spraying
similar to 3 or 2 layers; added with aerosol pump
propellant elements are mixed or separated using plastic bag
propellant allowed for food - nitrogen, carbon dioxide and Argon gas
3-piece cans
use to store pasteurized food, syrup, powder and non-heated cooking oil
electrolyte-covered pieces of steel on both sides by tin
new technology: tin is replaced with chromium dioxide and thin pieces of steel
Advantages:
provide full protection to food product
suitable to be stored at room temperature and exhibition
its content could not be disturbed
d)
Plastic bag or flexible film
cheap, light and prevent microbe entry
can be covered or sealed using heat
-strong and firm material, and can be printed
could be produced, used and stored
many types, with various thickness
able to follow shape of food, not wasting storing space
a)
Textile and wood
Textile
no protection from gas and humidity
not suitable for rapid filling and less attractive
limited to packaging for delivery purpose only
advantages:
cheap, durable and reusable
Wood
commonly used for fruits, vegetables, leaves etc
provide stronger protection, boxes can be overlapping
disadvantages:
easily rotten, not reusable and less attractive