Lecture 9 : MAP Flashcards
What is MAP?
modified atmosphere packaging
- food preservation technique
- comp of the atmosphere around the food is diff than comp of the air
how is MAP different than controlled atmosphere?
in map, there is no way of controlling the atmosphere components at specific concentrations once the package has been hermetically sealed
what are market demands for MAP?
- natural
- good quality
- longer shelf life
- convenience
- good protection from environment
what are effects of O2 on food?
what do all of these result in the loss of?
- deterioration from oxidation
- discoloration
- decomposition (Microorganisms
- damage due to insects
loss of
- freshness
- quality
- taste and flavour
- nutrients
what are advantages of MAP?
- extended shelf life and increased market areas
- better use of labour and equipment
- better economies of scale (by purchasing larger quantities of raw materials)
- reduces transportation costs
- less frequent loading of display shelves and checking “sell by” dates
- enhancement of sales
- reduction of costs associated w/ freezing
what are disadvantages of MAP?
- cost of packaging, equipment, films, etc…
- slower throughput of packages
- leakage
- secondary spoilage problems
- potential growth of organisms of public health concerns
what are methods of atmosphere modification?
- vacuum packaging
- gas packaging
- gas absorbents
- gas generators
describe vacuum packaging
removal of all or most of the air within a package without deliberate replacement with another gas mixture
what are properties of vacuum packaging?
- 5 times longer storage as refrigerated food
- no more freezer burn
- uses laminated films for strength and barrier properties
what are 3 types of vacuum packaging?
chamber vacuum packaging machine
belt vacuum chamber machine
thermoform fill seal machine
which molecule forms bright red?
a) oxymyoglobin
b) myoglobin
c) metmyoglobin
oxymyoglobin
which molecule forms dark red?
a) oxymyoglobin
b) myoglobin
3) metmyoglobin
myoglobin
which forms brown?
a) oxymyoglobin
b) myoglobin
3) metmyoglobin
metmyoglobin
what are factors influencing shelf life of VP pdts?
- raw material quality (affects microbial quality and pH)
- temp control
- hygiene control
- time before packaging
- film permeability
what is the spoilage defect of beef?
acidifying
greening
what is the spoilage defect of pork?
flavor (rancidity)
greening)
what is the spoilage defect of lamb?
color and fat appearance
describe gas packaging
the physical displacement of air by a new gaseous composition
what are 3 techniques used to replace air in gas packaging?
what equipment do each of them use?
- gas flushing: horizontal/vertical form fill seal (H/VFFS)
- compensated vacuum: thermoform-fill seal (TFFS)
- passive modification: no equipment needed. Takes place within sealed package
compare gas flushing to compensated vacuum
gas flushing
- uses the form-fill-seal machine
- continuous flushing
- fast
- residual O2
compensated vacuum
- thermoform-fill-seal machine
- slower
- less residual O2
- used for O2 sensitive pdts
what are characteristics of GP films?
- resistant to puncture
- sealing reliability
- anti-fog
- CO2 permeability
- O2 transmission rate (OTR)
- water vapour transmission rate (WVTR)
what are major gases used in MAP?
other gases?
major gases
N2
CO2
O2
other SO2 CO N2O Ar
why is CO2 a major gas in MAP?
- not inert
- bacteriostatic
- fungistatic
- prevents insect attack
- fat and water soluble
describe the antimicrobial action of CO2
- displacement of O2
- extracellular pH reduction
- intracellular pH reduction
- disruption of cell membrane and enzymes associated w/ metabolism
- increase lag phase = extend shelf life
the result of microbial growth depends on what?
- storage temp
- Aw
- gas conc
- type of MOs
- initial microbial load
- film permeability
in GP, describe use of O2
usually avoided
except for
- color of fresh meat
- respiration in fruits and veg
- anaerobes
describe use of N2 in GP
- inter
- no antimicrobial properties
- filler gas
what is the radio of gases in GP of fresh meat?
20% CO2 (for prevention of bacterial spoilage)
80% O2 (bloom)
in the GP of bakery products, what gas is the highest?
CO2 (50-100%)
rest is N2 (up to 50%)
no O2
what are O2 absorbents?
chemical compounds in the MA package to alter the atmosphere within the package
what are types of O2 absorbents? (according to material)
- inorganic: Fe powder; Na2S2O4
- organic: ascorbic acid; catechol
- enzyme: glucose oxidase (glucose –> gluconic acid + H2O2)
what are types of O2 absorbents? (according to rxn style)
- self-reactive type
2. moisture dependent type
what are types of O2 absorbents? (according to rxn speed)
- immediate effect type
- general type
- slow effect type
what are forms of O2 absorbents?
- sachets
- labels
- cards
- scavenging films
- crowns and closures
what are factors influencing type and size of sachets?
- nature of food (size, shape, wt)
- Aw of food
- amount of dissolved O2 in food
- initial level of O2 in package headspace
- desired shelf life
- O2 permeability of packaging material
what are advantages of O2 absorbents?
- non-toxic and safe
- extends microbiological and chemical shelf life
- replaces additives and preservatives in pdts
- reduces distribution losses
- replaces chemical pesticides to prevent insect damage of foods
what are disadvantages of O2 absorbents?
- need free flow of air to scavenge O2
- may cause package collapse (use O2 absorbent or CO2 generator)
- o2 absorbents/CO2 generators may cause flavour changes in high moisture foods
- expensive
- consumer resistance to sachets
describe ethylene scavengers
reduces ethylene to extend shelf life of fresh produce
ethylene scavengers can be
- scachets based on KMnO4 or activated charcoal w/ palladium catalyst
- PE films containing activated clay (clay absorbs ethylene and modifies gas barrier properties)
what are chemicals used in CO2 absorbents?
CaO
Ca(OH)2
NaOH
what are two types of ethanol vapour generators?
- ethicap:
- increases ethanol - negamold
- increases ethanol
- decreases O2
what are ethanol vapour generators used in?
moisture dependent cakes/bread
when Aw > 0.85
what layer is on the outside and inside of the anti-microbial SO2 generation system?
outside: calcium sulfite layer
inside: organic acid layer
what are halogen gases for ethylene removal in gas generators?
KI
NaClO2
what gases are produced by gas generators?
- halogen gas
- ethylene
- CO2
