food preservation
DESCRIPTION
Food preservationTRANSCRIPT
FOOD PRESERVATION
Food Preservation Methods Inhibition Inactivation Avoid contamination
Inhibition low T storage reduction of aw decrease O2, increase CO2, vacuum acidification fermentation freezing surface coating structural modification
Inactivation sterilization pasteurization radiation electrifying high pressure blanching cooking frying
Avoid recontamination packaging hygienic processing hygienic storage aseptic processing
Thermal processing pasteurization
inactivation of vegetative cells and/or enzymes sterilization
inactivation of spores blanching
inactivate enzymes fruits and vegetables ohmic heating
electrical conductivity for foods with 30-40% water dissolved ionic components uniform heating short processing time
Cold storage Chilling
slowing microbical growth reduce enzymatic and chemical reactions slow postharvest metabolism reduce moisture loss
Freezing slowing microbial and chemical reactions water immobilization reducing molecular mobility some microbial destruction
Reducing aw drying freeze-drying humectants freezing
slowing microbial and chemical reactions
water immobilization reducing molecular mobility
Fermentation inhibition of spoilage/pathogenic
flora by beneficial microbial flora consumption of substrate for
biochemical/chemical reactions production of antimicrobials acidification
Preservatives acidification
pH change antimicrobial property
other preservatives antimicrobial antioxidant enzyme inhibitor control redox potential
Control of redox potential CA/MAP
prevent postharvest ripening reduce microbial activity
Nonthermal processing Irradiation
free radical species hydrogen, H2O2, OOH
High pressure 3500-10000 atm protein damage
Pulsed electric field dielectric cell membrane destruction
Oscillating magnetic fields Microwave
thermal effect (?)
Irradiation- nonthermal - process in package, minimize contamination- form of food is not a factor- can replace preservatives, insecticides- can be used in fresh foods
Canada1960 – sprout control in potatoes and onions1961 – insect control in wheat1983 - spices
Irradiation
Doses of irradiationsprout inhibition: 0.15-0.2 kGyflour disinfestations: <= 1kGyspice cleaning: 5 kGyparasite elimination: <=6 kGypathogen destruction: <=10 kGybacterial destruction: <=5 kGy
Irradiation <= 10 kGy harmless to human health
(UN) pasteurization effect need to be used in combination with
refrigeration and CA/MAP
currently used forspices, disinfestations of cereal grains, pathogen control in poultry, trichinosis control in fresh pork, tropical fruits
Chilling
storage at T > Tfp (-1) - (+10 C)
chilling injury near Tfp
texture degradation in vegetables cold shortening of muscle foods,
staling of bread
Freezing
small many crystals desired, fast freezing entrapment of solutes, less than max concentration in the unfrozen phase
large crystals, slow freezing max concentration of solutes, tissue damage, partial dehydration,
local freeze concentration freezer burn, sublimation of ice, dry brown spots
on poultry, beef antimicrobial effect due to concentration,
intracellular freezing destabilization of proteins, vitamin and pigment
degradation, oxidation of lipids
Concentration and dehydration
concentration > 20% moisturedehydration < 20% moistureevaporation, crystallization,
sublimation, membrane separations
microorganisms survive, can recover, grow depending on aw
Controlled atmosphere
control of atmosphere composition during storage
in packaging, gas impermeable films with absorbers
Modified atmosphere closed storage rooms, allow
respiratory activity in packaging, remove air, replace
with other gases, N2, CO2
vacuum packaging vacuum, nitrogen: cheese, meat CO2 : fruits and vegetables, meat
Ohmic heating short processing times < 90 s, then
transfer into holding tube, aseptic packaging, commercial sterilization
no heat transfer surfaces, food heats inside, more efficient and uniform heating, reduces thermal quality defects
suitable for solid pieces containing liquid foods, like stews
Microwave heating
rapidcan be used in sterilizationapplicable to packaged productsprevent contaminationthermal inactivation
High pressure processing
better quality foodsready-to-serve foods, vegetablesjams, preserves, meat, seafoodpulsed high pressure applicationpressure environment, glycerol, edible
oils, water/edible oil emulsions700-900 MPa
Preservatives Legally allowed1. toxicity 2. soluble in food 3. food pH
- inhibition of chemical/biochemical reactions
- antimicrobial effect
Organic acids acidity, antimicrobial effect benzoic acid, Na- or Ca-benzoateparabens (p-OH-methyl or propylbenzoate)mold and yeast inhibitorat low pH antibacterial, 0.1%
jams, preserves, bakery products, salad dressingfruit juices
Organic acidssorbate (2,4-hexadienoic acid), K/Ca/Na
saltsmold and yeast inhibitorcheese, fruit juices, salads, bakery products
propionic acid, Ca/Na saltsrope inhibitors in bread, cheese, spreadsmold inhibitor at high pH
Organic acidsacetic acidrope inhibitor, mold inhibitorbakery products
lactic acid antimicrobial
citric acid acidulantion chelatorreduce oxidation
Nitrites and nitrates (NO2/NO3)
color stabilization C. botulinum inhibitor
Sulfur compounds (SO2, HSO3
-, SO32-, S2O5
2-)
antioxidant browning inhibitorantibacterial limited use due to allergic
reactions in some people wines, dried fruits, vegetables
Salt (NaCl) control of water antimicrobial
Antioxidants
rancidity inhibitorsBHA, BHT, tocopherolsascorbic acidEDTA (ion chelator)
Smoke (phenols, formaldehyde, ketones, alcohols, acids)
antioxidantantibacterial, C. botulinum
Carbon dioxide
antimicrobialcarbonated beverages
Antibiotics
nisin antibotulinal, antibacterialprocessed cheese
natamycinmold inhibitorsalami, cured cheese
Ethylene oxide
antimicrobialspices, nuts aseptic packaging
Other antimicrobials
chlorine (Na, Ca hypochlorite)ozonehydrogen peroxide
fresh fruits, vegetables
Packaging glass, metal, plastics, paper transport of gases, water vapor, low
MW components resistance (mechanical, heat,
chemical) oxygen, carbon dioxide, moisture
permeability light transmission inertness
Active packaging
interact with food or package environment responding to changesincorporation of different materials into the film or package
headspace to improve package performance- antimicrobial films
sulfur dioxide releaserethanol releaser
- oxygen scavengersiron scavengerphotosensitive dye scavengersenzyme scavengers
- moisture absorbersdessicant packages, clay, minerals, silica
- ethylene absorbers
KMnO4
Smart packaging
interact with food or package environment and give signals
indicate time/T historyindicate spoilage, remaining shelf
life, end of shelf life
Aseptic packaging
1. product sterilization2. package sterilization3. Aseptic filling and sealingLonger shelf life, better quality (?)
Hurdle technology
developed for limiting the growth of microorganisms in nonsterile foods (Leistner, 1978)
combined effects of preservation methods > sum of effects individually or large amounts of a single factor
Hurdle technology
has been used unintentionally
pickles pH + preservative (acid) + salt
sausage
aw + smoke + salt + spices + preservativesIMF (dried fruit, soft cookies)
aw + heating + preservatives pastırma
salt + spices + aw
Hurdle technology
HurdlesTpHsaltredox potentialmodified atmospherepackaginghigh pressureradiation, other physical processescompetitive flora (lactic acid bacteria)preservatives
all hurdles at the same intensity
all hurdles at different intensity
low initial microbial loadgood hygienic practice
high initial microbial load
low initial microbial loadmore nutrients
substerilizing treatmentdamaged cells
t : chillingF : heatingRVP : relative vapor pressure, awpH Eh : redox potentialpres : chemical preservativeN : nutrients