FNH 200 u2013 FINAL CHEAT SHEET - Food deterioration MO...

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Food deterioration: MO, enz rxn, moisture gain/loss, infestation, inappro temps, phys stress, time, rxn w light/O 2 ; O +lip/hydr rancid •perishable: min/no process, <60days •semi-perish: some process, 2-6mo •shelf-stable: >6mo •date label: <90 days •MO classification: type (bacteria, mould, yeast, virus); func (good (probiotics, starter cultures), spoilage former, pathogens); temp (psychrophiles (0- 18), psychrotrophs (-5-35; major cause of spoilage of refrig foods) , mesophiles (10-45), thermophiles(50->100; most spoil)); O 2 (aerobic, anaerobic, facultative anaerobe) •bacteria: vegetative cells (active), spores (dormant), fast growth •yeast: slower growth, med tolerant (lower pH & aw) •mould: high tolerant, spores •virus: cause disease, not food spoilage, not used in fermented food •enzymatic browning: polyphenol+O2(polyphenol oxidase) brown pigments (enz soften fruit tissue) •preserv. goals: min. deterioration, eliminate MO harm, maintain quality & safety •methods: old change sens. props (dehyd, smoking, ferment, salting, sweeten); modern less changes (can, freeze, UHT, irradiation) •dehyd : principle: removal of free water to control chem, enz & microbial activity; complete (drying - shelf life); partial (conc. – not preserv technique alone); process: H removes water from food to environ. MO growth a w >0.93 (mould >0.6), chem rxn >0.3; DH foods 0.2-0.6; MO not killed resume when rehydrated •changes in dehyd (new methods change) : shrinkage: water moves to surface and carried away & brings water soluble substances dissolved; case hardening : rapid drying causes compounds (eg. Sugars) to form hard/imperm case around food, dehyd rate (esp sugar products); chem changes: browning (maillard bc as [solutes] + flav changes due to rxn, protein denature + polysac aggregation (loss of water binding capacity), loss of water-soluble component or conc. on surface, loss of volatiles (flav) •factors affecting dehyd: S:A to vol : SA fast mois loss; temp of drying air : temp DH; air velocity : max velocity DH; humidity of drying air : %RH of air determines final mois content of food (lower RH, more mois absorb); atmos pressure & vacuum: low pressure BP water decrease – imp for heat-sensitive products •sun: dry, warm climate; slow; fruits veggies fish; cheap; invasion by MOs/animals •spray: liquid/puree; droplets of food sprayed into stream of heated air; fast; powder skim milk, tea/coffee •tray/air: heated air at set velocity w/ low %RH (counter-current flow of air); poor/mod rehyd b/c case hardening; food shrinkage/dense; quick & cheap; pasta, veggie, fruits, spices •drum: semi-solid: paste/puree; rotated heated drum; rapid in thin layer; scrape product (flakes); good rehyd; mashed potatoes, cereal •freeze (lyophilization): must be in frozen state; vacuum chamber; radiants heaters E; water sublime: solid vapour; voids from crystals make channel; excellent rehyd; no movinf od water-soluble compounds to surface; shape of food retained, V expensive; slow; eg high-q coffee, military/space foods •vacuum microwave: vacuum (keep pressure low = low BP) & microwave (rapid E transfer): high quality

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