Most pathogens cant grow psychrotrophs can though

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, most pathogens cant grow, psychrotrophs can though; Factors affecting quality: controlled temp (avoid chill injury), humidity (prevent dehydration, but don't want too much moisture either), gas atmosphere comp; Modified atmosphere packaging (remove air… pasta, cured meats, cheese… still need to be refrigerated) Freezing: commercial freezing at -18C, home at -12 to -14C; MOs cant grow below -9.5C, but some can below 0C; ---corn = blanching 3 ½ mins at 85-88C; frozen at -20C; PP: low temp,low water activity to inhibit growth of MOs;MOs can survive and resume growth upon thawing; usually higher quality than thermal processed foods; Quality frozen food affected by: rate of freezing (faster is better, small ice crystals), final storage temp (usually around -18C), stability temp (fluctuations in temp= large crystals), rate of thawing (faster is better); Freezing methods: air freezing (still air freezersslow, air blast freezers-18 to -34C, cold air at high velocity, IQFindividually quick frozen), indirect contact freezing (plate freezers (ex: fish sticks)), scraped surface/slush freezers(ex: ice cream.. used for liquid products only), immersion (refrigerant fluid) & cryogenic (N2, liquid CO2)used for frozen turkeys, chickens, ice cream popsicles, TV dinners very rapid; Packaging: resistant to h20 vapour transfer, resist formation of pinholes, depending on food may posses barrier properties toward light and/or oxygen L8: Dehydration:heat/energy transferred to food to promote h20 removal from food imparts long storage life; concentration foods not fully shelf-stable; PP: microbial growth (need aw≥ 0.93); staphylococcus aureus (aw 0.85), mould (need aw ≥ 0.6), chemical rxns e.g. Maillardbrowning, aw > 0.3; DH foods aw 0.2-0.6, but MO not killed, resume growth rehydrate; Changes during DH: shrinkage (As water migrates to the surface of the food it carries with it the water soluble substances dissolved in it (ex. apple… when dried, surfacesugary), case hardening (sugar forms fairly impermeable case, common in high sugar products), chemical changes (browning, denaturation proteins, loss water binding capacity); Factors affecting dehydration: surface area, temp of drying air, air velocity, humidity drying air, atmospheric pressure & vacuum; Drying methods: Sun drying (fruits, veg, fish, inexpensive), spray drying (powder milk, instant coffee, eggs), tray/tunnel air drying (poor rehydration properties, food shrinkage; pasta, fruit, spices), drum drying (fairly good rehydration; mashed potatoes, baby cereal), freeze drying/lypolyzation (food must be in frozen state, water will sublime (solid to vapour, skip liquid); excellent rehydration, no shrinkage, very expensiveinstant soup, space food), vacuum microwave drying (complete rehydr), deep fat drying (hot oil causes h20 to evaporate rapidly; instant noodles), vacuum extrusion drying (food puffs, moist heat causes starch gelatinization and cooking of productbreakfast cereals, snack foods); Packaging requirements: protect against moisture absorption; DH foods are hygroscopic L9: Food preservation w/ biotechnology:

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