Midterm 1.6 Food Processing Flashcards
What is food spoilage vs food contamination
food spoilage percentages
Food spoilage: Biological, chemical and physical changes in appearance, texture, taste and odor
Food contamination: undetectable
20% of all food is lost to spoilage
1/4 of American food purchased is discarded
Foods most susceptible to spoilage
Foods high in water (above .6 Aw) and protein content (meat, poultry, fish, dairy, eggs)
Categories of food spoilage
Biological - bacteria (food borne illness), yeast (fermentation) and molds (toxins)
- prevent contact with microbiological organisms or deprive them
Chemical - proteolytic enzymes, lipases and carbohydrases - results in new compounds
- stop enzymatic action or slow it down
Physical - evaporation, drip loss, separation
- protect from physical damage
How have wars contributed to advances in food preservation?
1700’s Napoleonic wars led to discovery of canning
WWII led to discovery of dehydrating foods
Vietnam war led to discovery of freeze-drying foods
Types of drying methods (8)
Sun drying - oldest
Conventional drying - heat used to evaporate water out
Spray drying - fine spray of liquid dried quickly in midair
Drum drying - liquid poured over inside surface of hot barrel and then peeled off and broken into flakes
Vacuum drying - chamber pressure reduced and is moisture boiled off
Osmotic drying - strong syrup used to draw water out of object being dried (cranberries)
Freeze-drying - freeze and then place in vacuum for ice to sublimate, MOST effective because no high heat
Microwave drying - rapid microwave drying
Pre-treatments for drying (3)
Fruits have skins “checked” or dipped in hot water or lye to break skin and facilitate drying
Blanching to arrest enzymes that cause browning
Sulfite solutions or Sulfur dioxide gas - stops browning and loss of vitamin A and C
Pickling
Preserves by acidification (citric or acetic) and/or fermentation (lactic acid)
Salt is added to draw moisture out and inhibit microbes
Clostridium botulinum cannot grow below
4.6 pH
Benefits of edible coatings
Types
1) increases shelf life
2) Improves food handling
3) Improves appearance
Lipid - waxes, oils and petroleum based
Protein - gelatin, collagen, whey, corn zein, soy, and wheat gluten
Carbohydrate - starches, cellulose, seaweed extracts, pectinates and chitosan
Canning process
Food is packed into containers, boiled, sealed and then boiled again to create seal
Without oxygen microorganisms cannot thrive (unless in spore form and above pH 4.6)
Heat kills microorganisms and destroys enzymes responsible for spoilage
Hot pack vs cold pack canning
Hot: Foods heated to 170°F/77°C in syrup, juice or water and added to sterilized jars
Cold: Foods put in sterilized jars and boiling liquid is added
Low acid foods must be boiled 10 minutes to destroy chance of C. botulinum
Both are vacuumed sealed
Benefits of crisper drawer and spoilage of veggies
Limits amount of oxygen available to foods which slows metabolism
Spoilage occurs when nutrient supply runs out and cells start to die
Fridge and freezer temps
Fridge between 0°C (32°F) and 4°C (40°F)
Freezer -18°C (0°F) and below
Why is freezing foods best?
- Freezing water makes it unavailable to microorganisms
- Least damaging to food and preserves flavor, nutrient content, and texture (faster freeze, better preserved)
- Oxygen is still available so degradation still occurs (less time than canned goods, 2-12 months)
Higher fat foods, sensitive veg and fruits not great for freezing
4 Problems with frozen foods
Freezer burn - improper packaging and too long freeze
Cell rupturing - water expands and ice crystals pierce cell walls
Fluid loss - drip from thawing meats
Recrystallization - temp fluctuations cause melting and refreezing
