Shared Flashcard Set

Details

Food Science 301
Removal of Thermal Energy (lecture 5)
14
Science
Undergraduate 2
05/10/2010

Additional Science Flashcards

 


 

Cards

Term

 

Purposes of Cooling

 

Definition

 

 

  • To Prolong Product Quality
  • To Increase Shelf-Life
  • To Slow post-harvest or post-slaughter physiological changes
  • To slow microbial growth
  • To slow enzyme activity
  • To make some foods possible

 

 

Term
Methods of Cooling
Definition

 

  • Chilling in Air
  • Indirect Contact Chilling
  • Direct Contact/Immersion Chilling

 

Term

Chilling in Air

Definition

 

  • Still Air
  • High-velocity Air
  • Fluidized Bed

 

Term
Indirect Contact Chilling
Definition

The food or package is in contact with a surface that is cooled by a refrigerant, but the food or package does not contact he refrigerant directly

  • plate heat exchanger
  • tubular heat exchanger

 

Term
Direct Contact Chilling
Definition

 

  • Direct contact of the food and refrigerant
    • Cold water spray
  • Submerging a food or spraying cold liquid onto the food or package
    • Submerging food in ice water or cryogenic fluids
  • Allows for intimate contact with the refrigerants
    • Storing on Ice

 

Term
Deterioration of Food During Refrigerated Storage
Definition

 

  • Chill Injury of Fresh Produce
  • Flavor Migration between foods
  • nutrient loss
  • retrogradation of starch
  • Oxidative rancidity of lipids
  • Enzymatic Reactions
  • Water Migration
  • Growth of Spoilage Organisms

 

Term
Microbiology and Low temperatures
Definition

 

  • Most microorganisms and pathogens don't grow at refrigeration temperatures
  • Pseudomonas does
    • counts can increase by a factor of 10 in 24 hrs at 70
    • produces heat stable proteases and lipases that are a concern in food

 

 

Term
Physical and chemical effects of freezing on food
Definition

 

  • proteins can denature
  • carbohydrates can come out of solution
  • acid concentration increases
  • gas pressure increase

 

Term
Heat Shock Damage
Definition

Intermittent thawing and freezing of a product, as often occurs during temperature cycling

  • does not require total change of ice to liquid

 

Term

Rate of Freezing

(results in, and is essential for)

Definition

 

  • Results in more, homogeneously dispersed ice nuclei
  • essential to preserving food quality

 

Term
Microbiology of Freezing
Definition

 

  • Bursts their cells and dries them out
  • Can kill higher level pathogens

 

Term
High-velocity Air
Definition

  • Wind Speeds up to 30-40 mph
  • Disadvantages: larger temperature gradient, expensive, dries out product

Term
Fluidized Bed
Definition

  • Use of high velocity air to separate particles
  • Often done with "Individually Quick Frozen" foods 
  • Freezes so quickly that no case hardening occurs

Term
5 Steps of Freezing
Definition

  1. Cooling to "freezing point"
  2. supercooling until...
  3. NUCLEATION
  4. Heat is released and local temperature increases
  5. further cooling will cause more ice to grow on existing crystals

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