Introduction to Foods Gelatins

1
Introduction to FoodsGelatins 
2
Define Gel

•    fluid trapped in rigid structure   work
  together (fluid in gel, gel in fluid)  
  polymers (chains) linked together

3
Types of polymers

• 1.        starch2.        egg
  protein3.        gelatin4.        pectin

4
 

•    gelatin made from collagen   connective
  tissue   nutritional value is low   bacteria
  growth concerns made in three forms1.
  granular2. pulverized3. sheets
•    when using, ratio of 1-3 parts gelatin to
  97-99 parts water

5
Hydration

•    swelling due to absorption of water
  (diffusion)    dependent upon1.size of
  gelatin particles2.percentage of
  water3.presence of salts accelerates
  process4.presence of sugar inhibits process

6
Dispersion

•    when the mixture reaches a temperature of 35
  C or 95 F   separation of molecules that form
  structure   therefore, add hot water to aid in
  separation

7
Gelation

•    reversal of dispersion process  
  temperature plays important role   normally
  requires a long time to set properly   rapid
  cooling affects strength (melts easier due to
  lack of strength)

8
Concentration of gelatin

•    increase the concentration of gelatin   
  increases firmness   decrease time of setting

9
Gel Foam 

•    air bubbles increase the volume (2-3
  times)   dispersion of the gel network
  structure   decreases the firmness of the
  network (possible weeping)

10
Acidity

•    high concentrations of acid inhibits gel
  formation and strength    salts increase
  strength   sugars weaken gel due to water
  absorption

11
Enzymes 

•    hydrolyze protein (breakdown)   weaken
  structure

12
Emulsions 

• Definition   one liquid dispersed in another
  liquid which is immiscble   can not mix or
  blend the liquids together

13
 Three Types

• 1) Temporary Emulsion
• do not hold together for long periods
• example oil and vinegar dressings that need to
  be shaken before service
• 2) Semi permanent Emulsion
• stabilizer added to decrease the tendency to
  separate
• example French salad dressing
• 3) Permanent Emulsion
• use of stabilizer / emulsifier to produce a
  product that will not separate
• example mayonnaise

14
Oil in Water Emulsion

• Oil droplets suspended in water
• Most emulsions of this type
• Examples milk, cream, egg yolks, puddings

15
Water in Oil Emulsion

• Water droplets suspended in oilExamples
  butter, margarine
• Both types of emulsions use an Amphiphilic
  molecule
• Polar in nature with two sides to each
• hydrophilic or water liking
• lipophilic or oil liking

16
Reasons for Breakdown of Emulsions

• 1. Oil particles coalesce (join together)2.
  Liquid added too fast3. Saturated solution4.
  Temperature

17
Mayonnaise

•    oil in water emulsion   65 edible oil by
  weight emulsified in vinegar or lemon juice  
  egg lecithin acts as emulsifying agent

18
 Factors affecting Mayo 

•    Temperature   harder to start with cold oil
  or eggs but end product is thicker  
  Ingredients    Salt aids in stabilization
  (crystalline structure)

19
Fats and Oils

• Difference between a fat and oilFat comes from
  animals, oils from plants
• Triglycerides   One glycerol molecule plus 3
  fatty acids

20
Saturated Fatty acid 

•    Full hydrogen capacity   Body produces
  low-density-lipoproteins to move cholesterol
  around body (promotes plaque in arteries)

21
Unsaturated fatty acid

•    Has one or more bonds not with hydrogen  
  Mono-unsaturated has 2 less hydrogen
  molecules   Poly-unsaturated has room for four
  or more hydrogen atoms

22
Melting Point

• based on three points
• 1) Number of saturated fatty acids (increase
  melting point)
• 2) Number of triglycerides (increase the number
  of carbon atoms)
• 3) Crystalline structure shape
• More unsaturated a fat, the more liquid it
  remains at room temperature
• More saturated a fat, the firmer its consistency
  at room temperature
• Remember that the product will melt over a range
  of temperatures due to mixture of triglycerides
  (quality of refining)

23
Plasticity

• ability to mold or shape (spread ability)
• liquid held in network of crystals
• increases melting point
• the more unsaturated a fat is, the more plastic
  it tends to be

24
Hydrogenation

•    Addition of hydrogen molecule to chain  
  increases plasticity and melting point  
  reduces oxidation and spoilage

25
Winterization

•    cloudy in fridge   crystallization of
  molecules due to melting points (triglycerides)

26
Five Types of Oils

• Butter
• two and a half quarts of milk to make ¼ lb of
  butter
• consists of 80 milk fat, no more than 16 water
  and 4 milk solids
• Margarine
• created in 1869
• consists of 80 fat and 4 milk solids
• lard or tallow
• hydrogenated shortening (Crisco)
• refined oils

27
Olive Oil

• three classifications based upon Italian law
• based upon the levels of acidity left in the oil
• the lower the level of acid, the higher the grade

28
Grades

• Extra Virgin
• approximately 1 acid
• the first cold press of the olives
• Virgin
• second cold press or mixture of two
• contains from 1 to 3.3 acid
• Refined
• heat extraction, third press or different blends

29
Rancidity

• Chemical deterioration of fat
• Molecules break off of the triglycerides and
  contribute to the off odors and tastes
• free acids and glycerol produced
• glycerol under high heat converts to acrolein and
  water (smoke and odor)

30
Rancidity

• Hydrolytic Rancidity
• Breaking of chemical bonds by the addition of
  water
• Oxidative Rancidity
• Breaking of chemical bonds by the addition of
  oxygen

31
Deep Frying

• Water on the surface instantly converts to steam
• Creates a barrier for oil penetrating into the
  food