KBP Reactions

Reactions

ŸHydrolysis triglycerides --H2O---> diglycerides, monoglycerides,  glycerol + fatty acids  

–saponification (base catalyzed)

–enzymatic hydrolysis (lipase catalyzed)

–interesterification (randomization)

Hydrogenation unsaturated lipids  <-----H2-----> Saturated lipids trans isomers

Oxidation


Acid Hydrolysis

ŸAddition of water to cleave ester bon 

–also called lipolysis

 

•Catalyzed by strong acid 

•Produces free fatty acids

 Lipases

ŸCan also be catalyzed by  enzymes

–hydrolases or lipases

–found in plants and animals

–in vivo digestion

 

Hydrolysis:  Products

ŸSmall quantities of free fatty acids

–contribute flavors to cheese, milk  chocolate

–cause off-flavors in milk, fruits and  vegetables

–lead to foaming

Ÿremoved during commercial production of  food oils

 

Saponification

Interesterification

• ŸRearrange the fatty acids so they become distributed  randomly among triacylglycerol molecules of the fat
• ŸImproves consistency of fats
• ŸApplications:

–Manufacture of shortenings 
–Lard (want ~10% tri-saturated glycerides)

• ŸForms large and coarse crystals
• ŸShortenings posses grainy consistency and poor baking  performances
• ŸRandomization improves plastic range

–Production of high stability margarine blends and hard butters  with desirable melting qualities and crystallization behavior

                                                                                                          Free fatty acids 

 

Hydrogenation

ŸAddition of hydrogen across double bonds

Rate is determined by

–Nature of substrate

–Type and concentration of catalyst

–Pressure (concentration of H2)

–Temperature

–Agitation

Hydrogenation:  Products

Produces triglycerides with higher melting  points

liquid Þ semi-solid

Convert soft-fats into firmer fats

Useful in margarine, peanut butter, baked  goods

Improves oxidative stability 

Fat Replacers 

Olestra, Fat replacer

Olestra vs Triglycerides

Calories 75

Fat Calories 0  Total fat 0 g

Saturated fat 0 g

Ingredients: Potatoes,  Olestra, Salt, a-Tocopheryl  Acetate (Vit E), Vitamin A  Palmitate, Tocopherols (to  protect flavor), Vitamin K,  Vitamin D

Calories 160

Fat Calories 90  Total fat 10 g

Saturated fat 2.5 g

Ingredients: Potatoes, Corn  and/or Cottonseed Oil, Salt

Lipids and Health
Trans Fatty Acids 
ŸTrans fats refers to triglycerides containing unsaturated  fatty acids in the trans conformation

–Found in partially hydrogenated fats or oils

–Help to solidify food (melting point higher than cis)

ŸFDA adopted new food labeling

Ÿlabels give weight of trans fat

Ÿrestrict low fat definitions by trans fat content

–Some margarines are sold as ”trans free”

ŸNo hydrogenation

ŸMix sat’d and unsat’d fats

ŸTend to be soft spreads

Alternatives for trans-FA in Foods

Modification of the hydrogenation process

–Increase the degree of hydrogenation

Interesterification

–Expensive

–Use 85% un-hydrogenated liquid vegetable oil and 15% fully  hydrogenated vegetable oil (hardstock)

Use of fractions high in solids

–Derived from coconut, pal and palm kernel oils

–Prepared by reducing the temperature of an oil sample so that  the more saturated fraction solidifies

Use of trait-enhanced oils

–High oleic acid oils

–Plant breeding, sunflower and canola

Saturated Fat & Health

ŸRisk of heart disease correlates with  cholesterol level in bloodstream (serum  cholesterol)

–low density lipoproteins (LDL)

carry cholesterol to cells 

–high density lipoproteins (HDL) 

carry cholesterol away

Fat affects cholesterol regulation

– Fat consumption with cholesterol raises serum  cholesterol levels

Health

Depends on what type of saturated/unsaturated fat

 

Improved cholesterol removal

Worsened cholesterol removal

Lowers serum cholesterol

Neutral

Raises serum cholesterol

Lipoproteins

Lipoproteins transport lipids throughout body

 ket: Chylomicron (75-1200 nm) Protein poor Lipid rich

         (5-12 nm) Protein rich Lipid poor

Essential Fatty Acids

PUFA requirements

a.should make up to 3% of fatty acid intake

b.PUFA deficiencies cause growth

retardation, skin  lesions, neurological  and visual abnormalities

Role of polyunsaturated fatty acids

ω3 and ω6 fatty acids are precursors to  potent bioactive compounds

1.Prostaglandins

a.Platelet antiaggregate

2.Thromboxanes

a.Platelet aggregate

ket:
Sources of Omega Fatty Acids

Omega-6
Linoleic acid = >
Vegetable oils ( corn, sunflower, safflower, soybean, cottonseed), poultry fat, nuts, seeds.
Arachidonic acid = >
Meats, poultry, eggs (or can be made from linoleic acid)

Omega-3
Linolenic acid = >
Oils (flaxseed, canola, walnut, wheat germ, soybean)
Nuts and seeds (butternuts, flaxseeds, walnuts, soybean kernels)
Vegetables (soybeans)

EPA and DHA = >
Human milk
Pacific oysters and fish (makerel, salmon, bluefish, mullet, sablefish, menhaden, anchovy, herring, lake trout, sardines, tuna,)
(or can be made from linolenic acid)