Content uploaded by Adel Gabr Abdel-Razek
Author content
All content in this area was uploaded by Adel Gabr Abdel-Razek on Jun 13, 2020
Content may be subject to copyright.
Fats and Oils:
Structures and Functions
By
Dr. Adel Gabr Abdel-Razek
National Research Centre
6 December 2017, Cairo, Egypt.
Today, we drink low-fat milk and eat leaner meats,
but we eat more fat from creams, cheese, sauces, and take-out foods.
Introduction
The Functions of Lipids and Fats?
•Lipids, a chemical family that includes cholesterol,
phospholipids, fats and oils, make up a major part of the
average human diet.
•Fats and oils are not just a caloric powerhouse,
•but they also serve many:
•Chemical, Physical, and Nutritional
•Functions in the foods we eat.
What role do dietary fats play in the diet?
•The fats that we get from food are vital to good health.
•They provide energy and essential fatty acids for healthy skin and important
hormone-like substances.
•Fats also carry and help the body absorb the fat-soluble vitamins A, D, E and K.
What’s more, dietary fats help us feel satisfied following meals.
FAT
Ten of the Most Important Functions That Fats Serve in Food
1. Appearance
•Fats and oils can alter a food’s appearance by creating a glossy or moist visual texture.
•The ability of fat to refract light is also responsible for the opaque appearance of milk.
•Fats also aid in the browning process of many foods, giving them an appealing golden brown color.
2. Emulsions
•Fats and oils are an important component in most emulsions.
•Emulsions are the dispersion of a fat or oil into water (or vice versa) O/W or W/O.
•There are many emulsions in the culinary world including salad dressings, mayonnaise
and cheese sauces.
•Emulsifying fat into a liquid produces unique flavor and texture qualities.
3- Flavor
•Fat has the unique ability to absorb and preserve flavors.
•Fats also contain compounds that lend specific flavors of their own.
•The way fat coats the tongue and allows flavors to linger can also alter
a flavor experience.
The species-specific flavors of meats are carried in their lipids; the flavors of beef and lamb are
indistinguishable,if the lipids are stripped from the meats.
4- Heat Transfer
•Fats provide one of the most efficient modes of heat transfer during cooking.
•From deep fat frying to sautéing in a skillet or wok, hot oil is able to transfer high levels of heat to the surface of
food without overheating the interior portions.
•Using fats and oils to transfer heat also facilitates crust formation.
5- Melting Point
•The type of fat used in a product often determines the melting point of the final product.
•A melting point is the temperature at which a substance changes from a solid to aliquid.
•This characteristic is especially important for items like chocolate,frosting, and salad
dressings.
•Saturated fats, like butter and animal fats, are solid and room temperature, which make them
perfect for using solid foods like chocolate and frosting.
•The low melting point of vegetable oils allows salad dressings to stay in liquid form when
refrigerated.
6- Nutrition
•Fats are the most calorie dense compound in food, weighing in at over twice the calories per
gram of proteins or carbohydrates.
•While this may not be seen as an advantage in today’s modern society, the ability to provide
energy dense food items is still necessary in many parts of the world.
•Fat is an effective method of delivering calories when needed.
•Fats are also important for delivering fat-soluble vitamins such as Vitamins A, E, D, and K.
7- Satiety
•Fats play an important role in making foods satisfying or making us feel full.
•Because fats take longer to digest than carbohydrates or proteins, high-fat foods stay in the
stomach longer and delay the feeling of hunger.
8- Shortening
•Shortening is not just the name of a solid, shelf stable fat but it is also the term used to describe
fat’s ability to make baked goods tender by impeding the formation of gluten strands.
•Normally, as bread dough is kneaded the gluten (wheat protein) begins to join and form long
elastic strands, which give strength and a chewy texture to the bread.
•When fat is added to dough, like in biscuits and pie crusts, the fat gets in the way of the gluten
formation, therefore keeping the final product tender and flakey.
9- Solubility
•While fats and oils are not soluble in water, there are other chemical
compounds that are only soluble in fats.
•Many of these fat-soluble compounds are responsible for foods flavor
and even vitamin content.
•Including fat in food allows for maximum flavor and a wider range of
nutritional content.
10. Texture
•Fats and oils have a texture all their own but are also responsible for
tenderizing baked goods via the shortening process.
•Fat provides a very specific, lubricating mouthfeel, which is why
most dry crackers or chips are served with high-fat content dips or
spreads.
Fats and Oils Structure and Function
•Emerging information on changing technologies, uses and health benefits of this
macronutrient is provided.
•The structure of lipids affects their nutritional and functional properties.
•The types of fats and oils used in formulations have specific impacts on sensory,
nutritional and functional aspects of finished products.
Function Follows Form
•The structure of the lipid determines its function in the cell.
•Most of the lipids that have value for food products are in the triglyceride,
energy-storage form.
•Triglycerides are composed of three fatty acids attached by an ester linkage to a
glycerol backbone.
•The order in which the fatty acids are attached to the glycerol backbone is highly
structured in nature.
Figure 5.5
Fatty Acids Vary in Shape
Unsaturated fatty acids form two different shapes
Portion of Figure 5.7
Triglycerides
Three fatty acids connected to a glycerol backbone
Triglycerides--Functional Fats/Shortenings
The difference between fats and oils is driven by their fatty acid composition and the
arrangement of the fatty acids in the triglyceride molecule.
Fatty acid chain length and the number and placement of double bonds in the fatty acid chain
determine the melting profile of fats and oils.
The melting profile determines the functionality and sensory characteristics of a fat.
As an example,properly crystallized cocoa butter in chocolate has a sharp melting point
slightly below body temperature, which gives chocolate its unique properties of melting and
cooling on the tongue.
The fatty acid composition of cocoa butter is about two thirds saturated fatty acids (palmitic
and stearic acids) and one third unsaturated (oleic with a small amount of linoleic acid).
Choosing solid shortenings for food applications is more complicated
than liquid oils, as the shortening’sstructure impacts its function, such
as flaky texture in pastry and smooth mouthfeel in breads.
Solid shortenings range from very hard and highly saturated to very
soft and plastic with a high degree of unsaturation.
•For many years, much of this functionality was achieved through the use of
trans fats.
•Trans fats are unique, in that they are unsaturated lipids that function much like
their saturated counterparts.
•While small amounts of trans fats are naturally occurring in some foods, such as
butter, they primarily are produced through partial hydrogenation of unsaturated
oils, such as soybean oil.
As the food industry rapidly moved away from using trans fats because of perceived
health concerns, lipid scientists had to scramble to find replacements that provided the unique
functionality that trans fats offered.
Palm and palm kernel oils have become the primary
sources for zero-trans alternative shortenings.
This is because they have a high degree of shorter-chain saturated fatty acids,
with lower melting points, that can be manipulated to provide crystalline
structure with a range of melt profiles.
The move to palm-based shortenings:
fats and oils manufacturers now have built much of the functionality into
palm-based shortenings, to the point that they are now comparable to their
trans counterparts.
This has been done through fractionation and recombination of the
triglycerides, along with rearrangement of the fatty acids on the
triglyceride molecules.
•While palm-based shortenings now are working well in foods, there
continue to be concerns around their saturated fat content.
Recently, palm-based shortenings are being transformed from
containing as much as 64-69%saturated fat to as low as 24-46%
saturated fat with equal functionality.
This is being done by using unsaturated fractions of soybean and
canola oils in combination with inter esterified palm fats.
Oil palm, is a unique crop as its fruit produces
two distinct types of oils;
Crude palm oil from the mesocarp & Crude palm kernel oil from the kernel.
Conclusion:
The structure of the lipid determines its function
The roles of fats and oils play in food products and in human nutrition continue to
grow and change.
Above all, it’s important to remember that the principles of balance,variety and
moderation form the basis for a healthful diet. Along with appropriate amounts of
whole grains, vegetables, fruits,
Recommendation:
The cooperation between the food manufacturer with food scientists and
nutritionists is resulting in producing more healthful, satisfying food products.
References:
Wendy M. Willis, Robert W. Lencki, and Alejandro G. Marangoni. Lipid Modification Strategies in the Production of
Nutritionally Functional Fats and Oils. Critical Reviews in Food Science and Nutrition, 38(8):639–674 (1998)
Beermann, C. et al. 2003. Lipids Health Dis. 2:10.
Dean, W., and English, J. 2010. Nutrition Review. www.nutritionreview.org/library/mcts.php.
Gaullier, J.M. et al. 2004. Am J Clin Nutr. 79:1118-1125.
Larsson, K. et al, 2006. Lipids: Structure, Physical Properties and Functionality: Volume 19. The Oily Press Lipid Library.
Stauffer, C.F. 1996. Fats & Oils. Eagan Press, St. Paul, MN, U.S.
Tricon S., et al. 2004. Am J Clin Nutr. 80: 614–20.
Zeisel, S.H. 2000. J Am Coll Nutr. 19:528S-531S.
Zulet, M.A., et al. 2005. J Physiol Biochem. 61: 483–94.
Thanks
For
Your Attention
