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Fats and Oils: Structures and Functions

  • National Research Centre, Dokki 12622; Cairo; Egypt
Fats and Oils:
Structures and Functions
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.
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.
Whats more, dietary fats help us feel satisfied following meals.
Ten of the Most Important Functions That Fats Serve in Food
1. Appearance
Fats and oils can alter a foods 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
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
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
fats 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
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
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 shorteningsstructure 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.
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,
The cooperation between the food manufacturer with food scientists and
nutritionists is resulting in producing more healthful, satisfying food products.
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Your Attention
The demand for lecithin has increased due to the need for plant-derived products, its important role in health benefits, and the wide range of industrial applications. However, most studies with lecithin use allergenic sources such as soy and egg yolk. Lecithin can be used in the crude form or modified with chemical by the bleaching process in order to quality proprieties. Therefore, we produced lecithin from a non-allergenic source (rice bran oil) by water degumming and evaluated the physicochemical and nutritional properties of natural and bleached lecithin by addition of hydrogen peroxide in an industrial scale. The physicochemical parameters indicated the quality of 12 lecithin samples. From these, 5 and 2 simples of natural and bleached lecithin, respectively, achieved FAO quality recommendations (acid value < 36 mgNaOH/g; hexane insoluble <0.3%; acetone insoluble from 50 to 60%; peroxide value < 10 meq/kg; and moisture <1%). From the multivariate analysis, it was observed that the bleaching process resulted in the improvement of physicochemical parameters, reduction of moisture and depigmentation of lecithin. Natural lecithin showed a greater tendency to accumulate phospholipids, tocopherols, tocotrienols, palmitic, stearic, and linolenic acids, while bleached lecithin stood out for accumulating γ-oryzanol, δ-tocotrienol, oleic and linoleic acids. In this paper, we suggest that the by-product of rice bran oil is a potential source to produce a non-allergenic, nutritious and safe lecithin, especially when the bleaching process is applied, which can contribute to quality enhancement on an industrial scale.
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The amount and quality of dietary fatty acids can modulate the fat metabolism. This dietary intervention is based on the different metabolic pathways of long-chain saturated fatty acids (LCFA), which are mostly stored in adipocytic triacylglycerols, medium-chain fatty acids (MCFA) which are preferentially available for hepatic mitochondrial beta-oxidation and n-3 long-chain polyunsaturated fatty acids (n-3 LCPUFA) suggested to modulate fat oxidation and storage by stimulating the peroxisomal beta-oxidation. Combined dietary MCFA and n-3 LCPUFA without LCFA may synergistically stimulate fatty acid oxidation resulting in blood lipid clearance and LCFA release from adipocytes. In a short term, parallel, randomized, double-blind trial effects on the fatty acid metabolism of 10 healthy volunteers (Body Mass Index 25-30) of a formula containing 72% MCFA and 22% n-3 LCPUFA without LCFA (intake: 1.500 kcal/day; fat: 55.5% of energy) were measured in comparison to an isoenergetic formula with equal fat amount and LCFA dominated lipid profile. The plasma triacylglycerol (p < 0.1) and cholesterol (p < 0.05) content decreased in the test group. The n-3/n-6 LCPUFA (> or = C 20) ratio increased (p < 0.0001) after 4 days treatment. The LCFA content was similar in both groups despite missing LCFA in the test formula indicating LCFA release from adipocytes into the plasma. Both groups significantly reduced body weight considerably 4 kg (p < 0.01) and fat mass up to 50% of weight loss (p < 0.05). Combined dietary 72% MCFA and 22% n-3 LCPUFA without LCFA stimulate the fatty acid oxidation and release from adipocytes without affecting any safety parameters measured.
Rapid improvements in the understanding of the nutritional requirements of both infants and adults has led to new developments in the modification of fats and oils. Specific targets include the improvement in growth and development of infants, treatment of disease in adults, and disease prevention. Efforts have been focussed on the production of structured lipids using medium-chain acids and long-chain polyunsaturated fatty acids (PUFAs), as well as the concentration of long-chain PUFAs from new and existing sources. Short- and medium-chain fatty acids are metabolized differently than long-chain fatty acids and have been used as a source of rapid energy for preterm infants and patients with fat malabsorption-related diseases. Long-chain PUFAs, specifically docosahexaenoic acid and arachidonic acid, are important both in the growth and development of infants, while n-3 PUFAs have been associated with reduced risk of cardiovascular disease in adults. Based on the requirements for individual fat components by different segments of the population, including infants, adults, and patients, ideal fats can be formulated to meet their needs. By using specific novel fat sources and lipid modification techniques, the concentrations of medium-chain, long-chain saturated, and long-chain polyunsaturated fatty acids as well as cholesterol can be varied to meet the individual needs of each of these groups. While genetic modification of oilseeds and other novel sources of specific lipid components are still being developed, chemical and lipase-catalyzed interesterification reactions have moved to the forefront of lipid modification technology. Fractionation of fats and oils to provide fractions with different nutritional properties has potential, but little work has been performed on the nutritional applications of this method. The choice of suitable lipid modification technologies will depend on the target lipid structure, production costs, and consumer demand. A combination of some or all of the present lipid modification techniques may be required for this purpose.
Conjugated linoleic acid (CLA) is reported to have weight-reducing and antiatherogenic properties when fed to laboratory animals. However, the effects of CLA on human health and, in particular, the effects of individual CLA isomers are unclear. This study investigated the effects of 3 doses of highly enriched cis-9,trans-11 (0.59, 1.19, and 2.38 g/d) or trans-10,cis-12 (0.63, 1.26, and 2.52 g/d) CLA preparations on body composition, blood lipid profile, and markers of insulin resistance in healthy men. Healthy men consumed 1, 2, and 4 capsules sequentially, containing either 80% cis-9,trans-11 CLA or 80% trans-10,cis-12 CLA for consecutive 8-wk periods. This phase was followed by a 6-wk washout and a crossover to the other isomer. Body composition was not significantly affected by either isomer of CLA. Mean plasma triacylglycerol concentration was higher during supplementation with trans-10,cis-12 CLA than during that with cis-9,trans-11 CLA, although there was no influence of dose. There were significant effects of both isomer and dose on plasma total cholesterol and LDL-cholesterol concentrations but not on HDL-cholesterol concentration. The ratios of LDL to HDL cholesterol and of total to HDL cholesterol were higher during supplementation with trans-10,cis-12 CLA than during that with cis-9,trans-11 CLA. CLA supplementation had no significant effect on plasma insulin concentration, homeostasis model for insulin resistance, or revised quantitative insulin sensitivity check index. Divergent effects of cis-9,trans-11 CLA and trans-10,cis-12 CLA appear on the blood lipid profile in healthy humans: trans-10,cis-12 CLA increases LDL:HDL cholesterol and total:HDL cholesterol, whereas cis-9,trans-11 CLA decreases them.
  • J M Gaullier
Gaullier, J.M. et al. 2004. Am J Clin Nutr. 79:1118-1125.
  • K Larsson
Larsson, K. et al, 2006. Lipids: Structure, Physical Properties and Functionality: Volume 19. The Oily Press Lipid Library.
  • S H Zeisel
Zeisel, S.H. 2000. J Am Coll Nutr. 19:528S-531S.