CHAPTER ONE
INTRODUCTION
1.1 AN OVERVIEW
There is a common misconception that all fats and oils are bad for health, when in actuality the
right types of oils and fats will provide an effective energy source for the body, as well as enhance
the texture, taste and aroma of many foods. Various types of oils and fats are commonly used in
the preparation of many types of foods by methods such as cooking, baking and frying, and are
also an important component in fillings, icings, toppings and coatings. The key to a healthy diet is
to stay away from foods and oils with high levels of trans and hypercholesterolemic fats.
Unfortunately, a high-fat diet is often linked to obesity. Obesity has become a major pandemic.
Globally, the incidence and prevalence of obesity continue to increase at alarming rates. which is
subsequently related to various diseases (Lai, O. M. et al., 2016). The incidence of degenerative
diseases such as cardiovascular disease, hypertension and diabetes is also rising at an alarming
rates. While obesity can be due to a combination of genetic, psychological, socio-economic and
cultural factors, a straight-forward explanation to this is that obesity is caused by an imbalance of
energy intake as compared to energy expenditure. As human continually become more aware of
the health risk associated with obesity, more people are trying to live healthier lives, which
typically includes eating healthier.
There are speculations that the incessant increase in obesity and disease are as a result of fats and
oils. Although fats and oils are critical to a balanced diet, many people in industrialized countries
have a tendency to consume more than is needed. A major source of consumption of fats and oils
is food that has been fried or baked in cooking oil. These cooking oils absorb into the food and
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give it certain texture, colour, and palatable qualities to which people have become accustomed.
Simply eliminating this cooking oils or fried foods from the diet often leaves people feeling
unsatisfied, or decreases the flavor and palatability of foods to the customer, so that motivation to
eat such foods for a potential health benefits is short lived. So far, low fat oil substitutes have
generally proven to be unsuccessful. The public does not seem to be willing to compromise taste
for health. Healthier, more palatable edible oils may be key to controlling the incidence of obesity
and certain diseases.
Although, Oils and fats are important components of our daily diet. However, health experts have
warned that the number of fat or obese people worldwide has risen at an alarming rate. Doctors,
scientists, and nutritionists are now investigating on the role of genetics, metabolism, and drugs in
contributing to this weight-related problem, as well as new methods to treat it. This, in turn, has
directly or indirectly enhanced the very lucrative global anti-obesity market, which currently is in
excess of USD 240 billion. However, at the other end of the scale, the rapid growing rate of obesity
may bankrupt national health organizations of certain countries (Lean et al. 2016). The functional
oils and fats market has certainly benefited from all this publicity. In the past decade, rising
consumer awareness and mandatory governmental legislations on unhealthful fats have partly
surged the sales volume of functional oil and fat products.
In the past two decades, the image of fats and oils has shifted from bad to healthful (Kennedy,
1991). As is often the case in the field of nutrition, there are always new products and new
developments to stay on top of. United States Patent No. 6,004,611 discloses an edible oil
composition having unique nutritional benefits. The majority of this edible oil composition is
diglycerides, of which the 1,3 diglycerides (comprising more than 40% of the oil) are considered
to be actual beneficial component. When edible oils of triglyceride nature are digested, they are
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broken into fat components. The body packages the components into triglycerides, and transport
them to the tissues while the liver handles the excess.
Triglycerides are stored in adipose tissue until the body needs them for energy at a later time.
However, the body does not package the digested components of 1,3-diglycerides as it does the
triglycerides. Therefore, the components of 1,3-diglycerides are transported to the liver to be
metabolized.
One recent commercial development in functional edible oils and fats is a product named ‘Healthy
Econa Cooking Oil’, developed and patented by Kao Corporation (Japan) in 1999. This novel oil
contains at least 80% diacylglycerols (DAG), predominantly the 1,3-isoform, and can be used in
the same way as conventional edible oils. The most important feature of this product is its ability
to reduce and prevent fat accumulation in the body. This functional oil was a hit in the Japanese
market when it was first launched in February 1999, with demand outstripping production.
Currently, the oil is used as a key component in a variety of products such as phytosterol-enriched
cooking oil, salad dressings, margarine, canned products and bread. Sales of ‘Healthy Econa
Cooking Oil’ account for 80% of premium oils, which constitutes around 14% of the total Japanese
edible oil market worth. Being designated as GRAS (generally recognised as safe) by the US Food
and Drug Administration, the functional oil reached the US market at the end of 2002 through a
joint venture with Archer Daniels Midland Co. called ADM Kao LLC (Decatur, Illinois). The
patented process for the production of DAG in this oil involves hydrolysis of triacylglycerols in
refined edible oils, followed by 1,3-position selective esterification using 1,3-position selective
lipases (Lai O. M. et al., 2019).
Researchers at Kao have found that DAG oil has metabolic characteristics that are distinct from
triacylglycerol (TAG) oils. The consumption of DAG oil is claimed to reduce postprandial serum
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TAG levels and thus is beneficial for the prevention and management of obesity. The physiological
differences between DAG and TAG observed in animal and clinical trials are due to distinct
metabolic fates of the oils after being absorbed via the gastrointestinal tract.
Diacylglycerols (DAGs) in different degrees of purity are used as additives or carriers in the food,
medicine and cosmetic industries (Ning, L., 2018). DAG oil has beneficial effects on obesity and
weight-related disorders. Dietary DAGs exhibit anti-obesity activities and can prevent
postprandial hypertriacylglycerolemia in experimental animals and humans.
Numerous methods for the synthesis of DAG-particularly 1,3-DAG-enriched oils—have been
reported. 1,3-DAGs can be synthesized using chemical and enzymatic methods.
A detailed description on the metabolic fates of DAG and TAG is provided in this review. Unlike
conventional TAG cooking oils that contains only up to 10% (w/w) DAG, these rather light-tasting
healthful cooking oils are claimed to contain 80% (w/w) or more of DAG as the main functional
component. In this review, we look into the properties and potential health benefits and highlight
patented processes and product formulations of DAG oil.
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CHATER TWO
LITERATURE REVIEW
2.1 PALM OIL
Palm oil is an edible vegetable oil whose color ranges from yellow-red to dark-red, and is
obtained from the reddish pulp (mesocarp) of the fruits of the Oil Palm tree, especially the
African Oil Palm-Elaeis guineensis (Composition of Palm Oil, 2019). Palm oil is a fat from the
fruit flesh of species of the Oil Palm tree (Elaeis guineensis), which has a distinctive orange-red
color as a result of the relatively high amount of carotenoids it contains (Palm Oil, 2020). The
Crude Palm Oil (CPO) is used extensively in Nigeria for the cooking of soups, stews, African
salad and also in frying; it represents a major source of vegetable fat (Nnadozie et al., 1989).
Palm oil is different from Palm kernel oil (PKO), in that Palm kernel oil (PKO) is gotten from
the kernels of the oil Palm fruit.
Crude Palm oil (CPO) has a reddish color because of its high beta-carotene content. Though
Palm oil and Palm kernel oil may be from the same oil Palm tree, Palm oil has a red color while
Palm kernel oil does not because it lacks carotenoids and Palm oil contains low levels of
saturated fat (49%) while Palm kernel oil (PKO) has about 81% of saturated fats (Palm oil, n.d.).
However, when Crude Palm oil (CPO) has been refined, bleached and deodorized, it produces a
common commodity called RBD Palm oil (Refined, Bleached and Deodorized Palm oil) which
does not contain carotenoids.
Fig. 2.1 Crude Palm Oil (PKO) (source: Palm oil, n.d.)
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Fig. 2.2 Refined, Bleached and Deodorized Palm Oil (RBD Palm Oil) (source: Palm Oil, n.d.)
Table 2.1 Composition of Crude Palm Oil and Refined Palm Oil
(source: Composition of Palm oil, 2019).
The Oil Palm tree (Elaeis guineensis) produces dense bunches having a large number of fruits
and those bunches weigh 10kg and above. The tree is native to the West Africa region and was
exported to South East Asia (firstly Malaysia) around the mid-19th century (Palm Oil, 2015). Oil
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Palm grows more in humid tropics and yields more when grown at about 10 degrees north or
south of the equator. Usually, the Oil Palm tree needs approximately 3m diameter clear around
the base of each tree to allow full growth. The tree is a very productive crop that yields more oil
per square meter of land than any other form of vegetable oil producing tree on earth. (Palm Oil,
2020).
Fig. 2.3 Palm Fruits (source: Palm Oil, n.d..)
Fig. 2.4 Palm Trees (Elaeis guineensis) (source: Palm Oil, n.d.)
Palm oil is used in a many diverse ways which depends to a large extent on its form i.e. whether
it is in its crude form or refined form. Crude Palm oil (CPO) is used in the preparation of many
delicacies in Africa and Asia, it is also used in the production of some soap, animal fats and in
the production of bio-fuel, it has now what is referred as a green fuel option. It is also used in the
production of edible Palm oil cakes which is considered a medium grade protein feedstock used
in the fattening of cattle and other livestock. The Refined Palm oil is used to make pastries,
cakes, biscuits and other snacks. It can also be used to make personal care and beauty products as
manufacturers of these brands prefer Palm oil because of its cheap price. It is also useful in
industrial and home cooking and frying because of its refined color and taste and also because it
has a high smoke (Njiribeakor & Nwanya, 2017).
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2.1.1 COMPSOSITION OF PALM OIL
Palm Oil, just like any other edible oils consists of Monoacylglycerols, Diacylglycerols and
Triacylglycerols. Other components are tocopherols, tocotrienols, sterols, carotenes,
phosphatides (gums), ubiquinone, moisture, Free Fatty acids (FFA), dirt and other minor
constituents of non-oil fatty matter amongst others (Composition of Palm Oil, 2019).
2.1.1.1 TRIACYLGLYCEROLS (TRIGLYCERIDES)
Triacylglycerols is the fundamental unit of fats and oils that determines their characteristics. The
characteristics of the fats and oils are dependent on the type of fatty acid and the distribution of
its molecules in position (Composition of Palm Oil, 2019).
Triacylglycerols is a chemical compound found in Palm oil that consists of three constituting
elements which are carbon, hydrogen and oxygen. The three constituent elements make up the
molecules of fatty acids and glycerol, which on combination forms molecules of fat referred to as
triacylglycerols. The term “Triacylglycerol” refers to the combination of three (tri-) molecules of
the acyl group (from carboxylic acids) to one glycerol molecule. For fats and oils generally, the
carboxylic acids consist of fatty acids (Dekker, 2016).
Fig. 2.5 Structure of Triglycerides. (source: Composition of Palm Oil, 2019).
2.1.1.2 FATTY ACIDS
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Fatty acids are compounds having carbon and hydrogen atoms in long chains (molecules of
hydrocarbon), whereby each of the two ends have a moiety of the carboxylic acid group. When
numbering carbons in fatty acids, it starts with the carbon contained in the carboxylic group.
Fatty Acid hydrocarbons chain usually consists of carbons in even numbers (from 4 to 28)
(Refining of Palm Oil, n.d..).
While there are a large variety of fatty acids, only a select few amount of these acids are of
commercial importance, they include: lauric, palmitic, stearic, oleic, myristic, linolic and
linolenic acids. Palm oil is readily distinguishable from other oils by the high amount of palmitic
acid C (16:0) it contains. Palm oil also differs from other vegetable oils in that, it consists of
equal amounts of saturated acids (Palmitic and Stearic acids, 45% and 4% respectively) and
unsaturated acids (Oleic and linoleic acids, 40% and 10% respectively) (Composition of Palm
Oil, 2019).
Fatty acids are usually used as animal feeds or can be sold to producers of oleochemicals for
soaps production as well as the production of other specialized chemicals.
Table 2.2 Composition of Fatty acids in some edible oils. (source: oilpalmblog.wordpress.com)
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Table 2.3 Names and Properties of some saturated Fatty acids.
(source: Composition of Palm Oil, 2019).
2.1.1.3 MONOACYLGLYCEROLS, DIACYLGLYCEROLS AND FREE FATTY ACIDS
(FFA)
The Triacylglycerol content in Palm oil usually gets broken down in the presence of water and
heat in the process of hydrolysis to give more monoacylglycerols, diacylglycerols and free fatty
acids (FFA). These monoacylglycerols and diacylglycerols are negligible contents in good grade
oils, but they may be formed extensively in fruits that are stored badly as a result of hydrolysis.
The breaking down (hydrolysis) reaction, may be catalyzed by lipase (an enzyme), some metals
or it can even be autocatalytic. The very first step is partial hydrolysis, which produces
diglycerides (glycerol attached with two molecules of fatty acids) and free fatty acids
(Composition of Palm Oil, 2019).
Hydrolysis can occur in different stages. The reaction can occur in pre-harvest preparations or in
post-harvest handling and storage, in oil extraction, crude palm oil storage, and product shipping.
This hydrolysis is unwanted because it results in increase in the free fatty acid (FFA)
concentration in the unrefined crude oil. More attention need to be paid during the stages of the
refining process so as to reduce the amount of free fatty acid in the Crude Palm oil (CPO) in the
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starting as well as the finishing stages. The presence of elevated levels of free fatty acids in
Crude Palm oil (CPO) will lead to increase in refining losses (Refining of Palm Oil, n.d..).
Good grade oils with smaller amounts of monoglycerides and diglycerides are vital in
fractionation because they inhibit the formation of crystals as emulsifying agents thus making
filtration easier (Composition of Palm Oil, 2019). The industrial manufacture of monoglycerols
and diglycerols is carried out through the process of partial hydrolysis. They are generally used
as food grade emulsifier.
2.2 DIACYLGLYCEROLS
DAGs are esters of the trihydric alcohol glycerol in which two of the hydroxyl groups are esterified
with fatty acids. They can exist in two structural isomers namely, 1,2-DAG and 1,3-DAG (Fig. 1).
These isomers will undergo acyl migration to form equilibrium at a ratio of 3–4:7–6 between 1,2and 1,3-DAG (Takano and Itabashi 2017) often in the presence of an acid, alkali, or heat. 1,3DAG is more thermodynamically stable because of the steric effect of the molecule. In general,
the melting point of 1,3-DAG is approximately 10°C higher than TAG, and 1,2-DAG is
approximately 10°C lower than 1,3-DAG, of the same fatty composition. The causes of these
melting point differences are the strength of hydrogen bonding of the hydroxyl group and fatty
acid chain arrangement of the DAG isomers. 1,3-DAG has a V-shaped fatty acid chain
arrangement, while 1,2- DAG has a hairpin-shaped conformation. The type of molecular
arrangement of the DAG isomer relates to its polymorphic form. Unlike TAG polymorphism,
DAG exhibits two types of polymorphic forms. 1,2-DAG exhibits the α- and β′-forms but has no
β-form, while 1,3-DAG has no α-form but exhibits two types of β-form, β1 and the more unstable
β2 (Nakajima et al. 2016)
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Fig 1.1 Structure of Diacylglycerol
. The 1,2- DAG isoform is recognized as a metabolic intermediate that is formed after the ingestion
of triacylglycerol (TAG). The DAG contained in refined edible oils is largely converted to the 1,3isoform by migration of the acyl group during the high-temperature manufacturing process. In
most edible oils, ~70% (w/w) of the DAG is present as the 1,3-isoform as shown in Table 1.1.
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TABLE 1.1
Contents of Acylglycerols in Edible Oils of Various Origina
DAG
TAG
Total DAG
1,2- DAG 1,3- DAG
MAG
Others
(g/100 g)
Soybeanb
97.9
1.0
ND
ND
0.0
1.1
Palmb
93.1
5.8
ND
ND
< DL
1.1
Cottonseedb
87.0
9.5
ND
ND
0.2
3.3
Cornb
95.8
2.8
1.5
2.9
< DL
1.4
Safflowerb
96.0
2.1
1.2
2.7
< DL
1.9
Oliveb
93.3
5.5
ND
ND
0.2
2.3
Olive (mol%)c 18– 41
8– 20
Rapeseedb
96.8
0.8
ND
ND
0.1
2.3
Vegetable oild 98.3
1.7
0.6
1.1
< DL
ND
(Soy + Canola)
Canolad
97.1
2.9
1.0
1.9
< DL
ND
Sesamed
95.2
4.1
1.2
2.9
0.8
ND
Pure sesame
95.5
3.9
1.2
2.7
0.6
ND
Rice germd
91.2
8.8
2.7
6.1
< DL
ND
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Corn germd
95.5
4.5
1.5
2.9
< DL
ND
Pure grapeseedd 94.2
5.8
2.1
3.7
< DL
ND
DAG oile
81.4
28.4
53.0
1.2
ND
17.3
a
Abbreviations: ND, not determined; <DL, below detectable limit (<0.1 g/100g).
b
S o u r c e: Refs. 37 and 38.
c
Source: Ref. 39.
d
S o u r c e: Nishide, T., unpublished data.
DAG in Nature DAG is a natural component of glycerides in various fats and oils at levels up to
10% (w/w). Table 1.1 shows the content of DAG and other acylglycerols in edible oils of In
particular, olive oil has been used for a long time in the Mediterranean area. It was reported that
some olive oil obtained in Major area in Spain contained a high content of DAG (39). DAG is also
a main component of mono- and diglycerides, one of the popular emulsifiers used in foods.
Therefore, DAG is normally present in plant oils and in fats and oil products that have been
consumed by humans for a long period of time.
2.1 DAG Oil
DAG oil contains >80% DAG, <20% TAG, <3% monoacylglycerol (MAG), and
small amounts of antioxidants and emulsifiers to maintain quality. DAG is generally
made from fatty acids derived from vegetable oil and glycerin by using an immobilized
1,3-regiospecific lipase. The ratio of the 1,3-isoform to the 1,2- or 2,3-isoform is
~7:3 due to acyl migration during the refining process. DAG oil as cooking oil is commercially
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available in Japan and in the United States
The main nutritional functions of DAG oil vs. TAG oil are as follows:
I.
II.
A suppressive effect on postprandial serum triglyceride elevation, and
A suppressive effect on body fat accumulation. DAG oil also has unique
physicochemical properties
caused by the presence of a free hydroxyl group in the structure compared with TAG oil. The
cooking properties of DAG oil are similar to those of conventional cooking oil
2.2 Digestion, Absorption, and Metabolism
DAG can be digested by the same gastrointestinal enzymes that hydrolyze TAG. However, upon
digestion, DAG does not follow the resynthetic pathway of TAG, which includes the 2monoacylglycerol (2-MAG) pathway and the glycerol-3-phosphate (GP) pathway. In TAG
digestion, the human pancreatic lipase hydrolyzes fatty acids from the terminal positions of the
TAG molecule to form 1,2- and 2,3-DAG as intermediate products. These intermediate products
can be further hydrolyzed by the pancreatic lipase to form 2-MAG. As
such, the pancreatic lipase can also hydrolyze 1,3-DAG to form 1(3)-MAG and free fatty acids
(Kondo et al. 2018). The key characteristic of DAG metabolism lies in the formation of 1(3)-MAG
rather than 2-MAG as found in TAG metabolism.
In TAG absorption, 2-MAG will undergo re-esterification with fatty acids via the 2-MAG pathway
to reform TAG, which will then be transported as a chylomicron complex
into the blood stream via the lymphatic system. In the case of DAG, however, 1(3)-MAG is poorly
re-esterified via the 2-MAG pathway and thus has an insignificant contribution toward TAG
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resynthesis (Lehner et al. 2019). Instead, substantial amounts of 1(3)-MAG are further hydrolyzed
to free fatty acids and glycerol, which are precursors of the GP pathway, while some are reesterified to 1,3-DAG. The efficiency of DAG digestion products to convert into TAG in the small
intestines was also found to be low. Another important difference between DAG and TAG
metabolism is the substrate specificity of the DAG acyltransferase (DGAT) enzymes, DGAT-1
and DGAT-2, in the small intestines (Cases et al., 2020). DGAT is involved in the final synthetic
step of TAG by catalyzing the acylation of 1,2 (2,3)-DAG, which are products from the 2-MAG
pathway.
However, DGAT has low substrate specificity toward 1,3 DAG and therefore does not
significantly convert 1,3-DAG to TAG (Lehner and Kuksis 2019). Conclusions from these
findings on the nature of DAG digestion and absorption may explain the reduction of postprandial
TAG levels in the blood.
Numerous animal and clinical studies have all shown that ingestion of DAG oil, in comparison
with TAG oil, increases the rate of β-oxidation of fatty acids. Additionally, the activities of
enzymes involved in fatty acid synthesis, such as glucose-6-phosphate dehydrogenase,
malic enzyme, and fatty acid synthetase, were observed to significantly decrease in subjects fed
with DAG oil. On the other hand, hepatic enzymes involved in the β-oxidation pathway, such as
acylcoenzyme A (CoA) dehydrogenase, acyl-CoA oxidase, enoyl-CoA hydratase, carnitine
palmitoyltransferase, 3- hydroxyacyl-CoA dehydrogenase, 2,4-dienoyl-CoA reductase, and δ3,δ2enoyl-CoA isomerase, were found to increase in activity on a dose-dependent manner with DAG
intake. In a clinical study, it was interesting to note that the increase in β-oxidation occurred even
without any change in daily energy expenditure resulting from resting activity or activity related
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to physical exertion. It is believed that the increase in β-oxidation of DAG metabolism relates to
the corresponding reduction in body fat and serum TAG levels.
2.3 Potential Health Benefits
The ingestion of DAG oil has been shown to reduce body fat accumulation and lower serum TAG
levels. Murase et al. (2016) reported a 70% reduction in body weight of mice after 5 months on a
diet containing 30% DAG oil. Significant fat reductions surrounding the epididymal, mesenteric,
retroperitoneal, and perirenal areas were observed. However, other animal tests revealed that the
effect of DAG oil on reducing body weight was not found at low intakes (10% or less) of DAG.
To compare the effects of DAG and TAG oil ingestion on human body fat, Nagao et al. (2018)
had conducted a 16-week double-blind study on 38 healthy men with an average body mass index
(BMI) of approximately 24 kg/m2. The subjects were randomly provided with food products
that contain either DAG or TAG oil at a dosage of 10 g/day during the treatment period. The results
revealed that reductions in body weight, BMI, waist circumference, and total fat area were more
distinct in subjects consuming the DAG oil diet. In another related study, it observed similar
findings in a 6- month investigation on the effect of diets rich in DAG and TAG oils on obese men
and women with BMI of approximately 34 kg/m2. On the contrary, several studies did not find
any significant change in body fat reduction of the subjects after the treatment period
Studies investigating the effect of DAG oil on serum TAG levels in animals and humans also
showed inconsistent results. Reductions in serum TAG levels were observed in some studies while
in others, there was no change in serum TAG. It was investigated that the effect of
feeding diets containing 10% DAG oil to rats and concluded that DAG has an ability to reduce
serum TAG levels. Murata et al. (2017) suggested that the ingestion of
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DAG oil decreased serum TAG levels by retarding the chylomicron assembly that is essential for
TAG transportation. In another study, it was reported that TAG synthesis in DAG-infused rats was
less pronounced than in TAG-infused rats. On the other hand, it did not find any decrease in serum
TAG levels of rats fed with diets containing 30% DAG oil. It is interesting to note that it was found
that the DAG oil suppressed it
2.4 Oil-in-Water Type Emulsion Foods
Oil-in-water type emulsion (O/W) food products are commonly represented by mayonnaise and
salad dressings. In general, mayonnaise and salad dressings contain oil, egg yolk, vinegar, and
seasonings (salt, sugar, spices, flavors, etc.). The major difference between mayonnaise and salad
dressings is in the oil content. Mayonnaise has an oil content of 65–85% (w/w), while salad
dressing has less than 60% (w/w) oil. The application of DAG oil in O/W products was first
patented by Nomura et al. (1992). According to the invention, the O/W product has an oil phase
comprising of 30–100% (w/w) DAG with a melting point of 20°C or less. The O/W composition
is claimed to exhibit a rich fatty savor even at a low fat content. Several years later, Kawai and
Konishi (2000) describes an O/W composition that has excellent storage stability, good
appearance, taste, and physical properties. The composition has an oil phase that is comprised of
30% (w/w) or greater of DAG oil and a yolk wherein the ratio of lysophospholipids to the whole
phospholipids is at least 15% (w/w) based on phosphorous content. Shiiba et al. (2002) provided
further improvements by disclosing an O/W composition that has excellent shelf stability at low
temperatures comprising at least 20 (w/w) and 0.5–5% (w/w) of a crystallization inhibitor. The
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crystallization inhibitor is a polyglycerol fatty acid ester, sucrose fatty acid ester, or sorbitan fatty
acid ester.
2.5 Water-in-Oil Type Emulsion Foods
The other form of emulsified food product has a water-in oil type emulsion (W/O). Examples of
such products are margarine, spreads, butter cream fillings, and icings used in baking and the
confectionery industry. Mori et al. invented a W/O-emulsified fat composition that has good
stability and spreadability and is suitable for use as a margarine. The W/O composition is made up
of 40 to less than 95% (w/w) of DAG and 5 to less than 60% (w/w) of TAG, wherein the DAG
comprises of 0.5 to less than 20% (w/w) DAG containing two saturated C14–C22 fatty acid groups,
20 to less than 55% (w/w) DAG containing one saturated C14–C22 fatty acid group and one
unsaturated C14–C22 fatty acid group, and 25 to less than 70% (w/w) DAG containing two
unsaturated C14–C22 fatty acid groups, and the weight ratio of total C14 and C16 saturated fatty
acid groups in DAG to total C18, C20, and C22 saturated fatty acid groups in DAG is in the range
from 1 to 8. Another W/O composition claimed to have excellent flavor release during the time of
ingestion was invented by Masui and Konishi (2001). According to this invention, it is
claimed that 30% (w/w) of the W/O oil or fat composition is being able to reverse in phase within
1 min after coming into contact with water at 36°C, thereby releasing the flavor
component. The W/O composition comprises of water as the aqueous phase, 15% (w/w) or more
of DAG as the oil phase, and a demulsifier, which comprises at least a polyglycerol fatty acid ester
having a hydrophilic–lipophilic balance (HLB) value of 8 or more, a water-soluble decomposed
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protein, lysolecithin having a HLB value of 8 or more, a sucrose fatty acid ester having a HLB of
5 or more, a MAG organic acid ester having a HLB of 8 or more, and a sorbitan fatty acid ester
having a HLB of 8 or more. A W/O composition by Masui and Yasunaga (2001) describes a W/O
product that is stable in spite of containing a high water content and has good storage and mouth
feel. The product composition comprises of water as the aqueous phase, 35– 95% (w/w) of DAG
having a melting point of below 20°C, and the remainder as TAG, which is composed of 13–60%
(w/w) palmitic acid and 5% (w/w) or less of fatty acid having 12 carbons or lower, as the oil phase.
Additionally, the TAG has to possess a stable polymorphic form of β.
2.6 DAG Oil Composition Containing Phytosterols
Phytosterols are lipid compounds that have been shown to lower serum cholesterol levels in
humans (Ling and Jones 1995; Jones et al. 1997). Because of its limited solubility in oil (approx.
1% w/w) and insolubility in water, normal intake of phytosterols are not efficiently absorbed by
the intestines and therefore ineffective in lowering serum cholesterol levels. Efforts were made to
increase solubility of phytosterols in oil by converting it into phytosterol fatty acid esters (Hendriks
et al. 1999). However, Meguro et al. (2001) reported that phytosterols can achieve higher solubility
in DAG oil without the need of esterification. Several patent literatures were found on DAG oil
composition containing dissolved phytosterols.
Goto et al. (2000a, b) claimed that the solubility of phytosterol can be increased by 1.2–20% (w/w)
when 15% (w/w) or more of DAG oil is used as solvent. Additionally, the authors claimed that
80% (w/w) or more of DAG oil can dissolve 0.05–20% (w/w) of phytosterols. However, 55%
(w/w) or more of unsaturated fatty acids have to be present in the DAG oil for effective
solubilization of the phytosterols. In another patent (Goto et al. 2001), an oil composition
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containing 15% (w/w) or more of DAG and up to 2,000 ppm of tocopherol was reported to
effectively dissolve 1.2–20% (w/w) of phytosterols. The DAG component is comprised of at least
70% (w/w) unsaturated fatty acids. Nakajima et al. made further improvements of phytosterol
solubility in DAG oil in a disclosure whereby an oil composition containing 15–95% (w/w) is used
to dissolve 2–10% (w/w) of phytosterol and the resultant oil composition remains a transparent
liquid at temperatures of 0–30°C.
2.7 Practical Use of DAG Oil.
DAG oil became commercially available as a cooking oil (Econa Cooking Oil, Kao Corporation,
Tokyo, Japan) in March 1999 in Japan, and greater than100,000 tonnes were consumed, making it
a top-selling brand as of December 2003. In the United States, it is sold in Chicago and Atlanta
under the name Enova Oil as ofnDecember 2003.
DAG is used in various fats and oil products in Japan. DAG has been applied to spreads (Snow
Brand Milk Products Company), bread (Yamazaki Baking Company), and canned tuna (Hagoromo
Foods Company) in 2000. DAG cooking oil containing phytosterols and DAG salad dressing (Kao
Corporation) became commercially available in 2001, a mayonnaise-type product (Kao
Corporation) and curry roux (House Foods Corporation) in 2002, fried tofu (Satonoyuki
Company), fried noodles (Sanyo Foods Company), and chips (Calbee Foods Company) in 2003.
2.7.1 Shortenings
DAG also finds an application in the formulation of shortenings. Doucet and Olathe (1999)
invented a shortening composition comprising a nonhydrogenated vegetable oil and a stearine
fraction containing 50–60 mol% of DAG. It is claimed that the shortening formulation has a
21
synergistic amount of solids and crystal matrices that imparts superior organoleptic properties to
the food product, without the incorporation of trans-fatty acids commonly found in partially
hydrogenated fats. Concomitantly, Doucet et al. (1999) claimed that the above effects can also be
made possible with the addition of MAG composed predominantly of saturated fatty acids.
2.7.2 Frying Applications
Because DAG has a lower molecular weight than TAG, DAG oil has a significantly lower smoke
point (30–40°C) than TAG oil with similar fatty acid compositions. Therefore, frying applications
with DAG oil will be problematic. Several DAG compositions suitable for use as frying oil have
been reported. Sakai et al. (2002a) reported a fat composition containing at least 15% (w/w) of
DAG, a fatty acid L-ascorbic ester, and a component such as catechin or a natural plant extract
such as rosemary, sage, and turmeric extracts. The authors claimed that the DAG composition has
excellent stability toward oxidation, while providing good flavor and appearance. Another DAG
composition reported by Sakai et al. (2002b) contains 15% (w/w) or more of DAG and 70 ppm or
more of one or more types of organic carboxylic acids such as two- to eight-carbon
hydroxycarboxylic or dicarboxylic acids and their derivatives thereof. The composition is claimed
to resist thermal oxidation or hydrolysis after prolonged heating or storage, as well as to reduce
smoking when the oil composition is used for frying purposes.
2.7.3 Foods Containing DAG Oil
Foods that are prepared with or contain DAG oil are summarized in this section. Mori et al. (1999b)
disclosed fried food with a fat composition containing 55 to less than 95% (w/w) of DAG, which
composed of 55 to less than 93% (w/w) of unsaturated fatty acids. The authors claimed that when
the food is fried with DAG oil of such composition, the resultant fried food will have a low water
22
content and will not likely get moist and reduce in crispiness over a prolonged period of time. The
fried foods that are covered in this patent are fried cakes, French fried potatoes, fried chicken, and
doughnuts. A disclosure from Mori and Watanabe (2000) described a food that is comprised of
0.5–85% (w/w) DAG with C2–C10 fatty acids. When ingested, the food composition is claimed
to possess good organoleptic properties, as well as to reduce body fat accumulation and provide
energy at times of exhaustion and fatigue.
Another DAG-containing food product as reported by Kudo et al. (2002) is fried or baked potatoes,
which comprise of 3–50% (w/w) of oil or fat, wherein the DAG content is 15% to less than 50%
(w/w). The fatty acids of the DAG oil are composed of 15–100% (w/w) of 5-3 unsaturated fatty
acids of less than 20 carbon atoms. Similar to the findings of Mori et al. (1999b), potatoes fried or
baked in such a DAG oil composition was reported to provide a product that has a low water
content, favorable texture and taste, and good storage stability.
2.7.4 Ice Cream Coating Fats
Ice cream coating fats are generally TAG of medium-chain fatty acids, such as lauric acid-rich
coconut oil. The first use of DAG as an ice cream coating fat was reported by Cain et al. (1999).
The fat composition is comprised of 50–90% (w/w) DAG and 10–50% (w/w) TAG of vegetable
origin. The DAG oil is composed of 75–90% (w/w) di-unsaturated DAG, less than 5% (w/w) disaturated DAG, and 10–25% (w/w) DAG with one unsaturated and one saturated fatty acid. The
TAG composition in this fat composition is such that the sum of tri-unsaturated and di-unsaturated
TAG is at least 50% (w/w). According to this invention, the ice cream coating fat had resulted in
a product that is softer and less brittle but had quicker and smoother meltdown, than cocoa butterbased coating fats.
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2.8 Manufacturing Process.
The performance requirements for the industrial manufacturing of DAG include high purity and
low-cost production. DAG was prepared from fatty acids and glycerin by esterification using an
immobilized 1,3-regiospecific lipase (Watanabe, T., et al. 2018). The manufacturing flow can be
divided into two main processes, i.e., the production of DAG through enzymatic reactions and the
refining process that is typically used in the production of edible oils. Enzymatic esterification is
an efficient route for
producing oil with a high DAG content. DAG obtained in the enzymatic reaction consists mainly
of the 1,3-isomer; some of the 1,3-isomer is isomerized to the 1,2-isomer during the refining
process in which some heat is generated. Finally, DAG consists of ~70% 1,3-isomer and 30% 1,2isomer. DAG is currently being produced in Japan and in the United States and the current
production volume is >30,000 tonnes/year
2.9 Safety and Regulation.
The safety of DAG has been established by various studies in humans, in vitro, and in animals.
The Ministry of Health and Welfare of Japan approved DAG oil as Food for Specified Health Use
(FOSHU) in 1999. In 2000, the Japanese Society of Human Dry Dock, a professional association
of Japanese physicians, recommended that DAG play a role in improving human health. In the
United States, DAG was submitted to the FDA as a Generally Recognized As Safe (GRAS)
substance, and the FDA indicated that there was no question regarding safety.
24
CHAPTER THREE
CONCLUSION
3.1 CONCLUSION
DAG, a natural oil component that has unique nutritional properties, “less likely elevates
postprandial serum triglycerides and is less likely to become body fat compared to TAG.” The
physicochemical properties of DAG oil as a liquid oil are nearly the same as those of TAG oil.
However, because DAG has a hydroxyl group in the molecule, some physicochemical properties
differ from those of TAG. These specific properties, which are not associated with TAG, may
require specific devices and technology to be able to apply DAG oil to food products; in some
cases, however, this would be useful for the development of new products. DAG is an attractive
new food material not only for its nutritional properties but also for its physicochemical
properties.
Scientific and practical information regarding the nutritional properties, clinical efficacy, safety,
manufacturing, and application technologies of DAG oil is summarized in this book and will be
useful in increasing our understanding of the nature of DAG and the use of DAG oil to maintain
a healthy body weight and prevent lifestyle-related diseases caused by obesity.
Numerous scientific reports have shown the effectiveness of DAG in preventing body fat
accumulation and obesity related disorders. The commercial potential of DAG has prompted
various patent publications on production technologies and product applications of DAG oil.
However, greater emphasis is required to further reduce the overall cost of DAG oil to meet
consumer expectations.
25
Further analysis is expected to allow more scientific evidence and information to be accumulated
concerning the efficacy, safety, mechanism of action, and application technologies that may
provide new insights for managing a lifestyle–related chronic disease such as the metabolic
syndrome. At the current growth rate of obese population throughout the world, it can be
expected that the global market demand for DAG oil will increase in the future.
26
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