Partially Hydrogenated Fat in Bakery & Shortening: Good or Bad?
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| Figure 1: Various types of vegetable oils http://www.lamsoon.com.my/images/naturelCookingOil03.jpg |
Semi/solidified vegetable fat is produced through the process of hydrogenation which converts liquids oil into solid or semisolid fats in the presence of heat, catalysts such as nickel and hydrogen gas. As vegetable oil is liquid due to the presence of double bonds, therefore this process causes the double bonds to become saturated and at the same time become trans configuration. The degree of hydrogenation can be conducted partially or completely depending on the final food applications. Therefore, the form of the fat can be either in solid form or semisolid form depending on the degree of hydrogenation.
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| Figure 2:The chemical reaction of hydrogenation |
Moreover, the solid fat contents are also important in the bakery products in a certain amount. They provide the pliability to dough as well as giving layers and spreading the distribution of fat in the bakery products. At the same time, they also contribute to unique properties in terms of soft texture, aeration, volume, dimensional structure, freshness and mouthfeel of the foods at room temperature.
Shortening is often used in the baking industry as a solid fat component. It is a 100% fat product that exists in solid at room temperature. It was introduced into U.S food supply in 1911 by Procter and Gamble who launched Crisco shortening in which “Crisco” represented the phrase “Crystallized cottonseed oil”. This vegetable shortening was produced through partial hydrogenation and back then used as a low-cost substitute for lard. Moreover, this shortening does not not require refrigeration which is why most food manufacturers prefer this type of shortening.
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Figure 3&4:Vegetable shortening (Left)vs. Lard (Right)
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Bakery products produced using the shortenings have markedly affected the processing steps of bakery production. As the shortening contains two components such as the liquid and solid, both of these components have different functions and properties in the bakery products in a way that the liquid component imparts excellent lubricating effect to improve the mixing process. On the other hand, the solid component is responsible for the entrapment of air bubbles during mixing, resulting considerably good volume of the product. These wonderful properties brought by the shortenings are absolutely necessary in bakery products such as cakes, cookies, breads and etc in order to provide good quality of the products in terms of lubrication, texture, structure and flavour.
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| Figure 5: Margarine vs. Shortening https://i.pinimg.com/originals/79/8d/a1/798da14656624865e87a307cdc586112.jpg |
However, according to studies, trans
fats in the partially hydrogenated fats have been found to increase low-density
lipoprotein (LDL) and reduce high-density lipoprotein (HDL). They adversely
increase the risk of coronary heart disease (CHD) which may be due to the
straight configuration of trans fats that resembles saturated fats.
The intake of trans fat from
partially hydrogenated fat is undoubtedly high due to its versatile usage and
low cost. Based on data reported by US Food & Drug Administration (FDA)
(2003), there were as high as 79.4% trans fat intake was originated from the
products containing partially hydrogenated fats. The major contributors to
total trans fat intake were margarine (16.56%), cakes and related products
(23.82%), cookies and crackers (9.78%), fried potatoes (8.32%), chips and
snacks (4.81%), and household shortening (4.28%). The remaining 20.6% trans fat
intake was contributed by animal products.
Since trans fats are widely used in
the food industry as well as increasing studies show that trans fats have
significant bad effects on the health issues, FDA has taken a step which
required the food manufacturers to declare the amount of trans fat on the
nutrition labels effectively on 1st January 2006. The action taken
by FDA is expected to decrease 0.1% in total trans fat intake by the
adults. Following 18th June
2018, FDA has enforced the regulation that all the manufacturers must ensure
that trans fats or partially hydrogenated oils are completely removed from
their products. On the other hand, Malaysia has less stringent regulation
compared to FDA. The Ministry of Health, Malaysia, only requires the mandatory
declaration on the amount of trans fatty acids as well as the amount of
saturated fatty acids, monounsaturated fatty acids and polyunsaturated fatty
acids on the nutrition labelling if there is a claim made based on the amount
and/or types of fatty acids.
Alternatives to trans fats are eagerly researched by the researchers to replace partially hydrogenated fat so that the alternatives can provide the similar functional properties as trans-fat. Margarine and shortenings are commonly used partially hydrogenated fat used in bakery products. They are visco-elastic semi-solid food products comprising liquid oil and solid fat. Therefore, palm oil is a suitable candidate to replace the partially hydrogenated fat since it is naturally semi-solid at room temperature. The formation of semi-solid is due to the liquid oil that has been entrapped in a crystal network structure.
The palm oil can be fractionated into
two phases such as palm olein (liquid phase) and palm stearin (solid phase)
through fractional crystallization. Palm olein is then separated from the palm
stearin through filtration or centrifugation. The fractionation involves the
physical separation which is based on the melting point or solubility of fat crystals
in oil. The palm olein is commonly utilised as culinary oil. It is mainly in
triacylglycerides (TAG) of POO (Palmitic, olein, olein) which represents the
liquid phase that can impart the properties of plasticity of the products in
the lower temperature range. Meanwhile, palm stearin which is the solid
fraction is used in food formulations such as margarine and shortening. It is
mainly in TAG of PPP (Palmitic, palmitic, palmitic) which represents the solid
phase that can provide the strength or structure to the products.
Fractionation can be conducted in
single or multiple steps to obtain different palm-based fractions. This is
because palm oil has distinctive composition of low, medium and high melting
point TAG. Hence, this allows the selective fractionation of palm oil to
produce low, medium and high melting fractions. In this case, medium and high
melting fractions will be major contributor to replace trans fat in partially
hydrogenated fat.
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Figure 7: Multiple step of dry fractionation
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Medium palm mid fractions refer to soft and hard palm mid fractions that have melting point below 37 °C. Soft palm mid fractions (Melting point: 28-32 °C) are obtained through double fractionation of palm olein whereas hard palm mid fractions (Melting point: 31-32 °C) are obtained through the fractionation of soft palm mid fractions.
Moving on to the high melting fractions, these fractions refer to three types of palm stearins which are soft, hard and very hard. Soft palm stearins (Melting point: 40-46 °C) are produced through double fractionation of palm stearins in which they are frequently used as major components in food products such as shortenings and margarines blended with liquid oil. Hard palm stearins (Melting point: 52-56 °C) are acquired through single fractionation of palm oil. These palm stearins provide the structure for margarines and shortenings. For very hard palm stearins (Melting point: 59-62 °C), it has high solid fat content in which they are more than 80% between 25 °C and 40 °C. Thus, only a small quantity of less than 5% of the fractions are added into the formulation of margarine to improve the stability as well as withstanding the deformation of texture.
By
blending palm oil and palm stearin in certain ratio such as palm stearin/palm
oil (20:80 and 40:60), the fatty acid compositions of the shortenings are
almost similar to the commercial shortening and commercial dough fat. This can
be further supported by a research that a 100% palm-based shortening consisting
of 20% palm stearin and 80% palm oil imparted an excellent performance compared
to hydrogenated commercial shortening. Furthermore, margarines used in the
bakery products are obtained using different combinations of palm oil fractions
without any presence of trans fat. These industrial margarines can be applied
in certain food applications namely cakes, pastries, puff pastries and etc. Besides
blending with palm-based products, the palm stearin can also be blended with
other vegetables oils such as sunflower, cottonseed or soybean oil to produce
shortenings without the process of hydrogenation. However, formulations that contain
high amount of palm oil will face post-hardening problem due to an increase in
solid fat content upon storage. Therefore, interesterification can also be
adopted to solve the post-hardening problem.
Interesterification can also be used
as a way to replace the trans-fat in the hydrogenated fats apart from solving
the post-hardening problem in palm-oil based products. The liquid fraction such
as palm olein can be interesterified to be used in solid-fat formulations such
as shortenings for bakery purpose. This process can be conducted chemically or
enzymatically. Chemical interesterification involves the usage of chemicals such
as sodium methoxide to produce complete randomized position of the acyl groups
in the TAG. In contrast, enzymatic interesterification utilises microbial
lipases as the catalyst to modify fatty acids in sn-1,3 position. Yet,
enzymatic interesterification is costly since it selectively modifies fatty
acids in sn-1,3 position and produces more natural fats. Studies have shown that
chemical interesterification have indeed produced fats with a wide range degree
of plasticity, allowing them to be used in the formulation of commercial
products such as shortenings and fats used in bakery.
More and more palm oil products have
been used to substitute the usage of partially hydrogenated fat since FDA has demanded
all the manufacturers to remove the trans fat from the partially hydrogenated fat.
However, the consumers are concerned about deforestation of tropical forests due
to high demand of palm oil products. Therefore, in order to ensure that the palm
oil production is sustainable without jeopardizing the environment or society,
the palm oil producers can apply Roundtable on Sustainable Palm Oil (RSPO) certification
that ensures palm oil production is truly sustainable.
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| Figure 9: Roundtable on Sustainable Palm Oil (RSPO) logo https://www.ran.org/wp-content/uploads/rainforestactionnetwork/pages/2134/attachments/original/1402949376/rspo_logo.jpg |
Partially hydrogenated fat has adverse effects towards human health particularly cardiovascular disease. It has to be replaced with other alternatives to reduce trans-fat intake. Fat modifications such as fractionation and interesterification have indeed solved the problems of trans-fat as well as maintaining the functional properties of trans-fat in the food application in bakery and shortening. However, the most practical way to avoid the intake of trans fat is to reduce the intake of bakery products, fried foods and other processed food.
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