Introduction
Shortening is a kind of edible fat which used traditionally in
confectionery and bakery products. These fats are a homogeneous blend of
various oils and fats, which are produced to provide desirable
physicochemical and textural properties in flour and non-flour products.
Shortenings prevent gluten and starch particles from adhering to each
other and give the sensation of softness to the bakery products when
chewed. Shortenings impart important functional properties such as
tenderness and texture, aeration and stability, mouthfeel, heat
transfer, positively contributing to the structure and geometry of the
products and extended shelf-life. In bakery products, shortening
increases the volume of the dough by allowing the gluten to regain its
elasticity (1-3). Shortenings also help stabilize air cells produced
during mixing (4).
Various types of shortenings, such as all-purpose, fluid, cake, icing,
filler fat, bread, frying, pie crust, pastry, and dry shortenings are
available in the food industry (1). Shortenings can be manufactured with
or without emulsifiers (often mono- and diacylglycerols (2-4 % w/w)).
Emulsified shortenings are more suitable for where the incorporation of
air into the shortening system is desired (such as icings, cakes, etc.),
while un-emulsified shortenings are typically used for cookies, crackers
and frying (5). Final application of a shortening in the food industry
typically depends on its solid fat content (SFC) profiles and oxidative
stability. Such fats have to satisfy a host of nutritional, physical and
rheological functionality requirements. According to the specific
functionality requirements, the shortening ingredients are sometimes at
odds with each other. For example, harmful trans fatty acids
(TFA) are common ingredients required for good consistency and
spreadability, whilst healthy essential fatty acids do not always aid in
the consistency requirements (and should also be included in shortening
formulation). The physical and rheological properties of shortenings
depend on several factors including 1) type of fat base stocks and the
amount of emulsifier; 2) the SFC profile; 3) the production process
conditions (including temperature and mechanical agitation rate) (1).
Shortening production systems may, therefore, contain several steps such
as blending, fractionation, hydrogenation, interesterification and
tempering to obtain the desired crustal polymorph and melting
characteristics. The hydrogenation is still the main technique for
producing shortening in many parts of the world. Accordingly, this fat
product may contain relatively high amounts of TFA (1). High levels of
TFA in the diet can increase the risk of coronary heart diseases by
increasing the level of triacylglycerol and the ratio of low-density
lipoprotein (LDL) to high-density lipoprotein (HDL) cholesterol in blood
plasma. It is specified that a 2 % increase in energy intake in TFA was
led to 23 % increase in the risk of incidence of coronary heart
disease. With increasing evidence of the harmful effects of TFA on human
health such as an increased risk of cardiovascular disease and different
types of allergies and cancer, studies, as well as regulatory policies,
have focused on reducing the intake of TFA in diets (6, 7). In January
2006, the Food and Drug Administration of the United States of America
(FDA) required producers to list the amount of TFAs on the nutrition
facts label of conventional foods and some dietary supplements (8). Many
countries such as USA, Brazil and EU countries have limits on the amount
of industrialized TFAs in food products (9). In recent years, the
Iranian National Standards Organization (INSO) has reduced the upper
limit of TFA and saturated fatty acids (SFA) in food products. In this
regard, the INSO revised the standard of specification of shortening in
2015, and changed the upper limit of TFA from 10 to 5 % and SFA from no
limit to 65 % (10).
In recent years, many studies have been conducted to investigate the
characteristics of shortenings worldwide. However, middle eastern
products characteristics have not been well-studied, yet. The chemical
composition and physical properties of 12 French shortenings; 73 brands
of margarines and shortenings on the Danish market; and 10 Turkish
shortenings have been characterized by Bayard and Wolff (11), Leth et
al. (12) and Karabulut and Turan (13), respectively. Recently,
Macias-Rodriguez and Marangoni (2016) investigated the rheological
properties of nine commercial shortenings (including puff pastry,
roll-in, all-purpose, cake and icing shortenings) with similar
physicochemical characteristics but diverse functionality under small
and large oscillatory shear tests (14).
In order to have accurate information on the intake of trans fats
and to implement appropriate measures to reduce their intake, each
country should have an updated estimate of the per capita consumption of
TFA in the diet of its citizens. However, there is no report on the
amount of TFA in shortenings in Iran. Other physicochemical and melting
properties of this product are also not known.
In this study, the physicochemical characteristics (fatty acid
composition, iodine value (IV), Lovibond color, free fatty acids (FFA),
peroxide value (PV), oxidative stability index, slip melting point (SMP)
and SFC) of commercial shortenings marketed in Iran were characterized.
Hence, the present research can provide valuable information about
different types of Iranian shortening.