Chemical Properties
Table 1 presents the fatty acids composition of shortening samples. The
TFA content of the shortenings varied between 0.21 and 15.54 % (4.29 %
on average). Based on definition, fat products with less than 5 % and 2
% TFA are referred to as low-trans and trans -free
products, respectively (16). According to Table 1, only 13.33 % of the
samples (codes 5 and 11) were trans -free (containing less than 2
% TFA). Also, 66.67 % of the samples (codes 1, 2, 3, 6, 8, 9, 10, 13,
14 and 15) were low-trans (containing 2-5 % TFA), and 20.00 %
of the samples (codes 4, 7 and 12) contained more than 5 % TFA. The
major trans isomer of the shortening samples was elaidic acid
(Trans 18:1) with a mean content of 3.52 %.
Although applying more stringent regulations of maximum allowed amount
of TFA was partly successful, about 20 % of the shortenings found in
the Iranian market still contained TFA contents of above 5 %, which
could be the cause for concern. Unfortunately, there is no precise and
reliable information on TFA content found in Iranian shortenings in
previous years, but undoubtedly these series of changes in regulatory
policy reduces the TFA content in Iranian shortenings.
As can be seen in Table 1, the SFA content of the shortenings was
between 40.08 and 59.54 % (50.46 % on average). Palmitic acid was the
main saturated fatty acid in the samples (25.48-48.90 %, 35.46 % on
average). This finding indicates that the palm oil and/or its
derivatives (palm olein and stearin) are the main fat base stocks for
production of Iranian shortenings. Oleic and linoleic acids were the
dominant unsaturated fatty acids (with a range of 26.96-38.78 % and
6.49-21.73 %, respectively). There was also a small amount of linolenic
acid in Iranian shortenings (with a range of 0.11–1.83 %, 0.66 % on
average), which helped their high oxidative stability.
The regulatory policy on the amount of lauric acid has recently focused
on reducing the maximum level of this fatty acid in fat products due to
increasing health concerns. In this regard, the INSO has determined an
upper limit of 0.7 % for lauric acid in the last standard amendment of
shortening (10). According to Table 1, the main content of lauric acid
in Iranian shortenings was 0.26 %. However, the lauric acid content of
sample 1 and 2 was respectively 1.08 and 1.32 % which was more than the
standard limit.
Leth et al. (12) characterized the properties of all shortening brands
in the Danish market (39 brands) from 1995 to 1999. They observed a
gradual decrease in trans isomers in the Danish shortenings: the
content of TFA in this product was reduced from 10.4% in 1992 to 3.6%
in 1995 and Danish shortenings were almost free from transisomers in 1999. The SFA content of Danish shortenings was 29.9-42.8 %.
They also reported that palmitic acid was the dominant SFA of Danish
shortenings with a range of 24.1-28.0 %.
Karabulut and Turan (13) analyzed 10 shortenings in the Turkish market
from 2003 to 2004. According to their results, the TFA content of the
shortenings in Turkey was 2.0-16.5 % and SFA content was 36.3-43.1 %.
Also, palmitic acid with the range of 23.8-38.4 % was the predominant
SFA content in Turkish shortenings, approximately similar to the Iranian
case.
In general, by decreasing the maximum limit of TFA in fat products,
manufacturers have to increase the SFA content in fat formulations
because TFA play a significant role in consistency, plasticity, and
proper melting properties. Therefore, in order to compensate for this
flaw, the increase in SFA is inevitable in fat formulations (12).
The IV is one of the important parameters of oils and fats, indicating
their unsaturation level. There is a direct relationship between the IV
and nutrition value of fat products. The INSO specifies no limit for the
IV of shortenings. According to Table 1, the IV of Iranian shortenings
was between 40.84 and 73.32 (53.52 on average).
Kheiri (17) reported the IV of 10 shortenings in the markets of
Australia, Egypt, Netherlands, Japan, Kuwait, Malaysia, New Zealand,
Turkey, United Arab Emirates, and United States of America as 57.0,
71.8, 67.0, 60.7, 60.4, 49.1, 48.3, 95.5, 75.9, and 84.4, respectively.
Generally, it can be concluded that the IV of most Iranian shortenings
is less than that of the foreign samples. Therefore, Iranian shortenings
may be more saturated than the foreign ones (Table 1).
FFA content is among the most important quality parameters of oils and
fats at all the processing and storage stages. These compounds are
indicators for studying hydrolytic rancidity and are the secondary
products of oxidation. By increasing the FFA content in fat products,
the smoking point is reduced (18). According to INSO, the maximum FFA
limit (wt. % of palmitic acid) is 0.1 %. As can be seen in Table 2,
the FFA content of the shortenings was 0.02-0.92 %. In fact, 46.7 % of
the samples’ (samples 5, 6, 7, 8, 9, 11, and 12) FFA contents was above
the standard limit.
PV is an indicator of the initial oxidation products (hydrogen
peroxides). Although hydrogen peroxide has no odor, the secondary
products of oxidation such as aldehydes and ketones with the undesirable
odor (off-flavors) are produced due to the breakdown of these compounds.
The PV measurement is the most common quality test for oils and fats
(18).
The PV of Iranian shortenings can be seen in Table 2. The PV of the
Iranian shortening samples was 1.0-3.0 mEq/kg. According to the INSO,
the maximum limit of PV of shortenings should be 1, 2, and 5 mEq/kg at
the time of production, for import (at the time of importing goods), and
at the time of consumption, respectively. As shown in Table 2, all the
shortenings had the PV of less than 5 mEq/kg. In general, the samples
with higher TFA and SFA contents had a lower PV; since the increase in
the content of these fatty acids increases the oxidative stability of
fat products.
Oxidative stability of oils and fats is affected by the presence of
unsaturated fatty acids, oxygen content and storage conditions. The high
content of unsaturated fatty acids accelerates the decay, thereby
causing off-flavors, toxic compounds, loss of nutritional value, and
unusable fat products. The toxic compounds resulting from rancidity can
cause problems such as tumors, heart failure, cataract, and brain
dysfunction (18). The high oxidative stability is one of the most
important features of shortenings, which has a great impact on the
shelf-life duration of final products (1). According to INSO (10), the
IP110 of shortenings used in flour and confectionery
products should be at least 30 and 25 h. According to Table 2,
IP110 of the shortenings found in the Iranian market was
10.03-44.02 h. In fact, 53.3 % of shortenings (samples 1, 2, 3, 5, 7,
8, 11, and 13) had the IP110 below 25 h and was not in
the standard range. However, 46.7 % of the samples (samples 4, 6, 9,
10, 12, 14, and 15) had IP110 above 30 h, indicating the
high oxidative stability of these samples. Unfortunately, no information
can be found on the oxidative stability of shortenings in other
countries.