Physical Properties
Lovibond color is a common method to check the color of oils and fats; in this method, the Lovibond color spectrophotometer is used. The major parts of a Lovibond color spectrophotometer are a series of red, yellow and blue glass standards, in which the color measurement is performed through the color control of samples with these glass color indicators (18).
Lovibond color parameters of shortenings in the Iranian market can be seen in Table 2. The Lovibond red and yellow colors of the samples were 2.1-13.6 and 28-70.4, respectively, and no blue color was found in the samples. As shown in Table 2, the Lovibond color range of the shortenings is rather wide; some samples are more colored, while others are less colored, which is due to the wide range of applications for shortenings in various food products. In fact, the type of usage of shortenings (the product that receives the shortenings) and the buyer’s demand determine the Lovibond color. The yellow/red origin in the samples is the natural or added carotenoids. Processes like bleaching and deodorizing lead to thermal removal of carotenoids. Therefore, in order to compensate for the yellow/red color reduction and manufacture a product with proper and standard color features, beta-carotene is usually added to the deodorized fat (19).
Melting point is one of the most important physical properties for quality control and producing fat products. Factors such as non-saturation, carbon chain length, isomeric forms (cis andtrans ), fatty acids and their position in the glycerol backbone, and tempering time and conditions affect the melting point of fats. SMP, which determines the beginning of melting range, is the most common one (20). In general, the shortenings should be solid at room temperature. Also, in order to prevent waxy mouthfeel, the melting point should be as close as possible to the body temperature (37 °C) (21).
In Table 3, the SMP of shortenings are shown. The SMP of Iranian shortenings was in the range of 42.5-49.3 °C (45.53 °C on average). The INSO has not specified a certain limit for SMP of shortenings.
Kheiri (17) reported the SMP of 10 shortenings found in the markets of Australia, Egypt, Netherlands, Kuwait, Malaysia, New Zealand, Turkey, United Arab Emirates, Japan, and United States of America as 35.8, 40.0, 37.0, 35.5, 42.0, 41.0, 38.9, 34.9, 34.0, and 43.0 °C, respectively. Karabulut and Turan (13) studied the physicochemical properties of the 10 shortening and 15 margarine samples in the Turkish market. The SMP of Turkish shortenings and margarines was in the range of 33-43 °C and 31.2-34.9 °C, respectively. They also reported that the SMP of all the shortenings was higher than that of margarines. The relatively high melting point is a desirable feature because shortening should not quickly melt at the high temperature of the oven and should lead to the stability of air cells and, as a result, a bigger product. In general, it can be concluded that the SMP of Iranian shortenings in most cases is higher than that of the foreign samples, which is quite reasonable with regard to the lower IV and higher saturation of Iranian shortenings than the foreign ones.
SFC represents the fat crystals within fats at various temperatures. It is one of the most important physical properties of fats, which directly affects many of their features such as the general appearance, ease of packaging, spreadability, consistency, textural, rheological and sensory properties (6, 22). This feature is not specified in INSO and there is no precise standard for it in Iran. The SFC of shortenings in the Iranian market at 10, 20, 30, 35 and 40°C is shown in Table 3. Accordingly, the SFC of Iranian shortenings at 10, 20, 30, 35 and 40°C was 40.6-75 %, 24.2-59.5 %, 11.4-36.4 %, 7.8-27.3 %, and 3.1-17.4 %, respectively.
Kheiri (23) reported the SFC of 10 shortenings in the markets of Australia, Egypt, Netherlands, Kuwait, Malaysia, New Zealand, Turkey, United Arab Emirates, Japan, and United States of America at 10, 20, 30, 35, and 40 °C as 27.1-44.3 %, 16.6-34.1 %, 9.7-23 %, 5.1-13.3 %, and 0.0-9.6 %, respectively.
Karabulut and Turan (13) reported that the SFC of shortenings in the Turkish market at 10, 20, 25, 30, 35 and 40°C was 37.9-55.6 %, 22.4-43.5 %, 14.9-38.4 %, 8.3-29.4 %, 3.3-18.3 %, and 0.0-8.0 %, respectively. According to the references, it can be concluded that the SFC of most Iranian shortenings is more than that of the majority of foreign samples (particularly at 10 and 20 °C), which may be due to the lower IV and, consequently, the higher saturation value in Iranian shortenings (Tables 1 and 3).
The SFC curve is an indicator for evaluating the rigidity and plasticity of fats at different temperatures, from the refrigerator to the body temperature. The SFC curve can be used to determine the specific uses of fats. For example, the shortening for frying should have a steep SFC curve, while the shortening of layered pastries should have a flat SFC curve (18, 24).
In Fig. 1, the SFC curve of Iranian shortenings is compared with the typical SFC curve of various types of plastic fats (from the published scientific sources). As seen in Table 1, the SFC curves of most Iranian shortenings are higher than the common SFC curves of margarines and shortenings. As discussed earlier, the reason is the higher saturation of these samples than the foreign samples. Another important point is the sharper slope of SFC curve of Iranian shortenings than the common SFC curves of various margarines and shortenings. Based on Fig. 1, the SFC curve of shortenings 6, 11, 13, and 15 is more similar to the typical SFC curve of margarines and shortenings.