Deodorizing, oils

Table 4. Viscosity of Deodorized Oils and Fats at Different Temperatures ...

Doktor Also spelled Doctor. A process for deodorizing oils by converting trace mercaptans to disulfides by the use of alkaline sodium plumbite and sulfur. The reactions are ... 

Deodorized oils, viscosity of, 10 821t Deoxidized copper, 7 751 Deoxidizers alkaline, 16 223 ferrosilicon as, 22 516 silicon as, 22 515... 

Refined, bleached, and deodorized oils may contain some nutritionally objectionable compounds - secondary oxidation products, di- and tri-enoic... 

OSI results range from 4 hr at 110°C for refined, bleached, deodorized oil, to 80 hr at 110°C for high-stability frying oil (Stauffer, 1996). Because the OSI can be determined at various temperatures, the temperature of the test should always be specified when reporting OSI results. 

The saponifiable portion of the fatty oil accounts for about 90% of the total fixed oil and is characterized by a very high content of octadecenoic acids. Petroselinic and oleic acid occur at similar levels and jointly comprise 74-85%, linoleic 7-16% and palmitic 4-8%, of the constituent fatty acids. During prolonged storage of the spice, the free fatty acid content gradually increases and this is a good indicator of the age of the material. The contents of fatty acids, sterols and total tocopherols in a deodorized oil derived from coriander seeds (yield up to 28%) are compared with those in sunflower oil and tests on the biological effects of coriander oil are reported by Mironova et al. (1991). Of the fatty acids present, total C18 1 acids (petroselinic acid + oleinic acids) constituted 80—82% and petroselinic acid alone 50—60%, and the food value was lower than that of sunflower oif. Kim et al. (1996) found the production of petroselinic acid from cell suspension cultures of C. Sativum. 

Iodometry on peroxidized olive oils gives the peroxide value (PV), which is expressed as the milliequivalent of active oxygen in the peroxides present in 1 kg of olive oil. Experienced oil analysts can relate PV values with rancidity and oil stability. Typical reports are that a fresh genuine oil has a PV of 2-5, a fresh deodorized oil a PV near to zero and that PV values of 10 or more are for oils prone to produce off-flavour volatiles. 

Trans fatty acids in refined and deodorized oils... 

About 0.01 percent of citric acid is commonly added to deodorized oils to inactivate trace-metal contaminants such as soluble iron or copper compounds that would otherwise promote oxidation and the development of rancidity. 

Winterizing is not practiced so widely in hot countries and its application is restricted mainly to sunflower, maize, cotton, ohve, ricebran, and partially hydrogenated soybean oils. The feedstock of the winterizing plant is usually bleached oil, sometimes neutralized or deodorized oil. The winterizing process is conducted in four steps ... 

A typical chemical composition of crude, refined, and deodorized canola oils is presented in Table 12. The deodorized oil data represents the oil quality used as a food ingredient. 

The values for the crude oil compare closely with those of other commercial oils, such as soybean oil, when produced according to good extraction practices. Chlorophylls and sulfur compounds levels are higher in canola oil compared with most other commodity oils. The deodorized oil data reflect good refining practice and are similar to the data obtained with other deodorized commodity oils processed for food applications. 

Dewaxing Canola oil is a natural salad oil. This means that it remains clear and liquid at refrigerator temperatures. It is used without winterization to produce bottled oil and salad dressings. However, the oil may contain a small and variable concentration of compounds (about 20-400 ppm), which may over time appear as sediment in the deodorized oil. This appears to be dependent on seed growing conditions. For the sake of simplicity, the term "waxes" is applied to these compounds, but it is known (99) that about 20-40% of these compounds are not wax esters. The crystallization behavior of the mix of compounds that can crystallize from canola oil is unpredictable in that low concentrations (<50 mg/kg) can sometimes show up in the oil as a sediment and that the sedimentation can occasionally occur in a few days, or take several months. 

Abbreviations nr—not reported TAG—triacylglycerols FFA—free fatty acids St —phytosterol fatty acyl esters St—free phytosterols FPE—phytosterol ferulate esters tocols-tocopherols and tocotrienols GL—glycolipids PL—phospholipids RBD—refined, bleached, and deodorized oil. 

Crude Oil Conditioning—Crude oils with high levels of phosphatides and trace metals are usually treated with food-grade phosphoric acid for 4 to 8 hours before refining. The purpose of the acid pretreatment is to (1) help precipitate phosphatidic materials (2) precipitate natural calcium and magnesium as insoluble phosphate salts (3) inactivate trace metals, such as iron, copper, and others that may be present in the oil (4) reduce the neutral oil losses and (5) improve the color and flavor stability of the finished deodorized oil. 

Deodorization Process Control. Deodorization is the last processing step, in which flavor, odor, and many of the stability qualities of an edible fat and oil product can be controlled. To produce quality deodorized products, attention must be focused on all of the factors involved with the process. The deodorization physical process removes the volatile, odoriferous materials present in the oils. The other factors that influence the quality of the deodorized oil products are as follows (106) ... 

Cold filtration may be performed before or after deodorization. Oil from the bleacher or the deodorizer is cooled to 12-15°C, and after settling for 12 hours, it is cold-filtrated with the addition of filter aid (perlite or diatoma) to prevent clogging caused by the wax. 

Trace metals are present in crude vegetable oils at parts per million (ppm) levels. Researchers have shown that soybean oil flavor can deteriorate from autoxidation, even at an iron content as low as 0.3 ppm (26) in the deodorized oil. Metal initiators initiate autoxidation in all vegetable oils and animal fats. 

Deodorized oil must be cooled, saturated with nitrogen, and stored in nitrogen-blanketed tanks (59). The storage tanks can be made of carbon steel. It is not necessary to have stainless steel tanks for freshly deodorized oil with a low free fatty acid content as shown in Table 3. The following guidelines are recommended... 

The best results are obtained when the deodorized oil is cooled to the above recommended temperatures, saturated with nitrogen as it leaves the deodorizer, and stored in nitrogen-blanketed tanks. The headspace in the storage tank should have maximum oxygen content of 0.5% (see Figure 4). 

Unloading and storage of the oil is equally critical at the snack food company. Care must be taken not to overheat any solidified hydrogenated oil. The oil must be saturated with nitrogen and stored under nitrogen as described for the deodorized oil. 

Peroxide value is the most widely used method (AOCS methods Cd S-53 and Cd 8b-90) to determine the quality of the oil. The primary oxidation products of oils and fats are the hydroperoxides. They can be quantitatively measured by determining the amount of iodine liberated by their reaction with potassium iodide. The peroxide content is expressed in terms of milliequivalents of iodine per kilogram of fat. However, when these hydroperoxides start breaking down to produce off-flavor compounds, correlation to the quality and stability of the oil will no longer be valid. Freshly deodorized oil should have zero peroxide value. In most cases, for the product to have acceptable storage stability, the peroxide value of oils used should be less than 1.0 meq/kg fat at the point of use. 

---