Hong-Sik Hwang

Preparation of Margarines from Organogels of Sunflower Wax and Vegetable Oils

UNLABELLEDnIt was previously reported that sunflower wax (SW) had high potential as an organogelator for soybean oil-based margarine and spread products. In this study, 12 other vegetable oils were evaluated in a margarine formulation to test feasibility of utilization of SW as an alternative to solid fats in margarine and spread products containing these oils. The minimum quantity of SW required to form a gel with these oils ranged from 0.3% to 1.0% (wt.). Organogels were prepared from the vegetable oils with 3%, 5% and 7% SW and were tested for firmness as well as melting behaviors using differential scanning calorimetry. These organogels were also incorporated into a margarine formulation. All of the vegetable oil organogels produced relatively firm margarines. The margarines prepared from organogels containing 3% (wt.) SW had greater firmness than commercial spreads, whereas margarines made from 7% SW were softer than commercial stick margarines. However, dropping points of the margarine samples were higher than those of commercial spread and margarine products. Margarine firmness was modestly inversely correlated with the amount of polar compounds in the oils and did not correlate with fatty acid compositions. This study demonstrates the feasibility of using a number of healthy vegetable oils rich in polyunsaturated fatty acids to make healthy margarine and spread products by utilizing SW as an organogelator.nnnPRACTICAL APPLICATIONnThis study showed that sunflower wax could be used as an alternative to traditional solid fats for the development of new margarine and spread products from a variety of healthy vegetable oils.

Enhancing Antioxidant Activity of Sesamol at Frying Temperature by Addition of Additives through Reducing Volatility

Additives were evaluated to investigate their effects on volatility of sesamol at frying temperature with the hypothesis that the interaction between an additive and sesamol would reduce sesamol volatility. Twenty-two additive : sesamol combinations were examined by thermogravimetric analysis (TGA) under nitrogen in neat form and in soybean oil. The results indicate that these additives could bind to or interact with sesamol and consequently reduced its volatility. (1) H NMR study provided evidence for hydrogen bonding between sesamol and a hydroxyl group, an amino group, and ether groups. Subsequent heating tests were conducted to investigate the effect of the reduced volatility of sesamol on antioxidant activity in soybean oil at 180 °C. Oxidation of soybean oil was monitored with gel permeation chromatography for formation of polymerized triacylglycerols and with (1) H NMR for loss of olefinic and bisallylic protons. Sesamol retained in soybean oil during the heating process was determined by high-performance liquid chromatography. A strong correlation between the retained sesamol and the antioxidant activity was observed. The mixture of 830 ppm sesamol and mono-/diglycerides, polysorbate 20 or l-carnosine showed much improved antioxidant activity compared to sesamol itself and slightly better antioxidant activity than 200 ppm tert-butylhydroquinone. It is believed that this method can also be used for many other antioxidants for which volatility is a problem.

Utilization of Oleogels as a Replacement for Solid Fat in Aerated Baked Goods: Physicochemical, Rheological, and Tomographic Characterization

Canola oil-carnauba wax oleogels were evaluated as a replacement for shortening in a baked cake system. The use of oleogels produced cake batters with a lower pseudoplastic property and also contributed to their viscous nature. The shortening replacement with oleogels at up to 50% was effective in maintaining the ability to hold air cells into the cake batters. The volume of cakes had an overall tendency to decrease with increasing shortening replacement with oleogels, leading to increased cake firmness. The tomographic analysis demonstrated that the total porosity and fragmentation index were reduced in the oleogel cakes, showing a more connected solid structure. The levels of saturated fatty acids in the cakes containing oleogels were significantly reduced to 13.3%, compared to the control with shortening (74.2%). As a result, the use of oleogels for shortening up to 25% produced cakes with lower levels of saturated fatty acids without quality loss.

Conclusions and Future Prospects

There are a variety of analytical methods developed for the determination of lipid oxidation. However, many of them are old methods that depend on chemical reactions with a reagent, require long time and extensive labor, cannot be automated, measure only one kind of oxidation product, determine the concentration of an oxidation product that reaches a peak in a short time, and/or have inconsistencies due to multiple variations in the procedure. Modern analytical instruments, which can handle many samples at a time by automation, concomitantly detect many oxidation products, and be used for a long period of oxidation process, should be utilized to overcome the problems of current standard analytical methods. The NMR methods meet all these needs and should be more widely used for the analysis of lipids. More convenient, user-friendly NMR instruments such as small benchtop NMR instruments and software programs such as an automated analysis program for the fatty acid composition of vegetable oils have been developed.

31 P NMR Spectroscopy for Assessment of Lipid Oxidation

The NMR method has drawn great interest as a new method to assess the level of lipid oxidation since most of conventional analytical methods have some problems. The 1H NMR method monitoring the disappearance of starting materials was found to be very reliable for the assessment of lipid oxidation. In this chapter, the development of 1H NMR methods for the assessment of lipid oxidation during storage and frying will be discussed. Starting from the first method reported by Saito in 1987, a variety of 1H NMR methods developed by many research groups are introduced in this chapter. Early studies focused more on lipid oxidation at relatively lower temperatures such as storage temperatures or slightly higher temperatures for the acceleration of oxidation (25–70 °C) since the more oxidation products could be detected at a lower temperature. Later, it was found that there were significant differences between oxidation products and oxidation mechanisms with different oxidation temperatures. There are four different types of methods developed for the assessment of oxidation during frying: 1) Methods monitoring the changes of major NMR signals, 2) methods using the NMR proton relaxation time, 3) methods measuring acyl groups, and 4) methods measuring aldehydes and other oxidation product.

1 H NMR Spectroscopy for Identification of Oxidation Products and for Elucidation of Reaction Mechanisms

One of the most significant contributions of the 1H NMR technique is that it made major advances in elucidation of molecular structures of oxidation products. Since oxidation mechanisms and consequent oxidation products are different at different temperatures, this chapter is divided into two parts: 1) 1H NMR to indentify oxidation products during storage of oil and 2) 1H NMR to indentify oxidation products at frying temperatures. The study on oxidation products using 1H NMR was conducted as early as 1966 when Zimmerman utilized a very early model of the NMR instrument (60 MHz) to verify the isomerization of unsaturated hydroperoxide to a ketohydroxy compound. Since then, many oxidation products including hydroperoxides, aldehydes, ketones, alcohols, and epoxides were identified by the NMR method. One major difference between the oxidation products formed at relatively lower temperatures and at frying temperatures is that intermediate oxidation products such as hydroperoxides are not observed at frying temperatures because these intermediate oxidation products easily react with other compounds or decompose to produce secondary oxidation products. These intermediate products can be detected only when the oil was heated for a relatively short time at a frying temperature.

Application of NMR Spectroscopy for Foods and Lipids

Nuclear magnetic resonance (NMR) spectroscopy is one of the most powerful analytical tools to identify organic and bio-organic substances and to elucidate their chemical structures. Therefore, it has widely been used to analyze a variety of foods. Moisture content, solid fat content, fatty acid composition in lipid, free fatty acids, authenticity of edible oils, and the metabolic profile of sweet pepper can be analyzed by the NMR spectroscopy.

Conventional Analytical Methods to Assess Lipid Oxidation

Lipid oxidation is a major cause of the deterioration of quality in food. The accurate qualitative and quantitative assessment of lipid oxidation is important for quality assurance of food products. Lipid oxidation is a very complicated process involving numerous oxidation products. Therefore, numerous chemical and physical analytical methods have been developed to assess lipid oxidation. Despite tremendous efforts on understanding mechanisms of lipid oxidation, lipid oxidation is not completely understood, and it is almost impossible to accurately predict oxidation products under different oxidation conditions. Since there are many standard methods available, it is very important to use the right analytical method depending on the purpose of the analysis. In this chapter, most widely used conventional analytical methods to assess lipid oxidation and their problems and limitations are discussed.

Use of 13C NMR Spectroscopy for Determination of Lipid Oxidation

Although 13C NMR spectroscopy is not as frequently used as 1H NMR spectroscopy, it is a very powerful tool to elucidate the molecular structure of a compound, especially when it is used with 1H NMR spectroscopy. The chemical shifts of 13C NMR signals are quite characteristic for specific carbons. Other techniques involving 13C NMR such as two dimensional (2D) NMR techniques (e.g. 1H-13C heteronuclear single-quantum correlation spectroscopy (HSQC)), distortionless enhancement by polarization transfer (DEPT), and attached proton test (APT) are very useful tools to elucidate molecular structure of an organic compound. Therefore, the 13C NMR spectroscopy and related techniques have been used for analyses of foods and lipids. In many cases, 13C NMR is used along with 1H NMR since a 13C NMR spectrum is typically obtained from the same sample used for 1H NMR. Examples of the application of 13C NMR including distinguishing cis- and trans- isomers of a mono-unsaturated fatty acid, the determination of the fatty acid position in a triacylglycerol, simultaneous quantitative determinations of free fatty acids, contents of triacylglycerols and phospholipids, and fatty acid composition, the elucidation of the mechanism of lipid oxidation, the prediction of the stability of the non-polar portion of vegetable oil, and the detection of Diels-Alder products in oxidized oil are discussed in this chapter.