BoRa Yi

Oxidative Stability of Solid Fats Containing Ethylcellulose Determined Based on the Headspace Oxygen Content

Solid fat was developed by blending fully hydrogenated soybean oil, palm oil, and canola oil, and organogels were prepared using selected solid fats and ethylcellulose. The oxidative stability of organogel was tested at 100 and 180°C using a headspace oxygen assay. Addition of ethylcellulose produced a firmer organogel solid state in selected solid fats ranging from 15.8 to 24.6% saturation at room temperature. Addition of ethylcellulose generally decreased the oxidative stability of organogels prepared using canola oil. The oxidative stability of some organogels made using solid fats changed depending on the concentration of added ethylcellulose (10 or 15%, w/w), and the oxidation temperature. Development of an organogel with a relatively low saturation and a high oxidative stability suitable as a food ingredient is possible.

Effects of relative humidity on the antioxidant properties of α-tocopherol in stripped corn oil.

The effects of relative humidity (RH) on the antioxidant properties of α-tocopherol (10, 20, 42, and 84 ppm) were determined in stripped corn oil oxidised at 60°C. The degree of oxidation in oils was determined by analysing headspace oxygen content and conjugated dienoic acids (CDAs). Changes in moisture and α-tocopherol content were also monitored. The oxidative stability of stripped corn oil and stability of α-tocopherol differed significantly depending on the RH. As the concentration of α-tocopherol increased from 10 to 84 ppm, oxidative stability decreased significantly irrespective of RH. The remaining α-tocopherol content decreased as RH increased, suggesting an important role for moisture content in the stability of α-tocopherol. Antioxidant properties of α-tocopherol were greatly influenced by both moisture content in oil and α-tocopherol concentration.

Antioxidant properties of ascorbic acid in bulk oils at different relative humidity.

The effects of relative humidity (RH) on the antioxidant properties of ascorbic acid (10, 20, 42, and 84ppm) were investigated in stripped corn oils stored at 60°C. The degree of oxidation in oils was determined by analysing headspace oxygen content and conjugated dienoic acids. The oxidative stability of bulk oils without addition of ascorbic acid was significantly different depending on the RH. As the concentration of ascorbic acid increased from 10 to 84ppm, oxidative stability increased significantly irrespective of RH (p<0.05). Generally, oils containing ascorbic acid at low RH had higher oxidative stability after storage at 60°C than those at high RH. The antioxidant properties of ascorbic acid were greatly influenced by both the moisture content in the oil and the ascorbic acid concentration.

Effects of deuterium oxide on formation of volatiles in linoleic acid model systems at different temperatures and oxygen limitation conditions

Effects of 30, 60, and 90°C treatments and oxygen limitation on formation of volatiles were determined for linoleic acid model systems containing deuterium oxide (D2O) and deuterium free water. The presence of D2O accelerated consumption of headspace oxygen, indicating that the rate of lipid oxidation increased in the presence of D2O. The presence of deuterium in headspace volatiles was indirectly determined based on comparison of the amount of the fragmented mass to charge ratio (m/z) (molecular weight, Mw), which was 73.1/72.1 for d1-pentane/pentane and 125.1/124.1 for d1-2,4 octadienal/2,4 octadienal. The ratio of 73.1/72.1 (m/z) for pentane was significantly (p<0.05) higher for samples containing D2O than for samples containing deuterium free water at 30, 60, and 90°C. Other volatiles did not follow the same pattern. 2,4-Octadienal in samples under unlimited oxygen conditions confirmed this trend, indicating that water was incorporated into volatiles during oxidation of linoleic acid under these conditions.

Effects of emulsifier charges on the oxidative stability in oil-in-water emulsions under riboflavin photosensitization

The oxidative stability in oil-in-water (O/W) emulsions containing different emulsifier charges was tested under riboflavin photosensitization by analysis of headspace oxygen content and lipid hydroperoxides. Sodium dodecyl sulfate (SDS), Tween 20, and cetyltrimethylammonium bromide (CTAB) were selected as anionic, neutral, and cationic emulsifiers, respectively. The O/W emulsions containing CTAB had lower oxidative stability than those with SDS and Tween 20. The addition of ethylenediaminetetraacetic acid, a well-known metal chelator, increased the oxidative stability in O/W emulsions, irrespective of emulsifier charges. Oxidative stability in Tween 20-stabilized emulsions decreased in FeCl3 and FeCl2 concentration-dependent manner. However, oxidative stability in samples containing CTAB increased up to 0.5mM of FeCl3 and FeCl2 and then decreased, which implies that CTAB act differently during lipid oxidation compared to SDS and Tween 20.

Evaluation of In vitro antioxidant properties of roasted hulled barley (Hordeum vulgare L.)

The antioxidant properties of roasted hulled barley (Hordeum vulgare L.) were tested using in vitro assays, including the total phenolic content (TPC), total flavonoid content (TFC), and DPPH, ABTS, and ferric reducing antioxidant power (FRAP) assays. Hulled barley was roasted at 0, 170, 210, and 250°C for 20 min. The effects of the aqueous heating time at 100°C from 0 to 60 min and the blending ratio of barley and water from 1:2 to 1:5 in aqueous solutions were evaluated. p-Coumaric and ferulic acid contents were analyzed. The highest antioxidant activities were observed in 250°C roasted samples, although the p-coumaric and ferulic acid contents were high at 210°C. The highest antioxidant capacity in aqueous solution was observed at 60 min of extraction and in samples with a 1:2 blending ratio.

Riboflavin Photo-transformation of Genistein and Changes in Radical Scavenging Activities of Photo-transformed Genistein Derivatives

Genistein was treated with riboflavin photosensitization and the radical scavenging activities of mixtures of genistein and riboflavin were determined using DPPH and ABTS assays. For a period of light irradiation of 100 min, the initial concentration of genistein decreased by 79.1% for riboflavin photosensitization. New peaks were formed and the peak areas increased for a mixture of riboflavin photosensitized genistein. Genistein derivatives were tentatively identified as trihydroxy isoflavones or genisteins with an additional hydroxyl groups. The radical scavenging abilities of photo-sensitized genistein derivatives were significantly (p<0.05) increased, based on DPPH and ABTS results, compared to samples without visible light irradiation for 100 min of photosensitization. Riboflavin photo-transformation can enhance antioxidant activities in isoflavone aglycones.

Physicochemical properties and oxidative stability of oleogels made of carnauba wax with canola oil or beeswax with grapeseed oil

Two types of oleogels—made of carnauba wax with canola oil or beeswax with grapeseed oil—were prepared at concentrations from 0 to 15% (w/w) of wax. Physical characterization was done and oxidative stability of the oleogels were evaluated. As the proportion of wax increased from 5 to 15%, the enthalpy of crystallization and melting increased in both oleogels. The carnauba wax-based oleogel (CWO) required greater enthalpy than the beeswax-based oleogel (BWO). Differences in L*, a*, and b* values between control oils and the oleogels significantly decreased as the concentration of wax increased in the oleogels (5–15%; p<0.05). Oil-binding capacity of the BWO was higher than that of the CWO. Solid-fat content of the CWO did not change significantly from 10 to 60oC, whereas that of the BWO decreased. In general, oxidative stability of the CWO was better at 60 and 180oC heat treatment in comparison with control oils (p<0.05). However, the BWO did not provide high oxidative stability than the control oils.

Evaluation of Antioxidant or Prooxidant Properties of Selected Amino Acids Using In Vitro Assays and in Oil-in-Water Emulsions Under Riboflavin Sensitization

The antioxidant properties of selected amino acids were tested using in vitro assays and oil-in-water (O/W) emulsions under riboflavin (RF) photosensitization. Headspace oxygen content, lipid hydroperoxides, and conjugated dienes were determined for the degree of oxidation. Riboflavin photosensitization was adapted as the oxidation driving force. In vitro assays showed that cysteine had the highest antioxidant properties followed by tryptophan and tyrosine. However, in O/W emulsions under RF photosensitization, tyrosine inhibited lipid oxidation whereas tryptophan acted as a prooxidant. Tryptophan accelerated the rates of oxidation in O/W emulsion without RF. The antioxidant properties of amino acids differed depending on the antioxidant determination methods, oxidation driving forces, and food matrices.

Analysis of Trans Fat in Edible Oils with Cooking Process

Trans fat is a unsaturated fatty acid with trans configuration and separated double bonds. Analytical methods have been introduced to analyze trans fat content in foods including infrared (IR) spectroscopy, gas chromatography (GC), Fourier transform-infrared (FT-IR) spectroscopy, reverses-phase silver ion high performance liquid chromatography, and silver nitrate thin layer chromatography. Currently, FT-IR spectroscopy and GC are mostly used methods. Trans fat content in 6 vegetable oils were analyzed and processing effects including baking, stir-frying, pan-frying, and frying on the formation of trans fat in corn oil was evaluated by GC. Among tested vegetable oils, corn oil has 0.25 g trans fat/100 g, whereas other oils including rapeseed, soybean, olive, perilla, and sesame oils did not have detectable amount of trans fat content. Among cooking methods, stir-frying increased trans fat in corn oil whereas baking, pan-frying, and frying procedures did not make changes in trans fat content compared to untreated corn oils. However, the trans fat content was so low and food label can be declared as ‘0’ trans based on the regulation of Ministry of Food ad Drug Safety (MFDS) (< 2 g/100 g edible oil).