H. P. Dupuy

Effect of ascorbyl palmitate on the quality of frying fats for deep frying operations

The addition of 0.02% ascorbyl palmitate (AP) reduced color development of frying fat (animal fat/vegetable oil [A-V] shortening) and vegetable oil (partially hydrogenated soybean [V-S] oil) in simulation studies. It also reduced peroxide values, development of conjugated diene hydroperoxides (CDHP) and their subsequent degradation to volatile compounds, such as decanal and 2,-4 decadienal, indicating that AP has the ability to inhibit thermal oxidation/degradation of frying fats and oils. A commercial french fry fat had lower CDHP values compared to A-V fat in simulated studies, and fried chicken oil had lower CDHP values than the V-S oil. Peanut oil had higher thermal stability than the other fats and oils.

Identification of lipoxygenase-linoleate decomposition products by direct gas chromatography-mass spectrometry

Lipoxygenase, prepared from Virginia-type peanuts, was used to catalyze the oxidation of linoleic acid and methyl linoleate to form the C−9 and C−13 hydroperoxides. These reactions were monitored by rapid unconventional direct gas chromatography-mass spectroscopy. An aliquot of the enzymatic reaction mixture, without prior extraction or chemical modification, was secured directly into the heated (40–70 C) or nonheated (room temperature) injection system. When the reaction mixture was analyzed at room temperature, only hexanal was found. At elevated temperatures, five major and several minor components were identified. The predominant compounds identified were pentane, hexanal, 2-pentylfuran,trans-2,cis-4-decadienal, andtrans-2,trans-4-decadienal. These products originate from decomposition of either the C−9 or C−13 hydroperoxides generated by peanut lipoxygenase.

Direct sampling capillary gas chromatography of volatiles in vegetable oils

Direct sampling gas chromatography used for determining volatiles and, indirectly, the flavor of vegetable oils, has been improved by a capillary column in place of the usual packed columns. Data on two good vegetable oils from a supermarket, and on one of these samples after intentional deterioration, are presented. Use of the capillary column provides a more efficient technique to differentiate between the better oils than did the previously used packed columns.

Storage Quality of Brown Rice as Affected by Packaging with and without Carbon Dioxide

Shelled brown rice (100 g/bag) was packed in regular plastic bags in air, in laminated film (nylon-EVA) bags in air, and in laminated bags plus CO2. Samples of each were stored in the dark at 4 C and at 24 C, and samples were removed after 1, 3, 5 and 7 months for analysis of odor changes, free fatty acids, total microbial counts, total lipolytic fungi and bacteria, lipid peroxides and gas chromatographic volatiles profiles. Brown rice in laminated bags plus CO2 was more stable under refrigerated conditions than at ambient temperatures. However, at 24-C storage there was no consistent significant decrease in free fatty acids, lipid peroxides and volatile compounds in these bags compared to the other types of packing. Laminated bags seem to have had an adverse effect on total microbial populations at both 4 and 24 C. Selection of either type of package for brown rice would be governed by end use, storage time and conditions.

Analysis for trace amounts of geosmin in water and fish

Trace amounts of geosmin (trans-1,10-dimethyl-trans-9-decalol) were concentrated from relatively large volumes of water by vegetable oil extraction. After stirring the two phases for 30 min, the dispersed oil was allowed to separate. The oily layer was removed and centrifuged to break the emulsion and separate the two layers. The direct gas chromatographic technique was used to resolve the geosmin from other volatile components on a capillary gas chromatographic column. Volatiles were separated from the oil by securing an aliquot of the oil layer on volatile-free glass wool in the glass liner of the special gas chromatography inlet system. Geosmin was detected at the parts ber billion level with this simple and rapid technique. A technique also was developed for detecting geosmin in fish tissue; it involves steaming the fish to break up the tissue, centrifuging the residual oil phase, and detecting geosmin by capillary gas chromatography. The geosmin remains in the residual oil.

A simplified gas chromatographic procedure for analysis of lipoxygenase reaction products

A simple and very sensitive technique was devised to analyze lipoxygenase reaction products by direct gas chromatography. Results showed that peanut lipoxygenase oxidizes linoleic acid at the C-13 position exclusively.

Analysis of trace volatiles in food and beverage products involving removal at a mild temperature under vacuum

Abstract A simple approach for the detection and identification of volatiles in food and beverage products involving removal at mild temperatures under vacuum is presented. Volatiles are stripped from the sample between 30 and 60°C and adsorbed onto a Tenax-GC trap at 8 psi. The GC oven is cooled to −30°C for several minutes. Then the moisture-free volatiles are desorbed directly onto the cold capillary GC column and resolution is accomplished by temperature programming. This approach minimizes thermal decomposition and permits the detection and identification of trace volatiles in foods and beverages down to the parts-per-billion level by GC-MS.