30A-27 |
Microwave-assisted fatty acid analysis of oil recovered from catfish processing wastes containing high moisture content |
S. SATHIVEL1, W. Prinyawiwatkul1, C. C. Grimm2, and J. M. King1. (1) Department of Food Science, Louisiana State University Agricultural Center, Baton Rouge, LA 70803-4200, (2) USDA-ARS-SRRC, New Orleans, LA 70124 Lipid extraction with solvents (e.g., chloroform, methanol) is a common step of fatty acid (FA) profile analysis. High-moisture content may interfere with lipid extraction, thus drying may be required before FA-methylester (FAME) is prepared. When a sample is microwave-heated, moisture in the tissues creates localized superheating, causing rapid release of moisture, expulsion of fat/oil from fat cells, and partial release of oil to the surface. It may be possible to prepare FAME from microwave-heated samples without solvent extraction. This study investigated efficiency of FA analysis of microwave-heated samples without solvent extraction and determined heating power(%)/time(sec) for maximal FA recovery. Catfish liver with 75%moisture was used for demonstration. Liver was collected, ground, and microwave-heated. Microwave-heated samples were methylated with methanolic-NaOH and BF3-methanol, and analyzed with GC. Heating conditions were: 100, 80, 60 or 40%power at 1000 Watts-2450 MHz, each for 80, 60, 40, or 20 sec. Three replications, each with 3 extractions, were conducted. The traditional FA analysis with chloroform-methanol-water extraction was used as the control. Microwave-heating at 60-100%power for 80sec removed over 50%water. FA profiles of microwave-heated samples differed (a=0.05). Principal component analysis separated 3 samples (control and two samples microwave-heated at 100%power-80sec and 80%power-80sec) from other 14 samples. Discriminant analysis identified C20:4/C16:0/C20:0 (the first dimension--59% variance explained) and C20:1/C18:0/C18:2/C16:1/C22:6 (the second dimension--cumulative 88% variance explained) as discriminating fatty acids. Recovery of C20:4, C16:0, and C20:0 of all microwave-heated samples was lower than that of the control, while higher recovery was observed for C20:1, C18:0, C18:2, C16:1, and C22:6 at 80-100%power for 60-80 sec or 60% power-80 sec. Heating at 100%power-80 sec yielded the highest recovery of DHA (C22:6w-3) and arachidonic (C20:4w-6). Microwave-assisted FA analysis offers a faster and efficient approach to determine FA acid profiles for high-moisture containing samples, generating less chemical wastes and requiring less labor.
Session 30A, Food Chemistry: Lipids
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