Effect of Baking Methods on the Fatty Acid Composition of Potatoes

Abstract

Fatty acid analysis Only minor differences in overall relative fatty acid composition were noted among four varieties of potatoes baked by microwave and conventional methods. However, the relative percent total unsaturated fatty acids were consistently lower in the microwave products as compared to conventionally baked potatoes regardless of variety. In addition, the relative percent rrans fatty acids was 2.5-4 times higher in the microwave process compared to the same varieties baked conventiohally.Since the potato is relatively low in lipid material which is present in a greater amount in the skin portion as compared to the interior tuber, entire potatoes were extracted. Approximately 600g (three potatoes) of cooked potatoes were immediately diced into 1L of boiling 80% methanol and refluxed for 10 min. This procedure was used to inactivate lipolytic enzymes that could alter fatty acid composition. It is acknowledged that this process probably resulted in the formation of methyl esters of the free fatty acid present. However, the goal was to methylate all lipid material present and this was accomplished as described below. Preliminary tests had indicated that the use of three potatoes from each lot was sufficient since relatively small standard deviations in relative fatty acid composition were noted. Upon cooling, redistilled diethyl ether was added and the mixture refluxed for 3 hr. The ether layer was separated and evaporated to dryness under a stream of nitrogen. The resulting lipid residue was methylated using commercially available boron trifluoride in methanol and the methylated product subjected to gas chromatographic analysis. Samples of raw potatoes of each variety were treated in the same manner.

Microwave and Conventional Heating Effects on Some Physical and Chemical Parameters of Edible Fats

“…Contradictory results have been reported on the possible isomerization (formation of trans) in the double bonds of fatty acids as a consequence of exposure to microwave energy (Maga et al, 1977;Mai et al, 1980), and in no study have data appeared relating to the positional isomers.…”

Formation ofTransFats: During Food Preparation

“…During stir-frying the oil was heated at an elevated temperature for a short time. In baking and stir-frying the fat was protected by water present in the prepared food, which lowers the temperature to a maximum of 100 o C. Maga et al (16) observed similar and insignificant changes in trans fat formation during the baking of potatoes. The activation energy for PUFA isomerization decreases when the number of cis double bonds increases (2,20); hence the linolenic acid trans isomers dominate in trans fat.…”

“…Thermo-oxidative degradation of lipids during food preparation at elevated temperatures has been studied extensively (12)(13)(14)(15); however, data are limited on the effect of these cooking methods on the formation of trans fats (15,16). Currently, baked goods are the main dietary source of trans fats, and reformulation of baking fats with liquid oils containing higher amounts of PUFA has the potential to increase trans fat formation during baking (15,17).…”

Isolation and Identification of Non-Conjugated Linoleic Acid from Processed Panax ginseng Using LC-MS/MS and 1H-NMR

“…Although the unknown HPLC peak eluting almost at the end of the solvent gradient in an ordinary HPLC separation can be confused with PPD, which is the most non-polar ginsenoside, we successfully showed that it is not a ginsenoside but rather linoleic acid by using analytical techniques such as LC-MS/MS and NMR. In addition, free fatty acids are known to usually increase in processed foods such as baked potato [30] and cooked pork [31]; thus, the hydrothermal degradation of lipids seems responsible for the increased free fatty acid content of black ginseng products.…”