Fatty Acid Composition and Iodine Values of Seeds of Oil and Fat Crops in Relation Climatic Conditions

Abstract

A review of the literature was carried out to evaluate the relationship between the climatic conditions and the composition of fatty acids and iodine values of the seeds of 35 species of oil and fat crops growing in the tropical, subtoropical and temperate regions.
1. Oil and fat crops which belong to 35 species described in the book “Oils and Oilseeds” by V. J. Godin and D. C. Spensley were studied. These include herbs and woody plants distributed in the tropical, subtropical and temperate regions.
2. Data reported were interpreted as follows :
1) Thirteen woody plants distributed in the tropics, such as palms, cocoa, illipe and shea nut, have a very high percentage of saturated fatty acids and vegetable fat or non-drying oil. Their predominant fatty acids are lauric acid, palmitic acid, stearic acid and oleic acid, and iodine values vary depending on the environmental conditions and the kinds of crops, averaging less than 110.
2) Subtropical woody crops, such as olive seeds have nearly the same fatty acid composition and iodine values as kapok, a tropical woody crop. Grape seeds which grow in the subtropical and temperate regions have almost the same fatty acid composition and iodine values as sunflower, a subtropical and temperate annual crop.
3) Warm-season herbaceous crops such as rice, groundnut and cotton which are distributed in the tropics, subtropics and temperate regions have a relatively high percentage of saturated fatty acids and non-drying or semi-drying oils. Their predominant fatty acids are oleic acid or linoleic acid, and iodine values are low or intermediate, ranging between 100 and 120.
4) The other warm-season crops adapted to rather cool temperature, such as soybean and maize, have a low percentage of saturated fatty acids (less than 15%) as well as of semi-drying or drying oil. Their predominant fatty acid is linoleic acid and their iodine values are rather high, between 120-150.
5) Cool-season herbaceous crops such as linseed flax, perilla, poppy and safflower which grow mostly in temperate regions and which can withstand severe winter have a very low percentage of saturated fatty acids, and drying oil. Their predominant fatty acids are linoleic acid or linolenic acid, and iodine values are among the highest (more than 150), as compared with those of other crops.
6) Sunflower and hemp, crops adapted to intermediate temperature conditions, show iodine values intermediate between those of warmseason and cool-season crops, namely 130 to 150. Linoleic acid is the predominant fatty acid along with drying oil.
7) The analysis of the data reported suggests that crops growing under high temperature conditions have a higher percentage of saturated fatty acids such as palmitic acid and stearic acid and consequently lower iodine values than crops growing under low temperature conditions in which fatty acids predominantly found are oleic acid, linoleic and linolenic acid. However, oiticica, tung, castor oil plant, crambe and rape seeds are an exception. They are composed of a large amount of fatty acids with a complicated structure such as licanic acid, eleostearic acid, ricinoleic acid, and erucic acid, respectively.
8) Woody plants and herbs in the tropics differed greatly in their percentage of saturated fatty acids, predominant fatty acids and iodine values, suggesting that woody or herbaceous characteristics represent an important factor for predicting fatty acid composition together with the distribution of the crop in relation to the climatic conditions.
It also appears that the adaptation of plants from tropical regions to temperate and the presence of herbaceous characteristics instead of woody ones are accompanied by a modification in the composition of fatty acids which become less saturated while the carbon number of predominant fatty acids increases from 14 or 16 to 18.