Abstract SCHIRACK, ANDRIANA VAIS. The Effect of Microwave ...

Composition of Peanuts
The structure of a peanut seed consists of two cotyledons and a germ, which
is enveloped in a thin skin called the testa. The peanut heart contains bitter material
and as a result is often removed during processing, while the testa is removed
during blanching. The testa contains mainly protein, fiber and carbohydrates, as
well as tannins which give the skin a bitter flavor (Hoffpauir, 1953).
Within each year, the composition and quality of the peanut crop changes due
to climatic variations as well as different harvesting and handling techniques (Pattee
et al., 1990). Peanut seeds consist of approximately 50% fat and 30% protein
(Hoffpauir, 1953). The main fatty acids found in peanuts include palmitic, oleic, and
linoleic acids. Up to 6% of peanut oil consists of long chain saturated fatty acids
such as arachidic acid (20:0), behenic acid (22:0), lignoceric acid (24:0), oleic acid
(18:1), and linoleic acid --18:2 (Chung et al., 1993). A large percentage of peanut oil
consists of polyunsaturated fatty acids, which are a substrate for oxidation by
lipoxygenase (Ory et al., 1992, St. Angelo, 1996). Ahmed and Young (1982)
indicated that the oleic/linoleic acid ratios in the peanut varied with cultivar, growing
location, maturity, as well as temperatures during the last few weeks of harvest.
This oleic/linoleic acid ratio has been positively correlated to oil stability.
The protein in peanuts includes albumins, and two globulins, arachin and
conarachin. The total protein has a high digestibility coefficient and has significant
amounts of 10 essential amino acids (Hoffpauir, 1953). The specific amino acid
content of peanuts varies depending on the type of peanut, cultivar, location, and
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