ABSTRACT: The effects of microwave roasting on phospholipids
in soybeans were investigated in relation to moisture.
Whole soybeans at different moistures (9.6, 38.2, and 51.9%)
were roasted by exposure to microwaves at a frequency of
2,450 MHz. During microwave treatments, the lower the moisture
content, the higher was the internal temperature in soybeans
at the end of microwave roasting. Total lipids were extracted
from the beans after microwave treatment, and the phospholipids
were separated with thin-layer chromatography.
Phosphatidylcholine was the principal phospholipid in the extracted
lipids from all unroasted and roasted bean samples. After
microwave roasting, phospholipids containing an amino group,
especially phosphatidylethanolamine, decreased substantially
(P < 0.05) in lower-moisture soybeans. However, increasing the
moisture content depressed a rise in the internal temperature of
soybeans and prevented a reduction in phospholipids and/or
polyunsaturated fatty acids in the phospholipids. Based on the
changes in the composition and fatty acid distribution of phospholipids
in soybeans during microwave roasting, it is necessary
to consider the moisture content in soybeans when roasting
in a microwave oven.
JAOCS 74, 117–124 (1997).
KEY WORDS: Fatty acid distributions