The purpose of this study was to evaluate frying
oil quality with different assessment methods during vacuum
frying of carrot slices. In six consecutive days, palm oil, lard, and
soybean oil were fried under vacuum at 105°C for 20 min each
hour in an 8-h shift. Peroxide value, acid value, carbonyl value,
total polar components, dielectric constant (Food Oil Sensor
reading), viscosity, and fatty acid composition were used to
evaluate the quality of these oils. Results showed that palm oil
and lard possess greater thermal stability than soybean oil. The
decrease in C18:2/C16:0 ratio was greater for soybean oil than the
other two oils. Of the assessment methods used, peroxide value,
carbonyl value, total polar components, and dielectric constant
all showed good correlation with frying time and between each
other. Viscosity was suitable to assess vacuum-fried lard and
soybean oil, but not palm oil. The measurement of dielectric
constant, on the other hand, appeared to be unsuitable to assess
vacuum-fried soybean oil.