The vitamin E content showed strong association with
tocopherol isomers (Table 4). The Pearson correlation
coefficients of R-, â-, and ç-tocopherols and R-tocotrienols
ranged from 0.854 to 0.978 for vitamin E equivalents.
The tocopherol isomers were significantly correlated
with each other (r values between 0.898 and 0.992)
(Table 4). The analysis also showed that peroxide value
was negatively associated with tocopherols, but significantly
(P < 0.05) only with R-tocotrienol and â-tocopherol.
Anisidine and triene values were positively
correlated with R-tocotrienol (r ) 0.826 and 0.924,
respectively). The triene value was also positively
associated with â-tocopherol and vitamin E equivalents.
The high positive correlation of peroxide value with oil
yield from grapeseed and negative association with
tocopherols suggest that oil stability may be reduced
with increased oil extraction.
The data presented indicate that microwave conditioning
of grapeseed produces changes in the quality of
its oil. Some positive effects, such as decrease in
chlorophyll level and increase in R-tocopherol and R- and
ç-tocotrienols, were observed as a result of microwave
treatments. The elevated tocotrienol concentration of
the oil from the microwave-treated seeds provides an
added benefit for its use as a nutraceutical because
tocotrienols have been reported to have positive biological
and health effects (Watkins et al., 1998). Microwavedrying
of grapeseed is rapid and with proper controls
can be used to produce good-quality oil that may have
applications in the foods and growing phytoceutical
industries.