Page 337 - Natural Antioxidants, Applications in Foods of Animal Origin

316 Natural Antioxidants: Applications in Foods of Animal Origin
VetBooks.ir reduced risk of certain cancers such as lung cancer, colorectal cancer, breast

cancer, and prostate cancer (Ciska & Pathak, 2004; Higdon et al., 2007).
Brassica vegetables have been reported to contain high amount of DF and
various bioactive agents with high antioxidant activity. Phenolic compounds
and vitamin C are the major antioxidants of brassica vegetables (Podsedek,
2007). Lipid-soluble antioxidants (carotenoids and vitamin E) are respon-
sible for up to 20% of the brassica total antioxidant activity.
Cauliflower has a very high waste index (Kulkarni et al., 2001) and is
an excellent source of protein, cellulose, and hemicellulose (Wadhwa et al.,
2006). It is considered as a rich source of DF and possesses both antioxi-
dant and anticarcinogenic properties. The level of non-starch polysaccharide
(NPS) in the upper cauliflower stem remains similar to that of the floret and
both are rich in pectic polysaccharides, while the cauliflower lower stem
NPS is rich in cellulose and xylan (Femenia et al., 1998).
White cabbages (Brassica oleracea var. capitata) have been reported
to contain high amount of DF and bioactive agents with high antioxidant
activity as well as glucosinolates which are claimed to possess anticar-
cinogenic activity. About 40% of cabbage leaves, which are processed into
many products, including salads and ready-to-eat vegetables, are lost and
regarded as waste which contains high amount of DF and various phyto-
chemical compounds (Nilnakara et al., 2009). Processing of these residues
could therefore add much value to the products. The main constituents in
white cabbage are carbohydrates, comprising nearly 90% of the dry weight,
where approximately one-third is DF and two-thirds are low-molecular-
weight carbohydrates (Wennberg et al., 2004). Additionally, white cabbage
also possesses significant amounts of antioxidants such as ascorbic acid,
phenolic compounds, and tocopherols (Kim et al., 2004; Wennberg et al.,
2004; Singh et al., 2006).
The cabbage glucosinolates are the most interesting compounds. Gluco-
sinolates are a group of sulfur-containing plant secondary metabolites and
can be hydrolyzed by myrosinase to form different products, for example,
thiocyanates, isothiocyanates, epithionitrile, nitrile, and oxazolidine-thione
(Wennberg et al., 2006). The breakdown products (especially isothio-
cyanates) possess anticancer activity via modulation of phase II enzymes,
including glutathione S-transferase and quinine reductase. These enzymes
are reported to help inactivate cancer by blocking normal cells from DNA
damage (Verkerk et al., 2001). Production of DF powder from cabbage outer
leaves involves mechanical and thermal processes which may affect the
amount of glucosinolates. Several reports have indeed shown that glucosino-
lates in Brassica vegetables decreased upon blanching because of enzymatic