208 Produce Degradation: Reaction Pathways and their Prevention
Zhang et al. (2004) reported a comparison of an application of HPLC of antho-
cyanins before and after sample hydrolysis for determination of anthocyanins and
anthocyanidins in bilberry extracts. In the direct analysis approach bilberry extract
powder was dispersed in a 1:1 water/methanol solution containing 2% HCl. This
solution was found to give the best extraction yields. After passing through a 0.45-μm
PTFE filter, samples were injected into HPLC. The identification was conducted
using HPLC coupled with DAD and a mass spectrometer. A UV-vis detector found
over 15 peaks and MS identified 9. In the hydrolysis approach, samples were
dispersed and filtered as in direct analysis, placed in a dry bath, and hydrolyzed at
100°C for 30 min, 1 h, and 2 h. After hydrolysis, samples were cooled immediately
to room temperature and analyzed by HPLC. After 30 min of hydrolysis most of
anthocyanins were converted to anthocyanidins, with approximately 10% remaining.
After 1 and 2 h all anthocyanin peaks almost completely disappeared. Five major
peaks were identified as delphinidin, cyanidin, petunidin, peonidin, and malvinidin.
The authors concluded that the analysis of unhydrolyzed samples provides an antho-
cyanin profile useful for characterization of raw materials, whereas the acid hydrol-
ysis approach allows quantification of individual anthocyanidins in botanical
extracts.
Parejo et al. (2004) used HPLC equipped with DAD coupled to negative elec-
trospray ionization (ESI) tandem mass spectrometry (MS/MS) to analyze an extract
from dried fennel residue after steam distillation of essential oils. Forty-two phenolic
compounds were identified, including 27 not previously reported in fennel. Among
newly identified compounds were hydoxycinnamic acid derivatives, flavonoid gly-
cosides, and flavonoid aglycons.
Anthocyanins are valuable compounds of pigmented orange juices. An econom-
ically feasible method of removing these compounds from citrus by-products may
lead to their recovery and utilization in food and pharmaceutical industries. Scordino
et al. (2004) studied equilibrium and kinetic data of adsorption of cyanidin-3-
glucoside chloride on 13 commercial resins. The presence of hesperidin, which is
a dominant flavanone in orange fruit, had to be considered. The experimental equi-
librium data fitted well into Langmuir and Freundlich isotherms. It was demonstrated
that the resin EXA-118 was most effective to obtain a highly concentrated extract
of anthocyanins from pigmented orange juice.
7.4.5 OCCURRENCE AND ANTIOXIDANT PROPERTIES
OF FLAVONOIDSThe increased interest in the flavonoids and phenolic acids other than anthocyanins
in fruits and vegetables comes from convincing epidemiological and other studies
that show health-promoting and disease-preventing effects of these compounds
(Rice-Evans and Parker, 1998).
Marin et al. (2004) investigated antioxidant constituents of sweet pepper (Cap-
sicum annum L.) at four maturity stages (immature green, green, immature red, and
red). The study included phenolics (hydroxycinnamic acids and flavonoids), vitamin
C (ascorbic acid and dehydroascorbic acid), and carotenoids. Utilization of modern
analytical techniques allowed the separation and identification of a significant number