ENHANCEMENT OF BIOACTIVE
PROPERTIES OF FRUITS, HERBS
AND SPICES AFTER PROCESSING
Associate Professor Eric Chan Wei Chiang
Things I hope to address in
this talk
Convince you that raw food does not
mean good food
My own research journey
Some thoughts about the future
Raw foods
There is a whole movement propagating
the virtues of raw foods and it is the
subject of multiple books
Benefits include better retention of
nutrients and phytochemicals
Heat is widely perceived to degrade
nutrients and phytochemicals – until
today some still hold this as gospel
Phytochemicals
Phytochemicals are plant secondary
metabolite that confer health benefits
The most widely studied group of
phytochemicals are the polyphenols
A few notable examples include resveratrol
from grapes that prevent heart disease and
xanthones, potent antioxidants from
mangosteen and mangoes
Effects of heat
Heat decreases the stability of
phytochemicals but may not affect the
overall bioactive properties.
Some phytochemicals are more stable
than others even within the same group
e.g. flavonoids
They occur in a matrix and may be
protected from thermal degradation
Effects of heat
Heat may release additional phenolic
compounds
Heat inactivates polyphenol oxidase an
enzyme present in many plants which
oxidizes phenols
Polyphenol oxidase converts green tea in
to black tea but it also reduces its
antioxidant capacity
My research journey
It is very important to ask good research
questions
During my undergraduate honours
research I asked:
Would it be ok to just dry leaves in the
microwave?
Would heat degrade the antioxidants?
I moved on to other bioactive properties
but these questions drove my research
for a good period of time.
Microwave-drying enhanced
the AOP of T. laurifolia leaves
with 34% increase in TPC
and 67% increase in AEAC
as confirmed by the half-leaf
test.
A likely cause for the
increase in antioxidant
activity following microwave-
drying was was the release
of bound phenolic
compounds, brought about
by the breakdown of cellular
constituents
Another possible explanation
is the rapid inactivation of
polyphenol oxidase (PPO)
activity in samples due to
microwave irradiation
Thunbergia laurifolia
Morus alba
Leaves of M. alba responded positively to Microwave-drying, Oven-
drying and Freeze-drying.
The increase in antioxidant properties is likely due to the release of
bound phenolic compounds.
Furthermore, the oxidative enzymes in M. alba was not activated by
oven drying as observed in T. laurifolia.
Freeze-drying enhanced the
AOP of leaves of E. elatior
The antioxidants within the
leaves were not heat stable
The HPLC chromatogram of
freeze-dried leaves of E.
elatior showed greater
amounts of minor compounds
than fresh leaves
Etligera elatior
Overlay of chromatograms
showed greater amounts of
minor compounds in freeze-
dried than fresh leaves.
Spices: Antioxidant
Clove and cardamom
showed an increase in total
phenolic content and
radical scavenging after
thermal treatment
Phenolics were leached by
water used by boiling and
blanching to different
degrees in different herbs
Heat treatment releases
bound phenolics but is
offset by thermal
degradation and leaching
Spices: Anti-tyrosinase
Cinnamon and cumin had the highest tyrosinase
inhibition with potential to be applied in skin-
whitening
In most cases, heating does not affect tyrosinase
inhibition
Tyrosinase inhibition often attributed to phenolic
compounds but the type of phenols is more
important than quantity
Spices: Anti-tyrosinase
Cinnamon and cumin had the highest tyrosinase
inhibition with potential to be applied in skin-
whitening
In most cases, heating does not affect tyrosinase
inhibition
Tyrosinase inhibition often attributed to phenolic
compounds but the type of phenols is more
important than quantity
Spices: Antibacteria
Clove showed broad-spectrum antibacterial activity
against all six bacteria
Cooking had a variable effect on antibacterial activity
Interestingly, cinnamon only inhibited Gram-negative E.
coli after cooking
Fruits
Reviewed the effects of drying on the
bioactive properties properties of fruits
for a chapter in a book
Fruits are often eaten raw so it is very
interesting to see how drying affects its
properties
True enough, a review of literature
showed that heating and drying had
variable effects but it is also possible to
observe enhancement
Elderberries
Kruger et al. 2015 reported additional
DPPH radical scavengers being released
by elderberries after drying
Thoughts about the future
It is getting harder to get research grants but
more and more journals are adopting the pay to
publish model even prestigious ones by Elsevier
and Nature Publishing
Research has evolved as follows
2000: Journals went online
2005: Impact factor becomes important
2010: Impact factor segregated into quartiles
2015: Pay to win
What would 2020 bring? Would journals be
obsolete rendering impact factor meaningless?
Would Donald Trump bring about the end of
civilization?
Thoughts about the future
It is impossible to tell what the future
may bring
Research niches may dry up
Therefore it is important to keep asking
good research questions even if it means
venturing into the unknown
Venturing into the unknown
Moving out of your niche can be very rewarding
Winning the Top 5 in Elsevier's Green Chemistry
Challenge allowed me to bring my students to
Berlin
Thank youSlides and publications can be downloaded here:
www.slideshare.net/ChanEWC
https://www.researchgate.net/profile/Eric_Chan14