ENHANCEMENT OF BIOACTIVE

PROPERTIES OF FRUITS, HERBS

AND SPICES AFTER PROCESSING

Associate Professor Eric Chan Wei Chiang

About myself

Full-blooded

Monash alumni

Still a young

researcher

Enjoy making

friends

Previous Monash Science

Symposium

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