DETECTION OF ENZYMATIC BROUNING IN FRUIT

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2783 (1982). .8 (1984). ... any previous treatment ( 7 ) . Houever ... 2 s h o u s an e n z y m a t i c b r o u n i n g k i n e t i c a t 2b "C or. an appiè ... the d i f f e r e n c e b e t u e e n t h e 280 nm and 260 nm v a l u e (D.O.D) and ... time considered.
DETECTION

OF

ENZYMATIC

M.C.Nicoli'

BROUNING

I N FRUIT

C.R.Lerici''

R.Massini'

PRODUCTS

and

D . Mas t r o c o i a-'

'

I s t i t u t o d i Tecnologie A1iroentari-University v i a M a r a n g o n i 97 33100 Udine Italy

'

Dipartimento d i Protezione e Valorizzazione Agro-AiIraentare University of Bologna v i a S.Giacomo 7 «H>

Fig. 2. E n z y m a t i c b r o u n i n g k i n e t i c f o l l o u e d b y t h e e v a l u a t i o n o f t h e d i f f e r e n c e b e t u e e n t h e 2 8 0 nm a n d 2 6 0 nm v a l u e ( D . O . D ) a n d t h e m e a s u r e m e n t a t 4 2 0 nm. For f i r s t

the order

Kinetic

range

of

time

considered

both

tuo pararoeters

shou

a

kinetic. rate

constants

are reported

i n table

1.

TA3LE 1 Constant rates of enzymatic brouning r e l a t i v e l y t o s p e c t r o p h o t o m e t r i c m e a s u r e m e n t s a t 4 2 0 nm

t o DOU

index

and

Index

Constant rate k (hours"' )

C o e f f i c i e n t of determination

DOD

0.127

0.9b6

0.035

0.834

420

nm

Froro DOD

i s

observation a more

traditional

of the kinetic

sensitive

index

spectrophotometric

rate

constants

of enzymatic measurement

66

i t appears

brouning

a t 420

nm.

than

that the

ot: a n

appiè

jhotomecric

Heating influence studied.

appiè

of

Flg.Ja

the

ultraviolet

for

a

shou at

blanched as

non

2 8 0 nm

puree

non

and f i g . 3 b region and

a t I i 5 'C

brouning report

depending

f o r d i f t e r e n t tiraes t h e

on

DOù

the variation on

tittie

to first

brouning Maillard

causes

an

reaction

paramet^r

uaa

i n absorbance i n

of heating

e n z y m a t i c a l l y brouned

enzymatic

due

samples

enzymatic

respectlvely

puree.

Ihese

increase

of

fiqures

absorbance

products C l l ) .

I.i. no

tréated

1 Hour 2 Hour8

I.I

u

•luation of C D . 0 . D) a n d

< H

^ters

shou

a » _ IM

9M WAVELENGHT

; index

and F i g . 3a. Changes o f s p e c t r a l b e h a v i o r o f a b l a n c h e d s u b j e c t e d t o one a n d t u o h o u r s t r e a t m e n t s a t 115

.cient of ination

appears ng

than

that the

67

pure* "C.

sample

ili*



«1»

*u



WAVELENGHT F i g . 3b. puree In the

both

broun

causes

Changes o f s p e c t r a l sample s u b j e c t e d t o

a

cases color

higher

DOD but

b e h a v i o r o f an d i f f e r e n t beat

increases i n the

according

blanched

amount

of

reaction

6

C

C

enaymatica1ly trcatroents at uith

puree

products

the

the

brouned IISOC.

increasinq

heat

absorbing

of

treatment at

280

nm.

.1.^

• 5

1*

li

li

il

C « L « I