3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
P17 ExTENSION OF ASPARAGINASE
APPLICATION TO ACRyLAMIDE
MINIMIZATION FROM POTATO TO CEREAL
PRODuCTS
ZUZAnA CIESAROVáa , KRISTínA KUKUROVáa ,
ALEnA BEDnáRIKOVáa and FRAnCISCO J.
MORALESb aVÚP Food Research Institute, Priemyselná 4, 824 75 Bratislava,
Slovak Republic,
bCSIC Consejo Superior De Investigaciones Cientificas, Instituto
Del Frio, José Antonio Novais 10, E-28040 Madrid, Spain,
ciesarova@vup.sk
Introduction
Acrylamide is a suspected human carcinogen, formed in
fried and baked carbohydrate-rich foodstuffs such as potatoes
and cereals. The free amino acid asparagine and reducing
sugars are considered as the main precurosrs 1 .
A number of raw material pre-treatments were
investigated which could mitigate acrylamide formation. Unfortunately,
most of them may also have an impact on the
product sensory quality. For example, the acidification may
result in a sour product taste, the addition of amino acids
may generate unpleasant off-flavours upon heating or in the
case of calcium chloride addition, product texture might be
improved, but on the other hand it causes a bitter aftertaste 2 .
However, the application of L-asparaginase enzyme before
heat treatment results in a sufficient decrease of acrylamide
amount with no undesirable impact on sensory quality of
final products 3 .
The aim of this work was an extension of enzymatic way
of acrylamide elimination in potato products 3 to cereal of rosquillas
type in collaboration with CSIC Institute del Frio in
Spain. In addition, the impact on the sensory quality of products
prepared with L-asparaginase was evaluated.
Experimental
L-asparaginase (novozymes, Denmark) produced by
Aspergillus oryzae was applied in simulated potato and cereal
matrices and food products on potato and cereal base such as
potato pancakes and typical Spanish cereal product named
rosquillas (Spanish doughnuts), respectively. Following ana-
lytical parameters were determined:
•
•
•
Saccharides using HPLC/RI according to ref. 4
Amino acids using LC/MS/MS according to ref. 5
Acrylamide using LC/MS/MS according to ref. 6
The content of main acrylamide precursors (monosaccharides
and amino acid asparagine) were analysed in raw
material. The conversion of asparagine to aspartic acid and
final acrylamide content after heat treatment was observed.
In potato pancakes the preliminary sensory evaluation
was done using a dual method. An appearance, colour, texture
and selected descriptors of taste and aroma were deter-
s610
mined using 0–5 point scale. Five trained assessors payed an
extraordinary attention to offlavour detection.
P o t a t o M a t r i x
Before the enzyme application in food products, the
appropriate conditions of L-asparaginase incubation (time
and temperature) were tested in simulated matrices. Potato
matrix consisted of the main acrylamide precursors (asparagine
and glucose), potato starch and water in typical proportions:
asparagine and glucose were used in equimolar ratio and
content of water was 80 %. Potato starch was dried before
the application to matrix in the ratio of 1 : 0.2 with mixture of
asparagine and glucose.
C e r e a l M a t r i x
Cereal matrix simulated Spanish cereal products recipe
for rosquillas preparation and was composed of asparagine,
glucose, fructose, wheat starch and water. Glucose and fructose
were used in equimolar ratio and in 1 : 4 ratio with starch
in a final mixture. Potency of 3 levels of asparagine (0.1, 0.5
and 1.0 %) were compared. Content of water in cereal matrix
was 50 %.
A s p a r a g i n a s e A p p l i c a t i o n
L-asparaginase was applied in concentrations of 2 and
10 U g –1 to simulated potato matrix or 0.1, 0.5 and 1.0 U g –1
to simulated cereal matrix. The enzyme was incubated at 20,
37, 50, 60 and 70 °C for 5, 10, 20, 30 and 60 min in thermostat
(Fried Electric, Haifa, Israel). Subsequently L-asparaginase
was applied to different potato varieties (Marabel and Bellarosa)
purchased from local Slovak market in concentrations
of 1 and 2 U g –1 , respectively, to potato pancakes (potatocereal
food product) in concentration of 1 U g –1 , and to cereal
product rosquillas in concentrations of 100 and 500 U kg –1 of
flour. L-asparaginase in food samples was incubated at 37 °C
for 10 and 15 min, respectively.
T h e r m a l T r e a t m e n t
For potato matrix 0.2 g of glucose and asparagine
mixture, 1 g of potato starch was weighed into the vial and
4 ml of water (control sample) or 4 ml of enzyme solution
with required concetration was added and in next step, after
enzyme incubation, treated at 180 °C for 20 min in thermoblock
(Liebisch Labortechnik, Bielefeld, Germany).
For cereal matrix 0.24 g of glucose and fructose mixture
and 0.76 g of wheat starch was weighed into the vial, 0.76 ml
of asparagine solution (concentration of 0.1, 0.5 and 1.0 g in
per 100 ml) in control sample or 0.38 ml of asparagine solution
(concentration 0.2, 1.0 and 2.0 g per 100 ml) and 0.38 ml
of enzyme solution with demanded concentration was added.
Vials were incubated and heated at 190 °C for 15 min in thermoblock.
Then, samples were cooled to room temperature and
final content of acrylamide was determined.