Chemistry Reference
In-Depth Information
(a) Industrial process
(b) Lab set-up
Control and sorting
Abrasive peeling
Hand peeling
Slicing
Slicing
Wash/rinse in cold water
Wash/rinse in cold water
Optional blanching,
80-85°C, 1-3 min
Blanching, 1 min, 85°C
Enzyme treatment, 15 min, 40°C
Frying, 2.5-4 min, 175-190°C
Frying, 2.5 min, 180°C
Seasoning
Acrylamide analysis
Packaging
(a) Industrial production of sliced potato chips.
85
Fig. 4.12
(b) The set-up used for lab-scale production
of sliced potato chips.
Asparaginase treatment of sliced potato chips was tested on both un-blanched and blanched
potato slices by introducing an extra processing step just before frying, as shown in Fig. 4.12.
Holding (15 min) the blanched slices in water without enzyme gave an acrylamide level of
1686 ppb, which was reduced to 659 ppb when asparaginase was included in the bath. If
the slices were not blanched prior to the enzyme treatment, no reduction in acrylamide
was observed (water, 3500 ppb acrylamide; enzyme treatment, 3752 ppb acrylamide). The
effect of a blanching treatment followed by a soak in water was thus significant compared
to just a soak in water, resulting in 1686 ppb versus 3500 ppb acrylamide, corresponding
to a 52% reduction. Similar results have been reported in several other studies.
38, 39
As was
observed for French fries, adding an asparaginase to the water increased the reducing effect
significantly, achieving a maximum of 81% reduction (659 ppb vs. 3500 ppb acrylamide) in
this experiment. The negative results obtained from treating the un-blanched slices confirm
that some kind of pretreatment for opening the cell wall or cell membrane structure is required
to release asparagine into the surrounding liquid hereby facilitating contact with the enzyme.
4.4.2.6
Limitations on asparaginase performance
To further investigate the rate-limiting step in the treatment of potato slices, a test was run
with increased enzyme dosage and prolonged treatment time. From a production point of
view, a long treatment time of up to 3 h is not an option since the final product completely
changes its characteristics and can no longer be considered a chip. However, as a means of
studying the system and defining the rate-limiting step, such tests can be valuable. Results
are shown in Fig. 4.13. The control sample was blanched and thereafter fried directly, while
all other samples were given a treatment in water or enzyme solution for 10 or 180 min after
blanching and before frying. The effect of the longer holding time is obvious, especially
for the enzyme-treated samples, where acrylamide levels as low as 30 ppb were reached.
Very little effect was seen of increasing the enzyme dosage five times for neither the 10
nor the 180 min samples, showing that reaction time more than enzyme dosage is a limiting
factor. This further indicates that the system is probably diffusion limited and controlled by
