Post-Frying Oil Drainage from Potato Chips and French
Fries: A Comparative Study of Atmospheric and Vacuum
Drainage
Azmil Haizam Ahmad Tarmizi & Keshavan Niranjan
Received: 6 July 2011 / Accepted: 1 September 2011 / Published online: 14 September 2011
# Springer Science+Business Media, LLC 2011
Abstract This paper represents a study of the transient
changes occurring in temperature, and moisture and oil
contents during the so called “post-frying drainage”—
which is the duration for which a product is held in the
head space of the fryer after it is removed from the oil.
Since most of the oil adhering to the product penetrates into
the structure during this period, this paper examines the
effects of applying vacuum during drainage (1.33 kPa) to
maintain the product temperature consistently above the
water saturation temperature corresponding to the prevailing
pressure (11 °C), which potentially eliminates water
condensation and prevents the occluded surface oil from
penetrating into the product structure. Draining under
vacuum significantly lowers the oil content of potato chips
by 38% compared to atmospheric drainage. This phenomenon
can be further confirmed by confocal laser scanning
microscopy (CLSM) images, which show that the boundary
between the core and the crust regions is clearly visible in
the case of vacuum drainage, whereas in the case of
atmospheric drainage, the oil is distributed throughout the
structure. Unfortunately, the same approach did not reduce
the oil content of French fries—the oil content of vacuumdrained
product was found similar to the product obtained
by draining under atmospheric pressure. This is because the
reduction in oil content only occurs when there is net
moisture evaporation from the product and the evaporation
rate is sufficient to force out the oil from the product; this
was clearly not the case with French fries. The CLSM
images show that the oil distribution in the products drained
under atmospheric pressure and vacuum was similar.
Keywords Post-frying drainage .Vacuum drainage .
Atmospheric drainage . Oil content . Confocal laser
scanning microscopy (CLSM)
Introduction