| dc.description.abstract | Thernost important processed potato products in Kenya are French fries (chips), followed by
crisps and frozen French fries (chips). The demands for these products have increased over
the years and therefore require that more effort is made to develop varieties with appropriate
qualities for the rapidly developing Industry. Ten advanced potato clones developed by the
national breeding programme in collaboration with the International Potato Centre (CIP) and
eight established varieties were evaluated for frozen French fry quality. The clones were
coded 393385.47, 393385.39, 393380.57, 393380.58, 385524.9, 399746.2, 392657.8,
392617.54, 391691.96 and 392637.10. The potato varieties were Tigoni, Roslin Tana,
Desiree, Kerr's Pink, Dutch Robyjn, Kenya Karibu, Kenya Sifa and Asante. Tubers were
harvested at full maturity and cured under ambient air conditions for three weeks before
evaluation The tubers selected from a preliminary trial were harvested at maturity and
·subjected to further treatments and analysis after. Each cultivar was divided into three
whereby one third was processed immediately after curing, a third was stored for 12 weeks at
prevailing air conditions (15-19 °C/86-92 % rh) in a dark naturally ventilated store, and the
other third was stored for 3 months in cold store (4°C) before evaluation. Parameters
evaluated include; physical and chemical characteristics for raw tubers processed fresh and
frozen fries, and sensory quality characteristics for the fries.
Fries for the study were prepared by frying 12 mm X 12 mm potato sticks in vegetable oil at
170°C for 2 min (par-fries) and finish fryied at 170°C for 5 min. Blanched, partly fried or fully
fried fries were frozen stored at -18 °C in a laboratory chest freezer one month in a preliminary
evaluation trial and up to three months to test French fry quality of selected cultivars.
Proximate and mineral compositions of raw tubers and fries were evaluated using AOAC
methods.
Based on the preliminary trial, all the varieties and advanced clones except Asante, Kerr's
Pink and 393380.57 were found to be suitable for processing into freshly prepared fries.
Frozen French fries from all the varieties except Asante and clones 393380.57, 393380.58,
385524.9, 399746.2, 392657.8, 392617.54 and 392637.10 were acceptable following one
month of freeze storage at -18°C. Eight cultivars were selected thereafter for further
evaluation including five varieties (Tigoni, Desiree, Dutch Robyjn, Kenya Karibu, and Kenya
Sifa) and three advanced clones (393385.47,391696.96 and 393385.39).
Results indicated that all the 8 cultivars had acceptable physical tuber characteristics with
acceptable levels of dry matter content (~ 20 %) and specific gravity (~ 1.070). Reducing
sugar content differed significantly (P:S;0.05) with variety and storage condition. In freshly
harevested tubers, reducing sugar levels ranged from 0.15 % to 0.37 %. No significant
change (P>0.05) was found in the reducing sugar content when tubers were stored at ambient
air conditions (15-19 °C/86-92 % rh) for 12 weeks. In cold storage (4 °C195 % rh), tubers of all
the varieties and advanced clones accumulated high amounts of reducing sugars and none
was suitable for processing even after reconditioning for 3 weeks at ~15 °C.
Ambient air storage had no significant (P>0.05) effect on proximate composition. Frying did
not significantly (P>0.05) reduce any chemical constituent while freezing fries significantly
(P:S;0.05) reduced total ash, crude protein and total carbohydrate contents. The retention levels
were, however, substantial. Fat content increased on finish frying due to absorption of oil. The
'finish frying method' influenced significantly (P:S;O.05) the fat content in the fries, being higher
in deep fat frying and lower in oven-fried samples.
Ambient air storage had no significant (P>O.05) effect on any of the sensory attributes
evaluated. Freezing significantly (P:S;O.05) reduced flavour and texture scores of the tubers
while the rest of attributes like colour, oiliness and overall acceptability were not affected.
Frozen French fries made from the selected cultivars were acceptable even after 3 months of
frozen storage at -18°C.
The study established that five varieties (Tigoni, Desiree, Dutch Robyjn, Kenya Karibu, and
Kenya Sifa) and three advanced clones (393385.47, 391696.96 and 393385.39) were the
most suitable for processing into freshly prepared and frozen French fries. | en |
