Agriculture Reference
In-Depth Information
Harvest the crop when skin set and chem-
ical maturity are appropriate for the desired
end use.
of pile temperature differential (delta T).
A  delta T of 0.6-0.8°C works well; for ex-
ample, 13°C tuber pulp temperature on the
bottom of the pile and 13.8°C on the top of
the pile for a 5.5 m high pile.
Harvest chip and fry processing tubers be-
fore crop is exposed to cold temperatures
that can lead to CIS.
Keep records for each storage bin: cultivar,
field, pulp temperature during loading, ex-
tent of skinning and bruising, and chem-
ical maturity of the crop. Improvements in
storage management accrue when past
successes and failures can be evaluated in
light of reliable records.
Minimize tuber skinning and damage during
harvest. Skinning and bruising facilitate
pathogen entry and can increase respiration
rate and tuber sugars.
Avoid bringing soil into the storage. Adher-
ing soil makes it more difficult to dry the
tubers in the short term and may prevent
uniform airflow in the long term.
Hold potatoes at approximately 13°C for
wound healing and preconditioning. Moni-
tor tuber sugars to assess progress in pre-
conditioning.
The ideal pulp temperature at harvest is
10- 16°C. Harvest operations should be
suspended when the pulp temperature of
tubers arriving at the potato storage is over
18°C. Warm temperatures increase the risk
of pathogenic spoilage of the crop.
Preconditioning of fry processing potatoes
requires 2-3 weeks, but can be longer. Glu-
cose should be 0.8 mg g - 1 FW or less at bud
end for good color in processing.
Observe all tubers moving into storage and
make note of potential storage issues such
as excessive shatter bruising, disease/rot,
and moisture.
Precondition chip stock so that sucrose is
~0.7 mg g - 1 FW and glucose is less than
0.035 mg g - 1 FW. This can take from several
weeks to 2- 3 months.
Pile tubers to a uniform depth of 5- 5.5 m.
Operate the bin piler such that tubers drop
no more than 6 inches when leaving the
conveyer. The top of the pile should be level,
which encourages uniform airflow through
the pile and greatly facilitates the detection
of wet spots and sunken areas later in the year.
For fresh market potatoes, allow wound
healing to proceed for at least 3 days at 10-
13°C, then ramp to final storage tempera-
ture at a rate of 0.25°C day - 1 .
Monitor atmospheric CO 2 in the potato stor-
age bin. Add fresh air when needed to keep
CO 2 below thresholds.
Avoid piling cool potatoes on top of warm
potatoes. The interface is a site where con-
densation is likely to occur, and this pro-
motes disease development.
Ramp chip and fry processing cultivars to
temperature set point at a rate of 0.1-
0.16°C day - 1 . Slow cooling can reduce the
potential for CIS.
Calibrated temperature probes should be
placed in tubers on the bottom and near the
top of the pile to monitor pulp temperatures.
General guidelines for temperature set
points are 7- 10°C for fry processing, 9- 10°C
for chips, 3- 5°C for fresh market, and 3°C
for seed.
Humidify to 95% RH. Reduce humidity
slightly if disease problems develop.
Ramping may take 6-8 weeks for process-
ing potatoes.
Cool to 14- 15.5°C as quickly as possible.
Initial air temperature settings should be
based on measured pulp temperatures. Set
to 0.8°C less than the pulp temperature
near the top of the pile.
Maintain pile temperature differential
(delta T) by adjusting fan speed or by using
intermittent ventilation.
Apply CIPC or other sprout inhibitor after
suberization is complete. A minimum of
3-4 weeks in storage is recommended; fol-
low label recommendations.
Remove field heat in about 3- 4 days using
cool air circulation.
Ramp temperature down to 13°C at 0.3-0.5°C
day - 1 or less to reduce evaporative loss and
refrigeration required.
Monitor sucrose for advance notice that
processing materials are likely to fry dark
because of responses to environment or
senescence sweetening.
Adjust airflow rate or duration to establish
a uniform pile temperature and top-to-bottom
 
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