Agriculture Reference
In-Depth Information
15
Postharvest Storage and
Physiology
Paul C. Bethke*
USDA Agricultural Research Service and University
of Wisconsin Department of Horticulture, Madison, USA
Potato storage is an important component of the
potato production system in many parts of the
world. This chapter begins by describing briefly
the purpose and value of potato storage, and
some of the many options available for storing
the crop.
Physiological defects that develop in storage
are described, including pressure bruise, cold-
induced sweetening, sugar-end defect, and stem-
end chip defect. The central importance of the
reducing sugars, glucose and fructose, to tuber
processing quality is introduced in the context of
physiological defects that cause dark-colored
fried products. The general features of carbohy-
drate metabolism in stored potato tubers are de-
scribed, with details provided for the subcellular
formation and utilization of starch, sucrose, glu-
cose, and fructose. These biochemical details are
the foundation for understanding the section on
the sugar management of potatoes in storage.
Tuber respiration is discussed, with an
emphasis on how storage duration and tempera-
ture impact respiration rates. The effects of res-
piration on crop value and potato storage
management are illustrated. The mechanism of
tuber water loss is described, and the relative
importance of water loss through the periderm,
lenticels, wounds, and sprouts is considered.
Sprout control is essential to maintain crop value,
and as such, options for residue-free, organic,
and synthetic sprout control are presented. Finally,
guidelines for the storage of potatoes in bulk bins
are provided, in order to give a general under-
standing of how potatoes in large, ventilated
storage facilities are managed.
15.1 The Purpose of Potato
Storage
Potato storage makes the crop available for con-
sumption or sale over an extended period of
time. Insulated storage structures protect the
crop from freezing in regions where postharvest
temperatures fall below 0°C. In regions where a
warm or wet period follows harvest, ventilated
storage structures protect the crop from disease
by keeping water off the tubers. In regions where
most potatoes are harvested during a short
period of time, prices tend to be low immediately
after harvest, due to an abundant supply. Stor-
age allows the potatoes to be sold when supplies
are reduced and prices are higher. Where tubers are
used for processing, local storage allows for tubers
to be available for many months. Local availabil-
ity minimizes shipping costs and reduces idle
time at processing plants. In situations where
storage conditions can be controlled precisely,
a well-designed storage facility can facilitate the
