PHL can be quantitative (e.g., physical
weight losses) and qualitative (e.g.,
loss in edibility, nutritional quality,
caloric value, consumer acceptability,
etc.). Others refer instead to direct
and indirect losses. Direct losses are
related to the total or partial loss of
product resulting from spoilage caused
by mechanical, physical, physiological,
or biological damage; indirect losses
relate to qualitative loss. Others use
the term opportunity losses to refer to
losses resulting in lost sales or sales
only made in low-value markets due
to quality problems and other market
constrains (Box 2.1). External losses
are an additional category. These fall
on both the value-chain participants
and society as a whole—for example,
cases in which the chemical pesticides
used to protect grain impact
the environment or human health.
External losses can be diffi cult to estimate
in economic terms (see Lubulwa
et al. (1995) for an example of cassava
cyanide).
The following pages present a brief
characterization of the ways some of
the postharvest related functions are
performed in grain chains in SSA, highlighting
the different factors that can
infl uence postharvest losses along the
different chain stages.