Field Guide of Discovery-based Exercises for - Aseanipm ...

Exercise No. 7.09 258
POST-HARVEST HANDLING AND PRIMARY PROCESSING
OF ORGANICALLY-GROWN VEGETABLES
BaCKGroUND aND raTIoNalE 259
During plant growth, roots absorb nutrients, moisture, and
carbon dioxide from atmosphere. The leaves then convert
these into structural components (e.g., cell walls, membranes,
and organelles) and food reserves. At harvest, plant parts we
388
Field Guide of Discovery-based Exercises for Organic Vegetable Production
when is this exercise most
appropriate?
ɶ In FFS, TOT, and VST
sessions, just before
harvesting and before
start of discussions on
‘Harvesting and Postharvest
Management in
Vegetables’.
are interested in are separated from the rest of the plant, hence, photosynthesis in these plant parts
essentially stops.
The harvested produce, therefore, has to depend on food and water reserves it has accumulated
during growth to maintain its physiological processes. Theoretically, once food and water reserves
declined appreciably, the usefulness of produce is greatly diminished, if not ended. As food and
water reserves are diminished, the produce’ susceptibility to microbial attack also increases, thus
resulting in decline of usability.
Food reserves decrease through degradation (breaking down) and by respiration, while water reserves
are lost by transpiration. Such decreases in food and water reserves are reflected as moisture loss
or shriveling, chemical changes (e.g., change in color, taste, aroma, contents of sugar and vitamins),
and textural modifications (e.g., softening, loss of crispiness, and toughening), and greater activity
of pathological organisms (e.g., rotting). Any factor that hastens these processes and encourages
microbial growth will hasten deterioration. The most important factors are as follows:
• Temperature. Low temperature slows down respiration, transpiration, and other processes
resulting in deterioration of any produce up to a certain extent. This is the basis for immediately
cooling a produce and then keeping it at a low temperature. Most tropical produce cannot,
however, withstand temperature lower than 12 °C. They show abnormalities like discoloration,
development of sunken areas (pitting), and failure to ripen. These are indications of physiological
disturbance within a cell. Most crops introduced from temperate zone, like strawberry and
cabbage, can tolerate temperature as low as 0 °C.
258 Adapted from Callo, Jr., D.P., L.B. Teofilo, and H.A. Tauli (eds). 2002. Field Guide of Discovery-based Exercises for Vegetable IPM, Volume II. SEAMEO
Regional Center for Graduate Study and Research in Agriculture (SEARCA), Los Baños, Laguna, Philippines. pp306-311.
259 Bautista, O.K. (ed). 1994. Introduction to Tropical Horticulture. 2 nd Edition. SEAMEO regional Center for Graduate Study and Research in Agriculture
and University of the Philippines Los Baños, College, Laguna, Philippines. pp435-438.