Mechanical and Temperature Effects on Shelf Life Stability of Fruits and Vegetables - Food Shelf Life Stability: Chemical, Biochemical, and Microbiological Changes - page 38

Rough handling of fresh produce is a serious problem in the postharvest system.
The shelf life of agricultural produce may be shortened due to unfavorable handling
temperature and humidity, together with mechanical injury and infestation of pests
and diseases. Fruits and vegetables are highly susceptible to mechanical damage
during harvesting and handling. As such, this chapter will focus on fruits and
vegetables, discussing how postharvest handling affects shelf life and measures to
minimize the deteriorative effects of mechanical injury are given.
Fruits are commonly derived from an ovary and the surrounding parts, while
vegetables are derived from different plant parts. Vegetables can be grouped into three
categories, namely: (1) seeds and pods; (2) bulbs, roots, and tubers; and (3) flowers,
buds, stems, and leaves. 2 Examples of the different derivation of fruits and vegetables ;
from plant parts are: potato — swollen stem tuber; sweet potato — root tuber from
fibrous root; carrot — root tuber from main taproot; taro — compressed stem tuber
(corm); cauliflower — massed flower head; pineapple — fused mass comprising of
unfertilized flower parts and main flower stalk; cabbage and lettuce — whole above-
ground vegetative growth; spinach — leaves; leeks — swollen leaf-base; mango and
avocado — fleshy fruit with single seed; tomato, citrus, banana, and pepper — fleshy
fruit , with several seeds; okra, green bean, and yard-long bean — immature green
pods with partly developed seed; green pea — immature seed. 1 Consequently, fruits
and vegetables have different physical and chemical characteristics and responses
vary to postharvest conditions and treatments to which they are subjected. Handling
of crops to maintain quality and lengthen their storage life is specific according to
the commodity, time, and environmental conditions.
STORAGE LIFE OF AGRICULTURAL PRODUCTS
The following metabolic processes and events affect the postharvest storage life of
agricultural produce and are important controlling factors in postharvest handling.
R ESPIRATION
This is a basic reaction of plants before and after harvest. Harvested plant materials
continue to respire and use the stored starch or sugar to maintain their structural
integrity. Since the stored food is not replaced, senescence follows and the produce
eventually decays. Respiration causes weight loss, excessive CO 2 build-up in storage,
and triggers a host of other metabolic reactions such as ethylene synthesis, color,
texture, and flavor changes.
T RANSPIRATION
Harvested produce rapidly lose water from their surfaces in a process known as
transpiration. Transpiration is a major component of weight loss in fruits and veg-
etables. A 5 to 10% weight loss will cause significant wilting, shriveling, poor texture,
and poor taste. 3 Moisture loss occurs rapidly in a warm, dry environment especially
among injured products, and it is affected by commodity characteristics such as
surface area to volume ratio, presence of waxy substances in the skin, tenderness