Production Practices and Quality Assessment of Food Crops. Vol. 1

262 M. Ruiz-Altisent et al.
2. HARVESTING FUNCTIONS
While detachment and removal, control, cleaning and selection, conveying and
loading are the required functional operations for a harvester, the order in which
these functions are achieved is determined by the requirements of the specific product
or commodity (as an example, hand harvesting always begins with selection)
(Srivastava et al., 1993). In mechanical harvesting systems, detachment is seldom
as selective as desirable, therefore the selection function is achieved after detachment,
in the form of sorting devices (or even manual sorting in the machine), or
else at a later processing (sorting, cleaning, grading and packaging) inside fixed
premises.
Detachment is the actual separation of the harvested portion of the plant: fruits,
buds, tubers, roots, leaves, etc. Catching and control: padding of catching surfaces
is required to gain or maintain product control during harvesting operations (Ryall
and Lipton, 1972). Good padding materials can absorb the impact energy of the
product, thus preventing its absorption and damage to the fruit; these materials
have to be easy to keep and to clean, and durable.
Selection is the process in which only the ripe, correctly sized or desirable product
is obtained from the entire recovered crop material, while the remainders are rejected.
Size is often associated with product quality. Harvesting machines are sometimes
equipped for size and color grading in the field. Product maturity requires special
attention as the main property of the product which decides harvest date, and defines
the product susceptibility to damage.
Transportation: whenever possible, bulk handling systems are preferred for transportation
of the product from the field to the grading/marketing station. Bulk
handling (trucks or tractor trailers) are used for industry products such as tomatoes,
green beans, onions, potatoes, peaches, wine grapes, olives. Standard pallet containers
can be handled with standard forklift equipment and are used also for fresh
market products like apples, melons, cucumbers, . . . . Delicate fruits like strawberries
need small, market-ready containers; these are also used in appropriate sizes,
for example for ripe peaches and apricots. Vegetables like lettuce, cauliflower,
broccoli, etc. are sometimes wrapped and packed in the field. Today, infield grading
and packaging of produce is contemplated as a good solution for reducing costs
and quality losses in many fresh-market products (vegetables, fruits, from these especially
tropical fruits).
Damage is an important consideration (Ryall and Lipton, 1972). Product bruising,
cutting, scuffing and direct damage to the remaining plant can be a consequence
of mechanical harvest. Damage reduces the value of the commodity in the market;
damage to the remaining plant can affect future crops or life of the plant itself (Ruiz-
Altisent, 1991).
Harvesting functions often interact with each other. For example, if inertial detachment
is used by interacting with the plant, the separated commodity often has an
associated kinetic energy, which aggravates the problem of product control (damages)
when compared to other types of detachment and removal procedures (Ryall and
Lipton, 1972) (Table 1).