Postharvest Handling of Potatoes
Introduction
White potato is a high value commercial crop. It is very nutritious and has many uses. Potato is used in the manufacture of snack foods, chips, French fries and as ingredient insalads, soups and some bakery products.
Many fast food chains in the country use potatoes as French fries. Demand for French fries increases with rise in number of fast food restaurants.
Meanwhile, the potato chips industry is also expanding . A daily demand of about 400 to 533 metric tons of fresh potato is needed in processing of potato chips.
The increasing demand for processed potatoes is currently not being met. First, supply is not continous. High postharvest handling losses also occur because of poor roads and lack of postharvest facilities. To prevent damages and reduction in quality of potato and avoid large fluctuation in supply and price, improved postharvest practices should be used. Good quality potatoes command a better price in the market.
Dehaulming or patpat
Cut the haulms or stems at ground level five to seven days before harvesting.
Cutting of haulms longer than a week may be done for better quality tubers that do not lose much weight while in storage. But precautions are needed against thieves when cutting haulms longer than a week.
Why dehaulm?
-The potato skin will harden;
-Tubers will firm up;
-there will be lower risk of skinning or feathering or maladlad during harvesting and handling;
-harvesting will be easier, and late virus infection will be avoided.
Harvesting
Harvest the crop in 90 to 120 days. Harvesting depends on variety, season, price, intended use and cash need of the farmer.For processing, potatoes with longer maturity is preferred for higher dry matter.
When harvesting potatoes the following should be considered:
-the number of days from planting
-80 to 85 percent yellowing of the leaves; and
-tuber sampling
A fully mature potato crop produces more tuber yield, lower sugar content and dry matter content. It is also less prone to damages during harvesting and handling.
Early harvesting could lower the crop yield and produce tubers that are easily skinned, feathered or damaged, and short shelf-life.
Harvesting is preferably done early in the morning and when soil is dry. Potatoes harvested when soil is wet cannot be stored longer. In Benguet and Mountain Province, harvesting is usually done manually using spading fork for loosening the soil; and a sharpened stick for exposing the tubers. Digging of tubers could be done in loose soil.
Care in harvesting is necessary to avoid skinning, cuts, cracks and internal bruises. These damages encourage disease infection, and may serve as entry points for tuber moths and other pests.
Curing
Newly harvested potatoes could be cured so that wounds, bruises and cuts will heal and the skin will harden. Or spread tubers thinly in a well-ventilated room for 6 to 7 days.
Cure by simply exposing the harvested tubers to sunlight for few hours to dry and promote rapid curing or wound healing.
Or air dry in the packing shed before packing. Curing is necessary for both table and seed potatoes.
Sorting / Grading
Separate marketable tubers from the non-marketable. Sorting is based on tuber size. Grade or classify tubers according to variety standard quality and size specifications. Different varieties and or sizes vary in their storability characteristics. Ideally, sort and grade after curing or when tuber wounds have healed. Potatoes will feather if these are harvested immature then sorted right in the field and simultaneously packed into bags , crates or baskets.