Detailed Guide to Potato Storage Methods: Teaching You How to Store Scientifically

I. Chemical and Physiological Changes During Storage

When potatoes are harvested, the tubers generally contain about 75% moisture. During storage, they have very strict requirements for temperature, humidity, light and air conditions. If these are not adjusted properly, they will cause adverse changes in physiological state and chemical composition.

During storage, the physiological and chemical composition of potatoes is constantly changing. With changes in temperature, humidity and light, their respiration intensity changes accordingly. Due to respiration, weight can be reduced by 6.5-11%. If maturity is insufficient, nitrogen fertilizer is excessive, or potassium chloride alone is used, the weight loss will be even greater. With changes in temperature, starch content drops rapidly. As storage time lengthens, starch content gradually decreases, and a series of changes also occur in various other nutrients and chemical components.

II. Losses During Storage

Potatoes suffer relatively high losses during storage, generally divided into two categories: natural loss and waste. Natural loss is the loss of moisture and dry matter caused by respiration and evaporation. Reasonable adjustment of storage conditions can reduce natural loss to a minimum. Waste is caused by rot, abnormal temperatures, oxygen deficiency and light, etc., which reduces the tubers' value for food, processing and seed use. To avoid and reduce the occurrence of waste, it is essential to strictly prevent infection by pathogenic bacteria, control abnormally high and low temperatures, regulate humidity, air and light, and prevent serious damage such as rot injury, heat injury, freezing injury, oxygen deficiency and suffocation, and dehydration.

III. Environmental Conditions for Storage

The environmental conditions inside the storage cellar mainly include: heat, temperature, humidity, carbon dioxide, light and ventilation.

Heat: During storage, heat has four sources: original heat (the heat originally contained in the tubers themselves), respiration heat (heat produced by tuber respiration), external heat (heat from air outside the cellar flowing into the cellar) and soil heat (warm currents conducted from underground into the soil). Among these, soil heat is the main source of heat used by the storage cellar.

Temperature: Storage is very closely related to humidity. At -5°C, tubers freeze in 2 hours and freeze through in 4 hours. Under long-term 0°C conditions, sprouting ability weakens. The suitable storage temperature for seed potatoes is 1-3°C, giving the highest yield.

Humidity: The safe range of humidity change during storage is 80-93%, and it is best controlled between 85-90%. Appropriate humidity can reduce natural loss and help keep tubers fresh. Too much moisture easily promotes early sprouting of tubers and the formation of fibrous roots, reducing food and seed quality. Too dry easily causes tubers to lose water, soften, shrink and lose plumpness.

Ventilation: This can regulate air circulation in the cellar, introduce fresh air, increase oxygen, remove accumulated carbon dioxide, ensure tuber respiration, and thereby ensure field sprouting of tubers and vigorous seedlings.

Light: Although it has little effect on the storage of seed potatoes, it still has some influence. When storage conditions are poor, a certain amount of light can be provided to make the skin turn green, which helps inhibit infection by pathogenic bacteria and inhibit excessive sprout growth, forming short, sturdy sprouts and helping increase yield. For processed commercial potatoes, however, light is not suitable, so as to avoid increased solanine and reduced quality.

IV. Management During the Storage Period

After entering the cellar, strictly implement scientific management. Through measures such as regulating cellar temperature, humidity, ventilation and air exchange, and turning the pile, prevent rot caused by disease and freezing injury, avoid shrinkage and sprouting, and ensure excellent varieties that meet different needs for food, processing and seed use.

1. Turning the Pile

Frequently check changes in cellar temperature and the occurrence of disease to make decisions. When the temperature in the pile rises from originally very low to above 8°C, promptly identify the cause and find ways to control it. If heating occurs due to disease and rot, turn the pile promptly. When the temperature is normal, if 3-5% of the pile is found infected with soft rot, more than 10% with dry rot, or more than 3-4% with freezing rot, the pile should be turned immediately. When turning the pile, remove all diseased and freeze-rotted tubers. If the above conditions are found during storage, the pile can be turned 1-2 times. If, before entering the cellar, the potatoes have undergone a certain period of drying and ventilation, are strictly selected when entering the cellar, and temperature and humidity are well controlled after entering the cellar, turning the pile may not be necessary.

2. Regulation of Temperature and Humidity

First, regulation of the cellar: in principle, keep the cellar temperature at 1-3°C. At the beginning of entering the cellar, pay attention to preventing heat. When the outside temperature drops to -5-10°C, block the cellar door and ventilate briefly at noon each day. Before the Beginning of Spring, place grass or plant stalks on top of the pile and over the cellar door and air holes for insulation. When the weather changes later, again prevent hot air from entering the cellar.

Second, regulation of pile temperature: inside the cellar, the pile height is generally above 1.5-2 m, with 5 m being suitable, and at 1/2-1/3 of the cellar depth, which is good for air circulation. Potatoes entering the cellar are best held in mesh bags, placed neatly, with certain gaps left. If stored in bulk, a cross-shaped ventilation trench should be dug at the bottom of the cellar, with both width and depth suitably 20 cm, covered with tree branches, leaving certain gaps, with the trench connected to the cellar wall. In the pile, insert ventilation stakes 20 cm in diameter, extending 30 cm above the pile height.

Third, regulate cellar humidity through air exchange at the cellar door and air holes. Keep the humidity inside the cellar at 80-93%. This is mainly because after the Beginning of Spring, tubers in the upper layer of the pile show the "sweating" phenomenon of water droplets, which promotes the occurrence and spread of disease. By spreading grass or straw curtains on top of the pile, the sweating phenomenon can be solved and insulation can also be provided.

V. Calculation of Cellar Capacity

The quantity of tubers in the cellar should maintain a certain relationship with the cellar capacity. When the maximum potato pile height is 2/3 of the cellar depth, 65% of the cellar volume can be utilized. Generally, each cubic meter of tubers weighs 650-750 kg. The larger the tubers, the lighter the weight per unit volume; conversely, the heavier. As long as the cellar volume is measured, the suitable amount for storage can be calculated. Calculation method: total cellar volume x (650 x 0.65) = suitable amount for storage (kg)

For example: when the cellar is 10 m long, 5 m wide and 4 m deep.

Suitable amount for storage = (10 x 5 x 4) x (650 x 0.65) = 84500 kg