CENTER, Colo. — Potato storage is to maintain quality and quantity of marketable tubers during the storage period in order to maximize growers’ returns. The most important issue during potato storage, beside spoilage, is weight loss. Weight loss (shrinkage) occurs due to physical water loss throughout transpiration and respiration. Annual losses in potato storages due to weight loss are about 12 million cwt (2015 NASS data). There are three basic tools of potato storage management: temperature, humidity, and airflow. Ventilation is required to remove the field and respiratory heat of the potato tubers, as well as prevent condensation and accumulation of carbon dioxide. There are many factors that influence ventilation that include: pulp temperature, air temperature, relative humidity, CO2 concentration, condensation, shrinkage, and energy efficiency.
Currently, most of the potato storages use either continuous ventilation or intermittent airflow. The ventilation rate recommendations range from 20 to 40 cubic feet per minute (CFM) per ton depending on intended usage and the local climate. Both types of the ventilation systems have advantages and disadvantages.
We designed this ventilation experiment to study the effect of different fan settings on weight loss in Rio Grande Russet after wound healing. We used three fan speeds, low (0.6 CFM), mid (13 CFM), and high (52 CFM) attached to 52-gallon drums filled with Rio Grande Russet tubers. The control is a drum with tubers but no fan in both experiments: a continuously running fan (24h/d) and an intermittently running fan (once/3h). The drums were stored in a controlled environment at a temperature of 40±2°F and a relative humidity of 90±4%.
We monitored the weight loss, respiration rate, texture change, temperature and RH during the storage period. The weight loss was higher in continuous fans operating at high speed (4.2% in case of 52 CFM after six months) than intermittent fans operating at low speed (1.7% in case of 0.6 CFM after six months).
Conclusions & Recommendations:
- There is more weight loss in the case of continuously operating fans at high speed and less in the case of timed fans running at low speed.
- The advantage of using intermittent ventilation is power savings, but humidity maintenance above 95% may not be possible in the storage.
- In North American climatic conditions, we recommend the slowest fan speed that can move humidity through the pile during the holding period.
— Esam Emragi and Sastry S. Jayanty*
*Associate Professor and Extension Specialist
San Luis Valley Research Center, Department of Horticulture and Landscape Architecture, Colorado State University
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