Fabrication of ventilated structure for storage of onion
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Date
2017
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Punjab Agricultural University, Ludhiana
Abstract
Onion is an important crop of the country that is consume throughout the year. Recently due to
greater economic return associated with this crop, the farmers in our state have also paid enough
attention for the cultivation of this crop. Looking at the physiology of this crop there is a lack of
proper storage structure for keeping the bulb for such a long time so the present study was
undertaken to develop suitable storage structure. As storage life of the onions is linked with its
harvesting at proper stage followed by thorough curing. Properly harvested onion crop at
vegetable farm of PAU was field cured. It was also cured in shade as well as in mechanical
drier. Using this information a ventilated onion storage structure of capacity 1.25 tonn was
fabricated. The results indicated that the highest losses (22.55 %) were recorded when the
onion cured at the open field for 5 days, followed by shade curing treatment (18.08 %) for 9
days and the lowest losses were 15.8 % for the artificial curing treatment at the end of storage
period. Physical characteristics of onions i.e. average size, angle of repose and bulk density
was calculated as 32.75-68.67 mm, 26⁰ and 560 kg/mᶟ respectively. Ventilated storage
structure was (size 1.2m х 1.2m х 1.5m) made up of angle iron frame and MS 1 inch square
mesh. For ease of loading and unloading the onion, an inclined surface at the base with angle
of repose 26 degrees has been provided. Three axial flow fans at the base of ventilated storage
structure created variable air flow rate with air velocities of 0.27 m/s, 0.32 m/s, 0.69 m/s, 0.9
m/s and 1.38 m/s. Onions in bulk were filled in the structure and samples of 10 kg of 5 onion
bags were kept at different location within the structure and at different air velocities for this
study. The variations in vital parameters were compared with commercially cold stored onions
in cold stores (0 to -1⁰C). It was observed that PLW, sprouting, TSS, colour difference,
moisture content, hardness, ascorbic acid and reducing sugars during 3 months of storage varied
significantly at CD 5% level of significance. This study indicates that onions which were stored at air speed 1.38 m/s and cold stored showed minimum loss and maximum retention of
chemical properties. But due to high rent of cold stored onions, cold storage is not normally
preferable in India.
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