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Potato storage technology and store design aspects

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The quality of potato, and its storage life, is reduced by the loss of moisture, decay and physiological breakdown. These deteriorations are directly related to storage temperature, relative humidity, air circulation and gas composition. In an attempt to attain the desired storage condition in an enclosure, many systems have been developed over the years depending on the geographic location, volume produced, consumer demand and the marketing strategies. Potatoes being a living organism require an effective management for storage. Quality of the potatoes cannot improve during storage. Bruise prevention is an important part of keeping quality of potatoes with minimum weight loss and storage diseases. Many attempts have been made by researchers to investigate the suitability of various storage systems over the years for safe storage of agricultural commodities. Conventional refrigerated room, ventilated cold room, bulk storage facilities, jacketed storage and various types of controlled atmosphere (CA) storage like Marcellin and Atmolysair have been used. In this paper, attempts have been made to integrate the application of scientific storage techniques, design factors and management fundamentals into storage systems, to minimize the storage losses.
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M.Eltawil, D.Samuel and O.Singhal “Potato Storage Technology and Store Design Aspects"
Agricultural Engineering International: the CIGR Ejournal. Invited Overview No. 11. Vol. VIII.
April, 2006.
1
Potato Storage Technology and Store Design Aspects
Mohamed A. Eltawil1, D.V.K. Samuel2 and O. P. Singhal2
1Agril. Engineering Division, Faculty of Agric. at Kafr El-Sheikh, Box 33516, Tanta Univ.,
Egypt, email: eltawil69@yahoo.co.in
2Post Harvest Technology Division, IARI, New Delhi-110012, India.
2Agril. Engineering, Division, IARI, New Delhi-110012, India.
ABSTRACT
The quality of potato, and its storage life, is reduced by the loss of moisture, decay and
physiological breakdown. These deteriorations are directly related to storage temperature,
relative humidity, air circulation and gas composition. In an attempt to attain the desired storage
condition in an enclosure, many systems have been developed over the years depending on the
geographic location, volume produced, consumer demand and the marketing strategies. Potatoes
being a living organism require an effective management for storage. Quality of the potatoes
cannot improve during storage. Bruise prevention is an important part of keeping quality of
potatoes with minimum weight loss and storage diseases. Many attempts have been made by
researchers to investigate the suitability of various storage systems over the years for safe storage
of agricultural commodities. Conventional refrigerated room, ventilated cold room, bulk storage
facilities, jacketed storage and various types of controlled atmosphere (CA) storage like
Marcellin and Atmolysair have been used. In this paper, attempts have been made to integrate
the application of scientific storage techniques, design factors and management fundamentals
into storage systems, to minimize the storage losses.
Keywords: Potato, Storage Technology, Irradiation, store design
1. INTRODUCTION
The potato is the most important food crop in the world after wheat, rice and maize. Over one
billion people consume worldwide and potatoes are part of the diet of half a billion people in the
developing counties. Potato ranks 4th in the world and third in India with respect to food
production. In the year 1999- 2000, India produced 25 million tonnes of potatoes from an area of
1.34 million hectares with an average yield of 18.6 t/ha.
Potato is a staple food in the colder regions of the world, while in other parts of the world it is
generally used as a vegetable. In India 73% potatoes are consumed in different forms such as
cooked, roasted, French-fried, chipped etc. Cooking often reduces mineral and vitamin
constituents. In case of processed products it is possible to add missing or low ingredients in
order to enhance overall nutritional value of the product (Shekhawat, 2001).
The potato (Solanum tuberosum L.) is a semi-perishable commodity. Appropriate and efficient
post harvest technology and marketing are critical to the entire production-consumption system
of potato because of its bulkiness and perishability. Unlike in temperate regions, in India the
potato is harvested in the beginning of summer. Due to inadequate cold storage facilities to hold
the produce for longer periods, prices plunge at harvest time and large quantities are spoiled
before they could be disposed off. Consumers are also unable to develop a habit of consuming
M.Eltawil, D.Samuel and O.Singhal “Potato Storage Technology and Store Design Aspects"
Agricultural Engineering International: the CIGR Ejournal. Invited Overview No. 11. Vol. VIII.
April, 2006.
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more potatoes because potato stocks disappear from the market within a few months of harvest
and in later part of the year relative prices of potato are high. Per capita consumption of potatoes
in India is 18.3 kg a year as against the world average of 52.7 kg, in spite of increase in
production in recent years (FAO, 1991).
Egypt is one of the largest producers and exporters of potatoes in Africa. Potato is the second
most important vegetable crop after tomato (El-Tobgy, 1974). In 1996, Egypt produced 2.6
million metric tonnes of potatoes and exported 411,000 metric tonnes valued at nearly US $80
million to Europe and the Arab countries. Small farmers grow 65% of these potatoes. In year
2000 Egypt produced 1.784 metric tonnes from an area of 83000 Ha with average yield of 21.49
t Ha-1 (FAO, 2000). 2. STORAGE OF POTATO
The purpose of storage is to maintain tubers in their most edible and marketable condition and to
provide a uniform flow of tubers to market and processing plants throughout the year. Four
variables to determine storage losses are the potato variety, pre-storage conditions, storage
conditions and storage duration. It must be realized that storage losses cannot be avoided even by
optimal storage. Good storage can merely limit storage losses in good product over relatively
long periods of storage. Storage losses are often specified as weight losses and losses in the
quality of potatoes, although the two cannot always be distinguished.
Storage losses are mainly caused by the processes like respiration, sprouting, evaporation of
water from the tubers, spread of diseases, changes in the chemical composition and physical
properties of the tuber and damage by extreme temperatures. These processes are influenced by
storage conditions. All the losses mentioned above depend on the storage conditions and
therefore can be limited by maintaining favourable conditions in the store. However, the
storability of potatoes is already determined before the beginning of storage, by such factors as
cultivar, growing techniques, type of soil, weather conditions during growth, diseases before
harvesting, maturity of potatoes at the time of harvesting, damage to tubers during lifting,
transport and filling of the store (Rastovesky, 1987 and Burton et al., 1992).
The four main outlets for stored potatoes are: seed potatoes, household consumption, the
processing industry and potatoes as raw material for the production of starch or alcohol. Choice
of storage method must be considered by the requirements for each purpose, but for all uses
wound healing is essential immediately after harvest.
Good storage should prevent excessive loss of moisture, development of rots, and excessive
sprout growth. It should also prevent accumulation of high concentration sugars in potatoes,
which results in dark-coloured processed products. Temperature, humidity, CO2 and air
movement are the most important factors during storage (Harbenburg et al., 1986 and Maldegem,
1999).
Varns et al. (1985) investigated the potato losses during the first three months of storage for
processing. It was observed the sampling of three respondent groups includes a local storage
region, the processing industry, and the federal inspection service (USDA). Questionnaires
indicated that 64 to 150 thousand metric tons were annually lost during early storage from the
total crop stored for processing. This constitutes a range of 5.6- 13.2 million dollars lost in
production costs.
M.Eltawil, D.Samuel and O.Singhal “Potato Storage Technology and Store Design Aspects"
Agricultural Engineering International: the CIGR Ejournal. Invited Overview No. 11. Vol. VIII.
April, 2006.
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Rastovsky (1987) has reported the approx. values of storability of potatoes at different
temperatures (Table 1) and ideal storage temperature for potato as per different uses (Table 2). In
addition to this, the atmospheric humidity must, in general, be as high as possible, in the range of
85 to 90 per cent. The warehouse potatoes must be treated with sprout inhibitors at storage
temperatures above 4°C.
Table 1. Storability of potatoes at different temperatures.
Average storage
temperature, °C Storability, months Average storage
temperature, °C Storability, months
5 6 20 2-3
10 3-4 25 2
15 2-3 30 1
Table 2. Recommended storage temperature for potatoes for different usage.
Purpose Storage temperature, °C
Fresh consumption 2-4
Chipping 4-5
French frying 7-10
Granulation (mashed potatoes) 5-7
2.1 Traditional Storage Practices
Storage methods, which were in vogue in the warm plains of India till recently, are described by
many authors and are as follows. i) Storage in cool dry rooms with proper ventilation on the floor
or on bamboo racks and ii) Storage in pits. The former was generally followed in the plains for
seed potatoes during the period from Feb.- March to Sept.-Oct. Storage in pits was adopted in the
erstwhile Bombay state from Feb.- March till the onset of monsoon season in June (Kishore,
1979).
In Egypt, the bulk of potato storage takes place in traditional structures or nawallas made of mud
bricks. Nawallas are typically privately owned and are concentrated in the northern governorates
with lower average temperatures. Walls are typically from 2.5 to 3.5 m high and 30 to 60 cm
thick. Storage period is normally for 5 months, May to September. Roofs consist of bamboo
matting, rice straw, and mud supported by wood or bamboo frames. Seed potatoes are dusted
with SEVIN and CAPTAN (brand names) and arranged in piles 1.5 to 4 m across and 0.8 to 1.0
m high. The piles are sorted every two weeks and infested, diseased, or damaged tubers
discarded. Rats and Tuber moth are major problems.
Temperatures within the nawallas are not much lower than the ambient temperatures in the shade
outside, although within the heaps temperatures may as much as 10˚C lower. Losses from tuber
moth infestation, dehydration, excessive sprouting, and other causes average about 20-30%,
although losses of up to 70% have been reported. The need for improving storage facilities and
practices for warehouse as well as seed potatoes has been noted by several authors (Geddes and
Monninkhoff, 1984).
M.Eltawil, D.Samuel and O.Singhal “Potato Storage Technology and Store Design Aspects"
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April, 2006.
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2.2 Scientific Storage Systems
2.2.1 Evaporatively Cooled Storage
Evaporative cooling is nature’s very own method. The ancient Egyptians used a primitive form
of evaporative cooling, dating back to about 2500 BC. Evaporation of water produces a
considerable cooling effect and the faster the evaporation the greater is the cooling. Evaporative
cooling (EC) occurs when air that is not already saturated with water vapour is blown across any
wet surface. Thus evaporative coolers consisted of a wet porous bed through which air is drawn
and cooled and humidified by evaporation of the water (Khader, 1999).
The farm level storage system, which is less capital intensive and extends the shelf life of fruits
and vegetables sufficiently to realize better prices after the storage period was very much needed.
EC storage was thus considered to meet the much-desired need and hence studies were initiated
on this aspect in the early eighties at CFTRI, Mysore, CPRS, Jalandhar and IARI, New Delhi
(Rama and Narasimham, 1991).
An open cycle 3-ton air conditioner has been designed to suit the hot humid climate by Gupta
and Gandhidason (1979). The method is based on dehumidification of air by using a liquid
absorbent followed by adiabatic evaporative cooling.
Roy and Khurdiya (1982) constructed 4 types of evaporatively cooled chambers for storage of
vegetables. The first chamber was made of cheap quality porous bricks and riverbed sand, which
was latter known as Zero energy cool chamber. The other three chambers were ordinary earthen
pots placed in three tanks: the first one made of bricks, the second one an ordinary wooden box
and the last, an ordinary fruit basket. The gap in all the cases was filled with sand. The sand and
the gunny bags covering the top of the chambers were kept saturated with water. The cool
chambers maintained a temperature between 23-26.5˚C and relative humidity (RH) between 94-
97% as against the ambient temperature between 24.2-39.1˚C and RH 9-36% during the months
of May-June. Chamber 1, i.e. the Zero energy cool chamber, performed best with the enclosed
air temperature remaining between 23-25.2˚C.
Roy (1984) reported that a 6 tonne cool chamber was constructed, where the side wall was
constructed with two layers of bricks leaving approx. 7.5 cm gap in between them. This gap was
filled with riverbed sand. The floor was made of wooden planks. Below the floor, a 33 cm deep
tank was constructed with 4 air ducts made of bricks opening at the center and submerged under
wet sand. The sand in the wall and surrounding the ducts were saturated with a drip system. The
top of the chamber was insulated and incorporated with an exhaust fan. The air while passing
through saturated duct and walls cooled sufficiently and took away heat from the produce.
Sprinkling of water twice daily was enough to maintain the desired temperature and humidity.
Chouksey (1985) reported the design aspects of a solar-cum-wind aspirator ventilated
evaporative cooling structure of 20-ton capacity for potatoes and other semi perishables, which
was constructed at the Central Potato Research Station (CPRS), Jalandhar. The structure
maintained a temperature of 21-25˚C with 80-90% RH at ventilation rate of 24m3/min when the
outside temperature and RH were 40-42˚C and 30-35%, respectively.
Anonymous (1985) and Roy and Khurdiya (1986) reported the detailed method of construction
of a Zero energy cool chamber. A chamber for storage of about 100 kg horticultural produce was
M.Eltawil, D.Samuel and O.Singhal “Potato Storage Technology and Store Design Aspects"
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April, 2006.
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constructed with two layers of bricks as side walls leaving approx. 7.5 cm gap in between them.
This gap was filled with riverbed sand. The top of the storage space was covered with khaskhas/
gunny cloth in a bamboo-framed structure. There was no provision for mechanical ventilation.
The sidewall and top cover were kept completely wet during the period of storage. It was
observed that the cool chamber had a temperature of less than 28˚C during summer, when the
maximum outside temperature was 44˚C. The average minimum temperature of the cool
chamber was either less than or near the outside average minimum temperature, excepting in
winter, when it maintained a few degrees centigrade more than the outside average minimum
temperature.
Habibunnisa et al. (1988) fabricated a metallic EC chamber measuring 45 x45 x 45 cm (approx.
0.1 m3) with a 2 mm GI sheet with the top side open. The four sides of metallic chamber were
covered with a cloth, the top ends of which were immersed in water placed in the top tray. For
allowing evaporation, the cloth surrounding the metallic chamber was made to remain wet
continuously by downward gravitational flow of water. A wire mesh basket of size 30 x30 x 30
cm filled with fruits was kept inside the chamber, leaving adequate space all around the basket
for circulation of the air. The EC storage increased the shelf life of apple by 6 times and Coorg
mandarins by 4 times.
Rama et al. (1990) studied the relative performance of two models of EC storage structures with
regard to their efficiency in maintaining the temperature close to the ambient wet bulb
temperature and high RH The first structure was the same as that used by Habibunnisa et al.
(1988). The second one resembled the first one except that the outer metallic wall was replaced
by a weld wire mesh (2.5 x 2.5 cm) with evaporative sides covered with wet gunny cloth to help
in free movement of evaporatively cooled air. The top tray used in this system (to serve as the
water reservoir to wet the gunny cloth) was devoid of vents. The inside temperature for both the
systems were almost similar and close to the ambient wet bulb temperature and the relative
humidities were 90 ±5%, respectively. The lower RH of the system 2 was attributed to the free
air circulation through the structure.
Sharma and Kachru (1990) used evaporatively cooled sand stores, where a 5 cm thick potato
layer was placed on floor in between two sand layers each of 20 cm thickness. In order to allow
evaporative cooling, 2.1 m3 of water was sprinkled daily to wet the sand. It was observed that
under low atmospheric RH conditions, wet sand was suitable for storing potatoes for up to 90
days as compared to 60 days in jute bags and still less in other storage methods like bamboo
baskets and heaps.
Umbarkar et al. (1998) constructed an EC structure of 2 tonne capacity based on the results of
their previous studies (Umbarkar et al., 1991). The walls of the structure were constructed with
10 cm thick brick batt pad sandwiched between two 10 cm thickness brick perforated walls. To
add to the structural strength, 8 mm diameter mild steel reinforcement anchored the latter with
each other. Holes of 50 x 40 mm were provided between two successive brick layers for air
circulation throughout the height of the structure. A thatched roof with bamboo mat and dry
grass was provided as cover at the top. At the bottom of storage stacks, a free board of 10 cm
was left for bleed off water from walls. The temperature in the chamber varied between 23-
26.5˚C as against ambient temperature variations between 25-44˚C on a test day. The RH. in the
structure was 85-97%. The water requirement was 325 litres per day.
M.Eltawil, D.Samuel and O.Singhal “Potato Storage Technology and Store Design Aspects"
Agricultural Engineering International: the CIGR Ejournal. Invited Overview No. 11. Vol. VIII.
April, 2006.
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Dash (1999) developed a mathematical model for analysis of time dependent thermal
environment in evaporatively cooled storage structures. Simulation studies indicated that the RH
inside the EC structure would remain close to 100%, throughout the year and maximum
advantage of evaporative cooling could be obtained under low ambient RH conditions. The
structural orientation had a negligible effect on the inside thermal environment of the EC
structures. The cumulative heat units was lowered by 8.1, 8.23, 3.2 and 4.8% by shading the
structure during the month of January, April, July and October, respectively. The cost of storing
one kg of potato in a 1.0m3 EC structure for about 100-120 days storage period were Rs. 1.14
and Rs. 1.17 (1US $ = 46 Indian Rupees) in the pad and brick structures, respectively. In a 25m3
structure (for 8 tonnes potato), the cost of storage was Rs 0.97/kg.
2.2.2 Cold Storage
The cold storage is serving mankind by preventing the spoilage of perishable commodities and
making them available off-season and in places where they are harvested. This also serves the
dual purposes: the growers of the perishable produce need not require to sell out their produce in
hurry at throwaway price and protect the nation from shortage of commodities due to spoilage of
food during off season.
A solar cold store could help the farmer in rural areas to store seasonal agricultural produce for
several months. Winter-grown vegetables like onions and potatoes are usually stored for 2-5
month before being supplied to the market.
In India studies by Mann and Joshi (1925) on the preservation of potatoes with minimum
wastage emphasized the need for cold storage. The storage of potatoes in cold stores was started
commercially at Karachi in 1932. The Meerut cold store was started in 1938 and others followed
(Singh, 1974). Cold storage facilities in India are shown in Table 3. More than 85% of the potato
production in India takes place during winter season till March and they must be stored for
warehouse purposes to meet the demand from May to October. This period is characterized by
high ambient temperature and low RH, which accelerate the deterioration. A report indicated that
due to inadequate cold storage space; only 41% of the total output (19.2 million tones) of
potatoes (1995-96) could be kept in refrigerated storage facilities (Dahya et al., 1997).
About 3.4 m3 of volume is required per tonne of potato to be preserved while for onions this
value is about 5.7 m3/t. Thus, one can calculate the total volume of storage space as soon as the
amount of storage product is known (Prasad, 1999).
The earlier cold storage were cubical in shape in order to minimize the surface area for a given
volume, i.e.,
a = b = H =V1/3 (1)
Where a, b, H and V are width, breadth, height and volume of storage space. In doing so the
height of large cold storage becomes too big, causing material handling, stacking and similar
other problems. A comparative study of the single and multi-storeyed cold store buildings has
been made with respect to space and installation (Heinze, 1973). It has been found that the
single-storeyed buildings turn out to be a better choice. However, the multi-storeyed cold
storages with mechanized arrangements are preferred for the multi-variety systems, especially in
cities where the floor area is extremely expensive.
M.Eltawil, D.Samuel and O.Singhal “Potato Storage Technology and Store Design Aspects"
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Table 3. Commodity-wise distribution of cold storage facility in India.
Commodity Capacity (Million tonnes) Percentage of Total
Potatoes 7.67 87.76
Multipurpose 0.75 8.56
Other fruits and Vegetables 0.17 1.98
Fish and Marine Products 0.06 0.75
Others 0.08 0.95
Total 8.73 100.00
Source: Floriculture Today (1998)
Sometimes cold storage size is based on floor area, i.e., about 100 kg m-2. However, there does
not exist a unique specification agreed upon and used internationally. Despite lots of discussions
differences on specification on the cold storages exist.
To name a few, the cold storage is specified on the gross volume or net volume or the capacity to
store commodity or tonnage of the refrigeration system (Prasad, 1999).
Giri and Bovne (1978) designed a one-ton solar powered cold storage plant. They proposed the
guideline for the development of 10-20 ton capacity refrigeration plants for rural applications.
Once produce is placed in the cold store, the heat from the produce is transmitted to the air,
which transfers this heat to the evaporator, which in turn removes it in the normal mechanical
refrigeration cycle. The cooling of the air and hence the cooling of produce is speeded up by the
presence of electric fans mounted across the evaporator coils and may be supplemented by
circulatory fans placed in the room and directed across the produce.
The time it takes for the produce to reach the optimum storage temperature (sometimes called the
pull-down time) will be limited by the overall refrigeration capacity of the equipment and the
speed of the air passing over the evaporator and over the produce assuming there are no barriers
to air circulation around the produce.
In the refrigeration industry, the unit used is ton refrigeration (TR). It is equivalent to the rate of
heat transfer needed to produce 1 ton (1000 kg) of ice at 0˚C (273.16 K) from water at 0˚C
(273.16 K) in one day.
(
)
(
)
[
]
1
11
11 5655
6024
801000
1
== mincalk.
hminxdh
kgcalkxdkg
TR
Rapid air movement over produce enhances water loss and so in most refrigerated stores for
long-term storage, air circulation is moderated to keep water loss to a minimum over the storage
period. Produce temperature reduction under these conditions will be slow and the rate of
respiration will only be slowly reduced.
2.2.3 Vapour Compression Cooling
Any liquid, when it evaporates, takes a certain amount of outside heat to change from liquid into
vapour form without any increase in its temperature. This amount of heat depends upon the
characteristics of the liquid and it is known as the latent heat. It is the utilization and removal of
this heat, which causes cold and more the latent heat of evaporation of a liquid the better it is to
use as a media for producing cold. To produce cold by mechanical means i.e. by refrigeration,
M.Eltawil, D.Samuel and O.Singhal “Potato Storage Technology and Store Design Aspects"
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April, 2006.
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the above principle is used. Vapour compression system is referred to as mechanical refrigeration
by different authors.
2.2.4 Forced Draught Cooling
In this system, the produce is stacked in the manner like in a cold store with a high refrigeration
capacity. A sheet of canvas or other material is placed over the stacked produce and a powerful
electric fan sucks cold air rapidly from the room through the packed produce.
Although the rapid air movement creates more water loss from the produce, cooling is much
more rapid than otherwise and the respiration rate is reduced very quickly. As soon as the
produce has been cooled down to close to the optimum storage temperature, it can be transferred
to an ordinary cold store for the rest of its storage life. There are many different types of forced-
draught cooling systems and most depend upon the produce being in appropriate containers –
often fiberboard cartons. Ships and containers adapted especially for refrigeration and carriage of
fresh produce use a variation of this system.
2.2.5 Ice-bank Cooling
This is a relatively recent development in which heat is removed by melting a large block of ice,
which has been built up over a period of days by a small refrigeration unit. The heat is removed
from air in the store by passing it through sprays of ice-cold melt water in a chamber separate
from the store. In this way cool air of very high relative humidity can rapidly cool the store and
the produce.
Temperature of ventilating air is reduced at the rate of –17.5°C per day until holding conditions
is reached. This is first done by measuring the return air temperature (although measuring the
bulb temperatures at the top of the pile will be more accurate). If the return air temperature is
within -16.7°C of the set temperature, it will be necessary to lower the set temperature at the rate
mentioned above. The best time to measure the return air is during early morning hours because
the pile would have gone through an extended period of cooling through the night. Ventilation
should always be provided during cool down. Once the conditions inside the storage are
stabilized, daily ventilation carried out should be long enough to maintain a –17.2 to –16.7°C
differential between the bottom and the top of the pile. Increasingly, fans are being run in shorter
cycles (at the rate of 2 to 4 hours per run with a break of at least 2 hours). The shorter cycles
tends to reduce extreme pile temperature difference between the top and the bottom. The point to
remember is that if the fans are stopped for long periods, the pile tends to get warmer; therefore,
it will require more time to cool down. This recommendation is fairly new and therefore storage
managers are advised to check the efficiency of the air system before making any changes.
2.2.6 CO2 Control System
In a storage room equipment with a CO2-control system, the desired Co2 levels are maintained by
controlling the airflow to the scrubber or by regulating the outflow into the storage area. There
are four main reagents, which are commercially used for CO2 absorption. They are: water,
Hydrated lime, activated charcoal, and molecular sieve. In these systems, the O2 levels are
usually maintained by introducing outside air into the storage room.
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2.2.7 Irradiation
During the past three decades, ionizing radiation has come into use as a means of food
preservation. This method has been recognized as the only new method of food preservation
since the invention of food canning by Nicolas Appert in 1890. The radiation treatment consists
of exposing a product to electromagnetic radiations or accelerated electrons. These radiations
interact with the product matter including chemical changes, ionization and excitation, which
alter the normal life process of living cells. Ionizing radiation can kill bacteria, delay ripening,
inhibit sprouting or impair insect reproduction without heating or using chemical treatments.
Low-dose irradiation of potatoes produced no detrimental effects on potato flavour (Pederson,
1956). Panalaskas and Pellefier (1960) found that specified level of gamma radiation did not
cause consistent variations in the ascorbic acid content of potatoes. Mikaelson and Roer (1956)
reported that the vitamin C content decreased in both the irradiated and non-irradiated potatoes
during the first 7 months of storage at 5°C but was restored after this period, and that the
ascorbic acid levels of the irradiated potato samples were higher than those under control.
Tatsumi et al. (1972) reported their experiments on mechanism of browning. The results showed
that the O-diphenol content increased in irradiated potato tubers (Table 4) and the rate of
increase was greater in the cortex and vascular bundles than in the pith. The ascorbic acid
content decreased with increasing levels of irradiation dose, the rate of decrease being greater in
the cortex and vascular bundles than in the pith. According to Wills et al., (1981) irradiation of
potato and onion is more expensive than treatment with chemical sprout inhibitors like CIPC and
MH.
Table 4. Ascorbic acid and O-dephenol contents after irradiation.
Irradiated 1 day after harvest* Irradiated 3 months after harvest* Doses
(krad) Cortex Vascular
bundle Pith Cortex Vascular
bundle Pith
Ascorbic acid
0 18.2 18.5 19.3 9.3 9.8 7.6
10 11.3 12.5 15.5 8.9 8.3 6.7
20 15.4 11.0 11.7 7.2 7.1 7.3
40 9.9 10.4 10.1 7.6 7.6 7.3
O-dephenol
0 3.2 3.4 2.0 5.7 3.6 1.2
10 8.4 7.2 4.4 6.0 5.7 0.6
20 10.8 7.6 4.8 5.4 6.6 0.9
40 11.7 8.4 4.6 3.9 6.0 0.0
* mg/100g fresh weight of potato tubers
source; Tatsumi et al. (1972)
3. POTATO STORAGE DESIGN PARAMETERS
To achieve the best results in efficiency and economy, cold storages should be designed and
constructed properly. The first step, while installing a cold storage plant, is the selection of
proper site. The cold storage building is an expensive structure and must be considered as a
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April, 2006.
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permanent building. Therefore, the site should be selected, keeping in view the long range
planning of production operations, and plant expansion.
3.1 Storage Building Structures
The basic functions of storage buildings are i) retention of the stored product; ii) protection of the
commodity against weather; and iii) to provide a micro-environment in which temperature, air
circulation, relative humidity and atmospheric composition can be easily controlled. The storage
building should be constructed on a well-drained soil, at a location that meets all the
requirements of the owner. Provisions for parking, receiving, shipping, storage for empty
containers, waste disposal, and future expansion should be made. Building floor plans are to be
designed according to the nature and the amount of the product to be stored and handled, the
space availability, the type of operation planned and costs involved. A flow diagram that shows
the path of all traffic as the product is received, stored, handled and shipped is most suited at this
stage of planning. Figure 1 show the important components of storage.
Fig. 1. Flow chart showing the various components of storage.
3.2 Static Load on Storage Building
There are three load factors to consider when designing a potato storage building (Brook et al.,
1995). (i) Wind and snow loads for the local geographic area. Most building contractors know
the wind and snow load factors required for their area. Another source is ASAE Engineering
Practice EP 288, Agricultural Building Snow and Wind Load (ASAE, 1994). (ii) Maximum floor
load, primarily due to loaded field trucks. Another source is ASAE Engineering Practice EP 378,
floor and suspended loads on agricultural structures due to use (ASAE, 1994). (iii) Static
Loading of Potatoes on the Sidewalls of the Building. For vertical walls, these static loads should
be based on design information in ASAE Engineering Practice EP 446, Lateral Pressure of Irish
Potatoes Stored in Bulk (ASAE, 1994). The values of lateral forces from potatoes can be
calculated with the following expression:
Material
Concrete,
Masonry Blocks,
Wood, Steel
Foundation
Insulation,
Vapour barriers,
Gas seal
Storage
building
structure Storage
operation
System
layout
Instrumentation
Sensors, Acquisition
and control system
Air Cooled,
Mechanically
Refrigerated, High
Relative Humidity,
CA Storage
Food
Irradiation
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L = 17.8 + 8.52 H – 0.18 H2 (2)
Where: L = lateral force, lb/ft2 and
H = the depth of potatoes in the bin, ft (Schaper and Herrick, 1968).
However, the angle of repose of clean potatoes is about 37˚ relative to a horizontal surface, and
the storage capacity of the building will be reduced at the natural angle of repose. Measurements
of pressures on the walls of reinforced concrete bins 122 m long and 18 m wide from potatoes
piled 6.1 m deep showed lateral pressures upto 11.5 Pa at 1.22 m above the floor (Powell at al.,
1980).
Since high pressure damages the tubers, causing bruising, the pressure must be limited by
restricting the stack height to 3 to 4 m depending on the quality of the potatoes. With a stacking
height of 3 m, therefore, 2 tonnes of potatoes per m2 can be stored, increasing to 2.87 tonnes/m2
for a height of 4 m (Rastovski, 1987).
3.3 Insulation
A correct insulation helps the store operator to maintain the right environmental conditions for
the storage of potatoes.
In any insulation calculations it is the inside and outside temperatures which are used, as the
actual surface temperature is not normally known. When heat goes from inside to outside, it first
goes into the structure, then through the structure and then goes out of the structure. These inside
and outside surfaces actually provide a resistance to heat flow and the value of coefficient of heat
transfer (U) should be taken into account. This surface resistance can be important particularly in
a poorly insulated structure.
cesresisthermaltheofsumTotal
Utan
1
= (3)
Where: U = thermal transmittance, and
k
x
materialoftyconductiviThermal
materialofThickness
ResistanceThermal == (4)
Therefore for calculation of the heat loss or heat gain of a building, it is the ‘U’ values of the
walls, roof and ceiling, which are required. As mentioned before, the heat transmission through a
structure depends on three factors: the thermal transmittance (the ‘U’ value), the surface area of
the structure (A) and the temperature difference between inside and outside (To - Ti). This can be
expressed as an equation:
Q = U A (To - Ti) (5)
When considering an economic level of insulation, the following factors must be taken into
account:
The annual cost of insulating material used.
The annual capital cost of the plant.
The loss in value of the produce stored as a result of moisture removed by the cooling system.
The temperature being maintained within the structure.
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The period of operation and the ambient temperatures occurring during this period. The costs
of fuel used to heat or cool the structure and its efficiency of utilization.
3.4 Vapor Barrier
Vapor barriers are important for a high humidity potato storage. The most adequate methods of
excluding moisture from the insulation materials are by sealing the insulation using the methods
that may exclude moisture from the insulation (Raghavan and Gariepy, 1984). Methods that may
exclude moisture from the insulation and produce adequate air tightness at the same time are the
sprayed-on polyurethane insulation and the prefabricated insulated steel panels.
3.5 Ceiling
A good ceiling is important in any potato storage, especially those with a truss roof. Space above
the ceiling will provide good venting for the ceiling insulation. The reduced space between the
potatoes and the ceiling will result in less temperature stratification. The ceiling will be warmer
to reduce the likelihood of moisture condensation. Painting the inside of the ceiling black, causes
the ceiling to stay warmer than a light colored surface. Using a material similar to an asphalt
mastic will help reduce moisture transfer through the ceiling while creating rough surface with
less chance for condensation. The attic space (created by the ceiling) needs a ventilation area of
approximately 1/50th of the ceiling surface area (Brook et al., 1995).
Condensation occurs on a surface when its temperature drops below the dewpoint of the air with
which it is in contact. Therefore condensation occurs when relatively warm moist air meets a
cold surface. Condensation should be avoided in potato storage for three reasons (Bishop et al.,
1980):
1. The condensing surfaces remove moisture from the air, which is largely replaced, by moisture
from the crop; therefore every litre of condensation is a direct loss of one kg of crop.
2. The loss of moisture by a crop can affect its appearance and therefore its marketability.
3. If condensation occurs on the ceiling water can drip back into the crop, making it more
susceptible to disease development.
The formation of condensation can be prevented by providing a proper insulation of the walls
and roof.
3.6 Fans and Airflow
The uniform distribution of ventilation air in potato storage is necessary for useful long-term
storage. Uniform air distribution equalizes bin temperatures, maintains the desired environmental
conditions and ensures an even distribution of sprout inhibitors. Good air distribution is provided
by proper ventilation duct design.
Recirculation is the term applied to continuous ventilation with store air, in the case of bulk
storage being introduced through ducts under the potatoes and the air intake usually in the roof
space above potatoes. If the store is sealed, depending for temperature control upon heat leakage
through the structure, the air is rapidly humidified by its passage through the potatoes- the
volume of the air in a filled bulk store could be some 2 m3.t-1, capable of holding at a
temperature of, say 7°C, only about 15 g of water vapour per tonne stored. There will be some of
this water by condensation on cold parts of the structure and by air leakage from the store; there
may also be dilution when it is necessary to introduce outside air, for cooling purposes, but
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nevertheless the store air can often be maintained with a very low WVPD, of the order of 0.5
mbar. In such a case, recirculation is equivalent to continuous ventilation with air with an inlet
WVPD of 0.5 mbar. At the rate of 30 m3.t-1.h-1 this would give an operative WVPD in the stack
of about 0.9 mbar and an evaporative loss of perhaps 0.15% week-1 (Harris, 1992).
Weight loss variations, sprouting problems or disease problems can often be traced to an
improperly designed or unbalanced airflow system. Airflow recommendations vary by
geographical region due to differences experienced during the harvest season. When installing
the fan, a velocity shelf must be used and the fan mounted horizontally with the airflow moving
along the shelf about 3 to 4 m before moving into the air plenum.
Some potato storage systems may utilize one or two other airflow components:
i) Over-pile circulation. It is often used when there is no ceiling in the storage, or when the roof
insulation is inadequate to prevent condensation. Fans are mounted above the pile to force air
movement over the potatoes. Use one or more fans, each supplying an airflow of 0.3 m3 min-1
m-2 of pile surface area.
ii) Powered exhaust fans: These are used in situations where the bin is not scaled sufficiently to
hold the above pile pressure required to force open the exhaust louver. In these situations, use
an exhaust fan that is sized to 25-30% of ventilation capacity must be used. The exhaust fan
should operate only when fresh air is required.
Neale and Messer (1976) studied the resistance of root and bulb vegetables to airflow. The
pressure required to ventilate small stacks of potatoes, red beet, onions and carrots increases by
velocity (0.04 and 0.3 m/s) to the power of 1.8. The pressure drop in a stack of potatoes has been
described as:
P = k v1.8 (6)
Where:
P = pressure drop in mm W.G.,
v = the velocity of the air in m/s and
k = constant.
3.7 Air Tightness: It is important not to let air of a different temperature or relative humidity
into the store or this nullifies the effect of the insulation. Therefore care must be taken to ensure
that all cracks are sealed and that door is a good fit and never left open when it is not necessary.
A separate personnel door should be fitted in the commercial large-scale storehouse so that the
main doors do not have to be opened when the potato is inspected.
3.8 Choice of Colour: A white surface will absorb 50 per cent of the radiation incident on it
whereas a grey surface will absorb 85 per cent of the same radiation.
3.9 Shading: Diffused sunlight has less radiation and so any way that the building or part of it
can be shaded will cut down the solar heat gain.
3.10 Thickness: The rate at which the solar radiation transmitted depends not only on the
insulation value of the walls and roof but also the thickness, and there may be time lag between
the peak incident radiation and the maximum effect on the building. Therefore this ‘flywheel’
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effect means that although the maximum radiation on a roof occurs at midday the effect may not
be felt in the building until late afternoon.
3.11 Orientation: The best way to place a potato store is east- west with the long dimensions
facing north- south. This is so that the rising and setting sun are shining against the shorter walls.
4. HEAT BALANCE IN A POTATO STORE (COOLING LOAD)
Before one goes into the design aspect of various components of the refrigeration system, it is
imperative to know the cooling load of the confined space for which refrigeration system is
needed.
The temperature at which the potatoes are placed in the store is usually higher than the required
storage temperature. So the potatoes first have to be cooled to that temperature and then
maintained at that temperature for the entire storage period. More heat than is being produced in
the store has to be evacuated during the cooling period. Once the storage temperature is reached,
heat evacuation must be equal to the heat production in the store if the required storage
temperature is to be maintained. The refrigeration load for potato store is made up of six basic
components (Bishop et al, 1980; Rastovski, 1987; ASHRAE, 1998; Prasad1999 and Arora 2000)
as follows:
i) Sensible heat gain through walls, floor, and roof.
ii) Heat removed to cool from the initial temperature to some lower temperature (Heat content
of the potatoes).
iii) Respiration of potatoes.
iv) Heat produced by fans.
v) Heat supplied by air renewal.
vi) Heat produced by equipment-related load.
5. POTATO STORAGE MANAGEMENT
It is important to remember that any management guideline is the result of an experience and
typically assumes the storage of good quality potatoes in a normal year. A well-designed
building, proper insulation and adequate refrigeration machinery of a cold storage cannot
necessarily ensure good storage business results. It equally needs vigilant management, careful
operation and maintenance of the plant as well. The cooperative societies putting up cold
storages should select persons with requisite qualifications and experience to work as managers
of their cold storages.
Management of stored potatoes can be divided into several stages as following (Brook et al.,
1995).
iv) Equalization and drying phase- The time immediately after placing the potatoes in storage to
allow the pile to achieve temperature equilibrium. In some wet years, tuber surface moisture
may need to be dried. The ventilation fan should run continuously during the equalization
phase, while the average potato pile temperature is allowed to settle within 2 degrees of the
average pulp temperature upon entry into storage.
v) Wound healing phase- Lignification, suberization, and handling that occurred prior to
storage. Successful curing of potatoes can be achieved by subjecting potatoes at 8-20°C and
at 85% RH for 7 to 17 days. Care should be taken to avoid the condensation of water on the
tubers during curing. The storage temperature during the curing period must not be allowed
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to exceed 22°C, to prevent additional respiration losses and development of any fungus or
bacterial diseases (Booth, 1974; Alam and Devnani, 1979; Kishore, 1979; Sparenberg, 1979;
Meijers, 1981; and Sukumaran and Verma, 1993).
vi) Preconditioning phase- Preconditioning is used to eliminate pools of reducing sugars in
potatoes. The storage environment is maintained similar to the wound healing phase, with the
bulb temperature actively controlled at wound healing temperature.
vii) Cooling phase- The main ventilation fan should run continuously during the cooling phase of
storage to help maintain a uniform pile temperature. Air blown through the potato should be
no more than 1.6 ºC cooler than the potatoes. Time periods when cooling air is available
often exist only in the night, when manual control is difficult, so a control system capable of
introducing fresh air into the storage as available is desirable.
viii) Holding phase- The goal of ventilation (recirculation and fresh air) is to maintain a
uniform pile temperature within one degree from top to bottom of the pile.
ix) Reconditioning phase- The reconditioning phase is the practice of warming the potatoes from
the holding temperature to obtain acceptable process colour if necessary, and to reduce the
handling damage that might occur during unloading.
6. CONCLUSION
Following recommendations may be followed for better management of potato storage.
Improvements to storage system layout should be achieved by considering the various
aspects of marketing strategies and the existing facilities.
The ideal atmosphere for optimum storage conditions should be maintained for the
different cultivars (of potatoes) grown in different soils.
Data acquisition and control systems should be devised and installed for improvement in
management and maintenance of produce and integrated with the handling system.
Irradiation technique that can significantly improve the storage life of commodities
should be adopted.
To avoid quick loading and overloading of storage chambers, it is best to keep tubers in
pre-cooling chambers for one or two weeks before they are transferred to cold storage
chambers. As different potato varieties are stored in the same chamber under identical
storage conditions, this results in heavy storage losses. Therefore, need for identifying the
suitable storage conditions, taking the variety into consideration, is of great and
immediate importance.
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... Penyimpanan kentang dengan traditional storage method (TSR) dilakukan di ruangan dengan suhu, kelembaban, cahaya serta kualitas udara yang tidak dikontrol. Suhu optimal untuk penyimpanan bibit kentang adalah 8-20°C dan kelembaban udara yang optimal untuk penyimpanan kentang adalah 85% (Eltawil et al., 2006). Akibat dari metode penyimpanan TSR dengan model umbi kentang tetap di dalam karung, dihamparkan di lantai atau ada di keranjang maka kerusakan umbi selama penyimpanan akibat serangga serta fungi mencapai 25-50% (Setiyo et al., 2017). ...
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Abstrak Petani di Bali belum mampu menghasilkan bibit yang baik akibat kegagalan di tahap penyimpanan dan masih tergantung pada bibit kentang kelompok G2-G4 yang didatangkan dari luar. Tujuan penelitian ini adalah untuk mengetahui dinamika suhu udara dan kelembaban udara (RH) selama penyimpanan kentang bibit dan perubahan fisik umbi bibit kentang hasil penyimpanan. Parameter yang diukur antara lain suhu dan kelembaban selama penyimpanan kentang, analisis neraca massa dan energi, perhitungan panas respirasi, panas untuk menaikan suhu kentang, panas untuk menguapan air serta panas yang hilang ke lingkungan dengan pendekatan model matematik sederhana. Hasil penelitian menunjukkan bahwa suhu cenderung membentuk pola polinomial orde dua atau kuadratik, sedangkan RH cenderung membentuk pola linier. Suhu ruang penyimpanan kentang berada pada kisaran 29,50 ºC - 29,09 ºC dan RH berada pada kisaran 73,00% - 81,80%. Nilai panas respirasi bervariasi antara 470,26 - 491,30 Watt. Panas yang dihasilkan dari proses respirasi adalah sebesar 72 -143 watt, panas untuk menaikan suhu umbi kentang sekitar kentang adalah 2,02 Watt; 1,81 Watt; 3,80 Watt; 2,60 Watt; 10,70 Watt; dan 15,20 Watt. Panas yang hilang ke lingkungan membentuk pola linier. Para-Para mampu menciptakan kondisi penyimpanan dan penyediaan oksigen yang, untuk perubahan fisik hampir tidak ada. Abstract Farmers in Bali have not been able to produce good seeds due to failures at the storage stage and are still dependent on potato seeds from the G2-G4 group imported from outside. The aim of this study was to determine the dynamics of air temperature and humidity (RH) during the storage of potato seeds and the physical changes of potato seed tubers after storage. Parameters measured included temperature and humidity during storage of potatoes, analysis of mass and energy balances, calculation of respiration heat, heat for increasing the temperature of potatoes, heat for water evaporation, and heat lost to the environment with a simple mathematical model approach. The results showed that temperature tends to form a quadratic polynomial pattern, while RH tends to form a linear pattern. The temperature of the potato storage room was in the range of 29.50 ºC - 29.09 ºC and the RH was in the range of 73.00% - 81.80%. Respiration heat value varies between 470.26 - 491.30 Watts. The heat generated from the respiration process is 72 -143 watts, the heat to raise the temperature of the potato tubers around the potatoes is 2.02 Watts; 1.81 Watts; 3.80 Watts; 2.60 Watts; 10.70 Watts; and 15.20 Watts. The heat lost to the environment forms a linear pattern. Para-Para is capable of creating conditions for the storage and supply of oxygen that, for physical change, are almost non-existent.
... Penyimpanan kentang dengan TSR, traditional storage method dilakukan di ruangan dengan suhu, kelembaban, cahaya serta kualitas udara yang tidak dikontrol. Suhu optimal untuk penyimpanan benih kentang adalah 18-20 °C dan kelembaban udara yang optimal untuk penyimpanan kentang adalah 85% (Eltawil et al., 2006). (Broto et al., 2018) melaporkan bahwa suhu penyimpanan kentang adalah 18-28 ºC pada kelembaban udara 70-90%. ...
... Alayew et al (2014) menjelaskan bahwa suhu sekitar produk hortikultura yang terlalu tinggi dalam kisaran suhu fisiologisnya menyebabkan peningkatan aktifitas enzim dan metabolisme yang memecah makromolekul menjadi molekul sederhana yang menurunkan mutu produk. Sementara itu kelembaban sekitar produk yang terlalu tinggi menyebabkan tumbuhnya mikroorganisme seperti jamur yang menyebabkan pembusukan, sedangkan kelembaban terlalu rendah menyebabkan permukaan kulit keriput dan peningkatan kehilangan berat (Eltawil et al., 2006). Pinjungwati (2020) menjelaskan bahwa penyimpanan kentang pada suhu 13-18 o C dan kelembaban 70-80%, mampu menjaga mutu kentang selama 1 bulan sebelum didistribusikan. ...
Article
The purpose of this study was to determine the performance of the box type potato storage aeration system in terms of changes in temperature and RH of the air during storage. Research on a box type aeration system for potato storage was carried out by measuring the temperature and RH of the incoming air, the temperature and the RH of the outgoing air during storage of potatoes for 21 days. In addition, calculating the heat of respiration, heat to increase the temperature of potatoes, heat to evaporate water and heat lost to the environment using a simple mathematical model approach. The results showed that the temperature and RH of the room and the incoming air flow tended to form a linear pattern, while the RH of the process room and the outgoing air flow tended to form a polynomial pattern. The temperature of the potato storage room was in the range of 24.07-25.70oC and the RH was in the range of 56.0-65.6%. The heat value of respiration varied between 261.42 - 311.88 k.Joule/kg potato tubers, because the storage temperature was 24.07-25.70oC. The heat generated by the respiration process used to evaporate water from the potato tubers to the environment is 6.01±0.3% on average, the average heat to raise the temperature of the potato tubers and the air temperature around the potato is 24.08±1, 3%, and the average heat loss to the environment with the flowing air is 59.89±3.4%.
... We hypothesize that in the environment of potato storage, the rot spreads inwards along with bacteria, causing a local temperature rise which is better sustained in the microclimate inside the tubers' cavities. Our current understanding of the infection suggests that it will likely manifest in storages with inefficient cooling conditions or ventilation or when stored tubers are not evenly distributed which leads to the development of clusters with increased local temperature and humidity [51]. A supplementary experiment with co-inoculation with a culture of Pseudomonas sp. ...
... bacteria, causing a local temperature rise which is better sustained in the microclimate inside the tubers' cavities. Our current understanding of the infection suggests that it will likely manifest in storages with inefficient cooling conditions or ventilation or when stored tubers are not evenly distributed which leads to the development of clusters with increased local temperature and humidity [51]. A supplementary experiment with co-inoculation with a culture of Pseudomonas sp. ...
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A new species, Trichocladium solani, was isolated from potato (Solanum tuberosum L.) tubers from Russia. The species has no observed teleomorph and is characterized morphologically by non-specific Acremonium-like conidia on single phialides and chains of swollen chlamydospores. Phylogenetic analysis placed the new species in a monophyletic clade inside the Trichocladium lineage with a high level of support from a multi-locus analysis of three gene regions: ITS, tub2, and rpb2. ITS is found to be insufficient for species delimitation and is not recommended for identification purposes in screening studies. T. solani is pathogenic to potato tubers and causes lesions that look similar to symptoms of Fusarium dry rot infection but with yellowish or greenish tint in the necrotized area. The disease has been named “yellow rot of potato tubers”.
... The taste and quality of deepfrying potato chips for different potato cultivars with various moistures can be optimized with controlled temperatures and timing if the initial water contents are known [73]- [75]. Proper storage will preserve the potatoes' freshness, preventing spoilage or shrinkage due to significant water loss [76], [77]. Thus, knowing the water content of potatoes in real-time and in situ can make informed decisions. ...
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This work aims to develop a planar microwave sensor fabricated on a flexible polyimide substrate to monitor the water content of fruits nondestructively. The sensor is based on a planar loop resonator tuned with a concentric metal pad that features improved resonance, compact size, and flexibility to conform to the curved surface of the fruit. The sensing mechanism is to detect electromagnetic resonance that is susceptible to dielectric property changes by water content variations. The robust resonance provides electric fields that penetrate deeper into the fruit tissues, compared to an untuned one, with a sufficient spectral resolution to reach high sensitivity. Experiments were conducted, including long-term continuous water content monitoring and total water content measurements. The sensors demonstrated clear frequency shifting trends when fresh apples became dehydrated, and their initial resonant frequencies indicated total water contents. Simulations were conducted to examine measurement discrepancies induced by inhomogeneous water evaporation and surface curvatures. The feasibility of sensing the watercore defects inside apples was demonstrated with simulations. Additionally, the sensor was used to demonstrate the feasibility of measuring water content in potatoes. The promising results show the great potential of the noninvasive and continuous water-content sensor applications in agriculture to study the growth, maturity, anomaly, and storage of fruits and in food processing applications to achieve optimal quality.
... Potato tubers usually lose part of their characteristics during the storage period, by moisture loss and pests [7]. The loss of tuber moisture leads to a decrease in its weight, so it is always recommended that the moisture in the store not be less than 85% [8]. The percentage of moisture loss increases in the feathery tubers whose crust formation is not completed as a result of not performing the drying treatment process [9]. ...
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Severe climatic changes led to the spread of pathogens, which made the global food security problem, and agricultural crops are damaged by fungi. In the current study, the novelty was the synthesis of bimetallic zinc oxide-copper oxide nanoparticles (ZnO-CuO NPs) by gamma rays and Gum Arabic for controlling potato post-harvest tuber rots as safe, and new protectant. High-resolution transmission electron microscope (HR-TEM) indicated that, ZnO-CuO NPs were semi-spherical and their sizes ranged from 8.5 nm to 70.0 nm, with an average diameter of 22.27 ± 1.6 nm. ZnO-CuO NPs displayed a fungicidal effect against Alternaria solani (A. solani) when used at levels greater than 31.25 µg/mL. When tubers were treated with ZnO-CuO NPs and infected with A. solani, it was demonstrated that they function as a coating layer on the surface of the tubers. As a consequence, there was no rot that could be seen for up to 21 days. Infected tubers lost the most weight (57.03%) after 21 days of storage, followed by infected tubers treated with ZnO-CuO NPs by 10.29%, uninfected tubers treated with ZnO-CuO NPs (2.35%), and uninfected tubers treated with ZnO-CuO NPs coming in third (0.36%). Intriguingly, at 21 days, treated infected tubers showed a substantial decline in α-amylase and cellulase (0.1618, and 0.230 U ml⁻¹, respectively). In addition, the healthy untreated tubers had levels of α-amylase and cellulase that were significantly lower than those of the uninfected tubers treated one at 21 days, reaching 0.124 U ml⁻¹ and 0.144 U ml⁻¹, respectively. The present method appears to be original in its use of disease prevention for potato tubers as a practical strategy for maintaining quality and extending storage shelf life.
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In this study conducted in 2022 year under the ecological conditions of Konya, five registered potato varieties (Innovator, Russet Burbank, Metro, Brooke, Lady Olympia) were cultivated, and certain physical and technological characteristics were examined before and after a six-month long storage period at conditions of 4-6 °C and 90-98% humidity. These characteristics, including dry matter content, chips yield, French fries yield, and the color values of chips after frying (L*, a*, b*) were assessed both before and after storage, and weight losses at the end of storage were also recorded. At the end of the storage period, there were variations in the physical and technological characteristics of the tubers. According to the overall average of the potato varieties, by the end of storage compared to before storage, the dry matter content of potato tubers increased by 2.72%, chip yield by 0.48%, French fries yield by 5.09%, and the a* value by 55.37%. On the other hand, the L* value decreased by 8.39%, the b* value by 28.17%, and the weight loss during storage showed a decrease of 4.61%. In terms of industrial type, based on dry matter content, the varieties Brooke and Innovator had the highest values. Excluding the Melody variety, all other varieties showed high yields in chips and French fries production. The variety with the least weight loss detected was the Innovator.
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Carotenoids are secondary metabolites that are synthesized and stored in all types of plant plastids. These pigments play a significant role in protection against oxidative stress, as well as in the color of flowers and sink organs. Tubers of potato Solanum tuberosum L. synthesize carotenoids, including during post-harvest storage. The state of physiological dormancy and cold stress response are controlled, among other things, by abscisic acid (ABA), which is an apocarotenoid. In this study, we analyzed the expression of carotenoid biogenesis pathway genes (PSY1, PSY2, PSY3, PDS, ZDS, Z-ISO, CRTISO, LCYB1, LCYB2, LCYE, VDE, ZEP, NSY, NCED1, NCED2, and NCED6), as well as genes putatively involved in initiation of chromoplast differentiation (OR1 and OR2), in the dynamics of long-term cold storage (September, February, April) of tubers of potato cultivars Barin, Utro, Krasavchik, Sevemoe siyanie and Nadezhda. It was shown that OR1, and OR2 mRNAs are present in tubers of all cultivars at all stages of storage. The expression profile of all analyzed carotenoid biosynthesis genes during tuber storage was characterized by a significant decrease in transcript levels in February compared to September, with some exceptions. In the period from February to April, the level of gene transcripts changed insignificantly. The biochemical analysis of the carotenoid content in the dynamics of cold storage showed that at the time of harvesting, the highest carotenoid content was in tubers of the cv. Utro; tubers of other cultivars were characterized by a similar amount of carotenoids. During storage from September to April, the total carotenoids changed in a genotype-dependent manner without any trend common to all cultivars.
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Measurements of pressures on the walls of reinforced concrete bins 122 m long and 18 m wide from potatoes piled 6. 1 m deep show actual pressures up to 50% greater than previous studies indicate. The paper discusses how the experiments were conducted, measuring instruments, pressure measurements and results.
Chapter
Whether or not to store potatoes and how to store them are commercial decisions which must depend upon the circumstances of the individual case. The technicalities of storage should never be considered in isolation. The influence of many storage variables upon the quality of stored potatoes and upon storage losses can be found in the following pages. On the basis of this information technically optimal methods of storage might be suggested.
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The air pressures required to ventilate small stacks of potatoes, red beet, onions and carrots at velocities between 0·04 and 0·3 m/s were determined. The velocity of the ventilating air was measured at the surface of the stack by an instrument designed for the purpose. The effects of depth and increasing air velocity are discussed together with the effects of soil or trash in the sample.
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The Alternative Fluorocarbon Environmental Acceptability Study (AFEAS), a consortium of fluorocarbon manufacturers, and the U.S. Department of Energy (DOE) are collaborating on a project to evaluate the energy use and global warming impacts of CFC alternatives. The goal of this project is to identify technologies that could replace the use of CFC's in refrigeration, heating, and air-conditioning equipment; to evaluate the direct impacts of chemical emissions on global warming; and to compile accurate estimates of energy use and indirect CO2 emissions of substitute technologies. The first phase of this work focused on alternatives that could be commercialized before the year 2000. The second phase of the project is examining not-in-kind and next-generation technologies that could be developed to replace CFC's, HCFC's, and HFC's over a longer period. As part of this effort, Oak Ridge National Laboratory held a workshop on June 23-25, 1993. The preliminary agenda covered a broad range of alternative technologies and at least one speaker was invited to make a brief presentation at the workshop on each technology. Some of the invited speakers were unable to participate, and in a few cases other experts could not be identified. As a result, those technologies were not represented at the workshop. Each speaker was asked to prepare a five to seven page paper addressing six key issues concerning the technology he/she is developing. These points are listed in the sidebar. Each expert also spoke for 20 to 25 minutes at the workshop and answered questions from the other participants concerning the presentation and area of expertise. The primary goal of the presentations and discussions was to identify the developmental state of the technology and to obtain comparable data on system efficiencies.