European Apple Warehouse Practices
This is a time of change for the Washington apple industry. There is more competition on a worldwide basis for a share of the apple market, and Washington producers are faced with the challenge of handling new varieties that are multicolored and bruised easily.
This is a report of a tour taken in November 1990 by Gaylord Enbom, Les Green, Fred Valentine and me to help address such concerns. The tour was partially funded by the Postharvest Education Fund of the Washington State Horticultural Association. Additional funds came from Wells and Wade Fruit Company, George Joseph Orchard Siding Company, the Tree Fruit Research Commission and Blue Star Growers. We appreciate the opportunity to have participated.
The specific goals of the tour were to:
- Evaluate equipment and commercial packing of apples and pears,
- Visit commercial CA storages and study their technology,
- Evaluate postharvest chemical use,
- Determine types of packages and fruit quality,
- Obtain information on harvest maturity, storage and handling of varieties new to Washington,
- Discuss current research with European postharvest scientists and make recommendations for postharvest research and industry changes.
We traveled in Europe from November 3-20, 1990, to visit:
- Offenburg and Bavendorf in Germany (southwestern Germany)
- South Tyrol in Italy (northeastern Italy)
- Digne, Avignon, Toulouse region, Bergerac, Brive
and Angers in France
- Geldermalsen in Holland
- Copenhagen in Denmark.
We inquired about the cost of electricity and were told that $0.20 per kwh is the average in many countries. This high cost of energy promotes conservation systems in warehousing and storage.
In each location we were received with great friendliness and found that we had much in common with our European counterparts. Chemicals, bruising, color sorting and new varieties are challenges the fruit industry of Europe shares with our industry. We thank all of those we visited for their hospitality.
Lessons for Washington State
Recommendations for Research
Washington researchers need to determine how to:
- Predict the risk of scald on a particular lot of fruit; reduce storage scald through nonchemical and alternative chemical means and determine how to apply DPA without unused chemical waste.
- Best measure humidity: what the humidity should be
and how it can be raised in a closed CA room.
- Optimize quality (especially flavor) of fruit stored
in CA. Investigate stepwise pulldown and the effect of
increasing the oxygen content in CA rooms as opening day
- Optimize the flavor of Washington apples. Determine
the effect of our postharvest practices on flavor.
- Evaluate the risk from diseases and disorders for each lot harvested so that chemical treatment of only certain lots is necessary. Reduce chemical use through nonchemical and alternative chemical control methods.
Lessons for Washington Industry
- Most of the warehouses visited were tight-filling
CA rooms. Tight- filling is the process of stacking rows of
bins close together, minimizing air movement along the side
of the bins but increasing the air flow over the tops of
bins. Curtains are used to prevent short circuiting of the
cold air across the tops of the upper bins.
- Most of the warehouses visited store their Golden
Delicious at 2-3% CO2, which is higher than in
most Washington CA rooms. Temperatures are also held higher
than in Washington (34°F vs 32°F). Adopting this
technology will save energy and reduce costs.
- European warehouses find markets for slightly
blemished fruit or soft fruit. In our opinion, we throw
away too much fruit--it's just a matter of finding the
right market for it.
- Certain European packers have packages with more
uniform fruit. The French and Dutch use a great deal of
hand labor to select fruit with similar appearance for each
layer of each box. The Dutch are making great strides in
having the entire industry pack to exactly the same
standards even though the growers and their families do
most of the packing.
- Many types of packages are used in Europe, 20-kg tray
pack, bags, one- and two-layer panapaks, overwraps, etc.,
since the consumer is willing to pay for this extra
- European warehouses that store most of their fruit in CA report increased consumer acceptance, since even short-term CA is superior to regular storage in retaining quality.
Apple Varieties and Harvest Maturity
Table 1. Apple production in EC countries (1989).
|Variety||Volume (1,000 MT)||% of Total|
"Quality" is defined differently in each country. There are two major schools of thought. The first is that fruit can have a rough look with lots of imperfections, russeting, etc., so long as it tastes good. Firmness and appearance are minor considerations. Although the apple must not be mealy, it can be soft. Visually perfect apples are rejected as being too artificial. These people often do not like Red Delicious but prefer Goldens, Grannies and tart apples. This philosophy is held by many of the Germanic peoples.
The second group of people prefers a crisp, hard apple with great visual appeal. Red Delicious is a very desirable apple for them. Red Delicious is increasing in popularity in the UK, Scandinavia and Italy.
In a discussion of apple maturity and fruit quality, scientists Josef Streif and Helmut Bohling (Germany) point out the difference between quality factors and ripening factors. They consider quality factors those that describe the inherent features of the apple such as size, calyx width, acidity and soluble solids. Ripening factors include ethylene, starch, firmness and ground color. Ripening factors are used to determine harvest date, not quality factors.
Here is a summary of comments on harvest maturity: Varieties such as Jonagold, Elstar, Gala and Gloster require several pickings. Jonagold trees may need to be picked four times and harvest may extend 3-4 weeks. Jonagold appears to be susceptible to both Bitterpit and Jonathan Spot. Not much is known about the harvest maturity of Fuji or Braeburn since plantings are still young.
Goldens are picked two or three times in some areas. In Germany, the first picked Goldens are placed in regular storage to develop aroma and flavor before sale in the fall. It is their opinion that fruit picked too early (preclimacteric) will not ripen with good flavor following CA. Fruit from the middle harvest is placed in long-term CA storage since it has already begun to develop flavor. Fruit from the end of harvest is sold immediately since it will not store well.
Streif described that a compromise between high yield, fruit taste and how well it will store is achieved by computing a harvest index. This is done using the following formula:
Firmness/(Soluble Solids · Starch)
where Firmness is measured in kg; Soluble Soilds as %; and Starch on a scale from 1 to 10.
Streif pointed out that in cooler microclimates apples are longer with lower soluble solids. In warmer climates fruit is rounder and develops more soluble solids. He also found a good correlation between the space between the calyx lobes and the amount of soluble solids in the fruit.
Growers are required to bring into the warehouse clean fruit of marketable quality. This makes postharvest disease control and cullage easier.
Controlled Atmosphere Storage
Most of the CA facilities we saw were excellent. However, one major French packinghouse still allows the fruit to respire its way to CA conditions. In contrast, the next warehouse visited that day had modern equipment for the establishment of rapid CA.
Apple Varieties and Storage Regimes
Rapid CA and low oxygen CA are used by progressive European warehouses. Commercial storage operators hold oxygen levels at 1% (ULO) for Goldens and Jonagold. Operators have found that fruit rotting has decreased and fruit quality increased as ULO has been adopted.
Carlo Nardin (Italy) recommends a stepwise pulldown consisting of rapid pulldown to 4-5% O2, followed by the fruit pulling the oxygen down to 2% where it is held for several days and then brought down to 1%.
Helmut Bohling (Germany) studied the relative effectiveness of lower oxygen levels, lower temperatures or higher carbon dioxide levels in governing the respiration rate of apples in CA (Table 2). Oxygen is the preferred method of controlling respiration since it is the most effective in retaining firmness, preserving green color and acidity. Flavor and aroma are retained as long as the oxygen is held above 1% and the maturity is correct.
Table 2. The rate of respiration when temperatures, oxygen, or carbon dioxide are reduced (Source: Streif).
|Temperature °C||Atmosphere||% Respiration1|
1Rate of respiration is a % of the rate of respiration in air at 12°C.
High CO2 application (12-15%) at harvest can be used when adequate cooling or oxygen reduction is not immediately available to obtain rapid CA. It will improve quality above that of air storage, but it is not superior to well-refrigerated ULO-stored fruit.
The effect of ULO (3% CO2, 1% O2) was compared with regular CA storage (3% CO2, 3% O2). Firmness, green skin color and acidity were higher in ULO than in CA. However, aroma was higher in the fruit out of CA than out of ULO.
The removal of ethylene in either CA or ULO has virtually no effect on the retention of aroma if the fruit is climacteric. Preclimacteric fruit retain aroma better in regular storage if ethylene is removed, but it has no effect in CA.
Jonagold is sensitive to senescent breakdown, skin browning and low temperature breakdown (mature fruits) in storage. In CA, the carbon dioxide can rise as high as 6% without bad effects. Nardin reported that Jonagold is susceptible to scald in storage after 9 months. To avoid unequal maturity, selective picking is necessary.
Fuji will store for seven months in regular storage. It may be too sweet and lack acidity, so the flavor will not appeal to certain people. Fuji must be held below 2.5% CO2, since burn can result at higher levels. Fuji may be susceptible to storage scald.
Gala can be stored for five to six months in regular storage. It has low acidity and may be sensitive to CO2 in CA. If the humidity is held above 92%, the fruit may crack.
It is acceptable to store Jonagold, Gloster and Goldens in the same room under the same CA conditions. However, Boskoop, Cox and Elstar should each be stored separately.
Relative Humidity in CA Storages
Humidity in the CA room is being studied by Nardin (Italy) who found that by adjusting humidity so Goldens lose 3% of their weight in storage, the fruit can be packed without bruising. Streif (Germany) reported that fruit that had 3% moisture loss in storage had less storage scald and core flush.
French storage operators measure moisture loss in each room by having the condensate drainage tube feed into a barrel in the hall outside the room. Dutch CA operators measure relative humidity by weighing the condensate water as it exits the room.
Nardin reported that humidification is especially important immediately after harvest. Saturating wooden bins with water can reduce moisture pulled out of the fruit by the refrigeration system. A loss of 3% regardless of the length of storage is ideal for Golden Delicious. Methods of managing the humidity in CA include:
a) Fan cycling-fans are run 4 hours per day whether or not refrigerant is called for. Storage temperatures are above 0°C and the heat generated by the fans alone can defrost the coils so defrosts are minimized. Defrosting is only on demand.
b) Methods of adding moisture to a CA room include using nozzles delivering water in front of the fan when the fans are on. The nozzles are 1 mm in diameter operating at a pressure of 10-15 bars and located 1.5 m in front of the fans. These nozzles deliver 20-25 liters/hour. Nardin found that 0.8 min diameter nozzles clog easily. Aeration of the water in the nozzle can help reduce clogging. This system uses 1 bar of water pressure in the line for air to atomize the water. The "Defensor" system, made in Switzerland, uses a rotor that sucks up the water which mechanically breaks up the droplets.
c) Many CA rooms are closed with water on the floor to increase humidity.
Oxygen Reduction Equipment
Oxygen reduction equipment is similar to that used by Washington storage operators. A number of sheds rely upon propane or natural gas catalytic burners. New installations are using PSA or membrane gas separators while a few have installed ammonia-separating equipment. One shed still depends on the fruit to reduce the oxygen. The vast majority of installations had first-rate equipment.
A storage firm in Holland has three types of oxygen reduction equipment in the same installation. When asked for a comparison of the three, we were given the following information:
Oxydrain--Difficult for a new person to run. Uses water, energy and ammonia, and ethylene is present. Often used in a recirculating mode. Ammonia is not looked upon favorably and can be dangerous. Of the three, the Oxydrain has the lowest capitalization cost but the highest cost for use.
Membrane--Highest capitalization cost of the three, but equal in running cost to the PSA. Used with fresh air, thus very low ethylene levels, and easy for a new person to run since the equipment involves few moving parts. However, the membrane will eventually need replacement and this is about 70% of the cost of the entire machine. Life expectancy of the membrane is unknown.
Pressure Swing Adsorption (PSA)--Lowest capitalization cost and equal in running cost to the membrane system. Uses fresh air, thus low ethylene levels. Easy for a new person to use, but employs several valves. This is currently their choice since the cost of replacing the carbon-adsorbing beads or valves is relatively inexpensive.
Carbon Dioxide Scrubbing
Carbon dioxide scrubbing methods are similar to those used in Washington, except that MSA systems are not used due to high energy cost. Most sheds used either lime or carbon scrubbers.
In the past, carbon scrubbers allowed oxygen into the room. Newer carbon scrubbers use a balloon or bag to store low oxygen, low carbon dioxide air which is used to purge carbon beds after regeneration. An alternative method of avoiding the entry of oxygen into the room is to flush the scrubber bed with pure nitrogen after it has been purged. Thus it is possible to maintain 1% oxygen using a carbon scrubber.
Most European storages store Golden Delicious at 2-3% carbon dioxide with oxygen levels at 1-1.5%. Therefore, it is not necessary for the operator to keep the carbon dioxide at very low levels.
Pressure relief is provided by a balloon or bag with the capacity of 1.5% of the total volume of the room. The bag is hung in the attic and when a high pressure weather system is present the bag inflates with room air (of low oxygen). When the pressure system passes, low oxygen air is pushed back into the room.
We saw very few ammonia systems since Europeans think that it is unsafe for both people and apples.
Most of the systems we saw were either direct Freon or glycol. Glycol is preferred to Freon in rooms with Golden Delicious since the glycol system results in a lower temperature difference (TD) than Freon systems. However, glycol is more expensive than Freon to install.
Energy conservation is practiced in most CA storages by reducing the fan speed by half or cycling the fans. In one case, the fans ran at half speed 20 hours per day. In most of the rest, the fans were off for a longer period of time-as long as 20 hours per day.
Defrosting is done as little as possible. Since the Europeans store fruit at 34°F and above, defrosting is not often necessary. One warehouse mentioned that they defrost once every four weeks.
Building and Room Construction
We did not see any tilt-up concrete buildings. Both storages and packinghouses are housed in buildings made of panels. CA storage buildings are made of metal and polyurethane sandwich panels about 10 cm thick using plastic strips with acrylic resin along the vertical edges to make them airtight. The panels are about 7.5 m tall and 2.10 m wide.
In most storage rooms, bins are loaded so each stack of bins touches every other stack. In these tightly filled rooms cooling is accomplished by careful alignment of the bins so that the runners go in the same direction. Nardin reported that evaporators should cover 60% of the wall space across the top of the room. The room should be filled with about 250-260 kg of fruit/cubic meter of space. Tight filled rooms have 40 cm of space along the back wall and 50 cm space under the evaporators. Along the side, the air space should be 20-25 cm.
Clear plastic curtains surround the evaporators to prevent short circuiting of the air across the tops of the bins. There is a sheet of poly in front of the fans to direct the air toward the back of the room. There are two fewer bins in each stack by the door and one less bin in the next stack. The poly sheet is slanted upward over the first two rows of bins to decrease the available space for air flow to discourage short circuiting. Placement of an additional rigid poly sheet at the top rear of the room rounds out the back where the ceiling meets the wall. An additional sheet of poly is draped between the evaporators and between the evaporators and the side walls.
In Italy, they use plastic bins that lock together vertically. These provide good air and liquid drainage and are easily cleaned. They are reusable and easily replaced. The manufacturer will return two new bins for three broken bins since the plastic can be reused. The cost of the plastic bins was $65 as compared with wooden bins which cost $45. Plastic bins weigh 32 kg while wooden bins weigh 55 kg. Plastic is stronger than wood and harbors fewer decay organisms.
In ULO, scald is suppressed during storage but develops during the shelf life. Streif found that warming the fruit for 24 hours to 70°F and ventilating it for 24 hours after one and two months in CA has reduced scald. However, firmness decreased.
Martin Nichler (Italy) reported that applying DPA as a fog directly into a CA room gives an acceptable level of control of storage scald in varieties that have low potential for scald. Varieties with strong scald potential may still develop scald. The technique of applying the DPA needs work since it is possible to achieve excessively high residues as a result of uneven application. It has not been used in very large CA rooms. Nardin reported that the DPA thermofogger can be used only if air circulation is good during application. Low pressure fans are used to distribute the DPA. High pressure fans should not be used when thermofogging. The room needs to be small and four-way entry bins must be used. The DPA residue may deplete rapidly and refogging may be necessary. Thermofogging of DPA has not been attempted under Washington conditions.
European packinglines range from very modern lines to hand packing. Labor is extremely expensive in most of Europe, forcing the managers to turn to robotics. Robots were most often used to take full bins off the end of the presizer and stack them according to fruit size and grade. They were also used to dump fruit onto packinglines. For example, on one line a robot alternately dumped three types (grades or varieties) of apples into one bin dumper which served three packinglines. A robot was used to automatically choose which bin to take from three separate stacks of bins brought over by the forklift driver.
2. Automatic box filler
In France we saw an automatic box filler that placed filled trays into boxes, although the orientation of the fruit on the tray was done by hand. The machine slid the tray along until it was over the box, at which point a trap door under the tray opened and the tray was lowered into the box. Bruising was avoided by rods that came up through holes in the bottom of the box to support the tray. The rods lowered the trays into the box. The box automatically moved down the line when full. Tray fill operations in most of the packinghouses used the same systems we use in Washington.
Palletization equipment ranged from worker-assist to fully automatic. The fully automatic systems oriented boxes via an elevated feeding system. The pallet itself did not rise. One system accumulated enough boxes for a complete pallet before feeding them into the palletizer. It was possible for three different sizes or grades of fruit to be accumulated at the same time without tying up the palletizer itself.
Worker-assist systems passed boxes to a worker who slid the box on rollers into position. When a layer was arranged the worker pushed a button and the whole layer was added to the pallet. The worker was standing on a platform which rose so the boxes were always at chest height and no lifting was required.
Full pallets were netted before shipping. Shipping was done on slotted wooden pallets.
4. Bin transportation
In many warehouses, bins were transported on little carts pulled by a tractor. This allowed one driver to haul many bins, as these "trains" could be up to ten carts long. Thus, forklift drivers were more stationary and did not haul bins any distance.
1. Presize vs direct pack
Most of the European packinghouses presized Goldens on equipment familiar to the Washington industry. One packinghouse claims to presize all fruit before storage. The presize operations were mainly using water dumps, flumes and water bin fillers. We did see a few dry dumps.
We saw an interesting method for checking the weight of fruit going into a flume. An automatic weighing device was placed in a flume that accumulated, then weighed 25 apples. This helped assure uniformity of size of fruit going into each lane.
2. Packingline size
In contrast to Washington, many European sheds use a number of smaller packinglines, rather than one or two high-volume lines. They presize fruit on one large line, but packing is done on two to four smaller lines. This allows the packing of multiple varieties or types of packs at the same time. It also may reduce the total building volume.
The negative side of having three to four packinglines was that in some cases total fruit volume was reduced since some of the lines were committed to a single type of pack (tray filler, bagger or overwrap, etc.).
Red Delicious apples are waxed in Europe, but they are not the mainstay of the industry and, where wax was used, the results were not up to Washington standards. The number of brushes was less and the dryer was shorter--apparently consumers accept less shiny fruit. Since most of the fruit was not waxed it could be transported in water, thus the packinglines were shorter and more compact.
Bruising During Packing
New packinglines greatly reduce bruising by using devices that help the fruit change direction or drop from one level to another. Again, our impression was that their consumers were willing to accept more bruising and softer fruit.
One type of device is a horizontal roller with very long, flexible, but rigid brushes (MAF, AWETA and STRAPAK). The apples fall into the brushes and are carried to the next belt as the brush turns. One drawback is that the brushes need to be cleaned as apple wax accumulates on the hairs. Brushes were also used to cushion the fall of the fruit into water flumes.
A second device is a fabric flap that travels along underneath the sizer cups (GREEFA, GORIN). Each cup has a separate flap; when the cup releases the fruit, the flap lowers it to the belt below. The flaps need replacement regularly as they travel along with the cups.
Astroturf is used to help pad the drops on a third system. It does not seem to provide as soft a landing as the other systems.
Much of the lower grade fruit is sold in wooden boxes which are jumble filled by a system of slowly lowering box holders. Once filled, the box is removed by hand.
In addition to tray packing, a significant amount of high quality apples is hand packed into one- or two-layer panapaks to prevent bruising and to orient the fruit for best eye appeal.
In presize lines, both dry and water bin fillers are used extensively. One system of water bin filling involved swirling the fruit into the bin from the surface of the water. We are not sure if this system would reduce bruising over our current system.
One warehouse passes Golden Delicious apples through a hot air dryer (150°F) for a very short time which they claim reduces packing bruises.
The grade regulations in Europe appeared to be more tolerant of defects. However, the lines seem to be more gentle and the fruit did not get as bruised as fruit does with many of Washington's presize lines.
We were impressed with the flexibility of many of the lines. Presize lines were built with the possibility of either refilling into bins or packing directly off the presizer.
One packingline used one bin dumper that fed into three separate packinglines. The system could be programmed to feed an equal number of fruit into all three lines or to put more fruit into one line. This way up to three varieties (grade or size) could be packed at the same time or one variety could be packed in volume.
Many of the warehouses were equipped to pack several types of packages including loose fill boxes, trays, bags, overwraps, etc. In some sheds, the same line could be easily switched between types of packs. Other lines were committed to a specific type of pack. A number of times we were told that consumers are willing to pay for a specific type of package. Therefore, the sheds are set up to give consumers what they want.
Belts on the tables were set so that they would move ahead only if they were full of fruit.
Waxing is done on a very limited basis and is not a high priority. Therefore, both the brush roller sections and the dryers were very short and apples were still wet at the wax applicator. The fruit were tacky coming out of the dryers. On the other hand, the short wax section allows more flexibility in line design and more water transport can be used.
Most lines still do considerable hand packing, although semiautomatic equipment is also used. Even in the most automated lines which had robots, bagging and arranging fruit on the trays were still done by hand.
Color Sorting and Sizing
We paid special attention to color sorting and sizing since new varieties of apples are multicolored instead of solid red, yellow or green. We observed four types of color sorters manufactured by MAF, GREEFA, AWETA and OMS.
In all instances, the problem of orientation of the fruit under the color sorter needs to be improved. The typyness of Washington's Red Delicious hinders the color sorting equipment's ability to evaluate color.
Automatic color sorting equipment in many packinghouses appears similar to the mirror and lens technology available in Washington. Most warehouse managers indicated that they were pleased with their ability to sort Golden Delicious. However, the sheds that put up a large number of different types of packs from the same line had many people doing the final sorting and selection for each box.
In a number of sheds, grading is done by having a sorter touch an apple with a wand that transmits a signal to an overhead camera. The apples are turned by rollers and sorters are assigned one, two or three lanes. It appeared difficult for the sorters to concentrate on the apples for very long and their eyes wander off the table. Therefore, it is important to rotate jobs frequently to get consistent quality. Managers of most of the packinglines that used this equipment stated that they had to slow down their equipment in order to make the wand system sort effectively. In addition, this method allows each apple to be examined by only one sorter.
We observed a volumetric sizer and color sorter developed in California which uses video cameras to determine the size and color of each apple. It does not use weight sizing, instead volume is determined by three cameras positioned at different angles above the fruit. Technicians working for the company told us that the software can be modified to screen for three colors if desired. We saw it used on Golden Delicious, and the user indicated that this sizing method is more rapid than weight sizing.
One of the most intriguing systems we saw has been developed in Holland by a company that has experience with grading tomatoes and eggs, as well as apples. They developed a video system that looks at one revolution of the apple and can read the amount of red, green and yellow color very effectively. It can also evaluate large areas of russet. The color sorter can be reprogrammed either by using computer commands or by passing ten apples under the sorter. The computer picks up the colors on the apples and the operator can fine tune it as needed. This system is not yet available in the U.S. but has been used in Europe for over a year. Operators we spoke with said that it is very versatile and reliable. One camera worked three lanes of fruit at the same time. The machine is capable of sorting seven apples per lane each second or 140 rods per minute. They use a weight sizer.
A French-based organization is devoting a great deal of time and effort to developing a laser technology to see not only color but bitter pit, russeting, bruising and size. This appears to be several years from commercial production.
Types of Packages
We were impressed by the number of types of packages in the European marketplace. One packinghouse that emphasizes differences in fruit appearance and quality puts up 130 different types of packs from five or six varieties of apples. Their premium pack was absolutely beautiful and all packs were extremely uniform. However, they admitted that packed fruit inventory control was a challenge.
The uniformity of the fruit in the pack was often better than what we usually see in Washington. In Europe, as in the U.S., the number of buyers is shrinking (Table 3).
Table 3. Where Euopean consumers purchase fruit (1989).
It is obvious that the green grocer and farmers' markets are giving way to larger and larger supermarkets. Holland is addressing this issue by enforcing strict regulations about the appearance of fruit in the box. They are working toward total electronic selling in which the buyer in his office anywhere in Europe can see a list of the fruit available that day and purchase it via computer. In order to do this they have created nine subcategories for Class I fruit.
1. Bags--In most packinghouses fruit of medium to lesser quality is bagged. Automatic baggers were often used. Bags are stronger than our bags and have handles molded into the bag. The better automatic baggers weigh 16-20 individual fruit and select the one closest to the weight needed to fill the bag. To reduce bruising, the baggers have a platform that supports the bag as it is filled. The empty plastic bags are delivered to the bagging machine on a roll.
2. Overwrap--Packinghouses place fruit in trays and overwrap four, six or eight apples per tray with clear poly. They orient the fruit by hand and apply a sticker which gives store name and logo, variety, weight and even price. In some cases, single layer boxes were overwrapped.
3. Loosefill boxes--Wooden boxes or cartons are used for lesser quality fruit bound for very local markets. They are filled automatically (described above) and then palletized.
4. Tray filled boxes--10 kg carton boxes, very similar to those used in Washington, with fiber or plastic foam trays are used extensively. Most sheds use hand labor to orient the fruit and use either hand or automatic tray feeding equipment. In some cases, the top layer of fruit is hand wrapped with colorful paper.
5. Layer boxes--These premium packs are hand packed into one- or two-layer panapaks. The blush side of the fruit is often up.
6. Modified atmosphere packaging (MAP)--Although we were told that they were used, we failed to see any type of MAP/CAP containers. Dr. Chambroy (France) reported that the major effect of modified atmosphere packaging is the reduction of fungal decay. This nonchemical method of decay reduction is becoming increasingly important due to laws against postharvest chemical use. There has been an increasing use of MAP on salad products and other vegetables. These rely upon 40 micron co-extruded OPP which extends shelf life six to ten days. The atmosphere should be 5% CO2 in air (16% O2) or 5% CO2 with 5% O2. The benefits (especially in mold and decay control) are improved when the atmosphere is enriched with high CO2 at the time of packaging. The company Courtaulds manufactures the MAP films.
Postharvest Chemical Use
European consumers appear to be greatly concerned about pesticide residues on their food. Formerly pesticide abuses were common among producers using unlabeled compounds or above label rates. However, regulations are being vigorously enforced with large penalties levied on offenders. As a result, an integrated management (IM) program has been developed for apples, and committees working on EC policies have incorporated much of the IM philosophy into proposed regulations governing pesticide use for all EC apple producers. It appears that this program is being imposed on the European fruit industry untested concerning its ability to control pests and diseases, especially in postharvest.
Integrated management is not synonymous with organic production since IM permits the use of "safe" synthetic pesticides. The term "safe" means that the pesticide is not injurious to beneficial insects, the soil, the atmosphere or the applicator. IM-produced fruit is identified in the supermarkets and consumers like it.
Pesticides are coded as red, yellow or green based on their safety. IM growers are permitted to use green pesticides as needed. Yellow pesticides are used only on very severe problems, while the use of red pesticides kicks that orchard out of the IM program. We have obtained the current list of these pesticides and will make it available to anyone wishing to see it. It is likely that Washington producers wishing to sell fruit to Europe will be forced to conform to these regulations.
Insecticide use in northern Italy has declined as growers use the IM program. Many of the sprays formerly controlled spider mites which are now controlled using the IM program which encourages natural predators. However, due to frequent rains during the growing season, growers are forced to repeatedly spray fungicides for apple scab. This has not yet been reduced by IM.
Prestorage Fruit Treatments
Fruit is usually placed into storage without any postharvest chemical treatment. Growers use fungicides in the orchards right up to harvest. One research report states: "To avoid fungal defects during storage, trees are intensively sprayed with fungicides before harvesting the fruits." Adoption of IM postharvest strategies is not uniform among European storage operators in different countries.
In France, Red Delicious and Granny Smith are treated with Benlate or TBZ and DPA prior to storage since scald is a serious problem. One packinghouse applied DPA without any fungicide to Red Delicious and Granny Smith for the first time this year. They hoped that by changing the DPA solution every four hours decay would be held at manageable levels.
Producers are fearful that when DPA is no longer permitted it will mean that scald-susceptible varieties can no longer be placed in long-term storage. There are a number of research projects looking into alternative methods to control scald.
Nichler reported that core rotting has become a serious problem in certain warehouses. It is thought that Alternaria, Fusarium or Botrytis enters the fruit at flowering. However, the decay seems to be associated with postharvest drenching. Studies at the University of Bologna have shown that spores resistant to Benlate are also resistant to thiabendazole (TBZ-Mertect, Deccosalt 19).
Packingline Water Treatments
We did not see treatment to control the buildup of spores in water and the water used to float apples was often dirty. Packingline managers change the water in the flumes as often as possible, usually every four to five days. However, chlorine is not permitted, and ozone and chlorine dioxide are not used. In one packinghouse we saw empty bins cleaned with a quaternary ammonia compound spray.
Packingline Fruit Treatments
Most varieties of apples have had no postharvest chemical treatment after storage. Red Delicious is waxed, but no fungicide is applied. It is important to realize that, with the exception of fruit being exported to the Middle Eastern countries, most of the fruit is only one to two days from market.
A Final Comment
Just as Washington producers have learned a great deal about growing apples (Axis, Slender Spindle, etc.) from Europe, we stand to profit from dialogue with the European storage industry and researchers. We were delighted to participate in this tour and hope that more of the Washington postharvest industry take the opportunity to investigate what their counterparts in other fruit growing regions are doing. If you have questions about what we have learned, contact any of us and we will be glad to share our experiences.
Dr. Eugene Kupferman, Postharvest Specialist
WSU Tree Fruit Research and Extension Center
1100 N. Western Ave., Wenatchee, WA 98801
Tree Fruit Postharvest Journal 2(3):3-15