Document Gm6B4xgDVxjXwdy4kZXyYOkjm

498 CHAPTER 47 mended storage temperature as soon as posable. Since modifi cation of the atmospheric composition.is not possible.until .the room is filled and sealed, it is desirable that any one room be filled within a few days, if the greatest benefit is to be obtained. Once the room is sealed, the oxygen content of the atmosphere will be reduced by fruit respiration, and theCOi content con trolled by scrubbing. Usually a lye solution is used during the initial period, but water scrubbing is feasible thereafter. Some times flushing with nitrogen is used as an initial ir*ng of lowering the 0% content to about 10 percent. Table 3 indicates approximate temperature and atmospheric requirements for controlled atmosphere storage of several varieties. Since these may vary from region to'region, more precise requirements should be determined from authorities within a region. Table 3 .... Requirements for Controlled Atmosphere Storage of Apples Variety McIntosh Delicious and Golden Delicious Baldwin, Jonathan, Rome Beauty, Stayman Winesap Yellow Newtown %co, 2-5 1.6-3 1-5 6-8 %o, 2-3 2.6-3 2-3 2-3 38 30-32 30-32 38-40 Apples packed in boxes with polyethylene liners hp1pH after packing have been used as a means ofcreating a modified atmo sphere. In many instances, it is possible to closely approach the atmospheric composition of a controlled atmosphere room, be causeof differential permeability of the film to 0,and CO*. Un fortunately, great variability exists in the composition of the atmospheres in different containers, so that no dependence can be placed on improved storage life. Also when the apples are marketed, the fihn finer must be opened in some way to avoid possible harmful effects of low Ot or high CO\ as the tempera ture rises. Although film liners seem impractical as a means of altering atmospheric 0* and CO% unsealed film liners have proven very helpful in controlling excessive moisture loss from varieties such as Golden Delicious. Dessication, although often severe in cold storage warehouses, should not be of sufficient concern to justify film liners for fruit in controlled atmosphere rooms. Storage Disorders Storage troubles of apples may be caused either-by invasion by microorganismsorby the fruit'sownphysiological processes. Rots caused primarily by fungi are covered in Chapter 51. Physiological disorders although sometimes resembling rots are related to biochemical processes within the fruit that are not understood. Susceptibility to such disorders is often a variety characteristic, but may be influenced by cultural and climatic factors and storage temperature. Only the most important storage disorders mil be discussed here. For further informa tion, see Chapter 51. Scald is the most serious disorder affecting apples in storage. It first appears as traces of light mottling on the greener sur faces of the fruit. Darkening becomes more severe with elapsed time and will extend to red cobred surfaces. Ordinarily, scald affects only the akin, but in severe cases may extend into the flesh. It develops rapidly at warm temperatures so that apples 1962 Guide And Data Book with fight scald in storage may be severely scalded durin* marketing. Fruits harvested in the early mature stage are more suscenU. ble than those harvested later. Any delay in cooling the faut after harvest will aggravate the problem. Susceptibility vans greatly with variety but most varieties can develop the trouble. Arkansas, Stayman Wines&p, Grimes Golden, Rome Beauty and Rhode Island Greening are especially suscept&fe varieties. Variations in the severity of scald from season to season indicate a strong climatic effect on its development. The problem seems to be associated with volatile organic n^temhi produced by the fruit, but removal of accumulations in the sur rounding atmosphere does not necessarily give control. The use of ventilation, air purification, oiled wraps, or shredded <&] paper have not given the desired control. Experimental results in recent years have shown diphenyl amine to be very effective in controlling apple scald when used as a fruit dip at a concentration of-1000 to 2000 ppm. Repre sentations have been made to the Food and- Drug Admcastra tion petitioning for approval of the use-of this material by the apple industry.. Bitter pit is characterised by small sunken'spots on the fruit surface. They are most prevalent near the blossom end and al though usually near the surface, they may be found deep inthe flesh as well. At first, they show as small water soaked areas that shrink and turn brown as water is lost from them, and end up as brown localised areas of dead tissue. Baldwin, Rhode Island Greening, York Imperial, Yelbw Newtown, Delirious and Gravenstein are some of the varieties most susceptible. The problem is most severe when apples are picked on the im mature ride, and may be worse on light crop years when fruits are of large site. Prompt storage at a low temperature and high relative humidity and early marketing are means of minimizing losses. The cause of bitter pit is not known but recent studies in __ Australia and the United States show a possible connection with calcium and magnesium nutrition. Soft scald is characterized by dark brows blister-like areas al irregular pattern extending over the fruit. In its earliest stages, it may resemble apple scald, but the two seem not related. The affected areas are soft, slightly sunken and well defined. The skin and outer portion of the flesh is involved. Although the exact cause of soft scald is not known, it is known that & combination of circumstances influence its appearance. It b most likely to occur on apples harvested at an advanced stage of maturity and is aggravated by delayed storage and storage at temperatures of 30 to 32 F. If apples are harvested at as early stage of maturity, storage at 30 to 32 F has been suc cessful, but late harvested apples of susceptible varieties may require elevated storage, temperatures of 34 to 36 FJonathan and Rome Beauty are highly susceptible varieties followed .by Cortland, Winter Ra-imna^ Golden Delicious, Northwestern Greening and Wealthy. Internal browning and brown con are two other disorders that are forms of chilling injury. The former is associated with the Yellow Newtown apple grown in the coastal area of California and is characterised by brownish streaks radiating into the flesh from the core. Susceptibility varys' between yeare and orchards. It can be controlled by storage at 40 F, but because of the short storage life at this temperature, a compromise temperature of about 36 F is ordinarily used except in con trolled atmosphere storage. Brown core is found primarily McIntosh apples in the northeastern states, but may also t* found in Rhode Island Greening, Baldwin and others. Its ap pearance and control are similar to that described for internal browning. The best means of control of both disorders is controlled atmosphere storage at 38 to 40 F. %ofage of Apples, Pears, Grapes, and Bananas 499 PEARS 'Although pear production in the United States is less than 94 Dement of that of apples, it is a substantial enterprise, parXofiiriy in the Pacific Coast states where more than 85 percent , the pears are produced. Bartlett is the most important vari- rTfP^inp; the total of Ml others by a wide margin. Other ptfjfic Coast varieties are Hardy, Comice, Anjou, Bose and Winter Nelis. The eastern states are limited in varieties because ^.the severe problem of fire blight and grow primarily the goffer variety. Although most Bartlett and Hardy, and many Winter Nelis, pears are canned, cold storage prior to ripening {or -rning is the usual procedure. A 10-day to 2-week cold storage period of Bartlett pears is commonly used by many efntwT* because it improves the uniformity of ripening. Sub- quantities may also be stored for extended periods approaching maximiup storage life of the variety in order to better utilise processing facilities. Maturity at harvest has a very important bearing upon sub sequentstorage fife, as it does in theapple. However, unlike the apple, pears do not ripen on the tree, nor do most varieties npen at cold storage temperatures. If harvested too early, they aie subject to excessive water loss in storage. If permitted to bynDi* oyer-mature on the tree, their storage life is shortened and they may be highly susceptible to scald and core break down. Flesh firmness as measured by a pressure tester is perbsps.the best measure of potential storage fife of pears horn any single orchard. For the Bartlett variety, a firmness of 19 to 17 lb may indicate best storage quality. If average firm ness is as low as 15 fl>, individual pears may be sufficiently advanced in maturity that storage for any prolonged.period is hazardous. Pressure test information for each lot of pears going into storage may be very helpful to the owner of the fruit and the cold storage operator in determining the stor age program. Careful harvesting and handling practices are essential to good storage quality. Bruises and skin breaks are likely rites for infection by microorganisms. Varieties such as Winter NeBa and Bose are highly susceptible to stem punctures caused by stems broken in the harvesting operation. Comice is also easily damaged because of its very tender skin. Many pears are now being harvested into pallet bins holding about 1000lb of fruit. These binscreatenospecial problems, but care in dumping fruit from a picking container is highly impor tant in keeping mechanical damage to a minimum -For best storage quality rapid cooling after harvest is emeatial. Pears ripen rapidly at elevated temperatures but the early stages of ripening are obscured by failure to soften or change color. Therefore, a considerable part of the storage He may be used up without a visible change being observed. Where cold storage rooms do not have adequate refrigeration and ventilation capacity for the rapid cooling of hot fruit, precooling should be considered prior to placing in the stor age room. Cooling in special rooms constructed for this pur pose or hydrocooling has proven effective. When warm fruit is placed in a room with cold fruit, the loading arrangements should be such that the temperature of the cold fruit is not elevated. The recommended storage temperature for pears is 30 to 31 F. Recommendations as low as 29 F have been made, but the risk of freeling injury is great unless the temperature u all parts of the room can be controlled precisely. Pears are Dot subject to chilling injury as are some apple varieties, so rievated storage temperatures are not required. The stacking arrangement in the cold storage room recommended for apples also applies for pears. As pears lose water more readily than do most apple vari- ches, it is important to maintain good humidity conditions in Table 4 .... Storage life of Pear Varieties at 30-31 F Variety Bartlett, Cornice, Hardy and Kieffer Bose Anjou Winter Nelis Storage life, Mootfu 2-3 3-4 4-6 6-7 the storage room.. For long storage, 90 to 95 percent relative humidity is recommended. Perforated film box liners have given excellent results in moisture loss control. The approximate storage fife of pears at 30 to 31 F is shown in Table 4. These values assume an additional time for trans portation and marketing. If Bartlett pears for running are harvested at the best stage of maturity and cooled quickly to 30 to 31 F, their safe storage fife may be as long as 4 months, since marketing involves only ripening for processing. How ever, it should be noted that quality deteriorates during stor age, particularly as the maximum storage fife ts approached. After removal from storage, best dessert quality is attained if pears are ripened in a controlled temperature range of about 60 to 70 F. This applies to cannery fruit as well as that for fresh use. Ripening at 68 to 72 F is more practical for can nery fruit than lower temperatures because the shorter time involved reduces overhead costs with no measurable differ ences in quality. Controlled atmosphere storage of pears looks promising based upon experimental studies. The storage life of Bartlett pears can be extended to 5-6 months for good storage quality fruit in an atmosphere containing about 5 percent COi and 2.5 percent Ot at 32 F. Perhaps this could be further extended if tire temperature were 30 F. Not quite as effective, but show ing good results, were atmospheres of 1 to 2.5 percent 0> with no COi involved. Commercial storage of pears in controlled atmosphere has not been considered as necessary as in the apple industry. Since no low temperature disorders have been recognized, there has not been an important need for further extension of the storage life. This has been particularly true of the Bartlett variety where surpluses for fresh use have gone into process ing. If controlled atmosphere storage were used on any impor tant scale with Bartlett, the fall and winter varieties would probably face a considerable market adjustment. Polyethylene film liners, while unsuited to modified at mospheres because of great variability, have proven useful in extending the storage and market fife of pears by reducing water loss to an insignificant level. Storage Disorders The principle storage disorders in pears are (1) core break down, (2) failure to ripen and scald, and (3) fungous rots, particularly gray mold (Botrytis cinerea). Core breakdown is associated with overmaturity at harvest. This problem has become more important since growth regu lator sprays have been used to keep pears from dropping dur ing the harvest season. Pressure test information of late har vested fruit is helpful in locating lots susceptible to core break down. Records are important also relative to time lapse be tween harvest and storage, since pressure test information may not be a true measure of relative storage quality where storage is delayed. Pear color, particularly in California Bartletts, is a very poor measure of potential storage fife because of great variability between pears from different districts.