Document MzZn1YaKOeyEbDzQeGrJv6Nz

504 CHAPTER 47 1962 Guide And Data Boot : of enveloping the fruit in a high humidity atmosphere result ing in fresher arrivals at destination. In order to minimize the handling of this tender fruit as much as possible, the industry is now beginning to cut the hands of fruit from the stems in the tropics. These hands are then packed in boxes at the tropical plantations, thus eliminating many of the sources of handling damage. There is still much to learn concerning refinements in this tropical packaging operation but due to the domestic im provement in fruit appearance, the refrigeration industry should recognize the difference in handling and ripening trop ical boxed fruit as well as stem fruit. The stems are harvested in the usual manner and trans ported to strategically located receiving stations or to central ized boxing stations. Here the hands are cut from the stalks and are then subjected to various processes for removal of foreign matter, elimination of latex (elastic, sticky, milky white fluid which exudes from green fruit when cut), and treatment with fungicides or fungistats. Some banana* are hydrocooled, boxed, and stored in holding rooms prior to ship ment to the tropical seaport, while other boxes are shipped directly to the port where the refrigerating system of the ship is used to remove the field heat from the boxed fruit. To prevent stems and boxes of bananas from ripening dur ing shipment; the holds of the refrigerated steamships are precooled so that the field heat will be removed as rapidly as possible. The fruit is reduced to a carrying temperature of about 55 F which is maintained throughout the journey to the domestic port. The stems and boxes of fruit are unloaded at the domestic wharf with mechanical unloading equipment. The discharge of a banana cargo must be a continuous opera tion from the time the ship's hatches are first opened until all ' the fruit is unloaded and stowed in refrigerator cars or trailer trucks for distribution to food warehouses in various cities. The bananas are protected as far as possible from damage by exposure to excessively high or low temperatures. In the win ter, where the climate requires, provision is made to heat the discharging areas so that the fruit will not be exposed to tem- peratures lower than 55 F. The bananas are inspected peri-' odicaUy while enroute to the consignee to insure safe delivery temperatures. Only refrigerated, insulated, fan-type railroad cars and refrigerated trailers are recommended for banana service. Refrigeration is required in the summer, and heat is provided in the winter as necessary. The total length of time required for shipment and tem perature during shipment affect the ripening and handling characteristics of various lots of bananas. The total time elapsed from harvesting to ripening room depends on: (1) (he distance from the plantation to the tropical port, (2) the ocean voyage which may vary from 4 to 10 days, and (3) the dis tance from the domestic port to the ripening room which may be up to 7 additional days. This time lapse, plus temperature, humidity and ventila tion influence the condition of the fruit on arrival at the ripen ing rooms and the rate of ripening. Usually, bananas subjected to greater lengths of time in transit will have undergone ripen ing to a further degree than bananas that have been recently harvested; Another factor responsible for variation in ripening and handling characteristics is the maturity of the bunch at tire time of harvesting aa indicated by the fullness or plumpness of the individual fingers, which is known as grade. There are many other factors that influence or cause varia tions In ripeoing and handling characteristics such as, climate, rainfall, etc. Rfwginfts are sold by the importer to wholesale jobbers in carload or truckload lots of whole stems, or tropically packed Table 7------ Approximate Temperatures for Ripeniru, Stem Bananas* " IP Ripanfag Sdfdvtt rmptrafim, F --- Itf 2nd 3rd m 515 6th dor day 4 days 5 days 6 days 7 days 8-10 days 64 64 62 60 62 62 62 62 60 62 62 60 60 60 60 GO 60 60 60 58 58 58 68 58 58 58 58 * Valid only ii ripening it dose with ethylene. boxes weighing 40 lb net. R*n*na^ should be unloaded as soon as possible after arrival at the ripening plant. Prompt unload ing and careful handling will minimis damage. The fruit must be brought under control as soon as possible to insure successful ripening on a predetermined schedule which is pos sible only in properly equipped ripening rooms. Ripening During ripening, enzymatic changes take place in the pulp of the fruit. The pulp of the green banana contains about 20 percent starch. As ripening progresses, this starch is con verted to sugars, principally sucrose, dextrose and levulose. Color changes in the peel occur simultaneously with the pulp change and are also enzymatic. Rates at which these changes take place depend upon the relative activities of different en zymes, which, in turn, are stimulated or depressed by the physical conditions to which the fruit is exposed. Green bana nas contain two classes of pigments, chlorophyll (green) and carotene (yellow). During ripening, the chlorophyll is grad ually destroyed by enzymatic action allowing the carotene to become more and more evident. Within certain limits, the period required for ripening green fruit can be extended or shortened to meet trade require ments. Under average conditions ripening cannot be accomp lished in less than 3 or 4 days nor extended much beyond 8 to 10 days without resorting to drastic treatment harmful to the quality and salability of the fruit. Especially important in controlling ripeningis the change in rate of heat generation aa the ripening cycle progresses. The rate of respiration and corresponding rate of heat generation varies with the temperature at which the fruit is held and with its stage of ripeness. The rate increases as the temperature rises and is highest when the fruit is in the turning stage. The controlling factors in banana ripening are generally recognized to be temperature, humidity and ventilation. Temperature. Ripening characteristics of different lots of bananas vary with tbe country of origin, botanical va riety, season of the year, maturity of the fruit when har vested and other factors. It is impractical to set down precise ripening temperatures that will cover all of the foregoing variables. Suggested ripening temperatures are for bananas with average characteristics. Approximate temperatures for ripening average shipments of Kaninas are indicated in Tables 7 and 8. These temperatures are approximately correct only if ethylene is administered on the first day, and the room is ventilated 24 hr after the application of ethylene. If, for any reason, ethylene is not used, initial temperatures must be 3 to 4 F dejg higher than shown, The temperatures shown for ripening tropical boxed fruit are reliable only if the boxes are stacked to permit adequate air circulation. The two most common stacking methods are the in-line stack utilizing forced air principles, and the chim- Sforage of Apples, Pears, Grapes, and Bananas 505 table 8 . . Approximate Temperatures for Ripening Tropical Boxed Bananas* Effect of Exposure to Excessively High or low Temperatures ftwort Sd*dd ,,. .. Sff. 6th 7ih day day day day day day day 4 day* 5 day* 6 dy 8 day* 64 62 56 62 62 60 57 58 56 56* 56* 62 58 58 58 58 57 . xr.T^ not? ii rineoioi i* done with ethylene. vnSTuro* Michel M F. Varieties 57 F. 57 day 66* oey stock. With the first method the boxes are stacked in rows, shout seven boxes high, the longitudinal axis of each box beiog parallel to the longitudinal axis of the room. The rows of boxes are separated by 4 in. air channels. Air baffles of card board, canvas, plywood or other suitable materials are ar ranged so that the delivery air will be directed to the air entrances which are farthest from the unit cooler. TOese baffles are positioned so that tbe air must pass through the ah' channels before returning to tire unit cooler. The sec ond method is known as the chimney stack which provides a lied load on standard pallets and is commonly used in the produce industry. Humidity. For green stem fruit, it is recommended that the relative humidity in the rooms be kept as high as pos sible, 95 to 100 percent. To. keep down loss of moisture it is further advisable to avoid excessive air circulation. Circulat ing fan* are connected so that they run continuously only during the initial heating period; and when under refrigera- tion, only during the periods when the cooling thermostat is calling for refrigeration. The relative humidity must be some what lower, about 85 percent, after the fruit has started to color. The effect of refrigeration when reducing the tempera ture of turning fruit is to automatically lower the relative hu midity of the air at a stage of the ripening cycle when lower humidity is desired. Humidity control Is somewhat different when ripening tropical boxed fruit. The transpiration of the bananas will increase the relative humidity of the air surrounding the fruit and the box itself tends to prevent loss of moisture because there is little air movement inside tbe box. The spray nozzle system for providing moisture when ripening stems is not used when ripening boxed fruit. Ventilation. Raimna rooms should be tightly constructed end not ventilated during the early stages of ripening. Bananas, during ripening, give off small amounts of ethylene, volatile esters, and carbon dioxide, which must be con-' fined to the ripening room, particularly during the early stages of the ripening process. The amount of these gases present has a direct bearing on the rate of ripening at a given temperature. To control the speed of ripening, it is highly de sirable to administer ethylene artificially. Only a very small amount of ethylene is required (1 cu ft of ethylene per 1000 cu ft of room volume). Since the bananas themselves produce ethylene, a natural ripening stimulant, the ripening process is normal and no deleterious effects result and no difference in taste of ethylene-ripened fruit can be detected. The affect of ethylene is merely to stimulate or trigger the normal enzy*natic changes which occur during ripening. Ethylene is recommended for ripening all varieties of harmna* both stems atld tropical boxed shipments. Such treatment will assure uni form coloration on a predetermined schedule ami will permit use of lower than normal ripening temperatures, resulting to increased store life of the fruit. Exposure to temperatures above 70 F or below 55 F ad versely affect hanftnft* with the extent of the injury depend ing on both the temperature and the time of exposure. dulling is mainly a peel injury caused by low but not freez ing temperatures. Certain surface cells of the peel are killed as evidenced by discoloration and by examination under a microscope. Dead cell contents darken by oxidation and give chilled fruit its characteristic dull appearance. Chilling affects both green and ripe bananas. With ripe bananas, the effect of chilling is not immediately apparent. The dull color does not appear until after tire fruit is exposed to warmer temperatures. Chilling causes a dullness of tbe peel and increased sensitiveness to even slight handling. The exact upper limits of chilling temperatures cannot be sharply defined but vary somewhat with the variety and the condition of the bananas and, of course, with the duration of the exposed period. It is well to avoid temperatures below 56 F for Gros Michel and 58 F for the variety fruits such as Lecat&n and Cavendish, especially in moving air. Twelve hours exposure at any temperature below 45 F in still air generally causes chilling injury sufficient to affect the salability of the fruit, regardless of the stage of ripeness when exposed. Since no method has been found by which the dead cells may be restored, no remedial measures are available. Bananas subjected to low temperatures should be brought to normal ripening temperatures as rapidly as posable to reduce, in a measure, the period of exposure. Although the peel appear ance will be affected, slightly chilled bananas will ripen normally. Exposure of ripe fruit to temperatures greater than 70 F also has a deleterious affect, the damage being proportional to the temperature and time of exposure. In severe cases, the bananas become soft, the peel is weak and easily split or broken. The term cooked is normally used to describe this type of injury. Cooked fruit may be the consequence of poor ripening procedures, failure of the refrigerating system, or Ugh temperatures encountered in retail stores during the summer months. Banana Ripening Rooms The construction of banana ripening rooms is somewhat similar to that of ordinary cold storage rooms. The'rooms re quire adequate insulation, refrigerating and heating systems, and must be as air tight as construction techniques will permit. An important consideration in the design of rooms for han dling steins of fruit is that the banana load is suspended from joists or racks instead of resting on the floor. This load tetrans ferred through posts or columns to reinforced concrete curbs along the side walls of the rooms. These supports carry a con centrated load, therefore, the curbs and footings must be de signed to support the maximum loading conditions of the rooms. The stems are bung from hooks inserted in the joists, or carrier bars in the case of fork-lift type rooms. For rooms equipped with banana joists, a clear height of 9 ft is required from the floor to the undertide of the banana joists. The joists should be on 14 in. centers and the banana hooks and eyes spaced 8 in. apart along the joists. These hooks and eyes should alternate in both directions, so that no two hooks and no two eyes are adjacent. The stems of bananas are hung in two tiers, the upper tier hanging directly from the hooks and the lower tier suspended on ropes fastened to the eyes.