1、36.1CHAPTER 36CITRUS FRUIT, BANANAS, AND SUBTROPICAL FRUITCITRUS FRUIT 36.1Maturity and Quality . 36.1Harvesting and Packing . 36.1Transportation 36.3Storage . 36.3Storage Disorders and Control . 36.4BANANAS. 36.5Harvesting and Transportation 36.5Diseases and Deterioration 36.5Exposure to Excessive
2、Temperatures . 36.5Wholesale Processing Facilities. 36.5SUBTROPICAL FRUIT 36.8Avocados 36.8Mangoes. 36.8Pineapples 36.8HIS chapter covers the harvesting, handling, processing,Tstorage requirements, and possible disorders of fresh marketcitrus fruit grown in Florida, California, Texas, and Arizona; o
3、fbananas; and of subtropical fruit grown in California, Florida,Hawaii, and Puerto Rico.CITRUS FRUITMATURITY AND QUALITYThe degree of citrus fruit ripeness at the time of harvest is themost important factor determining eating quality. Oranges andgrapefruit do not improve in palatability after harves
4、t. They containpractically no starch and do not undergo marked compositionchanges after they are picked (as do apples, pears, and bananas), andtheir sweetness comes from the natural sugars they contain whenpicked.Citrus fruit ripeness increases slowly and is closely correlatedwith increases in diame
5、ter and mass. Citrus fruit must be of highquality when harvested to ensure quality during storage and shelf life.Quality is often associated with the fruit rinds appearance, firm-ness, thickness, texture, freedom from blemishes, and color. How-ever, quality determination should be based on flesh tex
6、ture, juiciness,soluble solids (principally sugars), total acid, aromatic constituents,and vitamin and mineral content. Age is also important. Immaturefruit is usually coarse and very acid or tart and has an internal texturethat is ricey or coarse. Overripe fruit held on the tree too long maybecome
7、insipid, develop off-flavors, and possess short transit, stor-age, and shelf life. The importance of having good-quality fruit atharvest cannot be overemphasized. The main objective thereafter isto maintain quality and freshness.HARVESTING AND PACKINGPickingCitrus fruit is harvested in the United St
8、ates throughout theyear, depending on the growing area and kind of fruit. Figure 1shows the approximate commercial shipping seasons for Florida,California/Arizona, and Texas citrus. Trained crews from indepen-dent packing houses or large associations do the picking, which isscheduled to meet market
9、demands. Fruit that is not handledthrough cooperatives is normally sold on the tree to shippers orprocessors and is picked at the latters discretion.Pickers carefully remove fruit from the trees, either by hand orwith special clippers, and then place the fruit in picking bags that areemptied into fi
10、eld boxes. An increasing amount of fruit is handled inbulk, so pickers put fruit into pallet boxes or wheeled carts. In someThe preparation of this chapter is assigned to TC 10.9, Refrigeration Appli-cation for Foods and Beverages.Fig. 1 Approximate Commercial Shipping Season forU.S. CitrusFig. 1 Ap
11、proximate Commercial Shipping Season for U.S. Citrus36.2 2010 ASHRAE HandbookRefrigeration (SI)cases, especially when fruit is picked for processing, it is loadedloose into open truck trailers. In Florida, over 90% of the orangesand slightly more than 50% of the grapefruit and specialty fruit arepro
12、cessed, while in California and Arizona less than 35% of all cit-rus fruit is processed.At the beginning of the season, fruit is often spot-picked; only theriper, larger, or outside fruit is harvested. Later, the trees are pickedclean. In California, lemons usually are picked for size with the aidof
13、 sizing rings.Various labor-saving devices have been tested, including mechan-ical platforms and positioners, tree shakers with catch frames, and airblasts for fruit removal. Mechanical harvesting, however, is limitedto a very small percentage of the total crop. Because of damageincurred, fruit inte
14、nded only for processing is mechanically har-vested. Preharvest sprays have also been developed to improve colorand to loosen fruit to facilitate harvest.HandlingAfter fruit is received at the packinghouse, it is removed from theboxes or bulk containers carefully to prevent damage to the fruit. Itis
15、 then presized to remove oversized or undersized fruit. Beforewashing, fruit may be floated through a soak tank, which usuallycontains a detergent for cleaning and an antiseptic for decay control.The washer is generally equipped with transverse brushes thatrevolve up to 120 rpm. If not applied at th
16、e soak tank, soap or anti-septic may be dribbled or foamed on the first series of brushes. Afresh water spray then rinses the fruit.Fruit then passes under fans that circulate warm air through themoving pieces. When dried, fruit is polished and waxed (typicallywith a water wax), and then passes thro
17、ugh a second drying. It thenpasses over roller conveyor grading tables. After grading, it is con-veyed to sizing equipment that separates the pieces into the standardpacking sizes; the pieces are then dropped at stations for hand pack-ing or conveyed to automatic or semiautomatic box-filling or bag-
18、ging machines. Electronic sizing, based on machine vision, is usedextensively.Packinghouse handling of California lemons for fresh market isinterrupted by an extended storage period. After washing, fruit isconveyed to a sorting table for color separation by electronic meansor by human eye. Usually,
19、separation is into four colors: dark green,light green, silver, and yellow. The dark green is a full green; the lightgreen is a partially colored green (a green with color well broken);the silver is fully colored with a green tip (stylar end); and the yellowis fully colored and mature with no green
20、showing. The normal stor-age life for dark green fruit is 4 to 6 months; for yellow fruit, it is 3to 4 weeks. These periods are approximate, because storage (or keep-ing) quality of fruit varies considerably with season and grove. Alight concentration of water/wax emulsion is usually applied to lem-
21、ons before they are put into storage. The section on Storage has moreinformation on storing the different varieties of citrus fruit.After storage, lemons are waxed, then sized and packed. Post-storage washing to remove mold is desirable but requires a washerwith very soft roller brushes.Shipping and
22、 storage containers vary considerably for the differ-ent types of citrus fruit. In California and Florida, 28 L fiberboardcartons are the standard. In addition, over 15% of Florida fresh fruitis consumer-packed in mesh and polyethylene bags that are nor-mally shipped in 18 kg master cartons. After t
23、he packages are filledand closed, they are conveyed either to precooling rooms to awaitshipment or directly to standard refrigerator cars or trucks. Contain-ers are stacked so that air distribution is uniform throughout theload. Either slipsheets or wooden pallets are commonly used forpalletized han
24、dling.Accelerated Coloring or SweatingAll varieties of citrus fruit must be mature before they are picked.Maturity standards are based on internal attributes of soluble solids,acid percentage, and juice percentage. Color is not always a crite-rion of maturity. The natural change of color in oranges
25、from darkgreen to deep orange is a gradual process while the fruit remains onthe tree. The fruit remains dark green from its formation until it isnearly full size and approaching maturity; then the color maychange very rapidly. Color change is influenced greatly by temper-ature variations. A few col
26、d nights followed by warm days may turnvery green oranges to deep orange. Color changes in lemons andgrapefruit similarly turn the fruit yellow. Unfavorable weather con-ditions may delay coloring even after maturity.Up to a certain point, the natural color changes in Valencia or-anges follow the tre
27、nd described, but complete or nearly completeorange color generally develops some time before the fruit ismature. Some regreening of Valencias may occur after the fruit hasreached its prime. Navel oranges in California, as well as the Floridavarieties of Hamlin, Parson Brown, and Pineapple harvested
28、 in latefall and early winter, may be mature and of good eating quality evenif the rind is green. Grapefruit, lemons, tangerines, tangelos, andother specialty fruit may also be mature enough for eating beforethey are fully colored. Because the consumer is accustomed to fruitof characteristic color,
29、poorly colored fruit is put through a coloringor degreening process in special rooms, bulk bins, or trailer de-greening equipment.These units are equipped to maintain temperature and humidityat desired levels. Approximately 5 mg/kg ethylene is maintained inthe air. The concentration of ethylene and
30、duration of degreeningdepends on the variety of fruit and the amount of chlorophyll to beremoved. During degreening, fresh air is introduced into the room,and a relative humidity of 90 to 96% is maintained. In Florida, tem-peratures of 28 to 29C are recommended, whereas in Californiatemperatures of
31、18 to 21C are used. Lemons are usually degreenedat 16C. In California, the process is called sweating instead of col-oring or degreening.Oranges, grapefruit, and specialty citrus fruit requiring ethylenetreatment are frequently degreened upon delivery to the packing-house, but they may receive a fun
32、gicide drench before degreening.Lemons are washed and graded or color-separated before beingdegreened.Color-Added TreatmentA high percentage of Floridas early and midseason varieties oforanges and tangelos receive color-added treatment with a certifiedfood dye that causes the rind of pale fruit to t
33、ake on a brighter andmore uniform orange color. This is usually in addition to degreeningwith ethylene gas. In color-added treatment, the fruit is subjected for2 to 3 min to the dye solution, which is maintained at 49C. Treat-ment can be in an immersion tank filled with vegetable dye solution,or the
34、 dye can be flooded on the fruit as it passes on a roller con-veyor. The immersion tank is between the washer and the wax ap-plicator. Oranges with the desired color at harvest, as well astangerines and grapefruit, bypass the dye tank; alternatively, theflow of dye may be cut off as the fruit passes
35、 over the equipment.Standards for maturity are slightly higher in Florida for orangesgiven color-added treatment. California oranges are not artificiallycolored.CoolingAfter the fruit is packed, it is cooled. Cooling room efficiencydepends onCooling air rate per railcar load (at least 1400 L/s)Relat
36、ive humidity of supply air (95% or above)Temperature of supply air entering room (no more than 1 K belowthe selected cooling temperature)The fruit may also be cooled in a refrigerated truck trailer or con-tainer after it has been loaded.Citrus Fruit, Bananas, and Subtropical Fruit 36.3In California,
37、 air is used to cool oranges but not lemons or grape-fruit. In Florida, specialty fruit such as Temple oranges, tangerines,and tangelos may be cooled. Chapter 28 discusses cooling practicesand equipment used for various commodities in more detail.TRANSPORTATIONFruit packed in piggybacks, trucks, shi
38、p vans, or rail cars shouldbe stowed in appropriate modifications of the spaced bonded blockto ensure good air circulation, uniform temperature, and stable load.No dunnage is required. Such stowing provides continuous air chan-nels through the interior of the load and improves the likelihood ofsound
39、 arrival. Trailers and containers that circulate air from the bot-tom provide uniform temperatures throughout the load with a regu-lar bonded-block stow.In Florida, the present quarantine treatment for the Caribbeanfruit fly, Anastrepha suspensa, is to subject an export load of citrusto specified te
40、mperatures for up to 24 days (Ismail et al. 1986). Thistreatment may be implemented in containers or in a ships hold.A uniform sample of 1500 fruit is withdrawn from a shipmentbefore ship or container loading and is held at 27C or higher.These fruit are then examined after a 10 day incubation period
41、. Ifan infestation of A. suspensa is found, the entire load mustundergo the long treatment process. Table 1 details temperatureand time schedules.STORAGEPerformance of any citrus storage facility depends on three con-ditions: (1) provision of sufficient capacity for peak loads; (2) anevaporator and
42、secondary refrigerating surface sufficient to permitoperation at high back pressures, which prevents low humidity andlowers operating costs; and (3) efficient air distribution, whichensures velocities high enough to effect rapid initial cooling andvolumetric flows great enough to permit operation du
43、ring storagewith only a small temperature rise between delivery and return air.Chapters 21 to 24 have further information on storage design.OrangesValencia oranges grown Florida and Texas can be stored success-fully for 8 to 12 weeks at 0 to 1C with a relative humidity of 85 to90%. The same requirem
44、ents apply to Popes Summer orange, alate-maturing Valencia type. A temperature range of 4 to 7C for 4to 6 weeks is suggested for California oranges. Arizona Valenciasharvested in March store best at 9C, but fruit harvested in Junestore best at 3C.Oranges lose moisture rapidly, so high humidity shoul
45、d bemaintained in the storage rooms. For storage longer than the usualtransit and distribution periods, 85 to 90% relative humidity isrecommended.Florida and Texas oranges are particularly susceptible to stemend rots. Citrus fruit from all producing areas are subject to blue andgreen mold rot. These
46、 decays develop in the packinghouse, in tran-sit, in storage, and in the market, but they can be greatly reduced iffruit is properly treated. Proper temperature is effective in reducingdecay. However, once storage fruit is removed to room temperature,decay develops rapidly.Prolonged holding at relat
47、ively low temperatures may cause thedevelopment of physiological rind disorders (mainly aging, pit-ting, and watery breakdown) not ordinarily encountered at roomtemperature. This possibility often complicates orange storage.California and Arizona oranges are generally more susceptible tolow-temperat
48、ure rind disorders than Florida oranges.Successful long storage of oranges requires harvest at propermaturity, careful handling, good packinghouse methods, fungicidaltreatments, and prompt storage after harvest.The rate of respiration of citrus fruit is usually much lower thanthat of most stone frui
49、t and green vegetables and somewhat lowerthan that of apples. Navel oranges have the highest respiration rate,followed by Valencia oranges, grapefruit, and lemons. Heat fromrespiration is a relatively small part of the heat load. Table 2 showsheat generated through respiration.GrapefruitFlorida and Texas grapefruit is frequently placed in storage for4 to 6 weeks without serious loss from decay and rind breakdown.The recommended temperature is 10C. A temperature range of14.5 to 16C is recommended for storing California and Arizonagrapefruit.A relative humidity of 85 to 90% is
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