Cuts, Bruises, and Spoilage

T. R. Wright, Edwin Smith.

Fruits and vegetables, being tender, bruise easily and then spoil quickly as every housewife knows who sorts apples, pears, peaches, bananas in the grocery as a matter of course to avoid taking spoiled ones home.

Between tree and retail bin before the housewife inflicts her own bruises on them with thumbnail and fingers as she sorts them apples might have to go through quite a bombardment of heavy blows when packages are roughly handled during storage, car loading, transit, and delivery to retail stores.

Pears, before softening, are more resistant to bruise injuries than most other deciduous fruits. Their market value is lowered greatly, though, by skin injuries that resemble bruises but actually are caused by friction. That type of blemish, sometimes called "belt burn," occurs during packing and handling. Pears withstand normal handling without showing blemishes when they are packed immediately after picking. As they age in storage, however, the skin becomes less resistant and the degree of disfigurement from a like amount of friction increases progressively during successive weeks of storage.

At a temperature of 31 F., Anjou pears may be stored for a month before packing without showing excessive abrasion blemishes, but longer delays are not advisable. In packing, paraffin-coated chip-board liners will protect pears from friction against the box sides. Pears are extremely sensitive to abrasions after they ripen, and if they are not handled with great care when they are being placed in retail displays, unattractive blemishes are certain to appear.

Defacement of peaches from bruising follows excessive pressure in the package or from rough handling and jostling of the package after the peaches have softened. Severe bruising of peaches in baskets frequently occurs at the bottom of the package (because of the weight of the fruit above) or at the top of the package (from lid pressure in overfilled baskets). The extent of the bruising is related to the ripeness of the peaches when they are shipped.

Loss from the bruises on peaches to be used for processing is extensive. Fruit is wasted; extra labor is needed to trim bruised spots; yield of Fancy grade halves is lowered when trimming makes the fruit good only for slices. To avoid such losses, growers must pick canning peaches so that the fruit is mature but not soft. Studies showed that the number of fruits severely bruised was four times greater when mixed firm and ripe peaches Were sized than when firm peaches only were sized. When mature but firm fruits, sized 24 hours after picking, were processed, 1.26 pounds of trimmings per 500 peaches were removed, as against 4.04 pounds of trimmings from peaches that were sized 5 days after picking.

Spoilage due to excessive bruising extends also to seemingly more durable products such as potatoes. "Transit bruising" is apparent on the surface of potatoes and is caused largely by pressure of the tubers against the floors or walls in cars or trucks. The use of excelsior pads on floor racks in the cars have more than paid for their cost in reduced spoilage of that type, and care in loading to prevent shifting of sacks against side walls will avoid bruising from that source.

Cracks or "shatter bruises" follow heavy impacts when potatoes are handled while turgid and may cause serious damage in some places at harvest. It also becomes a problem when attempts are made to grade and sack potatoes after storage at low temperatures without a warm-up period. Potatoes warmed to a range of 35 to 50 F. in the bins before passing over the grader remain free of cracks; 50 percent of those that have not been warmed may have fresh cracks. Such damage may extend quite deeply into the flesh and cause more extensive damage than is apparent on the surface.

The careful adaptation and adjustment of the potato digger to immediate field and crop conditions is especially important in preventing digger cuts and "feathering." The tender skin of early potatoes is easily scuffed to cause feathering, and, wherever soil conditions make it possible, the digger chains should not employ kickers or eccentrics. Eccentrics, if they are used, should be set for the minimum throw necessary to remove the soil.

If the tissues exposed by feathering are allowed to dry rapidly they fail to cork over normally. Shriveling and a brown discoloration result. The unsightly appearance from the discoloration and the withering of seriously affected potatoes greatly lower their market value losses that can be largely avoided by protecting the freshly dug potatoes from drying by picking up promptly after digging, using tightly woven bags, and covering with tarpaulins during hauling.

Internal black spot of potatoes, a blackening of the internal tissues, may follow bruising. The disorder usually is most pronounced just beneath the skin. Potatoes grown in regions where internal black spot is a serious problem should receive special care in handling to avoid mechanical injuries.

Waste due to mishandling is not confined to those fruits and vegetables that must be thrown away at the store or at home because of their bruised appearance and poor quality.

Cuts and bruises furnish an entry for fungi and bacteria that cause rots during storage or shipment and result in much greater waste than that due to bruising alone. Spoilage from rots following cuts and bruises affects even products such as oranges, lemons, and grapefruit on which surface bruises do not show readily.

A research project of the Department of Agriculture was started in 1903 to study the decay of California oranges while in transit to eastern markets. Losses from decay at that time were estimated to be as great as 1,500,000 dollars annually. The rots were ascribed to two species of blue mold, Penicillium glaucum and P. digitatum fungi that were considered saprophytic or incapable of penetrating healthy, living tissue. It was observed that rot that was just starting was in the area where the skin had been previously injured by a cut or an abrasion.

The observations were followed by a series of laboratory studies by Mrs. Flora W. Patterson, a Department of Agriculture mycologist, who found that the blue mold fungus could not penetrate the epidermis of a sound orange even under conditions most favorable for its growth. It was thus evident that preventing injuries would reduce decay by blue mold.

G. Harold Powell and associates in the Department of Agriculture investigated the extent of mechanical injuries to oranges during harvesting and packing and their relationship to decay. He published his findings in a circular issued February 27, 1905. He found that as much as 35 percent of the fruit from some growers was mechanically injured and that some pickers injured 50 to 75 percent of the oranges they picked. The number of injured oranges in 10 packing houses varied from 4.2 to 22.7 percent. Twenty-five to 30 percent of the fruit from one association that had the reputation of producing fruit of the poorest carrying quality was found to be injured before shipment. Shipping tests disclosed that apparently sound fruit packed by the association showed an average of only 1.8 percent decay upon arrival in New York, compared to 26.9 percent in mechanically injured fruit.

The findings resulted in real progress in reducing bruises and decay after they were brought to the attention of orange growers. Before that time 15.8 percent of the fruit from one large corporation was mechanically injured. Subsequently the injuries were reduced generally to less than 2 percent. Harvesting methods were revolutionized, packing-house equipment was redesigned, and measures to control insects in the groves were changed in order to eliminate mechanical injuries to the fruit before it was shipped.

That early work profoundly influenced the citrus industry in California and was the forerunner of many studies on the importance of careful handling to reduce spoilage of fruits and vegetables. In the decade after 1907 extensive experiments demonstrated the importance of careful handling in harvesting oranges in Florida, grapes in California, and sweet cherries, red raspberries, and Italian prunes in the Pacific Northwest.

No special investigations had been conducted with apples relative to the effect of careful handling in lessening rot invasions before 1917, when H. J. Ramsey and his associates, in writing a Department bulletin on "The Handling and Storage of Apples in the Pacific Northwest," cautioned growers about the need to prevent skin injuries to avoid the serious storage decay of apples caused by blue mold. In the light of recent pathological studies with apples it is interesting to note that although they believed the blue mold fungus incapable of infecting an uninjured, healthy fruit they pointed out that "a microscopic break in the skin of an apple is sufficiently large to afford entrance to the decay fungus." It was generally believed that Penicillium expansum, the organism that causes blue mold decay in apples, would not penetrate the unbroken skin of a healthy fruit until F. D. Heald, of Washington State College, reported in 1932 that an examination of apples in commercial storages showed entrance through lenticels more frequently than through skin ruptures.

Harley English, of the Department of Agriculture, later discovered that blue mold entered apples through true lenticels and also through minute lenticel-like openings, the nature of some of which was obscure. English and his associates also observed that many lenticel infections occurred in bruised areas and thought it probable that localized pressure ruptured cells in the lenticel basins and thereby increased susceptibility. The observations changed the conception of infection and the procedures for preventing blue mold (which is by far the most important rot of apples) because previously it was the common belief that prevention of stem punctures or other visible skin breaks during harvest and packing would largely avoid infections by blue mold.

The apples thus far observed to have blue mold infections at lenticels had all been subjected to commercial handling at harvest. Interest centered in how much the bruising due to commercial handling had contributed to the vulnerability of apples with apparently sound skin. This interest was intensified in 1947 and 1948 by the large number of bruises found on commercially handled apples in the Pacific Northwest. Slight bruises on red apples are not very noticeable and are largely ignored by the apple industry. However such bruises might be the cause of the microscopic injuries concerning which Ramsey and his associates cautioned in 1917.