Apple Bruising. I. Evaluating Grading Lines 



William J. Bramlage 



Department of Plant & Soil Sciences, University of Massachusetts 



Bruising is responsible for downgrading large quanti- 

 ties of apples and other fruit. A single bruise larger than 5/ 

 8 inch in diameter, or several smaller bruises with an 

 aggregate area of more than 1/2 inch diameter will elimi- 

 nate an apple from the U.S. Extra Fancy grade. Some 

 bruising may occur before harvest, but the great majority 

 of it occurs during harvest, transport to the packing house, 

 grading and packing, transport to the retail outlet, and 

 during retail marketing. A great deal of this bruising is 

 caused by the harvesting and packing operations, and is 

 largely preventable. While any knowledgeable fruit 

 grower knows that a ripe apple is easily bruised and can 

 identify some obvious sources of bruising, many sources 

 are difficult to identify and thus to remedy. 



Personnel at the U.S. Department of Agriculture, 

 Agricultural Research Service and at Michigan State 

 University have been conducting cooperative research on 

 the sources and consequences of apple bruising, and have 

 published a series of reports on their findings that are very 

 helpful in identifying and correcting sources of bruising. 

 This article is the first in a series of articles in Fruit Notes 

 on their findings about this extremely important subject. 



Apple packing lines offer many opportunities for 

 bruising, but identifying trouble spots is not always easy. In 

 a paper presented at the December 15-18, 1987 meeting of 

 the American Society of Agricultural Engineers, G. K. 

 Brown, C. L. Burton, S. A. Sargent, N. L. Schulte Pason, E. 

 J. Timm, and B. E. Marshall addressed this problem. 

 Their paper, entitled "Apple Packing Line Damage As- 

 sessment," examined bruise, cut, and puncture damage 

 incurred by Golden Delicious apples as they moved 

 through typical mechanical packing and grading lines. 

 Eight different packing lines were tested, representing the 

 widely-used equipment and the range of daily capacity of 

 commercial packing houses in Michigan. The lines were 

 all evaluated twice: mid-September to mid-October 

 (freshly harvested apples), and early-January to early- 

 February (ripe air-stored fruit). 



Apples were sampled at 4 locations: input to the 

 washer, output from the dryer (after waxing), on the sizer, 

 and on the packing table. Additional samples were taken 

 after bagging. Bruises were all rated according to size 

 (diameter): "A" = 1/4 to 1/2 inch; "B" = 1/2 to 3/4 inch; 

 "C" = 3/4 to 7/8 inch; "D" = 7/8 to 1 1/4 inch; "E" = 

 more than 11/4 inch. 



Sampling at the washer input measured bruising that 

 occurred in the flotation tank, the undersize eliminator. 



and the inspection belt. Two-thirds of the apples sustained 

 bruises in these operations. Sampling at the dryer meas- 

 ured damage from the washer, dewaterer, waxer, and 

 dryer. More damage occurred in these operations than 

 anywhere else on the line. Sampling on the sizer showed 

 damage from the singulator and from transfer to the sizer, 

 and this was the second-most source of fruit damage on the 

 hne. Sampling at the packing table showed damage that 

 occurred from the sizer, and the conveyor, and here the 

 least amount of damage occurred. By the time the fruit 

 reached the packing table, 99% of them had been bruised 

 in the packing line. To evaluate damage in the bagging 

 operation, bruise-free fruit were bagged. This step was the 

 most damaging of all, bruising 91% of the apples. 



These results are depicted in Figure 1, showing the 

 average number of bruises per fruit incurred in each of 

 these operations, for each of the 8 packing lines. The data 

 shown are for the late test. 



Up to the bagging operation, over 90% of the bruises 

 were of the "A" size, less than 1/2 inch in diameter, and 

 less than 5% of the fruit were cut or punctured. However, 

 during bagging the damage was more severe; 20 to 25% of 

 the bruises were 1/2 to 3/4 inch in diameter, and 4 to 5% 

 of the fruit were cut or punctured. 



There were few differences in results between the fall 

 and winter tests, meaning that ripening had little effect 

 when compared with the operations of the packing lines. 

 One difference that did exist was that freshly harvested 

 fruit were more likely to be cut or punctured than were 

 fruit out of storage. 



As you might expect, there were great differences in 

 damage among the different packing lines, indicating that 

 much of this damage is under the control of the packing 

 line operator, and thus is correctable. This was demon- 

 strated clearly in that total number of bruises was reduced 

 by 50% in the late test, after operators saw the results of the 

 early test and began taking corrective actions. 



The authors summarized their assessments of the 

 causes of damage as follows. 



Sampling Point A: 



l.RoUing fruit hit steel chains, rollers, plates, and other 

 fruit. 



Sampling Point B : 



1. High washer or waxer brush speed resulted in bounc- 

 ing and stacking of fruit. 



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