Fruit receiving

To reduce losses in quality and recovery, all received fruit should be processed within 24 h of harvest. Trucks with bins containing up to 6 tons of decrowned fruit are weighed on a scale at the cannery upon arrival. Details regarding the origin of the fruit are carefully recorded. Such record-keeping practices are becoming increasingly important in developing trace-back information, which can be used in the event of product recall or any other activity that may require limiting the scope of investigation related to finished products. The type of information being gathered will vary among fruit obtained from private growers, cooperatives, or contract growers or from fields owned and/or operated by the cannery.

Before the fruit are unloaded, samples may be taken from the arriving load to assess fruit quality, size distribution, shell colour, disease incidence, possible pest infestation or flesh nitrate level. These indices can affect how and when the fruit will be processed. Fruit are then carefully unloaded and stacked near the fruit-dumping station for immediate processing.

Unloading may be accomplished by hand, by dumping into water or by hydraulic lifts, which raise the bins and gently unload the fruit on to conveyors that lead to the size graders. Careful fruit unloading is another critical factor in minimizing fruit bruising (Timm and Brown, 1991). Water has been shown to be one of the best methods of unloading, where fruit drops directly into a flume of water that is deep enough for the fruit to be moved away from other unloaded fruit and others that have sunk before being elevated out of the water to the size graders. Salt water has been effectively used to separate translucent fruit from opaque fruit, which may be unacceptable in some fresh-fruit markets.

Grading for fruit size is one of the most important activities in maximizing the recovery of marketable products. A precise determination of the relationship between fruit diameter and recovery should be made for each growing area and each clone of pineapples being grown. Seasonal variations in recovery should also be checked to ensure that there are no major differences. The normal procedure used in determining the ideal grader settings is to separate fruit by small increments of diameter, e.g. 1/16 in. or 1.5 mm, and to evaluate all fruit in a diameter class for product recovery. If slice products are of the highest value, then this measure may be sufficient as a means of determining optimum recovery. Others may choose to assign values to all products and determine the optimum economic recovery.

Table 11.1 demonstrates the relationship between individual fruit weight and cylinder weight. The points at which the recovery curves for each Ginaca knife size intersect determine the critical settings for the graders. All grader performances should be checked, using precisely machined, handheld graders. These consist of two parallel bars, separated at predetermined distances to measure fruit diameters (Fig. 11.1).

Once the fruit are properly graded, size distribution to the Ginacas should be con-

Table 11.1. Relationship between individual fruit weight and cylinder weight.

1T weight (kg) 2T weight (kg) 2\ weight (kg)

Fruit

Cylinder

Fruit

Cylinder

Fruit

Cylinder

0.73

0.19

1.23

0.40

1.83

0.64

0.74

0.23

1.25

0.39

1.86

0.61

0.75

0.20

1.26

0.41

1.88

0.64

0.75

0.21

1.28

0.41

1.90

0.63

0.75

0.23

1.30

0.41

1.90

0.71

0.76

0.21

1.32

0.42

1.94

0.66

0.76

0.25

1.32

0.41

1.94

0.69

0.79

0.23

1.33

0.41

1.95

0.68

0.79

0.23

1.35

0.41

1.96

0.67

0.81

0.22

1.35

0.44

2.02

0.66

0.81

0.24

1.36

0.44

2.02

0.68

0.82

0.22

1.37

0.45

2.01

0.71

0.83

0.24

1.42

0.44

2.01

0.70

0.84

0.23

1.42

0.46

2.08

0.72

0.84

0.25

1.44

0.47

2.10

0.68

0.91

0.26

1.47

0.47

2.10

0.69

0.91

0.31

1.50

0.47

2.13

0.73

0.94

0.24

1.51

0.46

2.15

0.69

1.51

0.47

2.18

0.75

Fig. 11.1. Hand-held pineapple grader.

trolled to keep the cannery in balance between the various fruit sizes with a minimum number of changes to the Ginaca settings. This can be accomplished by the use of accumulators for each major fruit size and unloading fruit that complement the desired size requirements, based on information gathered at fruit receiving.

Fruit may be divided into size classes by counter-rotating screws, which use fruit diameter to grade fruit into processing size classes (Table 11.2). The smallest fruit that falls through the grader rolls at the narrowest part is classed as Sub 1T (Cruess, 1938). The other fruit sizes in increasing diameter are 1T, 2T and 21/ These designations are

Table 11.2. Fruit diameter for grading.

Size class

Fruit diameter (cm)

Sub 1T

< 9.21

Small (1T)

9.21-10.80

Medium (2T)

10.80-13.02

Large (2JT)

>13.02

derived from equivalent can sizes in which slices cut from these fruit would fit conveniently. The Sub 1T fruit is frequently used for juice. The graded pineapples then fall into three separate conveyors of parallel water flumes, one flume per fruit diameter, each flume also serving to partially wash the fruit. Since overripe pineapples sink because their density values are greater than that of water, a water flume may be used to separate and wash them. At the end of the flumes, graded and washed pineapples are lifted by conveyors and sprayed with a chlorinated water rinse at approximately 20 p.p.m. chlorine. The graded and rinsed fruit are then transferred to other conveyor belts headed to the fruit preparation areas.

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