Malheur Experiment Station

Oregon State University

Ontario, OR, 2005

Introduction

There is some evidence that onion handling after harvest can bruise bulbs and cause symptoms similar in appearance to translucent scale. Several shippers have suggested that the effect of handling on bruise may be influenced by bulb temperature during handling and by length of time after handling before the onions are checked. This trial tested the effect of handling 4 onion varieties at 2 temperatures on bruise and on bulb recovery after 3 days storage at 38°F.

Methods

Trial 1

Prior to evaluating variety susceptibility to bruise in January 2004, a preliminary test of the effect of drop height on bruise was conducted. Fifteen onions from mixed varieties were each dropped on their sides onto a concrete floor from heights of 0.8 m (2 ft, 7 inches), 1 m (3 ft, 4 inches), 1.2 m (3 ft, 11 inches), or 1.4 m (4 ft, 7 inches). The onions were cut equatorially and rated for damage. During rating we noted where in the bulb the damage occurred and whether the appearance was of translucent or watery, mushy rings. The damaged or bruised area had the form of a triangle (Fig. 1) which extended from the surface to the center of the bulb. When the affected scales were translucent, the damage was different from typical translucent scale in that the scales were only translucent in the bruised area.

onions
Figure 1. Diagram of onion bulb damage or bruising resulting from a drop of 1 m (3 ft, 4 inches).

All drop heights resulted in bulb damage (Table 1). The lowest drop height of 0.8 m (2 ft, 7 inches) resulted in less pronounced damage.

Table 1. Number of onions out of 15 with visible damage or translucent scale after being dropped on a concrete floor from different heights.

Drop height

Onions with damage

meters (ft, inches)
0.0 0 0 of 15
0.8 2'7" 10* of 15
1.0 3'4" 8 of 15
1.2 3'11" 10 of 15
1.4 4'7" 11 of 15

*damage was less pronounced.

Trial 2

Onions of four varieties were randomly placed in nylon mesh bags (24 bags per variety). Given the availability of bulbs, there were 24 bulbs/bag of 'Delgado' (Bejo Seeds), 28 bulbs/bag of 'Granero', 27 bulbs/bag of 'Vaquero', and 30 bulbs/bag of 'Bandolero' (all three Nunhems). On January 13, 2005 the 24 bags of each variety were placed in 2 coolers: 12 at 32°F and 12 at 38°F. Three days later the bags were removed a few at a time from the coolers and were either not handled or handled by dropping each bulb from each bag individually on its side onto a concrete floor from a height of 1 m (3 ft, 4 inches). The spot of impact was marked on the onion bulb. After the handling treatments, half of the bags were put in a cooler at 38°F and the bulbs in the other half of the bags were immediately cut equatorially and rated for bruising. Three days after dropping, the onions in the bags stored in the cooler were rated individually for bruising. The number of bruised bulbs and the number of bruised rings in bruised bulbs was recorded. The width of the bruised area (Fig. 1) was also recorded. Rings with a watery appearance were judged to be bruised. Each treatment was replicated three times (three bags) for each variety (Table 2).

Table 2. Treatments applied to four onion varieties in January 2005.

Treatment Pretreatment storage Handling treatment Post-treatment storage
1 32°F Drop no storage
2

storage at 38°F
3
No Drop no storage
4

storage at 38°F
5 38°F Drop no storage
6

storage at 38°F
7
No Drop no storage
8

storage at 38°F

Results

Table 3. Effect of prehandling temperature, handling, and time after handling on onion bulb bruising, Malheur Experiment Station, Oregon State University, Ontario, OR, 2005.

Variety

Prehandling storage temperature


Bruised bulbs


Affected rings in bruised bulbs
Width of damage in bruised bulbs




Handling treatment

Before storage After storage Avg.
Before storage After storage Avg.
Before storage After storage Avg.

°F


-------- % --------
-------- % --------
------- cm -------

Delgado

32

Drop

91.7 87.5 89.6
92.1 51.9 72.0
5.4 4.8 5.1



No Drop

4.2 0.0 2.1
18.2 0.0 9.1
1.4 0.0 0.7


38

Drop

76.4 90.3 83.3
84.8 58.1 71.5
5.8 5.0 5.4



No Drop

0.0 0.0 0.0
0.0 0.0 0.0
0.0 0.0 0.0


Avg

Drop

84.0 88.9 86.5
88.4 55.0 71.7
5.6 4.9 5.3



No Drop

0.0 0.0 0.0
0.0 0.0 0.0
0.0 0.0 0.0

Granero

32

Drop

85.7 65.5 75.6
83.6 51.3 67.5
5.9 3.9 4.9



No Drop

1.2 3.6 2.4
25.0 17.9 21.4
1.0 1.2 1.1


38

Drop

81.0 97.6 89.3
80.4 78.8 79.6
5.2 5.7 5.5



No Drop

6.0 1.2 3.6
41.7 19.4 30.6
2.5 2.0 2.3


Avg

Drop

83.3 81.5 82.4
82.0 65.1 73.5
5.6 4.8 5.2



No Drop

3.6 2.4 3.0
33.4 18.7 26.1
1.8 1.6 1.7

Vaquero

32

Drop

84.0 72.8 78.4
80.4 40.8 60.6
5.6 5.0 5.3



No Drop

0.0 0.0 0.0
0.0 0.0 0.0
0.0 0.0 0.0


38

Drop

81.5 69.1 75.3
78.9 34.1 56.5
5.6 3.3 4.5



No Drop

6.0 1.2 3.6
41.7 19.4 30.6
2.5 2.0 2.3


Avg

Drop

82.7 71.0 76.8
79.6 37.4 58.5
5.6 4.2 4.9



No Drop

0.0 0.0 0.0
0.0 0.0 0.0
0.0 0.0 0.0

Bandolero

32

Drop

77.8 83.3 80.5
76.3 42.8 59.5
5.0 4.9 5.0



No Drop

0.0 2.2 1.1
0.0 12.8 6.4
0.0 2.0 1.0


38

Drop

83.3 86.7 85.0
76.6 67.2 71.9
5.1 5.0 5.0



No Drop

0.0 0.0 0.0
0.0 0.0 0.0
0.0 0.0 0.0


Avg

Drop

80.6 85.0 82.8
76.4 55.0 65.7
5.1 4.9 5.0



No Drop

0.0 1.1 0.6
0.0 6.4 3.2
0.0 1.0 0.5

Over all averages

32

Drop

84.8 81.6 81.0
83.1 46.7 64.9
5.5 4.7 5.1


No Drop

1.3 1.4 1.4
10.8 7.7 9.3
0.6 0.8 0.7


38

Drop

80.5 85.9 83.2
80.2 59.6 69.9
5.5 4.8 5.2



No Drop

3.0 0.6 1.8
20.9 9.7 15.3
1.3 1.0 1.1


Avg

Drop

82.7 81.6 82.2
81.6 53.1 67.3
5.5 4.7 5.1



No Drop

2.2 1.0 1.6
15.8 8.7 12.3
0.9 0.9 0.9

LSD (0.05)

Handling




3.9


5.1


0.3


Temperature



NS


1.7


NS


Time


NS


1.7


0.1


Temp. X Time


NS




2.4




NS


Variety


NS


2.4


0.2


Temp. X Variety



NS


3.3


0.2


Time X Variety



NS


3.3


0.2


Temp. X Time X Variety


NS


4.7


0.3