The Effect of Fruit Size on Various Fruit Quality Characteristics

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Cucurbit Genetics Cooperative Report 3:15-16 (article 9) 1980

J. Mather and R. L. Lower
University of Wisconsin, Madison, WI 53706

Fruit firmness is an important factor in assessing the quality of pickling cucumbers. The most frequent measurement of fruit firmness is pounds of pressure as determined by a Magness Taylor Fruit firmness is pounds of pressure as determined by a Magness Taylor Fruit Pressure Tester (MTFPT) equipped with a 7.9 mm tip plunger. A study was made to determine the relationship of fruit diameter, the fruit skin, and tip placement on MTFPT readings taken on fresh fruit. Assessments of placental hollowness and carpel separation were made on larger fruit.

Plants of the cv. ‘Calico’ were grown at the Hancock, WI Experimental Station using standard cultural practices. Five sections of 30ft of row were used as replications. The fruit were harvested in mid-september and graded by hand. Fruit grading was based on PCIC standards (Table 1). A 20 fruit sample of each size from each replication was selected bases on uniform shape. The skin was removed about 25.4 mm from both the stem and blossom end from one-half of the sample (ten fruit). Pressure tests were taken at both ends of fruit with and without skin. The plunger was placed at the juncture of two carpels, one-third of the distance from either the stem or blossom end, and penetration was at a 90° angle to the plane of the fruit which was on a solid platform. Only one measurement was obtained at each end. Fruit of the two largest sizes were cross-sectioned at both ends and the middle, and were checked for placental hollowness and carpel separation. The diameter of the fruit and the seed cavity were measured from the middle cross-section.

Pressure tests were significantly greater with the skin on the fruit and generally increased with increased diameter at both stem and blossom ends (Table 1). Pressure tests on fruit without skin were greater in size 2 than size 4 at the stem end. A similar pattern was observed at the blossom end where size 2 fruit had higher readings than both sizes 3 and 4. Measurements were greater at the stem end than at the blossom end and the relationship is fairly constant. Tests at the stem end are about 1.25 lbs higher than the blossom end. Thus, it seems that only one reading per fruit is necessary to test relative firmness as long as it is taken at the same end of all fruit.

the incidence of placental hollowness and carpel separation was almost exclusively confined to the largest sized fruit (Table 2). The relationship between diameter of the seed cavity and fruit diameter was expressed as interior ratio and was not significantly different in sizes 3 and 4, thus as the fruit increased in size, the relative size of the seed cavity remained constant. Further investigation will be necessary to test the relationship of these fresh fruit data and brinestock quality.

Table 1. Effect of fruit size, skin, and plunger placement on fruit firmness readings.

Fruit z

Mean pressure test y

Treatment
Size
No.
Stem end
Blossom end
With skin 1 50 23.16 22.42
2 50 25.94 24.72
3 50 26.44 24.60
4 50 27.92 26.64
Without skin 1 50 19.48 18.56
2 50 20.22 19.54
3 50 19.58 17.82
4 50 18.36 17.54
LSD .05 1.31 1.43

z Size based on PCIC standards

Size

Diameter in cm
1 up to 2.7
2 2.7-3.8
3 3.8-5.1
4 over 5.1

y Pounds of pressure determined by using Magness Taylor Fruit Pressure Tester with 7.9 mm tip.

Table 2. Effect of fruit size on several fruit quality factors.

Placental hollowness

Fruit sizez

Fruit size (mm)y

Seed cavity diameter (mm)y

Interior ratiox
Blossom end (%)
Center (%)
Stem end (%)
Carpel separation (%)
3 44.74 26.54 0.59 0 0 6 0
4 66.38 38.20 0.60 2 8 10 24

zSize based on PCIC standards. Size 3 = 3.8 cm to 5.1 cm diameter; size 4 = over 5.1 in diameter.
yMean of 50 fruit.
x  Based on seed cavity diameter/fruit diameter.