Handbook of Plant and Crop Physiology

B. Shape

Regardless of edibility, the buying public rejects misshapen fruits. But in some cases fruit shape can be a

useful indicator of eating quality.

Mango, a strongly climacteric fruit, develops an irregular shape as it matures on the tree, one “shoul-

der” becoming considerably higher than the other. The more marked this irregularity, the more mature the

mango and so the better chance that, once picked, it will ripen to good eating quality.

Grapefruit typically bloom irregularly, the first major bloom being followed by later blooms at ir-

regular intervals of days, weeks, or even months. Grapefruit from the first bloom tend to be oblate with

the axis often considerably less than the diameter. Such fruit are of superior eating quality. Successive

blooms result in increasingly spherical fruit of decreasing internal quality. “Sheep-nosed” grapefruit (axis

considerably longer than diameter) are avoided by discerning buyers.

More usually, market grades based on fruit shape are quite unrelated to organoleptic quality. That a

banana should be curved and a cucumber should not epitomizes the illogic of many market grades.

C. Thermodynamic Properties

Increasingly, modern fruit distribution involves the use of refrigeration. (Physiological responses of fruit

to low temperature are dealt with in Chapter 2.) Refrigeration can be inefficient or unnecessarily expen-

sive when the refrigeration system used does not take into account the thermodynamic properties of the

product, in this case fruits. Such data are curiously hard to find, being scattered among horticultural and

engineering publications. Such data have been compiled for citrus fruits; see Table 1. The values for heat

of respiration at various temperatures of such highly climacteric fruits as apples, pears, mangos, and ba-

nanas can be several times as high as for citrus fruits.

VII. CONCLUSIONS

There is very little in agriculture that one way or another is not dependent on successful fruit develop-

ment. Among those who make their livelihoods growing and marketing dessert fruits, there are many who

could profit from improved understanding of the complex biology of these gracious additions to our diet.

REFERENCES

1. Soule J. Glossary for Horticultural Crops. New York: Wiley, 1985.


2. Krezdorn AH, Robinson FA. Proc Fla State Hortic Soc 71:86, 1958.

FRUIT DEVELOPMENT, MATURATION, AND RIPENING 157

TABLE 1 Thermodynamic Data for Citrus Fruitsa

Parameter Oranges Grapefruit Lemons

Specific gravity 0.98 0.88 0.95
Specific heat (BTU/lb/F) 0.86 0.88 0.89
Thermal diffusivity (sq ft/hr) 0.0049 0.0047 0.0049
Thermal conductivity:
BTU/hr/ft^2 /F/in. 2.95 3.00 2.85
kcal/sec/cm^2 /C/cm 1.1 0.78 1.05
Heat of respiration (BTU/ton/day) at:
32 F0C 900 500 580
40 4.5 1400 1100 800
50 10.0 1300 1500 2300
60 15.5 5000 2800 3000
70 21.0 6200 3500 4100
80 27.5 8000 4200 6200
90 32 9900 6000 8000
aValues listed as means of data from various sources. Values vary with horticultural variety (cultivar), district,

maturity, size of fruit, etc.
Source: Ref. 69.