Effect of Number of Locules, Loading Position, and Compression Speed on the Mechanical Behaviors of Tomato Fruits

Figures & data

FIGURE 1 Single column test stand (model AEL, Ali Instrument Co., Ltd., ZJ, China) equipped with a 100 mm diameter top plate to compress a fruit against a large base plate. The initial distance between the top plate and the top point of a fruit d was 10 mm. The figure indicates how three locular tomato fruits would be loaded by the top plate at position 1.

FIGURE 2 Three and four locular tomato fruits, (a) Three locular tomato fruit and its simplified equatorial section; (b) Four locular tomato fruit and its simplified equatorial section. Numbers 1, 2, and 3 represent loading positions 1, 2, and 3, respectively.

FIGURE 3 (a) Typical loading-unloading curve for compression of a three locular tomato fruits to 4% final deformation at a compression speed of 1.5 mm s⁻¹; (b) compression energy of tomato fruits at different loading positions for each compression speed; (c) peak force of tomato fruits at different loading positions for each compression speed; (d) loading slope of tomato fruits at different loading positions for each compression speed. T × CW: loading position over a cross wall of three locule fruits; F × L: loading position over locular tissue of four locule fruits; F × CW: loading position over a cross wall of four locule fruits. The error bars represent 95% confidence limits.

TABLE 1 Size, shape, and mass of tomato fruits (mean value ± 95% confidence limits)

	Loading speed (mm s^−1)
	0.5	1.5	2.5	3.5	Overall
Number of fruits	15	15	15	15	60
Φ	0.87 ± 0.04	0.88 ± 0.02	0.83 ± 0.04	0.88 ± 0.03	0.87 ± 0.03
Dg (mm)	68.28 ± 2.69	68.16 ± 2.66	69.58 ± 5.31	71.71 ± 5.54	69.43 ± 4.05
Da (mm)	68.67 ± 2.76	68.44 ± 2.69	70.19 ± 5.31	70.05 ± 5.61	69.34 ± 4.09
M (g)	187.87 ± 22.77	179.47 ± 24.56	199.27 ± 21.04	192.52 ± 22.31	189.78 ± 22.67

Φ-sphericity, D_g-geometric mean diameter, D_a-arithmetic mean diameter, M-mass.

TABLE 2 Model 1, 2, and 3 with E_c, F_max, r_k as the dependent variable, respectively

Variable	Parameter estimate	t value	Probability > |t|	Tolerance
Model 1: Ec = β + α1 × CS + α2 × LN. Analysis of variance: F value: 25, Pr.: 0.0002, = 0.82
Intercept	β = 4.2	3.78	0.004
CS (mm s^−1)	α1 = 2.4	5.86	0.0002	1.00
LN	α2 = 3.9	4.09	0.003	1.00
Regression diagnostics: Chi-squared test: 4.07, Pr.: 0.40, Durbin-Watson D value: 2.15
Model 2: Fmax = β + α1 × CS + α2 × LN. Analysis of variance: F value: 21, Pr.: 0.0004, = 0.78
Intercept	β = 7.4	7.57	<0.0001
CS (mm s^−1)	α1 = 2.0	5.69	0.0003	1.00
LN	α2 = 2.5	3.05	0.01	1.00
Regression diagnostics: Chi-squared test: 3.70, Pr.: 0.45, Durbin-Watson D value: 2.183
Model 3: rk = β + α1 × CS. Analysis of variance: F value: 20, Pr.: 0.001, = 0.63
Intercept	β = 5.0	10.47	<0.0001
CS (mm s^−1)	α1 = 0.9	4.46	0.001	1.00
Regression diagnostics: Chi-squared test: 0.18, Pr.: 0.91, Durbin-Watson D value: 1.959

E_c: compression energy (mJ); F_max: peak force (N); r_k: loading slope (N m⁻¹); CS: compression speed (mm s⁻¹); LN: dummy variable for locular number was set at 0 for a three locule fruits and at 1 for a four locule fruits.

TABLE 3 Pearson correlation coefficient matrix for the mechanical parameters

	Ec	Fmax	rk
Ec	1
Fmax	0.9541 (Probability < 0.0001)	1
rk	0.6436 (Probability = 0.024)	0.7366 (Probability = 0.0063)	1

E_c: compression energy (mJ); F_max: peak force (N); r_k: loading slope (N m⁻¹).