Evaluation of strawberry texture in close relation with their anisotropy

Figures & data

Figure 1. Device for determining the food anisotropy: 1: metal box; 2: video camera; 3: capture and shielding con; 4: thick glass disc; 5: food sample; 6: ring of LEDs; 10: compression discs; 13: electronic power source; 14: PC.

Figure 2. The testing direction and the preparation of the strawberry samples for the anisotropy measurement.

Table 1. Physico-chemical and color parameters of strawberry samples.

Sample		pH	°Brix	Moisture [% wb]	L*	a*	b*	C*	h°
Coral	Nearly ripe	4.02 ± 0.01^b	9 ± 0.05^ef	98.3^a ± 0.51	98.23^a ± 0.51	2^bc ± 0.2	-0.26^de ± 0.20	1.92 ± 0.4^c	–8 ± 0.2^g
	Ripe	4.01 ± 0.02^b	9.4 ± 0.10^de	90.3^c ± 0.57	90.26^c ± 0.56	2.16^bc ± 0.30	0.56^cd ± 0.64	2.24 ± 0.5^c	15 ± 0.52^f
	Over ripe	4 ± 0.02^b	10.2 ± 0.11^bc	84.2^e ± 0.7	84.2^e ± 0.7	4.03^a ± 0.15	2.06^b ± 0.25	4.53 ± 0.68^b	27.12 ± 0.23^d
Darselect	Nearly ripe	4.21 ± 0.04^a	8.4 ± 0.13^f	98.1^a ± 0.85	98.1^a ± 0.84	2.75^b ± 0.21	–0.55^e ± 0.35	2.80 ± 0.52^bc	–11.31 ± 0.35^h
	Ripe	3.95 ± 0.02^b	9.8 ± 0.22^cd	94.6^b ± 0.2	94.6^b ± 0.2	1.4^c ± 0.36	1.7^b ± 0.43	2.20 ± 0.29^c	50.53 ± 0.38^b
	Over ripe	4.22 ± 0.01^a	10.6 ± 0.45^b	88.3^d ± 0.44	88.3^d ± 0.43	4.5^a ± 1.4	1.43^bc ± 0.66	4.72 ± 0.90^b	17.66 ± 1.02^e
Elsanta	Nearly ripe	3.81 ± 0.05^c	9 ± 0.18^ef	99.2^a ± 0.71	99.5^a ± 0.70	2.25^b ± 0.5	–0.6^e ± 0.14	2.32 ± 0.54^c	–15 ± 0.33^i
	Ripe	3.92 ± 0.06^bc	10.3 ± 0.16^bc	95.1^b ± 0.82	95.1^b ± 0.81	2^bc ± 0.26	1.33^bc ± 0.23	2.32 ± 0.68^c	35.05 ± 0.21^c
	Over ripe	4.01 ± 0.08^b	14.2 ± 0.24^a	89.6^cd ± 0.05	89.65^cd ± 0.5	4.1^a ± 0.4	5.6^a ± 1.0	7 ± 0.86^a	54 ± 0.8^a

*Values are the average of triplicates ± standard deviation.

Different letters in each row show the significant statistical difference between the samples.

L*: brightness; a*: red–green axis; b*: yellow–blue axis; C*: color intensity; h°: tone.

Table 2. The color difference.

Sample		ΔE
Coral	Nearly ripe – Ripe	8 ± 1
	Ripe – Over ripe	6.5 ± 1.15
	Over ripe – Nearly ripe	14.5 ± 1.0
Darselect	Nearly ripe – Ripe	5.1 ± 1.05
	Ripe – Over ripe	7.3 ± 1
	Over ripe – Nearly ripe	12 ± 1
Elsanta	Nearly ripe – Ripe	4 ± 0.73
	Ripe – Over ripe	7 ± 1.2
	Over ripe – Nearly ripe	10.4 ± 1.8

*Values are the average of triplicates ± standard deviation.

Table 3. The anisotropy coefficient of elsanta, darselect and coral strawberry.

Sample		Pa+b [mm]	Pc+d [mm]	Ka
Coral	Nearly ripe	45.02 ± 0.20	41.15 ± 0.30	1.094
	Ripe	53 ± 0.12	51.42 ± 0.21	1.030
	Over ripe	54.9 ± 0.10	54.33 ± 0.02	1.010
Darselect	Nearly ripe	65.5 ± 0.050	53.45 ± 0.35	1.224
	Ripe	69 ± 0.43	55.32 ± 0.21	1.246
	Over ripe	79.53 ± 0.30	60.19 ± 0.29	1.260
Elsanta	Nearly ripe	59 ± 0.24	52.86 ± 0.31	1.115
	Ripe	53.25 ± 0.12	50.84 ± 0.15	1.047
	Over ripe	63.7 ± 0.2	63.18 ± 0.08	1.008

*Values are the average of triplicates ± standard deviation.

P_a+b: the highest amount of two opposing ellipse segments; P_c+d: the lower amount of the other two ellipse segments; K_a: anisotropy coefficient.

Table 4. Textural properties of elsanta, darselect and coral strawberry.

Sample Texture paramete		Hardness [N]	Fracturability [N]	Viscosity [N]	Adhesiveness[N∙mm]	Elasticity	Cohesiveness	Gumminess [N]	Chewiness [N]	Penetrationdepth [mm]	Work [mm∙s]
Coral	Nearly ripe	8.62 ± 0.31	0.85 ± 0.041	0.263 ± 0.02	1.1 ± 0.15	0.267 ± 0.031	0.089 ± 0.07	0.705 ± 0.059	0.157 ± 0.07	7.71 ± 0.41	236.5 ± 2
	Ripe	6.63 ± 0.44	0.62 ± 0.021	0.536 ± 0.014	1.964 ± 0.287	0.244 ± 0.04	0.074 ± 0.01	0.478 ± 0.040	0.110 ± 0.011	8.22 ± 0.4	256 ± 1
	Over ripe	4.20 ± 0.70	0.42 ± 0.014	0.444 ± 0.02	2.068 ± 0.026	0.169 ± 0.06	0.051 ± 0.07	0.214 ± 0.035	0.035 ± 0.06	9.37 ± 0.17	288 ± 1.7
Darselect	Nearly ripe	44.38 ± 0.54	0.61 ± 0.056	0.147 ± 0.018	0.180 ± 0.03	0.312 ± 0.03	0.135 ± 0.07	4.886 ± 0.318	1.018 ± 0.096	2.23 ± 0.12	68 ± 0.7
	Ripe	27 ± 1.4	1.05 ± 0.084	0.997 ± 0.070	2.519 ± 0.41	0.254 ± 0.02	0.106 ± 0.03	2.298 ± 0.083	0.376 ± 0.022	2.44 ± 0.16	72 ± 1.8
	Over ripe	20.21 ± 1.2	1.38 ± 0.070	0.202 ± 0.014	0.347 ± 0.03	0.247 ± 0.02	0.103 ± 0.03	1.658 ± 0.065	0.258 ± 0.015	3.18 ± 0.15	100 ± 2.1
Elsanta	Nearly ripe	14.12 ± 1.76	2.05 ± 0.028	0.112 ± 0.014	0.120 ± 0.01	0.255 ± 0.01	0.119 ± 0.01	1.514 ± 0.035	0.311 ± 0.006	5.31 ± 0.35	160 ± 1
	Ripe	10 ± 0.8	1.05 ± 0.011	0.333 ± 0.001	0.852 ± 0.02	0.222 ± 0.05	0.080 ± 0.02	0.763 ± 0.055	0.154 ± 0.016	6.91 ± 0.47	206 ± 1.5
	Over ripe	7.82 ± 0.6	1.38 ± 0.028	0.478 ± 0.002	0.346 ± 0.04	0.194 ± 0.06	0.076 ± 0.02	0.588 ± 0.035	0.112 ± 0.010	7.61 ± 0.32	234 ± 2

*Values are the average of triplicates ± standard deviation.

Table 5. Pearson corelation matrix between the textural, physico-chemical and color parameters.

	H	F	V	A	E	Co	G	Ch	pH	°B	M	L*	a*	b*	C*	h°	P	W	Ka
H	1	–0.055	–0.071	–0.252	0.764(**)	0.842(**)	0.989(**)	0.960(**)	–0.258	–0.379	–0.729(*)	0.435	–0.136	–0.355	–0.208	–0.261	–0.895(**)	–0.894(**)	0.810(**)
F		1	–0.255	–0.559	0.049	0.395	–0.057	–0.089	–0.042	0.255	0.396	0.341	0.035	0.066	0.128	–0.074	–0.261	–0.270	0.171
V			1	0.818(**)	–0.267	–0.299	–0.168	–0.241	–0.840(**)	0.224	–0.302	–0.276	–0.299	0.410	–0.021	0.740(*)	–0.024	–0.025	0.021
A				1	–0.303	–0.500	–0.319	–0.360	–0.610(*)	–0.162	–0.257	–0.368	–0.337	0.063	–0.275	0.427	0.249	0.251	–0.134
E					1	0.872(**)	0.781(****)	0.791(****)	–0.084	–0.634(*)	–0.755(**)	0.758(**)	–0.472	–0.713(*)	–0.592(*)	–0.636(*)	–0.699(*)	–0.695(*)	0.682(*)
Co						1	0.854(**)	0.836(**)	–0.166	–0.428	–0.558	0.725(*)	–0.274	–0.525	–0.346	–0.510	–0.869(**)	–0.870(**)	0.781(**)
G							1	0.990(**)	–0.160	–0.412	–0.714(*)	0.482	–0.137	–0.401	–0.219	–0.356	–0.840(**)	–0.839(**)	0.739(*)
Ch								1	–0.067	–0.438	–0.707(*)	0.521	–0.155	–0.438	–0.241	–0.427	–0.765(**)	–0.765(**)	0.651(*)
pH									1	0.058	0.482	–0.132	0.495	–0.086	0.274	–0.468	0.427	0.435	–0.414
B										1	0.532	–0.490	0.552	0.963(**)	0.859(**)	0.731(*)	0.269	0.271	–0.366
M											1	–0.499	0.561	0.440	0.533	0.225	0.563	0.559	–0.553
L												1	–0.712(*)	–0.610(*)	–0.653(*)	–0.554	–0.410	–0.426	0.311
a													1	0.534	0.880(**)	0.181	0.133	0.150	–0.086
b														1	0.846(**)	0.846(**)	0.284	0.285	–0.367
C															1	0.496	0.188	0.198	–0.231
h°																1	0.127	0.123	–0.193
P																	1	0.999(**)	–0.948(**)
W																		1	–0.942(**)
Ka																			1

H: hardness; F: fracturability; V: viscosity; A: adhesiveness; E: elasticity; Co: cohesiveness; G: gumminess; Ch: chewiness; B: Brix concentration; M: moisture content,;L*: brightness; a*: red–green axis; b*: yellow–blue axis; C*: chroma; h°: tone; P: penetration depth; W: mechanical work; K_a: anisotropy coefficient.

*Correlation is significant at the 0.05 level (1-tailed).

**Correlation is significant at the 0.01 level (2-tailed).

Figure 3. A: Elsanta texture profile analysis; B: Darselect texture profile analysis; C: Coral texture profile analysis.

Figure 4. The strawberry anisotropy: A: The anisotropy of Elsanta strawberry; B: The anisotropy of Darselect strawberry; C: The anisotropy of Coral strawberry.

Figure 5. A: Elsanta creep curves; B: Darselect creep curves; C: Coral creep curves.

Figure 6. PCA scores of strawberry samples: p1: nearly ripe; p2: ripe; and p3: over ripe.

Figure 7. PCA loadings of strawberry samples. H: hardness; F: fracturability; V: viscosity; A: adhesiveness; E: elasticity; Co: cohesiveness; G: gumminess; Ch: chewiness; B: Brix concentration; M: moisture content; L*: brightness; a*: red–green axis; b*: yellow–blue axis; C*: chroma; h°: tone; P: penetration depth; W: mechanical work; Ka: anisotropy coefficient.