Chapter 2 The relationships between sugars, protein and oil of ‘Hass’
5. Conclusion
Mannoheptulose and perseitol appear to be a major carbon source in avocado fruit and an important energy source, especially for protein synthesis. The management of the respiration rate during postharvest handling, cold storage and ripening to limit the loss of these sugars is important to reduce the risk of fruit not achieving eating ripeness and developing internal disorders.
86 Table 2: P-values for REML analysis for time, harvest and the interaction between time and harvest for fruit harvested thrice from a commercial orchard near Tzaneen and (warm subtropical climate) another near Howick (cool subtropical climate) South Africa in the 2007 season.
EPR, Ethylene production rate; Manno, mannoheptulose; Resp, respiration rate.
P-value
Location Factor EPR Firmness Fructose Glucose Heptose Manno Oil Perseitol Protein Resp Sucrose Tzaneen Time <0.001 <0.001 <0.001 0.072 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 Harvest <0.001 0.350 <0.001 <0.001 <0.001 0.007 <0.001 <0.001 0.121 <0.001 <0.001 Time.Harvest <0.001 0.068 <0.001 <0.001 <0.001 0.010 0.234 <0.001 0.158 <0.001 <0.001
Howick Time <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 0.036 <0.001 <0.001 <0.001 0.002 Harvest 0.563 0.130 0.408 0.227 <0.001 <0.001 <0.001 0.012 0.003 <0.001 0.016 Time.Harvest 0.038 <0.001 0.584 0.385 0.007 0.001 0.834 0.041 0.311 <0.001 0.094
87 Table 3: Spearman’s rank correlation co-efficients between, ethylene production rate, firmness, fructose, glucose, heptose, mannoheptulose, oil, perseitol, protein, respiration and sucrose during the ripening of ‘Hass’ avocado fruit. Values are from fruit that were harvested thrice from a commercial orchard near Tzaneen (warm subtropical climate) and another in Howick (cool subtropical climate), South Africa in the 2007 season. Fruit were ripened at 21 ± 2°C.
Location Parameter EPR Firmness Fructose Glucose Heptose Manno Oil Perseitol Protein Resp
Tzaneen Firmness -0.28
Fructose 0.37 -0.46
Glucose 0.18 -0.08 0.41
Heptose -0.38 0.80 -0.44 -0.01
Manno -0.38 0.74 -0.38 -0.01 0.96
Oil 0.10 -0.07 0.08 0.04 -0.14 -0.10
Perseitol -0.34 0.85 -0.48 -0.01 0.85 0.75 -0.19
Protein 0.34 -0.74 0.33 0.07 -0.69 -0.68 0.19 -0.68
Resp 0.21 -0.10 0.18 0.29 -0.11 -0.13 -0.05 -0.07 -0.05
Sucrose 0.05 0.05 0.06 -0.14 -0.03 -0.04 0.01 0.07 0.09 -0.36
Howick Firmness -0.61
Fructose 0.40 -0.47
Glucose 0.14 -0.28 0.42
Heptose -0.67 0.79 -0.54 -0.22
Manno -0.64 0.75 -0.53 -0.21 0.98
Oil 0.10 -0.17 0.03 0.19 -0.05 -0.03
Perseitol -0.64 0.75 -0.50 -0.21 0.91 0.84 -0.10
Protein 0.43 -0.59 0.39 0.24 -0.52 -0.48 0.34 -0.56
Resp -0.07 0.12 -0.18 0.07 0.18 0.14 -0.01 0.24 -0.21
Sucrose 0.07 0.23 0.08 -0.18 0.32 0.33 -0.03 0.27 0.05 -0.26
EPR, Ethylene production rate; Manno, mannoheptulose; Resp, respiration rate.
88 Table 4: Comparison between fast and slow ripening ‘Hass’ avocado fruit from a commercial orchard near Howick (cool subtropical climate) South Africa, averaged for three harvests in the 2007 season. Fruit were ripened at 21 ± 2°C.
Day Postharvest
Ripening Rate 0 3 7 10 13
Firmness Fast1 85.4 ± 1.6 A2,3 76.4 ± 2.7 B 60.2 ± 2.2 C 50.6 ± 3.0 D -
(densimeter units) Slow 86.7 ± 1.6 A 78.0 ± 2.4 B 76.2 ± 1.4 B* 62.7 ± 0.8 C* 58.0 ± 1.2 C
Respiration Fast 2421 ± 62 A 3299 ± 298 B 2999 ± 122 B 1912 ± 128 C -
(μmol.kg-1.h-1 Slow 1577 ± 224 A* 2772 ± 405 B 2555 ± 260 B 1756 ± 161 A 1594 ± 142 A
Ethylene Fast 1.8 ± 1.7 A 137.2 ± 49.3 A 880.1 ± 244.1 B 403.3 ± 104.8 AB -
(μmol.kg-1.h-1) Slow 0.0 ± 0.0 A 215.2 ± 182.0 B 2021.6 ± 376.2 C* 660.3 ± 127.7 D 516.7 ± 151.7 BD
Glucose Fast 0.28 ± 0.17 A 0.82 ± 0.36 AB 1.43 ± 0.26 B 0.91 ± 0.36 AB -
(mg.g-1 DM) Slow 0.07 ± 0.07 A 0.61 ± 0.51 AB 0.52 ± 0.43 AB 1.76 ± 0.56 B 1.09 ± 0.54 AB
Fructose Fast 0.0 ± 0.0 A 0.0 ± 0.0 A 0.61 ± 0.22 A 0.43 ± 0.11 A -
(mg.g-1 DM) Slow 0.0 ± 0.0 AB 0.0 ± 0.0 A 0.62 ± 0.32 ABC 0.62± 0.25 BC 1.09 ± 0.29 C
Sucrose Fast 3.17 ± 0.62 A 2.20 ± 0.47 A 2.56 ± 0.58 A 2.11 ± 0.42 A -
(mg.g-1 DM) Slow 4.29 ± 0.55 A 3.02 ± 0.37 A 3.86 ± 0.48 A 3.91 ± 0.53 A* 2.70 ± 0.79 A
Mannoheptulose Fast 7.93 ± 1.76 A 4.05 ± 1.00 AB 1.01 ± 0.10 B 0.83 ± 0.14 B -
(mg.g-1 DM) Slow 13.97 ± 1.90 A* 8.36 ± 1.52 B 2.49 ± 0.48 BC 1.22 ± 0.18 C 1.31 ± 0.41 C
Perseitol Fast 6.62 ± 1.00 A 2.88 ± 0.63 B 0.59 ± 0.04 C 0.53 ± 0.10 C -
(mg.g-1 DM) Slow 7.76 ± 0.26 A 5.05 ± 0.77 B 1.40 ± 0.40 C 0.49 ± 0.07 C 0.48 ± 0.07 C
Protein Fast 17.74 ± 4.80 A 24.10 ± 5.95 AB 32.94 ± 4.80 BC 35.52 ± 4.81 C -
(mg.g-1 DM) Slow 15.28 ± 2.57 A 21.00 ± 2.02 AB 27.02 ± 2.40 BC 33.68 ± 3.15 C 39.27 ± 5.73 C
1 Fast ripening fruit ripened in 6-7 days after harvest, slow ripening fruit ripened in 12-13 days.
2 Values are means ± SEM; nfast = 5, nslow = 6.
3 Different letters indicate significant differences (P < 0.05) between sampling days.
* Significant difference (P < 0.05) between fast and slow ripening fruit on that sampling day.
Figure 8: Changes in firmness (A-B), respiration rate (C-D) and ethylene production rate (E-F) of South African
‘Hass’ avocados during ripening at 21±2°C in the 2007 season. Three harvests were made from a commercial orchard near Tzaneen (warm subtropical climate; left column) and another near Howick (cool subtropical climate; right column). Vertical bars = SEM; n = 8. Horizontal lines in A and B indicate ripeness.
Figure 9: Changes in the concentrations of glucose (A-B), fructose (C-D), sucrose (E-F), mannoheptulose (G-H), perseitol (I-J) and protein (K-L) in the mesocarp of South African ‘Hass’ avocados during the 2007 season. Three harvests were made from a commercial orchard near Tzaneen (warm subtropical climate; left column) and another near Howick (cool subtropical climate; right column). Vertical bars = SEM; n = 8.
Figure 10: Changes in the concentration of oil in the mesocarp of South African ‘Hass’ avocados during the 2007 season. Three harvests were made from a commercial orchard near Tzaneen (warm subtropical climate; A) and another near Howick (cool subtropical climate; B). Vertical bars = SEM; n = 8.
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