4. COMPARATIVA SOBRE LAS DISTINTAS DIMENSIONES DE LA EXPANSIÓN JAPONESA Y PRETENSIONES HEGEMÓNICAS CHINAS.
4.4. La política de prestigio internacional y soft power.
physically induced change in firmness. The relative degree of physiological and physical change in firmness between!! and/2 can be estimated from/3, as any physical change in firmness between!! and/2 should be reversed when fruit are returned to oOe
in the/3 treatment. Thus, the difference in firmness between!! and/3 provided an estimate of change in physiological firmness between!! and/2, while the firmness difference between/2 and/3 estimated change in physical firmness between!! and/2. It is possible that some physiological change in firmness occurred between/2 and13 resulting in an underestimation of physical change in firmness. However, physiological change is likely to be minimal as ripening rates for both RG and COP are considerably slower at oOe (13) than at 20°C (j2). As the difference between/2 and/3 appears to be
best for estimating physical change, l1.fremp and I1ttemp were calculated using change in firmness (or tensile strength) between/2 and/3.
Magnitude of change in firmness and tensile strength with fruit temperature varied with time at oOe (3°C for COP) for all cultivars (except PR), where l1.fremp was positive at
harvest, but became negative after 50- 1 00 days of storage. Similarly, there was a tendency for I1ttemp to be slightly positive at harvest and more negative after 50- 1 00 days of storage. The changing physical response of l1.fremp with storage time may explain previous inconsistent findings that did not incorporate storage time as a factor. Blanpied et al. ( 1 978) and Bourne ( 1 982) found a negative l1.fremp, while others found no effect of temperature on firmness (Haller, 1 94 1 ; Saltveit, 1 984). Alternatively, previous
inconsistent results may reflect large variation in ripeness between individual fruit; this would reduce sensitivity for detection of small treatment differences (in this instance, 3- 5 N). In future texture-temperature studies, experimental sensitivity could be improved through repeated measurements on the same fruit across different temperatures using non-destructive devices, or by using internal ethylene concentration or other ripening related compounds as covariates during statistical analysis.
Positive l1.fremp after 1 -3 days at oOe for RG and GS, and 3°C for COP, could be due to
cortical fruit tissue being more brittle under the compressive and fracturing forces of the penetrometer probe at oOe than at 20°C, resulting in lower firmness readings at oOe than
tissue more brittle at 0-3°e at harvest has not been elucidated, but it may be a
consequence of high fruit water status and associated high cell turgor characteristic of recently harvested fruit. The hypothesis that fruit water status has a role in generating a positive
I!!./r.emp
at harvest is supported by the finding that firmness differences between fruit at 20 and oOe were alleviated by fruit paring, and consequent rapid water loss from fruit at oOe (Fig. 3-5). It is likely that pared fruit had reduced cell turgor from localised rapid water loss, and consequently had less brittle cells and higher firmness readings than intact fruit that probably had higher cell turgor at O°e. Tissue brittleness at low temperatures may be reduced with time at 0-3°e through water loss, accounting for the gradual loss of a positiveI!!./r.emp
in the first 10-25 days at 0 or 3°e.The mechanism for development of a negative
I!!.fr.emp
after 50- 1 00 days at oOe (3°e for eOP) has not been identified in apples, but it has been suggested that a negativeI!!./r.emp
for peaches could be caused by temperature-induced changes in the viscosity of water soluble pectin (Werner and Frenkel, 1 978). Assuming that the same mechanism in peaches is also responsible for a negativeI!./r.emp
in apples, the development of a negativeI!./r.emp
after 50- 1 00 days at 0 or 3°e could be explained by an increased proportion of water-soluble pectin that occurs during apple ripening (Knee, 1 973; Knee, 1 978).I!!./r.emp
not only varied with time at oOe (3°e for eOP), but also between cultivars. eop and RG had the most positiveI!!./r.emp
1-3 days after harvest, followed by GS, butI!!./r.emp
for PR did not differ from -0. After 50- 100 days at oOe (3°e for eOP), eop had the most negativeI!!.fr.emp,
followed by RG and GS, but againI!!./r.emp
for PR did not differ from zero. Bourne ( 1 982) also reported firmness-temperature coefficient variation between apple cultivars (Golden Delicious, -0.73%; Idared, -0.32%; Red Delicious, -0.20%; McIntosh, -0.39%; and Rome, -0.08%). The mechanism for cultivarI!./r.emp
differencesis not known, although it is possible that cultivar differences in cell wall composition and cell packing may exist that facilitate
I!.fr.emp
differences. The structuralcharacteristics of PR have not been compared to cultivars used in this study. However, PR has smaller cells, higher cell number and more intercellular spaces than its parents 'Splendour' and 'Gala' (Opara, 1999).
Chapter 3 Physical change in texture: 72 Orchard and harvest maturity did not affect magnitude of
tl/temp
1 -3 days after harvest (Tables 3-1 and 3-2), indicating that a mean!:!./temp
for a given cultivar could be used across the New Zealand apple industry to estimate temperature induced physical changes in firmness at harvest. Similarly, change intl/temp
with time at lowtemperatures for RG, PR, GS and COP was consistent for two orchards harvested in different seasons (Fig. 3-3); this creates potential for estimating temperature induced physical changes in firmness through storage for a given cultivar from all orchards. As
tl/temp
was linear between 0 and 20°C at harvest and during storage (Fig. 3-4), it is possible that onetl/temp
value for a given storage time could be used to compare firmness readings from fruit measured at different temperatures between 0 and 20°e.In summary, the physical textural response of apples to temperature differed in magnitude between cultivars, texture test, and storage time at O°C or 3°e. Change in firmness associated with change in fruit temperature was not affected by orchard or maturity at harvest, indicating that a cultivar and storage-time specific
tl/temp
could be used to compare firmness readings for fruit from different orchards that were measured at different temperatures between 0 and 20°e. Similar studies are required to quantify the physical effect of temperature on firmness readings for other commerciallyimportant cultivars.
3.6 References
B lanpied, G.D., Bramlage, WJ., Dewey, D.H., LaBelle, R.L., Massey, L.M., Mattus, G.E., Stiles, W.e., Watada, A.E., 1 978. A standardized method for collecting apple pressure test data. N. Y. Food Life Sci. Bull. 74, 8pp, Comell University, Ithaca, New York. Boume, M.C., 1 982. Effect of temperature on firmness of raw fruits and vegetables. J. Food
Sci. 47, 440-444.
HaIler, M.H., 1 94 1 . Fruit pressure testers and their practical applications. USDA Circular 627.
Harker, F.R., HaIlett, Le., 1 992. Physiological changes associated with development of mealiness of apple fruit during cool storage. HortScience 27, 1 29 1 - 1 294.
Harker, F.R., Redgwell, RJ., Hallett, Le., Murray, S .H., 1 997a. Texture of fresh fruit. Hortic. Rev. 20, 1 2 1 -224.
Harker, ER., Stec, M.G.H., Hallett, Le., Bennett, e.L., 1 997b. Texture of parenchymatous plant tissue: a comparison between tensile and other instrumental and sensory
measurements of tissue strength and juiciness. Postharvest BioI. Technol. 1 1 , 63-72. Jeffery, P.B ., Banks, N.H., 1 994. Firmness-temperature coefficient of kiwifruit. New Zeal. J.
Crop Hort. Sci. 22, 97- 1 0 1 .
Knee, M., 1 973. Polysaccharide changes in cell walls of ripening apples. Phytochemistry 1 2, 1 543- 1 549.
Knee, M., 1 978. Metabolism of polymethylgalacturonate in apple fruit cortical tissue during ripening. Phytochemistry 1 7, 1 26 1 - 1 264.
Opara, L.V., 1 999. Bruise susceptibility and other postharvest quality attributes of Pacific Rose' apple and its parents. Paper presented: "Australasian Postharvest Conference", Waitangi, New Zealand, 3-8 October 1 999.
Saltveit, M .E., 1 984. Effects of temperature on firmness and bruising of 'Starkrimson Delicious' and 'Golden Delicious' apples. HortScience 1 9, 550-55 1 .
Stow, J., 1 989. The involvement of calcium ions in maintenance of apple fruit tissue structure.
J . Exp. Bot. 40, 1 053- 1 057.
Werner, R.A., Frenkel, C., 1 978. Rapid changes in the firmness of peaches as influenced by temperature. HortScience 1 3, 470-47 1 .
Chapter 4