‘Hass’ avocado (Persea americana) is the main internationally traded avocado fruit cultivar. With increasing global demand, and increasing numbers of suppliers, increasing volumes of fruit are being shipped between countries. In this global marketplace, New Zealand is a minor producer, yet its exporters are looking to diversify from the traditional Australian market to more distant markets as production volumes increase. Overall, New Zealand-grown fruit quality tends to be best ≈10–12 months postflowering, with a greater risk to quality earlier or later in the season, associated with less mature or more mature fruit (Burdon et al., 2013; Dixon et al., 2004).
The avocado fruit is chilling sensitive, with potential for both flesh and skin disorders to occur at low temperature (Chaplin et al., 1983; Hofman et al., 2002). Traditional shipping at about 5 °C risks the development of CI. Irrespective of CI, if fruit are stored in air for longer than 30 d, the ripe fruit quality tends to decline (Dixon et al., 2003, 2004). Hence, the overall capacity for ‘Hass’ avocado fruit to be stored, or distributed over long distances, is limited. The inherent storage life, which declines with maturity, and not being able to cool the fruit to the same degree as fruit such as apples and kiwifruit, which may be stored at, or close to, 0 °C, both limit storage life.
The association between poor quality and fruit age beyond 30 d can be improved by the use of CA in combination with refrigerated storage, with potential for good ripe fruit quality to be maintained for 6–8 weeks (Burdon et al., 2008). The value in using CA for shipping avocado fruit has long been recognized, with a range of research reported along with recommendations for atmospheres to use (Kader, 2003; Thompson, 2010).
‘Hass’ avocado is a typical climacteric fruit (Kader, 2002) in which there is a preclimacteric period before the ripening occurs and is associated with a climacteric increase in ethylene production and respiration. The preclimacteric period decreases the longer fruit are left on the tree, leading to the reduction in time to ripen as the fruit matures. CA storage retards the progression to ripening by extending the preclimacteric period at storage temperatures beyond that achieved by refrigeration alone. However, the maximum storage life achieved under CA may not always be needed to reach target markets. The storage life required when shipping from New Zealand is in the range 2–6 weeks, allowing export to Australia or Europe. As a result, it may be possible to remove the risk of chilling damage to the fruit by increasing the storage temperature slightly and by relying on the CA to provide adequate storage life.
In this project, the postharvest performance of ‘Hass’ avocado has been compared under CA at 5 °C or 7 °C. An additional sample of fruit was stored in air at 5 °C to provide the current non-CA practice for comparison.
Burdon, J., Connolly, P., de Silva, N., Lallu, N., Dixon, J. & Pak, H. 2013 A meta-analysis using a logit non-linear mixed effects model for ‘Hass’ avocado postharvest performance data Postharvest Biol. Technol. 86 134 140
Burdon, J., Lallu, N., Haynes, G., Francis, K., Patel, M., Laurie, T. & Hardy, J. 2015 Relationship between dry matter and ripening time in ‘Hass’ avocado Acta Hort. 1091 291 296
Burdon, J., Lallu, N., Haynes, G., McDermott, K. & Billing, D. 2008 The effect of delays in establishment of a static or dynamic controlled atmosphere on the quality of ‘Hass’ avocado fruit Postharvest Biol. Technol. 49 61 68
Chaplin, G.R., Wills, R.B.H. & Graham, D. 1983 Induction of chilling injury in stored avocados with exogenous ethylene HortScience 18 952 953
Dixon, J. 2003 New Zealand avocado fruit assessment manual. Version 3.0. Avocado Industry Council Limited
Dixon, J., Pak, H.A., Mandemaker, A.J., Smith, D.B., Elmsly, T.A. & Cutting, J.G.M. 2003 Fruit age management: The key to successful long distance export of New Zealand avocados NZ Avocado Growers’ Assoc. Ann. Res. Rep. 3 60 665
Dixon, J., Smith, D.B. & Elmsly, T.A. 2004 Fruit age, storage temperature and maturity effects on Hass avocado fruit quality and ripening NZ Avocado Growers Assoc. Ann. Res. Rep. 4 47 53
Everett, K.R., Hallett, I.C., Rees-George, J., Chynoweth, R.W. & Pak, H.A. 2008 Avocado lenticel damage: The cause and the effect on fruit quality Postharvest Biol. Technol. 48 383 390
Hofman, P.J., Fuchs, Y. & Milne, D.L. 2002 Harvesting, packing, postharvest technology, transport and processing, p. 363–401. In: A.W. Whiley, B. Schaffer and B.N. Wolstenholme (eds.). The avocado: Botany, production and uses. CAB International, Wallingford, UK
Kader, A.A. 2002 Postharvest technology of horticultural crops. 3rd ed. Univ. California Agriculture and Natural Resources. Publication 3311
Lee, S.K., Young, R.E., Schiffman, P.M. & Coggins, C.W. 1983 Maturity studies of avocado fruit based on picking dates and dry weight J. Amer. Soc. Hort. Sci. 108 390 394
Thompson, A.K. 2010 Controlled atmosphere storage of fruits and vegetables. 2nd ed. CAB International, Wallingford, UK