The effects of two nonchemical methods [controlled atmosphere (CA) storage and postharvest heating, alone or combined] on the quality (firmness, taste, color, and skin wax) and storability (losses resulting from bruising and fungal decay) of apples were investigated in a 3-year study. Fruits of two cultivars (cv. Aroma and cv. Ingrid Marie) were mechanically wounded on two opposing sides, inoculated with conidial suspensions of one of three pathogens [Pezicula malicorticis (bull's eye rot), Penicillium expansum (blue mould), and Colletotrichum gloeosporioides (bitter rot)], exposed to 40 °C for four different exposure periods (24, 48, 72, and 96 h), and stored either in air (21.0 kPa O2 + 0.03 kPa CO2) or in CA storage (2.0 kPa O2 + 2.0 kPa CO2) for 4 months. Effect of postharvest heating on bruise susceptibility of air- or CA-stored apples was also investigated. Cultivar Aroma apples generally showed higher bruise susceptibility than cv. Ingrid Marie. The sun-exposed side of apples was less sensitive to bruising than the shaded side and red phenotypes of these two cultivars also showed increased resistance to bruising as compared with standard phenotypes. Heat treatment and CA storage, either alone or in combination, decreased bruise occurrence in both cultivars. Pz. malicorticis was the more aggressive storage pathogen for both apple cultivars followed by P. expansum and C. gloeosporioides. The highest decay severity occurred in inoculated and nonheat-treated apples stored in air. Heat treatment, especially in combination with CA storage, showed an eradicative effect on the pathogens without any negative effects on apple quality. Heat treatment maintained flesh firmness during storage, reduced ethylene production, and caused clearly visible changes in epicuticular wax structure, resulting in a higher resistance to bruising or to natural and artificial infections with the pathogens. The effective exposure period could be reduced to 24 h, because a combination of heat treatment (at 40 °C for 24 h) and CA storage showed the best protective effect against bruising and fungal decay. This combined treatment decreased bull's eye rot by 86% and 60% and bitter rot by 73% and 65% in cv. Aroma and cv. Ingrid Marie, respectively, in comparison with untreated apples.
Ibrahim I. Tahir, Eva Johansson, and Marie E. Olsson
Jinhe Bai*, Paul Chen, Elizabeth Baldwin, and James Mattheis
`Bartlett' pears were treated with 300 nL·L-1 1-MCP at 20°C for 24 h shortly after harvest, and were stored at -1 °C in either regular atmosphere (RA) or controlled atmosphere (CA: 1.5 kPa O2 / 0.5 kPa CO2). After 2 and 4 months of RA storage, or 4 months of CA storage, fruit were pre-conditioned at 10 °C, 15 °C or 20 °C for 5, 10, or 20 days, respectively. Pre-conditioned fruit were then held at 20 °C for 14 days to simulate marketing conditions. Flesh firmness (FF) and extractable juice (EJ) were monitored during the marketing period. The optimal stage of ripeness for `Bartlett' pears was defined to be when FF decreases to 27 N and EJ decreases to 55 mL/100 g. The proper pre-conditioning combinations of temperature and duration were 15 °C or 20 °C for 10 d or 10 °C for 20 d if the fruit had been stored in RA for 2 months, 10 °C or 15 °C for 5 d if the fruit had been in RA for 4 months, and 20 °C for 10 d or 10°C for 20 d if the fruit had been in CA for 4 months, for which combinations the fruit ripened within a week and maintained quality for 14 days at 20 °C. The treatment combinations of lower temperature and/or shorter duration times in pre-conditioning delayed the ripening response of the fruit, and combinations of higher temperature and/or longer duration times in pre-conditioning resulted in a shorter marketing life because of senescence breakdown, in comparison the optimal combinations mentioned above. These results indicate that pre-conditioning regimes for 1-MCP treated `Bartlett' pears are storage atmosphere and time dependent. Generally, CA stored fruit needed more preconditioning (in terms of higher temperature and/or longer duration) than did RA stored fruit.
C.B. Watkins and J.F. Nock
The inhibitor of ethylene binding, 1-methylcyclopropene (1-MCP) has been applied to `Gala', `Cortland', `McIntosh', `Empire', `Delicious', `Jonagold', and `Law Rome' apples under air and/or controlled atmosphere (CA) storage conditions. 1-MCP gas concentrations ranged from 0 to 2 mL·L–1. Effects of 1-MCP were greater in CA than air storage. A dose response of internal ethylene concentrations and flesh firmness to 1-MCP was found in cultivars such as `McIntosh' and `Law Rome', whereas in others, such as `Delicious' and `Empire', ripening was generally prevented by all 1-MCP concentrations. We have further investigated the effects of 1-MCP on `McIntosh' by increasing rates of the chemical to 50 mL·L–1, and confirming that fruit of this cultivar respond poorly if fruit have entered the climacteric prior to 1-MCP application. Efficacy of 1-MCP is affected by cultivar and storage conditions, and that successful commercial utilization of the chemical will require understanding of these relationships.
Christopher J. Clark and Douglas M. Burmeister
Development of browning induced in `Braeburn' apple (Malus ×domestica Borkh.) fruit by a damaging CO2 concentration was monitored weekly using magnetic resonance imaging (MRI) during a 4-week storage trial (0.5 °C, 2 kPa O2/7 kPa CO2). Discrete patches of high-intensity signal, distributed randomly throughout the fruit, were observed in multislice images of samples after 2 weeks of storage; these patches were eventually confirmed as being sites of browning reactions after dissection at the end of the trial. Subsequently (weeks 3 and 4), signal intensity at sites of incipient damage increased and patches enlarged and coalesced. After 2 weeks of storage, the extent of affected tissue, averaged across all image slices, was 1.5%, increasing to 15.9% and 21.3% after 3 and 4 weeks. The average rate at which tissue damage spread in individual slices was 0.81 (range: 0–3.70) cm2·d–1 between weeks 2 and 3, declining to 0.32 (range: 0–1.55) cm2·d–1 in the final week. Tissue damage induced under these conditions did not spread at the same rate at all locations within individual fruit, nor was it preferentially located toward the stem or calyx ends of the fruit.
David Rudell, James Mattheis, and John Fellman
Diphenylamine (DPA) is used for superficial scald control in apple fruit. A number of DPA derivatives resulting from C-nitration, C-hydroxylation, O-methylation, and N-nitrosation can be present in DPA-treated apple fruit after storage. The presence of the compounds may be indicative of metabolic processes that lead to scald development. Therefore, apple peel DPA and DPA derivative content in fruit treated at harvest with DPA or DPA plus 1-methylcyclopropene (1-MCP) was assayed upon removal of fruit from controlled atmosphere (CA) and regular atmosphere (RA) storage and during a 14-d post-storage ripening period. Apples were also treated at harvest with different concentrations of DPA and assayed after 6 months CA storage to confirm recovery of DPA and DPA derivatives is linear over a wide concentration range. Harvest maturity notably affected peel DPA and 4-hydroxydiphenylamine (4OHDPA) content. Post-storage ripening, 1-MCP treatment, and CA storage had varied affects on DPA derivative content, suggesting reactive oxygen or nitrogen species, such as •OH, •NO, and •NO2, or enzyme catalyzed reactions may be generated during ripening and senescence related physiological processes. Consistent correlations between scald incidence and content of specific derivatives were not observed.
Mark D. Shelton, Victor Mendez, Virginia R. Walter, and David Brandl
Refrigerated (2 °C) controlled atmospheres significantly increased the mortality of green peach aphids [Myzus persicae (Sulzer)] and western flower thrips [Frankliniella occidentalis (Pergande)] in laboratory experiments. However, insect mortality during marine shipment in mixedload containers at 0.5 °C did not significantly increase in a controlled atmosphere. In laboratory experiments, mortality of green peach aphids ranged from 32.8% in the refrigerated control to 96.8% after storage in 0.10% O2 for 4 d followed by 7 d in 3% O2 with 5% CO2. When stored under these same conditions, western flower thrips mortality was 71% compared to 16% mortality in the refrigerated control. Following an 11-day marine shipment from California to Guam in a controlled atmosphere, vase life was extended for most of the 20 California cut-flower and foliage products compared to those shipped in the refrigerated air control.
A. Brackmann, J. Streif, and F. Bangerth
`Golden Delicious' apples (Malus domestica Borkh.) harvested at the preclimacteric and climacteric stages of ripening were stored for up to 8 months at 1C in air and under various controlled atmosphere(s) (CA), including ultralow oxygen (ULO) storage conditions. Aroma volatiles were measured at 2-month intervals in fruit ripened for 10 days at 20C. Fruits harvested at the climacteric stage produced more volatiles during all storage conditions than preclimacteric fruit. All CA storage treatments suppressed aroma production compared to cold storage. The greatest reduction was found under ULO (1% O2) and high CO2 (3%) conditions. A partial recovery of aroma production was observed when CA fruits were subsequently stored for 14 days under cold storage conditions. Suppression of aroma production under ULO conditions seems to be related to low fatty acid synthesis and/or degradation, and is restricted to volatiles having a straight C chain. Production of branched C-chain aroma compounds was suppressed by high CO2 concentrations. The reduced capacity of aroma production during shelf life after ULO storage is confined to apple cultivars producing mainly ester compounds with a straight C-chain, e.g., `Golden Delicious'.
Kathleen Evensen, Philip Hammer, Robert Crassweller, George Greene, and Laura Lehman-Salada
We present a method for predicting firmness of `York Imperial' apples after air or controlled-atmosphere storage. Firmness and soluble solids content in freshly harvested fruit can be plotted on a graph showing a “decision line.” If the prestorage firmness and soluble solids coordinates for a given sample are above the decision line, then firmness after storage is predicted to be greater than the target value. Prestorage flesh firmness and soluble solids content were the best predictors of poststorage firmness. There was no significant improvement in firmness prediction when ethylene, starch, or other indicators of maturity were included.
S.R. Drake and T.A. Eisele
Red color of two strains of `Delicious' apples was increased (25%) by a 10-day delay beyond recommended harvest date for long-term controlled atmosphere (CA) storage. Soluble solids content (SSC) and size also increased, but, depending on strain, up to 12% of firmness was lost at harvest with a 10-day delay. In 2 of 3 years, firmness values in all strains were 73 N or greater, and these fruit lost little firmness during 9 months of CA storage. Soft fruit (<63 N) at harvest resulted in unacceptable firmness after storage, regardless of harvest time or strain of `Delicious'. Immediate (<24 h) establishment of CA conditions resulted in good-quality fruit after storage. Quality loss was evident after a 5-day delay in atmosphere establishment, with no further loss after a 10-day delay. `Oregon Spur' apples had the best red color regardless of harvest. Sensory panel profiles were unable to distinguish among strains, harvest dates, or delays in time of atmosphere establishment. Caution should be exercised when initiating new harvest or storage procedures because growing conditions can vary from one location to another.
Steve J. McArtney, John D. Obermiller, James R. Schupp, Michael L. Parker, and Todd B. Edgington
cultivars to postharvest application of 1-methylcyclopropene (1-MCP) under air and controlled atmosphere storage conditions Postharvest Biol. Tech. 19 17 32 Whitaker, B.D. Solomos, T. Harrison, D.J. 1997