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Hidemi Izumi, Nathanee P. Ko, and Alley E. Watada

Quality and physiology of carrot shreds were monitored during storage in air, low O2 (0.5%, 1%, and 2%), or high CO2 (3%, 6%, and 10%) at 0, 5, and 10C to evaluate the response to controlled-atmosphere (CA) storage. Oxygen uptake and CO2 production from respiration were reduced under low-O2 or high-CO2 atmosphere, the reduction being greater at lower O2 and higher CO2 levels. The respiratory quotient was about 1 with samples in air, more than 1 in low-O2, and less than 1 in high-CO2 atmosphere during storage at all temperatures. No differences were found in ethylene production, which were less than 0.2 μl·kg–1·h–1 with all samples. The CA containing 0.5% O2 and 10% CO2 reduced weight loss and formation of white-colored tissue and decreased pH, but did not affect microbial count and texture at all temperatures. Off-odor and black root rot were not detected in both CA and air atmospheres.

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Dana F. Faubion, Mary Lu Arpaia, F. Gordon Mitchell, and Gene Mayer

Optimum controlled atmosphere (CA) storage conditions were evaluated over a two year period for California-grown `Hass' avocado (Persea americana). Fruit harvests corresponded to early, middle and late season commercial harvests. Various temperatures and CA conditions were tested. The results indicate that the storage life of `Hass' can be extended from 3 to 4 weeks in 5C air, to 9 weeks in 5C CA if they are held in 2% oxygen and 2 to 5% carbon dioxide. Loss of quality as determined by chilling injury expression and flesh softening was greatly reduced in these conditions. Fruit maturity influenced the response to CA storage. Late season fruit had greater loss of quality in storage than earlier fruit. In 2% oxygen and 2.5% carbon dioxide, continuous exposure to ethylene levels as low as 0.1 ppm significantly increased quality loss. Delays in cooling and CA atmosphere establishment of up to three days after harvest did not effect quality.

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Stacey L. Ontai, Robert E. Paull, and Mikal E. Saltveit Jr.

Sugar peas (Pisum sativum var. saccharatum cv. Manoa Sugar) were stored for 14 or 21 days under controlled atmospheres (CA) of 21% or 2.4% O2, plus 0%, 2.6%, or 4.7% CO2 at 10 or 1C. Changes in appearance, weight, and in the concentrations of chlorophyll, total soluble sugars, insoluble solids, and soluble protein were evaluated before and after storage. After 14 days of storage at 10C there were minor changes in all indicators of quality under the various storage conditions, but the appearance of sugar peas was better under CA than under 21% O2. When quality was evaluated after 21 days, however, storage under CA at 10C was not as beneficial as storage in 21% O2, at 1C. Holding peas in 2.4% O2, for up to 3 weeks at l0C, a higher than recommended storage temperature, maintained better quality than 21% O2. Increasing the CO, concentration from 0% to 2.6% or 4.7% had no adverse effects on quality and had a beneficial effect in some treatments. Compared with storage in 21% O2, the appearance of the peas was better, the concentrations of chlorophyll and soluble sugar were maintained at higher levels, and the insoluble solids were decreased in all atmospheres with 2.4% O2. Appearance and concentrations of chlorophyll, soluble sugars, and proteins were maintained at 1C regardless of treatments.

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P. Guy Lévesque, Jennifer R. DeEll, and Dennis P. Murr

Sequential decreases or increases in the levels of O2 in controlled atmosphere (CA) were investigated as techniques to improve fruit quality of `McIntosh' apples (Malus ×sylvestris [L.] Mill. var. domestica [Borkh.] Mansf.), a cultivar that tends to soften rapidly in storage. Precooled fruit that were harvested at optimum maturity for long-term storage were placed immediately in different programmed CA regimes. In the first year, CA programs consisted of 1) `standard' CA (SCA; 2.5–3.0% O2 + 2.5% CO2 for the first 30 d, 4.5% CO2 thereafter) at 3 °C for 180 d; 2) low CO2 SCA (2.5–3.0% O2 + 2.5% CO2) at 3 °C for 60 d, transferred to low O2 (LO; 1.5% O2 + 1.5% CO2) at 0 or 3 °C for 60 d, and then to ultralow O2 (ULO; 0.7% O2 + 1.0% CO2) at 0 or 3 °C for 60 d; and 3) ULO at 3 °C for 60 d, transferred to LO at 0 or 3 °C for 60 d, and then to SCA or low CO2 SCA at 0 or 3 °C for 60 d. In the second year, the regimes sequentially decreasing in O2 were compared with continuous ULO and SCA. After removal from storage, apples were held in ambient air at 20 °C for a 1-week ripening period. Fruit firmness was evaluated after 1 and 7 d at 20 °C, whereas the incidence of physiological disorders was assessed only after 7 d. Lowering the temperature while decreasing O2 was the best CA program with significant increased firmness retention during storage and after the 1-week ripening period. Reduced incidence of low O2 injury in decreasing O2 programs and absence of core browning at the lower temperature were also observed.

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Diana L. Lange and Arthur C. Cameron

The effect of controlled atmospheres (CA) on the development of injury symptoms and storage life of sweet basil (Ocimum basilicum L.) cuttings was assessed. Three-node basil stem cuttings were placed in micro-perforated low-density polyethylene packages and stored in the dark at 20 °C in a continuous stream of nitrogen containing the following percentages of O2/CO2:21/0 (air), 21/5, 21/10, 21/15, 21/20, 21/25, 0.5/0, 0.5/5, 1/0, 1.5/0, 2/0, 1/5, 1.5/5, 1.5/7.5, and 1.5/10. Cuttings stored in an atmosphere of <1% O2 developed dark, water-soaked lesions on young tissue after only 3 days. Fifteen percent or more CO2 caused brown spotting on all tissue. Sweet basil stored in 1.5% O2/0% CO2 had an average shelf life of 45 days compared with 18 days for the air control. None of the CA combinations tested alleviated chilling injury symptoms induced by storage at 5 °C.

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Richard B. Smith

Strawberries (Fragaria × ananassa Duch.) cv. Redcoat were stored at several temperatures and for various intervals in controlled atmospheres (CA) containing 0% to 18% CO2 and 15% to 21% 02. Bioyield point forces recorded on the CA-stored fresh fruit indicated that the addition of CO2 to the storage environment enhanced fruit firmness. Fruit kept under 15% CO2 for 18 hours was 48% firmer than untreated samples were initially. Response to increasing CO2 concentrations was linear. There was no response to changing 02 concentrations. Maximum enhancement of firmness was achieved at a fruit temperature of 0C; there was essentially no enhancement at 21C. In some instances, there was a moderate firmness enhancement as time in storage increased. Carbon dioxide acted to reduce the quantity of fruit lost due to rot. Fruit that was soft and bruised after harvest became drier and firmer in a CO2-enriched environment.

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S.R. Drake and S.K. Ivanov

In 1989 and 1990, `Golden Delicious' apples from controlled-atmosphere (CA) storage (1% O2; 3% CO2) averaged 8.5 N firmer after 30 days and 13.5 N firmer after 60 days of storage than apples from regular-atmosphere (RA) storage. After 7 days of ambient storage, `Golden Delicious' apples from CA storage were 10.3 N firmer than apples from RA storage. Little change in color was evident in `Golden Delicious' apples from CA storage after 30 or 60 days, but a distinct increase in yellow color was evident in apples from RA storage after only 30 days. The quality (color, firmness, and acidity) of `Golden Delicious' apples stored for 30 days under CA and then 30 days under RA was superior to that of `Golden Delicious' apples after 60 days of RA storage and similar to that of `Golden Delicious' apples after 60 days of CA storage. `Granny Smith' apples, traditionally a very firm apple regardless of the type of storage, averaged 3.3 N firmer after 30 days of CA storage (1% O2; 1% CO2) and 5.8 N firmer after 60 days of CA storage when compared to apples from RA storage. Little change in color was evident in `Golden Delicious' apples regardless of storage length, but under ambient storage temperatures, `Golden Delicious' apples from CA storage maintained their green color longer. Titratable acidity of both `Golden Delicious' and `Granny Smith' apples depended on growing season, and neither `Golden Delicious' nor `Granny Smith' apples showed consistent trends in titratable acidity after either RA or CA storage.

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S.R. Drake, T.A. Eisle, and H. Waelti

`Delicious' apples were held in controlled atmosphere (CA) storage at various carbon dioxide (CO2) levels for 9 months. CO2 levels were either 1, 3, or 5% with an additional treatment that was increased by 1% every 6 weeks to a maximum of 5%. For each treatment oxygen was 1%, and storage temperature was 1°C. Little quality difference was noted for the `Delicious' apples immediately after storage or after an 8 day ripening period. Firmness, external or internal color, titratable acidity and amount of scald showed no difference among the different storage treatments. Total carbohydrates and fructose were higher in apples stored at CO2 levels above 1 %. Sensory panelists found no flavor difference in `Delicious' apples regardless of CO2 storage level atmospheres. If one considers the substantial cost savings that are possible with increased CO2 in the storage system, there is good reason to increase the CO2 storage level in long term storage.

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Ahmed F. El-Shiekh and David H. Picha

Peaches stored in air for 40 days at OC developed severe internal breakdown and poor quality after transferring them to 20C to ripen. Comparable fruit stored under controlled atmosphere (1% O2 + 5% CO2) and then ripened at 20C had no breakdown and retained good quality. Fruit stored under CA had less reducing sugars but more sucrose than air stored fruit. Fruit pH increased and titratable acidity decreased over a 40 day storage period. Citric acid increased slightly while malic acid decreased during storage. Little or no differences in overall acidity and individual organic acids existed between CA and air storage. Little or no change in individual phenolic acid content occurred during storage or between CA and air storage. Internal color darkened and became redder with storage. CA stored fruit was significantly firmer than air stored fruit. Sensory evaluation indicated CA stored fruit was more acidic, sweeter, and had better overall flavor than air stored fruit.

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R.J. Bender, J.K. Brecht, D.J. Huber, and S.A. Sargent

Tree-ripe `Tommy Atkins' mangoes were not injured during storage in controlled atmospheres (CA) for 21 days at 8°C, and the fruit resumed ripening after transfer to air at 20°C (Bender et al., 1995). In our study, tree-ripe `Keitt' mangoes were stored at 5 and 8°C in either 10% or 25% CO2 combined with 5% O2 with control fruit maintained in air. Control fruit had higher percentages of electrolyte leakage than CO2-treated fruit at transfer from the CA and after 3 days in air at 20°C. Fruit stored in 25% CO2 at 5°C had significantly higher concentrations of 1-aminocyclopropane-1-carboxylic acid (ACC), over 0.5 nmol ACC/g fresh weight in mesocarp tissue. All the other treatments had similar ACC levels (<0.3 nmol/g fresh weight) after 21 days in CA. Ethylene production rates at both temperatures were significantly lower in the 10% CO2 treatment than in control fruit and were not detectable in 25% CO2. Ethylene production was similar in all treatments after transfer to air. Fruit from the 25% CO2 treatment at 5°C developed dull, green-grayish spots on the epidermis, but otherwise epidermal color, as determined by chroma and hue angles, did not differ among the treatments. There also were no differences in flesh color and flesh firmness.