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  • Author or Editor: Diana L. Lange x
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Several leading Eastern muskmelon varieties were evaluated for their postharvest characteristics. The varieties evaluated were `All Star', `Athena', `Eclipse', `Legend', `Quasar', `Starship', and `Superstar'. The fruit were harvested in multiple harvests from 1 July through 10 Aug. 1996. Postharvest measurements taken included soluble solids (%), firmness, rind and flesh color, respiration, flavor quality, damage after drop tests, storage life, and shipping ability. The fruit of each cultivar were harvested at “half-slip” and “full-slip” and fully evaluated at each level of maturity. Most of the cultivars had similar postharvest characteristics, except `Superstar', which had the lowest overall ratings. Firmness ratings were highest for `All-Star', `Athena', and `Legend' and were lowest for `Superstar'. The flavor quality was similar for most cultivars and lowest for `Superstar' fruit. This trial will be repeated in 1996 and promising cultivars will be recommended for midwestern Unites States production.

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Modified atmosphere packaging (MAP) is a technology that is currently used for most packaged salads and fresh-cut vegetables, and to a lesser extent, fresh-cut fruit such as cantaloupe (Cucumis melo L.), pineapple [Ananas comosus L. (Merr.)], and apple (Malus ×domestica Borkh.). In addition, about 750 million lb (340,200 Mg) of strawberries (Fragaria ×ananassa Duch.), raspberries (Rubus idaeus L.) and sweet cherries (Prunus avium L.) are distributed in MAP annually. The fresh produce packaging industry has developed new films to respond to increased produce consumption and changes in the use of film packaging within different produce marketing segments. The produce film industry sold 60 million lb (27,200 Mg) of film in 1994, and in 2000 it is forecasted to sell 110 million lb (49,900 Mg), an increase of 83%. The distribution of film usage has also changed since 1994 when film consumption patterns were as follows: 20% [12 million lb (5,400 Mg)] retail, 15% [9 million lb (4,100 Mg)] warehouse clubstores, and 65% [39 million lb (17,700 Mg)] food service. In 2000 it is projected that consumption patterns will be as follows: 25% [27.5 million lb (12,500 Mg)] retail, 20% [22 million lb (10,000 Mg)] warehouse clubstores, and 55% [60.5 million lb (27,400 Mg)] food service. These changes represent a 10% shift in film market segment usage patterns away from food service applications to an increase of 5% for each of the retail and warehouse clubstore segments.

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Postharvest shelf life (defined by visual quality) of fresh, greenhouse-grown sweet basil (Ocimum basilicum L.) at 5 °C was only 3 to 4 d due to the appearance of chilling injury symptoms. Plants chill-hardened at 10 °C for 4 h daily (2 h at the end of the light period and 2 h at the beginning of the dark period) for 2 d, before harvesting and packaging, had ≈3 d longer postharvest life. Four- to 6-week-old plants were chill-hardened for 1 week at several periods during the day. Chill-hardening at the beginning of the day extended the average shelf life of cuttings from 4- to 5-week-old plants by 1 and 1.5 d, respectively. Shelf life either was decreased or not affected by the other periods of preharvest hardening. More importantly, postharvest chill-hardening of packaged sweet basil for 1 day at 10 °C in darkness before transfer to 5 °C increased average shelf life by 5 d. Good potential exists for postharvest chill-hardening of packaged sweet basil since this method is effective and convenient.

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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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Preclimacteric avocado [Persea americana (Mill.) cv. Hass] fruit or fruit disks as well as fruit harvested in either June (midseason) or August (late season) and partially ripened were kept in air (21% O2 + 78% N2), 20% CO2 + 17% O2 (63% N2), or 40% CO2 + 13% O2 (47% N2) at either 10 or 20 °C. Ethylene production by preclimacteric fruit was completely inhibited during CO2 exposure, whereas there was only partial inhibition of ethylene production when partially ripened fruit were exposed. Compared to the fruit stored in air, O2 uptake of fruit stored in 20% CO2 was decreased by 20%, whereas the fruit stored in 40% CO2 showed 25% more O2 uptake than air-stored fruit. Fruit subjected to a storage regime of 40% CO2 at 10 °C followed by 2 d in air had the best visual quality. In general, climacteric fruit treated with 20% CO2 at 10 °C showed increased pyruvate dehydrogenase (PDH) activity and decreased cytochrome oxidase (CytOx) activity. Fruit stored in 40% CO2 had reduced CytOx activity compared to air-stored fruit, and PDH activity was variable depending on the harvest season of the fruit. Our results show that the effect of elevated CO2 on a given enzyme depends on concentration of CO2, duration of exposure, physiological state of the fruit, and type of tissue exposed.

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Partially ripened avocado [Persea americana (Mill.) cv. Hass] fruit harvested in either June or Aug. 1994 were kept at 10 °C in air (21% O2), 20% CO2 (17% O2, balance N2), or 40% CO2 (13% O2, balance N2) for 7 to 12 days and then were transferred to air at 10 °C for 2 to 3 days. Mitochondrial respiration was stimulated in response to elevated CO2 treatments at 10 °C. A shift to alternative pathway (Alt) respiration occurred on day 4 in experiments using avocados from both harvest dates, with a return to initial levels in only the 20% CO2-treated fruit (June-harvested fruit after return to air). Elevated CO2 at 20 °C decreased the in vitro O2 consumption of isolated mitochondria compared to mitochondria kept in air. The Alt pathway contributed less to the total O2 uptake of CO2-treated mitochondria compared to mitochondria kept in air. The respiratory control ratios of the CO2-treated fruit and mitochondria were higher and lower, respectively, than the air controls. Induction of 33 to 37 kD proteins (corresponding to the size of the alternative oxidase proteins) occurred in avocados after 4 days in 40% CO2. These results indicate that elevated CO2 has various effects depending on concentration, duration and temperature of exposure, and mitochondrial function of avocado fruit, such as increased and altered respiratory oxidation and up-regulation of alternative oxidase proteins.

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Changes in cytosolic and vacuolar pH, ATP, ADP, and the ATP : ADP ratio were measured in whole fruit or mesocarp disks of avocado [Persea americana (Mill.) cv. Hass] during brief exposures to elevated CO2. Intact climacteric fruit exposed to air (21% O2), 20% CO2 (17% O2, balance N2), or 40% CO2 (13% O2, balance N2) had cytosolic pH values of 7.0, 6.6, and 6.4, respectively, while mesocarp disks had cytosolic pH values of 6.9, 6.7, and 6.4, respectively. The ß-ATP levels of intact climacteric fruit exposed to 20% CO2 or 40% CO2 for 2 h were reduced by 25% or 43%, respectively, relative to air-exposed fruit. HPLC analysis of nucleotide phosphates from preclimacteric avocados revealed that ATP levels and the ATP : ADP ratio increased in 40% compared to the air-stored fruit. However, 1 day after transfer to air, the effects of elevated CO2 had dissipated. These modifications in cellular state could alter the activity of respiratory enzymes in fruit exposed to elevated CO2 atmospheres.

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Highbush blueberry (Vaccinium corymbosum L. `Bluecrop') fruit sealed in low-density polyethylene packages were incubated at 0, 5, 10, 15, 20, or 25C until O2 and CO2 levels in the package reached a steady state. A range of steady-state O2 partial pressures (1 to 18 kPa) was created by placing a range of fruit weights within packages having a constant surface area and film thickness. The steady-state O2 partial pressure in packages containing the same weight of fruit decreased as temperature increased, indicating the respiratory rate rose more rapidly (i.e., had a greater sensitivity to temperature) than O2 transmission through the film. Steady-state O2 and CO2 partial pressures were used to calculate rates of O2 uptake. CO2 Production. and the respiratory quotient (RO). The effects of temperature and 02 partial pressure on O2 uptake and CO2 production and the RQ were characte∼zed. The steady-state O, partial pressure at which the fruit began to exhibit anaerobic CO2 production (the RQ breakpoint) increased with increasing temperature, which implies that blueberry fruit can be stored at lower O2 partial pressures when stored at lower temperatures.

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