No abstract

A new chlorophyll fluorescence (F) sensor system called FIRM (fluorescence interactive response monitor) was developed that measures F at low irradiance. This system can produce a theoretical estimate of Fo at zero irradiance for which we have coined a new fluorescence term, Fα. The ability of Fα to detect fruit and vegetable low-O2 stress was tested in short-term (4-day) studies on chlorophyll-containing fruit [apple (Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.), pear (Pyrus communis L.), banana (Musa ×paradisiaca L.), kiwifruit (Actinidia deliciosa C.S. Liang & A.R. Ferguson), mango (Mangifera indica L.), and avocado (Persea americana Mill.)] and vegetables (cabbage (Brassica oleracea L. Capitata Group), green pepper (Capsicum annuum L. Grossum Group), iceberg and romaine lettuce (Lactuca sativa L.)). In all of these fruit and vegetables, Fα was able to indicate the presence of low-O2 stress. As the O2 concentration dropped below threshold values of 0 to 1.4 kPa, depending on the product, the Fα value immediately and dramatically increased. At the end of the short-term study, O2 was increased above the threshold level, whereupon Fα returned to approximately prestressed values. A 9-month study was undertaken with `Summerland McIntosh' apple fruit to determine if storing the fruit at 0.9 kPa O2, the estimated low O2 threshold value determined from Fα, would benefit or damage fruit quality, compared with threshold + 0.3 kPa (1.2 kPa O2) and the lowest recommended CA (1.5 kPa O2). After 9 months, the threshold treatment (0.9 kPa) had the highest firmness, lowest concentration of fermentation volatiles (ethanol, acetaldehyde, ethyl acetate) and lowest total disorders. Sensory rating for off-flavor, flavor and preference indicated no discernible differences among the three treatments.

ADDITIONAL INDEX WORDS. Malus ×domestica Borkh., chlorophyll fl uorescence, controlled atmosphere storage, dynamic low-oxygen controlled atmosphere storage, fl uorescence interactive response monitor, fruit quality, HarvestWatch, postharvest SUMMARY. HarvestWatch is a new chlorophyll fl uorescence (F)-based technology that identifi es the lowoxygen threshold for apple (Malus ×domestica) fruit in dynamic low-O 2 controlled atmosphere (DLOCA) storage environments [e.g., <1% oxygen (O 2 )]. Immediately following harvest, 'Cortland', 'Delicious', 'Golden Delicious', 'Honeycrisp', 'Jonagold' and 'McIntosh' fruit were cooled and loaded into 0.34 m 3 (12.0 ft 3 ) storage cabinets. A static controlled atmosphere (CA) regime of 1.5% O 2 , 1.5% carbon dioxide (CO 2 ) and 3 o C (37.4 o F) [0 o C (32.0 o F) for 'Delicious' and 'Golden Delicious'] was established for the control fruit, while the low-O 2 threshold was identifi ed by a spike in the fl uorescence parameter, Fα, as the O 2 levels in the DLOCA cabinets were lowered below 1%. The DLOCA storages were then maintained at O 2 levels of 0.1% to 0.2% above the threshold value for each cultivar, which returned Fα to prethreshold signatures. Quality

Forced-air cooling rates of highbush blueberries (Vaccinium corymbosum L.) packaged in 6-oz (177-mL) or 1-pt (473-mL) clamshell containers were affected by positions of vent holes in corrugated flats. Most rapid cooling occurred in flats with vents across the top of the flat. Additional vents aligned in front of clamshells resulted in more rapid and uniform cooling than vents placed between clamshells. Vent holes in the bottom of flats had no effect on cooling rates. Clamshells cooled more slowly in the front of the pallet where cold air entered than in the back of the pallet where cold air exited. Fruit in 6-oz clamshells cooled faster than fruit in 1-pt clamshells.

A plastic tent was designed and constructed for the controlled atmosphere (CA) storage of small quantities of fresh produce. The CA tent is suspended from pallet racking in a standard cold room and can hold two standard pallets stacked 6 feet high with produce. Tents are sealed with two air tight zippers and a small water trough, resulting in an airtight chamber that successfully maintains CA storage environments. The CA tents are easily set up and removed to allow flexibility in use of storage space. To provide efficient use of storage space tents can be stacked two or three high on pallet racking. Tents are easily loaded and unloaded by a single person using a forklift. CA tents provide an economical alternative to traditional CA rooms for the storage of small quantities of fresh produce under CA environments.