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- Author or Editor: P. M. A. Toivonen x
- HortScience x
Broccoli (Brassica oleracea L., cv. Mariner) was harvested and the crop divided into four treatments; 1) “hydrocooled + no wrap”, 2) “hydrocooled + wrap”, 3) “not hydrocooled + no wrap”, and 4) “not hydrocooled + wrap.” Microperforated film (SM60, CryoVac) was used for the wrapped treatments. The broccoli was then placed in 1C storage. On day 3, samples of each of the four treatments were removed from storage and placed into a 13C room to simulate shelf conditions. Visual quality, weight loss, and respiration were monitored over 5 days at 13C. This shelf evaluation was repeated with broccoli samples that had been stored for 10 and 17 days at 1C. Hydrocooling had the greatest effect on shelf performance when broccoli was held in storage for only a few days. However, after a week or more of storage, wrap had the greatest effect on shelf performance. The shelf performance of the “hydrocooled + wrap” treatment was similar for all three shelf evaluations (i.e., after 3, 10, and 17 days of storage). The shelf performance of the other three treatments had significantly deteriorated by the 1st or 2nd week of storage. Broccoli in the “hydrocooled + wrap” treatment maintained the greatest firmness and the lowest respiration and water loss rates. Yellowing was not found to be a problem until a high degree of wilting had occurred. These results show that, with hydrocooling and wrapping, poststorage shelf performance of broccoli is stable for at least 2 weeks of storage at 1C.
When the gas concentrations of modified atmosphere packaging (MAP) become extreme for broccoli (<2 kPa O2 and >10 kPa CO2), off-odors and off-flavors may develop via anaerobic respiration, rendering it unmarketable. We recently showed that chlorophyll fluorescence decreases when broccoli switches to anaerobic behavior in MAP. The objectives of this study were to determine: 1) if chlorophyll fluorescence returns to normal levels after the package is opened and hence the broccoli is exposed to ambient air, and 2) if chlorophyll fluorescence is related to off-odors that develop. Broccoli heads were held in MAP (2 to 3 kPa O2 and >10 kPa CO2) at 0 to 1 °C for 4, 7, 14, 21, or 28 days, and then 5 days in ambient air at 0 to 1 °C. Chlorophyll fluorescence of the broccoli decreased dramatically in MAP, and remained low during the subsequent 5 days in ambient air. Similarly, off-odors became worse and acetaldehyde, ethanol, and ethyl acetate increased in the broccoli with time in MAP. However, these compounds slightly decreased during the subsequent 5 days of storage in ambient air. Chlorophyll fluorescence parameters correlated negatively with off-odor development and acetaldehyde, ethanol, and ethyl acetate levels in the tissue.
The effects of cooling method and packaging with perforated film on broccoli (Brassica oleracea L. Italica group) quality during 2C storage were studied. Broccoli was either room-cooled, top-iced, or hydrocooled before being placing into storage for 14 days. Hydrocooling was the most rapid cooling method and resulted in the lowest vapor pressure deficits between the broccoli and the surrounding air. Hydrocooling and top-icing resulted in similar firmness and color retention. Broccoli that was hydrocooled and then overwrapped with perforated film lost less weight, was firmest, and retained color better than either top-iced or room-cooled broccoli.
The replacement of postharvest moisture loss in carrots (cv. Caro-choice) by single and repeated recharging (i.e., rehydration in water) treatments, interaction between the duration of recharging and temperature during recharging, and the effects of these treatments on moisture loss during subsequent short-term storage were studied. Carrot weight gain increased with increase in the duration of single recharging treatments. Carrots that had lost 2.96% of their weight, during storage at 13°C and 35% relative humidity, regained as much as 2.45% of the weight during recharging for 12 h. Longer rechargings had little additional effect. Recharging at 13°C and 26°C was more effective at replacing water than at 0°C. The rate of moisture loss (%/day) during subsequent storage was not affected by recharging duration and the temperature. With repeated recharging (every 3.5 d), increase in recharging duration up to 9 h increased carrot weight gain. Most of the weight gain occurred following 0 to 7 d of storage. These treatments, however, did not affect the rate of moisture loss during subsequent storage. These results suggest that the beneficial effect of recharging on carrot quality is due to replacement of the lost moisture and not to a decrease in moisture loss during storage following recharging. It is suggested that recharging be explored as an option to improve the shelf life of carrots.
The effect of potassium (K) nutrition on the shelf life of carrots was studied using a hydroponics system involving rockwool slabs as support. Carrots were grown for 192 days under greenhouse conditions and supplied with 0, 0.1, 1.0, 10, and 15 mm of K. Increase in K concentration in the nutrient medium decreased postharvest weight loss. Carrot weight and tissue K content increased and water potential, osmotic potential, and relative solute leakage decreased with increasing K concentration in the nutrient feed. Differences in postharvest weight loss were mainly associated to root weight and relative solute leakage. Root weight correlated negatively and relative solute leakage correlated positively to water loss. Water and osmotic potential also correlated to water loss, but not as strongly as root weight and relative solute leakage. These results suggest that K nutrition influences postharvest weight loss by influencing carrot size and membrane integrity. Effects on cell water and osmotic potential are also important in this regard but to a lesser extent.
To understand the relationship between preharvest water stress and postharvest weight loss, carrot cultivars Eagle and Paramount were grown in muck soil in 6-L pots (eight carrots per pot) in a greenhouse at the Univ. of British Columbia. The plants were watered to field capacity every second day for 4 months before receiving 100, 75, 50, and 25% field capacity water stress treatments, henceforth referred to as low, medium, high, and severe water stress, respectively. Postharvest weight loss of carrots was monitored at 13°C and 32% relative humidity. Carrot weight loss increased with duration of storage in all treatments. It was low in the low-water-stressed and high in severely water-stressed carrots for both cultivars. Root crown diameter, weight, water, and osmotic potential decreased, and specific surface area and relative solute leakage increased with increasing preharvest water stress. Water potential followed by relative solute leakage were the variables that affected weight loss the most. The results show that carrots adjust to water stress by lowering water and osmotic potential. Preharvest water stress lowers membrane integrity of carrot roots making them lose more moisture during storage.