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- Author or Editor: P.M.A. Toivonen 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.
The response of four apple (Malus ×domestica) cultivars (Gala, Granny Smith, Ambrosia, and Aurora Golden Gala™) to fresh-cut processing at core temperatures of 1, 5, 13, and 20 °C was investigated. Fruit were cut after a 24-h preconditioning at one of the four temperatures and a commercial antibrowning formulation was applied as a 7% (w/v) dip before packaging the slices and storing them for 3 weeks at 5 °C. Fruit firmness generally decreased with increasing core temperature, except for Aurora Golden Gala™, which maintained similar firmness at all temperatures. Firmness varied among cultivars, but all except Granny Smith apples held at 13 and 20 °C, were at or above a minimum processing firmness standard of 14 lbf. Cut-edge browning of slices, in response to processing temperature, varied among the cultivars. In the extreme, ‘Granny Smith’ was the most responsive, showing the largest variance in surface lightness across the temperature range. ‘Ambrosia’ was the least responsive to temperature, showing no significant difference in L-value despite the temperature at which it was processed. ‘Gala’ and Aurora Golden Gala™ were intermediate in response. The visual quality rating for ‘Granny Smith’ at 3 weeks was poor for slices from all processing temperatures. ‘Ambrosia’ slices maintained acceptable quality ratings over the full test temperature range. ‘Gala’ slices had lower quality ratings when processed at warmer temperatures, whereas Aurora Golden Gala™ showed increased quality ratings with warmer processing temperatures. It was concluded that ‘Gala’ were best processed at low core temperatures, ‘Ambrosia’ could be processed at all tested temperatures, and Aurora Golden Gala™ produced better quality slices when fruit were are room temperature (20 °C) before slicing.
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.
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 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.
Studies were carried out to understand the effects of moisture loss on water potential and root deterioration in carrot (Daucus carota L. `Eagle') roots during short-term storage. The roots were stored at various temperatures and relative humidities (RH) to provide 0.7 (low), 3 (medium), and 9 mbars (high) of water vapor pressure deficit (WVPD). Carrots at high WVPD lost the most weight, followed by those at medium and lowest WVPD. Water potential and osmotic potential of the carrot tissue at high WVPD did not change significantly up to 6 days, but decreased thereafter. There was no change in water potential and osmotic potential for carrots at medium and low WVPD. A significant quadratic relationship (P = 0.05, r = –0.764) between water potential and carrot root weight loss was observed. Relative electrolyte leakage increased over time in carrots at the high WVPD. At medium WVPD, relative electrolyte leakage did not change up to 6 days, but increased significantly thereafter. Carrots at the low WVPD did not change in relative electrolyte leakage. Relative electrolyte leakage and weight loss correlated positively (P = 0.05, r = 0.789). The results suggest that water stress during short-term storage causes tissue deterioration that may further increase rate of moisture loss and hence reduce 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.
In the 1979-1980 and 1980-1981 seasons, stored cabbage (Brassica oleracea L., Capitata group) developed symptoms of the disorder black speck. Dipping in 500 mg/liter benomyl and 95 or 190 mg/liter chlorine (as sodium hypochlorite) solutions increased susceptibility to the development of black speck, but control of ethylene levels and an atmosphere of 3% O2 + 5% CO2 had little effect. A slight difference was noted in cultivar susceptibility and in one season a dip in water appeared to decrease the occurrence of the disorder.