Changes in ripening behavior of ‘d'Anjou’ pears (Pyrus communis L.) after cold storage

‘d'Anjou’ pear fruit, harvested at optimum maturity with flesh firmness of 6.8 kg, were stored at ?1.1°C. Fruit were ripened at 20°C for 15 days following storage for 1–8 months. Dessert qualities were evaluated organoleptically on Day 10 of each ripening period. Changes in fruit firmness, extractable juice, titratable acids, solubl solids, respiration, ethylene production and internal ethylene were determined daily during each ripening period. Fruit firmness declined continually from 6.8 kg at harvest to 4.5 kg after 8 months of storage. Fruit stored for 2–8 months softened with a similar pattern during a 15-day ripening period at 20°C, while fruit stored for 1 month softened at a slower rate during ripening to 3.2 kg, with a coarse and dry texture after 15 days at 20°C. Fruit stored for 2–4 months ripened with the desirable buttery and juicy texture, while those stored for more than 5 months ripened with a coarse or mealy and dry texture. The buttery and juicy texture was highly correlated with a lower extractable juice, which could be used for quantitative determination of storage life based on ripened fruit quality. Changes in titratable acids and soluble solids during each ripening period were not associated with changes in dessert qualities of the ripened pears. Rates of respiration, ethylene production and internal ethylene during ripening at 20°C varied with duration of storage, but were not associated with changes in dessert qualities of the ripened fruit.     

Chilling induced ethylene biosynthesis in ‘Hayward’ kiwifruit following storage

‘Hayward’ kiwifruit were stored at 0, 5, 10, 15 and 20°C for 5, 12 and 17 days before rewarming to 20°C for 10 more days. Ethylene and CO₂ production, ACC, ACC synthase (ACS) and ACC oxidase (ACO) activities, flesh and core firmness, soluble solids content (SSC) and flesh colour were measured. Kiwifruit stored at 0, 5, 10 and 15°C did not ripen, produce ethylene or show increases in ACS or ACO activity. Fruit stored for 5 days at the above temperatures, then rewarmed to 20°C, did not show any change during the following 10 days. Rewarmed fruit, pre-stored at 0–10°C for 12 days, started autocatalytic ethylene production within 24 h, followed by fruit ripening. Fruit stored at 15°C for 12 days needed 72 h to start ethylene autocatalyse and did not fully ripen during 10 days at 20°C. After 17 days storage at 0–15°C kiwifruit started autocatalytic ethylene production with no delay upon exposure to 20°C. Autocatalytic ethylene production correlated with increased ACC content, and increased activities of ACS and ACO. Fruit held continuously at 20°C started autocatalytic ethylene production after 19 days, with concomitant increases in ACC content, ACS and ACO activities and ripening. Respiration increased after rewarming, concomitantly with the increase in ethylene production.We concluded that exposing kiwifruit to chilling temperatures (0–10°C) for 12 days advanced ethylene biosynthesis and ripening when compared with fruit held continuously at 20°C. The advanced ethylene biosynthesis was due to increase ACS and ACO activities immediately upon rewarming of the fruit.     

Can Mineral Analysis be Used as a Tool to Predict ‘Braeburn’ Browning Disorders (BBD) in Apple in Commercial Controlled Atmosphere (CA) Storage in Central Europe?

‘Braeburn’ apples stored in controlled atmosphere (CA) frequently present internal flesh browning physiological disorder which is commonly referred as ‘Braeburn’ Browning Disorder (BBD). Apples from different orchards, years or site conditions can vary considerably in their sensitivity. The aim of this research was to evaluate the relationship between the mineral status of ‘Braeburn’ apples before-harvest (18 days) and at early and normal harvest, to correlate the data with the BBD incidence found in apples post storage and to investigate possible reasons for differences in disorder sensitivity. Fruits from seven orchards in the Lake Constance area (South-Western Germany) were harvested at two picking dates and the mineral content was measured before-harvest, at-harvest and during storage. Fruit were stored at 1.5?°C under CA conditions (1 kPa O₂ and 0.5 kPa CO₂) using either a 10 days or a 24 days delayed establishment of CA conditions. Fruit were evaluated after 6 months of storage plus 10 days of shelf life at 18?°C for mineral status and the browning disorder incidence. Results indicate no significant changes of the mineral concentrations in the fruit during CA-storage. Significant correlations between the post storage BBD incidence with K, and in some cases also for the K/Ca ratio and for P at-harvest were found.     

Maintenance of fresh boysenberry fruit quality with UV-C light and heat treatments combined with low storage temperature

Summary

Mature boysenberries (Rubus hybrid) were harvested, heat-treated (45°C for 1 or 3 h or 47°C for 1 h) or exposed to UV-C light (2.3, 4.6 or 9.2 kJ m^–2), and stored at 20°C for 2 d. Fruit treated with 9.2 kJ m^–2 or 45°C for 1 h showed less damaged drupelets per fruit and/or remained firmer than untreated fruit after 2 d. Those treatments were selected for further analyses. In another experiment, boysenberries were either UV-C (9.2 kJ m^–2) or heat-treated (45°C for 1 h) and stored either at 20°C for 1 d or at 0°C for 4 d before transfer to 20°C for 1 d. Both UV-C and heat treatments reduced softening and/or fruit damage. Treated fruit had lower respiration rates and anthocyanin leakage than control fruit suggesting greater tissue integrity. Titratable acidity, pH, total sugar content and antioxidant activity in treated fruit showed fewer changes than in control fruit when stored at 20°C for 1 d. Results suggest that heat or UV-C treatment, alone or in combination with refrigerated storage, may be a useful non-chemical mean of maintaining boysenberry fruit quality and extending postharvest life.     

Interaction of Maximum Daily Trunk Shrinkage and Fruit Quality in European Plum

Maximum daily trunk shrinkage (MDS) has been suggested as an appropriate indicator of plant water status because it is closely related to stem water potential. Interaction of MDS and fruit quality was studied in plum (Prunus domestica L. ‘Jojo’/Wavit and ‘Tophit plus’/Wavit) in temperate climate. According to the MDS data, trees were grouped as low MDS (LMDS) and high MDS (HMDS). Fruit quality was analysed during fruit development (95, 103, 117 DAFB for ‘Jojo’ and 99, 112, 121 DAFB for ‘Tophit plus’) before commercial harvest. Fruit picked at commercial harvest (137 DAFB and 140 DAFB for ‘Jojo’ and ‘Tophit plus’, respectively) were stored at 2 ± 0.5?°C (90 ± 2% RH) for 28 days, and 2 days shelf life at 20?°C providing 6 measuring dates postharvest. Results confirmed that MDS was positively correlated with water vapour pressure deficit also in the apparent temperate, semi-humid climate. Transpiration of fruit from high crop load and resulting HMDS trees, which can be assessed as physiologically drought, was low compared to that of fruit from LMDS trees. Furthermore, HMDS tree grown plums had enhanced soluble solids and dry matter contents with a tendency of reduced fruit size.     

Effect of low-pressure storage on the quality of green capsicums (Capsicum annum L.)

Green capsicums (Capsicum annum L.) were stored under low pressure (4 kPa) at 10°C for 5 and 11 days with 100% RH. The results showed that the incidence of stem decay under low-pressure storage for 5 and 11 days and storage at ambient atmosphere at 20°C for 3 days was lower compared to fruits that were stored at regular atmosphere at 10°C. Fruit that had been stored at low pressure at 10°C had no symptoms of flesh rots for up to 11 days, whilst fruit which had been stored at regular atmosphere at 10°C had 6% flesh rots after 11 days storage at 10°C.There was no difference in flesh firmness and colour retention between fruits stored at low pressure and regular pressure at 10°C. Capsicums stored at low pressure had higher overall acceptability compared to fruit that were stored at regular atmosphere at 10°C. These results demonstrate the potential of low pressure storage as an effective technique to manage capsicum fruit quality, however, there was no additional benefit when fruits were stored at low pressure for more than 5 days.     

Tree yield and fruit minerals concentrations influence ‘Hass’ avocado fruit quality

To investigate the variation in quality of ‘Hass’ avocado fruit within an orchard, fruit were harvested at commercial maturity from 15 ‘Hass’ trees of similar appearance, growing in three adjacent rows on the same soil type, and receiving similar management. Fruit were harvested at commercial maturity, and either ripened at 22 °C or stored at 2 or 7 °C for 3 or 5 weeks and then ripened. Significant positive correlations (based on the mean for each datum tree) were noted between fruit flesh calcium (Ca) and magnesium (Mg) concentrations and the (Ca+Mg)/potassium ratio, and the number of days for the fruit to reach the eating ripe stage (DTR). Negative correlations were also observed between these minerals and anthracnose and mesocarp discolouration (MD) severity. Negative correlations were observed between fruit potassium (K) and phosphorus (P) concentrations and DTR. Fruit from trees with high fruit yield were generally smaller, with lower anthracnose and MD severity, ripened more slowly, and had higher flesh Ca concentrations. It is likely that cultural practices that maintain moderate to high fruit yield and reduce variation in yield will improve avocado fruit quality and reduce variability in quality. Since the main differences between adjacent trees in this trial were the seedling rootstocks of unknown origin, it is suggested that rootstocks can have a significant impact on avocado yield and fruit quality.     

The effects of storage temperature and fruit size on firmness,extractable juice,woolliness and browning in two nectarine cultivars

Fruit firmness, extractable juice, woolliness and browning of the mesocarp tissue in ‘Independence’ and ‘Flavortop’ nectarines stored at —0.5°, 3°, 5° and 7°C for four weeks were determined during ripening at 15°C. The firmness of both ‘Independence’ and ‘Flavortop’ during ripening decreased as storage temperatures increased. The percentage extractable juice after cold storage and during ripening varied considerably between cultivars and between the storage temperatures. The extractable juice of fruit stored at higher temperatures tended to increase during ripening, whereas fruit stored at lower temperatures tended to decrease first before increasing. At storage temperatures of —0.5° and 3°C both cultivars passed through a stage of woolliness during ripening, while less woolliness occurred after storage at 5° and 7°C. In both cultivars the percentage extractable juice during ripening was higher on average at storage temperatures of 5° and 7°C. Severe browning of mesocarp tissue in both cultivars occurred during ripening after storage at 3°C. The effect of fruit size on changes in firmness, development of woolliness and mesocarp browning in ‘Flavortop’ nectarines stored at — 0.5°C for four weeks and ripened at 15°C was also determined. Larger nectarines lost firmness more rapidly, woolliness occurred sooner and the mesocarp tissue was more prone to browning than smaller fruit during ripening.     

Quality of lemons sealed in high-density polyethylene film during long-term storage at different temperatures with intermittent warming

Storage of lemons is designed to extend the marketing of fruit throughout the year, from the main harvest season in the winter until late summer, which is a period of short supply in the market. This work was concerned with physiological and chemical attributes of stored lemons either seal-packaged in high-density polyethylene plastic film (HDPE), or left unwrapped, during storage at 13, 8 and 2°C. Intermittent warming (IW) was used to prevent chilling injury at the lower temperatures. Differences between fruit subjected to the two treatments which produced longest storage (sealed at 13°C and non-sealed at 2°C with IW) are discussed. Both treatments are recommended for adoption in commercial practice.     

Use of low-pressure storage to improve the quality of tomatoes

Freshly harvested vine-ripened tomatoes (Solanum lycopersicum cv. Neang Pich) were stored at low pressure (4 kPa) at 10°C for 11 days with 100% RH. Fruit quality was examined upon removal and after being transferred to normal atmosphere (101 kPa) at 20°C for 3 days. Weight loss was significantly lower in fruits which were stored at low pressure (4 kPa) than in fruits that were stored at regular atmosphere (101 kPa) at 10°C. Fruits that were stored at low pressure (4 kPa) reduced calyx browning by 12.5%, and calyx rots by 16%, compared to fruits that were stored at regular atmosphere (101 kPa) at 10°C. Fruit firmness was not significantly different between fruits stored at low pressures (4 kPa) and the normal atmosphere (101 kPa), with an average firmness of 14 N after fruits were stored at 10°C for 11 days. There was no difference in the SSC/TA ratio. The results suggest that a low pressure of 4 kPa at 10°C has potential as an alternative, non-chemical postharvest treatment to improve tomato quality during storage.     

Differential propylene induced ethylene production in ‘Anjou’ pears during storage at chilling and non-chilling temperatures

Summary

‘Anjou’ pears were harvested from the Mid-Columbia Experiment Station, Hood River, Oregon, at 67 N firmness, stored at –1° or 20°C for 85 d and periodically tested for sensitivity to 0 or 500 µl l^?1 propylene for at least 14 d at 20°C. Climacteric ethylene of pears stored at 20°C remained at low levels and started rising on the 90th day. Pears chilled at –1°C required 70 d to ripen and produced climacteric ethylene immediately upon transfer to 20°C. The sensitivity of the fruit to exogenous propylene increased progressively with storage time at –1°C. However, the non-chilled fruit responded to propylene similarly to freshly harvested fruit during the first 55 d of storage, then similarly to –1°C-stored fruit up to 85 d. Anjou pear ripening events and the sensitivity of the fruit to exogenous propylene developed differently in storage at non-chilling temperature compared with chilling temperature.     

Post-Harvest Studies on Autumn-Drilled Bulb Onions. The Effect of Harvest Date,Conditioning Treatments and Field Drying on Skin Quality and on Storage Performance

Overwintered onion cvs Express Yellow and Senshyu Semi-globe Yellow were harvested at 80% foliar fall-over (early June) and two and four weeks later, in 1975 and 1976. Plants were conditioned for one (1975) or two weeks (1976) at 20°C, 70% RH or 30°C,60% RH or field dried, and then stored at ambient temperature. Measurements of fresh weight loss during the first six weeks after harvest in 1976 indicated that drying was slow and was incomplete after 14 days conditioning at 30°C. Skin staining and splitting generally increased with delay in harvest date. Skin colour improved with delay in harvest date and with conditioning at 20°C. Wastage due to both rotting and sprouting during storage was generally lower when plants from the first two harvest dates were conditioned at 30°C. These bulbs are likely to be useful for long-term storage as total wastage levels of only 20% were reached in both cultivars after 3-5 months storage. Good field drying of the bulbs could not be consistently obtained and consequently storage performance was more variable than for bulbs conditioned at 20 °C and 30 °C before storage.     

Combinations of GA3 and AVG delay fruit maturation,increase fruit size and improve storage life of `Feicheng' peaches

Summary

Different concentrations of aminoethoxyvinylglycine (AVG) and gibberellic acid (GA₃) and their combinations, applied at two stages of fruit growth, were evaluated for prolonging the marketing season of `Feicheng' peaches. GA<sub>3</sub> applied at the end of pit hardening, or AVG applied two weeks before commercial harvest, inhibited fruit maturation on the tree, delayed harvest and reduced flesh browning after cold storage in a concentration-dependent manner. A synergistic effect was found when both GA<sub>3</sub> and AVG were used, with the combination of 100 or 150.mg l<sup>±1</sup> GA<sub>3</sub>, applied at the end of pit hardening, and 100 mg l<sup>±1</sup> AVG, applied two weeks before harvest giving the best results. These combinations retarded the change in ground colour, loss of firmness, and reduction in acidity by 2±3 weeks. Since harvest was prolonged by 2±3 weeks, soluble solids content (SSC) in fruit increased compared with the control (harvested earlier). Fruit size was significantly greater on treated trees compared with the controls when fruit set was controlled to the same level by hand thinning. After four weeks of storage and 4.d at 208C, 83% of control fruit developed tissue browning, but only 5% of AVG + GA<sub>3</sub>-treated fruit developed browning after six weeks of storage and 4 d at 208C. Thus, the marketing season of `Feicheng' peaches was prolonged by at least four weeks by 100 or 150 mg l^±1 of GA₃ and 100 mg l^±1 of AVG. Fruit treated with 150 mg l^±1 GA₃ plus 100 to 150 mg l^±1 AVG showed similar results but failed to ripen properly after cold storage.     

Subatmospheric pressure storage of mango fruits

Ripening of mango fruit is markedly delayed when the pressure in the storage chamber is reduced below 100 mm Hg, and fruit storage life is thus prolonged. The prolongation of storage life is inversely related to the pressure; control fruit stored at 760 mm Hg started to ripen after 16 days in storage at 13°C, while fruit stored at 100 and 75 mm Hg after 25 and 35 days, respectively. Fruit stored at 50 mm Hg remained unripe for 35 days. No effect on ripening was recorded at pressures above 250 mm Hg, while at pressures below 50 mm Hg the fruit desiccated. All fruits stored at subatmospheric pressure ripened 3–4 days after transfer to shelf life at 25°C. However, green mango fruits of the colored cultivars like ‘Haden’ and ‘Maya’, stored at subatmospheric pressure for a prolonged period, did not develop the proper red or orange color during shelf-life, but turned pale yellow instead. Treatment with ethylene upon removal from storage slightly improved color development in these fruits.     

Preventing cold storage disorders in nectarines

A storage experiment was aimed at preventing low temperature storage disorders in nectarine fruits, of cvs July Red and Autumn Grand. Fruit was either cooled immediately after harvest or kept at 20°C for 48 h, before transfer to controlled atmosphere (CA) conditions at 0°C. Combinations of 0, 10, 15 and 20% C02 with 8 and 16% 02 were assayed. The fruit was evaluated following cold storage, 31 days after harvest, and after four and eight days under ‘shelf conditions’ (ripening at 15-18 °C). Warming of the fruit at 20°C before cold storage prevented woolliness in the absence of elevated C02 levels but did not affect internal browning and increased reddish discoloration; further, it enhanced water loss and ripening, increasing fruit softening markedly. Conversely, high C02 delayed fruit ripening in CA storage, keeping the fruit firmer, and preventing the development of woolliness, internal browning and reddish discoloration during ripening, the best results being mostly obtained with 20% C02. 02 levels assayed did not show clear effects, but decreased 02 concentration in absence of high C02 showed some benefit in ‘July Red’. No deleterious effect of C02 concentrations even as high as 20% could be detected. Thus, even though high C02 in CA conditions showed promise for controlling disorders and preventing over-ripening, further work is needed on other cultivars, and lower 02 concentrations should be investigated before making a general recommendation.     

Polygalacturonase and β-galactosidase activities in Hayward kiwifruit as affected by light exposure,maturity stage and storage time

Softening process and total antioxidant activity were evaluated in kiwifruit differently exposed to light intensity and harvested at two different times (October 10 and November 14). Fruit was stored for 2 months at 0 °C (S1) and then maintained for a week at ambient temperature (S2). The results showed that fruit harvested later presented a faster softening rate during storage than fruit harvested earlier, even if antioxidant activity did not change. Light-exposed fruit showed higher flesh firmness than that of shaded ones. Polygalacturonase activity was higher in kiwifruit maintained for a week at ambient temperature after cool storage and, in particular the highest value was recorded in fruit harvested later. The behaviour of β-galactosidase was different: it did not show changes in fruit harvested later and significantly decreased in light- and shade-exposed fruit harvested earlier.     

Physiological and anatomical changes associated with ripening in the inner and outer mesocarp of cold stored ‘Songold’ plums and concomitant development of internal disorders

Plums (Prunus salicina cv. Songold) were cold stored for 10 d at -0.5°C followed by 18 d at 7.2°C and 7 d at 10°C. On the day of harvest and after 15,30 and 35 d of storage, the physiology, anatomy and development of internal disorders in inner and outer mesocarp tissue were assessed. Soluble solids, juice pH, internal conductivity, viscosity of soluble pectin and membrane leakage were significantly higher in the inner tissue, while titratable malic acid levels were lower, indicating that fruit was riper on the inside than the outside. Changes as indicated by the same variates showed that the rate of ripening in inner tissue was more rapid than in the outer mesocarp tissue over storage time. Gel breakdown in inner tissue was associated with high viscosities of water soluble pectin, permeable membranes, and as a result, binding of cell fluids which led to low levels of extractable juice. In outer tissue where extractable juice levels were higher, overripeness developed. At the ultrastructural level, it was evident that cell walls of inner tissue were thicker and had a better developed middle lamella than outer tissue. Inner mesocarp tissue was composed of larger cells than outer tissue.     

Fruit thinning in ‘Conference’ pear grown under deficit irrigation: Implications for fruit quality at harvest and after cold storage

Fruit thinning in pear is feasible for mitigation of water stress effects. However, it is not well known how fruit quality at harvest and after cold storage is affected by pre-harvest water stress. Even less is known about the effects of fruit thinning on quality under these circumstances. To elucidate these, we applied deficit irrigation (DI) and fruit thinning treatments to ‘Conference’ pear over the growing seasons of 2008 and 2009. At the onset of Stage II (80 and 67 days before harvest in 2008 and 2009, respectively), two irrigation treatments were applied: full irrigation (FI) and DI. FI trees received 100% of crop evapotranspiration (ETc). DI trees received no irrigation during the first three weeks of Stage II to induce water stress, but then received 20% of ETc to ensure tree survival. From bud-break until the onset of Stage II and during post-harvest, FI and DI trees received 100% of ETc. Each irrigation treatment received two thinning levels: no thinning leaving commercial crop load (∼180 fruits tree⁻¹), and hand-thinning at the onset of Stage II leaving a light crop load (∼85 fruits tree⁻¹). Under commercial crop loads, DI trees were moderately water-stressed and this had some positive effects on fruit quality. DI increased fruit firmness (FF), soluble solids concentrations (SSC) and acidity at harvest while no changes were observed in fruit maturity (based on ethylene production). Differences in FF and acidity at harvest between FI and DI fruit were maintained during cold storage. DI also reduced fruit weight loss during storage. But fruit size was reduced under DI. Fruit thinning under DI resulted in better fruit composition with no detrimental effect on fresh-market yield compared to un-thinned fruit. Fruit size at harvest and SSC values after five months of cold storage were higher in fruit from thinned trees than fruit from un-thinned trees. Fruit thinning increased fruit ethylene production, indicating advanced maturity. This may lead to earlier harvest which is desirable in years with impending drought. Fruit thinning is therefore a useful technique to enhance pear marketability under water shortage.     

Effects of high-humidity storage on quality,decay and storage life of cherry,lemon and peach fruits

Sweet cherries (Prunus avium (L.) ‘Lambert’ and ‘Blackboy’), lemons (Citrus limon (L.) Burm. f. ‘Lisbon’) and peaches (Prunus persica (L.) Batsch, ‘Summerset’) were stored at 77–83, 90–94 and 95–99% RH (high humidity) at near-optimal storage temperatures after harvest and treatment with fungicides. High-humidity storage did not increase the storage life of peaches held at 0°C, but the life expectancy of cherries (both cultivars) was extended by 7–10 days at 0°C, and of lemons by at least 4 weeks at 10°C when fruit were stored at 95–99% RH compared with levels below 95%. The beneficial effects of high humidity were attributed to retardation of peel desiccation and associated reductions in fruit deformation, peel de-greening, chilling-injury and decay in lemons and to the maintenance of a fresher stalk and a firmer, less shrivelled fruit in cherries. High humidity had no effect on decay in cherries or peaches, but it significantly reduced weight loss and delayed the appearance of shrivel in peaches stored at 0°C. However, after storage at high humidity for 4 weeks, peaches ripened with low rates of C₂H₄ evolution and showed severe low-temperature injury, slight peeling-injury and a poor flavour ex-store.     

The effect of fruit maturity on quality and colour shift of dried ‘Patterson’ apricot during eight months of cold storage

Summary

Fresh ‘Patterson’ apricot was harvested at three fruit maturity levels and characterized with measurements of flesh colour, Brix, acidity and levels of specific sugars. Fruit from the three maturity classes were sun-dried under uniform conditions. Dry fruit was again analysed for the content of specific sugars before cold storage. Stored fruit were sampled periodically for colour coordinates L*, C* and H° during an eight-month period. The study was repeated for two harvest seasons. In each season, significant differences (P≤0.05) were observed between the three fruit maturity classes for Brix, acidity, C* and H8. Levels of specific sugars varied significantly (P≤0.01) with regard to fruit maturity class, tissue type and fruit status. Regression analysis of colour coordinate changes during the storage period indicated significant (P≤0.05) differences in rate of colour shift of L*, C* and H8 relative to fruit maturity class. While dried fruit of the immature class was of substandard quality after the storage period, both medium and most mature dry fruit were of sufficient quality to warrant marketing even after eight months of cold storage.