William V. Biasi

Detection and monitoring of internal browning development in ‘Fuji’ apples using MRI

Abstract Magnetic resonance imaging (MRI) experiments were used to detect and monitor the progression of internal browning (IB) in Fuji apples ( Malus domestica Borkh. ). The apples were stored in two different controlled atmosphere (CA) conditions: 3% CO 2 at 0°C and 18% CO 2 at 20°C. The apples stored under 18% CO 2 , were imaged at 1, 3, 5, 7 and 9 days. Apples stored under 3% CO 2 were imaged once a week for the first 7 weeks and then every 2 weeks until the 12th week. Three distinct regions were identified in the MR images of apples with internal browning: normal, light brown and dark brown tissue. Light brown regions, more prominent in apples stored in 3% CO 2 at 0°C, had a lower signal intensity than normal tissue because of lower proton density (PD) and smaller transverse relaxation times ( T 2 ). Dark brown regions predominated in apples stored in 18% CO 2 at 20°C and displayed higher signal intensity than the normal apple tissue because of larger T 2 values. The speed of image acquisition was improved from 5.5 min to 20 s, by reducing the spatial resolution of the images. Both types of IB were detected by images acquired using coarse spatial resolution and correlated well to the IB detected by the images acquired using fine spatial resolution.

Effects of ethylene and 1-MCP on the quality and storage life of strawberries

Strawberry quality declines rapidly after harvest. Deterioration may be accelerated by ethylene and is potentially increased, decreased or unaffected by the ethylene inhibitor 1-MCP (1-methylcyclopropene). We have examined the effects of 0.01, 0.05, 0.1 and 1 m ll 1 of ethylene and 0.01, 0.1, and 1.0 m ll 1 1-MCP on the quality attributes and respiration rates of strawberries stored at 0 or 5 8C. Ethylene did not affect the rate of rot development. However, calyx quality was significantly reduced by exposure to 0.1 or 1.0 m ll 1 ethylene. Treatment with 1 m ll 1 1-MCP protected the calyx tissue from these effects. Exposure of strawberries to 0.01, 0.1 or 1.0 m ll 1 1-MCP did not affect overall fruit acceptability but did slightly increase the rate of rot development. 1-MCP treatment reduced ethylene production by the fruit. Increased production of CO2 by 1-MCP treated fruit was associated with the earlier onset of rots. Although the results suggest that blocking ethylene perception interferes with disease resistance in strawberries, there was only a small effect on total storage life. It was concluded that neither the removal of low levels of ethylene from the storage environment nor the treatment with 1-MCP are likely to be cost effective methods of extending strawberry storage life. It was concluded that neither removing low levels of ethylene from the storage environment nor treating with 1-MCP are likely to be cost-effective methods of extending storage life. # 2002 Elsevier Science B.V. All rights reserved.

Exogenous ethylene accelerates ripening responses in Bartlett pears regardless of maturity or growing region

Abstract Mature-green ‘Bartlett’ pears ( Pyrus communis L.) were harvested weekly during the commercial harvest period to explore the influence of three climatically diverse growing locations and of harvest maturity on the requirement for C 2 H 4 treatment at harvest to achieve uniform ripening and good eating quality. Pears were treated with ethylene (air+10 Pa C 2 H 4 ) or air (untreated) at 20°C for 24 h to determine their responsiveness to C 2 H 4 , including the effect on 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACC-S) and ACC oxidase (ACC-O) activity during subsequent ripening at 20°C. Exposing freshly harvested and non-chilled ‘Bartlett’ pears to 24 h exogenous C 2 H 4 treatment concurrently stimulated the activity of ACC-S and ACC-O, and resulted in higher C 2 H 4 production, which advanced the rate of ripening and reduced the firmness variability regardless of maturity, growing region or season. Differences in the rate of softening between ethylene-treated and untreated pears were greatest for fruit from earlier harvest dates. The ripening capacity of ‘Bartlett’ pears developed as the fruit matured on the tree, resulting in higher ACC-S activity, ACC-O activity and C 2 H 4 production, but the ripening capacity was not fully induced unless the fruit were cold stored or treated with exogenous C 2 H 4 . Ethylene production was higher in fruit from growing locations that experience cooler preharvest temperatures and fruit from later harvests within each location. Pears harvested from warmer growing regions as well as early harvests from later growing locations which experience cooler preharvest night temperatures can benefit from treatment with C 2 H 4 after harvest to promote uniform ripening.

Prediction of controlled atmosphere-induced flesh browning in `Fuji' apple

Abstract Rapid induction of internal flesh browning by exposure of fruit to high CO2, fruit maturity indices, respiration rates and CO2 permeances were assessed as predictors of flesh browning which developed in apple (Malus domestica, Borkh. cv. Fuji) during long-term controlled atmosphere storage. Fruit were harvested from eight orchards at 170, 190 or 210 days after full bloom and held at 20°C in 50 kPa CO2 (balance air) for 1–3 days, in 20 kPa CO2 (balance air) for 3–7 days or at 0°C in a controlled atmosphere of 2 kPa O2+2 kPa CO2 for 150 days. Flesh browning increased with greater exposure time in 20 kPa and 50 kPa CO2 and after 3 days of exposure, more browning developed in fruit exposed to 50 than 20 kPa CO2. Flesh browning in all atmospheres increased with harvest date but significant variability was present among orchards at any one harvest. Across all orchards and harvest dates, strong positive relationships were found between flesh browning after controlled atmosphere storage and that which developed after short-term exposure to 20 kPa CO2 at harvest. This relationship improved with decreasing exposure time at 20 kPa CO2. While substantial differences in fruit maturity indices (background colour, starch pattern index, watercore incidence, soluble solids concentration, titratable acidity, flesh firmness), fruit respiration rates and fruit permeances to CO2 determined at harvest were also found among harvest dates and orchards, they were at best poorly related to flesh browning. The best predictor of orchard and harvest date differences in controlled atmosphere-induced flesh browning was therefore assessment of flesh browning after exposure of fruit to 20 kPa CO2 for 3 days.

Effect of ethylene in the storage environment on quality of ‘Bartlett pears’

The effect of ethylene on the quality of ‘Bartlett pears’ stored at either � / 1o r 28C was examined. Fruit from three different harvest dates were stored for 3 months in 0, 1, 5 or 10 m ll � 1 ethylene. Quality attributes, including skin color, firmness, scald and internal browning, were assessed when the fruit were removed from storage and after 4 days ripening at 20 8C. All levels of ethylene increased the incidence of physiological disorders. However, the effect of ethylene was minor compared with the influence of temperature. Fruit stored at � /1 8C remained firm and green, subsequently ripening normally at 20 8C, irrespective of exposure to ethylene. In contrast, all of the pears kept at 2 8C softened and yellowed during storage, and developed symptoms of superficial scald and internal browning. The severity of these disorders increased when fruit were ripened at 20 8C. It was concluded that although it is desirable to minimize ethylene in the storage atmosphere, benefits are likely to be minor compared with the potential gains from good temperature management. # 2002 Elsevier Science B.V. All rights reserved.

Tolerance of ‘Fuyu’ persimmons to low oxygen and high carbon dioxide atmospheres for insect disinfestation

Abstract The tolerance of ‘Fuyu’ persimmons ( Diospyros kaki L.) to insecticidal controlled atmosphere (ICA) was investigated. Freshly harvested ‘Fuyu’ persimmon fruit were exposed to air, 0.25% O 2 , 40% CO 2 in air, and 0.25% O 2 + 40% CO 2 at 20 °C for 3, 5 and 7 days. Fruit treated with ICA exhibited slight external injury and fruit treated with 40% CO 2 , regardless of the O 2 concentration, were softer than fruit treated with air or 0.25% O 2 only 5 days after removal from the treatment. Ethanol and acetaldehyde concentrations were higher in treated fruit compared with air controls upon removal from ICA, with the highest levels in persimmons exposed to 0.25% O 2 + 40% CO 2 . Treatment with 40% CO 2 (balance air) resulted in higher levels of ethanol and acetaldehyde in the fruit than treatment with 0.25% O 2 (0.03% CO 2 ). Ethanol and acetaldehyde concentrations decreased 30 and 20%, respectively, after 5 days storage in air at 10 °C following ICA. Informal sensory evaluations indicated no loss in quality as a result of the ICA treatments. Tolerance of ‘Fuyu’ persimmons to ICA indicates a potential for developing such treatments for insect quarantine.

EFFECT OF TEMPERATURE MANAGEMENT METHODS ON FIRMNESS UNIFORMITY OF COMMERCIALLY RIPENED CANNERY PEARS

The effect of natural convection or forced–air temperature transition during commercial storage and ripening of ‘Bartlett’ pears (Pyrus communis L.) in field bins on fruit firmness uniformity following ripening was investigated. Time required for natural convection or forced–air cooling of fruit to 0 _ C and re–warm to 20_C was profiled in standard wooden bins and in higher ventilated plastic bins. Firmness of fruit sampled throughout the bins was analyzed with respect to their position in the bins during storage and ripening. Pears experiencing natural convective cooling or warming in standard wooden field bins obtained seven–eighths temperature transition across the whole bin within 18 and 34 h of each other, respectively. In plastic field bins, seven–eighths temperature transition occurred within 11 and 10 h of each other, respectively. Under a forced–air velocity of 0.41 m s –1 , pears in wooden or plastic field bins obtained seven–eighths temperature transition across the entire bin within 3.6 and 4.4 h of each other, respectively, for both cooling and warming. Firmness uniformity of sized, commercially ripened pears was not improved by forced–air cooling as opposed to natural convective cooling during the initiation of cold storage; however, forced–air as opposed to natural convective cooling of unsized pears improved firmness uniformity, possibly due to more consistent cooling times between adjacent large and small fruits. The variability in firmness of the ripened, sized, and unsized pears in the bins increased due to firmer fruit in the bottom of both wooden and plastic bins, irrespective of their exposure to forced–air or natural convective cooling during cold storage initiation or warming at the initiation of fruit ripening. This increased firmness variability was largely attributed to fruit temperature transitions resulting from unstable air temperatures during commercial ripening. Results indicate the benefit of improved firmness uniformity in fruit sorted for size prior to cold storage, and ripened under stable ripening room temperatures.