Ripening Capacity Research Articles

(29) MCP Treatment Makes Delayed Application of Ethoxyquin Effective in Control of Superficial Scald of `d'Anjou' Pears

Superficial scald of `d'Anjou' pears usually develops after storage of 2 months or longer. MCP application controls scald; however, fruit lose their ripening capacity if the dosage is >30 ppb, but lower dosages cannot control scald substantially. In this study, fruit treated with or without 25 ppb MCP within 2 d after harvest were stored at –1 °C for up to 5 months. After 1, 7, 30, or 70 d of storage, part of the fruit were pulled from storage and treated with 1000 ppm ethoxyquin line spray and immediately returned to the storage, left untreated as non-ethoxyquin control. Incidence of superficial scald along with the concentrations of α-farnesene and conjugated trienes (CTs), and the ripening capacity of fruit were investigated after 3, 4, and 5 months storage. All fruit ripened properly within 7 d of conditioning at room temperature regardless of treatments. Both of MCP or ethoxyquin-1d (ethoxyquin was applied after 1 day storage at –1 °C) alone controlled scald for only 3 months; however, MCP + ethoxyquin controlled scald for 5 months, whenever ethoxyquin was applied between 1 to 70 d after storage. Thus, with 25 ppb MCP treatment, which is simple, with rapid and mass treatment available, a delayed application (up to 70 d) of ethoxyquin becomes effective to control scald. Furthermore, the later application of ethoxyquin within 70 d after MCP treatment, the less incidence of scald was observed. Scald is caused by the CTs oxidation products of α-farnesene. MCP and ethoxyquin inhibited accumulation of CTs of fruit peel by different mechanisms. MCP inhibited the production by influencing ethylene production through control of α-farnesene synthesis; however, ethoxyquin worked by inhibiting the oxidation of α-farnesene to the CTs.

(53) Do Pawpaw Varieties Behave Differently during Ripening and Cold Storage?

Pawpaw[Asiminatriloba (L.) Dunal] is a highly perishable climacteric fruit. Generally, fruit may be stored at 4 °C for 4 weeks with minimal loss in quality or subsequent ripening capacity. However, comparisons among cultivars and advanced selections for ripening behavior and postharvest storage life have not been reported. Ideally, cultivars with superior ripening traits (higher firmness, or a slower rate of firmness loss) and longer storage life may be identified for the commercial market. To determine if differences among genotypes may exist, respiration, C2H4 production, and fruit firmness of six varieties, 8-20, 9-58, `Middletown', `PA Golden', `Taytwo', and `Taylor', were measured during ripening after harvest and after 1, 2, 3, 4, 5, and 6 weeks of 4 °C storage. No differences were observed among the cultivars regarding respiration and C2H4 production. Respiratory and ethylene peaks were detected within 48 hours after harvest or removal from cold storage. Rapid loss of firmness was measured during ripening at ambient temperature after harvest and after removal from cold storage (days 0–3), with some loss during cold storage itself (weeks 1–6). As expected, firmer fruits at harvest had a lower respiration rate. However, no obvious differences in ripening behavior or cold storage response were observed among the six genotypes. As a general guideline, only firmer fruits should be cold stored, since fruit softening did not stop at 4 °C. A broader analysis of all of the named cultivars and advanced selections of pawpaw will be needed to determine if the present results are generally representative of pawpaw.

Inducing Optimal Ripening Capacity of 1-MCP-treated `Bartlett' Pears after Regular Air or Controlled Atmosphere Storage

`Bartlett' pears were treated with 300 nL·L-1 1-MCP at 20°C for 24 h shortly after harvest, and were stored at -1 °C in either regular atmosphere (RA) or controlled atmosphere (CA: 1.5 kPa O2 / 0.5 kPa CO2). After 2 and 4 months of RA storage, or 4 months of CA storage, fruit were pre-conditioned at 10 °C, 15 °C or 20 °C for 5, 10, or 20 days, respectively. Pre-conditioned fruit were then held at 20 °C for 14 days to simulate marketing conditions. Flesh firmness (FF) and extractable juice (EJ) were monitored during the marketing period. The optimal stage of ripeness for `Bartlett' pears was defined to be when FF decreases to 27 N and EJ decreases to 55 mL/100 g. The proper pre-conditioning combinations of temperature and duration were 15 °C or 20 °C for 10 d or 10 °C for 20 d if the fruit had been stored in RA for 2 months, 10 °C or 15 °C for 5 d if the fruit had been in RA for 4 months, and 20 °C for 10 d or 10°C for 20 d if the fruit had been in CA for 4 months, for which combinations the fruit ripened within a week and maintained quality for 14 days at 20 °C. The treatment combinations of lower temperature and/or shorter duration times in pre-conditioning delayed the ripening response of the fruit, and combinations of higher temperature and/or longer duration times in pre-conditioning resulted in a shorter marketing life because of senescence breakdown, in comparison the optimal combinations mentioned above. These results indicate that pre-conditioning regimes for 1-MCP treated `Bartlett' pears are storage atmosphere and time dependent. Generally, CA stored fruit needed more preconditioning (in terms of higher temperature and/or longer duration) than did RA stored fruit.

Relationship between fruit softening and cell wall polysaccharides in pears after different storage periods

Abstract We investigated the relationship between flesh firmness and the cell wall polysaccharides of ‘Marguerite Marillat’ and ‘La France’ pears that had retained or lost their ripening capacity. In both cultivars, fruit softened and reached a buttery and juicy texture after short-term storage (1 month at 1 °C), while fruit softened but never reached that texture after long-term storage (4 months for ‘Marguerite Marillat’ or 5 months for ‘La France’ at 1 °C). In ‘Marguerite Marillat’ pears, the water-soluble polyuronide (WSP) levels in fruit after long-term storage tended to be lower than those after short-term storage, when compared with fruit having similar flesh firmness. In ‘La France’ pears, lower flesh firmness correlated with higher WSP content in fruit after short-term storage, while the lower the flesh firmness, the lower the WSP content in fruit after long-term storage. The relationship between flesh firmness and alkali-soluble polyuronide (ASP) content showed the highest correlations in both cultivars among cell wall polysaccharides determined in this study. Lower flesh firmness correlated with lower ASP content, independent of cultivar and storage period. Fruit, after short-term storage, contained more ASP than after long-term storage in both cultivars, when compared with fruit having similar flesh firmness. The differences in the amount of hemicellulosic polysaccharides between hard and soft fruit were slight. There was no negative correlation between flesh firmness and cellulose content, independent of cultivar and storage period. These data suggest that lower polyuronide content, especially WSP and ASP, in fruit after prolonged storage is one cause of the inferior texture of pears after prolonged storage.

Differences in Biochemical Composition between ‘Beurre d’Anjou’ and ‘Bose’ Pears during Fruit Development and Storage1

Abstract A comparative study in 1979 and 1980 between ‘Anjou’, a long-keeping winter pear and ‘Bose’, a shorter keeping winter pear (both Pyrus communis L.) revealed that ethanol-insoluble matter, titratable acids, soluble solids, proteins, and free amino acids in fruit of both cultivars during fruit development, maturation, and storage period fluctuated from season to season and were not associated with their difference in postharvest life. Malic acid was the major fraction of organic acids in both cultivars, and it declined at a faster rate in ‘Bosc’ than in ‘Anjou’ during storage at −1.1°C. The amounts of citric, oxaloacetic, and fumaric acids were higher in ‘Bosc’ than in ‘Anjou’ and were maintained at constant levels throughout the storage period. Internal ethylene in both cultivars early in fruit development was about 0.3 ppm and decreased rapidly to below 0.07 ppm during late fruit development and harvest period. For 2 seasons, ‘Bosc’ was capable of ripening after less than 20 days of chilling at −1.1°C when its internal ethylene increased to 0.2 ppm, while ‘Anjou’ required at least 50 days of chilling to develop the ripening capacity coincident with an internal ethylene above 2.0 ppm. Internal ethylene accumulated in ‘Bosc’ about 8 times faster than in ‘Anjou’ during the first 60 days of storage at −1.1° and reached an equilibrium at 40 ppm for ‘Bosc’ and only 5 ppm for ‘Anjou’ during the remaining storage period. After any corresponding period of cold storage, both ethylene and CO2 productions of ‘Bosc’ at ripening temperature of 20° were higher than those of ‘Anjou’, and ‘Bosc’ also required fewer days to reach the climacteric peaks than did ‘Anjou’.