Individual Shrink Wrapping of Zucchini Fruit Improves Postharvest Chilling Tolerance Associated with a Reduction in Ethylene Production and Oxidative Stress Metabolites

We have studied the effect of individual shrink wrapping (ISW) on the postharvest performance of refrigerated fruit from two zucchini cultivars that differ in their sensitivity to cold storage: Sinatra (more sensitive) and Natura (more tolerant). The fruit was individually shrink wrapped before storing at 4°C for 0, 7 and 14 days. Quality parameters, ethylene and CO2 productions, ethylene gene expression, and oxidative stress metabolites were assessed in shrink wrapped and non-wrapped fruit after conditioning the fruit for 6 hours at 20°C. ISW decreased significantly the postharvest deterioration of chilled zucchini in both cultivars. Weight loss was reduced to less than 1%, pitting symptoms were completely absent in ISW fruit at 7 days, and were less than 25% those of control fruits at 14 days of cold storage, and firmness loss was significantly reduced in the cultivar Sinatra. These enhancements in quality of ISW fruit were associated with a significant reduction in cold-induced ethylene production, in the respiration rate, and in the level of oxidative stress metabolites such as hydrogen peroxide and malonyldialdehyde (MDA). A detailed expression analysis of ethylene biosynthesis, perception and signaling genes demonstrated a downregulation of CpACS1 and CpACO1 genes in response to ISW, two genes that are upregulated by cold storage. However, the expression patterns of six other ethylene biosynthesis genes (CpACS2 to CpACS7) and five ethylene signal transduction pathway genes (CpCTR1, CpETR1, CpERS1, CpEIN3.1 and CpEN3.2), suggest that they do not play a major role in response to cold storage and ISW packaging. In conclusion, ISW zucchini packaging resulted in improved tolerance to chilling concomitantly with a reduction in oxidative stress, respiration rate and ethylene production, as well as in the expression of ethylene biosynthesis genes, but not of those involved in ethylene perception and sensitivity.This work was supported by grants AGL2011-30568-C02/ALI from the Spanish Ministry of Science and Innovation, and AGR1423 from the Consejería de Economía, Innovación y Ciencia, Junta de Andalucía, Spain. Z.M. acknowledges FPU program scholarships from MEC, Spain. S.M. is funded by grant PTA2011-479-I from the Spanish Ministry of Science and Innovation

Modeling of ethylene biosynthesis during ripening and CA storage of 'Jonagold' apples

Simulation models can make the determination of optimal storage conditions for new cultivars of Malus domestica less expensive and less time consuming. On top of this, modeling creates the opportunity to apply batch dependent conditions. Two experiments were set up to develop a model to describe ethylene production during the ripening and storage of 'Jonagold' apples. Fruit were harvested at different dates around the optimal harvest date to obtain different ethylene production rates at different ripeness stages. Apples harvested at the three most extreme harvest dates were used for the storage experiment (CA conditions, 1% O-2, 3% CO2) and either treated or not treated with Smartfresh (TM), a commercially applied ethylene inhibitor. The ethylene production rate was determined by gas chromatography and S-adenosyl-L-methionine (SAM) concentrations were measured with capillary electrophoresis. During fruit ripening and during the storage of untreated fruit, an increase in ethylene production rate was noticed. SAM concentrations on the other hand were not influenced significantly during the 4 weeks period around optimal harvest time

Ethylene metabolism in 'Jonagold' apple during CA storage and shelf life : a modeling approach

To be able to preserve climacteric fruit like Malus domestica for a long time suppression and control of the ripening process is crucial. Based on measurements of metabolites and enzymes of ethylene biosynthesis and taking into account the underlying pathway, a kinetic model to predict and simulate ethylene metabolism during storage and shelf life of Jonagold apple was developed. Data was gathered during ripening, storage and shelf life experiments. The obtained model explains 80% of the data

ACC-Oxidase is the rate limiting step in ethylene biosynthesis during postharvest storage of tomato

It has been well documented in literature that ACC-synthase is the rate limiting step in ethylene biosynthesis during climacteric ripening of tomato. This manuscript investigates how the ethylene metabolism further evolves during post harvest storage of tomato. The current data show how ethylene production declines after tomato fruit reaches the red stage. Metabolite screening revealed that ACC and MACC are highly abundant in red ripe and stored fruits. Surprisingly, although ACC-oxidase in-vitro activity was declining, ACC-synthase in vitro activity was increasing again during postharvest storage. These data suggest that the decline in ethylene production during storage must be regulated at the level of ACC-oxidase. The exact reason why ACC-synthase is still highly active during these stages remains peculiar and needs further investigation