Effect of Phytosanitary Irradiation on the Quality of Chandler Pummelo (Citrus maxima (Burm.) Merr.)

In this study, we evaluated the chemical and physiological effect of low-dose gamma irradiation on the post-harvest quality of Chandler Pummelos (Citrus maxima (Burm.) Merr.), an emerging crop of interest in the U.S. Chandler pummelos from a local grower in California were irradiated at target doses of 150 Gy and 1000 Gy. Irradiated and untreated pummelos were stored at 12 °C for 3 weeks and at 20 °C for the 4th week to reflect three weeks of sea shipment at ideal temperature for storage of pummelos and an additional week of retail under ambient conditions. Irradiation reduced hardness of the pummelo rind and firmness of the flesh. Rind hardness decreased during the 3 weeks of storage at 12 °C, however, during storage at 20 °C for 1 week, hardness increased, most likely due to moisture loss from the surface of the fruit. Although, a decrease in the firmness of the pummelo flesh was observed immediately following irradiation, storage did not lead to additional softening. The external appearance of pummelos was negatively impacted by higher irradiation dose, longer storage time and higher temperatures as pitting and mold growth were evident on pummelos treated at 1000 Gy and following storage at 20 °C. When stored at ideal temperature, pummelos irradiated at 150 Gy appeared to maintain similar quality as untreated pummelos. The results suggest that Chandler pummelo quality is compromised at 20 °C and 1000 Gy treatment but irradiation with 150 Gy can serve as a potential phytosanitary treatment for Chandler pummelos

Effect of Calcium Carbonate Residues from Cement Industries on the Phenolic Composition and Yield of Shiraz Grapes

Phenolic compounds are secondary metabolites synthesised in response to biotic or abiotic stress in plants.  This stress-induced increase in phenolic compound concentrations is generally activated by internal levels of abscisic acid (ABA). The exogenous application of ABA or calcium chloride on grapevines is also known to increase grape yield and alter the phenolic composition of grapes. Residues of cement industries such as calcium carbonates (CaCO3) are a safe environmental source of calcium that could be used to induce the synthesis of phenolic compounds and act as a yield promoter in grapes and other crops. Consequently, the objective of this study was to evaluate the effect of cement industries’ CaCO3 residues (CaCO3R) on the yield and concentration of phenolic compounds in Shiraz grapes. Thirteen phenolic compounds were identified and quantified by HPLC-DAD. Malvidin-3-O-glucoside was the major anthocyanin found inShiraz grapes, and its concentration increased by more than 200% in CaCO3R-treated vines. Similarly, the concentration of cinnamic acid, the main precursor of phenolic compounds, increased by more than 900%in grapes treated with CaCO3 residues at harvest time. Finally, catechin, epicatechin and procyanidin B1 and B2 increased significantly at harvest time in CaCO3R-treated grapes relative to the controls. In general, it was found that foliar application of CaCO3 residues from the cement industry at véraison induced an increase in yield, and in the concentration and composition of phenolic compounds in grapes