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Blue mold disease caused by Penicillium expansum is a major post-harvest disease of apples. In this research, the biochemical basis of apple resistance to this pathogen was studied in two relatively resistant and susceptible cultivars, Granny smith and Mashhad, respectively. The activities of catalase (CAT), peroxidase (POX), superoxide dismutase (SOD) and polyphenol oxidase (PPO) enzymes and polyphenol content were compared at different time intervals of 0 to 7 days. Based on the results, fruit polyphenol content of Granny smith was higher than that of Mashhad PPO, SOD and CAT activity was higher in Granny smith than Mashhad but CAT activity decreased three days post-treatment. No detectable difference was found in POX activities in the two cultivars. It is concluded that polyphenols contribute in apple resistance to blue mold. Activation of PPO and SOD, lack of POX activity and decrease of CAT activity, all together, could lead to a toxic environment around the blue mold fungus.

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The objective of this experiment was to investigate the antimould effect  of 19 Lactobacillus plantarum strains isolated from different production stages of  Lighvan cheese (3, 8 and 8 strains from raw milk, curd and fresh cheese stages, respectively) a traditional raw milk cheese, on  Penicillium expansum  (PTCC 89046) as an indicator  in fruit juice spoilage. This antimould spectrum was determined by agar spot and well diffusion method, followed by determination the influence of different technological or physico-chemical factors including  temperature (80°C for 1 h, 100°C for 10 min, 100°C for 30 min and 121° C for 15 min) and pH( 2 to 7) and different dilution (Titre test) . Serial twofold dilutions were conducted to the CFE in order to assess of CFE Titre against mould indicator. Findings revealed that Lactobacillus plantarum strain C28 has the highest antimould properties in both antimicrobial methods (Agar Spot and Well Diffussion Assay) and antimould effect showed decreasing trend with pH increasing. In 121 ° C for 15 min, no antimould effect was observed. The Lactobacillus plantarum strain C28  showed the highest titre  factor of 160 (AU / ml) .  Finally, we can assume that these strains which isolated from different production stages of Lighvan cheese or their Cell Free Extract (CFE) can be used as biopreservative in food systems.  

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Relative resistance of 43 Iranian as well as introduced apple cultivars to blue mold (Penicillium expansum) was studied within years 2010-2011. The fruit physicochemical traits were also evaluated as measures of potential resistance to decay. Local P. expansum strains were isolated from decayed apple fruits and the most aggressive isolate (5,000 spores ml^-1) used as inoculum. Fruits were wound-inoculated, and after four months stored in cold storage, decay lesion diameter was recorded. Force to break epidermis, cortex firmness, Total Soluble Solids (TSS) and Titratable Acidity (TA) were determined and their correlation with decay severity detected. Based on the obtained, results significant differences were observed in decay diameters in cultivars and for both years of the study priod. Mashhad was rated as the most susceptible cultivar while Granny Smith as the most resistant one. Relatively, 11.3% of cultivars were rated as susceptible, 54.5% as moderately susceptible, 31.8% as moderately resistant, and finally 2.2% resistant. The cultivars were significantly different in all the physicochemical traits studied. Correlation studies indicated weak negative correlations between decay diameter and TSS, TA, cortex firmness as well as epidermal toughness. Cortex firmness was directly correlated with epidermal toughness and is probable to influence blue mold severity.

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