Changes in pectin methylesterase, polygalacturonase, catalase and peroxidase activities associated with alleviation of chilling injury in persimmon by hot water and 1-MCP treatments
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'Rojo Brillante' persimmon is an astringent cultivar whose fruits are chilling injury-sensitive. A pretreatment of 1-MCP or Hot Water before cold storage is known to alleviate flesh softening, the main chilling injury symptom to occur when fruit is transferred from low to moderate temperatures. In order to better understand the chilling injury alleviation mechanism in persimmon through these two treatments, the changes of antioxidant system enzymes (catalase and peroxidase) and cell wall degrading enzymes (pectin methylesterase and polygalacturonase) were evaluated. Persimmon fruits subjected to the 1-MCP treatment (500 nL L-1) or to hot water treatments (45 degrees C for 30 min) (HWT-45 degrees C) and 50 degrees C for 20 min (HWT-50 degrees C) were stored at 1 degrees C for 30 days. Then they were submitted to a deastringency treatment (98% CO2 at 20 degrees C for 24h) before being transferred to shelf-life conditions for 5 days at 20 degrees C. The HWT applied at 50 degrees C and 1-MCP were observed to be the most effective treatments to reduce firmness loss after cold storage. During the shelf-life period, the activities of pectin methylesterase and polygalacturonase were lower in fruit treated with both treatments than in control fruit, which may result in higher cell wall integrity and, therefore, in fruit softening alleviation. The 1-MCP and HW-treated fruits exhibited higher catalase and lower peroxidase activities if compared to untreated fruit. While peroxidase activity was especially inhibited by 1-MCP, HWT exerted a more marked effect on the catalase enzyme. The changes in cell wall degrading and antioxidant system enzymes induced by 1-MCP and HWT-50 degrees C during the symptom development period reveal that these enzymes are involved in the chilling-tolerance of persimmon. (C) 2014 Elsevier B.V. All rights reserved.