Pre-storage Putrescine Treatment Alleviates Internal Browning of Stored Pear Fruit by Regulating Enzyme Activity

To investigate the preharvest putrescine (PUT) application effect on the storage life and internal browning (IB), the pear plants cv. ‘Punjab Beauty’ were sprayed with 1 mM, 2 mM and 3 mM PUT 14 days before fruit harvest. The untreated plants were sprayed with water and fruit were harvested as control. After harvesting, fruit were stored at 0–1 oC and 90–95% relative humidity for 75 days. The extent of IB along with changes in total phenolics content (TPC), colour value L* and a*, relative electrical conductivity (REC), malondialdehyde content (MDA), chlorophyll a and b (Chl a and b) and carotenoids content were measured on 0, 15th, 30th, 45th, 60th, 67th and 75th day of cold storage. The enzymatic activity of polyphenol oxidase (PPO) and peroxidase (POD) were also estimated during the study. The results revealed that higher POD while lower PPO activity with 2 mM and 3 mM PUT treatment led to the minimum IB in stored fruit as compared to untreated fruit. These treatments also maintained higher TPC, carotenoids content and preserved the colour changes along with chlorophyll content of pear fruit and reduced the EC and MDA content. Overall, preharvest 2 mM and 3 mM PUT applications could be an effective tool for prolonging the cold storage life and reducing the internal browning of pear fruit cv. ‘Punjab Beauty’.