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Increasing storage life of Plums

     

        Introduction : Post harvest losses of fruits in the Ontario fruit growing region is a serious problem and there has been research done in this field to increase the post harvest storage life. Though the plum fruits, peaches and nectarines can be stored in cold storage, they exhibit cold injury symptoms and they lose their nutrient content and there is a loss of carotenoids, fruit color and there are chances of fungal and bacterial disease pathogens. Hence, there is a need to develop new methods to extend the post harvest storage, to increase the marketability and the storage of these fruits for a longer time. My research is going to focus on using various chemical treatments especially with hexanal and 1-MCP during both pre and post harvest stages to see if there is any beneficial effect on these crops. As these chemicals are expected to delay ripening, the same energy will be rerouted and used in other biochemical pathways in plants. Hence, the fruits will also be checked to see whether there is an increase in the total phenolics and antioxidant levels of the fruit.

Research Objectives

        To increase the post harvest life of the fruits grown in the Ontario by using various preharvest and post harvest methods- chemicals such as hexanal, 1-MCP.
        To improve and/or retain the nutrient contents of the fruit (phytochemicals like carotenoids).
        To increase the levels of beneficial antioxidant enzymes
        To improve and or/maintain the marketable and visual characteristics of the fruit such as fruit color, firmness, texture.

Materials and Methods

        Plum fruit trees will be selected at random in an orchard. Preharvest and post harvest sprays of hexanal and 1-MCP will be done to examine their effects in increasing the post harvest storage life and quality parameters. Enhanced freshness formulations have been developed to to enhance and retain the quality parameters. There are many essential oils, phytochemicals used in this formulation. There is a chance to improve the freshness formulation using other essential oils and weed extracts such as barberry and other plant components. All these treatments will be done in tripicate using a completely randomized design. Various tests will be performed to check for the nutritional status of the fruits Color- It will be assessed by the Minolta color chart. Hue and chroma color components) will be calculated. Firmness-A penetrometer will be used. Soluble solids-A refractrometer will be used. The total phenolic content is estimated to know the nutritional status of the fruits. The extraction of polyphenols will be done with water and ethanol and the Total Phenolic Content is estimated by the Folin Ciocalteau Assay. The anthocyanins and polyphenols are separated using HPLC-MS. Characterization and quantification of the different anthocyanins present is done. Antioxidant Assays-Antioxidant activity is an important parameter that has to be assessed to check whether the nutrient content of the fruit corresponds with the antioxidant activity of these fruits ORAC, DPPH and FRAP assays will be done to assess the antioxidant capacity of the phytochemicals. Protein extraction will be done to assess the antioxidant enzyme activity. The total protein concentration will be measured by Bradford method. Superoxide dismutase and Ascorbic peroxidase are important enzyme required to catalyze the conversion of the reactive oxygen species to harmless compounds. These contents will be assessed as well. The content of these antioxidant enzymes will be assessed. Phospholipase D is an enzyme which facilitated phospholipid membrane degradation. It has been shown that Phospholipase D inhibition increases the shelf life of the fruits. Hence this is another enzyme that is going to be assessed.

Significance of my Research

        The tender fruit industry in Ontario comprising mainly of plums, peaches, nectarines and cherries produce about 10,000 metric tonnes annually and produce is worth more than 20 million dollars. Since post harvest life is an important aspect of its marketability, price and profit, it is imperative to develop new methods to increase the storage life of this produce. Methods to increase the post harvest storage life and retaining the beneficial nutrient content in the produce will greatly benefit the farmers of Ontario and other provinces as well as it helps to increase the storage, hence, increasing the marketability of the produce and other fruit characteristics.

Place : Vineland Station, Dept. of Plant Agriculture, Ontario Agricultural College, University of Guelph, Ontario, Canada

Supervisors: Dr. Jayasankar Subramanian, Dr. J. Alan Sullivan