Yusuf, Murad (2022) Development of Predictive tests for Determination of Shelf Life for Citrus Fruits. PhD thesis, Victoria University.

Abstract

The main focus of this project has been on the development of better understanding of the potentially devastating damage caused by cold winter freeze to growing citrus fruits. Fruit such as oranges are extremely important to the Australian fruit industry, and the establishment of such an investigation to address the current losses in this area is overdue. Any significant advancement towards better understanding and improvement in this problem area will be welcomed, and this work, using methods based in scientific analysis and visual investigation, has been mounted to contribute to this need. The cultivars investigated during the period 2007-13 were Navel and Valencia sweet oranges, two of the most important species in the citrus fruit industry. Every experimental method used in this investigation consists of two parallel investigations. The first study involves the development of simulated treatment in the laboratory, through techniques based on controlled freeze treatment with various sub-zero temperatures. In summary, the study found that emission of ethanol and other compounds could be observed following the freeze treatment of orange fruit, and these emissions were demonstrated to be predictive of damage to the fruit that will be present following a three-week period of storage. This finding strongly suggests that one or more of these volatiles could be used as analytical indicators to evaluate the degree of damage that has been caused during the frost damage that has occurred in a damaging freeze. The detection of ethanol emanations and the observations of internal and external changes that have resulted because of frost-damage conditions will also help to formulate quality control process needed for confident retailing of these fruits. It is recommended that further research needs to more closely ascertain whether these volatiles can be useful in the evaluation of damage to naturally frozen oranges.

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