Browsing by Author "Mokapane, Faith Moleboheng"

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    Effects of pre-treatments to preserve quality attributes and prolong shelf-life of dried pomegranate arils
    (Stellenbosch : Stellenbosch University, 2021-03) Mokapane, Faith Moleboheng; Fawole, Olaniyi Amos; Opara, Umezuruike Linus; Stellenbosch University. Faculty of Agrisciences. Dept. of Horticulture.
    ENGLISH ABSTRACT: The pomegranate fruit (Punica granatum L.) is a lucrative horticultural crop, which is rich in nutrients and phytochemical compounds. Fruit with physical defects such as sunburn and cracks pose a threat to the competitiveness of the South African pomegranate industry. Such fruit are undesirable to consumers and are thus regarded as second grade or waste. Fruit waste may be prevented by drying arils for marketing as healthy snacks. However, the process of dehydration involves heat application that may degrade beneficial phytochemicals and textural components of the fruit. The aim of this study was, therefore, to investigate the potential of pre-treatment use for the development of dried pomegranate arils. The pre-treatments under study were blanching at different temperatures and duration as well as chemical pre-treatments of ascorbic acid and citric acid at different concentrations and dipping times. Pre-treatments significantly affected drying characteristics. Blanching at higher temperatures (85 or 100 °C) for longer dipping times of 30 s increased the percentage moisture loss and drying rate. In contrast, chemical pre-treatments were found to have higher effective moisture diffusivity (Deff). The parabolic drying model had a better fit for all pre-treatments based on higher root mean square error (RMSE), chi-square (χ2) and coefficient of determination (r2). Citric acid (0.2 and 0.4 %) and 100 °C (10 s and 20 s) blanching pre-treatments had significant effects on the rehydration capacity. A further study on storage of dried arils revealed that quality parameters were significantly affected by pre-treatment application. Red colour (a*) of arils improved from the beginning of storage to month 5, with citric acid pre-treatment having the highest value. As storage progressed, dried arils became less sticky across all pre-treatments. Untreated arils were significantly harder (higher maximum compression force) while blanching at 100 °C for 20 s resulted in arils with the lowest compression force. Soluble solids (SS) content of arils decreased with increase in storage duration, and untreated arils retained the highest SS content. Blanched arils had increased acetic acid, while untreated samples had the highest abundance of furfural. In summary, this study showed the potential for the use of pre-treatments to produce dried arils with better retention of phytochemical content (TPC and TFC). Application of blanching pre-treatments at higher temperatures reduced drying time and aril texture but did not retain the red colour of dried arils. Overall, citric and ascorbic acid pre-treatments, respectively, maintained arils redness and total anthocyanin content. Future studies may focus on combining treatments to produce an additive effect, and a more extended storage trial may be explored to simulate long-term storage and handling as commonly practised in industry.