Browsing by Author "Riva, Shannon Claudia"
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- ItemEfficacy of edible coatings in alleviating shrivel and maintaining quality of Japanese plum (prunus salicina lindl.) during export and shelf life conditions(MDPI, 2020-07-16) Fawole, Olaniyi Amos; Riva, Shannon Claudia; Opara, Umezuruike LinusThe effect of six edible coatings were investigated on the ability to alleviate shrivel and extend shelf life of plums. Fruit were subjected to a simulated shipping period (−0.5 ± 2 ◦C and 90 ± 5% relative humidity (RH)) for five weeks and a subsequent shelf life period (20 ± 2 ◦C and 80 ± 5% RH) for 20 d. Overall, the study showed that it is possible to alleviate shrivel and also extend shelf life of plum (‘African Delight™’) at export and shelf life conditions. Amongst the edible coatings investigated, the findings in fruit coated with gum arabic and the commercial products were comparable and promising for postharvest preservation of the investigated plum cultivar. The coatings showed a moderate delay of fruit ripening, significantly reduced weight loss and shrivel development, allowing for the export of fruit over a long distance (five weeks) and up to 20 d of shelf life.
- ItemPostharvest application of edible coatings to reduce quality losses and prolong shelf life in plums(Stellenbosch : Stellenbosch University, 2019-12) Riva, Shannon Claudia; Fawole, Olaniyi Amos; Opara, Umezuruike Linus; Stellenbosch University. Faculty of Agrisciences. Dept. of Food Science.ENGLISH ABSTRACT: The Japanese plum (Prunus salicina Lindl.) is one of the most popular stone fruits consumed worldwide, characterised by its distinctive taste and high nutritional value. However, postharvest losses limit the economic value of exported plums, with the long handling chain of export and sale often resulting in shrivel, overripeness and decay. Whilst postharvest technologies such as low temperature storage and high density polyethylene (HDPE) bags are used to delay ripening and minimise moisture loss in exported plums, the incidence of fruit rejection on account of quality- related issues is still unfavourably high. Edible coatings have been widely reported to maintain postharvest quality in fresh produce. Coatings form a semi-permeable barrier on the fruit surface that controls moisture loss and gaseous exchange, consequently delaying ripening and extending shelf life. This study aimed to investigate the potential of edible coatings to improve the export quality of plums by controlling postharvest losses and extending shelf life. In a laboratory-scale trial, six edible coatings, four of which were experimental (alginate, chitosan, gellan gum and gum arabic) and two commercial (High shine and Sta-fresh), were screened during a simulated shipping period (-0.5 ± 2°C and 90 ± 5% RH for five weeks) and a subsequent shelf life period (20 ± 2°C and 80 ± 5% RH for 20 days) using ‘African Delight™’ plums. Gum arabic performed best out of all the coatings. At 20 d shelf life, weight loss was significantly (p<0.05) reduced from 23.62% in control plums to 5.36% in plums coated with gum arabic. Similarly, shrivel was significantly (p<0.05) reduced from 9.56% (control) to 4.91% (gum arabic), and decay was significantly (p<0.05) reduced from 7.57% (control) to 1.19% (gum arabic) at 20 d shelf life. Additionally, plums coated with gum arabic exhibited a delay in physico-chemical changes during storage, such as fruit softening, loss of acidity and darkening of the peel colour. These changes were delayed as a result of suppressed respiration and ethylene production, which consequently reduced the rate of fruit ripening. At 20 d shelf life, plums coated with gum arabic resembled control plums at 5-10 d shelf life, indicating an extension of shelf life as a result of coating application. Furthermore, a volatile analysis confirmed that coating application did not result in the formation of off-flavours. In order to validate the commercial viability of coating application and optimise coating formulation, gum arabic (GA) based coatings, including GA 2%, GA 5%, GA 10%, GA 5% + pomegranate seed oil and GA 5% + ascorbic acid, were applied to ‘African Delight™’ plums in a commercial packhouse. Commercial pack lines are generally equipped with atomizers to apply postharvest solutions such as fungicides; therefore, coating application on a commercial-scale is highly viable and would not require additional infrastructure. Fruit were subjected to real-life postharvest handling practices, and quality was assessed during a simulated shipping period (-0.5 ± 2°C and 90 ± 5% RH for six weeks) and a subsequent shelf life period (20 ± 2°C and 80 ± 5% RH for 15 days). The best performance was achieved with GA 10%, which resulted in a significant delay in physico-chemical changes during storage such as fruit softening, loss of acidity and darkening of the peel colour. These changes were delayed as a result of suppressed respiration and ethylene production, which consequently reduced the rate of fruit ripening. Plums coated with GA 10% were described by a trained sensory panel during descriptive sensory analysis as having unripe to semi- ripe sensory attributes at 5 d shelf life, compared to control plums which were characterised with a ripe to overripe sensory profile. This suggests that GA 10% could extend the shelf life of ‘African Delight™’ plums beyond the current five day end point of commercial sale. This observation was confirmed in the instrumental measurements, where fruit coated with GA 10% retained firmness (14.04 N), peel colour (L* = 34.67 and h° = 6.37) and TSS (15.60 °Brix) after 15 d at shelf life conditions. No off-flavours were detected in the sensory analysis as a result of coating application. Plums coated with GA 10% were also found to be microbially safe at 5 d shelf life, with no faecal coliforms detected and total coliforms falling within specified limits. Furthermore, coatings exhibited potential as a green replacement technology for HDPE bags. No significant difference (p≥0.05) in respiration rate was observed between coated fruit packed without HDPE and control fruit packed with HDPE bags at the end of cold storage. Thus, coatings may have created a similar modified atmosphere in plums as that created by the HDPE bags within the carton, which resulted in comparable physico-chemical changes during cold storage. Although the commercial viability and technological readiness of GA 10% as a postharvest edible coating is limited in this study, the use of gum arabic in postharvest edible coating application is promising.