Thesis (M.Sc.( Agriculture (Horticulture)) -- University of Limpopo, 2022 / Avocado fruit ‘Hass’ exocarp changes colour from green to purple and black during
ripening. However, uniform purple or black exocarp colour is not achieved during
ripening, leading to consumers' rejection of fruit for not meeting quality standards.
Avocado ‘Hass’ fruit harvested early remain green or develop a multicoloured
appearance, concurrently devaluing their commercial value; and, therefore, unattractive
to consumers. Therefore, this study aimed to investigate the role of sucrose and calcium
postharvest pulsing on early matured ‘Hass’ avocado exocarp colour change during
ripening. In this study, early matured ‘Hass’ avocado fruit were harvested from Halls and
Sons, Mataffin farm (25°25’39.13” S, 30°55’52.84” E), Nelspruit, South Africa with 10 cm
pedicel at commercial dry matter content (22%). Thereafter, the fruit were transported to
the University of Mpumalanga laboratory. In the laboratory, the study was divided into
two experiments: Experiment 1 ‘Hass’ fruit were continuously infused through the
pedicel with different sucrose concentrations; 0 (control), 0.2 and 0.5 mM L-1.
Experiment 2 fruit were infused with different calcium chloride (CaCl2) concentrations; 0
(control), 2 and 3 mM L-1. In both experiments, treated and untreated fruit were stored at
5.5°C for 28 days. After removal from cold storage, fruit were ripened at room
temperature (±25°C) and evaluated every other day for firmness, subjective colour
(visual colour), objective colour parameters (lightness-L*, chroma-C* and hue angle-
h°), external chilling injury and ripening percentage. The results showed that Su (0.2
mM L-1) pulsing extended the ripening period by one day, corresponding with
maintained fruit firmness. Furthermore, Su (0.2 mM L-1) treated fruit reduced the ‘Hass’
avocado fruit chilling injury index (CII) during cold storage. With respect to colour
change, Su (0.5 mM L-1) treated fruit developed purple colour when compared with Su
(0.2 mM L-1), which only developed to olive colour on the final ripening day (day 6). In
addition, the results showed that all sucrose concentrations had a significant decreasing
effect (P < 0.05) on objective colour parameters (L*, C* and h°) and increasing visual
colour rating. With respect to CaCl2 treatments, fruit firmness decline was significantly
delayed, which resulted in extended ripening time. Moreover, CaCl2 (2 and 3 mM L-1)
significantly decreased (P < 0.05) pericarp objective colour parameters (L*, C* and h°)
and increased visual colour rating and developed purple colour on the final ripening day
(days 6 and 8, respectively). In addition, pulsing with CaCl2 (2 and 3 mM L-1)
concentration reduced chilling injury during storage compared with control fruit. In
conclusion, the results of this study indicated that Su and CaCl2 applied as postharvest
treatments may contribute to avocado colour development by increasing anthocyanin
accumulation. However, future research is required to investigate whether these
treatments affect anthocyanin biosynthesis at the gene level.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ul/oai:ulspace.ul.ac.za:10386/3982 |
| Date | January 2022 |
| Creators | Chuene, Dipuo Rebecca |
| Contributors | Mathaba, N., Mafeo, T. P., Shikwambana, K. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | xiii, 69 leaves |
| Relation |
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