Horticultural Science

Permanent URI for this communityhttps://hdl.handle.net/10413/6545

Browse

Now showing 1 - 4 of 4

Antioxidants composition of moringa (moringa oleifera lam) in different plant organs.
(2015) Mohammed, Fatima Abdelkarim Abdelrahman.; Tesfay, Samson Zeray.
Moringa oleifera Lam. is a versatile plant with various benefits; different parts of the plant have different pharmacological activity such as flavonoid, alkaloids, phenol, and carotenoids. The aim of the seed study was to investigate phytochemicals composition change and their utilization during seed and seedling germination. Seeds were germinated using three different temperature regimes (30/20 °C, 25/15 °C and 20/10 °C). Spectrophotometric determination of proline and phenols was carried out, while sugars were analyzed using HPLC-RID. The data were collected and analyzed using statistical software GenStat 14.1. Results of seed showed significant differences on speed of seed germination at temperature of 30/20°C followed by 25/15°C and 20/10°C respectively. Seed carbohydrates composition changes were observed with germination hours sucrose concentrations peaked within 24h (16 mg/g DW) and the same sugar showed sharp decrease for 96h (6.4 mg/g DW). Glucose and fructose concentrations also increased for 96h (2-6 mg/g DW). Also temperature had significantly influenced the biosynthesis and accumulation of biochemical compounds in the seeds especially 30/20°C. Temperature 30/20°C, increased seed phenols and proline concentration. Phenols and proline started to accumulate at 72h, after seed germination presumed within 48h. Results of leaves showed that Temperature also had significant effect on phenols the proline concentration particularly, 35/18°C, followed by 30/15°C, 25/12°C. The antioxidant levels of post germination phase was investigated, the result showed significant differences in antioxidant concentrations and sugar distribution in various parts of Moringa seedling. The leaf was recorded the highest antioxidant concentration (1.7 mg g-1). Moringa leaf also recorded the highest total phenols. The highest sugar concentration was found in root (258.9 mg g-1), and stem (245.72mg g-1) followed by root and seed. The highest concentration of total crude protein (110.4mg g-1) and vitamin E (28.57 μg g-1) was found in seed. The carotenoids concentration was the highest in the root (29 mg g-1). The result also showed different nutrients at various concentrations on different parts of Moringa tree. High phosphorous accumulated in leaf and seed; Potassium accumulation was found in root, stem, and seed coat. It is concluded that temperature treatments of Moringa seed and leaves resulted in significant differences in the rate of germination and biochemical compounds. Furthermore, the present study showed that Temperature plays an important role in germination seed and development of M. oleifera and antioxidants, phenolic, proline and carbohydrates contents. Further research on the effect of temperature on germination of M. oleifera and biochemical compound is therefore recommended.
Assessing gaseous ozone and edible coatings as postharvest treatments for mango (mangifera indica L.) fruit.
(2021) Bambalele, Nonjabulo Lynne.; Mditshwa, Asanda.; Magwaza, Lembe Samukelo.; Tesfay, Samson Zeray.
This research examines the potential of gaseous ozone and edible coatings in preserving postharvest quality and extending the shelf-life of ‘Keitt’ mango fruit. A critical review of the literature focused on the recent postharvest technologies used to preserve the quality of mango fruit. The prospects of using non-chemical postharvest treatments such as gaseous ozone and edible coatings were also reviewed. A screening study was conducted to determine the optimum ozone (O3) application time for effectively maintaining fruit quality and extending shelf-life. Mango fruit were intermittently exposed to gaseous ozone for twelve, twenty-four, thirty-six, or forty-eight hours, and the control fruit were untreated. Fruit were stored at 10℃ for twenty-one days and seven days shelf-life at ambient temperature. The findings showed that the O3 treatment should be applied at the pre-climacteric stage to achieve optimum results. Ozone treatment for 24 or 36 hours effectively maintained firmness and carotenoids content, delayed color changes, decay incidence, and mass loss. Therefore, an ozone exposure time of 24 and 36 hours was adopted for the study. These exposure times were incorporated into edible coatings (moringa leaf extract and carboxymethyl cellulose) for further investigation. The study on the effect of gaseous O3 incorporated with edible coatings on sensory attributes and physicochemical parameters showed that EC and EC + O3 (36 h) were more effective in delaying the ripening process and maintaining the postharvest quality. Overall, consumers preferred the fruit coated with EC due to its attractive color, smell, and sweetness. The study on the postharvest effect of gaseous O3 and EC on antioxidants and the biochemical properties of mango fruit is discussed in Chapter Five. The findings of this study demonstrated that the treatment combination of EC and gaseous O3 (36 h) effectively maintained antioxidants, membrane integrity and enhanced the quality of mango fruit during storage. The effect of gaseous O3 and EC on postharvest diseases of mango fruit, specifically Colletotrichum gloeosporioides (anthracnose) and Lasiodiplodia theobromae (stem-end rot), was also investigated. This study revealed that EC + O3 (24 h) effectively controlled stem-end rot and anthracnose in mango fruit. The treatment combination of EC and O3 (36 h) reduced the mycelial growth and disease incidence of Lasiodiplodia theobromae and Colletotrichum gloeosporioides. The study of EC and O3 in the volatile compounds of mango fruit is discussed in Chapter Seven. The fruit treated with EC had a high content of volatile compounds compared to other treatments. The treatment combination of EC + O3 (24 h) was not effective in maintaining the volatile compounds of mango fruit during storage. The findings of the current study suggest that EC + O3 (36 h) can be used as postharvest treatment of mango fruit. Additional research is required to gain more insights in understanding the EC+ O3 mode of action in maintaining volatile compounds and controlling mango postharvest diseases.
A comparative study of antioxidant potentials of some leafy vegetables : emphasis on African leafy vegetable and exotic vegetables.
(2014) Mathe, Sakhile.; Tesfay, Samson Zeray.
Due to malnutrition and food insecurity problem around the globe, mainly in developing countries, cheap nutritional food sources are required. In South Africa, a large proportion of the population is considered “poor” and with limited resources. However, South Africa as a whole is rich in indigenous leafy vegetables which have the capacity to help mitigate the problem of malnutrition and food insecurity. Amaranthus hybridus, an African indigenous leafy vegetable was tested for seed quality and potential essential antioxidants. Exotic (to Africa) leafy vegetables (Brassica oleracea and Brassica oleracea var. capitata f. rubra) were used as references for potential antioxidants. Amaranthus hybridus seed quality was tested using two different coloured seeds, red and white gold. Seed viability and vigor were tested using germination, electrolyte leakage and antioxidant content. Data recorded indicated better seed quality for red seeds than white gold seeds; therefore red coloured seeds were planted along with purchased Brassica oleracea and Brassica oleracea var. capitata f. rubra for quantifying antioxidant content. Selected antioxidant types were measured on weekly harvests of the studied vegetables. From the results it was evident that the indigenous leafy vegetable amaranth with total antioxidants [FRAP(3174.91 mmol Fe2 SO4 100g-1 DW) and DPPH(8.3 mmol trollox 100g-1)], proteins (6.88 mg.g-1 DW), total phenols ( 345 mg 100g-1 DW), flavonoids (79 mg 100g-1 DW), Chlorophyll and carotenoids (2.8 mg 100g-1 DW), ascorbic acid (86 mg 100g-1 DW) and soluble sugars (1.07 Brix %), could be used in conjunction with available commercial leafy vegetables to combat malnutrition and food security problems. Further, these results indicate that in resource limited regions this vegetable can act as a main source of nutrients and a supplement in resource abundant regions of the country and/or continent. Further, analysis of selected enzymatic antioxidants was carried-out on leaf material of the studied vegetable to evaluate the capability of indigenous leafy vegetables to protect themselves against oxidative damage. Indigenous leafy vegetables exhibited high antioxidant activity against lipid peroxidation at early stages of growth and high antioxidant enzyme activity at similar stages thus high capability of mitigating ROS effect. Data obtained from the study indicated that indigenous vegetables are a good source of essential antioxidants which are beneficial to human health; therefore the intensity of their use needs to be increased, especially in areas of high prevalence of malnutrition and diseases.
Efficacy of enhanced freshness formulation as a novel postharvest treatment for gold kiwifruit (actinidia chinensis)
(2023) Mthembu, Sisanda Sibusiso Luyanda.; Mditshwa, Asanda.; Magwaza, Lembe Samukelo.; Tesfay, Samson Zeray .
When exporting kiwifruit, the main limiting factors are excessive fruit softening and fungal decay. Furthermore, exposing kiwifruits to low temperatures induces the mechanisms involved in the softening process. In addition, kiwifruit become much more susceptible to fungal decay as they soften, which exacerbates deterioration of kiwifruit during transit. Fruit firmness is an important criterion for the market value of kiwifruit and storage life for the wholesale and retail trade. Therefore, loss in firmness is a serious problem resulting in postharvest and economic losses. Given that cold storage alone is not enough to optimise firmness retention of kiwifruit, the current study aimed to investigate the capacity of enhanced freshness formulation (EFF) to reduce kiwifruit softening. Kiwifruits were subjected to eight weeks of storage at 0 °C and 90 % relative humidity, followed by one week at ambient storage. The efficacy of EFF to regulate the mechanisms behind the softening process such as cell wall degradation, membrane deterioration and fungal infection was evaluated. Furthermore, the efficacy of EFF to preserve bioactive compounds was also evaluated to assess the effect of this treatment on these highly appreciated quality attributes. The first study evaluated the efficacy of EFF to delay softening of kiwifruit harvested at both the mid and late maturity stage. The influence of EFF on cell wall polysaccharides (CWPs) and cell wall degrading enzymes (CWDEs) was assessed. The findings showed that EFF optimised firmness retention of kiwifruit by preserving CWPs through the suppression of CWDEs which are responsible for initiating fruit softening. Furthermore, EFF maintained fruit quality and marketability, characterised by significantly lower mass loss, total soluble solids and higher titratable acidity. The second study examined the capacity of EFF to inhibit the excessive production of reactive oxygen species (ROS) which induce membrane damage, resulting in softening and senescence. EFF treatment effectively delayed the progression of kiwifruit senescence by reducing membrane deterioration and the accumulation of ROS. The mechanism by which EFF reduced membrane damage caused by ROS was attributed to its capacity to enhance the activities of antioxidant enzymes involved in neutralising ROS and suppressing Phospholipase D which destroys membrane integrity, resulting in improved storability of treated fruit. The third study assessed the efficacy of EFF to inhibit the fungal growth of Botrytis cinerea, which one of the major postharvest pathogens of kiwifruit that contribute to excessive softening. The findings show that EFF effectively suppressed the fungal growth of Botrytis cinerea in a dose -dependent manner. The results demonstrate that EFF can serve as a potential disease control strategy for kiwifruit at the postharvest stage. The mechanism by which EFF suppressed fungal decay can be attributed to the treatment’s capacity to induce disease resistance against Botrytis cinerea, by enhancing the synthesis of secondary metabolites and the action of defence-related enzymes, thus conferring greater protection against pathogen attack. The fourth study investigated the ability of EFF to retain the antioxidant quality of kiwifruit during prolonged storage. The bioactive compounds of EFF-treated kiwifruits were effectively maintained throughout the storage period. The findings of the present study further revealed that the mechanism by which EFF optimises antioxidant retention is due to its ability to regulate enzymes involved in the synthesis and oxidation of bioactive compounds. Despite the positive results, further research on transcriptome analysis is needed to elucidate how EFF regulates softening and antioxidant enzymes.

Browse

Browsing Horticultural Science by Subject "Antioxidants."