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Keletso C. Mohale, Araya T. Hintsa, Machel A. Emanuel, and Fhatuwani N. Mudau

Bush tea (Athrixia phylicoides DC.) is a popular medicinal South African indigenous plant and it has been used for many decades as a health beverage and medicine. The objective of the study was to profile metabolites for assessment of quality of bush tea (A. phylicoides DC.) subjected to different pruning levels. Treatments consisted of untreated control, top-branch pruning, middle pruning, and basal pruning arranged in a randomized complete block design (RCBD) using 10 single trees as replications. The liquid chromatography quadrupole time-of-flight mass spectrometry (LC–QTOF–MS) was carried out to annotate the bush tea metabolites present in bush tea. Orthogonal partial least square-discriminatory analysis (OPLS-DA) from 1H nuclear magnetic resonance (NMR) revealed a separation between the basal, middle, top pruning, and the unpruned bush tea plants. The pruned (top) and unpruned tea plants, exhibited higher levels of metabolites than the basal and middle pruned. Pruning bush tea showed a significant effect on accumulation of secondary metabolites and thus could enhance bush tea quality. The study successfully annotated 28 metabolites (compounds), which elucidated canonical differences in pruning treatment of bush tea, as validated through multivariate analysis. Top pruning (apically pruned) resulted in improved metabolite accumulation than other treatment and can be recommended in bush tea cultivation. Future studies to enhance vegetative enhancement after pruning will be evaluated.

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Ambani R. Mudau, Puffy Soundy, Hintsa T. Araya, and Fhatuwani N. Mudau

The aim of the current study was to determine the influence of modified atmospheric pressure on the quality of baby spinach during storage. Treatments consisted of control [(normal air) (78% N2; 21% O2)], modified atmosphere (MA) (5% O2; 15% CO2; balance N2), storage temperature (4, 10, and 20 °C), and number of days after storage (0, 3, 6, 9, and 12). Parameters recorded are gas composition, weight loss, sensory quality, minerals and trace elements (Mg, Fe, and Zn), flavonoids, and antioxidant activity. The results of this study demonstrated that in the headspace gas there was overall reduction in O2 and increase in CO2 levels over the storage period. After 6 days of storage, all samples in normal air irrespective of the storage temperature were found to fall short of acceptable marketability with regard to visual appearance. The total antioxidant activity and flavonoids were well maintained under controlled atmosphere (CA) at 4 °C when stored for 9 days.

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Ambani R. Mudau, Puffy Soundy, Hintsa T. Araya, and Fhatuwani N. Mudau

Spinach is an annual, cool-season, green leafy vegetable that in temperate areas can be grown year-round. However, different seasons can influence the quality and shelf life of the produce. The objective of this study was to investigate the influence of different seasons on the quality of baby spinach leaves during growing and postharvest storage. The study was initiated in early Nov. 2013 and culminated toward the end of Oct. 2014, then was repeated from Nov. 2014 until Oct. 2015. A 4 × 5 × 3 factorial experiment was laid out in a randomized complete block design with four replicates per treatment. The treatments were arranged as follows. In autumn, winter, spring, and summer, leaves were kept up to 12 d at three different temperatures: 4, 10, and 20 °C. Parameters recorded are weight loss, leaf length, total flavonoids, and antioxidant activity. Results of the study demonstrate that the level of antioxidants in winter remained stable during storage, specifically at 4 °C, followed by autumn and spring. In contrast, the summer season reflected the worse potential of retaining a level of antioxidants compared with the other seasons. On day 12, at a storage temperature of 4 °C, winter maintained 0.55 mg·g–1 dry weight (DW), whereas autumn, spring, and summer had 0.41, 0.40, and 0.11 mg·g–1 DW, respectively. In conclusion, it is recommended that baby spinach growers consider winter, autumn, and spring for growing baby spinach to manage the quality favorably during the postharvest storage period in South Africa.

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Ambani R. Mudau, Mpumelelo M. Nkomo, Puffy Soundy, Hintsa T. Araya, Wonder Ngezimana, and Fhatuwani N. Mudau

Spinach (Spinacia oleracea) is a member of the Amaranthaceae family. Baby spinach leaves have a very high respiration rate, thus postharvest quality is affected mostly by tissue decay and the development of off-odors. Thus, this study was conducted to investigate the influence of storage temperature and time on the postharvest quality of baby spinach. Baby spinach leaves were harvested 36 days after planting and subsequently stored at 4 and 22 °C for 0, 2, 4, 6, 8, 10, or 12 days. Thereafter, the leaves were incubated for 72 hours at 40 °C to dry. Minerals, trace elements, total phenols, total carotenoids, flavonoids, and antioxidant activities were measured. Concentration of magnesium (Mg), zinc (Zn), and iron (Fe) were declined after 8 days of storage at 4 °C, while at 22 °C they declined after 2 days of storage. Mg, Zn, and Fe revealed a similar trend with significantly higher carotenoids found up to 6 days in storage at 4 °C, while at 22 °C the carotenoid levels declined after only 2 days. Total phenolic compounds gradually decreased in samples stored at 4 °C. However, samples stored at 22 °C showed a rapid decrease after 4 days. Both total antioxidant activities and vitamin C content showed a similar trend, with the content remaining constant at 4 °C and decreasing after 6 days, whereas the total antioxidant activities and vitamin C for leaves stored at 22 °C decreased immediately after 2 days. Results demonstrated that quality of baby spinach deteriorates as storage time and temperature increase.