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Food security is threatened in Southern Africa, because of unpredictable droughts and higher summer temperatures brought on by climate change and global warming. Durable and hardy plants that grow easily and quickly in such conditions must be adopted to ensure sustainable and reliable food supplies. The young cladodes (nopalitos) from the cactus pear plant, which adapts to hot and dry climates, is an underutilised alternative food source that can serve as a healthy vegetable. It thrives in many environments such as deserts, below sea level, high altitude regions and tropical regions with temperatures above 50°C. Nopalitos are a traditional staple vegetable and have been consumed in Mexico for over 9000 years. However, it is underutilised and unknown as an alternative vegetable in Africa. Research on the physiochemical and nutritional content has been conducted. However, the information on harvesting nopalitos from cultivars available in South Africa for optimal edible quality is not available. Good quality nopalitos are young, thin, bright green, soft, fresh and not too sour or slimy. This paper aims to identify the effect of and the interaction between size, cultivar and harvesting season to obtain optimal eating quality. Data were obtained for two cultivars (Morado and Fusicaulis) at 9 cm, 12 cm, 15 cm, 18 cm, 21 cm and 24 cm, which were harvested in spring (October) and autumn (March) over two years. The quality characteristics were translated into the measurable attributes of morphology (weight, width, diameter, volume and surface area), texture (firmness and compressibility), colour (L*, a*, b*, C*and h°), turgidity (moisture content, mucilage yield and viscosity) and gustatory (percentage titratable acidity, pH and total soluble solids). ANOVA and Principal Component Analyses were performed to determine significant differences and interactions between the length groups, two cultivars and two seasons. The results showed that the size, cultivar and season influenced the edible characteristics. Both cultivars were most tender at 15 cm and presented the best edible qualities in spring. Morado showed better colour, turgidity and gustatory qualities. Morado was thinner, a brighter green colour, less sour and less slimy compared to Fusicaulis nopalitos. • Nopalito quality is highly influenced by harvest size, cultivar and season. • At 15 cm, nopalitos from both Morado and Fusicaulis were the most tender. • Morado nopalitos was the preferred cultivar, but Fusicaulis also performed satisfactorily. • Spring harvest was preferable, but autumn harvest nopalitos were acceptable. • Morado was thinner, a brighter green colour, less sour and less slimy. [ABSTRACT FROM AUTHOR]

Climate change, limited water resources and expected population increases would require crops which contribute toward more resilient, more productive, more sustainable and climate-smart food systems. The cactus pear is a drought-resistant and sustainable food source to humans and livestock alike. Cactus mucilage has multiple applications in the food and packaging industry. It is eco-friendly, economical, functional and has multiple health benefits. However, the researchers observed umpteen variations in extracted mucilage yield and viscosity every time the cladodes were harvested, making the standardisation of formulations troublesome. We aimed to examine the effect of weather conditions on the physicochemical characteristics of cactus pear cladodes and mucilage extracted over two seasons to understand these observed variations in mucilage characteristics. Forty cladodes, ten from each of Opuntia ficus-indica Algerian, Morado and Gymno-Carpo and Opuntia robusta Robusta were harvested every month from February to August in Bloemfontein, South Africa. Daily weather data were obtained, weight and moisture contents determined on cladodes and yield, viscosity, pH, conductivity and malic acid content determined on extracted mucilage. Pearson correlation coefficients were calculated between the weather conditions, cladode properties, and mucilage properties. Contrary to common belief, neither increasing cladode weight as they grow, nor rainfall were the leading causes of mucilage inconsistencies. However, the correlations showed a relationship between environmental temperatures, cladode pH and conductivity, and mucilage viscosity and yields. In hot summer weather, the pH was lower, which led to an abundance of positive ions in cladodes. The H+ ions neutralise the negative charges along the outstretched mucilage molecule, causing it to coil up, reducing the viscosity of the mucilage. Thus, environmental temperatures rather than rainfall or cladode maturity influenced the physicochemical characteristics of mucilage. The findings should make an essential contribution in predicting the physicochemical characteristics of mucilage for specific food-related functions by observing the weather conditions. [ABSTRACT FROM AUTHOR]

Cactus pear fruit is a valuable source of antioxidants and could be an important functional ingredient in foods. Cultivars differ in fruit colour, which may indicate the presence of specific antioxidants. There is increased interest for cactus pear-derived products due to their potential nutraceutical effects, and determining antioxidant potential in processed foods is an important measure to ascertain the quality of a processed product. The aim of the study was to determine the relationship of fruit processing method and colour with antioxidant content and activity in fresh and processed cactus pear fruit. Antioxidant components (ascorbic acid, phenolic compounds, carotenes and betalains) and antioxidant activity (radical scavenging activity towards 2,2′-diphenyl-1-picrylhydrazyl and iron chelating capacity) were determined in fresh and processed (juiced, dried, preserved and chutney) fruits from four different coloured cultivars (purple, green, orange and pink). The highest antioxidant content and potential was found in purple (O. robusta cv Robusta) fruit products, attributed to the highest levels of betalains (1140.4 mg kg−1). Orange fruit (O. ficus-indica) products had the second highest levels, attributed to ascorbic acid and phenolics. Betalains were highly retained in all processed products, while ascorbic acid was mostly retained in the processed products that involved minimal heat treatment. Carotene and phenolic compounds became more available for extraction during processing and showed higher levels after processing. Principal component analysis makes it possible to identify fruit colours of fresh and processed products, which were mostly associated with a specific antioxidant. In the PCA biplot, PC1 (47.93%) and PC2 (21.93%) explained 69.15% of the total variation: a processing method rather than colour-correlated products in terms of antioxidant content and potential. PCA indicated that fresh purple fruit was correlated with chelating activity and betalains, while orange fruit was clustered with phenolics, ascorbic acid, carotene and DPPH. For the processed fruit products, most were clustered together with chelating activity, DPPH and the antioxidants. Orange and pink dried products had high ascorbic acid, phenolics, carotene and DPPH values, while dried and fresh purple fruit had high betalain content and chelating activity. [ABSTRACT FROM AUTHOR]

Natural food items and the additional benefits they provide have received considerable attention in recent years. Betalains are nutritious pigments which have valuable biological properties, e.g., antioxidant and free radical scavenging activity. In this study, aqueous betalain extracts were obtained from different coloured cactus pears (purple, red/pink, and orange), amaranth, and beetroot, with and without the addition of ascorbic acid, microwave-heated, and freeze-dried and subsequently analysed by thin layer chromatography (TLC). Beetroot samples without the addition of ascorbic acid (AA) had lower phenols, flavonoids, and ascorbic acid content than beetroot samples extracted with the addition of AA. Amaranth had significantly higher contents of antioxidants than all the other plants. Results for phenolic compounds showed that there were no significant differences between cactus pear cultivars, however, significant differences were seen between the two beetroot samples (microwave-heated with and without AA) as well as amaranth. For flavonoid compounds, amaranth had significantly higher values than all other samples. The lowest flavonoid content was found in beetroot without AA (0.49 mgCE/g). For ascorbic acid, significant differences were noticed between amaranth (71.71 mg/100 g) and samples from cactus pear and beetroot. TLC results showed that purple and red cactus pear samples had the most vivid colours, a reflection of the high betacyanin and betaxanthin contents in the cultivars. Moreover, extracts from cactus pear, beetroot, and amaranth were classified according to a decision tree which was designed by the Code of Federal Regulations/Food Additives Regulation of the EU. The classification of betalain pigment extracts as colouring foods was achieved through enrichment factor calculations and the colourant decision tree. The results showed that the betalain pigment extraction method used is inexpensive, time-saving, energy-saving, non-toxic, and chemical solvent free and yields high concentrations of betalains. [ABSTRACT FROM AUTHOR]