Abstract
Cactus pears are nutritious, drought-tolerant plants that flourish in hot and arid regions. All its plant parts can be consumed by humans and animals. Fruit seed oil production is an important emerging industry in South Africa. As part of an initiative to promote cactus pears as multi-functional crops, dual-purpose cultivars should be identified, and their production increased. The aim of this study was to investigate the role of nitrogen (N) fertilizer on the seed oil yield and quality of Opuntia ficus-indica. The project encompassed a trial using N fertilization from three N sources (limestone ammonium nitrate, ammonium sulfate, urea) and four N application levels (0, 60, 120, 240 kg ha−1). Oil was quantitatively extracted from the seed using the Folch method; fatty acids were quantified using a Varian 430-GC. Seed oil content significantly increased (p = 0.035) with increased N fertilization rates; the oil yield ranged between 7.96 and 9.54%. The composition of the main fatty acids (oleic, palmitic, cis-vaccenic and stearic acid) was significantly influenced; oleic and stearic acid were significantly increased by higher fertilization levels whereas a reducing trend was observed in palmitic and cis-vaccenic acid levels. The highest content fatty acid, linoleic acid, was not significantly influenced.
Highlights
A significant difference existed between the oil content of seed from plants not receiving any N (8.15%) and the seed of plants that were treated with urea at 240 kg N ha−1 (9.54%)
The oil content of seed from plants that were treated with ammonium sulfate (AmSul) at 60 kg ha−1 (7.96%) was significantly lower than the seed of plants treated with urea at 240 kg ha−1 (9.54%)
A similar trend was observed with tobacco; its seed oil content significantly increased with increased N fertilization levels (120, 180, 150 kg N ha−1 ) compared to the control (90 kg N ha−1 )
Summary
Spineless Burbank Opuntia ficus-indica is one of the most popular cactus pear species that grow in the arid and semi-arid regions of South Africa and is a noteworthy food source for humans and animals in these regions [1,2,3]. Fruit pulp processing of cactus pear leads to the discarding of the peels and seed as waste. New sources of oil and meal have been produced from these waste products [4,5]. Cactus pear fruits are valued for their distinctive flavour and aroma in addition to the nutritional properties of the oil in their seed. The Morado cultivar is one of the most popular cultivars in South Africa in relation to both human and animal consumption and food processing [6].
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