Myrtillocactus (cactaceae): botanical, agronomic, physicochemical and chemical characteristics of fruits

Abstract

Introduction. In Mexico, the Myrtillocactus fruit production levels are substantial, yet fruits are often under-used. Although the focus of interest is on their potential as food colourings, the fruits deserve more attention for their other food properties but information on their physico-chemical composition is scarce. To offer a baseline for the development of Myrtillocactus cultivation, we reviewed the information so far available. Botanical description. Four Myrtillocactus species have been identified and reported in the literature. They differ in shape, colour and other phenotypic characteristics. In Mexico, the predominant species is M. geometrizans, but M. schenckii also grows abundantly throughout the arid and semi-arid lands of the country. Cytological analyses performed on M. geometrizans showed that the plant is diploid (2n = 22). Agronomic aspects. Myrtillocactus species belong to the Cactaceae family. Because of their Crassulacean acid metabolism, they are able to grow in the arid and semi-arid highlands of Mexico. Myrtillocactus species have been propagated asexually by explants or cloning. Under controlled conditions, in vitro micropropagation from apical and basal explants gives rise to high yields. For cultivation, attention should be paid especially to minimum winter temperatures. Description of fruits and biochemical characterisation. The edible fruit is globular, with diameters reaching 1.5 cm. The pulp is gel-like, ranging in colour from glowing red to bluish. Chemical characterisation has mainly focused on betalain compounds, the predominant ones of which are betanin and betaxanthins. Contents are reported to be about 2.3 mg betalain·100 g^–1of pulp. Colour appears to be more stable than for red beets. Human consumption and commercial importance. In the production season (June to September), the fruits are found in all public markets in the states where they are grown. They are eaten either fresh or in processed forms. The commercialisation of the fruit is restricted mainly to rural production areas in certain states of Mexico. Conclusions. Our review establishes that published information on Myrtillocactus species is scarce and incomplete. The plant is under-utilised, despite its nutritional properties and commercial potential. Because they adapt easily to severely dry conditions, the Myrtillocactus species merit much more research.