Summary
Consumers are increasingly avoiding foods containing synthetic colourants, which lead food industries to replace them by natural pigments, such as carotenoids, betalains, anthocyanins and carminic acid. Betalains are water-soluble nitrogen-containing pigments, composed of two structural groups: the red-violet betacyanins and the yellow-orange betaxanthins. This review synthesises the published literature on basic chemistry of betalains, their sources and chemical stability. Moreover, several works are mentioned which have demonstrated the potent antioxidant activity of betalains, which has been associated with protection against degenerative diseases.

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Betalains: properties, sources, applications, and stability ? a review.

Draw solutions for forward osmosis processes: Developments, challenges, and prospects for the future

In recent years, food coloring with artificial colorants has been increasingly disapproved by consumers In return, application of coloring foodstuffs, among them betalain-containing fruits and vegetables, has gained importance for the food industry As commonly true for natural pigments, betalains are afflicted with inferior stability compared to synthetic dyes Especially temperature, oxygen, and light are known to exhibit detrimental effects on betalain integrity, while certain antioxidants and chelating agents may act as stabilizers Only recently, several studies expanded the knowledge on betalain degradation pathways, especially focusing on betacyanin decomposition Additionally, new findings on stability and stabilization of betalains in cactus fruit juices extended the application range of betalainic foodstuffs Focusing on betacyanins, the present review discusses betalain degradation mechanisms and provides a survey of compounds and conditions governing betalain stability in a beneficial or an unfavorable way Finally, strategies for maintaining the chromatic properties and tinctorial strength of betalain-based juices and pigment preparations as well as tools for color modulation by targeted betacyanin degradation are discussed

Betalain stability and degradation--structural and chromatic aspects

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Original article Betalains: properties, sources, applications, and stability - a review

Natural products and health foods have recently received a lot of attention both by health professionals and the common population for improving overall well-being, as well as in the prevention of diseases including cancer. In this line, all types of fruits and vegetables have been re-evaluated and recognized as valuable sources of nutraceuticals. The great number of potentially active nutrients and their multifunctional properties make cactus pear (Opuntia spp.) fruits and cladodes perfect candidates for the production of health-promoting food and food supplements. Although traditionally appreciated for its pharmacological properties by the Native Americans, cactus pear is still hardly recognized because of insufficient scientific information. However, recent studies on Opuntia spp. have demonstrated cactus pear fruit and vegetative cladodes to be excellent candidates for the development of healthy food. Therefore, this review summarizes current knowledge on the chemical composition of Opuntia cacti with particular emphasis in its use as food and medicine.

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Nutritional and medicinal use of Cactus pear (Opuntia spp.) cladodes and fruits.

The present work aimed both at improvement and extension of a previously developed process for the production of cactus pear juice. The total yield was increased by 10% through processing whole instead of peeled fruits and by further optimisation of pulp enzymation. As an alternative to HTST pasteurisation, cross-flow microfiltration was applied for non-thermal cactus pear juice preservation. Juice concentrates and fruit powders were produced by rotary evaporation and freeze drying at laboratory scale and compared to products obtained at pilot plant-scale applying a three-stage column evaporator and spray drying, respectively. To monitor process-related quality changes, the resulting products were characterised in terms of colour and selected quality parameters. For both juice concentrates and fruit powders, initial colour characteristics were retained. In addition to betanin isomerisation, C 11 -epimerisation of proline-betaxanthin was demonstrated to be a valuable indicator of the respective heat treatment applied. Whereas no adverse reactions were observed during juice production, non-enzymatic browning and HMF formation were found after concentration at pilot plant-scale and freeze drying, respectively. Industrial relevance Although cactus pear meets all requirements for food colouring purposes, no attempt has been made so far to exploit this potential. The feasibility of processing cactus pear juice into concentrates and fruit powders was demonstrated in this study. In contrast to single-strength juice, concentrates and powders are easier to handle during transportation and storage and also open further fields of application that may promote cactus pear fruit processing at industrial scale in the future.

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Evaluation of different methods for the production of juice concentrates and fruit powders from cactus pear

Crops with additional health-promoting and nutritional benefits, such as cactus pears, are increasingly gaining momentum both for health professionals and consumers (Feugang et al., 2006). Cactus pear fruits are rich in betalains, taurine, minerals, and antioxidants, and thus fit well this trend. Hence, it is considered and are predicted a promising future crop for commercial food applications. In this light, a sound knowledge of the physical and chemical characteristics of cactus pears as well as their current and potential future uses are needed. However, data are scattered and often difficult to access. Therefore, the present review summarizes data from the literature and points out promising areas of research.

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Cactus Pear Fruits (Opuntia spp.): A Review of Processing Technologies and Current Uses

Since no process has yet been established for the production of cactus pear juice, the present work aimed at the development of a betalain-based colouring foodstuff from Opuntia ficus-indica cv. ‘Gialla’ and cv. ‘Rossa’ of two seasons applying unit operations typical for fruit juice production. Complete separation of the peels from the pulp and removal of seeds were achieved by carborundum peeling of the frozen fruits and subsequent passing through a finisher. Furthermore, for improved filtration of cactus pear juice different enzyme preparations were tested to degrade pectic-like substances. To monitor quality changes in the course of processing, juice samples were analysed after each processing step in terms of colour and selected chemical parameters. While lightness (L*) and chroma (C*) increased during processing for both cultivars, hue angle (h°) remained unchanged for the yellow cultivar ‘Gialla’, but a slight shift towards red was observed for the red cultivar ‘Rossa’ after pasteurisation. Unexpectedly, even after repeated thermal treatment neither non-enzymatic browning nor HMF formation was observed in juices from both cultivars. Industrial relevance Cactus pear represents a viable alternative to red beet for food colouring purposes: it neither exhibits negative sensorial impact nor high nitrate levels, but offers a broad colour range. However, no attempt has yet been made to benefit from this potential. The process developed is considered suitable for being scaled up to industrial-scale production thus opening an avenue for large-scale cactus pear fruit processing.

Development of a process for the production of a betalain-based colouring foodstuff from cactus pear

Colour studies on fruit juice blends from Opuntia and Hylocereus cacti and betalain-containing model solutions derived therefrom

The impact of heating at 75, 85, and 95 °C during 60 min on overall color and betalain retention of yellow-orange cactus pear (Opuntia ficus-indica[L.] Mill. cv. ‘Gialla’) juice after a 24-h color regeneration period was investigated. The addition of 0.1% isoascorbic acid prior to heating minimized color alteration as well as betalain degradation to a significant level. A correlation between the total betaxanthin retention and the indicaxanthin/isoindicaxanthin ratio was detected in heated juice samples, thus proving the indicaxanthin/isoindicaxanthin ratio as a valuable indicator of thermally treated cactus pear juices. Notably, the same ratio was instrumental for retrospectively calculating the initial betaxanthin content. Additionally, storage experiments over a period of 6 mo were conducted. Samples kept in the dark exhibited notably better color and pigment retentions as compared to illuminated samples. A significantly stabilizing effect was also observed in samples with isoascorbic acid fortification. While indicaxanthin and betanin were predominantly degraded through hydrolytic cleavage upon both heat exposure and storage, isomerization was only marginal for betanin. In contrast, 2-decarboxy-betanin formation was exclusively found for nonfortified heated samples while decarboxylated indicaxanthin could not be detected.

Markus R. Moßhammer

Papers

Evaluation of different methods for the production of juice concentrates and fruit powders from cactus pear

Cactus Pear Fruits (Opuntia spp.): A Review of Processing Technologies and Current Uses

Development of a process for the production of a betalain-based colouring foodstuff from cactus pear

Colour studies on fruit juice blends from Opuntia and Hylocereus cacti and betalain-containing model solutions derived therefrom

Impact of Thermal Treatment and Storage on Color of Yellow-Orange Cactus Pear (Opuntia ficus-indica[L.] Mill. cv. ‘Gialla’) Juices