Continuous Flow UV-C Irradiation Effects on the Physicochemical Properties of Aloe vera Gel and Pitaya (Stenocereus spp.) Blend

Physical, Chemical and Microbiological Properties during Storage of Red Prickly Pear Juice Processed by a Continuous Flow UV-C System

The effects of pH (3.6 and 7.0) and irradiation UV-C dose irradiation (0, 9.81, 15.13, and 31.87 mJ/cm2) on the physicochemical properties and natural microbiota of red prickly pear juice were evaluated during processing and storage. Thermal treatments were used as the control applying high temperatures for a short time (HTST 80 °C/30 s) or ultra-high temperature (UHT 130 °C/3 s). UV-C treatments applied to juices with both pHs inactivated coliforms and mesophiles with the same efficacy as thermal treatments. Yeasts and molds were inactivated at a dose of >15.13 mJ/cm2 at both pHs. The UV-C doses showed no differences in betalains, polyphenols, or antioxidant activity. However, a decrease in these compounds was observed during storage. The lowest reductions in betacyanins (11.1–16.7%) and betaxanthins (2.38–10.22%) were obtained by UV-C treatment at pH 3.6. Thermal treatments (HTST and UHT) caused a reduction greater than UV-C irradiation in betacyanins, betaxanthins, polyphenols, and antioxidant activity after treatment. However, after storage at pH 3.6, the contents of these compounds reached those of the UV-C treatments, except for polyphenols. In specific pigments, betanin retention was highest at pH 3.6 (62.26–87.24%), and its retention decreases with UV-C dose increase and storage. The indicaxanthin retentions were higher (75.85–92.27%) than those of betanin, and the reduction was mainly due to storage. The physical properties (pH, acidity, and °Brix) were not affected by treatments, except for the color. The results suggest that a dose of 15.13 mJ/cm2 of a continuous UV-C system is a non-thermal alternative for the processing of red prickly pear juice at pH 3.6, preserving its properties.

Betalain plant sources, biosynthesis, extraction, stability enhancement methods, bioactivity, and applications

Betalains are plant pigments with functional properties used mainly as food dyes. However, they have been shown to be unstable to different environmental factors. This paper provides a review of (1) Betalain plant sources within several plant families such as Amaranthaceae, Basellaceae, Cactaceae, Portulacaceae, and Nyctaginaceae, (2) The biosynthesis pathway of betalains for both betacyanins and betaxanthins, (3) Betalain extraction process, including non-conventional technologies like microwave-assisted, ultrasound-assisted, and pulsed electrical field extraction, (4) Factors affecting their stability, mainly temperature, water activity, light incidence, as well as oxygen concentration, metals, and the presence of antioxidants, as well as activation energy as a mean to assess stability, and novel food-processing technologies able to prevent betalain degradation, (5) Methods to increase shelf life, mainly encapsulation by spray drying, freeze-drying, double emulsions, ionic gelation, nanoliposomes, hydrogels, co-crystallization, and unexplored methods such as complex coacervation and electrospraying, (6) Biological properties of betalains such as their antioxidant, hepatoprotective, antitumoral, and anti-inflammatory activities, among others, and (7) Applications in foods and other products such as cosmetics, textiles and solar cells, among others. Additionally, study perspectives for further research are provided for each section.