The objective of this study was to evaluate changes in color, betalain content, browning index, viscosity, physical stability, microbiological growth, antioxidant content and antioxidant activity of purple cactus pear juice during storage after thermoultrasonication at 80% amplitude level for 15 and 25 min in comparison with pasteurized juice. Thermoultrasound treatment for 25 min increased color stability and viscosity compared to treatment for 15 min (6.83 and 6.72 MPa, respectively), but this last parameter was significantly lower (p<0.05) compared to the control and pasteurized juices (22.47 and 26.32 MPa, respectively). Experimental treatment reduced significantly (p<0.05) sediment solids in juices. Total plate counts decreased from the first day of storage exhibiting values of 1.38 and 1.43 logCFU/mL, for 15 and 25 min treatment, respectively. Compared to the control, both treatments reduced enterobacteria counts (1.54 logCFU/mL), and compared to pasteurized juice decreased pectinmethylesterase activity (3.76 and 3.82 UPE/mL), maintained high values of ascorbic acid (252.05 and 257.18 mg AA/L) and antioxidant activity (by ABTS: 124.8 and 115.6 mg VCEAC/100 mL; and DPPH: 3114.2 and 2757.1 μmol TE/L). During storage thermoultrasonicated juices had a minimum increase in pectinmethylesterase activity (from day 14), and exhibited similar total plate counts to pasteurized juice. An increase of phenolic content was observed after 14 days of storage, particularly for treatment at 80%, 25 min, and an increase in antioxidant activity (ABTS, DPPH) by the end of storage.

Commercialization of cactus pears based on their antioxidant properties can generate competitive advantages, and these can turn into business opportunities and the development of new products and a high-value ingredient for the food industry. This work evaluated the antioxidant activities (1,1-diphenyl-2-picrylhydrazyl radical-scavenging, protection against oxidation of a β-carotene-linoleic acid emulsion, and iron (II) chelation), the content of total phenolic compounds, ascorbic acid, betacyanin, betaxanthin and the stability of betacyanin pigments in presence of Cu (II)-dependent hydroxyl radicals (OH•), in 18 cultivars of purple, red, yellow and white cactus pear from six Mexican states. Our results indicated that the antiradical activities from yellow and white cactus pear cultivars were not significantly different (p < 0.05) and were lower than the average antiradical activities in red and purple cultivars. The red cactus pear from the state of Zacatecas showed the highest antioxidant activity. The free radical scavenging activity for red cactus pears was significantly correlated (p < 0.05) to the concentration of total phenolic compounds (R² = 0.90) and ascorbic acid (R² = 0.86). All 18 cultivars of cactus pears studied showed significant chelating activity of ferrous ions. The red and purple cactus pears showed a great stability when exposed to OH•.

Seed oils from two Mexican varieties of cactus pear (green: Opuntia albicarpa and red: Opuntia ficus indica) were extracted with different solvents (hexane, ethanol, and ethyl acetate) to evaluate their antioxidant activity. The seed oil with higher antioxidant activity was selected to evaluate antimicrobial activity. The fatty acid profile was analyzed by gas chromatography-mass spectrometry (GC-MS). Oil from green cactus pear seeds obtained with ethanol and ethyl acetate exhibited higher antioxidant activity (p<0.05) of 323 and 316 μmol TE/20 mg (p < 0.05), respectively, compared to red cactus pear seed oil (≈274 and 247 μmol TE/20 mg with ethyl acetate and ethanol, resp.). The oil obtained with ethanol and higher antioxidant activity was used to determine the antimicrobial activity. Both cactus pear oils produced a microbial inhibition zone in most of the microorganisms evaluated, particularly Saccharomyces cerevisiae which had similar diameter (38–40 mm). The oil fatty acids profiles of both varieties were similar and exhibited a high content of linoleic acid, while two fatty acids (linolenic and behenic) found in red cactus pear were not observed in the green variety.