Interactions of Opuntia ficus-indica with Dactylopius coccus and D. opuntiae (Hemiptera: Dactylopiidae) through the Study of Their Volatile Compounds.

Opuntia ficus-indica has always interacted with many phytophagous insects; two of them are Dactylopius coccus and D. opuntiae. Fine cochineal (D. coccus) is produced to extract carminic acid, and D. opuntiae, or wild cochineal, is an invasive pest of O. ficus-indica in more than 20 countries around the world. Despite the economic and environmental relevance of this cactus, D. opuntiae, and D. coccus, there are few studies that have explored volatile organic compounds (VOCs) derived from the plant-insect interaction. The aim of this work was to determine the VOCs produced by D. coccus and D. opuntiae and to identify different VOCs in cladodes infested by each Dactylopius species. The VOCs (essential oils) were obtained by hydrodistillation and identified by GC-MS. A total of 66 VOCs from both Dactylopius species were identified, and 125 from the Esmeralda and Rojo Pelón cultivars infested by D. coccus and D. opuntiae, respectively, were determined. Differential VOC production due to infestation by each Dactylopius species was also found. Some changes in methyl salicylate, terpenes such as linalool, or the alcohol p-vinylguaiacol were related to Dactylopius feeding on the cladodes of their respective cultivars. Changes in these VOCs and their probable role in plant defense mechanisms should receive more attention because this knowledge could improve D. coccus rearing or its inclusion in breeding programs for D. opuntiae control in regions where it is a key pest of O. ficus-indica.

Dactylopius opuntiae [Cockerell] Could Be a Source of Antioxidants for the Preservation of Beef Patties.

Dactylopius opuntiae is an insect pest that contains at least carminic acid, which has antioxidant properties. Since there is a relationship between the antioxidant ability and preservative action of compounds applied to meat products, the purpose of this study was to evaluate the antioxidant activity and usefulness of a D. opuntiae extract for beef patty preservation. The insects were bred and processed to obtain a liquid extract. For the extract, its carminic acid content, antioxidant activity against two free radicals, and actions on food quality parameters were determined. The D. opuntiae dry powder contained 2.91% w/w carminic acid, while the liquid extract exhibited an IC50 value of 3437.8 ± 67.8 and 19633.0 ± 674.5 µg/mL against the DPPH and ABTS radicals. Nevertheless, these antioxidant actions were lower than those found in a D. coccus extract. The D. opuntiae extract improved in a short time the redness and yellowness, eliminated the unfavorable effect of their vehicle on the MetMb level, and greatly reduced the TBARS formation. For the first time, an extract of D. opuntiae was applied to beef patties, and its beneficial antioxidant action on meat acceptance parameters was confirmed, which has potential commercial applications.