Towards drylands biorefineries: valorisation of forage Opuntia for the production of edible coatings.

Species of the genus Opuntia may be a well-suited feedstock for biorefineries located in drylands, where biomass is scarcer than in humid or temperate regions. This plant has numerous uses in Mexico and Central America, and its mucilage is a specialty material with many promising applications. We extracted the mucilage from a forage species, O. heliabravoana Scheinvar, and mixed it with a thermoplastic starch to produce an edible coating. The coating was applied to blackberries, which were then evaluated in terms of several physicochemical and microbiological variables. During a 10-day evaluation period, the physicochemical variables measured in the coated fruits were not significantly different from those of the control group. However, the microbiological load of the coated fruits was significantly lower than that of the uncoated fruits, which was attributed to a decreased water activity under the edible coating. Multivariate analysis of the physicochemical and microbial variables indicated that the storage time negatively affected the weight and size of the coated and uncoated blackberries. Although some sensory attributes have yet to be optimised, our results support the use of the mucilage of forage Opuntia for the formation of edible coatings, as well as their valorisation through a biorefinery approach.