Ultrasound-assisted extraction of anthocyanins from Andean blackberry and their use as an indicator in sustainable smart biofilms developed with cocoa bean shells as natural fiber-filled PLA composite materials

Abstract

In Colombia, about 34% of the food available in the country is lost or discarded. Recent studies reveal that one of the main reasons why Colombians discard food is because they do not have enough information about the current state of the product. Developing smart packaging with indicator agents can help to reduce food waste by providing consumers with accurate information about food conditions. Anthocyanins (AA) are ideal pH-sensitive indicator pigments for this application. In addition, new packaging should prioritize the use of biodegradable materials such as polylactic acid (PLA) and natural fibers. These fibers can be obtained from agro-industrial waste, such as those generated in cocoa processing, which reach up to 80% of the total production. This study aimed to evaluate the ultrasound-assisted extraction of anthocyanins from Andean blackberry and its use as a natural indicator in a sustainable smart biofilm developed with cocoa beans shell (CBS) fiber-filled PLA composite material. For the ultrasound-assisted extraction of anthocyanins from blackberries, a 3² factorial experimental design was proposed to assess the effect of biomass: solvent ratio and extraction time on the extraction yield (%) and Monomeric Anthocyanin Content (MAC). The assays were conducted using a power of 110 W and a frequency of 40 kHz. The solvent employed was ethanol (80% v/v) acidified with 0.1% (v/v) hydrochloric acid. The results showed a maximum anthocyanins extraction of 161.66 mg/L, achieved with an extraction time of 15 min and a biomass-solvent ratio of 1:10 g/mL. The successful integration of anthocyanins into the biofilm was demonstrated by FTIR. However, it was found that they affect the thermal, mechanical, and physical properties of the biofilm. In PLA_AA biofilms, the total color difference (ΔE) increased with the pH after pH8, while in PLA_CBS_AA, there were higher ΔE values observed across the tested pH values, with the highest value presented in the intermediate range (pH 7). There was not a clear pattern of color change between pH 4 and pH 6. The potential use of these films in smart packaging applications was proved by significant color changes from pink (pH 2) to brown (pH 12). Overall, this study highlights the potential of utilizing anthocyanins as a natural indicator in sustainable smart packaging.