Writing in the journal Food Chemistry, Calatayud et al. say that the packaging film, made from ethylene–vinyl alcohol copolymer (EVOH) containing flavonoid-rich cocoa, could have wide spread appeal across the food industry.
Calatayud and her team developed the film and tested it in an infant formula package to see how it reacted to various food borne diseases such as listeria.
Active compounds inhibit pathogen growth
“This paper shows that the films that have been developed are able to release sufficient amounts of active compounds, mainly catechins from cocoa extract, to inhibit completely the growth of all the microorganisms tested, with no significant differences between Gram-positive and Gram-negative bacteria” said the researchers.
Gram-positive and Gram-negative bacteria have different cell structures. The negative variety includes bacteria such as E. coli and salmonella, while the positive kind includes streptococcus and staphylococcus bacteria.
Infant milk application
The cocoa extract-based films were particularly effective at inhibiting the growth of L. monocytogenes (a bacteria that causes meningitis) in infant milk.
“The films developed in this study could be applied as a coating on a packaging applied to milk. The release of active agents would produce greater protection against microbial contamination and could even extend the shelf life of this product.
“The films would also have the added value of producing an antioxidant effect.”
High flavanol extracts
To obtain cocoa extracts for the films, the researchers used a patented process that preserves most of the original flavanol content. The powder produced had eight times more epicatechin and procyanidin content than regular cocoa powder.
A few previous studies have looked at the possibilities of cocoa as an antimicrobial agent for the food industry, but no cocoa-based films have not been incorporated into any active packaging to date.
Thermal treatments during processing usually stamp out most pathogens but give no guarantee and can affect the quality of the product.
Food Chemistry139 (2013) 51–58
‘Active films based on cocoa extract with antioxidant, antimicrobial and biological applications’
Authors: Marta Calatayud, Carolina López-de-Dicastillo, Gracia López-Carballo, Dinoraz Vélez, Pilar Hernández Muñoz, Rafael Gavara