Antibacterial activity of essential oil encapsulated sodium iota-carrageenan fibers
Spoilage microorganisms cause food waste and loss of quality. While the foodborne pathogen outbreaks lead to thousands of hospitalizations and deaths. Essential oils (EOs), plant extracts, possess the required antimicrobial activities and thus their usage stands out as a feasible approach for controlling the undesirable bacterial growth in food systems. However, EOs are highly volatile and lose their activity upon exposure to environmental conditions. In this regard, their encapsulation in Generally Recognized As Safe (GRAS) matrices such as food grade polysaccharides especially iota-carrageenan could be one of the viable alternatives. Iota-carrageenan, sulfated polysaccharide from marine algae, is being used in food, pharmaceutical and medical application as a gelling and thickening agent. Ordered networks composed of water pockets of the dimensions of EOs could be created by stretching the oriented fibers of iota-carrageenan. These water pockets readily encapsulate the EOs, protect from external stresses, e.g. heat, light, moisture, and release in a controlled manner. Herein, two EOs, carvacrol and eugenol mixed in ethanol and Tween 80 were encapsulated in sodium salt form of iota-carrageenan fibers. The antimicrobial activity was tested against Listeria innocua F4248, Listeria monocytogenes F4244, Salmonella Enteritidis ENT 1344, Salmonella enterica serovar Heidelberg 513, Escherichia coli O157: H7 ATCC 43295, and Staphylococcus aureus ATCC 25923 using the disc diffusion and macro brothdilution assay. Results reveal that the complexes dissolve in the deionized water and EO release in about 40 mins. The complexing, indeed, have inhibitory effect on the growth of the microorganisms, especially in significantly reducing the proliferation of L. monocytogenes and L. innocua . Overall, the intrinsic functionality of essential oils could be preserved by encapsulating them in the ordered polysaccharide matrices for inhibiting the growth of spoilage microorganisms in food systems.^
Srinivas Janaswamy, Purdue University, Arun K. Bhunia, Purdue University.