Bacterial inactivation mechanism of SC-CD and TEO combinations in watermelon and melon juices

Abstract

Thermal heating methods are well-known and ancient techniques for reducing the microbial load of various foods. They have detrimental effects on the texture, color, flavor, aroma and nutrients of fruit products (Erkmen & Bozoglu, 2016c). Enteric bacteria (Escherichia coli, Salmonella strains and others) are Gram-negative rods, have great importance in public health and can associate with ready-made foods (such as fruits and fruit juice), dairy and meat products and seafood and vegetables (Erkmen & Bozoglu, 2016b). K. pneumoniae has been isolated from different foods, heated tomato juice (at 60 °C for 75 min), high sugar-containing acidic foods, wastewater and intestinal tract. In these senses, the increased consumer demand and awareness for fresh-like and natural food products with high and/or maximum organoleptic quality and extended shelf life, non-thermal food preservation methods have been proposed. Nonthermal pressurized carbon dioxide (CO2) has several advantages in the inactivation of microorganisms in foods, such as low cost, ease of removal from the product after use, generally recognized as safe, non-toxic, inflammable and environmentally friendly (Moussé et al., 2016; Silva et al., 2020). Supercritical CO2 (SC-CD) above its critical point (31 °C and 7.4 MPa) is characterized by a high density (close to liquids), a high diffusivity (close to gases), a low viscosity (as gases) and a very low surface tension. SC-CD were potentially used to inactivate microorganisms and enzymes in various foods such as watermelon, melon, milk, milk products, orange juice, apple juice, peach and carrot juice, apple juice and cheese, seeds, apple juice, peach and fresh-cut carrot, tomato juice and kimchi (Erkmen, 2000, 2012; Liu et al., 2012; Spilimbergo et al., 2013; Sikin et al., 2016; Marszałek et al., 2018; Pei et al., 2018; Wang et al., 2018).