Nonthermal inactivation and sublethal injury of Lactobacillus plantarum in apple cider by a pilot plant scale continuous supercritical carbon dioxide system

• Published in: Food microbiology 2011-05, Vol.28 (3), p.377-383
• Main Authors: Yuk, Hyun-Gyun, Geveke, David J.
• Format: Article
• Language: English
• Subjects: Apple cider; Beverages - microbiology; Biological and medical sciences; Carbon Dioxide - pharmacology; Colony Count, Microbial; Consumer Product Safety; Dose-Response Relationship, Drug; Food Contamination - analysis; Food Contamination - prevention & control; Food engineering; Food industries; Food Microbiology; Food Preservation - methods; Fundamental and applied biological sciences. Psychology; General aspects; Humans; Lactobacillus plantarum; Lactobacillus plantarum - drug effects; Lactobacillus plantarum - growth & development; Malus; Malus - microbiology; Nonthermal pasteurization; Sublethal injury; Supercritical carbon dioxide; Temperature
• ISSN: 0740-0020; 1095-9998
• DOI: 10.1016/j.fm.2010.09.010

The objective of this study was to evaluate the efficacy of supercritical carbon dioxide (SCCO 2) for inactivating Lactobacillus plantarum in apple cider using a continuous system with a gas-liquid metal contactor. Pasteurized apple cider without preservatives was inoculated with L. plantarum and processed using a SCCO 2 system at a CO 2 concentration range of 0–12% (g CO 2/100 g product), outlet temperatures of 34, 38, and 42 °C, a system pressure of 7.6 MPa, and a flow rate of 1 L/min. Processing with SCCO 2 significantly ( P < 0.05) enhanced inactivation of L. plantarum in apple cider, resulting in a 5 log reduction with 8% CO 2 at 42 °C. The response surface model indicated that both CO 2 concentration and temperature contributed to the microbial inactivation. The extent of sublethal injury in surviving cells in processed apple cider increased as CO 2 concentration and processing temperature increased, however the percent injury dramatically decreased during SCCO 2 processing at 42 °C. Structural damage in cell membranes after SCCO 2 processing was observed by SEM. Refrigeration (4 °C) after SCCO 2 processing effectively inhibited the re-growth of surviving L. plantarum during storage for 28 days. Thus this study suggests that SCCO 2 processing is effective in eliminating L. plantarum and could be applicable for nonthermal pasteurization of apple cider. ►SCCO 2 was effective in killing L. plantarum in apple cider at low temperature. ►Sublethal injury increased as CO 2 concentration and processing temperature increased. ►4 °C inhibited the re-growth of surviving L. plantarum during storage for 28 days.