Inhibition of Shiga Toxin 2 (Stx2) in Apple Juices and its Resistance to Pasteurization

• Published in: Journal of food science 2010-06, Vol.75 (5), p.M296-M301
• Main Authors: Rasooly, Reuven, Do, Paula M, Levin, Carol E, Friedman, Mendel
• Format: Article
• Language: English
• Subjects: apple juice; Apples; Beverages - microbiology; Biological and medical sciences; biological resistance; Colony Count, Microbial; E coli; E. coli O157:H7; Escherichia coli; Escherichia coli - immunology; Escherichia coli - metabolism; food contamination; Food engineering; Food industries; Food Microbiology; Food Preservation - methods; food processing quality; Food science; Fruit and vegetable industries; Fruit juices; Fundamental and applied biological sciences. Psychology; General aspects; High temperature; Hot Temperature; inhibitors; Malus; Malus - microbiology; model food systems; Molecular Weight; MTT assay; Oxidoreductases - metabolism; Pasteurization; Shiga Stx2 toxin inactivation; Shiga Toxin 2 - analysis; Shiga Toxin 2 - antagonists & inhibitors; Shiga Toxin 2 - chemistry; Shiga Toxin 2 - immunology; Shiga-like toxin 2; Shigellosis; Toxins
• ISSN: 0022-1147; 1750-3841
• DOI: 10.1111/j.1750-3841.2010.01615.x

In the present study, we evaluated Shiga toxin (Stx2) activity in apple juices by measuring a decrease in dehydrogenase activity of Vero cells with the microculture tetrazolium (MTT) assay. Freshly prepared juice from Red Delicious apples and Golden Delicious apples inhibited the biological activity of the bacterial toxin Stx2 produced by E. coli O157:H7 strains. Studies with immunomagnetic beads bearing specific antibodies against the toxin revealed that Stx2 activity was restored when removed from the apple juice. SDS gel electrophoresis revealed no difference (P < 0.05) in the densities or molecular weights between Stx2 in either PBS or apple juices. These results suggest that Stx2 may be reversibly bound to small molecular weight constituents in the juice. The Stx2 toxin was not inactivated on exposure to heat programs (63 °C for 30 min, 72 °C for 15 s, 89 °C for 1 s) commonly used to pasteurize apple juice, but lost all activity when exposed to 100 °C for 5 min. The results suggest that pasteurization of apple juice used to inactivate E. coli O157:H7 has no effect on Stx2, and that food-compatible and safe antitoxin compounds can be used to inhibit the biological activity of the Shiga toxin. This study explores the possibility of using naturally occurring antioxidative substances, in this case high phenolic apples juices, to inactivate Shiga toxin (Stx2) produced by E. coli O157:H7 in contaminated foods.