Antimicrobial effects of chitosans and chitooligosaccharides, upon Staphylococcus aureus and Escherichia coli, in food model systems

• Published in: Food microbiology Vol. 25; no. 7; pp. 922 - 928
• Main Authors: Fernandes, João C., Tavaria, Freni K., Soares, José C., Ramos, Óscar S., João Monteiro, M., Pintado, Manuela E., Xavier Malcata, F.
• Format: Journal Article
• Language: English
• Published: London Elsevier Ltd 01.10.2008; Elsevier
• Subjects: Animals; Anti-Bacterial Agents - adverse effects; Anti-Bacterial Agents - pharmacology; antibacterial properties; apple juice; bacterial contamination; Bactericidal; Beverages - microbiology; Beverages - standards; Biological and medical sciences; chitooligosaccharides; chitosan; Chitosan - adverse effects; Chitosan - pharmacology; Colony Count, Microbial; Consumer Product Safety; Dose-Response Relationship, Drug; Escherichia coli; Escherichia coli - drug effects; Escherichia coli - growth & development; food acceptability; food contamination; Food Contamination - prevention & control; Food industries; Food Microbiology; food pathogens; foods; Fundamental and applied biological sciences. Psychology; Gram-negative; Gram-positive; Humans; inoculum density; Juice; liquids; Malus; Milk; Milk - microbiology; Milk - standards; Milk and cheese industries. Ice creams; model food systems; Molecular Weight; off flavors; oligosaccharides; Oligosaccharides - adverse effects; Oligosaccharides - pharmacology; sensory properties; Staphylococcus aureus; Staphylococcus aureus - drug effects; Staphylococcus aureus - growth & development; Taste - drug effects; Time Factors; Juice; Bactericidal; Gram-positive; Gram-negative; Molecular weight; Milk; Escherichia coli; Oligosaccharide; Dairy product; Antimicrobial agent; Bactericidal effect; Bacteria; Micrococcales; Micrococcaceae; Models; Chitosan; Molecular mass; Staphylococcus aureus; Enterobacteriaceae; Food
• ISSN: 0740-0020; 1095-9998; 1095-9998
• DOI: 10.1016/j.fm.2008.05.003

The objective of this study was to elucidate the controversial relationship between the molecular weight (MW) of chitosans and their antibacterial activity (upon different inoculum levels, at several concentrations). The influence of food components on the activity was also ascertained, as well as acceptance by a sensory panel. All the compounds tested exhibited antibacterial activity against Staphylococcus aureus and Escherichia coli. This activity was shown to be closely dependent on the inoculum level, MW and concentration used. Within 4 h at 10 3 cells/mL, all five compounds, at every concentration (0.5%, 0.25% and 0.1%, w/v), proved to be bactericidal; for higher inocula, 0.1% (w/v) was only bacteriostatic; at 10 7 or 10 5 cells/mL, and independently of the inoculum level, 0.25% (w/v) of any chitooligosaccharide (COS) mixture was sufficient to reduce the E. coli initial population by at least 3 log cycles; COS never exhibited bactericidal action over S. aureus, unlike high and medium MW chitosans—which, at 0.5% (w/v), presented a bactericidal effect even against 10 7 cells/mL. When incorporated in liquid food matrices, medium and high MW chitosans maintained their activity, for both matrices and bacteria, although a slower activity was noticeable in milk; however, COS lost their activity upon both bacteria in milk after 4–8 h. Furthermore, addition of chitosans to apple juice led to several unpleasant off-flavors, such as astringency and after taste—which increased in magnitude with MW.