Autor(es):
Fernandes, João C. 
; Tavaria, Freni K. ; Soares, José C. ; Ramos, Óscar S. ; Monteiro, M. João ; Pintado, Manuela E. ; Malcata, F. Xavier
Data: 2008
Identificador Persistente: http://hdl.handle.net/10400.14/2726
Origem: Veritati - Repositório Institucional da Universidade Católica Portuguesa
Assunto(s): Bactericidal; Molecular weight; Juice; Milk; Gram-positive; Gram-negative
Descrição
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 10³ 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 107 or 105 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 107 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.
