Presence of nisin in edible films formulated with tapioca
starch and glycerol reduced L. innocua growth, producing
count decrease and acting as a barrier to contamination
after processing.
The study of nisin performance through the agar diffusion
technique was not satisfactory due to the competence
between rate of nisin diffusion, diameter increase due to
swelling and microbial growth. However, studied bacteria
showed a decreased population under the film with nisin
which also produced clear inhibitory zones.
The initial release of nisin to the liquid medium produced
an important inhibition of L. innocua, specially whenliquid had a pH 5.5. This inhibition increased with nisin
content of the films. Although the nisin released from films
suffered loss of activity, the gradual delivery of nisin still
contained in films controlled growth of L. innocua, helping
to reduce contamination along storage better than direct
addition.
It can be concluded that antimicrobial activity of the
films starch-based and containing nisin describe this hurdle
as adequate to act as a barrier to further product contamination.
Gradual release can also help to preclude microbial
proliferation better than nisin directly present in the
media. Additional studies must be performed to determine
if starch modification or additional changes in composition
(i.e. mixture of starch and lipids) might modify antimicrobial
activity and release producing changes in the possibilities
brought about by this hurdle.