טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentNin-Nun Ofra
SubjectThe Use of Peptides in Antimicrobial Films for Packaging of
Pastrami
DepartmentDepartment of Biotechnology and Food Engineering
Supervisors Professor Emeritus Joseph Miltz
Professor Amram Mor
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

The goal of the study was to examine the possibility to incorporate antimicrobial peptides into food packages for preservation.Pastrami (a rich source of nutrients which allows microbial growth) was chosen as the food product.A laminate composed of Polyethylene (PE) and Polyethylene Terephthalate (PET), of low permeability to gases and water vapor was chosen as the packaging substrate.The microbial strains that contaminate pastrami were identified. These are primarily Pseudomonas, and E.coli.Three antimicrobial active peptides derivatives of the Dermaseptin family where chosen for the study:K4K20S4 - a derivative enriched with lysine.K4S4(1-15) - a shorten derivative which was trimmed.C7-K4S4(3-15) - a hydrophobic shorten derivative. Each derivative was tested for inhibiting microbial growth. The tests were taken under laboratory conditions (Temp=37OC, pH=7, no salt added to the substrate), and under different sets of conditions, in order to examine any effect on their activity.In the first set of experiments, K4K20S4 showed the fastest killing activity against pseudomonas and E.coli.Changes in conditions (salt, acidity, temperature), simulated stress conditions in the environment of pastrami.K4K20S4 showed an advantage in the killing activity of the microorganisms at all sets of conditions tested afterwards.However - when testing the derivatives effectiveness on pastrami, K4S4(1-15) showed an advantage over the other two derivatives.K4S4(1-15) was incorporated in the packaging laminate by two methods:1. External coating of the antimicrobial (AM) agent on top of a starch gel placed on the PE layer of the polymeric substrate.2. Mixing the antimicrobial peptide into the starch gel and then applying it to the substrate. After creating the combined structure, its AM  activity was evaluated.The starch gel bridged the gap between the hydrophobic PE layer and the aqueous peptides solution: In the first method, the derivatives were very effective in the pastrami shelf life extension (by several weeks), in spite of the challenging conditions.In the second method, the peptides were less mobile, and could not reach the microbial contaminates.The process of coating antimicrobial peptides on plastic packaging materials can extend the shelf life of food products. It enables reducing preservatives into the bulk of foods. The topic needs further studies in order to optimize the process, and to find the most effective way for incorporating the peptides into the package. There is also a need to find ways for converting the process into a continuous one in order to be economical for industrial production.