Development of biodegradable active packaging material from chitosan: synthesis, optimisation of properties, characterisation and application

Predmet doktorske disertacije je razvoj aktivnog jestivog omotača na bazi hitozana sa dodatkom etarskih ulja začinskog bilja i pčelinjeg voska, kao i njegova aplikacija u cilju produženja održivosti suve fermentisane Petrovačke kobasice. U cilju realizacije programa teze, formirane su tri osnovne grupe filmova: hitozan-etarsko ulje origana, hitozan-etarsko ulje kima i hitozan-etarsko ulje kima-pčelinji vosak. Paralelno sa pripremom filmova, proizvedeni su i odgovarajući kolagen-hitozan laminirani omotači. U pripremi filmova i omotača su primenjena dva vlažna postupka. Filmovi su dobijeni razlivanjem, a laminirani omotači premazivanjem filmogene emulzije preko kolagenog omotača. Tokom razvijanja, ispitivan je uticaj različitih parametara na svojstva dobijenih filmova: viskozitet i koncentracija hitozana, dodatak polietilenoksida kao kopolimera u film, dodatak različite koncentracije etarskog ulja, uslovi mešanja i temperature, kao i dodatak različite koncentracije pčelinjeg voska. Dobijeni filmovi i omotači su okarakterisani ispitivanjem osobina značajnih za primenu materijala, a to su fizičko-mehanička (debljina, zatezna jačina i izduženje pri kidanju), strukturna (ATR-FTIR spektrometrija i elektron skenirajuća mikroskopija), fizičko-hemijska (sadržaj vlage, bubrenje, rastvaranje), barijerna (propustljivost gasova i brzina propustljivosti vodene pare) svojstva i biološka aktivnost (antioksidatino i antimikrobno delovanje). Na osnovu detaljne karakterizacije, odabrani su filmovi i omotači optimalnih svojstava za primenu u zaštiti Petrovačke kobasice tokom skladištenja. Ispitano je dejstvo premaza na očuvanje kobasice sa i bez dodate komercijalne i autohtone starter kulture. Efekat primene premaza izučavan je ispitivanjima parametara kvaliteta Petrovačke kobasice i to, praćenjem promene sadržaja vlage, pH vrednosti, boje, oksidacije lipida, kao i senzorne ocene mirisa i ukusa ove kobasice tokom skladištenja. Na osnovu prikazanih rezultata, može se zaključiti da je sintetisan aktivan jestivi premaz na bazi hitozana optimizovanih barijernih, fizičko-hemijskih, antioksidativnih i antimikrobnih svojstava. Sintetisani premaz ima manju brzinu propustljivosti vodene pare, uz očuvanu nisku propustljivost za gasove, smanjenu osetljivost na delovanje vlage i izraženiju antimikrobnu i antioksidativnu aktivnost. Upkos optimizovanim barijernim svojstvima za vodenu paru, hitozanski premaz sa dodatkom etarskih ulja i/ili pčelinjeg voska nije imao efekta u očuvanju sadržaja vlage suve fermentisane kobasice tokom skladištenja. Ispitivani premazi su doprineli očuvanju boje preseka kobasice, ali ovaj efekat nije bio potpuno izražen kod svih tipova kobasice i svih premaza. Sva tri parametra za praćenje oksidativnih promena u kobasici ukazuju na to da je nanošenjem hitozanskog premaza sa etarskim uljem origana ili kima i pčelinjim voskom, kobasica efikasno zaštićena od nepoželjnih oksidativnih promena. Između eksperimenata se može povući paralela, da hitozanski premaz pokazuje zaštitni efekat prema senzornom profilu mirisa i ukusa, do blizu 5 meseci skladištenja. Na ovom nivou razvoja premaza, on se može preporučiti kao pomoćan ambalažni materijal.The subject of the doctoral dissertation is development of active edible coating based on chitosan with added herb essential oils and beeswax, as well as its application for dry fermented sausage shelf life extension. In order to realize the program of investigation, three basic groups of films were produced: chitosan-essential oil of oregano, chitosan-essential oil of caraway and chitosan-essential oil of caraway-beeswax. Simultaneously with the production of films, collagen-chitosan laminated casings were produced. In the production of films and laminated casings, two wet methods were applied. Films were produced by casting method, while laminated casings were produced by coating collagen casing with filmogenic emulsion. During production, the influence of different parameters on properties of produced films and casings was investigated: viscosity and concentration of chitosan, addition of poly (ethylene oxide) as copolymer in the films, addition of different concentration of essential oils, mixing and temperature conditions, as well as addition of different concentration of beeswax. Produced films and laminated casings were characterized by the investigation of properties that are important for material application, namely physical-mechanical (thickness, tensile strength and elongation at break), structural (ATR-FTIR spectrometry and scanning electron microscopy), physical-chemical (water content, swelling, solubility), barrier (gas permeability and water vapor transmission rate) properties and biological activity (antioxidative and antimicrobial activity). Based on detail characterization, films and casings with optimal properties were selected for application on Petrovac sausage with and without the addition af commercial or indigenous starter culture for preservation during storage. The effect of coating application was analyzed based on the quality parameters of Petrovac sausage, namely: water content, pH value, color, lipid oxidation and sensory profile of taste and odor of the sausage during storage. Based on presented results, it can be concluded that active edible coating based on chitosan was synthesized, with optimized barrier, physical-chemical, antioxidant and antibacterial properties. Synthesized coating has lower water transmission rate with preserved low gas permeability, lowered sensibility to humidity and more pronounced antimicrobial and antioxidant activity. Despite optimized water vapor barrier properties, chitosan coating with addition of essential oils and/or beeswax did not show the effect in preserving the water content in the sausage during storage. Investigated coatings contributed to the preservation of core color of the sausage, but this effect was not fully expressed in all types of sausages and coatings. All three parameters for investigation of oxidative changes in the sausage showed that chitosan coating with essential oils of oregano and caraway and beeswax efficiently preserved sausage from unwanted oxidative changes. Mutual conclusion from the experiments is that chitosan coating shows preservative effect on the sensory profile of taste and odor till approximately 5 months of storage. On this level of coating development, it can be recommended as auxiliary packaging material