Journal on Processing and Energy in Agriculture 19 (2015) 3 139 Biblid: 1821-4487 (2015) 19; 3; p 139-142 Original Scientific Paper UDK: 547.458.61 Originalni naučni rad STRUCTURAL CHANGES IN STARCH DURING STARCH BASED EDIBLE FILMS SYNTHESIS STRUKTURNE PROMENE SKROBA TOKOM SINTEZE JESTIVIH FILMOVA Danijela ŠUPUT * , Vera LAZIĆ * , Lato PEZO ** , Aleksandra RADULOVIĆ ** , Senka POPOVIĆ * , Nevena HROMIŠ * , Sandra BULUT * * University of Novi Sad, Faculty of Technology, Bulevara cara Lazara 1, 21000 Novi Sad, Serbia ** University of Belgrade, Institute of General and Physical Chemistry, Studentski Trg 12, Belgrade, Serbia e-mail: suput.danijela@gmail.com ABSTRACT The aim of this study was to investigate starch and starch based edible films with and without oregano essential oil addition in terms of crystallinity by using X-ray diffractometry. Starch crystallinity is related to amylopectin linear chains which may give different X-ray diffraction patterns, described as A, B and C chains. Diffraction pattern of starch based edible film without essential oil addition showed broad diffraction peak in 15-20° 2θ region, indicating destruction of A-type crystal structure due to experimental conditions of casting procedure used in this work. Diffraction peaks of samples with 0.5 %, 1 % and 2 % oregano essential oil, whose shapes are to some extent retained after oregano oil addition, were centered at 20.8°, 20.1° and 21.6° 2θ respectively, while pattern of sample with 2% oregano essential oil showed additional diffraction peaks at 31.1°, 35.1°, 38.3°, 44.5° and 64.9° 2θ. X-ray diffraction patterns showed polyamorphous nature of investigated starch samples with essential oils addition. Key words: starch, starch based edible film, essential oil, structure, X-ray diffraction. REZIME Cilj istraživanja je ispitivanje strukturnih svojstava skroba, jestivog skrobnog filma i jestivog skrobnog filma kome je dodato esencijalno ulje origana u različitoj koncentraciji (0,5%, 1% i 2%). Uprkos razlikama u sastavu, veličini i obliku, opšti opis organizacije granula skroba je opšte prihvaćen: kombinacija dve komponente, amiloze i amilopektina. Poznato je da se pojam kristaliniteta skroba odnosi na linearne lance amilopektina, koji mogu da daju različite difrakcije X-zraka u zavisnosti od izvora skroba. Osnovna organizacija lanaca se opisuje kao tip skroba A, B ili C. Kristalinitet skroba, skrobnih filmova sa i bez dodatog ulja origana je ispitan korišćenjem metode difrakcije X-zraka. Difrakcioni podaci su prikupljeni u ugaonom opsegu 4-70°2θ, sa vremenom zadržavanja 0,5 s po koraku i veličinom koraka od 0,02° 2θ. Difraktogram jestivog filma na bazi skroba bez dodatka ulja pokazao je širok difrakcioni maksimum u 15-20° 2θ regionu, ukazujući na destrukciju A-tipa kristalne strukture zbog eksperimentalnih uslova razlivanja filma. Difrakcioni maksimumi uzoraka jestivih filmova na bazi skroba sa 0,5%, 1% i 2% dodatog esencijalnog ulja origana, donekle su zadržali svoje oblike, a maksimumi su locirani na 20,8°, 20,1° i 21,6° 2θ respektivno, dok uzorak sa 2% dodatog esencijalnog ulja origana pokazuje dodatne difrakcione pikove na 31,1°, 35,1°, 38,3°, 44,5° i 64,9° 2θ. Dobijeni difraktogrami X zraka ukazuju na poliamorfnu prirodu ispitivanih uzoraka jestivih filmova na bazi skroba sa dodatim uljem origana. Ključne reči: skrob, jestivi skrobni filmovi, esncijalno ulje, struktura, X-ray difrakcija. INTRODUCTION Starch based edible films, among other bio-based edible packaging materials (Lazić et al., 2008), have wide application in the food industry due to low cost, eco-friendly status (Lazić et al., 2009), flexibility and transparency (Šuput et al., 2014). Starch mainly consists of two polymers of a-D-glucose units linked by a-1,4 and a-1,6 bonds. These are the nearly linear amylose (AM) and highly branched amylopectin (AP), which make up for 98–99 % of the dry weight of the starch granule (Tester et al., 2004; Chen et al. 2009). Their chains can thus be represented as (C 6 H 12 O 6 ) n , whereby n is variable (in length) depending on the distribution of the different polymers. The ratio of the two starch polymers (in starch granules) as well as their molecular configuration strongly influences the product properties (Blazek and Copeland, 2008). AM is located in the amorphous and semi-crystalline regions, whereas the majority of AP chains are found within the crystalline regions (Jane and Shen, 1993). In addition, starch contains minor constituents (lipids, proteins and minerals) of which the levels vary with the botanical origin. The AM content of normal starches varies between 14 and 29 % (Vandeputte et al., 2003; Gomand et al., 2010). AM is a relatively long, linear a-glucan containing around 99 % (1→4)-α-linkages and differs in size and structure depending on botanical origin (Tester et al., 2004). Some molecules are slightly branched by (1→6)-α-linkages (Buleon et al., 1998). Therefore it can be concluded that the presence of branches does not alter significantly the solution behavior of amylose chains, which remains identical to that of strictly linear chains (Buleon et al., 1998). Amylopectin is a much larger molecule than amylose with heavily branched structure built from about 95 % (1→4)-α- and 5 % (1→6)-α-linkages. There is great additional variation with respect to the unit chain lengths and branching patterns (Tester et al., 2004). Amylopectin unit chains are relatively short compared to amylose molecules with a broad distribution profile. The individual chains can be specifically classified in terms of their lengths (chain lengths, CL) and consequently position within starch granules (Hizukuri, 1986). The basic organization of the chains is described in terms of the A, B and C chains. AP is largely responsible for the