0960–3085/02/$23.50+0.00 # Institution of Chemical Engineers www.catchword.com =titles=09603085.htm Trans IChemE, Vol 80, Part C, September 2002 CHARACTERIZATION OF STARCH BASED EDIBLE COATINGS C. PAGELLA, G. SPIGNO and D. M. DE FAVERI Institute of Oenology and Food Engineering, Catholic University of Sacro Cuore, Piacenza, Italy W hile market globalization and increasing use of minimally processed foods require increased product shelf life, environmental care constraints induce us to search for natural materials to be used in effective packaging systems. Both these issues can be addressed by using edible coatings based on naturally occurring polymers. The characteristics of basic materials need to be modied in formulated coatings to obtain satisfactory results. As edible coatings must act as a barrier, the correct measurement of transport properties is extremely important in product development and in assessing effectiveness. In the present work, different starch samples were tested to obtain edible lms or coatings. After optimizing concentration, composition, dispersion and gelatinization time and tempera- ture, a high amylose starch was selected for preparation of the lms. Films obtained by casting were characterized for water and oxygen permeability developing suitable and simple testing methods, nding a water vapour transfer rate of about 32 g m 2 h ¡1 and an oxygen transfer rate of 5.6 cm 3 O 2 m 2 h ¡1 . They were also tested for protection from UV radiation by adding food- approved iron oxides. Keywords: edible lms; starch-based lms; barrier properties; oxygen permeability; water vapour permeability. INTRODUCTION An edible packaging is dened as a thin layer of edible material formed on a food as a coating or placed (pre-formed) on or between food components. Its purpose is to inhibit mass transfer of moisture, oxygen, carbon dioxide, aromas and lipids; it can be used to encapsulate aroma compounds, anti- oxidants,antimicrobial agents, pigments, ions that stop brown- ing reactions or nutritional substances such as vitamins 1,2 . Furthermore, edible packagings contribute to the protec- tion of the environment because they consist of natural and biodegradable substances and so are non-pollutant products. Since edible lms are both a packaging and a food compo- nent, they have to fulll certain requirements, such as good sensory qualities, high barrier and mechanical efciencies, enough biochemical, physical–chemical and microbial stabi- lity, to be free of toxic substances and safe for health, of simple technology and have a low raw material and process cost 3 . Sometimes, stand-alone edible lms with good mechan- ical properties can replace synthetic packaging lms. Many literature works have investigated physical and mechanical properties of edible lms 4–12 . Starches can be used to form edible or biodegradable lms and to date high amylose starch and hydroxypropy- lated high amylose starch have been used to form self- supporting lms by casting from aqueous solution 4,13–15 . The purpose of the present research was to investigate different starch raw materials in order to select those more suitable for lm preparation and then to characterize the lm for its principal transport properties (e.g. oxygen and water vapour permeability, water resistance and protection from UV radiation). METHODS AND MATERIALS Materials The following starch types were tested: S1: maize starch standard; S2: waxy maize starch; S3: high amylose maize starch (approximately 70% amylose); S4: maize starch modied by ottenyl succinate of starch; S5: pre-gelatinized maize starch with long spinning; S6: pre-gelatinized maize starch with short spinning. As a comparison, lms were also formed from Bacto- Agar (Difco Laboratories) and Sodium Alginate (Carlo Erba Codex). Samples 1–6 were kindly donated by Roquette S.p.A. Further substances were tested as adjunctive ingredients: (a) Glycerin RPE-ALS Carlo Erba; (b) Sorbitol (Roquette Italia S.p.A); (c) Fe 2 O 3 ¢H 2 O (Kingland Chemical Industrial Company); (d) Wax of operculum (Azienda Api Cremona). 193