REVIEW BIODEGRADABLE PACKAGING AND EDIBLE COATING FOR FRESH-CUT FRUITS AND VEGETABLES F. GALGANO1*, N. CONDELLI1, F. FAVATI2, V. DI BIANCO1, G. PERRETTI3 and M.C. CARUSO1 1 School of Agricultural, Forestry, Food and Environmental Sciences, University of Basilicata, Viale dell’Ateneo Lucano 10, 85100 Potenza, Italy 2 Department of Biotechnology, University of Verona, Strada Le Grazie 15, 37134 Verona, Italy 3Department of Agriculture, Food and Environmental Sciences, University of Perugia, Via S. Costanzo n.c.n., 06126 Perugia, Italy *Corresponding author: Tel. +39 0971-205570, Fax +39 0971-205503, email: [email protected] ABSTRACT This work focuses on biodegradable packaging and edible coatings applied to fresh-cut fruits and vegetables and their effects on the product quality. Practical applications are mainly limited to the use of biodegradable materials that, however, do not allow full control of the product mois- ture loss. Better results can be achieved by the combined use of biodegradable packagings with edible coatings and recent research has shown that enrichment with silver-montmorillonite nan- oparticles may be a promising technique. However, the actual utilization of these materials is still limited, due to the high costs of the raw materials and the limited production. - Keywords: biodegradable packaging, biopolymers, edible coating, fresh-cut fruits and vegetables, minimally processed foods, nanocomposites - Ital. J. Food Sci., vol. 27 - 2015 1 INTRODUCTION appropriate atmosphere within packages (SMITH et al., 1987). In recent years, the establishment of new Traditionally, food companies use polymeric lifestyles, characterized by a lack of time in do- films (polyethylene PE, polypropylene PP, poly- mestic preparations, has been accompanied by styrene, PS) to package fresh fruits and vegeta- an evolution of the structure of food consump- bles because of their large availability at rela- tion and a destructuring of meals. Therefore, tively low cost and their good mechanical per- the consumption of minimally processed fruits formance, good barrier to oxygen, carbon diox- and vegetables has grown rapidly as a result of ide (SIRACUSA et al., 2008). Nowadays, there is the consumer trend- “rich in cash, poor in time” a growing trend in fresh fruits and vegetables (MARTÍN-DIANA et al., 2007; CONTE et al., 2009). packaging sector to replace the petrochemi- Minimally processed fruits and vegetables cal based packaging films with more environ- were developed in the 1980s to respond to the mentally-friendly biodegradable materials (THA- emerging consumer demand for both conve- RANATHAN, 2003). The extensive use of synthet- nience and high quality aspects (DEL NOBILE et ic packaging films has led to serious ecological al., 2008). These foodstuffs combine fresh-like problems due to their total non- biodegradabili- and healthy characteristics with a minimal time ty. Therefore, biodegradability is not only a func- of preparation before consumption (RAGAERT et tional requirement but also an important envi- al., 2004). In fact, their success is also due to the ronmental attribute. Biologically-based packag- beneficial health effects for the presence of an- ing contains raw materials originated from agri- tioxidants that act as receptors of free radicals; cultural sources, produced from renewable raw in particular, ascorbic acid and β-carotene are materials such as starch and bio-derived mono- the antioxidants present in the greatest quanti- mers (LUCERA et al., 2010). These materials rep- ties in fruits and vegetables (RICO et al., 2007). resent a viable alternative because: The minimal processing operations (“mild - they are obtained from renewable sources; technology”) necessary to produce fresh-cut - they are recyclable and degradable; foods, such as peeling, cutting, washing, treat- - they are an opportunity to reduce costs. ments with sanitizing agents, drying, alter the The applications range from the design of mul- physical integrity of these products, making tilayer barrier coating consisting of biopolymers, them more perishable than the original raw ma- to enrichment of the matrix of traditional plas- terials (CORBO et al., 2006). This is due to res- tics PP and PE with nanocomposite materials of piration, transpiration, enzymatic activity of the natural origin. However, bio-packaging still rep- living tissue after harvest and processing and, resents a niche market because of the cost and at the same time, to proliferation of spoilage and poor overall performance of biodegradable films pathogenic microorganisms (GALGANO et al., when compared to those of traditional plastic 2014; NGUYEN-THE and CARLIN, 1994). The in- materials (DEL NOBILE et al., 2009 a). dustrial process accelerates the degradation of The present work focuses on the different the minimally processed foods and leads to bio- packaging strategies for fresh-cut fruits and chemical changes such as: vegetables. In particular, the potential appli- - increasing of respiration that accelerates the cations of biodegradable materials and edible oxidation processes; coatings have been described, with their effects - degradation of cell membranes and enzy- on the quality of these products. The applica- matic browning; tion of nanotechnology, as a tool to improve the - loss of tissue texture. performance and thermal, barrier and mechani- The knowledge of factors influencing quality cal properties of bio-polymers has also been as- degradation after processing of fruits and vegeta- sessed (AZEREDO, 2009). bles is essential to develop technologies for shelf- life extending and maintaining quality during processing and distribution (CORBO et al., 2006). BIO-BASED MATERIALS In order to reduce the microbiological, chem- FOR FOOD paCKAGING ical and physical spoilage, it is possible to act on processing or, more usually, on packaging The term “Bio-Based Materials” (BBM) is as- that represents a barrier to qualitative decay of signed to packaging materials and to packaging the product (GALGANO et al., 2014). The packag- produced from biological renewable raw mate- ing operation should establish inside the pack- rials (PIERGIOVANNI and MASCHERONI, 2007). aging an optimal atmosphere for the best pres- Polymers derived from renewable resources ervation of the product. Generally, low O2 and (biopolymers) are broadly classified according elevated CO2 atmospheres, associated with low to method of production, as follows: storage temperature, reduce product respira- 1. Polymers directly extracted/removed from tion rate, limiting, in this way, losses in fresh natural materials (mainly plants). Examples weight (WATADA et al., 1996). Therefore, a prop- are polysaccharides, such as starch and cellu- er combination of product characteristics and lose and proteins, like casein and wheat glu- film permeability results in the evolution of an ten, and lipids. 2 Ital. J. Food Sci., vol. 27 - 2015 2. Polymers produced by “classical’’ chemi- in comparison with commercial plastic films. cal synthesis from renewable bio-derived mon- The main polysaccharides that can be includ- omers. A good example is polylactate, a biopol- ed in edible coating formulations are starch yester polymerised from lactic acid monomers. and starch derivates, cellulose derivates, alg- The monomer itself is produced via fermenta- inate, carrageenan, chitosan, pectin, and sev- tion of carbohydrate feedstock. eral gums. Based on the molecular level, pol- 3. Polymers produced by microorganisms ysaccharides vary according to their molecu- or genetically transformed bacteria. The best lar weight, degree of branching, conformation, known bio-polymer types are the polyhydroxyal- electrical charge and hydrophobicity. Variations kanoates, mainly polyhydroxy butyrates and co- in these molecular characteristics will lead to polymers of hydroxy-butyrate (HB) and hydroxy- variations in the ability of different polysaccha- valerate (HV) (PETERSEN et al., 1999). rides to form coatings, as well as to variations The compostability attribute is very impor- in the physicochemical properties and perfor- tant for biopolymer materials, because compost- mance of the coatings formed. For example, ing allows disposal of the packages in the soil, the linear structure of some of these polysac- which is more energy efficient than recycling. charides such as cellulose, amylose (a compo- During biological degradation water, carbon di- nent of starch), and chitosan makes their films oxide and inorganic compounds without toxic tough, flexible, transparent, and resistant to residues are produced. fats and oils (VARGAS et al., 2008). According to the European Bioplastics, biopol- Starch, a storage polysaccharide of cereals ymers made with renewable resources have to and legumes, is most commonly used in the for- be biodegradable and especially compostable, so mulation of edible coatings and films because they can act as fertilizers and soil conditioners. it is inexpensive, abundant, biodegradable, and Whereas plastics based on renewable resources easy to use. Films based on starch have mod- must not necessarily be biodegradable or com- erate gas barrier properties. Their mechani- postable, the bioplastic materials do not neces- cal properties are generally inferior to synthet- sarily have to be based on renewable materials, ic polymer films. When a plasticizer, such as because the biodegradability is directly corre- water, is added starches exhibit thermoplastic lated to the chemical structure of the materials behavior (KROCHTA and MULDER-JOHNSTON,