Gluten free edible films, coatings and toppings

Abstract

The gluten intolerances have determined diet changes based on the elimination of ingredients that contain prolamins and glutenin from wheat, rye and barley being replaced, in part, for alternative grains and tubers that do not induce the disease, for instance, rice, corn, sorghum, and millet (Lebwohl and Green 2021). This has led to an important challenge for the food industry due to the need of developing formulation strategies, generally known as “gluten free” (GF) ones, that include the use of suitable additives linked to this dietary modification, while helping to produce safety and organoleptically adequate food products (Zoumpopoulou and Tsakalidou 2019). According to the Food and Drug Administration (U.S.A.), the GF food is defined as the food that does not contain gluten, or its presence should be lower than 20 ppm (McCabe 2010). Bread and sweet baked goods (cakes, biscuits, doughnuts, etc.) are an essential constituent of the human daily diet, representing the most important basic food worldwide (Nils-Gerrit Wunsch 2020; Xu et al. 2020). There is a wide assortment of such products and, a possible classification is the one proposed by Smith et al. (2004) who grouped them as follow: unsweetened (bread, rolls, buns, crumpets, muffins, and bagels), sweet (pancakes, doughnuts, waffles, and cookies) and filled (fruit and meat pies, sausage rolls, pastries, sandwiches, cream cakes, pizza, and quiche) goods. In their formulation, these products include complex carbohydrates (mainly wheat flour), proteins, lipids, vitamins, and minerals (Soukoulis et al. 2014). Another classification proposed is based on the water activity (aw), one of the most important product properties affecting the physical and microbial deterioration of bakery products. Smith and Simpson (1995) classified bakery products as follow: (a) low moisture bakery products (cookies and crackers, aw < 0.6) in which microbiological spoilage is not a problem, (b) intermediate moisture products (chocolate coated, doughnuts, Danish pastries, cream-filled cake, soft cookies, aw 0.6–0.85) where osmophilic yeasts and moulds are the predominant spoilage microorganisms, and (c) high moisture products (bread, pita bread, fruit pies, carrot cake, cheesecake, pizza crust, pizza, aw > 0.85 and generally 0.94–0.99), where almost all bacteria, yeasts, and moulds are capable of growth (Smith et al. 2004). When no preservative additives are added, bread and bakery products are characterized by their limited shelf-life reaching a maximum of 3–5 days at room temperature. After this time, physical, chemical and microbiological changes are produced, resulting in the loss of freshness, texture, taste and microbial spoilage (growth of bacteria, yeast and mould) causing consumer’s rejection (Melini and Melini 2018). Those alterations can cause not only economic losses, but also threaten human health. Therefore, to extend bread and bakery products shelf-life and to assure their quality and safety properties, preservation techniques such as the use of preservatives or adequate packaging materials and the application of innovative processing technologies are proposed (Mitelut et al. 2021; Qian et al. 2021). Over time, one of the most conventional technique applied to extended freshness quality was the use of chemical additives as was previously detailed in Chap. 4. The bakery industry is looking for novel alternatives including the use of antioxidant and antimicrobial compounds obtained from natural sources, new packaging technologies, application of functional coatings, etc. (Klinmalai et al. 2021; Silva et al. 2021; Nallan Chakravartula et al. 2019a). Traditionally, to select a suitable packaging material for bakery products, the most important properties usually sought are gases and water vapour barrier, UV barrier, thermal stability, mechanical resistance (Roy and Rhim 2020). The most used packaging materials to preserve bread are different types of paper, such as waxed paper or the glazed imitation parchment which is strong and has grease resistance. It is usually impregnated on both sides with paraffin wax containing low density polyethylene (LDPE) and other additives (Martins et al. 2021). One alternative is LDPE bags with a strip of adhesive tape at the end to be twisted and sealed. Cakes and pastry products, which are more susceptible to crushing damage, are usually packed in grease-resistant paperboard bags with transparent cellophane windows and wrap, such as cling film, plastic nests or aluminium foil base plates and double plastic film layers. For long shelf-life products (biscuits and other), cellulose films coated with LDPE are generally used (De Pilli 2020; Galić et al. 2009) or other multi-layered films such as aluminium-coated LDPE, oriented polypropylene (OPP) or acrylic-coated OPP films which represent more effective barriers to oxygen and water vapour. In the case of fresh baked stuff immediately consumed, it is commonly packaged in bags made of polyolefin film, such as LDPE or polypropylene bags, normally microperforated to allow moisture to escape and avoid leathery consistency of the crust (Pasqualone 2019). Regarding packaging methods, the application of new technologies such as vacuum packaging, nitrogen flushing, modified atmosphere, functional or active packaging (with antimicrobial activity) reduce the growth of spoilage microorganisms, extending bakery products shelf-life (Qian et al. 2021). It is important to highlight that the plastic derived from fossil hydrocarbons comprise 46% of global plastic waste generation, producing a huge impact to the environment, which often end up in landfill sites or oceans, causing a significant pollution due to the poor infrastructure, the lack of recycling options and to the long periods of time required for their degradation (Tiseo 2021; Geyer et al. 2017). Thus, there is a wide interest in the development of new materials for substituting plastic packaging by using renewable resources to reduce polluting residues. In this framework, biodegradable packaging has emerged as an innovative and promising solution since they decompose after fulfilling their purpose (Chiralt et al. 2020; Tapia-Blácido et al. 2020). New biodegradable materials can be classified in chemically synthesised polymers made from natural or petroleum-based molecules (polylactic acid, polycaprolactone, polyvinyl alcohol, polyglycolic acid, polybutylene succinate, polybutylene adipate-co-terephthalate); directly extracted from biomass (biopolymers such as cellulose, starches, chitosan, alginate, gelatine, collagen, etc.) and biosynthesized via microbial fermentation (polyhydroxyalkanoates, bacterial cellulose) (Zhang et al. 2022; Kamarudin et al. 2022; Birania et al. 2022). These have been used to develop new eco-friendly and active systems that could be applied to protect or improve quality of GF bakery products. In the following sections of this chapter, a special description of biodegradable and edible matrices is performed.