|
|
|
You can get e-magazine links on WhatsApp. Click here
|
|
|
|
|
|
Flavours and actives with edible films and coatings
|
|
Wednesday, 01 October, 2014, 08 : 00 AM [IST]
|
|
Sumant Naik
|
|
fiogf49gjkf0d Introduction
Edible films and coatings are promising systems for improvement of food quality, shelf life, safety, and functionality. They can be used as individual packaging materials, food coating materials, and active ingredient carriers. They can also be used to separate the compartments of heterogeneous ingredients within foods. In fact, edible films and coatings can incorporate food additives, such as anti-browning agents, antimicrobials, flavours, colourants, and other functional substances.
Enhanced sensory properties of a food can be achieved by adding flavouring agents to an edible film or coating, leading to development of new flavour delivery systems that improve food quality and utility. Currently, there are numerous applications of edible films and coatings whose main purpose is to impart desirable mouthfeel to the coated product; this is especially true for snacks (e.g., popcorn, corn chips, and potato chips), nuts, meat, fish, and poultry. Further, incorporation of active ingredients can enhance functionality of edible films and coatings, thereby providing health benefits to consumers.
Historical background
Application of edible films and coatings to foods to extend their shelf life is not a new practice. Edible films and coatings have been used for centuries to prevent moisture migration, improve food appearance, and increased product shelf life. Wax coatings on whole fruits and vegetables have been used since the 1800s. In fact, coating of fresh citrus fruits (oranges and lemons) with wax to retard desiccation was practiced in China in the 12th and 13th centuries.
Currently, edible coatings are widely used on whole fruits such as apples, pears, oranges, lemons, and grapefruits, to reduce water loss, improve appearance by imparting sheen to the food surface, provide a carrier for fungicides or growth regulators, and create a barrier for gas exchange between the commodity and external atmosphere. In fact, application of a coating to tropical fruits is essential because they are susceptible to weight loss and, in some cases, to physiological breakdown. Coatings for tropical fruits such as mangoes, avocados, papayas, melons, and pineapples usually consist of emulsions composed of carnauba wax.
Preserving meats, nuts
Edible films and coatings have also been used to preserve meats, nuts, snacks, and candies. A good example of this is M&M chocolate candies. The practice of applying edible coatings to candy was originally introduced in 1941 to overcome lack of chocolate sales during warm summer months. The coating application kept chocolate from melting during storage and handling.
Edible films and coatings as carriers of flavours, colourants and spices
As previously outlined, edible films and coatings can deliver and maintain desirable concentrations of colour, flavour, spiciness, sweetness, saltiness, and so on.
Several commercial films, especially Japanese pullulan-based films, are available in a variety of colours, with spices and seasonings included. Owing to their excellent oxygen barrier properties, pullulan films can be used to entrap flavours and colours and to stabilise other active ingredients within the film.
Currently, the US Department of Agriculture’s (USDA’s) Agricultural Research Service (Albany, California), in cooperation with Origami Foods (Pleasanton, California), has developed vegetable and fruit edible films as alternatives to the seaweed sheets (nori) traditionally used for sushi and other Asian cuisine. These wraps, produced as soft and pliable sheets using infrared drying, can be made from broccoli, tomato, carrot, mango, apple, peach, pear, as well as a variety of other fruit and vegetable products. They can also be used to contain spices, seasonings, colourants, flavours, vitamins, and other beneficial plant-derived compounds.
Edible films and coatings carrying nutraceuticals
Edible films and coatings also have capacity to hold many active ingredients that could be used to enhance nutritional value of food products. However, few studies have actually reported integration of nutritional or nutraceutical ingredients into edible films or coatings of foods, though there is a recent growing interest in this area. For such applications, the concentration of nutraceuticals added to the films or coatings must be carefully studied in relation to basic properties (e.g., barrier and mechanical) of carrier films. Some studies have reported that edible coatings might serve as excellent carriers of low levels of nutrients for fruits and vegetables, thereby improving nutritional value.
Edible films and coatings to carry probiotic organisms
Incorporation of probiotics into functional edible films and coatings has been scarcely studied. Recently, Tapia developed probiotic edible films for coating fresh-cut fruits. In this work, feasibility of alginate (2% w/v) and gellan (0.5%) based edible coatings as carriers of organisms, such as bifidobacteria, was investigated in an attempt to obtain functional probiotic-coated fruits. Fresh-cut apples and papayas were successfully coated with alginate or gellan film-forming solutions containing viable bifidobacteria.
This work represents a recent advancement in the use of edible films and coatings as carriers of diverse food additives, and opens new possibilities for development of probiotic film and coating products.
Edible films and coatings to carry antimicrobial agents
Active compounds, such as antimicrobials, can be incorporated into edible films and coatings. These antimicrobial edible films and coatings inhibit spoilage and pathogenic bacteria by maintaining effective concentrations of active compounds on food surfaces. There are several categories of antimicrobials that can be potentially incorporated into edible films and coatings: organic acids (acetic, benzoic, lactic, propionic, sorbic); fatty acid esters (Glyceryl monolaurate); polypeptides (lysozyme, peroxidase, lactoferrin, nisin); plant essential oils (cinnamon, oregano, lemongrass); and nitrites and sulfites. Within these categories, plant essential oils are outstanding alternatives to chemical preservatives, and their use in foods meets consumer demands for minimally processed natural products. Essential oils are designated as “Generally Recognised as Safe” (GRAS) and are used as flavouring agents in various foods.
Edible films and coatings to carry antioxidant agents
Antioxidants are used to protect against oxidative rancidity, degradation, and enzymatic browning in fruits and vegetables. Ascorbic acid such as cysteine and glutathione have been widely studied, individually and in combination, for their ability to prevent enzymatic browning, to serve as sulfite substitutes, and to improve shelf life of minimally processed fruits applied alginate- and gellan-based coatings to fresh-cut apples and papayas, demonstrating that coatings were good carriers for antioxidant agents, including cysteine, glutathione, and ascorbic and citric acids. Most of these antibrowning agents, however, are hydrophilic compounds, and may increase water vapour transmission rate and induce water loss when incorporated into films and coatings.
Technical development
Edible films and coatings can be applied by different methods such as brushing, wrapping, spraying, dipping, casting, panning, or rolling. Dipping is advantageous when a product requires several applications of a coating to obtain uniformity on an irregular surface. After dipping the product and draining away the excess coating, the film is allowed to set or solidify on the product. Casting is another technique used to apply edible coatings to food. For casting, film forming solutions are poured onto a level surface and allowed to dry, usually within a confined space. Casting produces freestanding films that exhibit a specified thickness, smoothness, and flatness. Depending on firmness and flexibility, cast films can then be used to wrap surfaces. This wrapping technique allows films to be cut to any size, and serves as an innovative and easy method for carrying and delivering a wide variety of ingredients such as flavourings, spices and seasonings that can later be used to cover foods. This method is especially useful when applied to highly spicy materials that need to be separated from the food product. Another technique, spraying, provides a more uniform coating. Spraying is desirable when a coating application is needed only on one side of the food product or when a dual application must be used to achieve the desired. Sometimes it is advisable to heat product after spraying to hasten the drying process and to improve uniformity of film solution on the food surface
.
Properties and functions
Potential properties and applications of edible films and coatings have been extensively reviewed. Edible films and coatings are known to improve product shelf life and food quality, as they are selective barriers to moisture transfer, oxygen uptake, and loss of volatile aromas and flavours. When used to coat fresh-cut fruits and vegetables, edible films may reduce deleterious effects concomitant with minimal processing. Moisture barrier properties of edible films and coatings have been extensively studied by measuring their water vapour properties, because of water’s key role in deteriorative reactions. Edible film coatings made from naturally occurring polymers, such as polysaccharides and proteins are regarded as good oxygen barriers because of their hydrogen-bonded network structures, which are very tightly packed and ordered.
Current state and recent advances
There are multiple applications of edible films and coatings in the food industry. These include (1) oxygen-sensitive foods, such as nuts, to extend shelf life and reduce packaging; (2) nuts, to prevent oil migration into surrounding food components (e.g., nuts in chocolate);
(3) fragile foods, such as breakfast cereals and freeze-dried foods, to improve integrity and reduce loss due to breakage; (4) fresh fruits and vegetables, whole and pre-cut, to extend product shelf life by reducing moisture loss, respiration and colour change; (5) moisture-sensitive foods or inclusions, (e.g., nuts, cookies and/ or candies in ice cream) to provide a moisture barrier to keep products and inclusions crisp; (6) low-fat and non-fat snack foods, (e.g., chips) to keep seasonings adhered to products; (7) frozen foods, to prevent oxidation, as well as to prevent moisture, aroma or colour migration; film separation layers for heterogeneous foods; and film pouches for dry food ingredients. Within these applications, use of edible films and coatings as carriers of active substances stands out as a promising application of active food packaging.
Regulatory status
Edible films and coatings can be classified as food products, food ingredients, food additives, food contact substances, or food packaging materials. Therefore, edible films and coatings should follow all required regulations pertinent to food ingredients, since they are an integral part of the edible portion of food products. To maintain product safety and quality, all film-forming components, as well as any functional additives in the film-forming materials, should be food-grade, nontoxic materials; further, all process facilities should be acceptable for food processing and should strictly observe current Good Manufacturing Practice (GMP) Ingredients acceptable for use in edible films and coatings should be GRAS, and used within any limitations specified by the Food and Drug Administration (FDA).
Future trends
Development of new technologies to improve carrier properties of edible films and coatings is a major issue for future research. Currently, use of such edible films and coatings is limited. One of the main obstacles is cost, restricting their application to products of high value. Besides cost, other limiting factors for commercial use of edible films and coatings are lack of materials with desired functionalities, cost of investment for the installation of new film production or coating equipment, difficulty of the production process and strictness of regulations. In spite of these limitations, the food industry is looking for edible films and coatings that can be used on a broad spectrum of foods, add value to their products, increase product shelf life, and/or reduce packaging. However, more studies are yet necessary to develop new edible films and coatings containing active ingredients to understand interactions among components used in their production. When flavourings and active compounds (e.g., antimicrobials, antioxidants, and nutraceuticals) are added to edible films and coatings, mechanical properties can be dramatically affected.
(The author is CEO, ITC Colors)
|
|
|
|
|
|
|
|
|
|