Fruits are an essential source of vitamins and dietary fiber that are indispensable for human health and wellbeing. However, fruits are highly perishable; they can get damaged during transport and marketing and have short shelf lives –”shelf life” refers to the time that a product, especially medicine and food, can be kept before it becomes too old to be sold or consumed–. Producers can apply wax to protect them from decay and dehydration.
Naturally, fruits produce their own coating –the epicarp– or wax to protect themselves from drying or getting oversaturated with water when it rains. However, once the fruit is picked and washed, the natural protection comes off along with the residual dirt and chemicals from the orchard. Coatings can be used to preserve fruits for a longer time.
Nutrition and waste
Water is the main component of fruits. It can reach almost 90% of its weight for cantaloupes and watermelons, and close to 80% for apricots, oranges, blueberries, pineapples, peaches, raspberries, and plums. The passage of time after harvest and environmental conditions can cause excessive loss of moisture in fruits, resulting in wilting and shriveling, as well as disagreeable textures, which can negatively affect the fruit’s appearance edible quality.
Coatings can be applied to reduce moisture loss, slow post-harvest decay, extend the product’s shelf life. Using coatings make it possible to close small cracks and dents in the skin and create a physical barrier to stop bacterial and fungal pathogens from affecting the product.
Apples are perhaps the most known fruit to be waxed, but it certainly not the only one. Citrus fruits, stone fruits, avocados, cucumbers, tomatoes, melons, peppers, and even jellybeans are commonly coated.
The most recent FAO report on food loss and waste showed that 14% of the total food produced is lost between the post-harvest and retail level. If we consider only fruits, this amount is close to 22%. Preserving foods and lowering loss and waste is essential to ensure that the food system is more sustainable and equitable.
What are coatings made of?
Coatings have been used for a long time as a way to preserve fruit. Indeed, the records show that the Chinese began using coatings in the twelfth century after noticing that it slowed water loss and fermentation; Chinese citrus farmers used to pack oranges and lemons in wooden boxes filled with wax before shipping them. By the fifteenth century, the Japanese used a film made by boiling soymilk to coat their fruits before storing them. In the US, hot melt paraffin waxes were used since the 1930s to cover fruits and carnauba wax and oil in water emulsions since the 1950s to protect fruits and vegetables. Afterward, different edible films were made from various polysaccharides, proteins, and lipids.
Modern coatings are made from a mixture of resins, beeswax, sugarcane, carnauba, and other substances, and they accomplish two tasks, preserving the fruit and making it look appealing. Waxes can delay fruit ripening by controlling its respiration, inhibit the growth of mold, protect the fruit from bruising when it is being handled or traveling, while at the same time enhancing its appearance by giving it a glossy shine.
Furthermore, edible coatings made from natural ingredients are an environmentally ideal package; they are biodegradable, can be directly consumed, and their main ingredients come from renewable sources. This is a clear contrast from synthetic materials, such as paraffin, polyethylene, and plastics that come from a limited supply of fossil fuels.
Even though synthetic and natural coatings fill the same role, they are certainly distinct. Among the main advantages of choosing natural coatings is going in line with current consumers’ preferences, who are more inclined to buy natural -or naturally- based products. Therefore, coatings made from shellac, rosin, gum, ethanol from sugar, and other ingredients are highly desirable.
According to researchers from McGill University, modern coatings can be made of up to 50 different components, most of which are in the esters chemical category. Among the most commonly used ingredients in current waxes are carnauba wax that comes from the leaves of a Brazilian palm, shellac extracted from the Indian lac bug, and candelia wax that originates from a desert plant. Commonly used synthetic esters are made by mixing sucrose and fatty acids. Polyethylene can also be applied in a fine layer, as an alternative ethylene derived from corn ethanol can be used.
Among the main benefits of using natural ingredients to prepare coatings are the inherent characteristics of each component, for example:
- Preservation of quality attributes and good water vapor barrier from using guar gum, candelilla wax, glycerol, and gallic acid.
- Good oxygen barrier property and transparency from whey protein.
- Smooth and homogeneous coating layer, and hydrophilic surface from using soy protein.
Are coatings safe to eat?
Videos and posts have appeared claiming that wax is unsafe to eat; however, those claims are not true. Waxes are used in small amounts to give a microscopic coating that surrounds the product’s surface; thus, each piece of fruit only has a drop or two of wax. Furthermore, coatings used on fruits and vegetables have to pass strict regulations from the US Food and Drug Administration or the European Food Safety Authority.
Coatings used on fruits and vegetables have to meet the regulations ordered by the authorities in each territory. The regulatory agencies are constantly researching the effects that any additive can have on human and environmental health to ensure that they are safe. People concerned about animal byproducts or allergens can check the point of sale information displayed alongside the waxed fruit.
Even though it is possible to develop new waxes from a wide selection of available materials, both synthetic and natural, it is paramount to ensure that the products can fulfill their role; protect food products from deterioration processes, including oxidation, moisture absorption/desorption, chemical reactions, and microbial growth, as well as to improve their physical strength, reduce particle clustering, and possibly improve visual and tactile properties of food product surfaces (Pirozzi et al, 2020)
Why should you prefer natural coatings?
Recently, the study and development of natural coating materials have attracted a lot of attention from researchers. This can be seen in the wide use of Aloe Vera gel and other polysaccharides, or seaweed extracts that have an intrinsic antimicrobial activity, which significantly contributes to longer shelf life. This tendency also extends to the use of natural gums, starches, cellulose, and other compounds recovered from agri-food residues. Glycerol is also being used as a plasticizer, and natural extracts, including essential oils and different plant and fruit extracts, are used as antimicrobial or antioxidant agents.
Among the main advantages gained by using edible coatings are:
- Reduction in weight loss and an improvement in fruits’ firmness.
- Reduction in respiration rates and ethylene production, which delay senescence.
- Prevention of injuries related to chilling and storage.
- Encapsulation of aroma compounds, antioxidants, and pigments that stop browning reactions.
- Reduction of the use of packaging material.
- Improvement of external appearance by providing an extra shine in the surface of the fruit.
However, not all coatings are equal. Food regulations differ in different areas of the world, and the European Union is recognized as one of the most astringent territories in this regard. Regulation (EC) No 1333/2008 of the European Parliament on food additives stipulates the several uses for which each food additive, including coatings, can be used.
European Union Food Regulations and the role of natural wax
The European Union recognizes several ingredients that can be safe as fruit coatings; they include Beeswax (E 901), Candelilla wax (E 902), Carnauba wax (E 903), Shellac (E 904), and Microcrystalline wax (E 905). All of them have been tested multiple times as glazing agents and have shown no safety concerns. Furthermore, beeswax, carnauba wax can be used as organic coatings.
Wax coatings can be used in organic produce. In this case, they have to come from a natural source, such as beeswax, wood resins, or carnauba wax; they also have to be certified by a recognized authority in each territory.
By using protective coatings to preserve fruits, it is possible to increase the product’s longevity, increasing the possible days in a gondola by 40% compared with untreated products.
Shel-life® by PolyNatural, your coating alternative
PolyNatural offers Shel-life®, a natural, invisible, washable, tasteless “natural packaging” for each fruit. Their products can be used in pomaceous, citrus, stone fruits, and avocados; and they are developing a natural coating for blueberries, cherries, and kiwis. Their products are already approved to be used in the US with several organic certifications such as OMRI, Ecocert, and NSF.
Shel-life® has been tested several times. In 2018, it performed better than the control in organic apples by reducing the incidence of rot (0.4% vs 2.3%) and dehydration rates (4.7% vs. 4.9%). When tested against conventional apples, Shel-life® demonstrated the same performance as synthetic coatings.
When comparing the performance in nectarines in 2017, Shel-life® proved to be 132% superior in controlling rot incidence than other synthetic waxes while also lowering dehydration rates (2.9% vs. 3.6%).
In preserving plums, Shel-life® proved to perform better than other organic and conventional products both in rotten incidence and dehydration. And when the performance in oranges and easy peelers was tested, Shel-life®’s proved to be equal to synthetic coatings.
Most recently, in 2020, Shel-life® was tested in lemons and avocados and its performance was proved to be better in both cases. In lemons, it provided 75% less dehydration and 50% less incidence of rot; and in avocados, Shel-life® was shown to reduce dehydration rates (9,8% vs. 12%) and to extend shelf life by 20%.
If you are looking for a natural solution to make food last longer while taking care of it in transport, protecting it from fungal and decay, in that case, Shel-Life can be your solution.