Abstract

Native Brazilian fruits are rich in bioactive compounds, such as carotenoids and phenolic compounds. This is one of the reasons why their pulps and by-products became so popular. However, to make them accessible to different places, special care in their packaging is necessary. Not only does it provide protection from physical damage, but also prevents diseases and chemical contamination. Furthermore, there are additional advantages of its properties for developing biodegradable packaging. This recent review highlights the increasing development of edible films and coatings to preserve native Brazilian fruits. Brazil produces a wide variety of tropical fruits that remains underexplored, offering numerous possibilities for research, new products, and development of biodegradable packaging. Diverse, rich in nutrients and highly perishable, native Brazilian fruits can be sold in various countries, not limited to tropical regions, depending on the sustainable development of packaging. Therefore, we encourage future studies to integrate native Brazilian fruits into food and industrial applications across different parts of the globe.

1. Introduction

The consumption of minimally processed fruits and vegetables has steadily increased due to the convenience and health benefits associated with their high content of vitamins, antioxidants, minerals, and dietary fibers ^{1, 2}. The growing interest in fruit consumption draws attention to typical fruits commonly found in Brazilian markets, which is the third largest producer of fruits globally ³. Brazil produces a great variety of fruit species, both native and exotic, with excellent nutritional and commercial characteristics. Some of these species have gained prominence in tropical fruit production, including fresh consumption and the development of processed food products for domestic and foreign markets ^{4, 5}.

However, the production of minimally processed fresh fruit (MPF), especially when the fruit is climacteric, faces some difficulties related to increased exposure to oxidative stress and the action of browning enzymes on the surface of fresh-cut fruits ⁶. Changes in the color of MPF compromise consumer acceptance, as the visual aspect of the product is among the most significant quality attributes ⁷.

Packaging plays a crucial role in fruit preservation. It not only protects from physical damage, but also prevents diseases and chemical contamination, ensuring freshness and nutritional quality during long-distance transportation and prolonged storage ^{8, 9}.

Modified atmosphere film packaging has been widely used for fruit and vegetable storage ¹⁰. One of the most promising approaches to extend the shelf life of foods sensitive to oxidative and microbial deterioration is by incorporating antioxidant and/or antimicrobial active components in packaging and coatings ^{11, 12}. In edible antioxidant films and coatings, natural active compounds are generally preferred over synthetic additives due to consumer’s perception of natural components as healthier.

The coating of fruits and vegetables involves techniques that maintain their freshness over an extended period. These techniques include controlling moisture transport, surface ablation, and reducing the permeability of O₂ and CO₂ ¹³. In addition, coatings in direct contact with fruits and vegetables provide mechanical support, resisting overall quality degradation in terms of texture, appearance, color, and weight loss ¹⁴.

The main factors influencing physiological processes in fruits during storage and the occurrence of adverse changes are temperature, humidity, and the levels of oxygen and carbon dioxide in the storage environment. The appropriate balance and interaction of these factors significantly impact the characteristics and properties of stored fruits ¹⁵. Additionally, modern storage technologies include modified atmosphere with specific gas compositions tailored to the rate of biochemical changes in the fruit, allowing for extended storage without compromising biological quality ¹⁶.

Respiration observed during storage involves the conversion of compounds produced and accumulated during photosynthesis with the participation of oxygen. It also relates to compounds that influence fruit taste (e.g., sugars and acids). The application of the aforementioned technologies allows for the slowing down of this process, thereby preserving the desired organoleptic characteristics ¹⁷.

Mendes & Pedersen ¹⁸ assert that bio-based plastic packaging materials exhibit reduced climate impact compared to conventional packaging materials. However, it is essential to consider other environmental impacts associated with bio-based materials. When designing new innovative plastic packaging materials for food, some parameters should take precedence to ensure more sustainable packaging.

According to the authors, these materials should feature optimal barriers to enhance food shelf life and minimize food loss. Additionally, the packaging should be designed with (mechanical) recycling in mind, and bio-based materials should be efficiently produced from second generation feedstock.

In contrast, conventionally used synthetic polymers outperform biopolymers. Biopolymers tend to have inferior barrier, thermal, and mechanical properties compared to their synthetic counterparts ¹⁹. This limitation restricts their commercial applications, especially in areas like food packaging. One partial solution to these challenges involves crosslinking, grafting or functionalization of the monomers ²⁰. Notably, several biodegradable and bio-based polymers have been extensively studied for food packaging, including poly(lactic acid) (PLA) ²¹, polyhydroxyalkanoates (PHAs) ²², chitosan ²³, and proteins obtained from animals (gelatin, caseinates, etc.) and vegetables (soy, gluten, etc.) ²⁴.

Brazil is known for having the highest biological biodiversity globally, with a vast array of plant species. Many of these species thrive in the Southern Region, encompassing the states of Paraná, Santa Catarina, and Rio Grande do Sul ^{25, 26}. Researchers have increasingly focused on native Brazilian fruits due to their potential to enhance human health ²⁷.

Despite Brazil’s favorable climatic and geographical conditions for cultivating these species and their remarkable economic and nutritional potential, they remain underutilized by both the general population and the food industry ^{28, 29}.

A wealth of native fruits grows distributed across Brazil, each harboring interesting pharmacological and nutritional properties suitable for food and medicinal purposes ³⁰. Unfortunately, many of these fruits remain relatively unknown, leading to insufficient research and consumption. Factors such as limited consumer interest, low commercial value, and inadequate investment in research and development have pushed some of these species toward extinction ³¹.

Some studies have shown several promising pharmacological properties associated with native Brazilian fruits, including antioxidant, anti-inflammatory, antidiabetic, anticancer, antiviral, and antitumoral activities. These properties, associated with the protection from degenerative biological processes and chronic diseases ³², are attributed to bioactive compounds (e.g., phenolics, terpenes, and alkaloids) present in these fruits ³³. Additionally, some of these fruits contain chemical structures that could potentially replace synthetic additives commonly used in food products ^{34, 35}.

This review highlights the increasing use of Brazilian fruits in the development of edible films and coatings. These fruits, rich in nutrients and highly perishable, serve as valuable resources for creating new products and biodegradable packaging. The convergence of these ideas suggests that sustainable packaging solutions using native Brazilian fruits can extend beyond tropical regions and be adopted globally.

To present this topic systematically, the research was conducted in the scientific database “Web of Science”. Using keywords such as “tropical fruit coating” OR “tropical fruit edible film” OR “tropical fruit packing” in titles or abstracts, 5270 relevant documents were published between 2015 and 2024. This review focuses on the last five years of publications or the highly-cited articles from earlier years. Considering that reports about native Brazilian fruits are still limited, this review provides an overview on the most recent developments in edible films and coatings using tropical fruits. These innovations serve either to enhance the fruits themselves or to protect them from deterioration.

2. Main Types of Biodegradable Packaging

Edible coatings can be defined as thin layers of edible materials formed on the surface of food products, typically by immersing the food in a solution containing the coating material. On the other hand, an edible film is a preformed thin layer made of edible materials. These materials are first molded into solid sheets and then applied as a wrapping around the food product ^{36, 37}. Edible coatings are formulated using biodegradable natural polymers due to their recyclability, cost reduction potential and minimal pollution and waste generation ^{38, 39}. Researchers have focused on transforming fruit and vegetable waste into other valuable products to address environmental pollution ⁴⁰.

Both edible films and coatings have been shown to extend the shelf life of fresh fruits and vegetables. They achieve this by reducing moisture and solids migration, controlling gas exchange due to respiration, and inhibiting oxidative reactions ^{41, 42, 43}. Additionally, they can carry different active ingredients (colorants, flavors, antioxidants, nutrients, antibrowning and antimicrobial agents, among others), further extending shelf life and reducing pathogen growth on food surfaces ^{44, 45, 46}. These characteristics have elevated edible films and coatings to one of the most significant research topics in food science and technology. Over the past 5 years, more than 1700 scientific articles related to this issue have been published, according to the scientific database “Web of Science”

Edible films and coatings derived from plant-based natural products, including natural polymers (proteins, polysaccharides, and lipids), and plant-derived secondary metabolites (e.g., essential oils), play a crucial role in fruit storage ^{47, 48, 49, 50}. These materials are environmentally friendly and highly biodegradable ⁵¹, and their proper use may have no adverse effects on human health.

The potential impact of edible films and coatings derived from natural plant-based products is closely related to their ability to create a barrier on the fruit surface. This property makes them useful for reducing the movement of atmospheric gases and water vapor ¹³. Besides that, natural plant-based products may retard ethylene production, reduce free radical activity and oxidation, prevent enzymatic degradation, and also control physiological changes ^{52, 53}.

Several studies have explored the development of edible films containing fruit purees or juices ^{54, 55, 56, 57, 58}. The polysaccharides naturally present in fruits serve as film matrices or co-matrices, while sugars act as plasticizers. Furthermore, the sensory and nutritional properties of the fruits contribute to the market appeal of fruit-containing films. These edible films are usually produced using biopolymer matrices, such as pectin ^{58, 59, 60} or alginate ^{61, 62}.

The development of films and coatings based on polysaccharides has experienced significant growth in recent years due to their interesting mechanical and barrier properties ^{63, 64}. Starch, a polysaccharide, finds wide application in the food industry due to its easily availability, low extraction cost, biocompatibility, biodegradability, edibility, and good film forming ability ⁶⁵. Several studies have shown the successful incorporation of antioxidant agents (both natural and synthetic) into starch films for the development of active packaging ^{2, 12, 52, 66, 67, 68, 69}.

However, starch-based edible coatings exhibit high water solubility and poor water vapour barrier properties due to their hydrophilicity, which can limit their application in high moisture products and environments ⁴⁶. Starch possesses remarkable functionality attributed to two major components: amylose and amylopectin, as well as their organization within the granular structure. The effectiveness of the starch in forming better edible coatings and films depends on the amount of amylose present in the specific starch source ⁷⁰.

The application of starch-based edible coatings is extensive due to their lack of smell or taste and their ability to reduce gas exchange ⁴⁶. These coatings effectively preserve the organoleptic and nutritional properties of food ⁷¹. Currently, there is significant interest in obtaining starch with improved physicochemical and functional characteristics from nonconventional sources ⁷². Moreover, starch is an abundant, low-cost, renewable, and easy to use polysaccharide ⁷³.

Bananas (Mussa paradisiaca) are both an interesting source of starch and an important food crop extensively grown in tropical and subtropical regions worldwide. Unripe bananas contain approximately 36% starch and are readily available in local markets ⁷⁴. Banana’s starch stands out for its higher amylose content compared to potato and wheat starch, as well as its resistance to hydrolysis ⁷⁵. Table 1 provides an overview of the key characteristics and distinctions between edible films, edible coatings, and starch-based packaging sources.

3. Biodegradable Packaging and Native Brazilian Fruits

The main findings and results from recent research on edible films and coatings produced with native Brazilian fruits are summarized in Table 2. These studies explore various fruit types and food products that have benefited from these innovations.

Promising environmentally friendly solutions to replace problematic plastic packaging for regenerated cellulose films can be found in nearly all the studies listed in Table 2. In addition, different methodologies have been developed to optimize the composition of edible coatings for application on various native Brazilian fruits, including acerola, cajá, mango, and pitanga. Researchers have also investigated the impact of using edible films and coatings on the physicochemical characteristics and post-harvest shelf life of these fruits.

Rodrigues et al. ⁶³ described the first study that developed active films using chemical fractions extracted from Spondias purpurea L. (seriguela). Sophisticated methods, including Refractance Window drying, were employed to obtain a dehydrated product with high technological and nutritional quality for use in the food industry, as demonstrated by Nascimento et al. ⁷⁶ with mammee apple pulp (Mammea americana L.).

In studies where bioactive compounds were used for the development of films and coatings, antifungal and antimicrobial activities were observed. These properties helped preserve the physicochemical characteristics of fruits and added further value to the final results ⁷⁷. Viana et al. ⁷⁸ found that films containing mango or guava puree exhibited significant differences in tensile properties, water vapor barrier, and water resistance compared films without any fruit purees. These findings lead us to consider the distinct properties that native Brazilian fruits can offer.

4. Conclusions and Future Trends

This review highlights the abundant possibilities that native Brazilian fruits offer. Whether for the development of edible films and coatings or the creation of innovative packaging strategies for their distribution, these fruits are diverse, rich in nutrients, and highly perishable. By ensuring sustainable packaging practices, native Brazilian fruits can be marketed beyond tropical regions, reaching consumers in various countries. Therefore, we encourage further research to integrate these fruits into the food industry globally.

Funding: The authors would like to thank Capes (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) for the financial support.

References