In her doctoral thesis, carried out at the Faculty of Food Engineering (FEA), researcher Margarita Andrade-Mahecha developed a biofilm of biri flour (a tuber originating from the Andes, widely consumed in Colombia as a biscuit) that managed to increase the baking time shelf life of foods such as fresh mushrooms – from 12 to 15 days, three days longer than packaging made today with synthetic material. The work was supervised by FEA professor Florencia Menegalli.

The task was not simple and involved working with one of the most challenging problems of biodegradable materials, which is the fact that they are very hygroscopic and end up retaining greater moisture, not to mention their low mechanical performance compared to other materials. Due to its high starch content in the rhizome (a type of stem), biri has potential as a raw material for commercial production of both starch and flour.

In the thesis, the author carried out several tests and, at each stage, sought new methodologies with the aim of improving the mechanical properties, as well as reducing the water solubility and permeability of these materials. To achieve this, a series of biofilms was created using biri flour and mixtures of biri starch and cellulose in microcrystalline form (which has great affinity with biopolymers). 

In the last stage, the doctoral student produced her own cellulose nanofiber from biri pomace, adapting a process for obtaining industrial cellulose. The nanofibers were developed under milder conditions and then added to the film-forming suspension to produce the films. 

Margarita noticed how this affected solubility, water permeability and mechanical properties. And all the experiments achieved significant improvements in these properties, although it will still take some time to reach the properties of a synthetic polymer, Florencia estimates. 

For now, the materials studied can now be used as coverings for cut fruits which, with the addition of antioxidant or antimicrobial principles, lead to a greater conservation effect.

In addition to Margarita, other postgraduate students dedicated to this line of research (testing packaging produced from biopolymers, new materials that play an extremely important role – they do not harm nature) have already developed biofilms with various types of flour, starch and proteins, made with unconventional materials. The idea is to produce materials for packaging and packaging food, aiming to preserve it during storage and transport of products.

Among the most recent work carried out in the group for which Florencia is responsible, the properties of fibers to act as reinforcing material for biodegradable films are currently being analyzed. Various types of processes were even tested, in which the charge of the nanofibers, size and diameter were measured.

Furthermore, other types of films were designed at FEA, for drier products, suitable for placing in plastic trays, with a process entirely conducted with biodegradable material. 

In her study, Margarita investigated the thermal and functional properties of starch and flour, films added with microcrystalline cellulose, nanofiber production and hydrolysis, seeking application in edible coatings based on biri starch (Canna indica L.) for fresh mushrooms (Agaricus Bisporus), stored under refrigerated conditions.

Banana

One of the latest works points to a fruit rich in potassium, the banana, from which flour and nanofibers are obtained for the production of nanocomposites. Fresh green bananas, after being cut into slices, are dehydrated and then crushed. This way, the banana flour is ready. 

The bark is also used. Cellulose nanofibers are manufactured from it, a material that will later be added to films. “We seek to make full use of the fruit”, says Florencia. 

The teacher reports that the work began with flour because, to make a biodegradable film, a protein and a fat are normally added. In the case of cereal flour, it already comes with these components, in which all polymers are compatible, from a chemical point of view. The decision to add cellulose was intuitive, she says, after thinking that cellulose extracted from the product itself would be more proactive and incorporate better into the mix. 

As some researchers, led by Florencia, have been working hard in the field of formulation, at some stage there will be application for even more specific uses. Currently, the group is studying the coating of fruits prior to drying. Figs, starfruit and persimmons are sliced ​​and a coating is applied to them, and then dried. 

At this point, the topping is added with vitamin C, citric acid and other fruit juices, such as strawberry. Such a covering protects them during drying because, otherwise, several functional properties would easily degrade. 

This process does not yet have wide commercial use: covering fresh or dried fruits. However, for them to go on an industrial scale, the fact that they are biodegradable in itself already constitutes a great appeal.

According to the professor, the importance of these studies lies in expanding the range of options and making full use of food, since, to give you an idea, 40% of banana production is wasted.

In order to shed light on the subject, Florencia supervised a work addressing the fruit, entitled “Banana flour films (Musa paradisiaca): evaluation of film properties in terms of process variables”, chosen among the 12 best, of the 800 presented in oral form and poster, from the International Congress on Engineering and Food 11th (ICEF11). 

One of the most representative events in the area of ​​Food Engineering, ICEF11 was held in Greece last year, with the authors being postgraduates Franciele Pelissari and Margarita Andrade-Mahecha, and professor Paulo Sobral (from USP), in addition to Florencia. The study addressed the formulation of films from banana flour.

Publication

Tese: “Microcomposites, nanocomposites and coatings based on biodegradable materials obtained from biri (Canna indica L.)”
Author: Maria Trindade Marques Bizzarria
counselor: Florencia Cecilia Menegalli
Each: Faculty of Food Engineering (FEA)