Changes in eating habits, a lack of time in the day-to-day routine of those who live in our major cities and the search for consumption without waste have led to a an increase in studies into fresh foods that can last longer on the shelf or in the refrigerator. New initiatives are arising in the form of packaging, using biodegradable biofilms and edible coverings that are taking shape in the Faculty of Food Engineering at the State University of Campinas (Unicamp). In the research groups of professors Miriam Dupas Hubinger and Florência Cecilia Menegalli the challenge is to come up with cheap, practical ad non-polluting packaging that is easy to produce.
Since 2000 Florência’s group has been concentrating on developing biodegradable packaging and edible coverings for dried fruit. Miriam and the postgraduate students she supervises have been specializing in coverings for fresh fruit and salad vegetables, the so-called minimally processed products. “Our coverings bring together two benefits: practicality for those who are going to consume the product, since the fruit is peeled, cut up and ready to eat, and a healthy appearance,” says Miriam. She explains that their coverings act like a barrier, conserving the fruit’s moisture and mineral salts and protecting it from microorganisms and contact with the air.
Simplicity was one of the reasons that led Miriam to work with flour-based coverings made from cassava starch in the form of a gel. The concentration of this material needed to form a covering is smaller than that used to make a solid film, similar to plastic, which needs the addition of plasticizing agents to remain flexible. “We favored cost, availability and ease of preparation of the covering, with the flour that becomes a gel at low concentrations and does not change the flavor of the food,” explains Miriam.
“The coverings need to be resistant to the oxygen in the air, to steam and to microorganisms, without forgetting the main thing: sensory acceptance by the consumer.” The professor adds a mixture of two natural components, citric acid, found in oranges, for example, and ascorbic acid (vitamin C) to the polysaccharides of the flour that is the basis of the covering. They are added before immersing the fruit in the covering, thus inhibiting enzymatic activity, which is one of the factors that leads to food going dark on contact with air. The food is then left for the liquid to drain off at room temperature.
The cassava flour covering solution creates a barrier, which is largely impermeable to air, but does not protect the product from the water vapor that is in the atmosphere. The resource found for protecting the food was an emulsified covering or a double layer that mixes cassava flour with lipids such as carnauba or bees wax, for example. The results using this strategy were encouraging.
Strawberries covered with cassava starch, without any antimicrobial agent, lasted 12 days, when the normal is 5. In the case of peeled pineapple, which normally has a shelf-life of 4 days, survival time was also around 12 days. Sliced mango with a cassava covering lasted as long as 15 days; normally it gets dark in just 2 days. Marcela Chiumarelli, a student who collaborated with the study of the coverings explains that “the handling of minimally processed products is still recent in the country and many markets and wholesalers do not carry out the activity correctly.”
Florência and her group are testing various compositions for producing efficient biofilms in the laboratory for different functions, such as resistance, flexibility and edibility. Among the ingredients used are unconventional sources for the production of flour and cereal starch, such as amaranth, which originates in the Andes region in South America, and more recently banana, in a film that is reinforced with cellulose nanofibers obtained from the skin of the fruit itself. They are also using montmorillonite-based nanocompounds, a mineral clay found in the sub-soil in some regions of Minas Gerais. Colorless films with reduced water solubility were produced from quinoa starch, also a native plant of the Andes.
The professor clarifies that the experiments with nanocompounds are more recent and complex. “We use flour from the banana and canna indica, which is an ornamental plant. We isolate the biopolymers and we produce a cellulosic fiber from the waste. Microfiber made from the nanoparticles makes the film less permeable and less soluble,” says Florência. This product, however, is going to take more time to reach the consumer. “We can’t look for commercial agreements because we first need to see what effect there is on humans when they eat nanoparticles.” Another study by the group is in the area of coverings for dried fruit made from biopolymers that are applied before drying. They have already been tested on star fruit, figs and persimmons.
In the United States, Nature Seal is commercially producing edible coverings that, when applied to the surface of fruit and salad vegetables, keep the appearance of pieces of apple clear, without any loss of flavor or vitamins for more than 10 days, for example. The work of Miriam’s group, particularly its research with strawberries, has attracted the attention of an important snack-bar chain in the United States and a large company in Belgium that sells cherries, raspberries and blueberries. A billionaire market is forming because fast food restaurants like McDonald’s, Burger King, Wendy’s and Jack in the Box have made their menus greener, by adding salads and fresh fruit; which makes them potential customers for biofilms.
1. Amaranth starch: study of the rheological and thermo-physical properties and the structural and physiochemical characteristics of starch and its products (gels, coverings and biofilms) (nº 2002/12137-6); Modality Regular Research Funding; Coordinator Florência Menegalli – Unicamp; Investment R$ 47,909.00 and US$ 16,092.00 (FAPESP)
2. Evaluation of the quality of minimally processed fruit with edible coverings (nº 2009/51420-4); Modality Regular Research Funding; Coordinator Miriam Dupas Hubinger – Unicamp; Investment R$ 33,108.04 (FAPESP)
CHIUMARELLI, M. et al. Stability, solubility, mechanical and barrier properties of cassava starch – Carnauba wax edible coatings to preserve fresh-cut apples. Food Hydrocolloids. v. 20, n. 1, p. 59-67. Jul. 2012.
ANDRADE-MAHECHA, M.M. et al. Development and optimization of biodegradable films based on achira flour. Carbohydrate Polymers. v. 88, n. 2, p. 449-58. Apr. 2012.