A, shows a flowchart of the process of making lacquer from tomato pulp for metal packaging. First, the tomato fruit is processed to make various tomato products (e.g. sauces, soups, ketchup, etc.). The resulting by-product, namely tomato residue, was hydrolyzed in basic medium and the corresponding unsaturated and hydroxylated fatty acids from the peel and seeds, respectively, were extracted. These molecules are dissolved in a mixture of water and ethanol and then sprayed onto the metal substrate. Finally, a bio-based polyester is prepared by molten polycondensation. B, the system boundary is considered for LCA. Credit: Cleaner Production Magazine (2022). DOI: 10.1016/j.jclepro.2022.135836
An international team of experts led by researchers from the Instituto de Hortofruticultura Subtropical y Mediterránea “La Mayora” (IHSM-CSIC-UMA), in Malaga, and the Instituto de Ciencia de los Materiales de Sevilla ( ICMS-CSIC-US), located in the Cartuja Science and Technology Park in Seville, has developed a tomato paste lacquer to coat the inner surfaces of metal food packaging, food and beverage cans. , among others.
Currently, steel and aluminum are the main materials used to manufacture metal cans and containers. When they come into contact with food, they can corrode metals and thus contaminate stored food. To avoid this, the inside of these containers is covered with a very thin protective layer to prevent corrosion of this metal. this adhesive SAP called epoxy and is a petroleum-based plastic that contains bisphenol A, aka BPA, an industrial chemical compound that protects food, but also releases interfering particles. to human health. “BPA is similar to estrogen, meaning it enters foods as Endocrine disordershormone-like, and has been linked to the occurrence of diseases such as cancer and diabetes, as well as growth problems in infants and adolescents,” Heredia points out.
Therefore, the use of BPA for the production of food packaging such as food and soft drink cans banned in Spain under the Waste and Polluted Soils Act for the circular economy 2022.
In the search for a solution, the researchers repurposed the by-products obtained from processing tomatoes to make gazpachos, sauces or juices, which are made up of seeds, skins and small stalks. Today, tomato pulp is treated as solid wasteburned or to a small extent used in animal feed due to its low nutritional value.
In the study titled “Bio-lacquer from industrially processed tomato residue for sustainable metal food packaging” published in the journal Cleaner Production MagazineExperts propose a biodegradable alternative to food packaging based on the circular bioeconomy of a product such as tomatoes.
Among its main characteristics, this bio- and eco-friendly plastic is derived from tomato processing residues, repels water, adheres firmly to the metal of the box covered with it and has anti-inflammatory properties. Corrosive to salt and any liquid. After experimenting with simulated food, the next step would be to test its performance on real food containers and packaging and evaluate its industrial application.
The aim is to reuse a waste product, i.e. the residue of this fruit, to make raw materials for other products, in this case cans and others. food box. “From one industrial waste we get an ecological and sustainable raw material that has a very low environmental impact, as it reduces waste generation and, at the same time, reduces the extraction of fossil resources to produce the very containers this,” as explained to Fundación Descubre by Alejandro Heredia, researcher at the Instituto de Hortofruticultura Subtropical y Mediterránea La Mayora.
Hydrophobic, adhesive and anti-corrosion paint
To obtain the resin, the experts let the tomato residue samples dry and undergo hydrolysis, which means they remove any residual water to retain lipids, in this case vegetable fats.
After the fat was extracted, they mixed it with a minimal percentage of ethanol, an organic compound known as ethyl alcohol. “We disperse the sample in about 80% water and 20% ethanol. Then, that water-dispersed grease is sprayed directly onto the metal surface to be protected. This allows it to penetrate the metal, adheres to the box shape and resists subsequent impacts. cuts in the container,” explains the study’s lead author.
To achieve the alignment of the molecules in the mixture and obtain the resin, the experts used heat. Heredia explains: “We leave the lacquer at 200 degrees for a very short period of time, between 10 and 60 minutes, and thus obtain turpentine.
In the end, the experts discovered that ketchup resin is hydrophobic, meaning it repels water. In addition, it has a high adhesion rate to the metal of the box it covers. “If the container is dropped, bumped or bumped during transport, such as in a delivery truck, the plastic acts as a protective barrier between the food,” said researcher from La Mayora. and metal”.
In addition to these qualities, this resin is highly resistant to corrosion to salts and any liquids. Heredia explains: “The compounds of this coating do not enter the food and therefore do not contaminate the product contained in the can, as is the case with BPA plastic.
Experiment with simulated food
To confirm all these properties, the experts carried out tests with a food simulant, according to the European Union regulation on plastics in contact with food. “We use products that mimic the behavior of a group of foods with similar characteristics. For example, we use ethanol solutions as if they were soups, oils as if they were creams, and absorbent polymers like maybe they’re dry food,” Heredia points out.
In addition to determining the properties of ketchup resin used as a coating inside the container, the experts assessed the environmental impact of its production.
To this end, they analyzed the entire manufacturing process, from the extraction of raw materials to the production of lacquer and its final use. They also compared these results with an equivalent process using BPA plastic and what would happen if the tomato residue was removed by direct incineration in the industry. “This analysis shows that capturing ketchup resin produces less carbon dioxide than BPA. And when we don’t use ketchup but burn it to remove it, the pollution it creates is also greater. compared to reusing it as plastic,” Heredia points out.
At the same time, they have also identified and quantified the effects on human health caused by the production of this plastic. “The magnitude of the impact is low compared with the impact of BPA use in everyday products,” warns the researcher.
After performing the tests with the food simulator, the next step would be to test the plastic’s behavior with real food. Heredia explains: “We’re going to take ketchup, tuna and other foods that are normally sold in cans, and we’ll sterilize them, put them in tins and test them to see if they’re going to withstand the harsh conditions. factual facts or not”.
More information:
José J. Benítez et al., Industrially processed tomato pulp bio-lacquer for sustainable metal food packaging, Cleaner Production Magazine (2022). DOI: 10.1016/j.jclepro.2022.135836
Provided by Fundación Descubre
quote: Tomato-based coating for interior coating of canned food and food packaging (2023, March 20) retrieved March 20, 2023 from https://techxplore.com/news/2023-03-tomato -residue-based-lacquers-coat -cans-food.html
This document is the subject for the collection of authors. Other than any fair dealing for private learning or research purposes, no part may be reproduced without written permission. The content provided is for informational purposes only.
