Blueberries to overthrow listeria
Pathogenic bacteria are enemies of food products. Therefore, methods are used that keep them at bay. There are several treatments that improve the safety of food that reach consumers, although the challenge is that they are as natural as possible. With this idea in mind, researchers from the Food Technology Area of the University of Burgos (UBU) work, which have shown that the application of blueberry extract as a natural additive can extend the shelf life of meat products and improve the food safety thereof.
First, they studied the microbial activity in vitro against several bacteria that cause food spoilage and pathogenic bacteria that cause infections due to contaminated food consumption. Given the good results obtained against Listeria monocytogenes, Pseudomonas putida and Brochothrix thermosphacta, this extract was applied to pork burgers contaminated with these microorganisms and pork lunches infected with listeria after cooking the product.
In the first case, explains researcher Beatriz Melero, the extract maintained the concentration of altering bacteria at the levels added during a period of 16 days and a reduction of the bacteria was observed after five days of refrigeration. In the deli, the extract maintained the levels of L. monocytogenes added until 32 days. However, he points out that the cold meat without the exact one did not achieve this effect on the growth of the pathogen. In addition, it was found that the blueberry extract had a positive effect, delaying the oxidation of fats in pork burgers and that, despite the fact that the color of the product with the essence was darker than a normal cold and gave it a More acid taste, consumers did not reject these sensory modifications. Throughout the study, he added, the addition of the extract prevented the appearance of unpleasant odors in the case of pork burgers.
This step is important, since listeria is capable of surviving extreme situations such as acidity, high salt concentrations, growth at refrigeration temperatures and freezing survival. This bacterium is considered to be ubiquitous, that is, it can grow in many places and in unfavorable conditions, being, therefore, the possible sources of contamination. In fact, Melero recognizes that it can enter the food industry through the raw material due to its presence in soils, vegetation, animal skin, fecal matter, wastewater and contaminated water.
Shielding the meat against bacteria is a challenge. According to account, the foods that are usually more related to their transmission to humans are those considered ready for consumption, which are those that do not need cooking treatment to be consumed: shredded meat, cheeses made with unpasteurized milk, milk Raw, smoked and marinated fish, prepared salads, sandwiches, fresh fruits and vegetables, among others.
In this work, the Burgos team achieved that with the addition of an 2% of the blueberry extract, the shelf life of the hamburgers could be extended from five days to nine, almost double. In the case of pork sausage, the results indicate that if the product has had a recontamination with listeria the shelf life is extended to 32 days, since, without the presence of the extract, the pathogen grew without problem from the first day that The product was artificially contaminated in the laboratory. "If we focus on the bacteria that cause deterioration, the shelf life of the extract was extended by 25% with respect to the batch without extract, going from 32 to 40 days," he says.
Why this essence can mark a before and after in the food industry? Recognize that blueberries are rich in phenolic compounds that are described as natural compounds with antimicrobial activity. Among these compounds are quercetin, citric acid, quinic acid and catechins. Although the mechanism of action of these compounds in listeria is not known exactly, their antimicrobial activity is related to the ability to inhibit the synthesis of the cell wall of bacteria and therefore, the loss of crucial intracellular material occurs to The survival of the cells can also act by joining essential metals for the survival of bacteria such as iron, which is no longer available to bacteria. They can also be added to sugars, proteins necessary for nutrition, growth and reproduction of bacteria, he says.
Regarding the advantages, Beatriz Melero points out that with this project, the by-products of the blueberry juice manufacturing industry are released. «The paste that is generated due to the low pH that characterizes it, the low amount of nutrients and high amount of moisture, makes it a product not suitable for animal consumption». In this way, an environmental problem associated with this industry would be reduced.
Another step forward, ensures that it is the development of food products with added value because these extracts are rich in polyphenols, compounds that are characterized by their antimicrobial characteristics, improving their food safety and extending their shelf life. «This improves the rotation of the products in the supermarket lines. In addition, they have a potential antioxidant effect that helps stabilize the deterioration of food fats and their anti-inflammatory effects are proven, and also reducing the formation of carcinogenic compounds », it affects.
This initiative, which arises in collaboration with the Kaunas University of Technology in Lithuania, will be one more study within a line that, as the UBU researcher advances, will continue to seek to help the food industry improve its processes, its cleaning protocols and disinfection, its staff training to improve the food safety of its products and thus avoid food crises such as this summer. In addition to looking for natural products to contribute to this food safety, improving its quality and extending the shelf life of food.
They will address these plans from the classic tools of microbiology, but also with more cutting-edge and current technology that is the sequencing of the genomes of bacteria to know the presence of different genes that can help them better resist the performance of detergents and disinfectants , antibiotics, and other genes that give them a virulent character to humans. In addition, other DNA techniques to study the bacterial population that is settled in food plants or that which is responsible for food spoilage and thus be able to give a "more personalized response" to each food industry.
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