Fraunhofer Institute for Process Engineering and Packaging IVV
Food safety is essential for minimally processed foods
Minimally processed foods are products that are usually only washed, cut, and packaged, without any physical or chemical preservation steps. Their freshness and naturalness make them increasingly popular on the refrigerated shelves of supermarkets and in the food service sector. Many of these products are marketed with the claim that they can be eaten without further washing.
The disadvantage of minimally processed foods is their rapid spoiling due to microorganisms. This can jeopardize food safety. The natural microflora in the products restricts their shelf-life and presents a not inconsiderable risk of pathogen transmission to humans. Studies have confirmed the relationship between minimally processed foods, such as salads and fresh fruit salad, and the transmission of infection[1],[2]. Proven pathogens here include bacteria such as listeria, salmonella, and Escherichia coli, and also viruses such as norovirus and hepatitis viruses[3].
The use of physical methods to reduce the number of microorganisms on food products is little practiced due to the sensitivity of foods. In order to guarantee the quality and safety of foods, it is often necessary to justify the use of preservatives for reasons of consumer protection. Against this is the desire of consumers for natural products and the general negativity about preservatives.
Natural hop extracts as an alternative to conventional preservatives
The AiF project "Microbiological stabilization of fish products using hop extracts" is investigating the antimicrobial activity of various hop extracts to selected microorganisms and studying their suitability from a sensory perspective and preservative effect in a variety of vegetable, fruit, and meat products.
The most active components in the extracts are the lupulones, also called beta hop acids. Extracts having a high concentration of these molecules have a notable antimicrobial effect against gram-positive bacteria such as lactic acid producers that spoil many foods. The extracts are also effective against pathogens such as listeria, staphylococci, and clostridia.
The studies that have been carried out have identified the concentration ranges in which the hop extracts have a considerable antimicrobial effect without significantly affecting the sensory properties of the food product. Although their effectiveness is greater in acid-rich, low fat products, the use of the hop extracts with meat and meat-containing products has been particularly promising. For example, the microbiological shelf-life of marinated pork could be increased by about 40%. Further series of experiments have demonstrated the use of the extract on freshly slaughtered poultry to suppress the growth of listeria. Ongoing studies are focusing on the use of the extracts in sausage products.
Hop extracts as preservatives for clean labeling
Hop extracts are a natural way of increasing the microbiological safety and shelf-life of selected foods. As these are natural preservatives they can be used for consumer-desired clean labeling. Their high activity in low concentrations means they are economical to use and have high consumer acceptance.
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[1] Callejón et al. 2015 Reported foodborne outbreaks due to fresh produce in the United States and European Union: trends and causes. Foodborne Pathog Dis.;12(1):32-8
[2] Amin et al. 2012 Factors influencing the microbial safety of fresh produce: A review. Food microbiology, 32: 1-19
[3] Seymour, I. and Appleton, H. (2001), Foodborne viruses and fresh produce. Journal of Applied Microbiology, 91: 759-773