How to naturally extend the shelf life of food?

The world is changing, and so are consumer demands. Food matching modern trends has to be, above all, safe, natural and have a “clean” label. Maintaining a naturalness of product while ensuring a long shelf life requires effective solutions.

In order to obtain the best results, food preservation is increasingly being carried out with a combined system (hurdle technology), using the synergistic action of several factors that inhibit the growth of microorganisms that cause food spoilage.

The most common “hurdles” (obstacles to microbial growth) are:

• pH control
• water activity
• addition of preservatives
• application of bacteriostatic
• heat treatment
• good hygiene practice
• packing conditions
• cold storage

In this article, we will turn our attention to the use of bacteriostatic. As substances that inhibit the growth and reproduction of bacteria, they ensure the safety and extend the shelf life of food products.

Lactic acid and lactates

• synthesized during lactic fermentation
• reduce the water activity of products by water binding (thus making it less available for microorganisms)
• stabilize pH
• have an antioxidant effect and therefore inhibit the growth of Listeria monocytogenes, Salmonella typhimurium, Clostridium perfringens and Escherichia coli in food products
• improve the taste of products
• have a positive influence on protein swelling and hydration
• reduce added salt in meat products (potassium lactate, sodium lactate)
• have a positive effect on product structure and are a source of calcium with high bioavailability (calcium lactate)

Application:

• in the meat industry (for meat products, canned meat, pate)
• for cheese production
• for soup production
• for confectionery, ice cream, fruit jellies
• for canned fruits
• in the cosmetics industry

Acetic acid and acetates

A group of compounds formed by acetic fermentation. They are mainly used as:

• stabilizers
• acidity regulators
• substances with preservative effect
• dispersants

Application:

• in the meat industry
• for the production of fats and oils
• for sauces and soups production
• in bakery
• in jams, jellies and candies

In the meat industry, mixtures of acetates and lactates are often used. Both lactates and acetates show very good growth inhibitory properties against L. monocytogenes, Clostridium. They do not require high dosage (0.2 -1.5% in relation to meat used in the product). They do not negatively influence sensory properties of products (taste, smell, colour, texture). Using potassium salts allows to decrease the salt content in products (according to nutritionists, we consume far too much of it, which is harmful to our health).

The results of research clearly show that the best results are obtained with mixtures of lactates and acetates. They effectively inhibit the growth of microorganisms, including pathogenic ones, e.g. L. monocytogenes. Products prepared with lactate-acetate combinations stored at 4 °C for 90 days retain their sensory parameters such as taste, texture and colour. Moreover, in comparison with control samples (without the addition of bacteriostatic), lower growth of microorganisms and inhibition of L. monocytogenes are noted. The obtained results show that thanks to the use of compounds inhibiting the growth of microorganisms in the products is possible to extend the shelf life by 50-60%.

Perhaps in the near future we will also learn the results of research conducted by research centres on the effect of bacteriostats on the safety of meat products packaged in MAP (sausages, wieners, cooked ham).

Polyphenols

A group of compounds found in fruits, vegetables, cereal and legume seeds, nuts, coffee, tea, and cocoa, which:

• act as strong antioxidants
• effectively inhibit microbial growth (including many pathogens)
• have a beneficial effect on the cardiovascular system, by “trapping” free radicals they prevent the development of cancer cells

In recent years, interest in phenolic compounds has grown due to their pro-health, antioxidant, and antimicrobial properties. Since polyphenolic compounds are found in plant products, many studies have analysed the antimicrobial properties of plant extracts containing phenolic acids.

Scientists analysed the antimicrobial effects of phenolic acids, contained in extracts of blueberry leaves, different species of white and red wines, and salts of phenolic acids, and confirmed their antimicrobial activity. Although they did not act equally on all strains of bacteria, Gram-positive bacteria were more sensitive to the phenolic acids. The study confirmed that phenolic compounds effectively inhibit the growth of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica. They also have an antifungal effect.

Polyphenolic acids also have a strong antioxidant effect. Chlorogenic acid occurring in fruits: apples, strawberries, pineapples added in a concentration of 50 mg/l to fruit stored at 25 ° C has the ability to inhibit the formation of superoxide radical and hydrogen peroxide. Moreover, in fruits treated with chlorogenic acid, an increase in the activity of enzymes responsible for the neutralization of free radicals was noted.

Long-standing research confirming the antioxidant capacity of rosemary extract resulted in its qualification as an antioxidant food additive with E 392 code under Directive 95/2/EC. Besides rosemary extracts, water extracts of dill and thyme also have high antioxidant activity against meat lipids when added to chicken or turkey meat stored frozen for 6 months.

An alternative to bacteriostatic

Extending the shelf life of meat and fish products is also possible by using bacterial cultures. These are isolated and specially grown strains of bacteria, which through competitive displacement and production of lactic acid and bacteriocins inhibit the growth of rotting and pathogenic bacteria.

Interest in protective cultures has been growing recently due to increased consumer awareness of the impact of food ingredients on their health. Although the use of only  protective cultures may not be sufficient to fully ensure microbiological safety, they are increasingly used in meat processing as part of hurdle technology, as one of many elements designed to ensure product safety. On the shelves we can find, among others, minced meat or sliced raw bacon, which, in addition to meat, salt and other spices, contains live cultures of lactic fermentation bacteria. Analysing the needs of the market, we can conclude that this trend is bound to grow.

Sources:

• Papadopoulou C., Kalliopi S., Roussis I.G., Potential antimicrobial activity of red and white wine phenolic extract against Staphylococcus aureus, Escherichia coli and Candida albicans., Food Techolo. Biotechnol., 2005, 43 (1), 41-46.
• Sroka Z., Franiczek R., Antiradical and antimicrobial activity of extracts obtained from plant raw materials., Adv Clin Exp Med 2008, 17, 275-283.
• Stachelska A.M.. Jakubczak A., Microbial activity of salts of coumaric and cinnamic acids against Escherichia coli O157:H7 and Staphylococcus aureus in vitro., Adv.Agric. Sci., 2011, XIV (1-2), 165-172.
• Szaufer – Hajdrych M., Goślińska M., The quantitative determination of phenolic acids and antimicrobial activityof Symphonicorpos albus (L.) Blake., Acta Poloniae Pharmaceutica – Drug Research, 2004 Vol.61, No.1, 69- 74.
• Marlena Dudek-Makuch, Kinga Knoska, Justyna Chanaj-Kaczmarek Naturalne przedłużanie trwałości produktów spożywczych, Post Fitoter 2019; 20(3): 208-215    
• Anna Zadernowska, Wioleta Chajęcka-Wierzchowska, Lucyna Kłębukowska, Urszula Zarzecka, Łucja Łaniewska-Trokenheim kultury ochronne i ich  zastosowanie w ograniczeniu rozwoju pałeczek Listeria monocytogenes w surowcach  i produktach mięsnych. Kosmos Problemy Nauk Prryrodniczych Polskie Towarzystwo Przyrodników im. Kopernika, Tom 66 2017 Numer 1 (314) Strony 59–65
• Materials provided by suppliers of UNICO POLSKA Sp. z o.o. Sp. k.