For centuries, food preservation and preservatives have been used to extend food shelf-life and prevent spoilage. Preservation techniques such as salting and curing (smoke) have been used since the 14th century to prevent deterioration of meat and fish products. At the same time, fermentation has been utilized for beer, wine, and cheese making to extend products' shelf-life, improve their taste, and enhance the availability of their nutrients. The pickling (acidification (acidic solution or salt brine)) preservation technique has been used to inhibit microbial and enzyme growth in fruits and vegetables. Nowadays, food additives and preservatives have become key components in the food system, aiming to keep food fresh, safe, and shelf-stable, with an extended shelf-life. However, there is a concern of misgivings about their safety, potential health hazards, and their association with "ultra-processed" foods. This blog tends to describe the use of food preservatives, their attributes, and the truths and myths about their use in our foods.
1. Food Preservatives
Food preservatives help to control and prevent food deterioration, protecting against spoilage from enzymes and microorganisms (e.g., bacteria, yeast, molds), life-threatening botulism, and other organisms that can cause food poisoning (antimicrobial function). High-risk foods such as meat, seafood, and dairy are prone to microbial contamination; therefore, food preservatives are usually required to ensure food safety. Food additives and preservatives can prevent spoilage caused by microorganisms, chemical (e.g., oxidation) or physical (e.g., temperature, light) factors, helping to extend products' shelf-life, while preventing any alterations in food taste or, texture (antioxidant function), rancid or change color. It is important to clarify that preservatives are additives, but additives are not necessarily preservatives. Food manufacturing primarily includes additives to enhance a product’s flavor, color, or texture. Non preservative additives are used to improve or maintain the product's quality characteristics (texture, color, etc.). Therefore, food preservatives primarily protect the quality of foods, reducing costs, improving convenience, lengthening shelf-life, and reducing food waste (Wedzicha, 2002; Eufic, 2022; CIFS, 2024; Foodresearchlab, 2024).
Food preservatives are natural or synthetic additives added to food to extend food's shelf-life, acting as an antimicrobial factor or reducing the rate of food spoilage. Antioxidants are compounds that delay or prevent the oxidation and deterioration of foods, while antimicrobial agents prevent and inhibit microbial (spoilage and/or pathogenic) (Wedzicha, 2002; Eufic, 2022; CIFS, 2024; Foodresearchlab, 2024).
2. Antimicrobial agents
Antimicrobial agents have long been researched for their effectiveness and successfully applied in killing, reducing, or inhibiting the growth of pathogens or spoilage microorganisms in and on foods. Natural antimicrobial food substances such as common salt, sugar, vinegar, or spices (ex. rosemary extract), act as effective antimicrobial agents under appropriate conditions.
Acid-antimicrobial preservatives are widely researched and used compounds that include organic acids such as lactic, acetic, and citric acids. The antimicrobial effectiveness of organic acids depends on concentration, pH, molarity, and the concentration of their non-dissociated form (Wedzicha, 2002; Eufic, 2022; CIFS, 2024). For example, ascorbic acid, Vitamin C, is used to prevent spoilage in products such as bread. Citric acid is usually added as an acidification factor in foods to control pH (below 4.6 to inhibit Clostridium botulinum germination) and enhance the flavor. Examples of foods used are jams, juices, fruit and vegetable purees (baby foods), and canned foods (ex. Ntolmadakia yalanji). Acid-antimicrobials, when used in combination with other compounds, have exhibited synergism. Potassium sorbate with lactic acid and citric acid has been reported to inhibit Salmonella, Pseudomonas fluorescent, Yersinia enterocolitica, and some lactic acid bacteria and osmophilic yeasts. Benzoic acid and sodium benzoate (at 0.1%) prevent yeast and mold growth in fruit juices and products. The organic acids potassium sorbate and sorbic acid, used in bakery products, cheese, and salad dressing, are antimicrobial effective at a pH range of 4.0-6.0 (Wedzicha, 2002; Eufic, 2022; CIFS, 2024).
Chemical-antimicrobial agents, such as sorbic acid (which can be found naturally in berries), are used in wine, cheese, and meat products to prevent the growth of yeast and mold. Benzoic acid (not water soluble) and sodium benzoate, which occur naturally in some fruits and spices, help to limit microbial growth in foods (Wedzicha, 2002; Eufic, 2022; CIFS, 2024). Benzoate contains small amounts of benzene, a carcinogen compound. Calcium phosphate is used in baked foods as a thickener and stabilizer agent, preventing lumps from forming in baked goods. Another chemical antimicrobial is trisodium phosphate (TSP), used by the poultry industry as an antimicrobial for raw, unchilled carcasses and giblets. TSP at 10% has been reported to reduce Salmonella Typhimurium by 2 log CFU/carcass. Sodium nitrite and nitrate, known as the “red” color stabilizer in meat products, have been used as the primary preservatives found in cured meats, sausage, ground beef, smoked and cured sablefish, salmon, shad, and other meat and fish products. Sodium nitrite is also an effective antimicrobial agent against Clostridium species, including Clostridium botulinum. Sodium nitrite is applied to meat or fish, it kills toxins and interacts with the proteins, increasing product’s shelf life and enhance color and flavor, widely used in major markets such as North America, Asia Pacific, Europe, and Latin America. When naturally occurring in foods, nitrates may be considered safe. However, when heating nitrites at cooking temperatures or found in large amounts, nitrosamines are produced, a carcinogenic compound. Much ongoing research explores alternative antimicrobial agents, such as spices, for meat products that can substitute nitrates and ensure antimicrobial effects against Clostridium species (Wedzicha, 2002; Eufic, 2022; CIFS, 2024).
Usually, spices are added to food products to add flavor or aroma profiles; however, many spices also contain active compounds with a certain degree of antimicrobial ability, known as bio-preservatives. Some antimicrobial active compounds derived from plant essential oils include eugenol, carvacrol, thymol, and vanillin. Some spices most effective for bacterial inhibition include allspice, bay leaves, capsicums, cinnamon, cloves, cumin, garlic, lemon grass, onion, oregano, rosemary, tarragon, thyme, tea (contain tannins and polyphenolic compounds), and prunes. On the other hand, an unreasonable amount of spice must be added to the food to achieve a high number of active compounds. Therefore, the active compounds need to be isolated and concentrated, and research must be performed on the concentrates to confirm their bactericidal and bacteriostatic properties. While increasing antimicrobial ability, some concentrated compounds may lend adverse flavor or odor depending on the food product.
In the bio-preservatives category, food preservatives have been extensively used in food preservation. Nisin is an example of a bio-preservative antimicrobial compound approved by the Food and Drug Administration (FDA) and GRAS (Generally Recognized as Safe). Nisin, produced by Lactococcus lactis subsp. lactis, is a natural preservative for many food products used in processed cheese, meats, beverages, etc. Nisin inhibits pathogenic food-borne bacteria such as Listeria monocytogenes and many other Gram-positive food spoilage microorganisms. Nisin can be used alone or with other preservatives or several physical treatments. Another example is Natamycin, a natural antimicrobial peptide produced from a microorganism known as Streptomyces natalensis. Natamycin is known for its efficacy in controlling fungi growth and is used in food products such as cheese, sausages, yogurts, juices, wines, etc. It is preferred over the other preservatives as it is free from odor and color and has a GRAS status from all regulatory agencies.
3. Antioxidants
Oxidation of food products occurs by adding an oxygen atom to or removing a hydrogen atom from the different chemical molecules found in food. Two types of oxidations that contribute to food deterioration are autoxidation of unsaturated fatty acids and enzyme-catalyzed oxidation (Eufic, 2022; CIFS, 2024; Foodresearchlab, 2024).
Autoxidation occurs when unsaturated fatty acids react with the carbon-carbon double bonds and molecular oxygen. The by-products of autoxidation, known as free radicals, are highly reactive compounds that cause the off-flavors and off-odors characteristic of oxidative rancidity (Eufic, 2022; CIFS, 2024). Antioxidants that react with the free radicals (free radical scavengers) can slow the rate of autoxidation, including tocopherols (vitamin E derivatives) and the synthetic compounds butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and tertiary butylhydroquinone (TBHQ). BHT and BHA prevent oxidization or slow damage to cells caused by free radicals. These antioxidants are considered safe in small, limited amounts. BHA and BHT prevent oxidation in cereals, dehydrated potato shreds and beverages. Another antioxidant is EDTA (ethylenediaminetetraacetic acid), used in products such as sauces, canned foods, and carbonated beverages. EDTA helps to prevent food from oxidizing, preserving any change in the appearance and taste of the food products (Wedzicha, 2002; Eufic, 2022; CIFS, 2024).
Oxidation can also occur due to enzyme activity, which may lead to spoilage and changes in the food, known as enzymatic browning, producing a black pigment, melanin. Characteristic examples are phenolases that catalyze the oxidation of specific molecules, like amino acid tyrosine, of bruised fruits and vegetables. Antioxidants that inhibit enzymatic browning include agents that bind free oxygen (i.e., reducing agents), ascorbic acid (vitamin C), and inactivate enzymes, such as citric acid and sulfites (used in wine) (Wedzicha, 2002; Eufic, 2022; CIFS, 2024). Sulfite is used to prevent browning and is listed in the ingredient lists as sulfur dioxide, potassium metabisulfite, sodium metabisulfite, sodium sulfite, or sodium bisulfite. Sulfites prevent dried fruits from rotting and are used in fruit juices and wine. Sulfites are considered safe preservatives; however, they can impact consumers with asthma (Wedzicha, 2002; Eufic, 2022; CIFS, 2024).
FAO/WHO Expert Committee on Food Additives (JECFA), FDA, and European Food Safety Authority (EFSA) conduct extensive research to regulate food preservatives based adequately on several factors, such as the desired effect, the legal limits of use, and the effect on food. The FDA evaluates and regulates ingredients added to food to help ensure they are used safely. The safety of food additives and ingredients generally recognized as safe (GRAS) must be supported by science that demonstrates its use meets the FDA's safety standard. The European Parliament and the European Council have laid down a detailed labeling system for food additives to enable consumers to make informed choices about foods containing preservatives. Legislations also stipulate that preservatives and additives are labeled on food packaging by their category (preservative, color, antioxidant, etc.) with their name or E-number. Table 1 describes the main food preservatives the food industry uses, providing the E-number and their effects on foods.
Table 1. Main food preservatives are used by the food industry (Eufic, 2022).
4. Safety of food preservatives
There has been much public concern that some food preservatives may cause health hazards for consumers. As described above, all food preservatives, natural or synthetic, should be used with consideration and after proper research. While food preservatives are considered safe for the general population, many food preservatives and additives can be harmful—even deadly—to certain people. Preservatives that exceed a certain quantity in any given food would be harmful to everyone, causing health issues. Namely, the carcinogenic compounds that may be found from excessive use of nitrates and Benzoic compounds. High levels of Sodium nitrate are linked to gastric cancer (Jakszyn and Gonzalez, 2006), while petroleum-derived antioxidants, BHA, and BHT, based on animal studies, may be carcinogenic, promoting the growth of tumors (Ito et al., 1985; Kahl and Kappus, 1993).
However, the main health concern of preservatives in foods is allergic reactions. Preservatives have rarely been shown to cause true allergic (immunological) reactions. Among the food additives reported to cause adverse reactions are some preservatives from the group of sulfite agents, which include several inorganic sulfite additives (E220-228) and benzoic acid and its derivatives (E210-213), which may trigger asthma characterized by breathing difficulties, shortness of breath, wheezing and coughing in sensitive (e.g., asthmatic) individuals (Eufic, 2022; CIFS, 2024).
More studies, especially longer-term studies, are needed to determine the true risk of consuming these preservatives over time. Testing is an ongoing process; more information will become available to food businesses when tests are conducted (Eufic, 2022; CIFS, 2024).
5. Truths and Myths about preservatives
Food preservatives are still necessary in many perishable foods to ensure safety. Food preservatives work by delaying the spoilage of foodstuffs and preventing any alterations in their taste or appearance. The following paragraphs discuss truths and myths on preservatives ((Eufic, 2022; CIFS, 2024):
• As described in the text, the truth is that most of the antimicrobial and antioxidant compounds are natural substances found in fruits, vegetables, spices, etc. This is a fact that opposes the myth that preservatives are not healthy. Vitamins (A, D, and E) provide significant antioxidants and antimicrobial properties, helping preserve food and enhancing nutritional value.
• Another myth is that all packed foods contain preservatives. In fact, food products that are properly processed (thermal process, etc.) eliminate any potential spoilage and pathogenic microorganisms without the need for preservatives. Food preservatives are mainly used to extend the shelf-life of perishable food products. Aseptically, pasteurized and canned processed foods, if appropriately done, receive adequate thermal process to kill all undesirable pathogenic and spoilage microorganisms. For this reason, the use of preservatives is not necessary for most aseptically processed and canned foods; something backed up by European and global legislation prohibiting the use of preservatives; a great example is the category of canned fish..
• Additives that are harmful to health is another false myth. As mentioned, if used in limited, regulated amounts, all food preservatives are considered safe, with no association with health problems. Excessive amounts can be harmful to specific groups of consumers. Also, food manufacturers should clearly label allergens, and consumers with health issues should be aware and careful with their choices.
• Experts recommend that preserves should not be part of consumers' diets. Nutritionists and dieticians advise that our diet should avoid foods with preservatives. This is also a common myth belief about the consumption of food preservatives. Food preservatives can have nutritional benefits, such as using vitamins as antimicrobials and antioxidants. Still, preservatives such as acid food preservatives prolong foods' shelf-life, adding flavor to the food while preserving most of the product quality aspects (nutrients, texture, taste, etc.), helping the consumer have more healthy options and achieve and maintain a balanced diet.
To conclude, food preservatives play an essential role in modern food production and safety by protecting food from spoilage, extending shelf-life, and helping maintain nutritional value. Their use enables wider distribution of food products and reduces food waste. The number of preservatives added to foods has increased significantly in recent decades, allowing food processors to extend foods' freshness. Food preservatives currently used in food production are either extracted from natural sources or synthetically produced. Public demand for 'more natural' preservative technologies and minimally processed foods has increased, making governments and research centers increasingly concerned with synthetic preservatives' effects on human health. The safe use of approved preservatives in food and beverages is highly regulated (effects, limit amount for consumption), but consuming large amounts of these additives may increase health risks. Therefore, consumers should be adequately informed and carefully read ingredient labels, allowing them to make informed choices about the additives and products they consume.
References
CIFS, 2024. Understanding Food Preservatives: What Are The Health Risks? Accessed on 20 December 2024. Available at: https://blog.foodsafety.ca/food-preservatives-what-are-health-risks
Eufic, 2022. What are preservatives and what are common examples used in food?. Accessed on 20 December 2024. Available at: https://www.eufic.org/en/whats-in-food/article/what-are-preservatives-and-what-are-common-examples-used-in-food
Foodresearchlab, 2024. An overview of food preservative markets. Accessed on 20 December 2024. Available at: https://www.foodresearchlab.com/blog/new-food-product-development/global-market-analysis-on-food-preservatives/
Ito N, Fukushima S, Tsuda H., 1985. Carcinogenicity and modification of the carcinogenic response by BHA, BHT, and other antioxidants. Crit Rev Toxicol;15(2):109-50. doi: 10.3109/10408448509029322. PMID: 3899519.
Jakszyn P., Gonzalez CA., 2006. Nitrosamine and related food intake and gastric and oesophageal cancer risk: a systematic review of the epidemiological evidence. World J Gastroenterol. 2006 Jul 21;12(27):4296-303. doi: 10.3748/wjg.v12.i27.4296. PMID: 16865769; PMCID: PMC4087738.
Kahl R, Kappus H., 1993. Toxikologie der synthetischen Antioxidantien BHA und BHT im Vergleich mit dem natürlichen Antioxidans Vitamin E [Toxicology of the synthetic antioxidants BHA and BHT in comparison with the natural antioxidant vitamin E]. Z Lebensm Unters Forsch.; 196(4):329-38. German. doi: 10.1007/BF01197931. PMID: 8493816.
Wedzicha, B., 2002. PRESERVATIVES | Classifications and Properties. Encyclopedia of Food Sciences and Nutrition (Second Edition), 4773-4776. https://doi.org/10.1016/B0-12-227055-X/00969-X
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