Are substances added to food to slow or prevent food spoilage caused by microbes or oxidation. Packaged food industry has been serving as one of the fastest growing network in the present era. Numerous forms of preservation techniques such as pasteurization, freezing, drying and application of chemicals have been designed to extend the shelf-life of the food products, not only by reducing the microbial growth, but also to maintain the antioxidant potential to serve the consumers’ need. To make the packaged food quality stable for a reasonable time period, preservatives are often used in different quantity and concentrations.
Traditional food preservation has 3 goals; the preservation of appearance, the preservation of nutritional characteristics, and a prolongation of the time that the food can be stored. Hence, food preservatives can be defined as the “food additives used to inhibit the growth of micro-organisms like yeast, molds and bacteria and prevent the spoilage by different anti-oxidative reactions in order to maintain the quality, texture, consistency, taste, color, alkalinity or acidity”. Several forms of chemical preservatives are being currently in use in food and beverages industries such as benzoate, sorbates, vitamins, fruit extracts, sodium salts etc. Preservatives can mainly divide into two groups based on their purpose of usages i.e. as antimicrobial and as antioxidants.
Adverse effects of preservatives:
Though preservatives are beneficial for packaged food, they do have some negative effect on human health. All preservatives cause hyper activity on regular usage. Modern food preservatives are usually synthetic chemicals, such as sorbates, benzoates, nitrates and nitrites.
- Nitrates and Nitrites: For curing of meat products these additives are used. But sometimes it reacts to cause urticarial, itching and anaphylaxis in human beings. Sodium Nitrite is used in meat product during cooking to prevent botulism, but during high heat it reacts with the proteins to produce carcinogenic N-nitrosamines which are linked to different forms of cancers such as liver cancer, intestinal cancer and oesophageal cancer.
- Benzoates: Benzoate contained foods are strictly abandoned for asthma patients because itworsening the condition. Benzoates are also reported to cause rhinitis, chronic urticarial and flushing in some cases. Sodium benzoate which is used to enhance the self-life for a long time is found to form carcinogenic benzene while use with vitamin C or ascorbic acid. Though the amount of benzene form is low but it is a risk factor to cause cancer. It is also reported that benzoates can cause brain damage.
- Sorbates: Sorbates can cause urticarial and contact dermatitis in some cases.
- Sulphates: Copper sulphate is generally used in coloring of peas and other vegetables. It is found that the copper, when added to the vegetables, forms a compound which is not easily soluble in the human body.
However, more research in recent times have begun to shed light on the non-negligible health risks of consuming these synthetic food additives even below recommended limits as defined by regulatory agencies, such as the FDA. These health risks include allergic reactions, gastrointestinal disorders and cancer. There is therefore much ongoing interest in more “natural” sources of food preservatives, which can be plant extracts, essential oils or purified secondary metabolites.
Belonging to the phenolic class of plant secondary metabolites, are distinguished from the other phenolics by their 15-carbon, C6-C3-C6 (aryl-propyl-aryl) structural backbone. They are primarily responsible for the vivid colours of flowering plants. Aside from colour pigments, flavonoids are typically produced in plants in response to environmental changes, usually as a defence mechanism, e.g. UV exposure, pathogenic invasion. The flavonoid biosynthetic pathway occurs mainly in the plant cell cytosol, with some downstream ancillary enzymes compartmentalized in plastids. There is a tremendous and still-growing body of literature on the significant health benefits of flavonoids, spanning decades. These include antioxidant, anti-inflammatory, anticancer, antimicrobial and anti-diabetic properties.
Plant extracts containing flavonoids, such as naringenin, have reportedly demonstrated antimicrobial activities. Allied with their inherently potent nutraceutical benefits, the use of extracts containing flavonoids as novel food preservatives would therefore be highly desirable and profitable.
Plant-based food preservative that is more effective than artificial preservatives:
The organic preservative comprises a naturally-occurring substance known as ‘flavonoids’, a diverse group of phytonutrients. Though flavonoids’ anti-microbial potential have been reported, they have not been used as a food preservative because they require further processing before they can mitigate bacteria. This is known as ‘prenylation’-a process involving the addition of hydrophobic molecules onto a protein to facilitate cell attachment-which is not cost-effective or sustainable.
The flavonoids created by NTU scientists have strong anti-microbial and anti-oxidant properties; two key traits of preservatives that inhibit bacterial growth and keep food fresher for longer. NTU researchers have not only found a way to grow flavonoids with high anti-microbial and antioxidant properties but also in a natural and sustainable manner. They achieved this by implanting the flavonoid-producing mechanism from plants into baker’s yeast (a species known as Saccharomyces cerevisiae). Similar to how vaccines are manufactured using yeast, the researchers found that the yeast produced flavonoids with high anti-microbial properties, which are not even present in pure flavonoid samples extracted directly from plants.
In tests carried out on meat and fruit juice samples, the organic preservative kept its samples fresh for two days without refrigeration, compared to commercial-grade artificial food preservatives. The experiment was conducted at room temperature (about 23°C) where the other food samples with artificial preservatives succumbed to bacteria contamination within six hours.
The NTU research team was led by Professor William Chen, Director of NTU’s Food Science & Technology programme. The team aims to further develop their findings with the food industry and enhance its efficacy and safety so that it can be used in all packaged food products.
©BforBiotech by Bedadyuti Mohanty, Assistant Managing Editor by Profession and Bio-technologist by heart.