Anti-spoilage agents for food

Food spoilage is defined as a process that renders a product unacceptable or undesirable for consumption and is the result of the biochemical activity of microbial populations that predominate in the product. Among spoilage microorganisms, bacteria, fungi (yeast and mold) are the major concerns.

Microorganism contamination at various stages of food chain is one of the major causes for food spoilage that ultimately leads to food waste, increasing food insecurity issues and substantial economic losses

Anti-spoilage agent or food preservatives are employed to ensure safety and avoid quality loss derived from microbial, physical–chemical, or enzymatic reactions.

Food preservatives are classified into two main groups: antioxidants and antimicrobials. Antioxidants are compounds that delay or prevent the deterioration of foods by oxidative mechanisms.

Antimicrobial agents inhibit the growth of spoilage and pathogenic microorganisms in food. To prevent growth of spoilage and pathogenic microorganisms in foods, several preservation techniques, such as heat treatment, salting, acidification, and drying have been used in the food industry

Various synthetic chemical preservatives are being used to control microbial food spoilage and to extend product shelf life. All chemical preservatives must be nontoxic and readily soluble, not impart off-flavors, exhibit antimicrobial properties over the pH range of the food, and be economical and practical.

Natural preservatives are easy to obtain from plants, animals and microbes. These naturally occurring antimicrobial agents can be isolated from indigenous sources using various advanced techniques.

The 5 most common food preservatives are: salt, nitrites, BHA/BHT, sulfites, sodium benzoate/potassium benzoate/benzene
Anti-spoilage agents for food

Prevention of spoilage in food

Food spoilage is a metabolic process that causes foods to be undesirable or unacceptable for human consumption due to changes in sensory characteristics. Some deterioration occurs through the spontaneous breakdown of complex organic molecules.

Most spoilage of food meant for human consumption is caused by microorganisms, which effectively compete with humans for limited and valuable food resources. Spoiled foods may be safe to eat, i.e. they may not cause illness because there are no pathogens or a toxin present, but changes in texture, smell, taste, or appearance cause them to be rejected.

In principle spoilage prevention may be achieved in the
following ways:
• by keeping out or removing microorganisms,
• by hindering growth and activity of microorganisms, and
• by killing microorganisms.

The development of food preservation processes has been driven by the need to extend the shelf-life of foods. Food preservation is a continuous fight against microorganisms spoiling the food or making it unsafe. Several food preservation systems such as heating, refrigeration and addition of antimicrobial compounds can be used to reduce the risk of outbreaks of food poisoning.

Low temperatures are used to retard chemical reactions and action of food enzymes and to slow or stop growth and activity of microorganisms. Temperatures that are just above freezing maintain foods near their original condition without special pretreatments. Storage time in such a case is limited, because some bacteria, yeasts and molds can grow at low temperatures, although this growth is much slower than at higher temperatures.

Increased temperatures can have a more permanent preservative, effect, and only require a fairly brief treatment. They may also alter the flavor of food.

Through millennia of observation and experimentation and depending on geographic location and cultural history, humans developed many methods to extend the shelf life of common foodstuffs. They learned how to manipulate osmotic conditions through the addition of sugars, salts, or lipids (e.g., sugar for jams, jellies, and syrups; salt for fish and meat; oil or fat from olives and butter) to inhibit deleterious microbial growth.

Growth of microorganisms and their activity may also be hindered by chemical agents known to specialists as preservatives. Chemical preservatives are substances which are added to food just to retard, inhibit or arrest the activity of microorganisms such as fermentation, putrefaction and decomposition of the food. Commonly used preservatives include, common salt, sugar, dextrose, spices, vinegar, ascorbic acid, benzoic acid and its salt, SO2 and the salts of sulphuric acid, nitrates, sorbic acid and its salts, propionic acid and its salts, lactic acid and its salts.

Many herbs, essential oils, and spices have demonstrated some inhibitory activity against spoilage microbes in a variety of foods. Thyme, oregano, vanillin, and cinnamon are the most commonly used.

Formulation of processed foods may include compounds that alter the water activity or pH of foods, thereby limiting growth of many organisms. 
Preserving food can help to avoid wasting of food. Food preservation involves preventing the food from being spoilt. Preservation of food is the process by which food is stored by special methods.
Prevention of spoilage in food

Protection against food spoilage

Microorganisms can grow and multiply in all sorts of environments, which cause food spoilage problems. They change flavors and textures, and may produce toxic materials.

The microorganisms themselves may cause human disease. Although foods can be sterilized (as by heat processing)and contained in such a way as to prevent contamination by microbes during storage, it still is often necessary in some cases to forego sterilization, thus making it necessary to take other steps to prevent microbial degradation of the food.

Foods can be protected against microbial attack for long periods (months to years) by holding them at temperatures below freezing. They can be preserved for shorter periods by several days by holding them in ice or in a refrigerator at temperatures in the range 32 – 46 F (0 – 7.8 C).

Foods can also be preserved by altering them to make them incapable of supporting microbial growth. Drying is an example of this type of preservation. Food must be preserved against color and texture changes.

Quite often it is either impossible or undesirable to employ conventional preservation methods, and a large variety of food additives is available for use, alone or in combination with other additives or with mild forms of concentrations 0f 0.1% or less.

Sometimes, radiation has been experimented upon as a means of preventing microbial spoilage of food. Electric energy, radiowave, etc are known to kill microorganisms. Ionizing radiations such as alpha, beta, X-rays and ultraviolet rays have also been tried for the purpose.

Sodium diacetate and sodium or calcium propionate are used in breads to prevent mold growth and the development of bacteria that may produce a slimy material known as rope. Sorbic acid and its salts may be used in bakery products, cheeses, syrups, and pie fillings to prevent mold growth.

Sulfur dioxide is used to prevent browning in certain dried fruits and to prevent wild yeast growth in wines used to make vinegar. Benzoic acid and sodium benzoate may be used to inhibit mold and bacterial growth in some fruit juices, oleomargarines, pickles, and condiments. It also be noted that benzoic acid is a natural component of cranberries.

Mould spoilage of bread is generally prevented by the addition of food grade preservatives such as propionic, sorbic and acetic acids and their salts.

Aeration plays a major role in food spoilage. By creating anaerobic conditions, the action of spoilage organism may be reduced, Complete evacuation of air or replacement or air with CO2 or nitrogen may help in preventing the action of microorganisms. But some of the anaerobic organisms, if present, may become more virulent and cause damage to the food products.
Protection against food spoilage

Preservation by High Osmotic Pressure

Osmotic pressure is the force with which water tends to move across a wall or membrane, the relative concentration of solute molecules in either side of the membrane drives water flow towards the side with the higher solute concentration.

Bacteria reach osmotic equilibrium by two means:
1. In hypertonic environments (environment having an osmotic pressure higher than that of the bacterial cell) the volume of the protoplasts will shrink. Water from the interior of the cell goes into the surrounding medium resulting in the shrinkage of the cell – phenomenon called plasmolysis.

2. In hypotonic environments (an environment that solution having an osmotic pressure lower than that of the bacteria cell) the rigid wall will resist increase in protoplasts volume at a limiting volume of water; equilibrium results from turgor against the wall. Water from surrounding media can enter the cell resulting in swelling- the phenomenon is known as plasmoptysis.

One of the major functions of the bacteria cell envelope is to present, or at least slow down, the influx of deleterious compounds from the environment.

The rigid wall present in the bacteria cells enables most bacteria to tolerate even extremely dilute environments. Osmotic equilibrium is achieved by the development of turgor pressure against the wall. The cell wall of gram positive species, such as mycobacteria acts as an effective permeability barrier. The wall of gram positive micrococci can withstand 22 atm of pressure.

Although the walls of gram-negative rods have lower tensile strengths, the wall is sufficiently strong to retain the turgor pressure if the cell is suspended in water.

Turgor against a rigid wall is apparently a much simpler development than the mechanism utilized by many protozoa for similar purposes.

Turgor pressure is almost essential to growth and consequently must be almost maintained despite variations in the external osmolarity.

Cell membranes are semi-permeable that contain various system (typically called pumps) to help attenuate the effects of osmotic pressure.

Protozoa contractile a vacuole to pump out the water in adapting to osmotic pressure in order to maintain equilibrium.
Preservation by High Osmotic Pressure