How do salt and sugar prevent microbial spoilage?

Answer 1

Protection of foods from microbial spoilage using salt (usually sodium chloride) or sugar (usually sucrose) has ancient roots and is often referred to as salting, salt curing, corning or sugar curing. (Pieces of rock salt used for curing are sometimes called corns, hence the name "corned beef.") Curing may utilize solid forms of salt and sugar or solutions in which salt or sugar is mixed with water. For instance, brine is the term for salt solutions used in curing or pickling preservation processes. Examples of foods preserved with salt or sugar include the aforementioned corned beef, bacon, salt pork, sugar-cured ham, fruit preserves, jams and jellies, among others.

There are numerous descriptions and permutations of curing which may include additional preservation techniques such as smoking or ingredients such as spices. However, all curing processes fundamentally depend on the use of salt and/or sugar as the primary preservation agent or agents. Incidentally, these processes not only prevent spoilage of foods, but more importantly serve to inhibit or prevent growth of food-borne pathogens such as Salmonella or Clostridium botulinum when properly applied.

There are several ways in which salt and sugar inhibit microbial growth. The most notable is simple osmosis, or dehydration. The salt or sugar, whether in solid or aqueous form, attempts to reach equilibrium with the salt or sugar content of the food product with which it is in contact. This has the effect of drawing available water from within the food to the outside and inserting salt or sugar molecules into the food interior. The result is a reduction of the so-called product water activity (aw), a measure of unbound, free water molecules in the food that is necessary for microbial survival and growth. The aw of most fresh foods is 0.99 whereas the aw necessary to inhibit growth of most bacteria is roughly 0.91. Yeasts and molds, on the other hand, usually require even lower aw to prevent growth.

Other mechanisms of salt or sugar antimicrobial activity include —interfering with the microbe's enzyme activity and weakening its DNA molecular structure. Sugar may also provide an indirect form of preservation by serving to accelerate accumulation of antimicrobial compounds from the growth of certain other organisms. Examples include the conversion of sugar to ethanol in wine by fermentative yeasts or the conversion of sugar to organic acids in sauerkraut by lactic acid bacteria.

Microorganisms differ widely in their ability to resist salt- or sugar-induced reductions of aw. Most disease-causing bacteria do not grow below 0.94 aw (roughly 10 percent sodium chloride concentrations), whereas most molds that spoil foods grow at aw as low as 0.80, corresponding to highly concentrated salt or sugar solutions. Yet other microorganisms grow quite well under even more highly osmotic, low aw conditions. For example, halophiles are an entire class of "salt-loving" bacteria that actually require a significant level of salt to grow and are capable of spoiling salt-cured foods. These include members of the genera Halobacillus and Halococcus. Food products that are concentrated sugar solutions, such as concentrated fruit juices, can be spoiled by sugar-loving yeasts such as species of Zygosaccharomyces. Nevertheless, use of salt and sugar curing to prevent microbial growth is an ancient technique that remains important today for the preservation of foods..

Answer 2

1

Answer 3

Salted meat can last for years. The salt enters the tissue and in effect binds the water, inhibiting the bacteria that causes spoilage. The salt restricts to tiny concentration and protects food from yeasts and molds. Salt has anion from hydrochloric acid. Salt is also known as sodium chloride. The salt draws out moisture and creates an environment inhospitable to bacteria.

By binding water, sugar acts as a very effective, natural preservative. For example, the high sugar levels in jams, jellies and sauces make them more immune to the microorganism development common in thinner, high-moisture products like commercial applesauce

Answer 4

These are done thru concentration gradient. See, when you put in a lot of salt on food stuffs, the water concentration tend to go from the organism to the salty solution and the salt to the organism. At some point, the organism reaches salt/sugar concentration and loses water beyond their threshold limit, thereby killing them.

Answer 5

2

Answer 6

Salt and sugar form hypertonic solution in which water concentration is lower but water always goes higher concentration to lower concentration(osmosis), so, water from microbes goes out due to osmosis. and due to dehydration microbes die..

Answer 7

they act as preservatives
they r a media where growth of microbes r almost impossible.

Answer 8

Salt and sugar, when concentrated or even pure, are ideal to kill microbes (bacteria or fungi) and prevents their colonization of our foods.
This is mainly due to the osmosis; the high concentration of salt or sugar cause the diffusion of all water from microbes cytoplasm, so that they are totally dried and die or are made inactive.

Salt is used in concentrated solutions, until 33 g/100 ml of solution, its saturation limit, to preserve for many time olives, for ex., but can also be used pure in little crystals to keep dry food into salt.
Sugar, instead, can be mixed with water in all proportions to create syrups, when water is less than sugar.

Fruits, like peaches, apricots, prunes and other fruits, if cut into pieces and boiled for 1 hour in concentrated sugar solution,(30-50% in water) can be stored for months in glass bottles totally filled and hermetically closed.
Also fruits jams are concentrated sugar products, rather resistant to microbes, but vulnerable to mold, when already open.
Instead, sugar, when diluted, creates the ideal conditions to microbes to thrive, after few time of conservation.

Protection of foods from microbial spoilage using salt (usually sodium chloride) or sugar (usually sucrose) has ancient roots and is often referred to as salting, salt curing, corning or sugar curing. (Pieces of rock salt used for curing are sometimes called corns, hence the name "corned beef.") Curing may utilize solid forms of salt and sugar or solutions in which salt or sugar is mixed with water. For instance, brine is the term for salt solutions used in curing or pickling preservation processes. Examples of foods preserved with salt or sugar include the aforementioned corned beef, bacon, salt pork, sugar-cured ham, fruit preserves, jams and jellies, among others.
Mickey Parish, chair of the Nutrition and Food Science Department at the University of Maryland, explains.
Protection of foods from microbial spoilage using salt (usually sodium chloride) or sugar (usually sucrose) has ancient roots and is often referred to as salting, salt curing, corning or sugar curing. (Pieces of rock salt used for curing are sometimes called corns, hence the name "corned beef.") Curing may utilize solid forms of salt and sugar or solutions in which salt or sugar is mixed with water. For instance, brine is the term for salt solutions used in curing or pickling preservation processes. Examples of foods preserved with salt or sugar include the aforementioned corned beef, bacon, salt pork, sugar-cured ham, fruit preserves, jams and jellies, among others.

There are numerous descriptions and permutations of curing which may include additional preservation techniques such as smoking or ingredients such as spices. However, all curing processes fundamentally depend on the use of salt and/or sugar as the primary preservation agent or agents. Incidentally, these processes not only prevent spoilage of foods, but more importantly serve to inhibit or prevent growth of food-borne pathogens such as Salmonella or Clostridium botulinum when properly applied.
There are several ways in which salt and sugar inhibit microbial growth. The most notable is simple osmosis, or dehydration. The salt or sugar, whether in solid or aqueous form, attempts to reach equilibrium with the salt or sugar content of the food product with which it is in contact. This has the effect of drawing available water from within the food to the outside and inserting salt or sugar molecules into the food interior. The result is a reduction of the so-called product water activity (aw), a measure of unbound, free water molecules in the food that is necessary for microbial survival and growth. The aw of most fresh foods is 0.99 whereas the aw necessary to inhibit growth of most bacteria is roughly 0.91. Yeasts and molds, on the other hand, usually require even lower aw to prevent growth.

Other mechanisms of salt or sugar antimicrobial activity include —interfering with the microbe's enzyme activity and weakening its DNA molecular structure. Sugar may also provide an indirect form of preservation by serving to accelerate accumulation of antimicrobial compounds from the growth of certain other organisms. Examples include the conversion of sugar to ethanol in wine by fermentative yeasts or the conversion of sugar to organic acids in sauerkraut by lactic acid bacteria.
Microorganisms differ widely in their ability to resist salt- or sugar-induced reductions of aw. Most disease-causing bacteria do not grow below 0.94 aw (roughly 10 percent sodium chloride concentrations), whereas most molds that spoil foods grow at aw as low as 0.80, corresponding to highly concentrated salt or sugar solutions. Yet other microorganisms grow quite well under even more highly osmotic, low aw conditions. For example, halophiles are an entire class of "salt-loving" bacteria that actually require a significant level of salt to grow and are capable of spoiling salt-cured foods. These include members of the genera Halobacillus and Halococcus. Food products that are concentrated sugar solutions, such as concentrated fruit juices, can be spoiled by sugar-loving yeasts such as species of Zygosaccharomyces. Nevertheless, use of salt and sugar curing to prevent microbial growth is an ancient technique that remains important today for the preservation of foods.

.....all the best.