Tag: #chemically

FOOD SPOILAGE

Food is considered contaminated when unwanted microorganisms are present. Most of the time, the contamination is natural, but sometimes it can be artificial too.
NATURAL CONTAMINATION occurs when microorganisms attach themselves to foods while the foods are in growing stages.
ARTIFICIAL CONTAMINATION occurs when the food is handled or processed such as when fecal bacteria enter food through improper handling procedures.
CAUSES OF FOOD SPOILAGE:

  1. Growth and Activity of microorganisms – Bacteria, yeasts and molds are microorganisms that cause food spoilage. They produce various enzymes that decompose various constituents of food.
  2. Enzyme activity – Action of enzymes start the decomposition of various food components after death of plants and animals.
  3. Chemical reactions – These are the reactions that are not catalyzed by any enzyme. E.g. Oxidation of fats
  4. Vermin – It includes weevils, ants, rats, mice, birds, larval stage of some insects. Vermin are important due to asthetic aspect of their presence, possible transmission of pathogenic agents and consumption of food.
  5. Physical changes – These include changes caused by freezing, burning, drying, pressure etc.
    SOURCES OF FOOD CONTAMINATION. PHYSICAL SPOILAGE is due to physical damage to food during harvesting, processing or distribution. The damage increases the chance of chemical or microbial spoilage and contamination because the protective outer layer of food is broken and microorganisms can enter through it. CHEMICAL SPOILAGE in food are responsible for changes in the color and flavor of foods during processing and storage. After harvesting, chemical changes begin automatically within foods and lead to deterioration. Every living organism uses specialized proteins called enzymes to drive the chemical reactions in its cell. After death, enzymes play an important role in the decomposition of living tissues in a process called as autolysis (self-destruction) or ENZYMATIC SPOILAGE. MICROBIAL SPOILAGE is due to bacteria, yeasts or molds. They produce various enzymes that decompose various constituents of food. • Besides natural microorganisms, foods can be contaminated with different types of microbes coming from outside sources such as air, soil, sewage water, humans, food ingredients, equipments, packages, insects, etc.

The primary sources of microorganisms in food may include –

  1. Soil and Water – Soil grows agricultural produce and raise animals and birds which might contain several microorganisms. Also, these microbes can multiply in soil and their numbers can be even very high as expected. Fecal materials may also contaminate soils which can act as a source of microorganisms. Sewage water can also contaminate crops with variety of microorganisms when sewage water is used as a fertilizer. So, Sewage must be always treated before using as a fertilizer.
  2. Plants and plant products – The inside tissue of food from plant sources are essentially sterile except for few porous vegetables such as radish, onion and cabbage. Also it has been observed that some plants produce natural metabolites that can limit the presence of microorganisms in those particular foods. Fruits and vegetables contain a variety of microorganisms on their surface and their presence and number depends on various factors such as disease of the plant, storage, etc.
  3. Food utensils – Many different microorganisms can contaminate food utensils from which they can transmit to human body and make them ill if pathogenic. Proper cleansing and sanitization of food utensils is required before serving food in them.
  4. Food handlers – Food handler is a person who touches or handles food. The microorganism may be transmitted from his hand to the food and may be harmful for the person consuming that particular food. The microbes can come from animals or from the environment.
  5. Animal hides and skins – Food animals and birds normally carry various indigenous microorganisms some of which are pathogens and are responsible for food-borne diseases in humans. The number of these microorganisms is less than10/g.
  6. Air and dust – Microorganisms may be present in dust and moisture droplets in the air. The microorganisms which are present in air may be transient or variable depending on the environment. Some pathogenic microorganisms may cause air-borne diseases.

CHEMICAL AGENTS IN MICROBIAL CONTROL

The chemical agents are mostly employed in disinfection and antisepsis. The proper use of these agents is essential to laboratory and hospital safety. Many disinfectants are available and each has its own advantages and disadvantages, but ideally the disinfectant must be effective against a wide variety of infectious agents. The disinfectant must be stable upon storage, odorless, or with pleasant order, soluble in water and lipids for penetration into microorganisms, and have a low surface tension through that it can enter cracks in surfaces.

  1. Phenols
    In 1867, Joseph Lister employed it to reduce the risk of infection during operations and phenol was the first widely used antiseptic and disinfectant. Today phenol and phenolics such as cresols, xylenols, and orthophenylphenol are used as disinfectants in laboratories and hospitals. Lysol is made of a mixture of phenolics which is commercially available disinfectant. They act by denaturing proteins and disrupting cell membranes.
  2. Alcohols
    Alcohols are the most widely used disinfectant and antiseptic. They are bactericidal and fungicidal but not sporicidal. Ethanol and isopropanol are the two most popular alcohol germicides. Small instruments like thermometers can be disinfected by soaking them for 10 to 15 minutes in alcohol solutions. 70% ethanol is more effective than 95% as water is needed for proteins to coagulate.
  3. Halogens
    Halogens exist as diatomic molecules in the free state and form salt like compounds with sodium and most other metals. Iodine and chlorine are the most important antimicrobial agents. Spores can be destroyed at higher concentration. Iodine is often applied as tincture of iodine, 2% or more iodine in a water-ethanol solution of potassium iodide. Skin scars result and sometimes iodine allergies can result.
    Chlorine is mostly used as a disinfectant for municipal water supplies and swimming pools and also employed in dairy and food industry. It may be applied as chlorine gas, sodium hypochlorite or calcium hypochlorite, all of which yield hypochlorous acid and then atomic oxygen.
  4. Heavy metals
    Heavy metals such as mercury, silver, arsenic, zinc and copper were used as germicides and these have nit been most recently superseded by other less toxic and more effective germicides. A 1% solution of silver nitrate if often added to the eyes of infants to prevent ophthalmic gonorrhea but now erythromycin is used instead of silver nitrate because it is more effective. Silver sulfadiazine is used on burns. Copper sulphate is an effective algicide in lakes and swimming pools. The action of these heavy metals is mostly on the proteins, and they combine often with their sulfhydryl groups, and inactivate them. They may also precipitate cell proteins.
  5. Quaternary ammonium compounds
    Detergents are organic molecules that serve as wetting agents and emulsifiers and are amphipathic in nature and hence solubilize otherwise insoluble residues and are very effective cleansing agents and are efficient from soaps, which are derived from fats.
    Only cationic detergent are effective disinfectants characterized by positively charged quaternary nitrogen and a long hydrophobic aliphatic chain. They are mostly used as disinfectants for food utensils and small instruments and as skin antiseptics.
  6. Sterilizing gases
    Gases may also be used as sterilizing agents in order to sterilize many heat-sensitive items such as disposable petri dishes and many syringes, heat-lung machine components, sutures, etc. Ethylene oxide gas is used for this purpose as it readily penetrates packing materials, even plastic wraps and is both microbicidal and sporicidal and kills by combining with cell proteins.
  7. Hydrogen peroxide
    Hydrogen peroxide effects our direct and indirect actions of oxygen as it forms hydroxyl free radical which is highly toxic and reactive to cells. As an antiseptic, 3% hydrogen peroxide serves a variety of needs including skin and wound cleansing, bedsore care and mouth washing. When it is applied to a wound, the enzyme catalase in the tissue decomposes the hydrogen peroxide into water and free oxygen. The oxygen causes the wound tissues to bubble and the bubbling removes microorganism mechanically.
  8. Acids and alkalis
    Aqueous solutions of ammonium hydroxide remain a common component of detergent, cleanser and deodorizers. Organic acids are widely used in food preservatives because they prevent spore germination and bacterial and fungal growth. Acetic acid in the form of vinegar is a picking agents that inhibits bacterial growth, propionic acid is commonly incorporated into breads and cakes to retard molds, benzoic acid and sorbic acids are added to beverages, syrups to inhibit yeasts.