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Introduction to Preservatives in Cosmetics

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Update time : 2021-03-18 13:40:40
There are now around 60 different preservatives used in personal care products worldwide, and even fewer are widely and predominantly used. Many of the so-called new products are simply the result of combining different preservatives in different proportions.

  1. Definition of preservatives 

  In short, a preservative is a substance that prevents the growth of micro-organisms. In cosmetics, the role of preservatives is to protect the product from microbial contamination, to extend the shelf life of the product; to ensure the safety of the product, to prevent consumers from using products contaminated by microorganisms that may cause infection. The deterioration of cosmetics caused by microbial contamination can generally be reflected in their appearance. For example, mould and yeast often appear in places such as the edges of the packaging; products contaminated by micro-organisms appear cloudy, precipitation, colour change, PH value change, foaming, odour change, if the body is emulsified may appear to break the milk, into lumps, etc. If the amount of preservatives added is not enough, microorganisms may adapt to the surrounding growth environment and produce resistance, thus leading to corrosion failure.

  2, the mechanism of action of preservatives

  The survival and reproduction of microorganisms in cosmetics is dependent on a number of environmental factors: physical aspects are temperature, environmental pH, osmotic pressure, radiation, static pressure; chemical aspects are water sources, nutrients (C, N, P, S sources), oxygen, organic growth factors. Based on this, the mechanism of action of preservatives can be briefly summarised as follows.
  1) In some products with very low water content, such as oils and pastes, it is generally very difficult for microorganisms to grow;
  2) For most bacteria, the most suitable pH range for growth is close to neutral (6.5~7.5), strong acids and bases are not suitable for microbial growth, for example, the common fruit acid products, the preservative effect is usually better than neutral products in parallel;
  3) Increasing or decreasing the osmotic pressure can lead to the rupture of cell membranes, which can also cause membrane contraction and dehydration;
  4) Surface tension is also a cause of microbial growth, in some formulations with high surfactant dosage, microorganisms are also not easy to grow, in this regard, cationic surfactants are more prominent, while anionic and non-ionic have little physiological toxicity to microorganisms.
  5) In general, the most suitable temperature for the production of bacteria is 30℃~37℃, while mould and yeast is 20℃~25℃, so high temperature disinfection can be used, but individual bacterium after adapting to the environment, generating a protective film, even at 80℃~90℃ high temperature for a short period of time can not be killed.
  The effect of preservatives on microorganisms can only be produced if they are in direct contact with them in sufficient concentration. The preservative first comes into contact with the outer cell membrane, adsorbs and passes through the cell membrane into the cytoplasm before it can exert its effect at various sites, preventing the cells from multiplying or killing them. In practice, it is mainly the effect of the preservative on the cell wall and cell membrane, and additionally on the activity of enzymes affecting cell metabolism or on the structure of genetic particles in the cytoplasmic part.

  3、Category of preservatives

  Most of the preservatives are used by contact with the cell membrane, and certain components of the cell wall, mainly with protein reaction, to destroy the protective structure of microbial cells or interfere with the metabolism of cells, affecting the normal order of cell growth, so as to achieve the purpose of corrosion, cation is mainly by affecting its osmotic pressure, so that the cell membrane rupture, contraction and loss of water, so as to sterilize.
  Dozens of preservatives are more commonly used in the cosmetic field today and are classified according to their active substances.
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