MILK PRODUCTION MANAGEMENT & DAIRY DEVELOPMENT

Module 11. Maintenance of hygiene and sanitation at dairy farm premises

Lesson 17
TYPES OF SANITIZERS AND DISINFECTANTS, SANITATION OF MILKING PARLOUR EQUIPMENT, SHEDS

17.1 Introduction

Sanitation at the dairy farm is very critical for obtaining the milk with low microbial load and improving the keeping quality of milk. The sanitation measures include reduction or limiting the contact between healthy and infected/contagious animals; prompt removal of dung, infective excreta like nasal discharges, saliva, urine etc; isolation of sick animals and immediate disposal of dead animals from the immediate environment of healthy animals. The methods of sanitation include physical, chemical and mechanical disinfection.

17.2 Maintenance of Hygiene and Sanitation at Dairy Farm Premises

Types of Sanitizers and Disinfections:

All dairy farm equipment and premises should be properly cleaned and sanitized to prevent contamination of milk, as milk provides an excellent medium for growth of microorganisms. At the same time detergents and sanitizers should be carefully selected not to affect equipment material.

17.2.1 Sanitizers

Sanitizers are the substances capable of bringing about the destruction of all non- pathogenic microorganisms and reducing the number of pathogenic bacterial contamination to a safe level. A good sanitizer should be quick acting, non corrosive, nontoxic, inexpensive, easily and quickly applied to equipment. Different sanitizers can be used at the dairy farm and they are classified as shown in Fig 17.1

Fig. 17.1 Sanitizer

17.2.1.1. Heat

Elevated temperature is the best method for sanitization and/or sterilization, as it penetrates into surfaces, is non-corrosive, is non-selective to microbes, is easily measured and leaves no residues. The type of heating that is mostly used is moist heat, for example,

• Hot and/or boiling water – Hot water circulation (85°C/15–20 min) is widely used and recommended for sanitizing processing plants. It is an effective, non-selective method for surfaces; however, bacterial spores and bacteriophages may survive. Boiling water (100°C) has limited applications but could be used for disinfection purposes; spores survive, but bacteriophages are inactivated. Free-flowing steam (100°C) is not more effective than boiling water and has limited applications. Steam under pressure may, however, be used to sterilize UHT plants.
  

• Steam (free flowing) – The use of hot water or steam is uneconomic, hazardous, corrosive to certain materials, difficult to control and therefore ineffective. The efficiency of sterilization or sanitization, using hot water or steam, is primarily dependent on three factors: the time–temperature combination (i.e. the temperature reached and the time for which the temperature is maintained), humidity and pressure.

17.2.1.2 Chemicals

The efficacy of chemical preparations used for sanitation purposes is controlled by the following factors:

• Amount of residual soiling matter on equipment surfaces;
• Temperature and pH of the chemical disinfectant;
• Concentration of the chemical compounds in the sterilizing solution;
• Contact time between the chemical disinfectant and the equipment surface;
• Type(s) of microorganisms being inactivated;
• Hardness of the water; and

• Chlorine compounds: The most common chlorine compounds used are hypochlorites. These compounds may be obtained in liquid or powder form, and their bactericidal effect is due to the release of chlorine, which is normally in the range 50–250 μg ml−1, depending on the application. At the dairy farm the concentration to be used is 200ppm of chlorine. The advantages are that the chlorine compounds are inexpensive, active against all microorganisms and unaffected by hard water salts. More over the concentration can be easily determined by field tests. Disadvantages are short residual life of compounds, corrosive on certain metals like aluminum.

• Iodophores : Iodophores are also a commonly used chemical disinfectants. The bactericidal compound is iodine, which has been combined with a suitable non-ionic surfactant to provide a usable product. These are stable compounds having long resudual life with good penetrating qualities and are non-irritating to skin. Generally a concentration of 25 ppm iodine is preferred. Disadvantages of iodophores are that they are expensive, non- effective against spores and bacteriophages, stains plastic surfaces

• Quaternary Ammonium compounds: QACs are amphipolar, cationic detergents that are surface-active bactericidal agents. They have long residual life and non irrititating to skin. They are stable to temperature changes and presence of organic matter. They are at a concentration of 200 ppm. However they are expensive, slow in destruction of coliforms and non-effective in destruction of spores, viruses.

• Acid anionic surfactant: These are formulations that consist mainly of inorganic Acids (e.g. phosphoric acid) and an anionic surfactant. These are active against wide spectrum of microorganisms and bacteriophoges. These are noncorrosive, non-straining and their bactericidal action is increased at high temperatures. They are effective in presence of organic matter or even in hard water. The concentration to be used is 100 ppm. The major disadvantage is that they are corrosive to metals other than stainless steel.

17.2.1.3 Special applications

• U. V. Radiation: Ultraviolet (UV) radiation (c. 250–260 nm), in particular, has been used with success to sterilize air entering a processing area or sterilizing packaging materials before filling.
• H₂O₂ treatment: It is a strong oxidizing agent mostly used in pure pack, packaging of UHT products. A 15% solution of H₂O₂ is recommended.

17.2.2 Disinfectants: Disinfectants are the agents that are capable of bringing about the complete destruction of all infective and other microbial life.

The disinfection of animal houses can take place by two ways.

1. Natural disinfection.

a) Sunlight b) Heat

2. Artificial disinfection.

a) Phenol b) Acids c) Heavy metal salts d) Hypochlorites

Natural disinfection: Sunlight is the most efficient due to its ultraviolet wavelength. It can act as potential disinfectant if surface is exposed directly for longer duration. Heat is the form of steam at 15 lbs pressure is useful for disinfection of dairy utensils.

Chemical disinfection: Chemical disinfectants are used generally for disinfection of farms. The germicidal action of the chemical disinfectants on microorganisms is as follows.

1. Hydrolytic and burning action on cell with acids and alkalies.

2. Oxidative action on protoplasm of cell as in case of KMNO₄, H₂O₂.

3. Protein coagulation in protoplasm of cell with alcohol and formaldehyde.

4. Disruption of cell wall and cell membrane as in case of phenol, cresol.

Phenol is a bactericidal, fungicidal but not sporicidal. It has greater effect when used with mixture of ferric chloride and ferrous chloride. Propylene glycol is active in aerosol form and has wider applications for animal premise disinfection. 1.0 % mineral acids of caustic alkali are sporicidal. Ethyl alcohol in 70% concentration is effective against bacterial flora of skin. Formaldehyde is bactericidal and fungicidal and is effective as general disinfectant in acqueous solution (5g formaldehyde in 100ml solution formalin). Ammonia is effective disinfectant in 10% acqueous solution for destruction of coccidial oocytes. Quicklime (Calcium oxide) is used for disposal of carcass by burial method. Slaked lime (Calcium hydroxide) is used as white wash of animal houses. Its usefulness increases with addition of 1% phenol disinfectant.