Module 6. Hygiene

Lesson 11

11.1 Introduction

Adoption of good manufacturing practices is the key to producing 'quality products'. When the personnel involved in manufacture adhere to certain norms, their working hours turn out to be pleasant, orderly and safe.

The good manufacturing practices requirement specified are designed to:
  • Assist employees to maintain high quality standards, wholesomeness and safety of products manufactured and distributed by the dairy plants.
  • Educate employees about correct sanitary practices.
  • Stress the importance of personnel hygiene and cleanliness.
11.2 Personnel Hygiene

All employees must maintain a high degree of personal cleanliness to prevent dairy products from contamination.

11.2.1 Employee grooming and hygiene related items

No person shall spit, use tobacco, pan masala, chew betel leaves, take food, drink water or consume beverages or store clothing or personal belongings in any room where dairy products are manufactured or stored or in places where utensils, packing materials or ingredients for the preparation of dairy products are stored.

No person who is a carrier of disease or who is suffering from any infectious disease, open sore or communicable infection of the skin, shall be engaged in the manufacture of dairy products. In case of doubt the authorized doctor shall check the employee for any illness. Hair

Hair is an extraneous matter hazard and must be kept out of the product. Hair must be neatly combed.

* A head covering to contain the hair, as completely as possible, in the form of hairnet, and / or cap provided by the dairy, must be worn at all times. If the hair is not enclosed by a cap, then a hairnet must be worn.

* No hair pins, bobby pins, hair clips or any other similar clip is allowed to keep a head covering in place. They must be enclosed in the hairnet. Hair extending over the ears or beyond the top of the shirt collar must be protected by a hairnet.

* Bump helmets are not considered effective hair restraints and, if worn, an approved hair covering restraint must also be worn underneath.

* No person should comb their hair at the work place.

Men shall preferably be clean shaven. The mustache should be properly covered so that chances of hairs failing in the products do not arise. A neat closely clipped moustache and neat sideburns are permissible if:

* The mustache is no wider than around outer edge of mouth and extends no longer than the bottom of the mouth. Handlebar style moustache will not be permitted.

* The sideburns are trimmed no longer than the lobe of the ear. Curved sideburns extending towards the corner of the mouth will not be permitted.

* Beards are an extraneous matter hazard. Because of the risk of hair loss, any beard must be completely covered and enclosed with a clean, disposable mask. Hands

* Hands touch products or product packaging all the time and this may become hazardous to the products. Keep hands and finger nails clean. Keep finger nails properly trimmed. Long finger nails are unsuitable in a dairy.

* Wash hands thoroughly in a hand-washing facility before commencing work and after each absence from the work area.

* After visiting the rest rooms, toilet, after smoking and at any other time when hands have become soiled or contaminated, employees must wash their hands before returning to their work area.

* In areas designated as critical hygiene areas, hands must be sanitized in the solution provided upon entering the area.

* Perfumed hand lotions and hand soaps are not permitted.

* Any person with cuts or unprotected sores on fingers must not start work, but must report to their supervisor and then to the medical centre.

* Cuts and open sores on fingers must be covered by a colored band-aid type dressing applied by the authorized Medical Officer or an authorized person. Standard flesh colored band-aids or dressings are not acceptable. Clothing

* Clothing is provided to protect the product from contamination. Clothing must be clean at the start of production and kept clean during production.

* Where clothing becomes soiled rapidly, disposable or plastic aprons should be worn over it and changed frequently for additional protection against product contamination.

* If you work in a very dirty or contaminated area, such as effluent disposal area, change into clean clothes before entering the plant.

* Pockets above the waist are not allowed. Pockets must be removed or sewn shut to prevent use and to eliminate a product contamination risk.

* When sweaters are needed, they must be worn under the outer garment to avoid product contamination with loose fibers. Sweaters should be 'short haired (smooth)' close knit and lint-free.

* Maintain gloves used for handling food and food contact packaging supplies intact and in sanitary condition. Gloves shall be of food grade material. If gloves are worn for handling food and food packaging they must be kept clean and only worn for this purpose. Gloves shall be rinsed in sanitizing solution before handling any product. Hands must be washed and sanitized even though gloves are worn.

* Do not carry pens, pencils, thermometers, spectacles, tools, etc., in shirts, coats etc., above the belt or waistline, or behind the ear. This would prevent articles from falling into the product.

* Do not use decorative buttons on shirt or apron. They may fall in product accidentally. Jewelery

Rings, ear rings, badges, watches and other jewellery must not be worn while on the job because:

* Hand jewelery cannot be adequately sanitized against bacteria transmission.

* Jewelery may fall into product.

* Jewelery is a safety hazard with machinery.

Exceptions for Wearing Jewelery:

* A necklace or chain where applicable worn under a shirt or T- shirt.

* Small plain sleeper ear rings.

* A plain wedding band which cannot be removed is the only exception to this requirement. Shoes

Keep shoes clean, neat and in good condition. Safety boots and shoes should be worn only at the work place and not in any other place to avoid contamination. In critical aseptic areas footbaths must be used by all personnel whenever they are provided. They are an essential part of sanitation procedure. Other Habits

Smoking is permitted only in authorized areas. Hands must be washed after smoking and before re-entering the production area. Chewing of betel leaves, pan masala and tobacco is permitted only outside the factory premises. Mouth and hands must be washed after chewing and before re-entering the production area.

11.3 General Safety Measures to be Followed in the Dairy Plant

* Food or drink is not permitted in the plant. Drinking water is provided at drinking fountains / basins.

* Maintain lockers clean and free of soiled clothing and food materials to prevent attraction of pests.

* Avoid uncontrolled, uncovered coughing or sneezing in manufacturing and packaging area.

* Wear safety goggles where chemical materials are used and handled.

* Hearing protection must be worn in designated area. They must be kept clean. Do not leave them on equipment surfaces when not in use.

* Mask should be used in designated areas.

* Nobody should be allowed to enter production area without wearing the apron and cap.

* Use of muffler is prohibited in production area.

11.4 Water Quality

11.4.1 Impurities in water

Rain water is nearest approach of chemically pure water. But it contains small amounts of organic matter dissolved gases; principally O2 taken from the air. The composition of the ground over which and through which it flows after falling to the earth will determine the additional impurities that observe. The earth’s surface contains large amounts of mineral salts such as carbonated, SO4 such as lime and Magnesia which are dissolved by water.

11.4.2 Dissolved matter

The substances commonly found in solution are minerals, salts, gases.

11.4.3 Suspended matter

The suspended matter impurities include mud & sand, vegetable matter decayed, waste and sewage, bacteria.

11.4.4 Amounts of impurities in water

Calcium and Magnesium salts may be present in solution in amounts upto 800 ppm. Most natural water contain only relatively small amounts of Na salts, although some parts of country there are water with high contents with Sodium salts. CO2 is found in deep well water in quantities upto 40 ppm. Surface water ordinarily contain not more than a few ppm. Dissolved O2 is not usually present in deep well water but is found in surface water in amounts varying upto the limit of solubility which is about 14 ppm at 0°C.

11.4.5 Colloidal suspensions

This consists material of so finely divided that it cannot be seen under the microscope and existing in a state intermediate between true suspension and solution but removable by filtration. Matter in colloidal suspension does not settle out easily where ordinary suspended material will settle out with relative rapidity.

11.4.6 Purposes of purification

The purifying done by cities, municipalities to make the water suitable for general domestic supply.

* Purified process to improve the visibility of water for their particular requirements including boiler feed.

General domestic supply is desired to make water wholesome and pleasant to drink and object of purification is to remove the bacteria that cause disease, turbidity, colour, taste and odour which cause the water to be distasteful to the consumer .

filtration & chlorination

Sedimentation process used to settle out suspended solids in water under the influence of gravity.Water is preserved in reservoirs or storage basins until the greater part of suspended impurities settle to bottom decanted to the top.

Aeration or other process may be used to remove odors; special means may be required to remove iron and manganese.

Water is usually not softened by municipal supply. The softening is meant for the removal of dissolved salts which cause excessive soap consumption and scale deposition in boilers and pipelines.

11.4.7 Industrial water supply and softening

In this the softening occupies the most important place. Although sedimentation, filtration, aeration etc are frequently required as adjunct to the softening process. Hard water deposits scale in pipelines, boilers and cause economic loss.

11.4.8 Effect of hard water

* Scale formation.

* Scale formation in pipelines and boilers.

* Cause insulating effect which prevents transfer of heat.

* Corrosion

11.5 Water Purification Methods

11.5.1 Sedimentation Plain sedimentation

The largest use and single method for removing impurities in water is plain sedimentation. The water is allowed to stand quite or move very slowly through artificial or natural basins until such of suspended impurities settled to water and the relatively clear water form on top. Dissolved impurities including the mineral salts cannot be removed but only the suspended matter can be removed.

The degree of impurities removal depends on:

* Length of the retention period

* Size of suspended particle

* Temperature of water (Higher the temp, faster the rate of settling)

* Sedimentation basins and size of suspended particles

Sedimentation basins may be operated continuously or intermittently. For operation, two or more basins are required. One is for standing and another is for withdrawal of the water. Plain sedimentation does not include chemical to any sedimentation to the water. The amount of turbidity by plain sedimentation will cover 60 to 70% for bacterial removal. Coagulation & sedimentation

To reduce the retention period of the sedimentation bags and using smaller basins efficiently a coagulant chemical is fed to water as it enters. The coagulant reacts with alkaline salts, which are naturally present in the water and forms gelatinous precipitate which settles with relative rapidity and carried down with suspended matter with water. The most commonly added chemical is alum or aluminium sulphate. Water supply to dairy

An ideal water supply is one that is regular, adequate, soft cold and free from all impurities. The sources for water supply may be from wells, rivers, tanks and city water supply. About 4-5 liters of water is required per liter of milk handled depending on the type of plant before laying out the water supply system. Therefore, it is necessary to assess the qualitative requirement of water for the plant under consideration. The storage tank should be designed for about two days water requirement. Water Requirements

* Dairy plants require large quantities of water for steam formation, heating and cooling processes, for cleaning and washing equipments and floors, etc.

* Refrigeration machinery requires about 2 gallons per minute per ton of refrigeration.

* Single stage condensing pans require about 2 to 3 gallons of water per pound of water evaporated.

* Cooling of milk requires a ratio of 3:1, 3 parts of water to 1 part of milk.

* Bottle washing requires one gallon per minute and washes approximately 4 bottles per minute Can washing approximately 2 gallons of water per can is needed.

* Water is needed for washing equipment which may be from 20 to 50 gallons per 1000 pounds of milk. Water resources

The sources of water supply are usually only two:

* The company's own supply.

* The public supply - Under the control of municipal authorities.

11.6 Treatment of Hard Water

Hard water contains calcium and magnesium salts in solution as carbonates and sulphates. Hard water is not suitable for washing as it won't give froth with soap and is also unsuitable for cooling and for some of the industries. Therefore, hard water requires treatment before use. In a tank of hard water, proper proportion of milk and lime is added and stirred with mechanical stirrer and allow settling and the clear water is pumped out and then the tank is washed and the process is repeated. This is an intermittent system, but there will be water softness where the system is a continuous one.

11.6.1 Reutilization

Large quantities of water are required for removing the heat from certain equipments, e.g., refrigeration, compressors, milk condensing units, etc. It is a good practice to re­utilize the same water. But, to utilize the water, we have to cool the water to the desired temperature. For this purpose spray ponds and tower coolers will be very helpful.

11.7 Standards for Water in a Dairy Plant

As per BIS (IS : 425), water to be used in a processed food industry shall contain coliform less than 1 / 100 ml, SPC not more than 50 / ml. It should be free from thermophilic organisms. Chilled and hot water are free from these requirements. The hardness of water which is used in dairy should have less than 10 ppm of calcium carbonate.

Table 11.1 Bacteriological standards for dairy plant water quality


Total colony count/ml












On the basis of these standards, the dairy can decide which kind of treatment is needed for its water supply. This is very helpful in determining the water quality of a plant and what preventive or control measures to be taken to tackle the problem.

11.8 Water Treatment

A good number of methods are available for water treatment. They are filtration, ozone treatment, etc. The most effective process is chlorine treatment. It is said that a residual chlorine level of 0.3-0.6 ppm is sufficient to produce safe tube well water supply.

Last modified: Friday, 5 October 2012, 6:45 AM