Handling Fresh Raw Milk

…or Controlling the Funkiness of your Cheese

The most important consideration in good flavored milk and milk products is the proper handling of the milk from the time it is milked out to the time that it is consumed or made into cheese. It makes me wonder about commercially available goat’s milk, which in my experience has a strong “goaty” flavor. The goat’s milk I produce only has had such flavor problems if the steps given below were not followed. Many people who say they hate the taste of goat’s milk are usually referring to ‘store-bought’ goat’s milk, and find mine mild, sweet and rich. Likewise, many commercial goat cheeses taste like they were cured in the billy pen… NOT to my liking.

Here are the critical factors I have discovered over a couple of decades of keeping goats and making cheese. All of these are aimed at keeping bacterial contamination as low as possible. Undesirable bacteria are what make milk products have an off flavor. The goal in cheese-making is to add beneficial bacteria which produces good flavor while avoiding the rest. Undesirable bacteria abound on goat hair and dander. Removal of these is the goal of careful filtration.
Never try to make cheese out of “turned” or spoiled milk–the unpleasant flavor will linger. Feed it to your pets if they will drink it. Otherwise, put it on the compost pile.

Note that repeated reference is made to complete drying of thoroughly cleansed equipment. The reason is that most bacteria do not survive well on clean dry surfaces exposed to the air.

Avoiding Bacterial Contamination in your Milk Products

Cleanliness/Sterility of Milking Cans and Storage Bottles:

1. Immediately after milking, rinse equipment in lukewarm water to remove the majority of milk.  If you let the equipment sit, the drying milk will glue itself in the cracks and crevices, and will be come a breeding ground for bacteria.
   
2. You should carefully wash the rinsed milking cans in very hot soapy water, rinse well, and air dry COMPLETELY. (Do not dry with a towel, it is easy to introduce bacteria this way.) If you have no problems with odor or taste in your milk, actually sterilization of the cans may not be required.  But if you are having problems, your implements should be boiled and air dried.  I avoid chlorine because of its poisonousness, but in the worst cases, may have to be resorted to.

Essentials of Recommended Cleansing:

1. Wash implements well in very hot water and soap
2. Rinse thoroughly in very hot fresh water
3. Ensure that they are thoroughly air dried before using
   

If you must use chlorine for sterilization, use as little as possible, and avoid any trace in your milk.

Stages of Milk Handling

 

I.  Setting up Milking Equipment

Sterilize the washing cloth by boiling, then adding an equal volume of cool water to lower the temperature to a manageable level. (I aim for 60ºC. This is hot, but will cool as you wash the udder.) Use a very clean jug with sterile filtering cloth and lid AND a clean can into which to milk.

Secure the goat in a stanchion with goat feed to keep her happy.

Note that the washing can is hung from the stanchion, and the milking can sits ready on a nearby (cleaned) surface.

II. Setting up Goat to be Milked

Note that the washing can is hung from the stanchion, and the milking can sits ready on a nearby (cleaned) surface.

Sterilize the washing cloth by boiling, then adding an equal volume of cool water to lower the temperature to a manageable level. (I aim for 60ºC. This is hot, but will cool as you wash the udder.) Use a very clean jug with sterile filtering cloth and lid AND a clean can into which to milk.

III. Cleansing Udders

Wash the udder and teats thoroughly with the sterilized cloth. Wash the udder and teats thoroughly with the sterilized cloth. Wring out the cloth, and damp dry the udder so that no drips remain. Washing with very warm water does two things. a) It cleanses the udder, removing surface dirt, dander and hair, and b) the warmth and massaging of the washing causes milk let-down, making milking much easier.

Wring out the cloth, and damp dry the udder so that no drips remain.

IV. Milking and Feeding

Give the first squirt or two from each teat to the cats. Do this because the milk ducts contain more bacteria near the opening, and you clear out these bacteria rather than add them to the kept milk. Place a “milking board” on the stanchion, and the can on the board. This keeps the can from touching any surface that the goat may have walked on. I use a piece of white formica, one foot square, for this purpose. The can is placed on top of this “milk board.”

HOW TO MILK: Pinch the top of the teat between your thumb and index finger , trapping milk in the teat.

HOW TO MILK: Then the other fingers squeeze the trapped milk out without releasing the pinch at the top. Note the “milking board” under the can.

Alternatively, if I am only milking one or two goats, I place the sterile handkerchief over the mouth of a wide mouth jar and milk directly into the suspended cloth. This ensures that hair and dander are immediately removed from the milk, and removes any chance of contamination from the milking can.

When you get no more milk out easily, massage the gland inside the udder. This will release additional milk. Milking is done when no more milk can be coaxed from the udder, even with additional massaging. Note that the teats appear completely deflated.

V. Filtering and Recording

Optional: Weigh the milk and record it. This will help you monitor the health and productivity of your animals. Here is an overview of my home made “appropriate technology” scale to weigh milk, made from a long spring and calibrated to read out on graph paper on which I record the weights of morning and evening milkings. (Note that I am a data junky–many do not record these details.)

This image shows the gallon jug with sterile filter cloth and the freshly milked milk being weighed.

This iimage shows a detail of my home made scale.

Filter freshly milked milk immediately through a sterile fine-weave cloth.

Immediately upon milking, filter the warm milk through a fine weave sterile handkerchief (sterilized by previous boiling and complete drying) into a scrupulously clean dry jar, cleaned at least as well as the milking cans. (You may sterilize in boiling water if you are in doubt). Use wide-mouthed jars if possible since they are more easily cleansed.

This filtering removes goat hair and dander which are very rich in bacteria. These bacteria act on goat butterfat resulting in strong “goaty” flavor. [If you pay careful attention to cleansing, boiling and thorough drying of all apparatus, and still have problems with short shelf life, strong goat flavor, etc, you might resort to such poisonous chemicals as chlorine or iodine to treat surfaces.]

Release the goat from the stanchion and return to the goat room. Bring in the next goat, if there is one.

Sweep off the stanchion to remove loose dirt.

Wash down the stanchion and dry with a wrung out cloth.

Do the same for the milking board, and the resting place of the milking can.

Although these cleansed surfaces are not sterile, keeping them clean and dry dramatically reduces bacterial contamination which could transfer to the milking can.

VI. Chilling

Label the freshly milked and filtered milk with the date. The importance of rapid and complete cooling to near freezing cannot be over-emphasized in retarding spoilage. “Funkifying” bacteria HATE such cold conditions. I reserve a second refrigerator (in my garage) to chill fresh milk.

On the floor of this refrigerator, I have a large 2 gallon plastic bucket which contains as much near-freezing water as will partially float the milk jars. I keep blocks of ice floating in it so it’s temperature remains at 0ºC (32ºF). Each time a fresh jar of warm milk is placed in the chiller, a cup of water is removed, and another block of ice is added .

Chilling in this water-ice bath is much more rapid than air chilling in a refrigerator. Here the warm milk is being immersed in the ice water bath.

I freeze this ice in large strong plastic cups filled with clean water. I get a good supply of these cups at Cincinnati Reds games, picking up the discarded heavy plastic cups after the game.

VII. Cleansing Equipment after Milking

Immediately after placing the milk in the chiller, rinse the can and filtering cloth well to remove most milk. Wash the can and cloth in very hot soapy water, rinse well. Air dry the can. (Drying with a towel adds bacteria.)

The filtering cloth is boiled for a minute or two, and hung to dry in a clean location (out in the sun is perfect because of its antiseptic action.

Keep the milk chilled at 4ºC until ready for use.  Do not add warm milk to previously chilled milk.  It will encourage any bacteria in the older milk to grow.  However, once thoroughly chilled, milk from sequential milkings can be pooled.

Follow these steps and maintaining a temperature of no more than 4ºC in your refrigerator and your milk should keep easily for more than a week without pasteurization. If goat’s milk is kept this long, cream can be skimmed off when making cheese. Freeze this cream immediately after skimming to produce delicious ice cream.

If you don’t follow these steps closely, you risk a number of bacterial contaminations including those of Salmonella, Escherichia coli and reportedly, Listeria.

Bacterial Contamination of Meat: Pour Plate Assay

Weigh 1 g meat into a steril tube to suspend

Add the diluted sample to the plate. (Then pour in the melted 45 C agar.)

RELATED PROTOCOLS:
Pour Plate Technique for Bacterial Enumeration
Dilutions
Bacterial Contamination of Milk, Pour Plate Assay

DISCUSSION:
Ground beef for human consumption may legally contain up to (hard to believe) 50 million bacteria/gm. The number of bacteria in a given sample may vary by several orders of magnitude.  Therefore, when samples of these foodstuffs are assayed for bacterial count, several dilutions must be prepared over several orders of magnitude in order to achieve the desired range of colonies per plate (30-300). Typically, 1.0 mL of several dilutions from each of the dilutios ( undiluted to 10³, or higher) should be plated.  Greater dilution is necessary for more highly contaminated samples. The following procedure is for that purpose:

SUPPLIES:
Ground beef to be tested. Have date of origin, if possible. Calculate age of material.
Standard Plate Count Agar, sterile (SPCA) 15 mL in capped 16 x 150mm test tubes, melted, 45 C , three per student
Sterile dH₂O in 4 repipets capable of adjustment to deliver 1 to 10 mL aliquots.
Clean sterile petri dishes, 3 per student.

EQUIPMENT:
wax pencil
sterile 16x150mm test tubes  (four per student)
balance
stainless steel spatula in test tube with 95% EtOH
flame
45^o C  Hot Block (or water bath deep enough to equal agar depth.)   One per15 students
vortex
2.0 mL pipets, sterile , 3 per student
1.0 mL pipet, 1 per student
colony counter with magnifying glass

EXPERIMENTAL PLAN FOR ASSAYING BACTERIAL CONTENT OF MEAT:

PREP OF MEAT SAMPLE, DILUTIONS, AND ALIQUOT ADDITION TO PLATES

Label the bottoms of three empty plates with:
initials
date
specimen
aliquot volume (1.0 mL each)
dilution factor (10¹, 10² or 10³)
Prepare meat dilution blanks by labeling three 16 x 150mm sterile tubes with your initials and the exponents 1, 2 or 3 (dil’n factors 10¹, 10² or 10³.)

Prepare dilution blanks:
Repipet 9.0 mL sterile dH2O into each of the three tubes.

Prepare a 10% suspension of meat in sterile water:
Weigh out 1.00 g ground beef sterilely into a fourth sterile capped 16x150mm test tube. (Record actual amount weighted out.)
(If you only weigh out 0.8 g of meat, suspend it in 8 mL water in the next several steps. I.e., a 10% suspension.)

Suspend the weighed meat with a vortex and spatula:
Add 3.0 mL sterile dH2O 2, vortex with sterile spatula inserted to suspend well. Be sure to hold the tube near the top to prevent spraying…)
After thorough suspension, add an additional 7.0 mL more sterile dH2O. Vortex to mix well again.

In the following steps, you will prepare the serial dilutions:
Prepare serial dilutions of the specimen in steps of 10¹, vortex after each dilution to mix completely. [Greater dilution factors may be achieved by using 0.1 mL into 9.9 mL in one or more of the serial dilutions, or plating 0.1 mL into the final petri dish.]:

For the first dilution, because of chunks of meat in suspension, use an inverted 2 mL pipet as instructed:
1) Use an inverted 2.0 mL pipet to deliver 1.0 mL of sample into first dilution tube = 10¹. (Invert so that meat particles do not clog up the pipet. Draw fluid to the 1.0 mark, deliver to the 0.0 mark.)

Add the diluted sample to the plate. (Then pour in the melted 45 C agar.)

2) Use a 2.0 mL pipet to deliver first 1.0 mL of 10¹ dilution into the appropriately marked empty plate, THEN deliver the rest (1.0 mL) into the 10² dilution tube, vortex

3) Use a fresh 2.0 mL pipet to deliver first 1.0 ml of 10² into the appropriately marked empty plate, then deliver the rest (1.0 mL) into 10³ dilution tube, vortex.

4) Use a fresh 1.0 mL pipet, deliver 1.0 mL of the 10³ dilution into the appropriately marked empty plate

Melted plate count agar, 45 C is added to sample and mixed

Add 15 mL 45 C melted agar to each plate in turn, swirl well to mix completely. To ease cleaning, plunge the emptied agar tube immediately into warm water before agar solidifies

After the plate has completely solidified (be patient), invert plate and incubate 35 C for 48 hr.
Meanwhile, pour the contents of the initial meat suspension tube into the quart jar provided (do not pour down the stink, er…, I mean sink…)
The contents of the other dilution tubes may be washed down with hot soapy water.

Count the colonies on the plates and calculate CFU per mL.
Remember that colonies imbedded within the agar are quite small, while the colonies on the surface are quite large (see the image to the left).
Each counts as a colony when enumerating the total colonies formed.

Using which of the three dilution plates has between 30 and 300 colonies, calculate the CFU/g meat. (See formula below.)
Enter your results into the class table (your initials, the meat source, its expiration date, CFU /g

 

CFU/plate x meat suspension factor (10 mL/g) x dil’n factor x aliquot factor (1) = CFU/g meat

¹  On the plate shown, 1 gram of meat was suspended in 10 mL, diluted 1 to 10, 1.0 mL of the suspension was plated and 293 colonies formed.  Therefore the count per gram in the meat was 293 x 10mL/g x 10 D.F. = 2.93 x 10³/gram

²  If testing for E coli H7:O157, substitute MacConkey Broth for sterile water in this step. After dilutions are completed, place suspension in 37^oC.