AT-HOME MILK FERMENT PRODUCTION: FACT SHEET  

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What is Fermented Milk?

Fermented milks are prepared from milk fermented by the action of good bacteria (most commonly lactic acid bacteria) naturally found in milk or which may be added to the milk. The milk and milk products used may or may not be homogenized (mixed vigorously) so that the milk fat is evenly distributed through the milk and must be pasteurized. These good bacteria remain active in the milk even when it is consumed. There are two main species of good bacteria; these are Lactic acid bacteria and Bifidobacteria. Some examples of the good bacteria that help milk ferment are:

After fermentation, the milk should not be heated nor should the whey (liquid part of the sour milk) should not be removed. As fresh products they have a limited shelf life and should preferably be kept refrigerated.

Source: International Dairy Foundation (IDF) 1969. International Standard (Compositional Standard for Fermented milks) FIL-IDF 47, in revision. Brussels: International Dairy Foundation – with modifications

Composition of fresh milk

Nutrients in milk can differ depending on the age, breed of cattle or goat, the season of the year and the food it is fed or grass the animal grazes. On average, milk has 4% fat, 3.4 percent protein and 4.8 percent milk sugar (lactose) and provides approximately 730 kcal in energy per liter. As such a serving of 250 ml glass would therefore provide 180kcal, which 10% of an under five year old child’s energy needs for a day and 6% of a symptomatic HIV+ adult’s and energy needs., a 250ml glass of milk will provide 8 % of the needs of a HIV+ symptomatic child’s experiencing weight loss.12

Milk also provides valuable vitamins, vitamin A (for eyes, skin, hair, mucous membranes and immunity), vitamin B’s (important for metabolism of carbohydrates in foods to produce energy) and vitamin D (important for strong bones and teeth), as well as minerals, calcium and phosphorus (both of which are important for bone health). Source: http://www.fao.org/docrep/v1650t/v1650T0s.htm:- with modifications

Health benefits when milk is fermented

                                                            1 Reference for changes in energy requirements in HIV :‐ http://whqlibdoc.who.int/publications/2003/9241591196.pdf  2 Reference for energy requirements in the lifecycle : ftp://ftp.fao.org/docrep/fao/007/y5686e/y5686e00.pdf  

Effect of fermentation

Changes in milk Effect on health

Increase in lactic acid bacteria levels

Reduced lactose content in milk *

Reduced content of bad bacteria*

No diarrhea and bloating Improved gut health Prevention of protection from bacterial

vaginosis and fungal infections in women Ability to digest remaining lactose in the

fermented milk and use as energy source Breakdown to shorter chain proteins

Identification of casein peptides and whey peptides with functional properties. *

Easier digestion Some with antihypertensive effects Some with pain relief effects Some with immune enhancing properties Some with calcium binding bone building

properties

Increased acidity Sharpness of taste

Prevents harmful bacterial growth in milk*

• Lactobacillus acidophilus, Lactobacillus GG, Lactobacillus reuteri: - beneficial in reducing diarrhea from infections like shigella or rotavirus or from the effects of antibiotics.

• L. acidophilus and L. casei subsp. Rhmnosus to inhibit H. pylori • Bifido breve: diarrhea prevention • Bifido bifidum + Streptococcus thermophilus: prevented rotavirus

diarrhea • Bifido longum: decreased erythromycin induced diarrhea

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*These aspects are especially beneficial for people living with HIV because of the frequent bouts of diarrhea they experience, bloating experienced when they consume fresh milk. Additionally research shows that hypertension and bone disease are a common problem affecting people living with HIV. Also because of the immune compromised state, limiting bacterial growth is beneficial to people living with HIV.

What are Traditional Fermented Fresh Milk Products

These are milk products that have been made in different cultures for many centuries as a means of preserving milk for later consumption and preventing spoilage (wild fermentation). Only products containing live microorganisms can be regarded as traditional fermented milk products.

Making Traditionally Fermented Milk

Using boiled /pasteurized milk:-

1. To ensure that your milk is of good quality check that:- a. That you have cleaned and wiped the udders of the cows or goats with

a damp clean cloth b. You always use clean and sanitized equipment and containers to ensure

a long shelf life for your fermented milk c. The milk is free from dirt and sediment d. The milk does not smell sour e. The milk has no mould growing on it f. Milk cows that have been treated with antibiotics or that have the udder

infection called “mastitis” and discard the milk. i. Antibiotics in milk will stop the process of fermentation

because they kill the bacteria that cause the milk to ferment 2. Contact your local agricultural extension worker for a fermentation starter

culture supply which can be stored in a sealed tin, or if possible buy a package of already fermented milk / yogurt to use as a starter.

3. Filter the milk to remove any dirt. 4. Bring the milk to the boil then let it keep bubbling for 5 minutes, keep stirring to

make sure that the milk heat evenly. If sugar will be added, add the sugar at this stage.

5. After pasteurization the milk should be cooled to room temperature (the coolest part of a dark room). You can cool the milk by placing the boiled milk container in a bucket or wide open mouth basin with enough cold water to come to 2/3rds of the way up the pot and leaving it in a cool part of the room.

6. When the milk has cooled add the starter culture (1 tablespoon for every ½ liter quantity of milk). If you are using a yogurt you have bought, add 100 ml yogurt for every 1 liter of milk. This is called inoculating the milk. Stir well for 3-5 minutes to ensure it is evenly mixed.

7. Incubate at room temperature overnight (for 16 -18 hours).

8. Check the milk ferment, it should be a thick semisolid lump, this is called the coagulum. It should be compact without cracks and whey on top.

9. Break the coagulum and stir well to mix the curd evenly to a smooth

consistency.

10. Wash the containers you will use to pack the fermented milk well with soap and hot water. Then place the containers, in boiling water for 5 minutes and allow them to air dry. You can also use plastic bags and seal with a heat seal.

• Remember that your finished milk product if not kept in a refrigerator should be used within 4 days

• With refrigeration the fermented milk can be kept for 21 days.

11. After the containers that were used during milking (cans, buckets) are emptied of milk they should be cleaned as follows:

• Cold water rinse. • Scrubbed with brush and warm detergent (any unperfumed liquid soap

will do). • Cold water rinse. • Sterilization (sanitization) with boiling water or steam.

Boiling the milk is important so that

• Any bacteria or germs in the milk that can make it go bad are killed. • The fermented milk produced will be smooth and thick and viscous

product. • Stop the liquid (whey) from running the solid milk (curd) while the milk

ferments, this is called wheying off. • To ensure that the bacteria that make the milk ferment will grow well in

the milk.

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• Dry cans on a drying rack preferably in the sun. This is because exposure to sunlight will help kill off bacteria while the milk containers (buckets, cans) air dry.

Adapted from Milk Processing Guide Series Volume 4 Published by: FAO/TCP/KEN/6611 Project – with modifications

Safety issues to remember

Raw milk and other milk-based products naturally contain both beneficial and harmful bacteria. However, milk may contain harmful bacteria that can cause serious illness. These bacteria can be shed by animals into milk at the farm, or contaminated by manure on the farm. Milk is nutritionally complete which makes it an ideal environment for bacteria to grow. .

Your fermented milk may be unsafe to eat if:

• If the yogurt does not set properly • Molds, yeasts (green or yellow growths) start to grow on top of the yogurt,

even before its expiry date.

Seek medical help if you experience any of the following symptoms after consuming your home fermented milk: - Nausea, vomiting, diarrhea, fever

 

Important Note • Good fermentation : the milk smells and tastes clean • The whey is at the top and the curd is at the bottom of the container • Bad fermentation the milk has an undesirable smell and the curd floats at the top and the

whey on the bottom • Remember when the weather is cooler the fermentation process will take longer than in

the hot season. This is because higher temperatures make the bacteria more active and colder temperatures slow down the bacteria’s action.