Module 18. Other fermented milks

Lesson 32

KISHK, YAKULT, VILLI

32.1 Introduction

Several fermented food products have been evolved from various parts of the world with different regional requirements. Some of the important products are described below.

32.2 Kishk

Kishk, is a typical wheat – milk mixture fermented food popular in Egypt and most of the Arab World. It consists of small, round or irregular pieces, yellowish brown in colour, which have a rough surface and hard texture. When moistened with water, it becomes white and breaks up after a short time.

Kishk is rich in nutritive constituents, and is a possible source of many vitamins and growth factors associated with the microbial fermentative processes. It is of good keeping quality and consumed throughout the year.

32.2.1 Micro flora in kishk

Kishk is naturally fermented product and aerobic spore formers like B. subtilis and B.megaterium are high in numbers in initial stage, but inhibited later on due to high acid.

The most predominat microflora, which are responsible for fermentation are lactic acid bacteria. Among LAB, homo and heterofermentative lactobacilli, mainly Lb. plantarum, Lb.casei and Lb. brevis are predominate bacteria.

During the later stage of fermentation, yeasts develop, which produce gas and improve porosity and also enrich product with vitamins.

32.2.2 Manufacture of kishk

Kishk preparation involves three main stages.

32.2.2.1 Preparation of Par-boiled wheat

Wheat grains, are placed in large cooking pan, covered with water and heated slowly to boiling and simmered until soft. The cooked wheat or helila is then washed with cold water, spread on straw mats and left to dry in air. The dry material which is hard in texture is coarsely ground in stone mills, then sieved and seed coats are removed.

32.2.2.2 Preparation of Laban Zeer

Laban-zeer is sour coagulated milk. Traditionally, the milk was churned in skin bag and left out fluid is called as sour milk. In hot weather, milk coagulates spontaneously and is then often considered unsuitable for cheese making. Such sour milk is stored in earthenware containers known as zeer. A suitable quantity of salt judged by taste is added and the contents of the zeer are mixed. The whey oozes through the walls and thus consistency of sour milk becomes considerably thicker. Accumulated laban zeer is especially used in summer, when wheat are plentiful in the farmers store for making kishk.

The most dominant microflora of laban zeer compose of Lb. casei, Lb. plantarum and Lb. brevis.

32.2.2.3 Preparation of hamma (kishk mix)

The coarser power of the par boiled wheat is placed in large pots and moistened with slightly salted boiling water. Then raw milk or laban zeer diluted with water is added and thoroughly mixed to obtain a homogenous paste, called hamma.

After 24h, the hamma, which has meanwhile increased in volume as a result of fermentation, is kneaded by hand. Later on Laban zeer, twice the volume added before is diluted with water or milk with syrupy consistency, is added in portions to the hamma and left for a further 24h. Subsequently, the fermented mix is thoroughly remixed, cut in small balls and placed on straw mats to dry in the open. The dried product is kishk. Sometimes spices like cumin or pepper are added for enhancing taste. Complete drying of product takes 5-7 days and during this period also fermentation goes on gradually at reducing rates.

32.2.3 Advantages of kishk fermentation

1. Outlet for surplus milk

2. Higher protein content (average 23%)

3. Contains fair amounts of iron, phosphorous and calcium.

4. Contains higher amounts of (i) phenylalanine (ii) threonine (iii) isoleucine (iv) leucine (v) arginine (vi) valine (vii) tyrosine (viii) lysine; while low amount of tryptophane & sulphur containing amino acids.

5. Net protein utilization is comparable with casein ( 60 for casein, 59 for Kishk)

6. Has higher digestibility.

7. The milk protein makes up for the amino acid deficiency of most of the cereal product.

8. About 50 g of Kishk, would meet the daily requirement of lysine for a man of average 60 kg body weight.

9. Milk and cereals would supplement each other with vitamins and salts.

10. Wheat is relatively good source of iron while milk is deficient in iron. The complementary effect makes the product nutritionally sound.

11. Excellent shelf-life of more than one year at room temperature.

12. Convenient to use. It can be taken as breakfast food along with milk or used for preparation of vegetable curries for lunch or dinner.

32.3 Yakult

Yakult is a probiotic fermented milk product which originated from Japan almost 70 years before. It is made with the help of a culture of Lactobacillus casei strain Shirota, which is named after the inventor Prof. Minoru Shirota. The product is most widely studied for clinical benefits and it is claimed that the product aids digestion, modulates immunity and prevents infection.

Yakult is originally made from skim milk & sweetener agents like sucrose, glucose, liquid sugar & starch syrup. It may contain fruit juices & flavouring essences.

The average composition of yakult is given below:

Fat 1.1 %

Protein 1.2 %

Lactose 1.1 %

Other Sugar 14.1 %

Ash 0.34 %

It has a junket like consistency. Colour is slightly brown, which indicates that the milk / sugar base may be highly heat treated. Now it is available in different flavours blended with different fruits juices. The product is proprietary item of M/s Yakut Hansa Ltd. in Japan and is being consumed now by 25 million people every day in 31 countries across the world as per company’s claim. The company is now producing Yakult in India also. Yakult is available in 65 ml bottle, which contains 6.5 billion live cells of Lactobacillus casei strain Shirota.

The main reasons for the popularity of Yakult in Japan are

i. It psychologically, meets the desire of people to be healthy and it is now scientifically confirmed also.

ii. It suits the taste of most Japanese people.

iii. It is readily acceptable in every day diet.

iv. It has a reasonable price.

32.4 Villi

Villi is a traditional Finnish fermented milk product made from pastuerized unhomogenized milk with capsule or slime forming starters that have adapted to grow at lower temperature than the ambient temp., viz. 18 - 19°C.

32.4.1 Starters for villi

Lactic streptococci – Lactococcus lactis subsp lactis, L. lactis subsp cremoris

Mold – Geotrichum candidum

Because villi is made from unhomogenized milk, the cream rises up to the top in the cup during fermentation and this mold grows on its, so there is a uniform velvet like layer is seen when the cup is opened for eating.

Geotricum candidum has different metabolic activity and is symbiotic with lactic streptococci. It assimilates glucose and galactose but not lactose and sucrose, while assimilating sugars in villi, the mold consumes oxygen from air space of air tight cup and produce CO₂. When all O₂ is consumed its growth is restricted. So much CO₂ is produced by mold that it is partially dissolved in the milk to form carbonic acid and carbonates, and as a consequence of it, slight under pressure is generated in the cup. The mold also shows lipolytic activity, while growing on the surface layer, the concentration of monoglycerides and free fatty acids increases and gives typical flavor to the product.

32.4.2 Other fermented milk products

        - Fermented beverages

        - Fermented dietetic preparation

        - Fermented milk ingredients in food.

· Soups & Sauces

· Confectionary

· Sweets

· Chocolate

· Bakery products

· Cereal products

· Liqueur

· Spreads

· Meat products