Defects In Sour-Milk Production

Defect   
Causes
Measures of prevention

Fluid consistence with a serum sediments

Use of milk with a density less than 1027 kg/m3 for all dairy drinks and less than 1028 kg/m3 for kefir

To carry out careful selection of raw materials of the recommended density. In autumn-winter period in connection with decrease of maintenance of a casein in milk it is recommended to develop, especially kefir, with addition of powdered milk

 

The poor mode of thermal treatment of initial milk as a result of which the denaturation of serumal proteins is not observed

To apply the following modes of pasteurization for dairy drinks: 85 — 87 °C with endurance of 5 — 10 min.; 92 — 95 °C with exposure 2 — 8 Mia. At these modes there is an aggregation of almost completely denatured particles of serumal proteins which form the dense clot during souring milk coagulate together with a casein, and which delays separation of serum. The denatured serumal proteins are directly involved in formation of a three-dimensional reticulate structure of a clot

 

Lack of homogenization of milk

At a dispersion (refinement) of fat balls their surface increases and on it bathotonic fractions of proteins of plasma are adsorbed that leads to violation of a dynamic equilibrium in which there was originally a proteinaceous complex. And it causes an autodecomposition of proteinaceous particles, that is their refinement promoting the best coagulation when souring and to formation of the dense clot.

It is necessary to keep the homogenization modes: pressure is 12,5 — 17,5 MPas and temperature is 45 — 48 °C

 

Non-compliance with the modes of hashing

 

Hashing of kefir at acidity 85 °Т leads to a serum sedimentation, and at 95 — 100 °Т promotes receiving a product with rather viscid consistence. It is bound to increase in water-retaining power of a casein. Duration of hashing depends on a design of a mixer and durability of a clot. If the clot is weak (especially for kefir), then it is recommended to carry out maturing at 20 °C. At this temperature there is repeated structurization, number of contacts between macromolecules increases

 

Transferring a clot on pouring by means of pumps.

Pumps should have a rotation frequency of 100 — 200 rpm. The flow of kefir through pipes has to be laminar with a speed no more than 0,6 m/s, and moving speed in the pump is not higher than 0,01 m/s o

Flocculent consistence

Low heat stability of proteins of milk

To check with use of alcoholic tests.

 

Local coagulation of proteins at interaction of starter with the first portions and the milk fed into the tank with the starter inside

The first portions of the milk fed into the tank with starter should have temperature lower than temperature of souring on 5 — 7 "C. The first portions of milk having temperature of 35 — 50 °C can also cause local coagulation of proteins of milk and promote formation of a flocculent, grainy consistence in a finished stock.

Nonspecific sour milk smack for kefir

 

Underdevelopment of yeast, aroma forming and acetic bacteria

To reduce temperature of cultivation of kefiric fungi, to reduce their quantity; to exclude washing of kefiric fungi

Too fast souring of kefir and the its increased acidity

Lack of standard heating environments for process of souring of kefir at which thermophilic lactic bacteria intensively develop

It is necessary to establish temperature of souring, equal 18 — 25 °C, to reduce amount of starter to 1 — 2%

Availability of bacteria of group of colibacillus

Violation of sanitary hygienic conditions of production

To systematically conduct microbiological researches of raw materials, starters and an inventory on the course of technological process. The main source of colibacillus — starter if the modes of its preparation are broken. Often dairy drinks are inseminated by these bacteria in liquid-filling and corking automatic machines