STARTER CULTURES AND FERMENTED MILK PRODUCTS

Module 14. Cultured butter milk

Lesson 24
PREPARATION OF CULTURED BUTTER MILK, COMPOSITION AND QUALITY CHARACTERISTICS

24.1 Introduction

Drinking of butter after churning dahi in to country butter is a very common habit in India. This product has most of the fermented milk solids except fat which goes in butter.It also has mixed lactic acid bacteria, especially Lactococci and Leucostocs,which gives it a typical diacetyl flavour.

Manufacturing cultured butter milk on industrial scale involve selection of good quality raw material,standard cultures and optimized process of fermentation, packaging and storage.

True buttermilk is the fluid remaining after cream is churned into butter. If butter is made from sweet cream, its buttermilk has approximately the same composition as skim milk. Cultured butter milk is prepared by souring true butter milk or more commonly, skim milk with a butter starter culture that produces a desirable flavor and aroma.

24.2 Starter Culture

Cultured butter milk is prepared with the help of normal mesophilic lactic acid bacteria.

There should be satisfactory balance between acid and flavor producers in the starter.

24.3 Making of Cultured Butter Milk

The typical process flow diagram for preparation of culture butter milk is shown in Figure 1.

Each step in the process has significance on the technological, microbiological and sensory qualities of the product.

24.4 Selection of Milk

The quality of raw material decides the quality of final product. The raw milk selected for CBM manufacture should normal composition, be free from off flavor and odours and free from inhibitory substances. It should have lower microbial count.

Fig. 24.1 Flow diagram for preparation of cultured butter milk

24.5 Standardization of Milk

It is usual practice to standardize milk for fat and solids-not-fat content looking to legal requirements and also as per consumer demands. Generally skim milk is the starting material and it may be added with approximately 1.7% fat. In certain commercial processes, fat is added as granules in cold fermented butter milk.Sodium chloride at the rate of 0.1 – 0.2% and sodium citrate at the rate of 0.1 – 0.2% may be added for enhancement offlavor.

24.6 Heat Treatment

Proper heat treatment of at least pasteurization equivalence is mandatory for CBM production. This is to ensure destruction of pathogens and make the product safe for human consumption. It also helps in proving suitable environment for the cultures. Based on earlier experiences and scientific evidences, it found that heating at 85° for 30 min is the optimum heat treatment for CMP production which gives best quality product in terms of flavour and shelf-life. Heating below 82°C or above 88°C causes a weak body, that allows whey separation in cultured butter milk.

24.7 Cooling

Milk must be cooled down to inoculation temperature as soon as holding period is over. Inoculation in hot milk will destroy the culture. It should be 22-25°C for cultured buttermilk.

24.8 Inoculation

The milk should be inoculated with appropriate mesophilic starter culture just after cooling. Inoculation rate varies from 0.5 to 2.0%, depending upon the starter activity and time of incubation At the time of inoculation,starter should have 0.80-0.85% acidity. Over ripe culture are not suitable as the lactic streptococci have passed their peak of acidity. If it is under ripenedi.e. less than 0.8% lactic acid, it will not have sufficient number of aroma bacteria.

24.9 Incubation

The typical incubation temperature for CBM is 21.6°C. There are several reasons for selecting 21-22°C as incubation temperature.

• Any departure of more than a degree or two above or below will cause imbalance in the bacterial mixture and will adversely affect the product.
• At lower temperature, the starter organisms grow too slowly, and curdling is delayed excessively
• At much higher temperature, the streptococci overgrow aroma bacteria and product lack flavor and aroma.
• At higher incubation temperature the curd forms at a lower acidity and it tends to shrink, causing whey separation.
• Use of lowest practicable temperature inhibits the growth of undesirable bacteria that survive the heat treatment given to the milk.

24.10 Cooling, Agitation and Dilution

After desired stage of ripening, the curd must be cooled rapidly to avoid over ripening. Mixing may be necessary to hasten cooling, but it should not be done in a manner that incorporate air. Excessive agitation decreases the stability of butter milk and increases whey separation. Gentle agitation is required to break curd and to have efficient and quick cooling. At the stage dilution of the product may also may be done to adjust solids level to desired level. Some manufacturers also add some spices and condiments to falvour it . The final cooling of the product should be to less than 5°C.

24.11 Packaging & Storage

Bottle or cartons packaging material are commonly used. Packaging material should not excessively increase the microbial load in the product. Product will have better shelf-life if stored below 5°C.

24.12 Composition of Cultured Butter Milk

The normal composition of cultured butter milk is given in Table 2.

Table 24.2 Composition of cultured butter milk

24.13 Characteristics of Good Quality Cultured Butter Milk

A good quality butter milk, after packaging has a pH 4.5 and a possess smooth viscous body giving a slow even flow when poured. The flavor should be clean acid with an integrated aromatic diacetyl and free volatile acid background. It exhibits no free whey or whey separation. The keeping quality of good buttermilk at 5°C is approximately 2 weeks

The standards for quality and hygiene apply to butter milk too. In India the standards for contamination prescribe that coli form count should be less than 10 per ml and yeast & mold count should be less than 100 per ml.