Laboratory work №8 Studying of technology of preparation of sour-milk ferments.

Work purpose: To get acquainted with technology of preparation of sour-milk ferments. To study a bottle way of receiving ferments of true cultures.

Task 1. To define how many production ferment is necessary for preparation 500 kg of kefir.

Task 2.To prepare production ferment for preparation of kefir.

Short theoretical data

To cause lactic fermentation by production of fermented milk products, kisloslivochny oil and cheese, apply true bacterial cultures. Bacterial cultures usually produce in a look dry and liquid (seldom), kotoryesokhranyayutsyado10-14 days on cold, an expiration date of dry cultures – more 2-hmesyaets. At the plant, as well as in laboratory, prepare maternal (the main, initial or primary), transfer (secondary) and production (worker) ferment. All stock has to be sterile.

Equipment, devices and technical means:

the thermostat, pans, the electric stove, scales with weights, glasses, circles of parchment, ferment dry.

Work performance order

Technology of preparation of sour-milk ferments

Maternal ferment.

1. Milk to proseparirovat and receive about 2 l of skim milk (to remove foam with a pure spoon).

2. To pour in milk in a flask, to close a wadded stopper, to propasterizovat in water at 90-95 °C within 30 min.

3. In the same ware to cool milk to 30 °C (in cold water). Temperature of milk is taken the thermometer without wooden frame. At preparation of ferment for acidophilus milk to cool up to 45 °C.

4. The film formed on the surface of milk is removed a sterile metal spoon.

5. To pour dry or to pour in liquid laboratory culture in milk, at the same time mixing it a verticil. Contents of a flask are mixed roundabouts.

6. To close ware a gauze or parchment and to put in the thermostat or in a vessel with water, where to maintain temperature 28-30os. The culture for acidophilus milk and yogurt is maintained at 40-45 °C. If milk was fermented in a flask, then it should be placed in the thermostat.

7. The first three hours to mix milk in each hour, then to cover capacity with a gauze. Final souring occurs cherez12-18ch.

Maternal ferment is stored at a temperature of 10 °C. Her clot has to be quite dense, acidity – 65-70 °Т. Taste and aroma pure, accurately expressed.

Transfer (secondary ferment)

1. To prepare skim milk also, as well as for maternal ferment (to pasteurize, remove foam, okhladitdo25-27 with °C). At preparation of ferment for acidophilus milk and yogurt temperature of milk has to be 40-45 °C.

2. To skim with maternal ferments a sterile spoon (2-3rd). To stir the remained clot a verticil to a smetanoobrazny state. To shake up contents of a flask.

3. To bring a pure beaker or the cylinder in prepared fat-free moloko2-3 by % of maternal ferment.

4. Folding of transfer (secondary) ferment comes in 8-14 h. Ferment has to have pleasant taste and aroma, acidity within 90-100 °. It is necessary to store this ferment at a temperature of 10 °. In maternal and transfer ferments of a bacterium are still insufficiently active therefore the third change is necessary for receiving working (polzovatelny) ferment.

Working ferment is prepared similarly transfer, it is only necessary to reduce souring temperature to 20-24 °C, for acidophilus milk till 38-40 °. These ferments are usually ready in 6-10 h. Ready working ferment has to have sour-milk true taste and a smell, a uniform consistence, to be without vials of gas and foreign smacks and smells. Apply a so-called two-row way to respect for purity. From the main ferment at the same time train the main and working again. Working ferment every time ferment new the main. At such way remain more long time of property of the main ferment, and working ferment turns out quality.

Bottle way of receiving ferments of true cultures.

The ferment received from laboratory is brought in the prepared milk which is spilled in seven sterile bottles. Bottles with skvashenny milk store in the refrigerator. The next day from the first bottle prepare secondary culture. For the third day from the secondary culture which was in the first bottle prepare working ferment and on the same day from the second bottle prepare secondary culture. For the fourth day working ferment is received from secondary culture of the second bottle, and from the third bottle - secondary culture the next day. Act daily this way, receiving working ferment for the present day and preparing culture on following.

In all cases of emergence in ferments of defects (a flabby clot, foreign smack, the slowed-down folding) from laboratory culture prepare maternal and the subsequent ferments again.

The worker and parallel ferments is stored at 8-10 °C no more than two days. Through each 10-12 changes ferment is changed. Some feature is represented by kefiric fungi. Microflora of kefiric fungi consists of a symbiotic combination of lactic streptococci and sticks, the aromatobrazuyushchikh of bacteria, milk yeast, microtherms (filmy yeast) and acetic bacteria. Kefiric grains serve as maternal ferment from which the subsequent receive all for production of kefir. Technical progress of poseshas allowed to receive continuously fungal ferment and to create the automated product line on production of kefir. Advantage of this method is that favorable conditions for development of all components of microflora of kefiric ferment (lactic streptococci, sticks, yeast) are created.

Control questions:

1. What types of ferments you know?

2. Give the characteristic of working ferment?

3. Characterize a bottle way of receiving ferments.