Yogurt(suan nai )

Yogurt method:

Raw materials for making yogurt:

Fresh milk, sugar.

Yogurt making steps:

The fresh milk without antibiotics and preservatives should be selected. The fat content should not be higher than 3%, dry matter should be higher than 8.5%, and acidity should be lower than 0.16. Add sugar according to 5% - 10% of fresh milk, boil for 3 minutes and then filter. Then the filtered milk was quickly cooled to 38-42 degrees, and lactic acid bacteria were inoculated under aseptic condition to make the bacteria evenly distributed. The inoculated milk is separately packed in the washed and sterilized milk bottles, sealed in time, and fermented at 37 ℃ for 4-6 hours. After fermentation, the acidity and coagulation should be checked at any time. When the acidity is 0.58 and the coagulation also meets the requirements, stop the fermentation, carefully take it out, cool it at room temperature, and then move it to the refrigerator of 2-6 degrees for cooling.

Yogurt

Yogurt is a kind of milk drink with sweet and sour taste. It is a kind of milk product with milk as raw material, pasteurized and then added with beneficial bacteria (starter), fermented and then cooled. Yogurt products in the market are mostly solidified, stirred and fruit flavored with various fruit juices and jams.

Historical evolution

Historical evidence shows that yoghurt has been used as food for at least 4500 years. The earliest yoghurt may be that the milk in the sheepskin bag of nomadic people was naturally fermented by bacteria attached to the bag and became cheese.

More than 2000 BC, the ancient Thracians living in northeast Greece and Bulgaria also mastered the production technology of yogurt. They also used goat's milk at first. Later, yogurt technology was spread to other parts of Europe by the ancient Greeks.

According to the Turkic dictionary written by Mahmoud Kashkari in the 11th century and the wisdom of happiness written by Yusuf Hass hajifu, the Turks were eating yogurt in the middle ages. Both books refer to the word yogurt in different aspects, and record in detail how nomadic Turks used yoghurt. The first record of yogurt in Europe originated from the clinical history of France: Francis I suffered from a serious dysentery, and the French doctors at that time were at a loss. The ally's Suleiman I sent him a doctor, who claimed that he had cured the patient with yogurt.

In fact, from the perspective of linguistics, according to the etymological study of yoghurt, yoghurt came into English vocabulary from Turkish language. Today, yogurt is still used in Turkey. Reference: New Oxford Dictionary, Turkic dictionary, entry: yogurt

It was not until the 20th century that yogurt gradually became a food material in South Asia, Central Asia, West Asia, Southeast Europe and central Europe.

Production method

Production process

The production process of yoghurt can be summarized as batching, preheating, homogenization, sterilization, cooling, inoculation, (filling: used for solidified yoghurt), fermentation, cooling, (stirring: used for stirred yoghurt), packaging and post ripening

Ingredients: according to the material balance table, select the required raw materials, such as fresh milk, sugar and stabilizer. Denatured starch can be added alone or mixed with other food gums. Considering that most of starch and food gum are high molecular materials with strong hydrophilicity, it is best to mix with appropriate amount of granulated sugar and dissolve them in hot milk (55 ℃ ~ 65 ℃) under high-speed stirring state to improve their dispersibility.

Preheat: the purpose of preheat is to improve the efficiency of the next process homogenization. The preheat temperature should not be higher than the gelatinization temperature of starch (to avoid the destruction of granule structure in the process of homogenization after starch gelatinization).

Homogenization: homogenization refers to the mechanical treatment of milk fat globules so that they are uniformly dispersed in the milk as smaller fat globules. In the homogenization stage, the material is subjected to shear, collision and cavitation forces. Due to the cross-linking modification, modified starch has strong mechanical shear resistance, and can maintain the complete particle structure, which is conducive to maintaining the viscosity and body state of yogurt.

Sterilization: pasteurization is generally used, and the sterilization process of 95 ℃ and 300s is generally used in dairy factories. At this stage, the modified starch is fully expanded and gelatinized to form viscosity.

Cooling, inoculation and fermentation: modified starch is a kind of high molecular material, which still retains part of the properties of original starch, that is, the properties of polysaccharide. In the pH environment of yogurt, starch will not be degraded by bacteria, so it can maintain the stability of the system. When the pH value of the fermentation system dropped to the isoelectric point of casein, casein denatured and solidified, forming a three-dimensional network system of casein micelles connected with water, and the skeleton became curdled. At this time, the gelatinized starch could fill the skeleton, bound free water, and maintained the stability of the system.

Cooling, stirring and post ripening: the purpose of stirring yogurt cooling is to quickly inhibit the growth of microorganisms and enzyme activity, mainly to prevent excessive acid production during fermentation and dehydration during stirring. Due to more sources of raw materials and different degrees of denaturation, different modified starches have different effects in yogurt production. Therefore, the modified starch can be provided according to the different requirements of yogurt quality.

The instruments and materials for making yoghurt

Sterilization equipment, fermentation tank or fermentation room, heating tank, ultraviolet lamp, glass bottle or porcelain bottle or special paper basin, fresh milk, sugar, lactic acid bacteria (bulgaricus and Streptococcus thermophilus), etc.

Production steps

Sterilization of glass bottles, etc. Sterilize the glass bottle in the sterilizer for half an hour, sterilize it in the steamer for 45 minutes, sterilize it in the inoculation room for 50 minutes, and sterilize the inoculation tools in the high-pressure steam sterilizer for 30 minutes.

Milk is sterilized. Put the fresh milk into the heating jar, add 10-12% sugar, and sterilize at 85-90 ℃ for 30 minutes or by other methods. No matter which method is used, it is better not to destroy the original nutrients of milk, and it should be cooled after sterilization. Before or during sterilization, it is better to remove the upper layer of grease to defat the milk.

Vaccination. The sterilized milk with the temperature lower than 43 ℃ is separately packed in the sterilized glass bottle. The milk is inoculated in the inoculation room according to the inoculation amount of 2% - 4% and stirred evenly. Pay attention to the full filling of the tank without leaving any gap, and seal immediately after connecting, so as to ensure the anaerobic condition of lactic acid fermentation. After soaking in warm water (below 43 ℃) for 8-10 hours, it can be put on the market after refrigerated in 0-5 ℃. After ripening yoghurt has special aromatic smell because of ester. On the one hand, cold storage can prevent the increase of acidity and the pollution of miscellaneous bacteria, on the other hand, it can make the texture firm and the whey recycled, thus greatly improving the stability of yogurt quality. During the whole process, attention should be paid to aseptic operation. The staff should wear aseptic work clothes, gloves and masks, clean their hands, and do not inoculate without masks to prevent contamination by miscellaneous bacteria.

Quality standard. The appearance of high-quality yoghurt is milky white or slightly yellow, the surface is smooth, the curd is firm, the organization is fine, the texture is uniform, a small amount of whey is allowed to precipitate, no bubbles, moderate sour and sweet, no pungent and other peculiar smell. If there are bubbles or bulging caps in yoghurt, or there are pungent and other odors, it means that the fresh milk has been contaminated by miscellaneous bacteria in the fermentation process and can not be eaten. If the above situation occurs in the production of seed (starter), it must not be used in production to prevent unnecessary losses. If the time-out occurs under suitable temperature, there is little milk coagulation, whey separation, or even no milk coagulation, and a large number of suspended solids and odor appear, which indicates that the strain is seriously declining or has been contaminated by miscellaneous bacteria, so it should be stopped. If the strain declines, the declining strain can be cultured on the inclined plane medium, purified and rejuvenated, and then propagated to obtain excellent production species

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Nutrients

Every 100 grams of yogurt contains 99 calories. The specific nutrient contents are shown in the table below:

Classification of yogurt

According to the national standard, yogurt can be divided into four categories: yogurt, fermented milk, flavor yogurt and flavor fermented milk.

Yoghurt

The product is made from raw milk or milk powder of cattle (sheep) by sterilization, inoculation of Streptococcus thermophilus and fermentation of Lactobacillus bulgaricus (Lactobacillus delbrueckii subsp. Bulgaricus).

Fermented milk

The product with lower pH value made from raw milk or milk powder after sterilization and fermentation has no limitation of bacteria.

flavored yoghurt

In addition to milk / milk powder, yogurt also contains other ingredients, such as food additives, fruits and vegetables or cereals. As long as the milk / milk powder content is more than 80% and the protein content is more than or equal to 2.3%.

Chinese PinYin : Suan Nai