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Microflora of feed and food products

Completed by a 2nd year student

Tutunar Denis

Feed microflora

Epiphytic microflora. On the surface parts of plants, a diverse microflora, called epiphytic, is constantly present. On stems, leaves, flowers, fruits, the following non-spore types of microorganisms are most often found: Bact, herbicola makes up 40% of all epiphytic microflora, Ps. fluorescens - 40%, lactic acid bacteria - 10%, the like - 2%, yeast, mold fungi, cellulose, butyric, thermophilic bacteria - 8%.

After mowing and loss of resistance of plants, as well as due to mechanical damage to their tissues, the epiphytic and, above all, putrefactive microflora, multiplying intensively, penetrates into the thickness of plant tissues and causes their decomposition. That is why crop products (grain, coarse and succulent fodder) are protected from the destructive action of epiphytic microflora by various conservation methods.

It is known that in plants there is bound water, which is part of their chemical substances, and free - drip-liquid. Microorganisms can multiply in the plant mass only in the presence of free water in it. One of the most common and accessible methods for removing free water from crop products and, consequently, their conservation is drying and ensiling.

Drying grain and hay involves removing free water from them. Therefore, microorganisms cannot multiply on them as long as these products are dry.

In freshly cut, unripened grass, water contains 70-80%, in dried hay only 12-16%, the remaining moisture is in a bound state with organic substances and microorganisms is not used. During the drying of hay, about 10% of organic matter is lost, mainly during the decomposition of proteins and sugars. Particularly large losses of nutrients, vitamins and mineral compounds occur in dried hay in swaths (rolls) when it often rains. Rain distilled water washes them up to 50%. Significant losses of dry matter occur in the grain during its self-heating. This process is due to thermogenesis, that is, the creation of heat by microorganisms. It arises because thermophilic bacteria use for their life only 5-10% of the energy of the nutrients they consume, and the rest is released into their environment - grain, hay.

Ensiling fodder. When growing fodder crops (corn, sorghum, etc.) from one hectare, it is possible to obtain much more fodder units in green mass than in grain. According to the starch equivalent, the nutritional value of green mass during drying can decrease up to 50%, and during ensiling only up to 20%. When ensiling, small leaves of plants with high nutritional value are not lost, and when dried, they fall off. The silo can be laid even in variable weather. Good silage is a juicy, vitamin, milk-producing feed.

The essence of ensiling lies in the fact that in the crushed green mass laid in the container, lactic acid microbes intensively multiply, decomposing sugars with the formation of lactic acid, which accumulates up to 1.5--2.5% by weight of the silage. At the same time, acetic acid bacteria multiply, converting alcohol and other carbohydrates into acetic acid; it accumulates 0.4--0.6% by weight of the silo. Lactic and acetic acids are a strong poison for putrefactive microbes, so their reproduction stops.

Silage is kept in good condition for up to three years, as long as it contains at least 2% lactic and acetic acids, and the pH is 4--4.2. If the reproduction of lactic acid and acetic bacteria weakens, then the concentration of acids decreases. At this time, yeast, mold, butyric and putrefactive bacteria simultaneously begin to multiply and the silage deteriorates. Thus, obtaining good silage depends primarily on the presence of sucrose in the green mass and the intensity of the development of lactic acid bacteria.

In the process of silage maturation, three microbiological phases are distinguished, characterized by a specific species composition of the microflora.

The first phase is characterized by the reproduction of mixed microflora with a certain predominance of putrefactive aerobic non-spore bacteria - Escherichia coli, Pseudomonas, lactic acid microbes, yeast. Sporiferous putrefactive and butyric bacteria multiply slowly and do not predominate over lactic acid bacteria. The main environment for the development of mixed microflora at this stage is plant sap, which is released from plant tissues and fills the space between the crushed plant mass. This contributes to the creation of anaerobic conditions in the silage, which inhibits the development of putrefactive bacteria and favors the reproduction of lactic acid microbes. The first phase with dense laying of silage, that is, under anaerobic conditions, lasts only 1--3 days, with loose laying under aerobic conditions, it is longer and lasts 1--2 weeks. During this time, the silo is heated up due to intensive aerobic microbiological processes. The second phase of silage maturation is characterized by the rapid reproduction of lactic acid microbes, and at first predominantly coccal forms develop, which are then replaced by lactic acid bacteria.

Due to the accumulation of lactic acid, the development of all putrefactive and butyric microorganisms stops, while their vegetative forms die, leaving only spore-bearing ones (in the form of spores). With full observance of the technology of laying silage in this phase, homofermentative lactic acid bacteria multiply, forming only lactic acid from sugars. In case of violation of the silo laying technology, when in it. air is contained, the microflora of heterofermentative fermentation develops, as a result of which undesirable volatile acids are formed - butyric, acetic, etc. The duration of the second phase is from two weeks to three months.

The third phase is characterized by the gradual death of lactic acid microbes in the silage due to the high concentration of lactic acid (2.5%). At this time, the maturation of the silage is completed, the acidity of the silage mass, which decreases to pH 4.2 - 4.5, is considered a conditional indicator of its suitability for feeding (Fig. 37). Under aerobic conditions, molds and yeasts begin to multiply, which break down lactic acid, butyric and putrefactive bacteria germinating from spores take advantage of this, as a result, the silage becomes moldy and rots.

Silage defects of microbial origin. If the proper conditions for laying and storing the silo are not observed, certain defects occur in it.

Silage rotting, accompanied by significant self-heating, is noted with its loose laying and insufficient compaction. The rapid development of putrefactive and thermophilic microbes is facilitated by the air in the silo. As a result of protein decomposition, silage acquires a putrid, ammoniacal smell and becomes unsuitable for feeding. Silage rotting occurs in the first microbiological phase, when the development of lactic acid microbes and the accumulation of lactic acid, which suppresses putrefactive bacteria, is delayed. To stop the development of the latter, it is necessary to reduce the pH in the silage to 4.2-4.5. Silage rotting is caused by Er. herbicola, E. coli, Ps. aerogenes. P. vulgaris, B. subtilis, Ps. fluorescens, as well as fungi.

Rancidity of silage is due to the accumulation of butyric acid in it, which has a sharp bitter taste and an unpleasant odor. Butyric acid is absent in good silage, up to 0.2% in medium-quality silage, and up to 1% in unsuitable for feeding silage.

The causative agents of butyric fermentation are capable of converting lactic into butyric acid, as well as causing putrefactive decomposition of proteins, which aggravates their negative effect on the quality of silage. Butyric fermentation is manifested by the slow development of lactic acid bacteria and insufficient accumulation of lactic acid, at a pH above 4.7. With the rapid accumulation of lactic acid in the silage up to 2% and pH 4--4.2, butyric fermentation does not occur.

The main causative agents of butyric fermentation in silage: Ps. fluo-rescens, Cl. pasteurianum, Cl. felsineum.

Peroxidation of silage is observed with the vigorous reproduction of acetic acid, as well as putrefactive bacteria in it, capable of producing acetic acid. Acetic acid bacteria multiply especially intensively in the presence of ethyl alcohol in the silage, which is accumulated by alcoholic fermentation yeast. Yeast and acetic acid bacteria are aerobes, therefore a significant content of acetic acid in the silage and, consequently, its peroxidation is noted in the presence of air in the silo.

Molding of the silage occurs when there is air in the silo, which favors the intensive development of molds and yeasts. These microorganisms are always found on plants, therefore, under favorable conditions, their rapid reproduction begins.

The rhizospheric and epiphytic microflora can also play a negative role. Root crops are often affected by rot (black - Alternaria radicina, gray - Botrutus cinirea, potato - Phitophtora infenstans). Excessive activity of causative agents of butyric fermentation leads to spoilage of silage. Ergot (claviceps purpurae), which causes the disease ergotism, reproduces on vegetative plants. Mushrooms cause toxicosis. The causative agent of botulism (Cl. botulinum), getting into the feed with soil and faeces, causes severe toxicosis, often fatal. Many fungi (Aspergillus, Penicillum, Mucor, Fusarium, Stachybotrus) populate food, multiply under favorable conditions, and cause acute or chronic toxicosis in animals, often accompanied by nonspecific symptoms.

Microbiological preparations used in the diets of animals and birds. Enzymes improve the absorption of feed. Vitamins and amino acids are obtained on a microbiological basis. It is possible to use a bacterial protein. Feed yeast is a good protein-vitamin feed. Yeast contains easily digestible protein, provitamin D (pro-gosterol), as well as vitamins A, B, E. Yeast reproduces very quickly, therefore, under industrial conditions, it is possible to obtain a large amount of yeast mass when cultivating them on molasses or saccharified fiber. At present, in our country, dry fodder yeast is prepared in large quantities. For their manufacture, a fodder yeast culture is used.

Microflora of food products during refrigerated storage

The microflora of raw food products of plant and animal origin is very diverse. Microorganisms that make up the microflora of products include bacteria, yeasts, molds, protozoa (protozoa) and some algae. Microorganisms are widespread in nature due to their easy adaptability to heat, cold, lack of moisture, as well as due to their high resistance and rapid reproduction. silo microbial microflora mold

The development of microbiological processes in food products can lead to a decrease in nutritional value and drastically worsen the organoleptic characteristics of food products, causing the formation of substances harmful to products. Therefore, one of the tasks of the food industry is to limit the harmful effects of microorganisms on products. However, there are certain micro-organisms whose presence in foods gives them new flavors. The method of replacing unwanted microflora with microflora with the required properties is used in the production of kefir, curdled milk, acidophilus, cheeses, sauerkraut, etc.

For the development of microorganisms, the presence of water in a form accessible to them is necessary. The need of microorganisms for water can be expressed quantitatively in the form of water activity, which depends on the concentration of dissolved substances and the degree of their dissociation.

The development of microflora with a decrease in temperature is sharply inhibited, and the more, the closer the temperature is to the freezing point of the tissue fluid of the product. The effect of lowering the temperature on the microbial cell is due to the violation of the complex relationship of metabolic reactions as a result of different levels of changes in their rates and damage to the molecular mechanism of the active transfer of soluble substances through the cell membrane. Along with this, there is a change in the qualitative composition of microorganisms. Some groups of them also reproduce at low temperatures, causing infection of fruits and vegetables injured during harvesting and transportation. The infection then spreads to healthy, undamaged fruits and vegetables.

In relation to temperature, all microorganisms are divided into three groups: THERMOPHILES (55-75 o C); MESOPHILES (25-37 o C); PSYCHROPHILES (0-15 o C).

For refrigeration technology, psychrophilic microorganisms in food products are of great importance. They are found in soil, water, air, having the ability to seed technological equipment, tools, containers, directly food products. They actively breed on foods with low acidity - meat, fish, milk and vegetables.

Freezing food is accompanied by a decrease in the number of microorganisms and their activity. In the initial period of freezing, when most of the water turns into ice, there is a sharp decrease in the number of microorganism cells (zone A). This is followed by a slowdown in the reproduction of microorganisms (zone B). Then the process stabilizes, and a certain amount of resistant microorganism cells remain (zone C).

The death of microorganisms during freezing with the greatest intensity occurs at temperatures from -5 to -10 o C. A number of yeasts and mold fungi are capable of vital processes up to a temperature of -10 - -12 o C.

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1 area of use

This standard applies to feed, compound feed, compound feed raw materials and is a general guideline for the preparation of dilutions to detect the presence (absence) or determine the number of aerobic microorganisms (currently, the guide should be used in combination with the methods described in the "Rules for the bacteriological examination of feed") .

Mandatory requirements for the procedure for conducting dilutions are set out in section 9.

2 Normative references

GOST 13496.0-80 * Compound feed, raw materials. Sampling methods
_______________
* Valid until the entry into force of GOST R, developed on the basis of ISO 6497.

GOST R 51419-99 (ISO 6498-98) Feed, feed, mixed feed raw materials. Sample preparation

3 Definitions

For the purposes of this International Standard, the following terms apply with their respective definitions:

original suspension (primary dilution): Suspension, solution or emulsion, obtained after a weighed or measured amount of the test product has been mixed, if necessary, using a mixer and following the appropriate precautions (see note to 9) with nine times the amount of reconstitution liquid (see diluent 5) so that large particles, if any, can settle.

NOTE In some cases, especially for products where the original 1+9 slurry is too viscous or too thick, more diluent needs to be added. This should be taken into account in the follow-up and when presenting the results;

further tenfold dilutions: Suspensions or solutions obtained by mixing a specified volume of the original suspension with a ninefold volume of diluent and repeating this procedure until a series of tenfold dilutions suitable for inoculation of the culture medium is obtained;

special standard: A standard or official guide that describes the examination of a specific product (or group of products) for the identification or quantification of a specific microorganism (or group of microorganisms) and describes the specifics of the selection and preparation of test samples.

4 Essence of the method

The essence of the method lies in the preparation of the initial suspension with a uniform, as far as possible for the test sample, distribution of microorganisms. If necessary, in order to reduce the number of microorganisms per unit volume and make it possible to observe their growth or count colonies after incubation, ten-fold dilutions are prepared.

The acceptable number of microorganisms is usually:

- for the most probable counting method using three tubes: 1 microorganism in 10 ml of the highest ten-fold dilution;

- for the colony count method: 30 to 300 colonies (for some groups, eg coliforms, 15 to 150 colonies).

5 Thinner

5.1 To achieve reproducible results, the diluent should be prepared using dehydrated base components or a dehydrated complete preparation.

The manufacturer's instructions must be strictly followed.

All reagents must be chemically pure. or h.d.a.

The water used must be distilled in a glass apparatus or deionized.

5.2 Composition

If there is no conclusive evidence (for example, authoritative data or comparative experiments) that other diluents are more acceptable for these products, then a diluent of the following composition should be used: 1.0 g peptone, 8.5 g sodium chloride, 1 dm of water.

5.3 Preparation

The components are dissolved in water, if necessary, with heating.

The pH of the diluent after sterilization should be 7.0 at 25°C.

5.4 Diluent distribution

The diluent is placed in test tubes, flasks or vials of appropriate capacity in such an amount that, after sterilization, each of them contains 9 ml of diluent or a volume that is a multiple of 9 ml (for tenfold dilutions), or 90 ml of diluent, or a volume that is a multiple of 90 ml (for initial suspensions). For non-liquid products, see 9.1.2. Close the test tubes, flasks or vials with stoppers.

Test tubes, flasks or diluent vials are sterilized in an autoclave at (121±1)°C for 20 minutes.

If the diluent is not used immediately, it should be stored in the dark at a temperature of 0 to 5°C for no more than one month under conditions that do not allow any changes in its volume or composition.

NOTE When counting several groups of microorganisms requiring different culture media, it is necessary to distribute all dilutions (or some of them) in quantities greater than 9 ml. The capacity of tubes, flasks or vials should be indicated accordingly.

6 Hardware

For testing, conventional microbiological equipment is used.

6.1 Apparatus for dry or wet sterilization (oven or autoclave, operating alone or as part of a preparation and dispensing apparatus).

Instrument that will come into contact with diluent, sample or dilutions, other than equipment that is supplied sterile (plastic cups, plastic pipettes, etc.), should be sterilized by one of the following methods:

- by keeping in an oven at 170-175°C for 1 hour;

- by keeping in an autoclave at (121±1)°C for 20 minutes.

6.2 Shaking equipment (for non-liquid products, see 9.1.2).

One of the following devices may be used:

- Rotary shaker, resistant to sterilization conditions, operating at a speed of 8000 to 45000 rpm with glass or metal containers equipped with lids;

- peristaltic type shaker (stomacher) with sterile plastic containers.

NOTE Reservoirs or plastic containers should be of sufficient capacity to allow the sample to be effectively mixed with a sufficient amount of diluent. As a general rule, the capacity of the container should be twice the volume of the sample plus diluent.

6.3 Mixer capable of mixing 1 or 2 ml of sample (in the case of liquid products) or its higher dilution in a tube of appropriate capacity with 9 or 18 ml of diluent to obtain a homogeneous suspension, operating on the principle of eccentric rotation of the contents of the tube (vortex mixer).

6.4 Flasks or vials, of a capacity sufficient to contain 90 ml of the diluent used to prepare the initial suspension, or a multiple of 90 ml (for non-liquid products, see 9.1.2).

6.5 Test tubes (flasks or vials) of sufficient capacity to contain and leave space on top to mix a 10 ml (or multiple of 10 ml) sample of liquid product or initial suspension, or further decimal dilutions.

6.6 Volumetric pipettes, with a capacity of 1 and 2 ml, having an outlet with a diameter of 2 to 3 mm, closed with cotton.

6.7 Graduated pipettes, of capacity 10 ml to 20 ml, closed with cotton.

6.8 pH meter with a measurement error of ±0.1 pH.

6.9 Analytical balances with weighing accuracy up to 0.01 g.

Note - It is allowed to use other equipment with the same or higher metrological characteristics. Glassware must be re-sterilizable and chemically inert.

7 Sampling

7.1 Sampling - according to GOST 13496.0.

8 Preparation of test samples

8.1 Preparation of test samples - according to GOST R 51419.

9 Dilution procedure

9.1 Test sample and initial suspension (primary dilution)

The procedure described in 9.1.1 is used in the following cases:

- for non-viscous liquid products (water, milk, etc.) in which the distribution of microorganisms is homogeneous or easily made homogeneous mechanically (shaking, etc.);

- for the liquid part of a heterogeneous mixture, which is considered to be sufficiently representative of the entire sample (for example, the aqueous phase of animal or vegetable fats).

For all other products, use the procedure described in 9.1.2.

To avoid damage to microorganisms as a result of sudden changes in temperature, the temperature of the diluent during the entire test should be approximately the same as that of the test sample.

9.1.1 Liquid products (which can be pipetted)

Shake the test sample in the hand, making 25 up and down movements with an amplitude of about 30 cm in 7 s. To achieve an even distribution of microorganisms, it is better to use a standard mechanical device. 1 cm of the test sample is taken with a pipette and added to 9 cm of the diluent, avoiding contact of the pipette with the diluent.

Carefully mix the test portion with the diluent by aspirating ten times with another pipette or in a mechanical mixer for 5-10 s. The rotational speed of the mixer must be selected so that the liquid that forms the funnel does not reach the edge of the vessel by 2-3 cm.

NOTE If it is known that, for test products, aggregations of microorganisms are more effectively dispersed by mechanical agitation than by pipetting, and that results are significantly different, then the specific standard for the product under study should recommend only one of these methods, primarily using mechanical agitation. mixing. The conditions of use of the mixer must be specified exactly.

9.1.2 Other products

Weigh (10 ± 0.01) g or a multiple of 10 g of the test sample into a rotary shaker container or a plastic stomacher container of sufficient capacity to carry out the test and prepare all further dilutions required by the specific standard for the test product.

Add a volume of diluent equal to 9 ml or a multiple of 9 ml.

The rotary agitator is used for a time sufficient to obtain from 15,000 to 20,000 revolutions, but not more than 2.5 minutes.

Stomacher is used within 1-2 minutes, taking into account the properties of the product (see note 2).

Allow large particles to settle for 15 min, then transfer a certain amount from the top layer of the suspension into a culture tube, flask or vial using a large pipette. If there is a layer of fat, the sample is taken from the water layer. This amount should be sufficient to complete the entire assay and prepare further dilutions. If on the day of inoculation or further dilution only one portion needs to be taken from the initial suspension, then this transfer can be omitted.

Notes

1 For some products (for example, products with sharp particles or components that are difficult to grind), the stomacher is not suitable. It should only be used when there is evidence (published data or comparative tests) that the results obtained are not significantly different from those obtained using a rotary shaker.

2 Please note that for some products, in particular cereals, the above shaking times are not suitable for microorganisms such as yeasts and moulds.

3 In this case, the stomacher gives higher yields than the rotary shaker. Stomacher should be used within 10 minutes and separation should be avoided as some yeasts and molds may be lost from the supernatant.

9.2 Further tenfold dilutions

In the case of a study on the presence or absence of microorganisms in 0.1 cm or 0.1 g of the product, the following dilutions are prepared.

Transfer with a clean pipette (if the original suspension mixture was pipetted, use the same pipette) 1 ml of the original suspension (primary 1+9 (10) dilution into another tube containing 9 ml of sterile diluent, avoiding contact of the pipette with the diluent.

Mix thoroughly either by pulling ten times with a clean pipette, or in a mechanical mixer for 5-10 s to obtain a dilution of 10. The mixer speed is selected so that the liquid does not reach the edges of the vessel by 2-3 cm during the formation of the funnel.

If necessary, repeat these steps using dilutions of 10 or further dilutions to obtain dilutions of 10, 10, etc. until an acceptable number of microorganisms is obtained.

9.3 Repeat individual procedures

The procedures described in 9.1 and 9.2 are carried out as many times as specified in the specific product standard.

NOTE It has been statistically found that in order to reduce the scatter of results when using the colony count method, the procedures should be repeated with different portions of the test sample, rather than doubling the number of plates populated from each tube of the same dilution series.

9.4 Duration of the procedure

Typically, dilutions are prepared from the test sample immediately prior to analysis; the duration of the procedure for preparing dilutions and using them for inoculation of the culture medium should be no more than 30 minutes.

Note - For some products, when preparing the initial suspension, it is necessary to follow the precautions established by the special standard for a particular product, for example:

- use elevated temperatures to obtain a suspension;

- adjust the pH of the sample;

- restore dehydrated products and revive microorganisms damaged during various processing and storage of the product.

APPENDIX A (informative). Bibliography

APPENDIX A
(reference)

ISO 6497 Animal feed. Sampling methods

OKS 65.120 S19 OKSTU 9209, 9709

Keywords: dilution, diluent, sterilization, initial suspension, decimal dilutions, culture medium, inoculation
__________________________________________________________________________________

Electronic text of the document
prepared by Kodeks JSC and verified against:
official publication
Compound feed. Part 8. Animal feed and
vegetable origin.
Methods of analysis: Sat. GOSTs. -
Moscow: IPK Standards Publishing House, 2002

Feed determines the condition and productivity of animals. By origin, vegetable, animal and mineral feeds are distinguished. Plant foods occupy the largest share. Depending on the moisture content in harvested vegetable feed, there are: hay (12-17%), haylage (40-50%), silage (70-80%).

epiphytic microflora. Microbiological processes occurring during forage ensiling

Microorganisms that live and reproduce on the terrestrial parts of plants are called epiphytic. The study of the species composition of microbes is necessary in order to know what processes they can cause during the preparation and storage of feed. The number of microbes on plants depends on the phase of plant development, humidity, temperature, and other factors. when moistened, the number of microorganisms increases. The older the plant, the more germs. On the surface of the leaves of plants contains a large number of ammonifiers and less than others - lactic acid, butyric, yeast, Escherichia.

Epiphytes are characterized by the fact that, being on the surface of plants, they tolerate the action of phytoncides, sunlight well and feed on substances secreted by plants. The resistance of epiphytes to phytoncides is much higher than that of soil microbes. However, the growth of microbes on the surface of plants is limited, since they release a small amount of nutrients. Epiphytes do not damage or penetrate the tissues of a healthy plant. The role of natural immunity and acidic substances in this is great. (plants secrete phytoncides)

When studying the epiphytic microflora, strict specificity to certain plants was not revealed.

After mowing plants, microbes begin to multiply actively, as the barriers that prevent the penetration of microbes into their tissues disappear. Nutrient loss and food spoilage occur. It acquires a putrid, musty smell, changes color. Plants are easily torn, their consistency becomes smeared. Such feed is poorly eaten by animals and poses a danger to their health.

Ensiling (fermentation) is a method of conservation of green fodder, in which the plant mass is kept wet in pits, trenches or special structures - silos. The feed, more or less compressed and isolated from air, undergoes fermentation. It acquires a sour taste, becomes softer, somewhat changes color (takes on a brown color), but remains juicy.

Ensiling has a number of advantages over other methods of fodder conservation. There are two methods of ensiling: cold and hot.

The cold ensiling method is so named because during the maturation of the silage, a moderate temperature increase occurs in it, reaching up to 40 ° C in some layers of the feed, the optimum temperature is considered to be 25-30 ° C.

With such ensiling, the mowed plant mass, if necessary, is crushed, placed to failure in the feed container, tamped, and covered as tightly as possible from above to isolate from exposure to air.

With the hot method, the silo is filled piecemeal. The green mass is loosely laid for 1-2 days in a layer of about 1-1.5 m. With a large amount of air, vigorous microbiological and enzymatic processes develop in it, as a result of which the temperature of the feed rises to 45-50 ° C. Then a second layer of the same thickness as the first is laid, and it, in turn, is subjected to heating. Plants located below and softened under the influence of high temperature are compressed under the weight of a new layer of feed. This causes air to be removed from the lower layer of the silo, which stops aerobic processes in it, and the temperature begins to decrease. So layer after layer fills the entire silo. The topmost layer of food is compacted and tightly covered to protect it from the air. Due to the fact that the silo in the hot silage method is usually made small in size, a certain load is placed on the top layer of the silage feed.

The heating of the plant mass is associated with the loss (sometimes significant) of the nutrients in the feed. In particular, the digestibility of its proteins sharply decreases. Therefore, hot ensiling cannot be considered a rational way to preserve plant mass.

The cold method of ensiling is the most common. This is due to both its comparative simplicity and the good quality of the resulting feed. The hot method of ensiling is recognized as admissible only for fermentation of coarse-stemmed, low-value feeds, since heating improves their palatability.

Ensiling is associated with the accumulation of acids in the feed, which are formed as a result of fermentation by microbes - acid-forming sugar substances contained in plants. The main role in the ensiling process is played by lactic acid bacteria, which produce lactic and partially acetic acids from carbohydrates (mainly from mono- and disaccharides). These acids have pleasant taste properties, are well absorbed by the animal's body and excite his appetite. Lactic acid bacteria reduce the pH of the feed to 4.2-4 and below.

The accumulation of lactic and acetic acids in the silage determines its safety because putrefactive and other undesirable bacteria for silage cannot multiply in an acidic environment (below 4.5-4.7). Lactic acid bacteria themselves are relatively resistant to acids. Molds that tolerate strong acidification are strict aerobes and cannot multiply in well-covered fermented food.

Thus, sealing and acidity of silage are the main factors that determine its stability during storage. If for one reason or another the acidity of the feed decreases, then this inevitably leads to its deterioration, since conditions favorable for harmful microbes are created.

For normal ensiling of various feeds, unequal acidification is required. Sometimes 0.5% lactic acid lowers the pH of the feed to 4.2, i.e. to a value characteristic of good silage. In other cases, it requires 2% of the same acid. Such a fluctuation depends on the different manifestation of the buffer properties of some components of the plant juice. The mechanism of action of buffers is that in their presence a significant part of hydrogen ions is neutralized. Therefore, despite the accumulation of acid, the pH of the medium hardly decreases until all the buffer is used up. A stock of so-called buffered acids is formed in the silo. The role of buffers can be played by various salts and some organic substances (for example, proteins) that are part of the vegetable juice. A more buffered feed must have more sugars to produce good silage than a less buffered one. Consequently, the viability of plants is determined not only by their richness in sugars, but also by their specific buffer properties. Based on the buffering capacity of plant sap, one can theoretically calculate the sugar norms necessary for the successful ensiling of various plant materials.

The buffering capacity of plant juice is directly dependent on the amount of protein in them. Therefore, most legumes are difficult to ensil, as they are relatively low in sugar (8-6%) and high in protein (20-40%). An excellent silage crop is corn. Its stems and cobs contain 8-10% protein and about 12% sugar. Sunflower is well ensiled, in which, although there is a lot of protein (about 20%), it contains enough carbohydrates (more than 20%). The figures given are based on dry matter.

Knowing the buffering capacity of the feed and its chemical composition, it is possible to solve the problem of the silosability of a particular plant. Basically, the silage is associated with the supply of mono- and disaccharides, which provide the necessary acidification of a certain feed. Their minimum content to bring the feed pH to 4.2 can be called the sugar minimum. According to A. A. Zubrilin, if the feed contains more sugar than the calculated sugar minimum shows, then it will silage well.

Technically, it is not difficult to determine the sugar minimum. By titration, the required amount of acids is established to acidify the test feed sample to pH 4.2. Then determine the amount of simple sugars in the feed. Assuming that about 60% of the sugars in the feed are converted to lactic acid, it is not difficult to calculate whether there is enough sugar available to properly acidify the feed.

To improve the silosability of feeds that are low in carbohydrates, they are mixed with feeds containing a lot of sugar. It is also possible to improve the composition of the silage feed by adding molasses to it according to a certain calculation.

Some foods have too many carbohydrates. When ensiling such feeds, excess acidity occurs (the phenomenon of silage peroxidation). Animals are reluctant to eat too acidic food. To combat acidification of silage, feeds containing a lot of sugar are mixed with feeds that are low in carbohydrates. Sour feed can be neutralized by adding CaCO3.

During fermentation, some of the protein is converted into amino acids. Based on experimental data, it is currently believed that such a transformation is mainly associated with the activity of plant tissue enzymes, and not bacteria.

Since amino acids are well absorbed by the animal organism, the partial conversion of proteins into amino acids should not affect the reduction in the nutritional value of the ensiled mass. There is no deep breakdown of protein with the formation of ammonia in good silage.

During ensiling, there is a partial loss of vitamins in the fermented mass, but, as a rule, it is much less than when hay is dried.

The total loss of feed solids in cold ensiling is much less than in hot ensiling. In the first case, they and - should exceed 10-15%, in the second they reach 30% or more.

Among lactic acid bacteria there are cocci and non-spore-forming rods. Some of these bacteria form mainly lactic acid from sugar, and only traces of other organic acids (homofermentative forms). Others, in addition to lactic acid, accumulate noticeable amounts of acetic acid (heteroenzymatic forms).

Typical representatives of the first group of bacteria include Streptococcus lactis, Str. thermophilus, Streptobacterium plantarum, and from the representatives of the second - Lactobacillus brevis and Betabacterium breve. These microbes are facultative anaerobes.

The nature of the products formed by lactic acid bacteria is affected not only by the biochemical characteristics of one or another culture, but also by the composition of the nutrient medium. For example, if it is not hexose that is fermented, but pentose, then one fermentation product has three carbon atoms, and the other only two (the first substance is lactic acid, the second is acetic). In such a case, the fermentation process can be expressed approximately by the following equation;

6С5Н10О 5 → 8С3Н6О3 + 3С2Н4О2

In vegetable raw materials there are pentosans, which give pentoses upon hydrolysis. Therefore, even with the normal maturation of silage, it usually accumulates some amount of acetic acid, which is also formed by heterofermentative lactic acid bacteria from hexoses.

Most lactic acid bacteria live at a temperature of 7-42°C (optimum is about 25-30°C). Some cultures are active at low temperatures (about 5°C). It was noted that when the silage is heated to 60-65°C, lactic acid accumulates in it, which is produced by some thermotolerant bacteria, such as Bac. subtilis.

Acid-fast yeasts can grow in silage without adversely affecting the quality of the feed. In a properly laid fermented mass, yeast does not multiply strongly. This is due to the fact that they cannot grow at a low level of redox potential created in the silage by lactic acid bacteria. The critical points of H2 for butyric acid bacteria are about 3, for lactic acid bacteria - 6-9, for yeasts - 12-14.

The development of butyric bacteria is associated with the following features. They are more strict anaerobes than yeasts, but are not tolerant of high acidity and will stop growing at a pH close to 4.7-5, like most putrefactive bacteria. The accumulation of butyric acid is undesirable, since it has an unpleasant odor, and feed containing it is poorly eaten by livestock. With vicious fermentation of feed, in addition to butyric acid, it accumulates such harmful products as amines, ammonia, etc.

In the plant mass laid in the silage, there may be bacteria of the intestinal group. They cause putrefactive protein breakdown, and sugar turns into products of little value for canning.

With a normally proceeding ensiling process, the bacteria of the intestinal group quickly die off, since they are not acid-resistant.

Consider the dynamics of silage maturation. The fermentation process can be conditionally divided into three phases. The first phase of maturation of fermented feed is characterized by the development of mixed microflora. On the plant mass, the rapid development of various groups of microorganisms introduced with feed into the silo begins. Usually the first phase of fermentation is short-lived. The end of the first, or preliminary, phase of fermentation is associated with acidification of the environment, which inhibits the activity of most of the microflora of the feed. By this time, anaerobic conditions are established in the silo, as oxygen is consumed.

In the second phase - the phase of the main fermentation - the main role is played by lactic acid bacteria, which continue to acidify the feed. Most non-spore-bearing bacteria die, but bacillary forms in the form of spores can persist for a long time in the fermented feed. At the beginning of the second phase of fermentation, the silage is usually dominated by cocci, which are later replaced by rod-shaped lactic acid bacteria, which are highly acid-resistant.

The third phase of feed fermentation (final) is associated with the gradual death of pathogens of the lactic acid process in the maturing silage. By this time, ensiling is coming to a natural end. The speed of feed acidification depends not only on the amount of carbohydrates in it, but also on the structure of plant tissues. The faster the plants give juice, the faster the fermentation process takes place under the same conditions. The speed of fermentation is facilitated by grinding the mass, which facilitates the separation of the juice.

Several methods are recommended to regulate the ensiling process. Among them, we note the use of starter cultures of lactic acid bacteria. These microorganisms are found on the surface of plants, but in small numbers. Therefore, a certain period is required, during which lactic acid bacteria multiply intensively, and only then their useful activity is noticeably manifested. This period can be reduced artificially by enriching the feed with lactic acid bacteria. It is especially advisable to introduce starter cultures when working with hard-to-silage material.

A technology for the preparation and use of bacterial starter cultures that improve the quality of feed is proposed. In most cases, the lactic acid bacterium Lactobacillus plantarum is recommended. Sometimes another causative agent of lactic acid fermentation is added to this microorganism. Prepare both liquid and dry sourdough.

For feeds with a small supply of monosaccharides, a preparation is prepared with Streptococcus lactis diastaticus. This microorganism, unlike other lactic acid bacteria, can ferment not only simple carbohydrates, but also starch.

There are proposals to add to the ensiled mass, poor in monosaccharides, enzyme preparations (maltase, cellulases) that decompose polysaccharides and enrich the feed with sugars available to lactic acid bacteria.

When ensiling feeds with a large supply of carbohydrates (for example, corn), which give too acidic feed, which is undesirable, a starter is prepared from propionic acid bacteria. When using it, part of the lactic acid is converted into propionic and acetic acid, which dissociate weakly, and the feed becomes less acidic. In addition, propionic acid bacteria produce significant amounts of vitamin B12.

To improve the silosability of difficult-to-ferment feeds, it is proposed to use an amylase preparation. This enzyme converts feed starch to maltose, which increases the reserve of sugars available to lactic acid bacteria and enhances feed acidification.

Buffer acid mixtures are also recommended, which include various mineral acids. In the CIS, preparations AAZ, VIC, etc. are proposed. Abroad, AIV, Penrhesta, etc. are used. Organic acids (for example, formic) are successfully used.

Acid preparations are used for hard-to-ferment fodder. Their introduction into the silage feed suppresses the development of saprophytic microflora of the first phase of fermentation. The pH (about 4) created in the plant mass by acid mixtures does not prevent the development of lactic acid bacteria, which keep the pH of the feed at a low level.

For the preservation of poorly fermented feed, preparations containing calcium formate, metabisulphite, sodium pyrosulfite, sulfamic, benzoic, formic acids and other substances that suppress microbiological processes in ensiled feed and preserve it are also recommended.

The above information refers to the conservation of feed with normal moisture content (about 75%). If the moisture content of the preserved mass is much lower (50-65%), then good fermentation occurs even with a shortage of carbohydrates and a high quality feed is obtained - haylage. At the same time, the pH of the feed can be quite high - about 5, since putrefactive bacteria have a lower osmotic pressure than lactic acid ones. When the feed is dried, putrefactive processes stop in it, but the causative agents of lactic acid fermentation continue to act. The preparation of haylage is based on this, when a somewhat dried mass is laid for conservation, as in cold ensiling.

The research of the authors showed that microbiological processes develop in clover, the humidity of which was 50% and below. They flow the weaker, the drier the food. Lactic acid bacteria quickly become the dominant microflora in canned food. This group of rather specific microorganisms is close to Lactobacillus plantarum, but differs in the ability to grow in a much drier environment and ferment starch. Their development in the feed leads to the accumulation of a certain amount of lactic and acetic acids in it.

According to the type of haylage, chopped corn cobs intended for fodder with a moisture content of 26-50% (optimum 30-40%) are well preserved.

Recently, the Kuibyshev Agricultural Institute has recommended treating under-dried hay (with a moisture content of about 35%) with liquid ammonia, which acts as a preservative.

With the introduction of ammonia in the feed, an alkaline reaction is created that blocks microbiological and enzymatic processes. Ammonia treated feed should be covered with some kind of insulating material.

Some technological methods of feed conservation are based on principles that exclude the development of microbiological and enzymatic processes in the feed. This is the production of herbal flour, granulation, briquetting and the manufacture of mixtures using high temperatures, and sometimes high pressure.

Microbiology of forage and haylage ensiling. microorganism biology food epiphytic microflora. Microbiological processes occurring during forage ensiling

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Feed microflora

Microflora of food products during refrigerated storage

Similar Documents

1 area of use

2 Normative references

3 Definitions

4 Essence of the method

5 Thinner

6 Hardware

7 Sampling

8 Preparation of test samples

9 Dilution procedure

APPENDIX A (informative). Bibliography

epiphytic microflora. Microbiological processes occurring during forage ensiling

Send your good work in the knowledge base is simple. Use the form below

Feed microflora

Microflora of food products during refrigerated storage

Similar Documents

1 area of ​​use

2 Normative references

3 Definitions

4 Essence of the method

5 Thinner

6 Hardware

7 Sampling

8 Preparation of test samples

9 Dilution procedure

APPENDIX A (informative). Bibliography

epiphytic microflora. Microbiological processes occurring during forage ensiling

1 area of use