Lactic acid is one of the chemical reagents formed as a result of the breakdown of glucose and its derivatives into its components. Lactic acid belongs to the carboxylic group. The substance is found in the cells of the brain, heart, muscle tissue, and tissues of other organs. The compound is the root of almost all the problems of athletes: it causes deterioration in well-being, muscle pain, cramps, oxygen deprivation and injuries. Many people view lactate as a product that should be avoided at all costs. However, in fact, this acid plays an important role in the production of energy, which is required to maintain muscle tone. It is especially important during active training.
Lactic acid molecule
What is lactic acid?
Lactic acid is a colorless or faint yellow liquid with a faint odor and a distinct sour taste. The substance dissolves easily in different media: alcohol, glycerin and ordinary water. The first information about lactate dates back to the 80s of the 18th century. The main area of use of the compound is the food industry. In food production, lactic acid is known under the index E270, and its derivatives under the index E271.
Lactic acid is a natural biological substance that plays an important role in the metabolic process.
For a long time, chemists believed that lactate could cause apathy, loss of strength, fatigue, cramps, loss of sensation in the limbs and severe muscle pain. However, over time, this claim was refuted, and lactic acid regained its reputation. Researchers have proven that the substance is responsible for energy production during sports. It promotes better absorption of carbohydrates and supplies energy to many organs, in particular the liver, brain and heart.
Formula of lactic acid and its properties
The formula for lactic acid is as follows:
C3H6O3
As can be seen from the formula, the substance contains 3 molecules of carbon atoms, six hydrogen atoms and three oxygen atoms.
Lactic acid is the simplest organic compound, existing in the form of two enantiomers. The compound is hygroscopic and typically exists in the form of a colorless or barely yellow aqueous solution. In this regard, it is quite problematic to establish the temperature at which lactic acid begins to melt. Specialized sources indicate the melting point of lactic acid in the range from 18 to 33 degrees.
Lactate is highly soluble in water and alcohol, which are miscible with water. The compound is practically unaffected by benzene and chloroform.
The substance decomposes when reacting with oxidizing agents. When reacted with oxygen or nitric acid in the presence of iron or copper, the compound is converted into formic, acetic and oxalic acid, carbon dioxide and pyruvic acid.
Obtaining lactic acid
In industry, lactate is produced in two ways: enzymatic and synthetic. The first method is more popular because it produces a purer compound. It uses carbon raw materials, nutrients and a number of microorganisms. The main raw materials are glucose, corn-based syrups, molasses, sugar beet juice, whey and potato starch. Upon completion of the fermentation procedure, the resulting acid is subjected to a thorough purification procedure. Undesirable inclusions are separated by flocculation occurring in an alkaline medium or ultrafiltration.
In the pharmaceutical industry, methods for producing lactic acid with purification in several stages are used. The most common method is to extract lactic acid into the organic phase with long-chain tertiary amines and then back-extract it into water.
There is a synthetic method for producing lactic acid. It is based on the reaction of acetaldehyde with hydrogen cyanide and subsequent hydrolysis of the resulting lactonitrile.
15.7.10.5. Lactic acid production
Lactic (2-hydroxypropionic, α-hydroxypropionic) acid is the simplest hydroxy acid having an asymmetric carbon atom, providing the existence of two optical isomers, i.e. D (or R) and L (or S) forms. L-Lactic acid is absorbed by the body, but the D-isomer is not.
Lactic acid is produced industrially by chemical (50%) and enzymatic (50%) syntheses [179].
Chemical synthesis is based on the reaction of acetaldehyde with hydrogen cyanide, resulting in the production of lactonitrile, the hydrolysis of which produces lactic acid.
When lactic acid is produced using lactic acid bacteria and chemical synthesis, optically inactive D,L-lactic acid is formed.
L(+)-Lactic acid is produced by lactic acid streptococci ( S. termophilus
,
S. lactis
,
Leuconostoc cremoris
), and
Lb.
lactis and
Lb.
bukgaricus produce about 90% D(–)-lactic acid [104].
The causative agent of lactic fermentation in the production of lactic acid is the culture of Lactobacillus delbrukii
.
Properties of lactic acid bacteria [104]
Lactobacillus delbrüeckii
- thermophilic grain must bacterium. These bacteria ferment glucose, maltose, fructose, galactose and sucrose well.
Lactic acid bacteria are gram-positive, nonmotile, facultative anaerobes. They have the shape of large rods 7–8 µm long, 0.5–0.8 µm thick and, as a rule, form short chains of 2–4 cells.
Lactic acid bacteria require the following amino acids: arginine, cysteine, glutamic acid, leucine, phenylalanine, tryptophan, tyrosine, lysine and possibly some others.
Of the vitamins, the producer needs riboflavin, nicotinic and folic acids; thiamine inhibits the formation of lactic acid.
From mineral nutrition, lactic acid bacteria need: sodium, potassium, phosphorus, copper, iron, sulfur, magnesium and, especially, manganese. Therefore, to sugar-containing media it is necessary to add dry sprouts of barley, rye or wheat malt, malt extract, sedimentary wine or alcohol yeast, yeast autolysate, and wheat germ.
The optimal temperature for the development of the producer is 48–50 °C; fermentation takes place in a slightly acidic environment (pH 5.5), but at pH = 3.0 the development of bacteria stops. At a pH above 7, the nutrient medium becomes easily infected.
Due to sensitivity to the acidity of the environment, the resulting lactic acid is neutralized with chalk, maintaining the acidity at 0.3–0.4%:
2C3H6O3 + CaCO3 = Ca(C3H5O3)2 + CO2 + H2O
The solubility of calcium lactate at 50 °C is 15–16%.
Raw materials for the production of lactic acid [104, 173]
In the domestic production of lactic acid, the raw material is a mixture of raw cane sugar, refined molasses and beet molasses. Malt sprouts serve as a source of essential organic and mineral substances.
Raw cane sugar contains, %: DM - 99.4-99.6 (including sucrose - 96.5-98), RS - 0.6-0.9, organic non-sugars - 0.7-1.
The use of molasses allows you to speed up the fermentation process due to the presence of substances necessary for lactic acid fermentation. However, due to the intense color of molasses, the use of large quantities leads to difficulties in purifying lactic acid.
Refined molasses is a viscous brown liquid containing at least 72% dry matter, including 49% sucrose, pH value not lower than 5.5.
Compared to molasses, it has higher quality, approximately half the color, contains less colloids (1.3–3.0%), ash (3–5%) and nitrogen (0.25%), more invert sugar (10– 20%), but it lacks vitamins.
Malt sprouts contain up to 30% nitrogenous substances, about half of which are soluble in water. The sprouts contain the bulk of the vitamins and biostimulants of sprouted grain: riboflavin, pyridoxine, cyanocobalamin, nicotinic acid, pantothenic acid, tocopherol, inositol, biotin. The sprouts should be yellow or brown; the presence of 5–6% grain admixture is allowed; minerals - no more than 0.5%.
To obtain lactic acid, you can use ultrafiltrates of milk and whey, waste from fruit juice production.
However, the best substrate is D-glucose (lactic acid yield 86%), which can be replaced, for example, with wood hydrolysates, carrying out conversion using Lb plantarum
ETH B-4258.
Lactic acid production technology [15, 173]
The main stages of the lactic acid production process are shown in Fig. 15.7.55 [66].
Rice. 15.7.55.
Technological scheme for the production of lactic acid
Obtaining seed
It is also produced in several stages.
The pure culture is seeded into three test tubes with freshly prepared nutrient medium. The culture from one test tube (others are “museum” and spare) is transferred into a flask (500 ml), and then into a bottle (10 l) and finally into a cultivator. The volume of seeding culture should be up to 30 vol. % of the capacity of the fermenter.
The first two stages are carried out on a nutrient medium from malt wort, the third - on a medium from wort and production medium (1:1) and the last - on production medium. The duration of each stage is 20–24 hours (48–50 °C).
An indicator of the maturity and activity of a bacterial culture at each stage of reproduction is the population density, which should be 700–800 cells/ml. After 10–15 hours, an active culture accumulates up to 0.5% lactic acid.
When preparing the inoculum, the bacteria are passaged several times in a medium with a slight excess of chalk, kept at 45–55 °C; each stage lasts 16–18 hours.
Nutrient medium
prepared directly in the fermentation apparatus. The fermenter is filled with water and wash water to 2/3 of its capacity, heated to 70 °C, molasses, refined molasses and dissolved raw sugar are fed into it. (NH4)2SO4 and NH4HPO4, as well as malt or corn extract are added to the medium. The mass fraction of sugar in the solution should be 3–4 mass. %. The solution is heated to 70 °C and pasteurized at this temperature for 1 hour. After cooling to a temperature of 48–50 °C, 15 wt. % by weight of sugar of malt sprouts.
Lactic acid fermentation -
The formation of lactic acid can be described by the equation:
С6Н12О6 → 2С3Н6О3
According to the equation, 100 g of glucose produces 100 g of lactic acid; practical yield is 90–91 wt. % by weight of sugar.
Since foreign microflora develops at temperatures below 45 °C, fermentation is carried out at a temperature of 48–50 °C. Increasing the temperature above 55 °C reduces the activity of lactic acid bacteria.
Fermentation is carried out in apparatus (vats) with a capacity of 25–45 m3.
After preparing the nutrient medium, QL (20 vol.% of its capacity) with lactic acid bacteria is added to the apparatus. After 6 hours, begin stirring the mixture by bubbling air. Once the mass fraction of lactic acid reaches 0.5–0.6 wt. % (about a day after sowing), they begin to add chalk milk, maintaining the mass fraction of acid in the solution at the level of 0.3–0.4 wt. %.
To neutralize 1 kg of lactic acid, 0.55 kg of calcium carbonate is required. As a result of neutralization, 120 masses are formed. % calcium lactate by weight of fermented hexose or 125 wt. % by weight of the disaccharide.
During normal fermentation, up to 2% of sugar is fermented per day, the loss of which is compensated by adding a 50% solution of raw sugar with the addition of refined molasses, maintaining the mass fraction of sugar in the medium at the level of 3–4%. Fermentation is carried out until the concentration of calcium lactate is about 15% (6–8 days).
To clean the culture fluid,
which contains solid impurities - chalk, malt sprouts, as well as colloidal particles, is treated with lime milk at a temperature of 70–80 ° C, during which iron ions precipitate, proteins coagulate, and unfermented sugar is destroyed. To separate suspended particles, the culture liquid is allowed to settle for 6–12 hours at a temperature above 48 °C. After settling (6–12 hours), the mixture is filtered, and the filtrate with the first portion of wash water is sent for lactate crystallization.
When calcium lactate crystallizes
about 2/3 of the salt remains in the mother solution, therefore, along with purification of lactic acid by crystallization of lactate, purification is also used with ion exchange resins.
lactate (
) is described by the following equations [28]:
in the temperature range 12–35 °C: y
= 1.9 exp(0.035
T
),
in the range of 40–80 °C: y
= 1.4exp(0.0435
T
).
When calcium lactate crystallizes, its initial concentration in solution is 14.5–15.5%; at higher concentrations, separation of crystals becomes difficult due to their small size. The optimal initial temperature of the solution is 30 °C. After filling the crystallizer, a seed is added (6–7 wt.% by weight of lactate) in the form of raw crystals from the previous crystallization. The final solution temperature should not exceed 10 °C; the total duration of crystallization is 10–12 hours.
During the crystallization process, the temperature is reduced in the first hour from 30 to 23 °C, and in the next 1.5 hours - from 23 to 16 °C (mass crystallization begins). Next, the temperature is reduced at a rate of 2 degrees/hour, and then the mixture is kept for 3 hours at 10 °C. After separating the crystals by filtration or centrifugation and washing them, the lactate yield is 80 wt. % of the mass of crystals contained in the massecuite, with a good quality of 96%.
From the mother liquor, after decomposition of the lactate, separation of gypsum and clarification of the solution with active carbon, second-grade lactic acid is obtained.
Knowing the lactate content in the initial ( C
m) and final (
C
m) solutions (mass %), you can calculate its yield as a percentage of the solution mass (
K
, anhydrous substance) or as a percentage of the lactate content in the initial solution (
A
):
Purified calcium lactate solution
decomposes with sulfuric acid:
Ca(C3H5O3)2 + H2SO4 = 2C3H6O3 + CaSO4
Calcium sulfate is released from the solution in the form of a precipitate (gypsum). To obtain a coarse-crystalline gypsum sediment, the following conditions are necessary: supersaturation coefficient 1.3–1.4; the mass fraction of calcium lactate is not higher than 18 wt. %; temperature 80 °C; excess sulfuric acid 0.5%; The duration of ripening of gypsum crystals is 1 hour.
The completeness of decomposition of calcium lactate is controlled using a color reaction with a 0.1% solution of methyl violet, which should have a cornflower blue color, with an excess of sulfuric acid - green, calcium lactate - purple.
Iron compounds are precipitated with yellow or red blood salt, and the use of the latter is preferable, since the resulting calcium lactate decomposes further to form insoluble calcium sulfate:
4Fe(C3H5O3)3 + 3Ca[Fe(CN)6] = Fe4[Fe(CN)6]3 + 6Ca(C3H5O3)2
Compounds of heavy metals and arsenic are precipitated with barium sulfide. To clarify the solution, it is treated with active carbon, and the precipitate is separated by filtration.
Clarification and evaporation of lactic acid solution
carried out using activated carbon (OU-A) either before gypsum separation or after sludge separation. The clarified solution is concentrated to a mass fraction of lactic acid of 40 wt. % on vacuum evaporators (80 kPa). After evaporation, the solution is again treated with active carbon (correction) and, after filtering, poured into containers.
Properties of lactic acid [173]
Food grade lactic acid is produced in the form of an aqueous solution with a concentration of 40%, the quality of which is regulated by GOST 490–79 (Table 15.7.143).
Table 15.7.143
Chemical indicators of food lactic acid [173]
| Indicators | Variety | ||
| higher | first | second | |
| Mass fraction of total lactic acid, wt. % | 40±1 | ||
| Mass fraction of directly titrated lactic acid, wt. %, not less | 37,5 | 35,0 | |
| Mass fraction, mass. %, no more | |||
| anhydrides | 2,5 | 5,0 | |
| ash | 0,6 | 1,0 | 4,0 |
| gland | 0,007 | 0,014 | 0,020 |
| sulfates | 0,3 | Not standardized | |
| chlorides | 0,1 | ||
| reducing substances | 0,1 | ||
| Color, grad, no more | 6,5 | 10 | 30 |
| Mass fraction of arsenic, mg/kg, no more | 0,3 | ||
| Heavy metal salts | Must stand the test | ||
| Ferrocyanides | |||
| Hydrocyanic acid | |||
| Free sulfuric acid | |||
| Barium | Not allowed | ||
Lactic acid is also obtained at a 70% concentration, for which secondary evaporation is carried out in vacuum devices, followed by filtration on filter presses. The product is available in liquid form or as a paste, which is obtained by adding a small amount of chalk to concentrated acid.
D-Lactic acid has T
melt 53 °C,
boiling
point 103 °C (2 mmHg); D,L-lactic acid - 18 and 85 °C (1 mm Hg), respectively [155] (see section 15.7.10).
The dynamic viscosity of lactic acid solutions at a temperature of 25 °C is given in table. 15.7.144.
Table 15.7.144
Dynamic viscosity of aqueous solutions of lactic acid [28]
| Concentration, mass. % | Viscosity, mPa × s | Concentration, mass. % | Viscosity, mPa × s |
| 6,29 | 1,04 | 54,94 | 4,68 |
| 9,16 | 1,15 | 64,89 | 6,96 |
| 12,19 | 1,21 | 75,33 | 13,03 |
| 24,35 | 1,67 | 85,32 | 28,50 |
| 37,50 | 2,45 | 88,60 | 36,90 |
| 45,48 | 3,09 |
Use of lactic acid [28, 155]
Lactic acid is used in the food industry [102], in medicine and veterinary medicine [173] and for a variety of technical purposes.
Lactic acid inhibits the development of putrefactive bacteria, but has no effect on microscopic fungi and yeast. Lactic acid and its salts in the presence of water are strong plasticizers for almost all proteins. In bread baking, lactic acid and lactates increase the volume of the crumb and improve the crust of bread.
Lactic acid is added to the mash in brewing to reduce water hardness and achieve a pH value close to optimal for the action of amylolytic and proteolytic enzymes. Lactic acid is used in the production of baker's yeast to purify seed yeast from foreign microflora, including lactobacilli, as well as to purify molasses, stimulating the proliferation of yeast.
Lactates of sodium (E325), potassium (E326), calcium (E327), ammonium (E328) and magnesium (E329) are allowed for use in food products. They are used in the production of soft drinks, caramel masses, and fermented milk products.
Sodium lactate increases the volume and stability of foam in protein-whipped masses of confectionery products and ice cream.
Esters of lactic acid - lactylates [102] (E481, E482) - belong to the group of anionic surfactants.
This subgroup of food surfactants includes derivatives of lactic acid with higher fatty acids (stearic or oleic) in the form of sodium or calcium salts. The structure of a substance can be described by the following formula:
,
where R is acyl stearic or oleic acid; Me - Na or Ca; n
— degree of polymerization of lactic acid (from 1 to 4).
The purity criteria for lactylates are presented in table. 15.7.145.
Table 15.7.145
Characteristics of lactylates [102]
| Criterion | E 481 | E 482 |
| Content, mass. %: | ||
| sodium | 2–5 | — |
| calcium | — | 1–5 |
| Essential number, mg KOH/g: | ||
| no less | 90 | 125 |
| no more | 190 | 190 |
| Total content of lactic acid (free and bound), mass. %: | ||
| no less | 15 | 15 |
| no more | 40 | 40 |
| Acid number, mg KOH/g: | ||
| no less | 60 | 50 |
| no more | 130 | 130 |
| GLB | 10–12 | 5–6 |
Calcium lactate [173] is an important therapeutic drug in the treatment of calcium deficiency (rickets) in human and veterinary medicine.
It is used as a hemostatic agent for pulmonary, gastrointestinal, nasal and other bleeding, in surgical practice - to increase blood clotting, to relieve itching in allergic diseases.
Magnesium lactate has a laxative effect, ferrous lactate is used for acute and chronic anemia.
In veterinary medicine, lactic acid is used to suppress the development of harmful intestinal microbes in piglets that have just been weaned from their mother's milk; with inflammation of the stomach, intestines; for gynecological diseases; for ulcerative skin lesions.
Adding a 1% solution of calcium lactate to chicken feed increases egg production by 15% due to a decrease in the number of microbes in the intestines of birds that destroy protein.
Lactic acid is used in the leather industry for decalcification of skins and furs; In the textile industry, lactic acid and its antimony salt are used in mordant dyeing and finishing of fabrics (finishing). Lactates are used as anti-corrosion agents in antifreeze solutions.
Ethyl and butyl lactates (Table 15.7.146) [155] are used as solvents for cellulose ethers, drying oils, and vegetable oils; butyl lactate is also used as a solvent for some synthetic polymers. Lactic acid also becomes important as a monomer in the production of biodegradable polymers.
Table 15.7.146
Properties of some lactates [155]
| Index | Methyl lactate | Ethyl lactate | Butyl lactate |
| T melt, °C | –66 | — | –28 |
| T kip, °C | 144,8 | 154 | 187 |
| 1,0939 | 1,0348 | 0,9837 | |
| 1,4139 | 1,4132 | 1,4217 | |
| h, MPa × s | 2.92 (25 °C) | 2.681 (20 °C) | — |
| g, mN/m | — | 29,2 | 28,8 |
Preparation of polylactides [180–182]
Polylactides are aliphatic polyesters synthesized from lactic (2-hydroxypropionic) acid.
Polylactide is a polycrystalline polymer with a glass transition temperature ( T
c), equal to 55±5 °C, and a softening temperature (
Тр
) 170±10 °С. Typical values for tensile strength and elongation are 50 MPa and 2%, respectively.
Polylactides are used mainly in medicine, where high strength and rigidity are not required. Industrial polylactide is called EcoPla.
Low molecular weight polylactides can be considered as polycondensation products of lactic acid. A higher degree of polymerization is achieved when using a cyclic dimer (lactide, 121
, - 3,6-dimethyl-1,4-dioxane-2,5-dione), shown in Fig.
15.7.56.
lactide is mainly used to obtain polymers ( 122
Rice. 15.7.56.
Structure of L-lactide (
121
) and poly-L-lactide (
122
)
Preparation of lactide.
A cyclic dimer has two stereocenters and therefore three stereoisomers (two enantiomers and a meso form).
The enantiomers are called L-lactide (derived from L-lactic acid) and D-lactide (from D-lactic acid). meso
-Lactide contains one atom in the L-form and the other in the D-form.
The production of lactide involves the distillation of lactic acid. First, water is distilled off, and then lactide. The process occurs in two stages. At the first stage, oligomeric linear lactide is formed during the dehydration of lactic acid (DP 10–30). In the second stage, the oligomer depolymerizes and produces lactide under reduced pressure. Lactide is distilled at 200–240 °C and a pressure of 5 mm Hg. Art.
From 200 g of lactic acid, 125 g of lactide are obtained, T
Melt 128°C.
The yield can be increased by adding a catalyst: zinc powder, zinc oxide, titanates, tin powder.
Optically pure L- or D-lactide ( T
melt 96–98 °C) can be obtained from pure enantiomers.
Synthesis of polylactide
Polycondensation of lactic acid is the simplest method for producing polylactide. When water is removed from a lactic acid solution, a polymer with an increasing DP is formed. In this way, it is possible to obtain a polymer with a molecular weight of several thousand.
When using solid acid catalysts like aluminum silicate or ion exchange resin, a polymer with M 30,000 Da can be obtained.
Using dehydrating agents, it is possible to obtain a polymer with M up to 36,000 Da. The following are proposed as such agents: bis-(trichloromethyl)-carbonate {(Cl3CO)2CO}; N
,
N'
-carbonyldiimidazole {(C3H3N2)2CO} and dicyclohexylcarbodiimide {DCC, (C6H11N)2C}.
Polymers with different molecular weights can be obtained from lactide. The highest molecular weight polymer is obtained by block polymerization carried out at low temperature using very pure lactide and a low concentration of catalyst [tin(II) bis(2-ethylhexanoate)]. The molecular weight can be controlled by adding an initiator, which can be water, alcohols or amines.
O) as a catalyst
,
O
')zinc [(Zn(DMH)2], bis(2,4-pentanedionato-
O
,
O
')tin [(Sn(Acac)2].
The physical properties of polylactides are highly dependent on the stereochemical composition or tacticity.
Softening temperature T
p of isotactic L-polylactide and D-polylactide is highly dependent on molecular weight and degree of crystallinity and can range from 131 to 207 °C.
Most often T
p is in the region of 180 °C.
Atactic polylactides are amorphous substances. For a polymer containing 85 mol. % L-lactide and 15 mol. % D-lactide, T
p is 125 °C.
Similar to the softening temperature, the glass transition temperature T
c increases with increasing degree of crystallinity and molecular weight.
In most cases, Tc
for both isotactic and atactic polymers lies in the region of 60 °C.
History of lactic acid
Lactic acid was first produced artificially at the dawn of the 18th century in Sweden by pharmacist Karl Scheele. During lengthy experiments, the scientist isolated the compound from brown syrup and sour milk. Later, another chemist from another country, Henri Braconneau from France, confirmed that acid is formed during lactic acid fermentation.
The experience of his colleagues was adopted by the Swedish chemist Jens Jakob Berzelius, who in 1807 isolated the zinc salt of lactic acid, which is found in muscles.
Domestic scientists - chemists from the Soviet Union - also devoted their activities to the study of lactic acid. Their experiments were extremely successful. In the 30s of the 20th century, they received high quality lactate. It does not contain traces of iron, and in its production special equipment is used to prevent iron impurities from entering the acid.
Functions of lactic acid in the human body
Lactic acid is necessary for the body as a source of energy resource, as a raw material for the synthesis of glucose and glycogen. Muscles especially need connection. During intense physical activity, lactic acid accumulated in fast-twitch muscle fibers moves to the slow-twitch fibers, heart and respiratory muscles, where it is used as energy fuel.
But only 75% of the substance is used as fuel; the rest is transported by the blood to the liver and kidneys, where it is converted into glucose. There is no excess lactate left in the body, but a sufficient level of glucose is continuously maintained in the blood, which is especially important for long-term training.
What are the benefits of lactate for health and fitness?
Lactate is a source of energy
In the 80s and 90s, George Brooks proved Lactic Acid Not Athlete's Poison, But An Energy Source - If You Know How To Use It that lactate passes from muscle cells into the blood and is transported to the liver, where it is reduced to glucose in the Cori cycle. After this, glucose is again transported through the blood to working muscles and can be used for energy production and stored in the form of glycogen.
Moreover, even muscles can use lactate as fuel. In 1999, Brooks discovered Lactic Acid Not Athlete's Poison, But An Energy Source - If You Know How To Use It that endurance training reduces blood lactate levels even when cells continue to produce the same amount. In 2000, he found that endurance athletes had an increased number of lactate transporter molecules, which quickly move lactate from the cell cytoplasm to the mitochondria.
In further experiments, scientists discovered not only carrier proteins inside the mitochondria, but also the lactate dehydrogenase enzyme, which triggers the conversion of lactate into energy.
Scientists concluded that lactate is transferred to mitochondria and burned there with the participation of oxygen to produce energy.
Lactate serves as a source of energy for muscles. In the liver, it is reduced to glucose, which is then used again by the muscles or stored in them in the form of glycogen. In addition, lactate can be burned directly in the muscles to produce energy.
Lactate increases endurance
Lactate helps increase oxygen consumption, which also has a positive effect on endurance. Research Lactate, not glucose, up-regulates mitochondrial oxygen consumption both in sham and lateral fluid percussed rat brains. 2006 showed that lactate, unlike glucose, increases the amount of oxygen consumed by mitochondria, which allows them to produce more energy.
And in 2014, it was found that lactate reduces the response to stress and increases the production of genes involved in the creation of new mitochondria.
Lactate increases the amount of oxygen consumed so your body can tolerate stress longer.
Lactate protects the brain
Lactate prevents L-glutamate-induced excitotoxicity. This is a pathological condition in which, due to excessive activity of neurons, their mitochondria and membranes are damaged and the cell dies. Excitotoxicity can cause multiple sclerosis, stroke, Alzheimer's disease and other diseases associated with damage to nerve tissue.
The 2013 Lactate Modulates the Activity of Primary Cortical Neurons through a Receptor-Mediated Pathway study demonstrated that lactate regulates neuronal activity, protecting the brain from excitotoxicity.
In addition, lactate provides the brain with an alternative source of nutrition when glucose is in short supply. Also in 2013, scientists found out that Lactate preserves neuronal metabolism and function following antecedent recurrent hypoglycemia. That a slight increase in lactate circulation allows the brain to function normally in conditions of hypoglycemia.
Moreover, the study Lactate Effectively Covers Energy Demands during Neuronal Network Activity in Neonatal Hippocampal Slices. 2011 showed that glucose is not enough to provide energy during intense synaptic activity, and lactate may be an effective energy source that supports and enhances brain metabolism.
And finally, a study of Lactate-mediated glia-neuronal signaling in the mammalian brain. 2014 showed that lactate increases the amount of norepinephrine, a neurotransmitter that is necessary for supplying blood to the brain and concentration.
Lactate protects the brain from excitotoxicity, serves as a source of energy and improves concentration.
Lactate promotes muscle growth
Lactate creates good conditions for muscle growth. Research: Mixed lactate and caffeine compound increases satellite cell activity and anabolic signals for muscle hypertrophy. 2015 showed that caffeine and lactate supplementation increased muscle growth even during low-intensity exercise by activating stem cells and anabolic signals: increasing the expression of myogenin and follistatin.
Even 20 years ago, scientists discovered Lactate and the effects of exercise on testosterone secretion: evidence for the involvement of a cAMP-mediated mechanism. that after administration of lactate and exercise (swimming), the amount of testosterone in the blood plasma increases in male mice. In addition, the amount of luteinizing hormone increases, which also promotes the secretion of testosterone. And this, in turn, has a positive effect on muscle growth.
Lactate increases the secretion of hormones necessary for muscle growth.
Lactic acid concentration in the body
The concentration of lactic acid determines the quality of carbohydrate metabolism and the degree of oxygen saturation of tissues. In the body of a healthy person, the lactate content in the blood varies from 0.6 to 1.3 mmol/liter. Cramps and other unpleasant sensations in muscle tissue are explained by an increase in this indicator.
Exceeding the concentration of lactic acid in the body indicates a lack of oxygen. And the lack of oxygen, in turn, is one of the symptoms of heart failure, anemia and impaired lung function. In oncology, an excess of lactic acid concentration can be an indicator of the growth of malignant tumors. Increased acid levels can cause cirrhosis, hepatitis and diabetes.
Exceeding the concentration of lactic acid can be observed in a healthy body - immediately after active sports.
Links
- Regulation (EU) No 528/2012 of the European Parliament and of the Council of 22 May 2012 concerning the making available on the market and use of biocidal products
- Opinion of the biocidal products committee on the application for approval of the active substance Triclosan in product type 1, ECHA/BPC/066/2015, adopted 17 June 2015
- Opinion of the biocidal products committee on the application for approval of the active substance L(+)-lactic acid in product type 1, ECHA/BPC/084/2015, adopted 10 December 2015
- Regulation (EC) No 1272/2008 on classification, labeling and packaging of substances and mixtures
- SP Denyer, GSAB Stewart, International Biodeterioration & Biodegradation 1998, 41, 261–268
- RE Glover, RR Smith, MV Jones, SK Jackson, CC Rowlands, FEMS Microbiology Letters 1999, 177, 57–62
- JD Van Hamme, A. Singh, OP Ward, Biotechnology Advances 2006, 24, 604–620
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This article was originally published in Household and Personal Care Today, January/February 2022, Vol. 12(1), p. 20–21
Daily lactic acid intake
There is no clear definition of the daily intake of lactic acid. However, there are recommendations from experts for people leading a sedentary lifestyle on eating food with lactic acid. To restore the balance of lactic acid in the body, just two glasses of kefir per day are enough. This will be enough for the complete absorption of acid molecules by the body.
Children during periods of active growth, as well as adults whose work involves intellectual activity, have a special need for lactate. But an elderly body does not need large volumes of lactic acid.
Delayed pain syndrome - what is it?
If pain after training does not occur immediately , but after a while, then the problem is not due to a harmful substance. This is the so-called delayed pain syndrome .
As a result of hard training, microtraumas - they are very small, as they are only a few millimeters. They usually appear after 2-3 days, and the body is struck by aching pain . Therefore, it is necessary to distinguish excess lactic acid from this syndrome in order to select the correct treatment package.
How to remove excess lactic acid?
How does the presence of excess acid in muscles manifest itself?
Lactate is formed in muscle tissue as a result of active training. It is a consequence of the breakdown of glucose and consists of hydrogen and the lactate anion.
Hydrogen interferes with the free transmission of nerve impulses and significantly reduces the rate of contraction of muscle fibers. The accumulation of large amounts of lactate in the muscles is accompanied by a number of symptoms, including:
- burning sensation in the muscles involved during training;
- discomfort throughout the body;
- general weakness and noticeable loss of strength, lack of interest in the environment;
- discomfort when moving;
- pain during subsequent workouts;
- with a particularly large excess of lactate, an increase in temperature may be observed.
Unpleasant sensations can persist for several days, after which they pass without any manipulation on your part. But with a particularly large excess of lactic acid, the restoration of muscle fibers may take a longer period. If a strong burning sensation occurs, it is recommended to reduce the intensity of training for a while.
Why is lactic acid not eliminated from the body on its own?
During muscle tissue work, a constant supply of oxygen is required to continuously replenish energy reserves. But with particularly intense contractions of muscle fibers, the rate of blood circulation in them decreases, and the flow of oxygen is blocked. The body, at the same time, does not stop functioning; accordingly, the body looks for other ways to obtain the energy it needs, through the synthesis of glycogen into ATP. As a result, lactate is formed in the muscles. The body is not able to remove it all at once, so the substance accumulates and unpleasant sensations arise in the body.
Prolonged presence of lactic acid in muscle tissue can cause the following reactions in the body:
- insufficient amount of energy resource;
- lack of creatine in muscle fibers;
- stopping protein synthesis;
- activation of cortisol;
- decreased insulin production.
How to neutralize lactic acid?
Doctors do not have a consensus regarding the removal of lactate from the body. Some experts argue that there is no way to remove the compound from the body. They say that the only thing that can be done is to reduce the discomfort:
- proper balanced nutrition;
- consumption of fresh fruits and berries, rich in antioxidants;
- drinking herbal teas and decoctions, in particular those based on nettle, hawthorn and rose hips;
- drinking plenty of fluids both during and after physical activity;
- taking hot baths - the water must be hot: this will help speed up the blood circulation process;
- using a warming ointment;
- adherence to a rest regime - healthy sleep contributes to the restoration of the body;
- sauna and bathhouse.
The following can help reduce discomfort: a contrast shower, massage, drinking a herbal decoction immediately after training and introducing a large amount of vegetables, fruits and herbs into your daily diet.
There are certain rules about what is not recommended to do. For example, experts do not advise consuming fast carbohydrates and alcoholic drinks, since they significantly slow down the process of muscle tissue restoration. You should not use painkillers, as they inhibit the process of removing lactic acid.
If you do not want to feel muscle pain after training, you must stop consuming the above-mentioned products in advance. And before you start playing sports, it is very important to warm up thoroughly and stretch after completing your workout. It is not recommended to suddenly change the training program and not to be particularly zealous unless you have enough experience for this.
How to rid yourself of lactic acid? Practical recommendations
A large number of beginners in the gym almost constantly experience discomfort from training, which leads to a burning sensation in the muscles. But if you remember simple tips (which come next), the level of comfort of the exercise will increase, and discomfort will be minimized. So, in order for the accumulation of lactic acid to occur in small quantities, you need to:
- Start your workout with a warm-up. It should be light and warming;
- Stretch the muscles after each repetition of the exercise/after completing a set;
- Increase the weight of the load gradually as the muscles are ready for it;
- Don’t skip workouts so that your muscles get used to the load;
- Recover fully after every workout.
That's all. If you follow simple tips and take into account the information provided, you can easily learn how to manage the most powerful catalyst for training intensity.
Beneficial properties of lactic acid
Lactic acid, as mentioned above, provides the body with the energy resource it needs. It takes part in metabolic processes and in the production of glucose. This organic compound is required for the proper functioning of the heart muscle, the proper functioning of the nervous system, brain and a list of other organs.
Lactate is included in cosmetic products used to remove cuticles. At the same time, it does not have any effect on ordinary skin, but acts exclusively on its keratinized layers. Due to these features, products containing the substance in question are also used to remove calluses and warts.
In addition, lactate has a beneficial effect on hair condition. Thanks to it, they become softer and more manageable, and acquire a beautiful healthy shine. The product works well with both dry and normal hair. Leave the mask with lactate on the hair for a period of time, after which it is washed off with warm water.
Lactic acid is used to prolong skin youth. Daily washing with sour milk helps cleanse the skin and increase its elasticity.
Harm of lactic acid and contraindications to its use
An excess of any substance in the human body is not normal and is of no benefit. Lactate in excess has a negative effect on the condition of the blood: it changes its composition and leads to the development of lactic acidosis. As a result of the disease, the pH level in the body sharply decreases, which leads to disruption of the functioning of almost all organs.
However, it is worth noting that such a disease will not occur even with the most intense training - it usually accompanies leukemia, diabetes, acute blood loss and sepsis.
Areas of application of lactic acid
Food industry
First of all, lactic acid is widely used in the food industry. In food production it is known under the index E270. The compound is used both as an oxidizing agent and as a preservative. Thanks to lactic acid, the shelf life of food products is significantly increased: during long-term storage, products do not acquire an unpleasant odor or taste.
Lactate as a food additive is approved for use in all countries.
You can find lactic acid in the following products:
- sweets;
- juices and carbonated drinks;
- vegetable-based sauces;
- beer;
- canned food – both vegetables and meat;
- vegetable fats;
- alcoholic drinks;
- cheese and dairy products;
- semi-finished fish products.
Lactic acid can not only extend their shelf life, but also improve taste, color, consistency, and also protect against bacteria.
Cosmetology
In modern cosmetology, acid-based products are very popular. Products based on lactic acid are especially popular. It is of safe natural origin, which means it is safer for humans.
Thus, acid helps exfoliate dead cells, narrow pores, whiten age spots and improve facial skin tone, eliminate imperfections and inflammation, and get rid of scars.
Lactic acid is popular in gynecological products. It is often used as an acidity regulator in intimate hygiene products.
Pharmaceuticals
The safety of lactic acid allows its inclusion in medicinal preparations. The compound used in medicines is characterized by high purity and is produced exclusively on high-quality equipment with additional protection against the inclusion of iron impurities.
Among pharmaceutical preparations, products that help get rid of fungus of the skin and nail plate are especially popular. Lactate is often included in antimicrobial agents used to maintain gastric microflora. The substance helps relax the gastric and intestinal sphincters and prevent the development of pathogenic microflora.
Veterinary
In veterinary medicine, lactic acid is used as an antifermentation product used to treat gastric diseases. The properties of the compound are used to prevent the development of respiratory diseases. Lactic acid products are given to horses, ruminants, foxes and cattle to treat stomach problems.
In poultry farms, the compound is used to increase egg production and acid strength. It is used as an additional metabolite.
Application
Lactic acid is used primarily in three areas: food industry, polymer production and other industrial purposes.
In the food industry, lactic acid is used as a preservative and acidulant. Due to the fact that its salts are highly soluble in water, they can also be used in products where the pH value is important. Lactic acid and its salts are used in drinks, candy, meat products and sauces. Calcium lactate is added to foods as a source of calcium.
In the polymer industry, polylactide is obtained from lactic acid. It is produced from lactide by ring-opening polymerization. Lactide itself is obtained by condensation of lactic acid.
Lactic acid is also used in metal coating, cosmetics, textiles and leather industries. Its esters are used in the production of paints and inks, electronics and metal cleaning.
Cosmetics containing lactic acid
Most often, lactic acid is included in shampoos and other hair products, as well as in peelings. Acid helps improve the quality of hair: hair acquires a healthy shine, becomes softer and more manageable. They become easy to comb and style.
As part of peelings, lactic acid helps exfoliate dead skin cells, improve complexion, remove age spots and improve skin structure. Lactic acid helps tighten and cleanse pores.
Peeling with lactic acid at home
Using homemade acid peeling leads to the following effect:
- removing oily shine;
- reducing the intensity of redness and inflammatory processes;
- smoothing out shallow wrinkles;
- improvement of facial relief;
- removing acne spots;
- eliminating unwanted pigmentation;
- the skin becomes fresher.
It is not recommended to use lactic acid-based peels during lactation, pregnancy, malignant neoplasms, a tendency to form scar tissue, spider veins on the face and overly sensitive skin.
To prepare the peeling, you will need, in fact, lactate - 0.5 g and purified water - 9.5 g. Cosmetologists recommend taking care of a product to neutralize lactic acid. It can be prepared from soda and distilled water mixed in equal proportions.
For easier peeling, you can use the following recipe:
- fat sour cream – 1 tbsp;
- yolk – 1 pc.;
- crushed oatmeal – 1 tsp;
- lemon juice – 1 tsp.
Before starting the procedure, both at home and in a salon, it is recommended to test the degree of sensitivity of the skin to acid.
Before starting the procedure itself, it is necessary to thoroughly cleanse the skin of fatty contaminants and makeup residues. A tonic is best suited for these purposes. It is best to apply peeling with a brush, but in the absence of one, you can also use ordinary cotton pads. You need to start applying from the forehead, gradually moving down to the chin. Immediately after completing the procedure, you must apply a moisturizing mask to your face.
Why is an athlete's lactate measured?
In professional sports, lactate is used as an indicator of load intensity. Lactate levels increase with increasing intensity, so the amount of lactate in the blood determines the type of training and calculates intensity zones. Blood lactate concentration in different intensity zones:
- in the aerobic zone - 2 mmol/l
- in the transit zone - 4-10 mmol/l
- in the anaerobic zone - more than 10 mmol/l
By conducting a lactate test, you can most accurately determine the athlete's TNA or lactate threshold. A lactate level of 4 mmol/L is considered the approximate TANO level - the point at which the body switches from a predominantly aerobic to anaerobic mode. Many amateur athletes train to the point of exhaustion, mistakenly believing that the more intense the training, the better the result. Fatigue and lack of coordination are usually a sign of high blood lactate levels. Frequent training at high intensity not only does not bring results, but also worsens physical fitness and leads to overtraining .
Measuring blood lactate levels. Source: trackanalysis.co.uk
Knowing your lactate threshold, you can build an effective training plan and train at the right intensity. For example: training at the lactate threshold level (that is, with a lactate concentration in the blood of about 4 mmol/l) develops the athlete’s threshold speed and increases PANO. Training at a lactate level of 0.5-1.5 mmol/L is considered restorative, and at a lactate concentration of 2-4 mmol/L aerobic training is performed, which forms the main part of an endurance athlete's training plan.
During the training cycle, the effectiveness of the athlete’s training is monitored by lactate levels. If over time the lactate level decreases under the same loads, this indicates an increase in athletic fitness; if it increases, this indicates a decline in fitness. In the latter case, the training plan is adjusted.
Peeling with lactic acid - reviews
Alexandra, 30 years old
Lactic acid for the face is a product that I use regularly in the autumn-winter period and in the spring. Acid peels cannot be done during solar activity. Peeling with lactic acid on a regular basis refreshes the skin, removes dead layers of the epidermis and helps add freshness. I love using this foot product to remove hard skin from my feet.
Angela, 33 years old
I decided to try peeling with lactic acid because of problematic facial skin – I was struggling with acne. I was very pleased with the result, the skin is smoothed, the number of acne is noticeably reduced. It’s a little uncomfortable the next day, the skin peels, but it only lasts a day. I use low concentration acids. Lactic acid for the face is the best product for my skin at the moment. In addition to reducing acne, the skin is rejuvenated and looks much fresher.
Elena, 41 years old
In my opinion, lactic acid peeling is the best procedure for skin rejuvenation! Despite the fact that this procedure is considered by cosmetologists to be one of the most gentle, the result exceeded all my expectations! Age wrinkles are smoothed out, and with regular peelings, a cumulative effect is felt! I recommend to everyone!
Why does it cause muscle pain?
The more intensely an athlete trains, the more his body needs easily accessible energy - and the more actively the body produces lactic acid when processing carbohydrates. However, its excessive accumulation can cause a characteristic burning sensation and mild pain in the muscles, interfering with exercise¹.
About 90% of lactic acid is utilized within an hour after the end of the workout - that is, it is eliminated from the body and cannot cause pain the next day. Despite this, lactic acid lowers the pH level in the muscles - which affects their biochemistry.
Let us also note that the higher the load and the lower the level of physical fitness of a person, the more lactic acid is produced - but the reason lies not in genetic differences, but in the body’s ability to accumulate (and use) a sufficient amount of glycogen.
Is pain related to weight gain?
Some athletes believe that lactic acid helps stimulate testosterone production - and use special training strategies to increase it. First of all, we are talking about pumping training and performing exercises in a pyramid scheme or to failure.
This is partly true. High lactic acid levels and low pH do increase the production of growth hormone - but not in the amount that will fundamentally change the metabolism of a beginner². In other words, this technique is only suitable for professionals.
