Lactic acid

Lactic acid is an organic acid. It has a molecular formula CH3CH(OH)CO2H. It is white in solid state and it is extremely soluble in water. Solubility is so high that 1 part of lactic acid can dissolve 12 parts of water. While in liquid state (dissolved state) it is a colorless solution. Production includes both artificial synthesis as well as natural sources. Lactic acid is an alpha-hydroxy acid (AHA) due to the presence of carboxyl group adjacent to the hydroxyl group. It is used as a synthetic intermediate in many organic synthesis industries and in various biochemical industries. The conjugate base of lactic acid is called lactate.

In solution, it can ionize a proton from the carboxyl group, producing the lactate ion CH
3
CH(OH)CO
2
. Compared to acetic acid, its pKa is 1 unit less, meaning lactic acid is ten times more acidic than acetic acid. This higher acidity is the consequence of the intramolecular hydrogen bonding between the α-hydroxyl and the carboxylate group. Lactic acid is chiral, consisting of two enantiomers. One is known as L-(+)-lactic acid or (S)-lactic acid and the other, its mirror image, is D-(−)-lactic acid or (R)-lactic acid. A mixture of the two in equal amounts is called DL-lactic acid, or racemic lactic acid. Lactic acid is hygroscopic. DL-lactic acid is miscible with water and with ethanol above its melting point, which is around 17 or 18 °C. D-lactic acid and L-lactic acid have a higher melting point.

In animals, L-lactate is constantly produced from pyruvate via the enzyme lactate dehydrogenase (LDH) in a process of fermentation during normal metabolism and exercise. It does not increase in concentration until the rate of lactate production exceeds the rate of lactate removal, which is governed by a number of factors, including monocarboxylate transporters, concentration and isoform of LDH, and oxidative capacity of tissues. The concentration of blood lactate is usually 1–2 mM at rest, but can rise to over 20 mM during intense exertion and as high as 25 mM afterward.[5][6] In addition to other biological roles, L-lactic acid is the primary endogenous agonist of hydroxycarboxylic acid receptor 1 (HCA1), which is a Gi/o-coupled G protein-coupled receptor (GPCR).[7][8]

In industry, lactic acid fermentation is performed by lactic acid bacteria, which convert simple carbohydrates such as glucose, sucrose, or galactose to lactic acid. These bacteria can also grow in the mouth; the acid they produce is responsible for the tooth decay known as caries.[9][10][11][12] In medicine, lactate is one of the main components of lactated Ringer's solution and Hartmann's solution. These intravenous fluids consist of sodium and potassium cations along with lactate and chloride anions in solution with distilled water, generally in concentrations isotonic with human blood. It is most commonly used for fluid resuscitation after blood loss due to trauma, surgery, or burns.

Lactic acid
Skeletal formula of L-lactic acid
L-Lactic acid molecule spacefill
Names
Preferred IUPAC name
2-Hydroxypropanoic acid[1]
Other names
Lactic acid[1]
Milk acid
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.000.017
E number E270 (preservatives)
UNII
Properties
C3H6O3
Molar mass 90.078 g·mol−1
Melting point 18°C
Boiling point 122 °C (252 °F; 395 K) @ 15 mmHg
Acidity (pKa) 3.86,[2] 15.1[3]
Thermochemistry
1361.9 kJ/mol, 325.5 kcal/mol, 15.1 kJ/g, 3.61 kcal/g
Pharmacology
G01AD01 (WHO) QP53AG02 (WHO)
Hazards
GHS pictograms GHS-pictogram-acid[4]
H315, H318[4]
P280, P305+351+338[4]
Related compounds
Other anions
lactate
acetic acid
glycolic acid
propionic acid
3-hydroxypropanoic acid
malonic acid
butyric acid
hydroxybutyric acid
Related compounds
1-propanol
2-propanol
propionaldehyde
acrolein
sodium lactate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

History

Swedish chemist Carl Wilhelm Scheele was the first person to isolate lactic acid in 1780 from sour milk. The name reflects the lact- combining form derived from the Latin word lac, which means milk. In 1808, Jöns Jacob Berzelius discovered that lactic acid (actually L-lactate) also is produced in muscles during exertion.[13] Its structure was established by Johannes Wislicenus in 1873.

In 1856, the role of Lactobacillus in the synthesis of lactic acid. Lactic acid was discovered by Louis Pasteur. And hence this pathway was used for the commercial by the German pharmacy Boehringer Ingelheim in 1895.

In 2006, global production of lactic acid reached 275,000 metric tons with an average annual growth of 10%.[14]

Production

Lactic acid is produced industrially by bacterial fermentation of carbohydrates (sugar, starch) or by chemical synthesis from acetaldehyde, that is available from coal or crude oil.[15] In 2009 lactic acid was produced predominantly (70–90%)[16] by fermentation. Production of racemic lactic acid consisting of a 1:1 mixture of D and L stereoisomers, or of mixtures with up to 99.9% L-lactic acid, is possible by microbial fermentation. Industrial scale production of D-lactic acid by fermentation is possible, but much more challenging.

Fermentative production

Fermented milk products are obtained industrially by fermentation of milk or whey by Lactobacillius species: Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus delbrueckii subsp. bulgaricus (Lactobacillus bulgaricus) and Lactobacillus helveticus, and furthermore Streptococcus salivarius subsp. thermophilus (Streptococcus thermophilus) and Lactococcus lactis.

As a starting material for industrial production of lactic chemistry, that is applied for chemical synthesis, almost any carbohydrate source containing C5/C6 sugars could be used. Pure sucrose, glucose from starch, raw sugar beet juice are frequently applied.[17] Lactic acid producing bacteria could be divided in two classes: homofermentative bacteria like Lactobacillus casei and Lactococcus lactis, producing two moles of lactate from one mole of glucose, heterofermentative species producing one mole of lactate from one mole of glucose as well as carbon dioxide and acetic acid/ethanol.[18]

Chemical production

Racemic lactic acid is produced in industry by addition of hydrogen cyanide to acetaldehyde and subsequent hydrolysis of forming lactonitrile. Hydrolysis performed by hydrochloric acid and ammonium chloride forms as a by-product. Japanese concern Musashino is one of the last big manufactures of lactic acid by this route.[19] Synthesis of both racemic and enantiopure lactic acids is also possible from other starting materials (vinyl acetate, glycerol, etc.) by application of catalytic procedures.[20]

Biology

Molecular biology

L-lactic acid is the primary endogenous agonist of hydroxycarboxylic acid receptor 1 (HCA1), a Gi/o-coupled G protein-coupled receptor (GPCR).[7][8]

Exercise and lactate

During power exercises such as sprinting, when the rate of demand for energy is high, glucose is broken down and oxidized to pyruvate, and lactate is then produced from the pyruvate faster than the body can process it, causing lactate concentrations to rise. The production of lactate is beneficial for NAD+ regeneration (pyruvate is reduced to lactate while NADH is oxidized to NAD+), which is used up in oxidation of glyceraldehyde 3-phosphate during production of pyruvate from glucose, and this ensures that energy production is maintained and exercise can continue. (During intense exercise, the respiratory chain cannot keep up with the amount of hydrogen ions that join to form NADH, and cannot regenerate NAD+ quickly enough.) In volant animals such as birds and bats, lactic acid may build up in the pectoral muscles.[21]

The resulting lactate can be used in two ways:

However, lactate is continually formed even at rest and during moderate exercise. Some causes of this are metabolism in red blood cells that lack mitochondria, and limitations resulting from the enzyme activity that occurs in muscle fibers having a high glycolytic capacity.[22]

In 2004 Robergs et al. maintained that lactic acidosis during exercise is a "construct" or myth, pointing out that part of the H+ comes from ATP hydrolysis (ATP4− + H2O → ADP3− + HPO2−
4
+ H+), and that reducing pyruvate to lactate (pyruvate + NADH + H+ → lactate + NAD+) actually consumes H+.[23] Lindinger et al.[24] countered that they had ignored the causative factors of the increase in [H+]. After all, the production of lactate from a neutral molecule must increase [H+] to maintain electroneutrality. The point of Robergs's paper, however, was that lactate is produced from pyruvate, which has the same charge. It is pyruvate production from neutral glucose that generates H+:

    C6H12O6 + 2 NAD+ + 2 ADP3− + 2 HPO2−
4
CH
3
COCO
2
+ 2 H+ + 2 NADH + 2 ATP4− + 2 H2O
Subsequent lactate production absorbs these protons:
CH
3
COCO
2
+ 2 H+ + 2 NADH
CH
3
CH(OH)CO
2
+ 2 NAD+
Overall:
C6H12O6 + 2 NAD+ + 2 ADP3− + 2 HPO2−
4
CH
3
COCO
2
+ 2 H+ + 2 NADH + 2 ATP4− + 2 H2O
CH
3
CH(OH)CO
2
+ 2 NAD+ + 2 ATP4− + 2 H2O

Although the reaction glucose → 2 lactate + 2 H+ releases two H+ when viewed on its own, the H+ are absorbed in the production of ATP. On the other hand, the absorbed acidity is released during subsequent hydrolysis of ATP: ATP4− + H2O → ADP3− + HPO2−
4
+ H+. So once the use of the ATP is included, the overall reaction is

C6H12O6 → 2 CH
3
COCO
2
+ 2 H+

The generation of CO2 during respiration also causes an increase in [H+].

Brain metabolism

Although glucose is usually assumed to be the main energy source for living tissues, there are some indications that it is lactate, and not glucose, that is preferentially metabolized by neurons in the brain of several mammalian species (the notable ones being mice, rats, and humans).[25][26] According to the lactate-shuttle hypothesis, glial cells are responsible for transforming glucose into lactate, and for providing lactate to the neurons.[27][28] Because of this local metabolic activity of glial cells, the extracellular fluid immediately surrounding neurons strongly differs in composition from the blood or cerebrospinal fluid, being much richer with lactate, as was found in microdialysis studies.[25]

Some evidence suggests that lactate is important at early stages of development for brain metabolism in prenatal and early postnatal subjects, with lactate at these stages having higher concentrations in body liquids, and being utilized by the brain preferentially over glucose.[25] It was also hypothesized that lactate may exert a strong action over GABAergic networks in the developing brain, making them more inhibitory than it was previously assumed,[29] acting either through better support of metabolites,[25] or alterations in base intracellular pH levels,[30][31] or both.[32]

Studies of brain slices of mice show that beta-hydroxybutyrate, lactate, and pyruvate act as oxidative energy substrates, causing an increase in the NAD(P)H oxidation phase, that glucose was insufficient as an energy carrier during intense synaptic activity and, finally, that lactate can be an efficient energy substrate capable of sustaining and enhancing brain aerobic energy metabolism in vitro.[33] The study, "provides novel data on biphasic NAD(P)H fluorescence transients, an important physiological response to neural activation that has been reproduced in many studies and that is believed to originate predominately from activity-induced concentration changes to the cellular NADH pools."[34]

Blood testing

Blood values sorted by mass and molar concentration
Reference ranges for blood tests, comparing lactate content (shown in violet at center-right) to other constituents in human blood.

Blood tests for lactate are performed to determine the status of the acid base homeostasis in the body. Blood sampling for this purpose is often by arterial blood sampling (even if it is more difficult than venipuncture), because lactate differs substantially between arterial and venous levels, and the arterial level is more representative for this purpose.

Reference ranges
Lower limit Upper limit Unit
Venous 4.5[35] 19.8[35] mg/dL
0.5[36] 2.2[36] mmol/L
Arterial 4.5[35] 14.4[35] mg/dL
0.5[36] 1.6[36] mmol/L

During childbirth, lactate levels in the fetus can be quantified by fetal scalp blood testing.

Polymer precursor

Two molecules of lactic acid can be dehydrated to the lactone lactide. In the presence of catalysts lactide polymerize to either atactic or syndiotactic polylactide (PLA), which are biodegradable polyesters. PLA is an example of a plastic that is not derived from petrochemicals.

Pharmaceutical and cosmetic applications

Lactic acid is also employed in pharmaceutical technology to produce water-soluble lactates from otherwise-insoluble active ingredients. It finds further use in topical preparations and cosmetics to adjust acidity and for its disinfectant and keratolytic properties.

Foods

Lactic acid is found primarily in sour milk products, such as koumiss, laban, yogurt, kefir, and some cottage cheeses. The casein in fermented milk is coagulated (curdled) by lactic acid. Lactic acid is also responsible for the sour flavor of sourdough bread.

In lists of nutritional information lactic acid might be included under the term "carbohydrate" (or "carbohydrate by difference") because this often includes everything other than water, protein, fat, ash, and ethanol.[37] If this is the case then the calculated food energy may use the standard 4 calories per gram that is often used for all carbohydrates. But in some cases lactic acid is ignored in the calculation.[38] The energy density of lactic acid is 362 kilocalories (1,510 kJ) per 100 g.[39]

In beer brewing some styles of beer (sour beer) purposely contain lactic acid. Most commonly this is produced naturally by various strains of bacteria. These bacteria ferment sugars into acids, unlike yeast, which ferment sugar into ethanol. One such style are Belgian Lambics. After cooling the wort, yeast and bacteria are allowed to “fall” into the open fermenters. Most brewers of more common beer styles would ensure no such bacteria are allowed to enter the fermenter. Other sour styles of beer include Berliner weisse, Flanders red and American wild ale.[40][41]

In winemaking, a bacterial process, natural or controlled, is often used to convert the naturally present malic acid to lactic acid, to reduce the sharpness and for other flavor-related reasons. This malolactic fermentation is undertaken by the family of lactic acid bacteria.

While not normally found in significant quantities in fruit, lactic acid is the primary organic acid in akebia fruit, making up 2.12% of the juice.[42]

As a food additive it is approved for use in the EU,[43] USA[44] and Australia and New Zealand;[45] it is listed by its INS number 270 or as E number E270. Lactic acid is used as a food preservative, curing agent, and flavoring agent.[46] It is an ingredient in processed foods and is used as a decontaminant during meat processing.[47] Lactic acid is produced commercially by fermentation of carbohydrates such as glucose, sucrose, or lactose, or by chemical synthesis.[46] Carbohydrate sources include corn, beets, and cane sugar.[48]

Forgery

Lactic acid has historically been used to assist with the erasure of inks from official papers to be modified during forgery.[49]

See also

References

  1. ^ a b "CHAPTER P-6. Applications to Specific Classes of Compounds". Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 748. doi:10.1039/9781849733069-00648. ISBN 978-0-85404-182-4.
  2. ^ Dawson RM, et al. (1959). Data for Biochemical Research. Oxford: Clarendon Press.
  3. ^ Silva AM, Kong X, Hider RC (October 2009). "Determination of the pKa value of the hydroxyl group in the alpha-hydroxycarboxylates citrate, malate and lactate by 13C NMR: implications for metal coordination in biological systems". Biometals. 22 (5): 771–8. doi:10.1007/s10534-009-9224-5. PMID 19288211.
  4. ^ a b c Sigma-Aldrich Co., DL-Lactic acid.
  5. ^ "Lactate Profile". UC Davis Health System, Sports Medicine and Sports Performance. Retrieved 23 November 2015.
  6. ^ Goodwin ML, Harris JE, Hernández A, Gladden LB (July 2007). "Blood lactate measurements and analysis during exercise: a guide for clinicians". Journal of Diabetes Science and Technology. 1 (4): 558–69. doi:10.1177/193229680700100414. PMC 2769631. PMID 19885119.
  7. ^ a b Offermanns S, Colletti SL, Lovenberg TW, Semple G, Wise A, IJzerman AP (June 2011). "International Union of Basic and Clinical Pharmacology. LXXXII: Nomenclature and Classification of Hydroxy-carboxylic Acid Receptors (GPR81, GPR109A, and GPR109B)". Pharmacological Reviews. 63 (2): 269–90. doi:10.1124/pr.110.003301. PMID 21454438.
  8. ^ a b S Offermanns, SL Colletti, AP IJzerman, TW Lovenberg, G Semple, A Wise, MG Waters. "Hydroxycarboxylic acid receptors". IUPHAR/BPS Guide to Pharmacology. International Union of Basic and Clinical Pharmacology. Retrieved 13 July 2018.CS1 maint: Multiple names: authors list (link)
  9. ^ Badet C, Thebaud NB (2008). "Ecology of lactobacilli in the oral cavity: a review of literature". The Open Microbiology Journal. 2: 38–48. doi:10.2174/1874285800802010038. PMC 2593047. PMID 19088910.
  10. ^ Nascimento MM, Gordan VV, Garvan CW, Browngardt CM, Burne RA (April 2009). "Correlations of oral bacterial arginine and urea catabolism with caries experience". Oral Microbiology and Immunology. 24 (2): 89–95. doi:10.1111/j.1399-302X.2008.00477.x. PMC 2742966. PMID 19239634.
  11. ^ Aas JA, Griffen AL, Dardis SR, Lee AM, Olsen I, Dewhirst FE, Leys EJ, Paster BJ (April 2008). "Bacteria of dental caries in primary and permanent teeth in children and young adults". Journal of Clinical Microbiology. 46 (4): 1407–17. doi:10.1128/JCM.01410-07. PMC 2292933. PMID 18216213.
  12. ^ Caufield PW, Li Y, Dasanayake A, Saxena D (2007). "Diversity of lactobacilli in the oral cavities of young women with dental caries". Caries Research. 41 (1): 2–8. doi:10.1159/000096099. PMC 2646165. PMID 17167253.
  13. ^ Roth SM. "Why does lactic acid build up in muscles? And why does it cause soreness?". Retrieved 23 January 2006.
  14. ^ "NNFCC Renewable Chemicals Factsheet: Lactic Acid". NNFCC.
  15. ^ H. Benninga (1990): "A History of Lactic Acid Making: A Chapter in the History of Biotechnology". Volume 11 of Chemists and Chemistry. Springer, ISBN 0792306252, 9780792306252
  16. ^ Endres H (2009). Technische Biopolymere. München: Hanser-Verlag. p. 103. ISBN 978-3-446-41683-3.
  17. ^ Groot W, van Krieken J, Slekersl O, de Vos S (2010-10-19). Auras R, Lim L, Selke SE, Tsuji H, eds. Chemistry and production of lactic acid, lactide and poly(lactic acid) in Poly(Lactic acid). Hoboken: Wiley. p. 3. ISBN 978-0-470-29366-9.
  18. ^ König H, Fröhlich J (2009). Lactic acid bacteria in Biology of Microorganisms on Grapes, in Must and in Wine. Springer-Verlag. p. 3. ISBN 978-3-540-85462-3.
  19. ^ Westhoff G, Starr JN (2012). "Lactic Acid". Lactic Acids. In: Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. pp. 1–8. doi:10.1002/14356007.a15_097.pub3. ISBN 9783527306732.
  20. ^ Shuklov IA, Dubrovina NV, Kühlein K, Börner A (2016). "Chemo-Catalyzed Pathways to Lactic Acid and Lactates". Advanced Synthesis and Catalysis. 358 (24): 3910–3931. doi:10.1002/adsc.201600768.
  21. ^ Article in "Mammalian Biology"
  22. ^ a b McArdle WD, Katch FI, Katch VL (2010). Exercise Physiology: Energy, Nutrition, and Human Performance. Wolters Kluwer/Lippincott Williams & Wilkins Health. ISBN 978-0-683-05731-7.
  23. ^ Robergs RA, Ghiasvand F, Parker D (September 2004). "Biochemistry of exercise-induced metabolic acidosis" (PDF). American Journal of Physiology. Regulatory, Integrative and Comparative Physiology. 287 (3): R502–16. doi:10.1152/ajpregu.00114.2004. PMID 15308499.
  24. ^ Lindinger MI, Kowalchuk JM, Heigenhauser GJ (September 2005). "Applying physicochemical principles to skeletal muscle acid-base status". American Journal of Physiology. Regulatory, Integrative and Comparative Physiology. 289 (3): R891–4, author reply R904–910. doi:10.1152/ajpregu.00225.2005. PMID 16105823.
  25. ^ a b c d Zilberter Y, Zilberter T, Bregestovski P (September 2010). "Neuronal activity in vitro and the in vivo reality: the role of energy homeostasis". Trends in Pharmacological Sciences. 31 (9): 394–401. doi:10.1016/j.tips.2010.06.005. PMID 20633934.
  26. ^ Wyss MT, Jolivet R, Buck A, Magistretti PJ, Weber B (May 2011). "In vivo evidence for lactate as a neuronal energy source" (PDF). The Journal of Neuroscience. 31 (20): 7477–85. doi:10.1523/JNEUROSCI.0415-11.2011. PMID 21593331.
  27. ^ Gladden LB (July 2004). "Lactate metabolism: a new paradigm for the third millennium". The Journal of Physiology. 558 (Pt 1): 5–30. doi:10.1113/jphysiol.2003.058701. PMC 1664920. PMID 15131240.
  28. ^ Pellerin L, Bouzier-Sore AK, Aubert A, Serres S, Merle M, Costalat R, Magistretti PJ (September 2007). "Activity-dependent regulation of energy metabolism by astrocytes: an update". Glia. 55 (12): 1251–62. doi:10.1002/glia.20528. PMID 17659524.
  29. ^ Holmgren CD, Mukhtarov M, Malkov AE, Popova IY, Bregestovski P, Zilberter Y (February 2010). "Energy substrate availability as a determinant of neuronal resting potential, GABA signaling and spontaneous network activity in the neonatal cortex in vitro". Journal of Neurochemistry. 112 (4): 900–12. doi:10.1111/j.1471-4159.2009.06506.x. PMID 19943846.
  30. ^ Tyzio R, Allene C, Nardou R, Picardo MA, Yamamoto S, Sivakumaran S, Caiati MD, Rheims S, Minlebaev M, Milh M, Ferré P, Khazipov R, Romette JL, Lorquin J, Cossart R, Khalilov I, Nehlig A, Cherubini E, Ben-Ari Y (January 2011). "Depolarizing actions of GABA in immature neurons depend neither on ketone bodies nor on pyruvate". The Journal of Neuroscience. 31 (1): 34–45. doi:10.1523/JNEUROSCI.3314-10.2011. PMID 21209187.
  31. ^ Ruusuvuori E, Kirilkin I, Pandya N, Kaila K (November 2010). "Spontaneous network events driven by depolarizing GABA action in neonatal hippocampal slices are not attributable to deficient mitochondrial energy metabolism". The Journal of Neuroscience. 30 (46): 15638–42. doi:10.1523/JNEUROSCI.3355-10.2010. PMID 21084619.
  32. ^ Khakhalin AS (September 2011). "Questioning the depolarizing effects of GABA during early brain development". Journal of Neurophysiology. 106 (3): 1065–7. doi:10.1152/jn.00293.2011. PMID 21593390.
  33. ^ Ivanov A, Mukhtarov M, Bregestovski P, Zilberter Y (2011). "Lactate Effectively Covers Energy Demands during Neuronal Network Activity in Neonatal Hippocampal Slices". Frontiers in Neuroenergetics. 3: 2. doi:10.3389/fnene.2011.00002. PMC 3092068. PMID 21602909.
  34. ^ Kasischke K (2011). "Lactate fuels the neonatal brain". Frontiers in Neuroenergetics. 3: 4. doi:10.3389/fnene.2011.00004. PMC 3108381. PMID 21687795.
  35. ^ a b c d Blood Test Results – Normal Ranges Bloodbook.Com
  36. ^ a b c d Derived from mass values using molar mass of 90.08 g/mol
  37. ^ "USDA National Nutrient Database for Standard Reference, Release 28 (2015) Documentation and User Guide" (PDF). 2015. p. 13.
  38. ^ For example, in this USDA database entry for yoghurt the food energy is calculated using given coefficients for carbohydrate, fat, and protein. (One must click on "Full report" to see the coefficients.) The calculated value is based on 4.66 grams of carbohydrate, which is exactly equal to the sugars.
  39. ^ Greenfield H, Southgate D (2003). Food Composition Data: Production, Management and Use. Rome: FAO. p. 146. ISBN 9789251049495.
  40. ^ "Brewing With Lactic Acid Bacteria". MoreBeer.
  41. ^ Lambic (Classic Beer Style) – Jean Guinard
  42. ^ Li Li, Xiaohong Yao, Caihong Zhong and Xuzhong Chen (January 2010). "Akebia: A Potential New Fruit Crop in China". HortScience. 45 (1): 4–10.CS1 maint: Multiple names: authors list (link)
  43. ^ "Current EU approved additives and their E Numbers". UK Food Standards Agency. Retrieved 27 October 2011.
  44. ^ "Listing of Food Additives Status Part II". US Food and Drug Administration. Retrieved 27 October 2011.
  45. ^ "Standard 1.2.4 – Labelling of ingredients". Australia New Zealand Food Standards Code. Retrieved 27 October 2011.
  46. ^ a b "Listing of Specific Substances Affirmed as GRAS:Lactic Acid". US FDA. Retrieved 20 May 2013.
  47. ^ "Purac Carcass Applications". Purac. Retrieved 20 May 2013.
  48. ^ "Agency Response Letter GRAS Notice No. GRN 000240". FDA. US FDA. Retrieved 20 May 2013.
  49. ^ Druckerman P (2 October 2016). "If I Sleep for an Hour, 30 People Will Die". The New York Times.

External links

Acids in wine

The acids in wine are an important component in both winemaking and the finished product of wine. They are present in both grapes and wine, having direct influences on the color, balance and taste of the wine as well as the growth and vitality of yeast during fermentation and protecting the wine from bacteria. The measure of the amount of acidity in wine is known as the “titratable acidity” or “total acidity”, which refers to the test that yields the total of all acids present, while strength of acidity is measured according to pH, with most wines having a pH between 2.9 and 3.9. Generally, the lower the pH, the higher the acidity in the wine. However, there is no direct connection between total acidity and pH (it is possible to find wines with a high pH for wine and high acidity). In wine tasting, the term “acidity” refers to the fresh, tart and sour attributes of the wine which are evaluated in relation to how well the acidity balances out the sweetness and bitter components of the wine such as tannins. Three primary acids are found in wine grapes: tartaric, malic and citric acids. During the course of winemaking and in the finished wines, acetic, butyric, lactic and succinic acids can play significant roles. Most of the acids involved with wine are fixed acids with the notable exception of acetic acid, mostly found in vinegar, which is volatile and can contribute to the wine fault known as volatile acidity. Sometimes, additional acids, such as ascorbic, sorbic and sulfurous acids, are used in winemaking.

Anaerobic exercise

Anaerobic exercise is a physical exercise intense enough to cause lactate to form. It is used by athletes in non-endurance sports to promote strength, speed and power and by body builders to build muscle mass. Muscle energy systems trained using anaerobic exercise develop differently compared to aerobic exercise, leading to greater performance in short duration, high intensity activities, which last from mere seconds to up to about 2 minutes. Any activity lasting longer than about two minutes has a large aerobic metabolic component.

Balao-balao

Balao-balao, also known as burong hipon ("pickled shrimp"), is a Filipino dish consisting of cooked rice and whole raw shrimp fermented with salt and angkak (red yeast rice). Depending on the salt content, it is fermented for several days to weeks. The lactobacilli involved in the fermentation process of the rice produces lactic acid which preserves and softens the shrimp.

Biopreservation

Biopreservation is the use of natural or controlled microbiota or antimicrobials as a way of preserving food and extending its shelf life. The biopreservation of food, especially utilizing lactic acid bacteria (LAB) that are inhibitory to food spoilage microbes, has been practiced since early ages, at first unconsciously but eventually with an increasingly robust scientific foundation. Beneficial bacteria or the fermentation products produced by these bacteria are used in biopreservation to control spoilage and render pathogens inactive in food. There are a various modes of action through which microorganisms can interfere with the growth of others such as organic acid production, resulting in a reduction of pH and the antimicrobial activity of the un-dissociated acid molecules, a wide variety of small inhibitory molecules including hydrogen peroxide, etc. It is a benign ecological approach which is gaining increasing attention.

Buttermilk

Buttermilk is a dairy drink. Originally, buttermilk was the liquid left behind after churning butter out of cultured cream. This type of buttermilk is now specifically referred to as traditional buttermilk.

Most modern buttermilk is a fermented dairy product known as cultured buttermilk. It is common in warm climates (e.g., Afghanistan, the Balkans, India, the Middle East, Nepal, Nicaragua, Pakistan, Sri Lanka, Turkey, and the Southern United States) where unrefrigerated fresh milk sours quickly.Buttermilk can be drunk straight, and it can also be used in cooking. Soda bread is a bread in which the acid in buttermilk reacts with the rising agent, sodium bicarbonate, to produce carbon dioxide which acts as the leavening agent. Buttermilk is also used in marination, especially of chicken and pork, whereby the lactic acid helps to tenderize, retain moisture, and allows added flavors to permeate throughout the meat.

Calpis

Calpis (カルピス, Karupisu) is a Japanese uncarbonated soft drink, manufactured by Calpis Co., Ltd. (カルピス株式会社, Karupisu Kabushiki-gaisha), headquartered in Shibuya, Tokyo. Calpis Co. is a subsidiary of Asahi.

The beverage has a light, somewhat milky, and slightly acidic flavor, similar to plain or vanilla flavored yogurt or Yakult. Its ingredients include water, nonfat dry milk and lactic acid, and is produced by lactic acid fermentation.

The drink is sold as a concentrate which is mixed with water or sometimes milk just before consumption. A pre diluted version known as Calpis Water (カルピスウォーター, Karupisu Wōtā), or its carbonated variety, known as Calpis Soda (カルピスソーダ, Karupisu Sōda), are also available. It is also used to flavor kakigōri (shaved ice) and as a mixer for cocktails and chūhai.

It was first marketed on July 7, 1919. It quickly became popular in pre war Japan, as its concentrated form meant it kept well without refrigeration. The polka dot packaging used to be white dots against a blue background until the colours were inverted in 1953. It was originally themed on the Milky Way, which is in reference to the Japanese festival of Tanabata on July 7, a traditional observation seen as the start of the summer.

Fermentation

Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In the context of food production, it may more broadly refer to any process in which the activity of microorganisms brings about a desirable change to a foodstuff or beverage. The science of fermentation is known as zymology.

In microorganisms, fermentation is the primary means of producing ATP by the degradation of organic nutrients anaerobically. Humans have used fermentation to produce foodstuffs and beverages since the Neolithic age. For example, fermentation is used for preservation in a process that produces lactic acid found in such sour foods as pickled cucumbers, kimchi, and yogurt, as well as for producing alcoholic beverages such as wine and beer. Fermentation occurs within the gastrointestinal tracts of all animals, including humans.

Lactic acid bacteria

Lactic acid bacteria (LAB) are an order of gram-positive, low-GC, acid-tolerant, generally nonsporulating, nonrespiring, either rod-shaped (bacilli) or spherical (cocci) bacteria that share common metabolic and physiological characteristics. These bacteria, usually found in decomposing plants and milk products, produce lactic acid as the major metabolic end product of carbohydrate fermentation. This trait has, throughout history, linked LAB with food fermentations, as acidification inhibits the growth of spoilage agents. Proteinaceous bacteriocins are produced by several LAB strains and provide an additional hurdle for spoilage and pathogenic microorganisms. Furthermore, lactic acid and other metabolic products contribute to the organoleptic and textural profile of a food item. The industrial importance of the LAB is further evidenced by their generally recognized as safe (GRAS) status, due to their ubiquitous appearance in food and their contribution to the healthy microflora of human mucosal surfaces. The genera that comprise the LAB are at its core Lactobacillus, Leuconostoc, Pediococcus, Lactococcus, and Streptococcus, as well as the more peripheral Aerococcus, Carnobacterium, Enterococcus, Oenococcus, Sporolactobacillus, Tetragenococcus, Vagococcus, and Weissella; these belong to the order Lactobacillales.

Lactic acid fermentation

Lactic acid fermentation is a metabolic process by which glucose and other six-carbon sugars (also, disaccharides of six-carbon sugars, e.g. sucrose or lactose) are converted into cellular energy and the metabolite lactate, which is lactic acid in solution. It is an anaerobic fermentation reaction that occurs in some bacteria and animal cells, such as muscle cells.If oxygen is present in the cell, many organisms will bypass fermentation and undergo cellular respiration; however, facultative anaerobic organisms will both ferment and undergo respiration in the presence of oxygen. Sometimes even when oxygen is present and aerobic metabolism is happening in the mitochondria, if pyruvate is building up faster than it can be metabolized, the fermentation will happen anyway.

Lactate dehydrogenase catalyzes the interconversion of pyruvate and lactate with concomitant interconversion of NADH and NAD+.

In homolactic fermentation, one molecule of glucose is ultimately converted to two molecules of lactic acid. Heterolactic fermentation, in contrast, yields carbon dioxide and ethanol in addition to lactic acid, in a process called the phosphoketolase pathway.

Lactobacillus

Lactobacillus is a genus of Gram-positive, facultative anaerobic or microaerophilic, rod-shaped, non-spore-forming bacteria. They are a major part of the lactic acid bacteria group (i.e., they convert sugars to lactic acid). In humans, they constitute a significant component of the microbiota at a number of body sites, such as the digestive system, urinary system, and genital system. In women of European ancestry, Lactobacillus species are normally a major part of the vaginal microbiota. Lactobacillus forms biofilms in the vaginal and gut microbiota, allowing them to persist during harsh environmental conditions and maintain ample populations. Lactobacillus exhibits a mutualistic relationship with the human body, as it protects the host against potential invasions by pathogens, and in turn, the host provides a source of nutrients. Lactobacillus is the most common probiotic found in food such as yogurt, and it is diverse in its application to maintain human well-being, as it can help treat diarrhea, vaginal infections, and skin disorders such as eczema.

Lactococcus lactis

Lactococcus lactis is a Gram-positive bacterium used extensively in the production of buttermilk and cheese, but has also become famous as the first genetically modified organism to be used alive for the treatment of human disease. L. lactis cells are cocci that group in pairs and short chains, and, depending on growth conditions, appear ovoid with a typical length of 0.5 - 1.5 µm. L. lactis does not produce spores (nonsporulating) and are not motile (nonmotile). They have a homofermentative metabolism, meaning they produce lactic acid from sugars. They've also been reported to produce exclusive L-(+)-lactic acid. However, reported D-(−)-lactic acid can be produced when cultured at low pH. The capability to produce lactic acid is one of the reasons why L. lactis is one of the most important microorganisms in the dairy industry. Based on its history in food fermentation, L. lactis has generally recognized as safe (GRAS) status with few case reports of being an opportunistic pathogen.L. lactis is of crucial importance for manufacturing dairy products, such as buttermilk and cheeses. When L. lactis ssp. lactis is added to milk, the bacterium uses enzymes to produce energy molecules (ATP), from lactose. The byproduct of ATP energy production is lactic acid. The lactic acid produced by the bacterium curdles the milk that then separates to form curds, which are used to produce cheese. Other uses that have been reported for this bacterium include the production of pickled vegetables, beer or wine, some breads, and other fermented foodstuffs, such as soymilk kefir, buttermilk, and others. L. lactis is one of the best characterized low GC Gram positive bacteria with detailed knowledge on genetics, metabolism and biodiversity.L. lactis is mainly isolated from either the dairy environment or plant material. Dairy isolates are suggested to have evolved from plant isolates through a process in which genes without benefit in the rich medium milk were either lost or down-regulated. This process, also called genome erosion or reductive evolution is also described in several other lactic acid bacteria. The proposed transition from the plant to the dairy environment was reproduced in the laboratory through experimental evolution of a plant isolate that was cultivated in milk for a prolonged period. Consistent with the results from comparative genomics (see references above) this resulted in L. lactis losing or down-regulating genes which are dispensable in milk and the up-regulation of peptide transport.Hundreds of novel small RNAs were identified by Meulen et al. in the genome of L. lactis MG1363. One of them: LLnc147 was shown to be involved carbon uptake and metabolism.

Malolactic fermentation

Malolactic fermentation (also known as malolactic conversion or MLF) is a process in winemaking in which tart-tasting malic acid, naturally present in grape must, is converted to softer-tasting lactic acid. Malolactic fermentation is most often performed as a secondary fermentation shortly after the end of the primary fermentation, but can sometimes run concurrently with it. The process is standard for most red wine production and common for some white grape varieties such as Chardonnay, where it can impart a "buttery" flavor from diacetyl, a byproduct of the reaction.The fermentation reaction is undertaken by the family of lactic acid bacteria (LAB); Oenococcus oeni, and various species of Lactobacillus and Pediococcus. Chemically, malolactic fermentation is a decarboxylation, which means carbon dioxide is liberated in the process.The primary function of all these bacteria is to convert one of the two major grape acids found in wine called L-malic acid, to another type of acid, L+ lactic acid. This can occur naturally. However, in commercial winemaking, malolactic conversion typically is initiated by an inoculation of desirable bacteria, usually O. oeni. This prevents undesirable bacterial strains from producing "off" flavors. Conversely, commercial winemakers actively prevent malolactic conversion when it is not desired, such as with fruity and floral white grape varieties such as Riesling and Gewürztraminer, to maintain a more tart or acidic profile in the finished wine.Malolactic fermentation tends to create a rounder, fuller mouthfeel. Malic acid is typically associated with the taste of green apples, while lactic acid is richer and more buttery tasting. Grapes produced in cool regions tend to be high in acidity, much of which comes from the contribution of malic acid. Malolactic fermentation generally enhances the body and flavor persistence of wine, producing wines of greater palate softness. Many winemakers also feel that better integration of fruit and oak character can be achieved if malolactic fermentation occurs during the time the wine is in barrel.A wine undergoing malolactic conversion will be cloudy because of the presence of bacteria, and may have the smell of buttered popcorn, the result of the production of diacetyl. The onset of malolactic fermentation in the bottle is usually considered a wine fault, as the wine will appear to the consumer to still be fermenting (as a result of CO2 being produced). However, for early Vinho Verde production, this slight effervesce was considered a distinguishing trait, though Portuguese wine producers had to market the wine in opaque bottles because of the increase in turbidity and sediment that the "in-bottle MLF" produced. Today, most Vinho Verde producers no longer follow this practice and instead complete malolactic fermentation prior to bottling with the slight sparkle being added by artificial carbonation.

Muscle fatigue

Muscle fatigue is the decline in ability of a muscle to generate force. It can be a result of vigorous exercise but abnormal fatigue may be caused by barriers to or interference with the different stages of muscle contraction. There are two main causes of muscle fatigue: the limitations of a nerve’s ability to generate a sustained signal (neural fatigue); and the reduced ability of the muscle fiber to contract (metabolic fatigue).

Muscle weakness

Muscle weakness is a lack of muscle strength. The causes are many and can be divided into conditions that have either true or perceived muscle weakness. True muscle weakness is a primary symptom of a variety of skeletal muscle diseases, including muscular dystrophy and inflammatory myopathy. It occurs in neuromuscular junction disorders, such as myasthenia gravis. Muscle weakness can also be caused by low levels of potassium and other electrolytes within muscle cells. It can be temporary or long-lasting (from seconds or minutes to months or years). The term myasthenia is from my- from Greek μυο meaning "muscle" + -asthenia ἀσθένεια meaning "weakness".

N-Acetylmuramic acid

N-Acetylmuramic acid, or MurNAc, is the ether of lactic acid and N-acetylglucosamine with a chemical formula of C11H19NO8. It is part of a biopolymer in the bacterial cell wall, which is built from alternating units of N-acetylglucosamine (GlcNAc) and N-acetylmuramic acid (MurNAc), cross-linked with oligopeptides at the lactic acid residue of MurNAc. This layered structure is called peptidoglycan.

MurNAc is a monosaccharide derivative of N-acetylglucosamine.

Polylactic acid

Poly(lactic acid) or polylactic acid or polylactide (PLA) is a biodegradable and bioactive thermoplastic aliphatic polyester derived from renewable biomass, typically from fermented plant starch such as from corn, cassava, sugarcane or sugar beet pulp. In 2010, PLA had the second highest consumption volume of any bioplastic of the world.The name "polylactic acid" does not comply with IUPAC standard nomenclature, and is potentially ambiguous or confusing, because PLA is not a polyacid (polyelectrolyte), but rather a polyester.

Rosmarinic acid

Rosmarinic acid is a chemical compound found in a variety of plants.

Sourdough

Sourdough bread is made by the fermentation of dough using naturally occurring lactobacilli and yeast. Sourdough bread has a mildly sour taste not present in most breads made with baker's yeast, and better inherent keeping qualities than other breads due to the lactic acid produced by the lactobacilli.

Wine fault

A wine fault or defect is an unpleasant characteristic of a wine often resulting from poor winemaking practices or storage conditions, and leading to wine spoilage. Many of the compounds that cause wine faults are already naturally present in wine but at insufficient concentrations to be of issue. In fact, depending on perception, these concentrations may impart positive characters to the wine. However, when the concentration of these compounds greatly exceeds the sensory threshold, they replace or obscure the flavors and aromas that the wine should be expressing (or that the winemaker wants the wine to express). Ultimately the quality of the wine is reduced, making it less appealing and sometimes undrinkable.There are many causes for the perception in wine faults, including poor hygiene at the winery, excessive or insufficient exposure of the wine to oxygen, excessive or insufficient exposure of the wine to sulphur, overextended maceration of the wine either pre- or post-fermentation, faulty fining, filtering and stabilization of the wine, the use of dirty oak barrels, over-extended barrel aging and the use of poor quality corks. Outside of the winery, other factors within the control of the retailer or end user of the wine can contribute to the perception of flaws in the wine. These include poor storage of the wine that exposes it to excessive heat and temperature fluctuations as well as the use of dirty stemware during wine tasting that can introduce materials or aromas to what was previously a clean and fault-free wine.

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