Lactic acid test

Take two test-tubes A and B in A place about 5 ml. of neutralised tartaric acid solution and in B place 5 ml. of distilled water. To each solution add 3-4 drops of ferric chloride solution. Place a piece of white paper under the tubes, look down their length and note that A is definitely yellow compared with the control tube B. This yellow colour is given by a-hydroxy-carboxylic-acids, lactic acid, tartaric acid, citric acid. 

The fermentation-derived food-grade product is sold in 50, 80, and 88% concentrations the other grades are available in 50 and 88% concentrations. The food-grade product meets the Vood Chemicals Codex III and the pharmaceutical grade meets the FCC and the United States Pharmacopoeia XK specifications (7). Other lactic acid derivatives such as salts and esters are also available in weU-estabhshed product specifications. Standard analytical methods such as titration and Hquid chromatography can be used to determine lactic acid, and other gravimetric and specific tests are used to detect impurities for the product specifications. A standard titration method neutralizes the acid with sodium hydroxide and then back-titrates the acid. An older standard quantitative method for determination of lactic acid was based on oxidation by potassium permanganate to acetaldehyde, which is absorbed in sodium bisulfite and titrated iodometricaHy. 

Salpeter-luft,/. nitrogen (old name), -messer, m. nitrometer, -milchsiure, /. lactic acid nitrate, -papier, n. niter paper, nitrous paper, -plantage, /. saltpeter plantation, -probe, /. saltpeter test, nitrate test saltpeter sample. 

In more recent times chemically defined basal media have been elaborated, on which the growth of various lactic acid bacteria is luxuriant and acid production is near-optimal. The proportions of the nutrients in the basal media have been determined which induce maximum sensitivity of the organisms for the test substance and minimize the stimulatory or inhibitory action of other nutrilites introduced with the test sample. Assay conditions have been provided which permit the attainment of satisfactory precision and accuracy in the determination of amino acids. Experimental techniques have been provided which facilitate the microbiological determination of amino acids. On the whole, microbiological procedures now available for the determination of all the amino acids except hydroxy-proline are convenient, reasonably accurate, and applicable to the assay of purified proteins, food, blood, urine, plant products, and other types of biological materials. On the other hand, it is improbable that any microbiological procedure approaches perfection and it is to be expected that old methods will be improved and new ones proposed by the many investigators interested in this problem. 

Sf.i f-Test 10.9A Calculate the pH and percentage deprotonation of 0.50 m aqueous lactic acid. See Table 10.1 for Ka. Be sure to check any approximation to see whether it is valid. 

Suppose we have two test tubes, one containing (— )-lactic acid and the other the (-I-) enantiomer. One test tube contains 34 and the other 35. How do we know which is which Chemists in the early part of this century pondered this problem and decided... 

The earlier work of Miller (35), Outright (37), and Brady (5) on nonmedicated implants provided an excellent basis for further studies on specific controlled release formulations such as the determination of the biodegradation rates of lactide/glycolide drug-loaded microspheres (38). Those studies were done with l c-iabeled polymers produced from DL-lactic acid and glycolide. The final formulations tested in rats were microspheres loaded with H-labeled steroid and polymer as the matrix. The microspheres were administered intramuscularly and animals were serially sacrificed over a period of about a year. 

Hydrocortisone microspheres (108,109) and films (110) based on poly(lactic acid) have been investigated. A cage implant technique was used to study the performance of monolithic poly (DL-lactide) films loaded with hydrocortisone acetate (110). Films 1.5 x 0.6 cm were inserted into titanium wire-mesh cages 3.5 x 1.0 cm. The cages were implanted in the backs of rats and the inflammatory exudate was sampled periodically. The white cell concentration in the samples was lower than that of controls at all times during the 21-day test. 

The laboratory impinging jet test for evaluating the acid erosion of dental cements is described in Chapter 10. Using this method with lactic acid-lactate solutions, Wilson et al. (1986b) found, for one cement, that the erosion rate was virtually zero at pH = 5 0, 0-38 % at pH = 4-0 and 5 7 % at pH = 2-7. For a range of cements Wilson et al. (1986a) found erosion rates varying from 3 0 to 5-7 % in lactic add solutions of pH = 2-1. The... 

Billington, R. W., Williams, J. A. Pearson, G. J. (1992). In vitro erosion of 20 commercial glass ionomer cements measured using the lactic acid jet test. 

Sometimes, scientists just get it wrong. That certainly seems to be the case with lactic acid and exercise. For more than a century, lactic acid was seen as the "bad boy" of exercise. People believed that intense, unaccustomed exercise made lactic acid build up in muscles and made them burn and eventually tire and give out. Some athletes even went as far as to have the lactic acid level in their blood tested. Everyone considered lactic acid a toxic waste product. As it turns out, that is not true. 

Different organic acids, primarily lactic acid, have been successfully used for decontamination of whole livestock carcasses, and the application of different organic acids used for decontamination has also been tested in the fruit and vegetable industry. Organic acids other than lactic acid that are known to have bactericidal effects are acetic, benzoic, citric, malic, propanoic, sorbic, succinic and tartaric acids (Betts and Everis 2005). The antimicrobial action is due to a reduction in the pH in the bacterial environment, disruption of membrane transport, anion accumulation or a reduction in the internal pH in the cell (Busta et al., 2001). Many fruits contain naturally occurring organic acids. Nevertheless, some strains, for example E. coli 0157, are adapted to an acidic environment. Its survival, in combination with its low infective dose, makes it a health hazard for humans. 

Ackland MR and Reeder JE. 1984. A rapid chemical spot test for the detection of lactic acid as an indicator of microbial spoilage in preserved foods. J Appl Bacteriol 56 415—419. 

Lactic acid fermentation was the topic of a paper by Vaccari et al.35 In this work, lactic acid, glucose, and biomass were determined over the course of the reaction. The measurements were made in real time, using a bypass pump and flow-through cell for the NIR measurements. Instead of using normal chemomet-ric statistics, the authors used correlation coefficients, mean of differences, standard deviation, student s t-test, and the student test parameter of significant difference to evaluate the results. Under these restrictions, the results appeared fairly good, with the biomass having the best set of statistics. 

TMS systems, which were used in the isomerizing hydroformylation of frans-4-octene, should be apphcable to hydroaminomethylation as well because the hydroformylation is the first step of the reaction. For this reason similar TMS systems were apphed in a first series of investigations [40]. Propylene carbonate (PC) was chosen as the polar solvent si for the catalyst and alkanes (an isomeric mixture of dodecane or n-hexane) were used as non-polar component s2. 1.4-Dioxane, different pyrrohdones [N-methylpyr-rolidone (NMP), JV-ethylpyrrohdone (NEP), M-cyclohexylpyrrolidone (NCP) AT-benzylpyrrolidone (NBP) and N-octylpyrrohdone (NOP)] or esters of lactic acid (ethyllactate and butyllactate) served as mediator s3. As a test reaction the hydroaminomethylation of 1-octene with morphohne was investigated (Scheme 7). 

A solution containing chlorine dioxide concentrations of approximately 9.7-11.4 mg/L was nonirritating to the skin of mice in a 48-hour test (Shi and Xie 1999). Moderate to severe erythema was observed in rabbits following repeated daily applications of Alcide, an antimicrobial compound consisting of solutions of sodium chlorite and lactic acid that produce chlorine dioxide when mixed (Abdel-Rahman et al. 1987b). However, levels of exposure to sodium chlorite or chlorine dioxide could not be quantified. 

A practical technique for lactic acid fermentation of potato pulp has been developed (Oda et al., 2002). They screened 38 strains of the fungus Rhizopus oryzae either lactic acid or fumaric acid and ethanol were formed, and the ratio differed among the strains tested. Saito et al. (2003) studied the effect of pectinolytic enzymes on lactic acid fermentation of potato pulp by different Rhizopus oryzae NRRL 395 and NBRC 4707 strains. When a commercial preparation of pectinase was added to potato pulp inoculated with fungal spores and incubated for 7 days, both strains effectively produced larger amounts of lactic acid and ethanol. These data indicated that the fermentation of potato pulp depends on the degradation of pectic substances in NRRL 395 and NBRC 4707. Saito et al. (2006) evaluated the potato pulp obtained in different seasons and found pectin content to be dependent on the dates of extraction. 

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