Lactic acid quality

PLA offers an unprecedented market potential to lactic acid producers all over the world, but not all potential players can succeed, because PLA production poses stringent demands to lactic acid quality and price. The chemistry and physics of today s fermentative production and industrial-scale purification of lactic acid and lactide are the subject of this chapter. 

The dehydration of lactic acid to make the prepolymer should start with an —OH to —COOH ratio of 1 1. All other components with —OH and —COOH functionality disrupt the stoichiometric balance and may be incorporated as comonomers during prepolymerization, which limits the final lactide production yield from lactic acid. Little public information is available on the technical and economic relationship between lactic acid quality and lactide synthesis. Only a few patents mention the effect of metal impurities on racemization [68,69]. Stereochemical purity is one of the key parameters determining lactic acid purity. 

Having determined the effect of temperature and NaCl on koji autolysis, the next step in finding an optimal protocol for the rapid production of soy sauce with high flavor quality was to examine die effect of independent and combined effect of lactic acid fermentation and alcohol on koji autolysis. 

Antimicrobial peptides, relation to food quality-CortrirtMe / heat stability among lactic acid bacteria bacteriocins, 315-318 inhibitory activity, 308-309 interaction with food components, 314-315... 

Even prior to Pasteur, alcohol content determination was important as a basis for local, import, and export taxes. Other important applications of accurate wine analysis have been to detect and to accurately determine food additives now there are legal reasons for analyzing wines for sulfur dioxide, organic chloride or bromide, sodium, cyanide, diglucoside pigments, various insecticides, fungicides, etc. Winery control calls for analytical determination of iron, copper, protein, total acidity, pH, tartaric, malic and lactic acids, etc. Finally, quality control... 

The highly flavorable compound diacetyl is an important by-product of lactic acid bacterial fermentation. The mechanism of its formation has recently been unraveled (35). Diacetyl (measured as diacetyl rather than as diacetyl plus acetoin) is present in higher concentrations in wines with malo-lactic fermentation (cf. Ref. 36). At approximately threshold levels, this compound might contribute favorably to the flavor of wine (7) since increased complexity has been shown to enhance the quality of wine (37). 

The most important fermentative reaction used in dairy processing is the homofermentative conversion of lactose to lactic acid. The efficient manufacture of high-quality cultured products, including most cheese varieties, yogurt, and cultured buttermilk, requires a rapid and consistent rate of lactic acid production. Lactic acid helps to preserve, contributes to the flavor, and modifies the texture of these products. Nearly all starter cultures used to produce acidified dairy products contain one or more strains of lactic streptococci, because these organisms can produce the desired acidity without causing detrimental changes in flavor or texture. Strains of lactic streptococci can be classified as... 

In the analysis of fruit juices, it is important to determine the levels of the individual acids to assess authenticity and quality. A range of these acids can be determined using an enzyme-linked assays and these procedures have been collaboratively tested and published in the IFU compendium of methods (citric no. 22, isocitric no. 54, D-malic no. 64, L-malic no. 21 and D-and L-lactic acids no. 53). r-Biopharm now distributes the Boehringer Mannheim kits to assess the levels of these acids. Similar kits are available from other suppliers. 

Quality. Water. Fat. Albuminoids. Lactose and Lactic Acid. Ash. 

Simultaneous L-lactic acid fermentation (by Rhizopus oryzae immobilized in calcium alginate beads) and separation was carried out using a three-phase fluidized-bed bioreactor as a fermenter (F), an external electrodialyzer as a separator, and a pump to recycle the fermentation broth between the bioreactor and the separator. In this way, the experimental specific lactate productivity and yield practically coincided with those obtained in the CaC03-buffered fermentation process (Xuemei et al., 1999), thus confirming the capability of the combined system to alleviate product inhibition without any addition of alkali or alkali salts. It was also shown that the adoption of ED-F for the production of inoculum reduced variability in inoculum quality, thus shortening the length of the lag phase of L-lactate production practically to zero as compared to that observed using an inoculum... 

Lonvaud-Funel, A. (1999). Lactic acid bacteria in the quality improvement and depreciation of wine. Anton. Leeuw. Int.. G. 76, 317-331. 

Usually, after alcoholic fermentation, the wine undergoes malolactic fermentation, induced primarily by Oenococcus oeni. Not only can this lactic acid bacterium convert L-malic acid into L-lactic acid but also it is involved in many other transformations fundamental to Amarone quality. 

Steeping at temperatures >55°C can result in a favorable environment for the propagation of Clostridium spp., bacteria which produce acetic acid. Some strains of Clostridium are highly exothermic and can result in a self-regulated steep temperature of 59°C, even with all heat exchangers turned off. Total acidity does not seem to be much different than in a Lactobacillus spp. fermentation, except that the primary acid produced is acetic rather than lactic acid. There does not seem to be any discernible effect on starch yield or quality. 

The concentration of lactic acid in the steep has been shown to affect both the yield of starch178 and the quality of the resulting starch.179 Starch yields increased with increasing lactic acid concentration up to —0.5%, and decreased when more than —2% lactic acid was used. Shandera and lackson179 tested starch quality when steeped at 57°C with either 0.2% or 1.5% lactic acid and 0.05% or 0.3% sulfur dioxide. The level of sulfur dioxide had a small effect on starch quality, but the level of lactic acid had a pronounced reduction effect on peak viscosity, shear thinning viscosity, set-back viscosity, pasting viscosity and starch water solubility. 

In the Interior Valley, red wines are generally in the 3.4-3.7-pH range, which is more favorable for the malo-lactic fermentation that takes place within a few months after production. It is primarily a decarboxylation of malic acid to lactic acid. This results in a decrease in the acidity of the wine and an increase in pH. Generally, malo-lactic fermentation of Interior Valley wines decreases their quality. 

Lactic acid is a sour principle of yogurt and lactobacillus beverages. It exhibits a soft and thick sour taste quality with slight astringency. It is a syrupy liquid produced by fermentation with a lactobacillus and is formed in the body by the metabolism of sugars. Due to its pH-controlling effect, it is used in soft drinks, pickles, Japanese sakes, sherbets, and so on. It is industrially produced by the fermentation of glucose and chemical synthesis. Approximately 12 000 tons are consumed annually as a food additive in Japan. 

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