Lowering Cholesterol Naturally
The ability to ferment lactose varies among strains, but in the absence of lactose, dairy strains are quite capable of using lactate as a carbon and energy source. Metabolic end-products include propionic acid, acetic acid, and carbon dioxide. Small amounts of Vitamin B12 may also be produced. During growth in a peptide-rich medium, such as cheese, propionibacteria release the amino acid proline via peptide hydrol-ysis.They also are lipolytic, releasing free fatty acids from triglycerides. Despite their role as eye-formers in Swiss-type cheese, they are not particularly prolific CO2-producers.
Moreover, in cheese making, not only does the gross composition affect cheese properties, but so does the specific composition of each of the milk constituents.The lipid portion of goat milk, for example, contains a higher percentage of volatile, short-chain fatty acids, such that rancid flavor notes are most evident when the triglycerides are hydrolyzed by li-pases. The fat content also has a profound influence of other properties of cheese. Fat not only contributes to the body and texture of cheese, but it also serves as substrate for important flavor-generating reactions performed by microorganisms. Also, many of the flavor constituents derived from non-lipid substrates that form during cheese ripening are soluble in the lipid phase. For example, hydrophobic pep-tides derived from casein hydrolysis (many of which are bitter) are found in the fat portion of the cheese.
When the blood lipid levels are high, cholesterol tends to precipitate on the inner walls ofthe blood vessels and induce atherosclerosis and blood clots. Tea drinking can lower the level of blood lipids in particular, the EGCG (epigallocatechin gallate) can lower the low-density lipoproteins (LDL) and increase the high-density lipoproteins (HDL). In rat feeding studies, 0.5-1.0 EGCG in the rat feed can significantly lower the contents of total cholesterol, free cholesterol, low-density lipoproteins, and triglycerides, and increase the high-density lipoprotein content there are also increases in the cholesterol and lipid contents excreted into the feces.
Hydrolytic rancidity or lipolysis is caused by the release of free fatty acids from the glycerol backbone of triglycerides. The reaction is catalyzed by the lipase enzyme, which can be a native milk lipoprotein lipase or can originate from bacterial sources. Triglycerides are generally protected from lipase activity as long as the milk-fat globule remains intact. However, damage to the globule will lead to rapid lipolysis because lipase, which is situated on the surface of the globule, can access the triglycerides. Therefore, precautions must be taken to prevent damage to the milkfat globule until pasteurization, which denatures most types of lipase. This means that raw milk cream must be pasteurized before or immediately after homogenization to assure denaturation of lipase. Likewise, it is strongly recommended never to recycle pasteurized milk cream back into raw milk cream storage, which is essentially an issue of rework handling. Cream from poor-quality raw milk can also develop...
The limited lipolysis that occurs during the ripening of Cheddar cheese manufactured from pasteurized milk is probably effected by the lipolytic enzymes of the starter lactococci and nonstarter lactobacilli, although LAB are generally only weakly lipolytic. Screening studies using natural substrates, triglycerides, and synthetic chromogenic substrates (58) have confirmed the presence of lipase (121-123) and esterase activities in mesophilic (67,123-125) and thermophilic (126,127) dairy lactobacilli. In general the enzymes were located intracellularly, and activities were strain specific but tended to be higher in thermophilic than mesophilic strains. In the majority of strains examined, activities increased as the carbon chain length of the fatty acid decreased. The only lipase purified is a 65 kDa molecular mass intracellular enzyme produced by Lb. plantarum (128). The enzyme hydrolyzed the triglycerides trilaurin and tripalmitin but was most active against tributyrin. The purified...
More end-products that are characteristic of blue cheese flavors are generated, however, from lipid metabolism. About 20 of triglycerides in milk are initially hydrolyzed by P roqueforti-produced lipases, releasing free fatty acids, including short chain, volatile fatty acids, such as butyric and caproic acids. Metab olism of free fatty acids via p-oxidation pathways then yields a variety of methylketones, compounds that are responsible for the characteristic flavor and aroma of blue cheese. Similarly, growth of the Brie cheese mold, P. camemberti, results in a similar sequence of metabolic events. Proteinases and lipases diffuse through the cheese (since the mold grows only at the surface), generating amino and free fatty acids. Subsequent metabolism of the amino acids results in formation of ammonia, methanethiol, and other sulfur compounds, presumably derived from sulfur-containing amino acids. Lipolysis of triglycerides and fatty acid metabolism by P. camemberti are just as...
Kimchi has a low caloric content, but it is rich in minerals, vitamins, and dietary fiber. The protein and lipid contents can be increased with various subingredients like fish, clams, oysters, and meat, which give kimchi its characteristic savor. Triglycerides, polar lipids, free fatty acids, monoglycerides, hydrocarbones, sterol, and about 18 various free fatty acids were found, among the major fatty acids (44 to 60 ) are linoleic and linolenic acid. The
Microalgal production of useful chemicals and energy resources have been extensively investigated. Processes that utilize the majority of the resulting microal-gal biomass as energy sources would be desired. Such processes may allow the recycling of evolved CO2 from human energy consumption rather than a one-way emission, as is the case with fossil fuels. The following six products can be produced from microalgal biomass for use as fuels hydrogen (through biophotolysis), methane (through anaerobic digestion), ethanol (through yeast or other alcohol fermentation), triglycerides (through extraction of lipids), methyl ester fuels (through transesterification of lipids), and liquid hydrocarbon (from Botryococcus braunii).
For example, methyl ketones, which contribute to the characteristic flavor of blue cheese, are synthesized by P. roqueforti from free fatty acids.Thus, methyl ketone formation depends on release of these acids from triglycerides via lipolytic enzymes produced by microorganisms or naturally present in the milk. Similarly, hydrogen sulfide, which is an important flavor note in aged Cheddar cheese (or may also be a defect see below), is derived from sulfur-containing amino acids that form via protein and peptide hydrolysis. As noted above, cheese contains mostly water, protein, and fat as it leaves the vat and moves into the ripening coolers. Although some protein hydrolysis certainly occurs during the lactic fermentation by starter culture bacteria and by the action of milk proteases and the coagulant, as1, as2, and p-caseins are still intact. Similarly, the triglycerides in milk are also mostly unaffected by the early cheese-making steps. However, within just a few days, enzymes begin...
Tors make Feta crumbly.The main flavors in Feta are due to lactic acid and salt, but, depending on the presence of lipases (exogenous or from milk), there can also be considerable hydrolysis of triglycerides and formation of free fatty acids. It is the release of short, volatile fatty acids, including acetic, propionic, butyric, and valeric acids, that account for the rancid-like flavor notes characteristic of these cheeses.
It is now well established that lipolysis in dry sausages is, to a great extent, of endogenous origin (84,99). There are two types of endogenous lipases triglyceride lipases present in the muscle and in the adipose tissue, which act on triglycerides, and phospho-lipases, which hydrolyze phospholipids and whose optimal pH of 5.5 is close to that of sausages (100-102). The importance of endogenous lipolysis has been demonstrated by manufacturing aseptically or in paucimicrobial sausages inoculated by micrococci or staphylococci and comparing the increase in the level of fatty acids (101,102) and also by manufacturing sausages using antibiotics (99). According to Hierro et al (102), lipolysis by endogenous enzymes accounts for more than 60 of total free fatty acid release. Similarly, Johansson (103) considers that about 30 of lipolysis come from the lipolytic strain of
Lower Your Cholesterol In Just 33 Days
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