Cholesterol in foods

ALTERNATE PROTOCOL 2 ENZYMATIC MEASUREMENT OF CHOLESTEROL Test combination kits for enzymatic determination of cholesterol in food are now commercially available. For the determination of total cholesterol, esterified cholesterol is hydrolyzed to free cholesterol and fatty acid under mild alkaline conditions. Cholesterol oxidase oxidizes free cholesterol to cholest-4-en-3-one to generate hydrogen peroxide, which further oxidizes methanol to formaldehyde. Formaldehyde then reacts with acetyl acetone in the presence of NH4+ ions to form yellow lutidine dye, which is subsequently determined spectrophotometric al 1 y. 

Several methodologies are known as effective tools for the determination of cholesterol in food and foodstuffs, e.g., colorimetry using the Libermann-Burchard reaction (Naito and David, 1984), Iatroscan thin-layer chromato-graphy/flame ionization detection (Indrasena et al., 1991), enzymatic determination (Shen et al., 1982), GC determination (Karkalas et al.,... 

Newkirk, D.R. and Sheppard, AJ. 1981. High pressure liquid chromatographic determination of cholesterol in foods. J. Assoc. Off. Anal. Chem. 64 54-57. 

For application in enzyme electrodes COD has been mainly immobilized by surface fixation (Table 7). As early as 1977, Clark had patented the polarographic analysis of free and esterified cholesterol by means of free as well as immobilized COD and CEH with anodic H2O2 indication. Cholesterol in food and serum samples has been determined by using COD bound to a collagen membrane via glutaraldehyde and coupled to a Pt electrode (Clark, 1978). A similar probe has been devised by Bertrand et al. (1979). In this sensor the enzyme membrane was not protected by a semipermeable membrane. Interferences were compensated for by difference measurements between an enzyme sensor and an enzyme-free membrane electrode. The lower detection limit was 0.05... 

Various physical, chemical, and biological methods have been proposed for reducing cholesterol in foods. These include blending with vegetable oils, extraction with... 

Another possible way of lowering cholesterol in food is the application of special diets for feeding animals. Many experiments with varying feeding conditions have been performed. Precht (2001) has shown that the cholesterol content in milk fat can be lowered by 8 to 13% with special feeding conditions using rapeseed. An extraordinary lowering of up to 50% can be achieved by dry fractionation of milk fat (stearin hard fraction). 

Pie, J.E., Spahis, K. and Seillan, C. (1990). Evaluation of oxidative degradation of cholesterol in food and food ingredients identification and quantification of cholesterol oxides, J. Agric. Food Chem., 38, 973. 

Determination of cholesterol in foods. Jian, Xuexin and Ai (1996) have determined the levels of cholesterol in foods by means of TLC. The separated lipids were sprayed with 5% phosphoric acid-alcohol solution to give coloration sterols. They found this method comparable to that of GC. 

Note There is very little cholesterol in low-fat dairy foods like skim milk and no cholesterol in food from plants, like fruits, vegetables, vegetable oils, grains, cereals, nuts, and seeds. 

Weiner MA (1986) Cholesterol in foods rich in omega-3 fatty add. N Engl J Med 315 833... 

The concern by consumers about cholesterol has stimulated the development of methods for its removal. Three principal approaches are in the pilot-plant stages use of enzymes, supercritical fluid extraction, and steam distillation. Using known techniques, it is not possible to remove all cholesterol from milk. Therefore, FDA guidelines identify cholesterol-free foods as containing less than 2 mg cholesterol per serving, and low cholesterol foods as containing from 2 to 20 mg (37). 

FoodApphca.tlons, Carbon dioxide, a nontoxic material, can be used to extract thermally labde food components at near-ambient temperatures. The food product is thus not contaminated with residual solvent, as is potentially the case when usiag coaveatioaal Hquid solveats such as methylene chloride or hexane. In the food iadustry, CO2 is not recorded as a foreign substance or additive. Supercritical solvents not only can remove oils, caffeiae, or cholesterol from food substrates, but can also be used to fractionate mixtures such as glycerides and vegetable oils iato aumerous compoaeats. 

Molecular Interactions. Various polysaccharides readily associate with other substances, including bile acids and cholesterol, proteins, small organic molecules, inorganic salts, and ions. Anionic polysaccharides form salts and chelate complexes with cations some neutral polysaccharides form complexes with inorganic salts and some interactions are stmcture specific. Starch amylose and the linear branches of amylopectin form inclusion complexes with several classes of polar molecules, including fatty acids, glycerides, alcohols, esters, ketones, and iodine/iodide. The absorbed molecule occupies the cavity of the amylose helix, which has the capacity to expand somewhat to accommodate larger molecules. The starch—Hpid complex is important in food systems. Whether similar inclusion complexes can form with any of the dietary fiber components is not known. 

Vitamins and Other Nutrients in Food Matrices see also Section 6.3. Food matrices are available with values assigned for vitamins, carotenoids, fatty acids, cholesterol, natural toxins, veterinary drugs, and hormone residues. The NIST food matrix SRMs for vitamins include coconut oil (SRM 1563), infant formula (SRM 1846), and baby food composite (SRM 2383) (particularly for carotenoids). Fatty acids and cholesterol are the primary analytes of interest in meat homogenate (SRM 1546) and diet... 

Synthesis of endogenic cholesterol is also controlled by exogenous cholesterol supplied in food the more dietary cholesterol is digested, the less endogenic cho-lesterol is produced in the liveV. Exogenous cholesterol inhibits the activity of hydroxymethylglutaryl-CoA reductase and the cyclization of squalene to lanosterol. 

Experimental. A second study was conducted with nine postmenopausal women age 51-65 yr. The subjects were fed standardized meals for 19 weeks. The mean composition for the 7-day menus of natural foods as % of total calories was 15% protein, 50% carbohydrate, 35% fat with a P/S ratio of 0.7, 10 g/day crude fiber, and less than 300 mg/day cholesterol. In addition, the diets supplied 1289 mg calcium, 1832 mg phosphorus, 2561 mg sodium and 5099 mg potassium daily. The diets met the RDA for all other nutrients. Calorie levels were adjusted to maintain body weight. The experimental meals were fed during the last six weeks of this 19-week period. No more than one liquid meal was consumed by each subject in one week. Fasting and postprandial samples of blood and urine were collected as in the previous study. Diuresis was induced by scheduled consumption of water. 

Most of the mention of cholesterol in the popular press positions this molecule as a threat to human health. Many foods are proudly labeled cholesterol-free. People are properly warned to pay attention to their plasma cholesterol level, particnlarly that carried in the low-density lipoproteins, LDLs, commonly known, with pretty good reason, as bad cholesterol. LDLs are lipoprotein particles containing a large protein known as B-100 associated with cholesterol, cholesteryl esters, phospholipids, and some triglycerides. 

Analysis of vitamin content of food materials appears to be a developing field. B vitamins in rice were analyzed using a mobile phase which contained pentanesulfonic acid and heptanesulfonic acid (558). Although the peaks were not sharp, the separation of the vitamins was satisfactory. Vitamin D in fortified milk has b n analyzed after removal Of cholesterol and carotenes in a preliminary cleanup (559, 540). Vitamin A has been analyzed in margarine, infant formula, and fortified milk (541, 542). Reports of the analysis of other vitamins in food are few to te but this mode of analysis can be expected to rapidly expand in the future in light of the variety of vitamin determinations in formulations which have been done (see Section VIII,F,l). 

Because of their similarity to the composition of human bile, which consists mainly of bile salts, phospholipids, and cholesterol, of interest for pharmaceutical studies are mainly binary bile salt micelles (BS/PL) (32,33). The function of the bile is to emulsify lipids in food and to dissolve the fission products of lipids as well as fat-soluble vitamins. The spontaneous formation of micelles is a necessary prerequisite to a contact of the lipophilic fission products with the intestinal wall. For affinity measurements, micellar sys-... 

Vitamin D is present in very low concentration in food, thereby its analysis is challenging, owing to the need to remove substances present in much higher amounts, such as cholesterol, vitamins A and E. When the total amount of vitamin D is determined in animal products, 25-hydroxyvitamin D3 has to be included due to its high amount. 

CAOlO Ratnayake, W. M., G. Pelletier, R. Hollywood, S. Malcolm, and B. Stavric. Investigations of the effect of coffee lipids on serum cholesterol in hamsers. Food Chem Toxicol 1995 33(3) 195-201. 

Investigation of the effect of coffee lipids on serum cholesterol in hamsters. Food Chem Toxicol 1995 33(3) ... 

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