INDEX ascorbic acid

FIG. 10 Vitamin C loss (percentage of apricot content before drying) and browning index (BI) of apricot cubes air dried (NT) or air dried following 60-min osmotic dehydration at 25 °C at atmospheric pressure in 60% (w/w) sucrose (SU) or maltose (MA) or 13% (w/w) sucrose (ISO) solution added with 1% ascorbic acid and 0.5% NaCl (Camacho et al., 1998). All samples were dried at 60 °C up to aw = 0.80. 

A simple method for assessing lipid oxidation is measuring the headspace concentration of hexanal by capillary GLC. Also, the total volatiles appearing in the chromatogram up to hexanal can be taken as oxidation index. The method was applied to determine the amounts of lipid peroxides present in rat liver cells. Enhancement of the hexanal concentration can be achieved on adding ascorbic acid (22), that reduces Fe(ni) present in the matrix to Fe(II), which catalyzes decomposition of hydroperoxides to aldehydes. Significant correlations are found between hexanal concentrations and various oxidation indices, such as TBARS (Section IV.D.2)" . ... 

The long-standing interest in the properties of L-ascorbic acid is manifested by the fact that 1146 references related to vitamin C are listed for year 2000 in the PUB MED index in the Internet. The most popular use of L-ascorbic acid is for prevention and treatment of the common cold, but this role remains controversial. In a recent review, the authors conclude that the long-term daily supplementation with large doses of vitamin C does not appear to prevent colds, but there is a modest therapeutic effect on the duration of cold symptoms.369... 

Blood plasma of children with cystic fibrosis was found to have decreased TAC (by 16%) in spite of increased concentrations of ascorbic acid, uric acid, and thiol groups (L4). In another study TAC of children with cystic fibrosis was normal, but these children received vitamin supplementation in doses prescribed in international guidelines (a-tocopherol <10 years, 100 mg daily, and >10 years, 200 mg daily retinol 2.5 mg daily ascorbic acid 100-200 mg daily) (M2). Other authors found TAC values for nonhospitalized patients (1.40 0.20 mM) not different from laboratory control values (1.35 0.11 mM), but greater than values for hospitalized patients (1.09 0.17 mM). TAC in CF children correlated positively with anthropometric values (height, weight, body mass index) and pulmonary function (forced expiratory volume in 1 sec), but not with age (L3). 

Fumed silica A-200 (Pilot plant at the Institute of Surface Chemistry, Kalush, Ukraine specific surface area Ascorbic acid (vitamin C) and all-rac-a-Tocopheryl acetate (vitamin E acetate) were used as adsorbates. Folin-Ciocalteu s phenol reagent (Merck) was used to measure the total polyphenolic index. Silica samples with different degree of surface silylation were obtained using gas-phase chemical modification of highly disperse silica (A-200) surface by trimethylchlorosilane.6... 

Antioxidant activity of silica nanocomposites with immobilized vitamin C was tested using the polyphenolic activity index.8 After adsorption of ascorbic acid on the silica surface and centrifugation, the excess solution was removed to obtain the suspension of a fixed volume (2 ml). Distilled water, sodium carbonate solution, and Folin-Ciocalteu s phenol reagent were subsequently added to suspensions and to the reference Vitamin C solution. The suspensions were then stored for 30 min, and the optical density of supernatant was measured at X = 750 nm. The reference solution of ascorbic acid was used to compare antioxidant activity of vitamin-containing nanocomposites with the activity of dissolved vitamin C. 

However, while some reports (Schwartz and Parks, 1974) indicate a correlation between the oxidation of ascorbic acid and the development of an oxidized lipid flavor, Smith and Dunkley (1962c) concluded that the oxidation of ascorbic acid alone cannot be used as an index of lipid oxidation. They reported that although ascorbic acid oxidation curves for homogenized and pasteurized milk were similar, the homogenized samples had a significantly lower tendency to develop oxidized flavor. 

As shown in Table I, iron intakes of both groups was approximately the same with mean values being only about one-half the NRC RDA allowances for this age/sex group. However, ascorbic acid intake levels were high which might have helped in the utilization of the iron provided. Hemoglobin and hematocrit levels which are sometimes used as indexes of adequate iron... 

The results of enzymatic determinations of ceruloplasmin are often expressed in arbitrary units, and the values judged in the light of a series of results obtained in normal subjects by the same method. Expression of the enzyme activity in milligrams of ceruloplasmin per unit volume of serum is also possible. The relation between oxidase activity and the amount of ceruloplasmin in serum can be determined by measuring in parallel samples of sera both the oxidase activity and the change of optical density at 610 mix before and after the addition of ascorbic acid or cyanide. On the basis of the known absorbancy index, the ceruloplasmin concentration can be calculated (see Section 2.2.1) and the relation between it and the enzyme activity determined. Alternatively, purified human ceruloplasmin can be used for standardization of the enzymatic method. The ceruloplasmin content of the purified preparation can be determined colorimetrically or, in the case of a highly purified preparation, by nitrogen analysis. Predetermined increments of ceruloplasmin can then be added to aliquots of a selected serum. It is convenient to select a serum with relatively low ceruloplasmin level to start with. Serum of a patient with Wilson s disease, some of whom have no measurable amount of enzyme activity, would be ideal for the purpose however, Walshe (W5) has recently found an inhibitor in these sera. 

Indoles, ascorbic acid 0.1 mol I. 1 phosphate buffer, pH 7.4 4.61-6.75 Differential refractive index detection Dm little affected by the analyte concentration [78]... 

A6. Anisova, A. A., Changes in the ascorbic acid content of the white blood as an index of the vitamin C content of the body. Bull. Exptl. Biol. Med. (U.S.S.R.) (English translation) 47, 708-710 (1959). 

The rise of ascorbic acid in the plasma in temporary stress is considered by some to constitute the most reliable index of stress, although it is somewhat less sensitive than eosinophilia. Ascorbic acid con-... 

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