A. Frígola

Determination of ascorbic and dehydroascorbic acids in blood plasma and serum by liquid chromatography

A liquid-chromatography (LC) method with ultraviolet detection for measuring ascorbic (AA) and dehydroascorbic acid (DHA) in human blood and serum was studied. The method used an ODS reversed-phase column and cetyltrimethyl ammonium bromide as an ion-pairing agent. AA was measured before and after the reduction of DHA with dithiothreitol. The absence of interferences resulting from hemolysis products was verified and also the stability of the ascorbic acid in metaphosphoric acid extracts. The analytical parameters, linearity (1-80 micrograms/ml), accuracy (recovery, 96.7-100.7%) and precision (C.V. = 3.1%), show that the method is reliable and adequate for measuring the total vitamin C content in serum and plasma.

Determination of liposoluble vitamins in cooked meals, milk and milk products by liquid chromatography

A method for the simultaneous determination of liposoluble vitamins in cooked meals was established. Saponification was performed with 50% (w/v) KOH at 80 degrees C, and ascorbic acid was added as antioxidant. The subsequent extraction was carried out with diethyl ether. This was followed by a liquid chromatographic separation on a reversed-phase C18 column with methanol-water (94:6, v/v as the mobile phase. Retinyl acetate was used as the internal standard. The analytical parameters linearity, detection limit (0.19 and 8.33 microg/100 g for retinol and alpha-tocopherol, respectively), precision of the method (RSD=5.24 and 6.99% for retinol and alpha-tocopherol, respectively) and recovery assays (95.6 and 96.5% for retinol and alpha-tocopherol, respectively) show that the method studied is useful for measuring these compounds in foods and cooked meals.

Determination of vitamin B6 (pyridoxamine, pyridoxal and pyridoxine) in pork meat and pork meat products by liquid chromatography

A liquid chromatographic method for determining vitamin B6 compounds in pork meat and pork meat products is examined. It uses the same extraction procedure as that applied for thiamin and riboflavin determination, followed by a liquid chromatographic separation on a reversed-phase C18 column with 0.01 M H2SO4 as mobile phase at 30 degrees C. 4-Deoxypyridoxine is used as internal standard. The analytical parameters linearity, precision of the method (R.S.D. = 7.3 and 6.9% for pyridoxamine and pyridoxal, respectively) and accuracy obtained by recovery assays (99 and 85.1% for pyridoxamine and pyridoxal, respectively) show that the studied method is useful to measure these compounds in pork meat.

Comparison of voltammetric and high performance liquid chromatographic methods for ascorbic acid determination in infant formulas

Abstract Two methods — voltammetric and high performance liquid Chromatographic (HPLC) — useful for determining ascorbic acid in foods, were compared to ascertain which of them could be used for routine determination of ascorbic acid in infant formulas. Both methods were used to assay 10 identical samples of an adapted cows milk infant formula and 10 samples of soya protein formula. Precision was determined, the variance of each method was measured, and the methods were compared with each other. The variances of the two methods were not statistically different nor was there any significant difference between the results from the two methods. Therefore, it was concluded that both methods can be used for determination of ascorbic acid in infant formulas. The voltammetric method, because of its simplicity, cheapness and less time-consuming nature, could be used for routine determination.

Kinetics of Ascorbic Acid Degradation in Green Asparagus during Heat Processing

The effect of heating on ascorbic acid in green asparagus during a simulated retort operation was investigated. The asparagus was heated in trays of ethylene-vinyl alcohol copolymer for selected time intervals at four temperatures ranging from 110 to 125 degrees C. It was found that the rate of degradation followed first-order kinetics. Kinetic parameters were obtained by using two least squares methods. The activation energy and z value were 35 kcal/mol and 20 degrees C, respectively.

Contents of vitamins B1, B2, B6, and B12 in pork and meat products

Abstract The concentration of B vitamins (B 1 , B 2 , B 6 , and B 12 ) was determined in three pork muscles ( Longissimus dorsi , loin; Biceps femoris , ham; and Triceps brachii , shoulder) and in pork and other meat products (cooked, pickled, and cured), of importance because they are consumed in high quantities. The results were compared with values reported by other authors and their contribution to the daily intake of these vitamins estimated. This showed that pork provides, on average, 97, 25.8, 35/43.7 (men/women), and 37% of the RDA (Recommended Dietary Allowances) for vitamins B 1 , B 2 , B 6 , and B 12 , respectively.

Determination of ascorbic acid in asparagus by differential pulse polarography

A useful method for the determination of ascorbic acid in a vegetable product (asparagus) by differential pulse polarography has been set up and evaluated. Extraction and instrumental conditions were optimized. The analytical parameters are: linearity (0–18.18 μg/ml); detection limit (0.182 μg/ml); instrumental and method precision (2.77% and 4%, respectively); accuracy (96.9–113.4%). These data show that the method is sufficiently sensitive, reliable and accurate. It was also compared with the official fluorometric AOAC method.

Use of polarography as a quality-control method for determining diacetyl in citrus and vegetable juices, yoghurt and butter

The determination of diacetyl permits the detection of microbial growth in the processing of citrus fruit before the appearance of other organoleptic, chemical or microbiological changes. It also makes it possible to detect a break in the cold chain during distribution and sale. The study proposed a polarographic method for the determination of diacetyl that allowed routine analysis with the aim of detecting possible contamination in the citrus juice manufacturing chain (orange and orange-carrot). The analytical performance of the method in terms of a linearity from 0 to 960 μg ml-1, a recovery of 97 to 98%, a precision of 3.2 to 4.8%, and a sensitivity of 0.2 ng ml-1 for juices indicated the robustness of the method. The same method was also applied to butter and yoghurt with detection limits of and 0.4 ng g-1.

Steviol Glycosides Stability after Pulsed Electric Technologies and Ultrasounds Treatments in Fruit Juice Blend Sweetened with Stevia rebaudiana

Stevia rebaudiana bartoni due to its high content in steviol glycosides and the ability to serve as a natural antimicrobial to complement the effectiveness of pulsed electric technologies for food preservation, has been used more frequently to improve sensorial properties of liquid foods.

Dietary Assesment of Free-Living Elderly Spanish People with Disabilities

ABSTRACT Nutritional research in elderly disabled is difficult in noninstitutionalized people. The dietary intake of a noninstitutionalized disabled population of the eastern region of Spain was evaluated to detect possible nutritional deviations. A total of 329 participants aged 65 and over were recruited. Most participants were overweight. Carbohydrates did not reach 50% of total Kcal/day. Insufficient micronutrient intakes and high consumption of simple carbohydrates and saturated fats (SFA) were found. A decreasing trend of water intake (p < .05) as well as an increasing trend of alcohol consumption (p < .05) with increasing age was found. The area of residence had a relevant impact on nutritional, dietary, and anthropometric characteristics of our population.