Use and abuse of ascorbic acid—A review

The antiscorbutic¹ and ‘extra-antiscorbutic’ functions of ascorbic acid are reviewed. Although megatherapy remains unproven there is substantial evidence that ascorbic acid may affect metabolism in other ways, e.g. by enhancing heavy metal absorption from the alimentary canal. There is little generally accepted evidence that megadoses of ascorbic acid are of themselves toxic.     

Changes in nitrogen content and amino acid composition of navel oranges during ripening

Nitrogen content and composition of amino acids in juice and rind of navel oranges were studied. The compared varieties were ‘Navelina’ ‘Washington Navel’ and ‘Navelate’, early, mid-season and late types, respectively. Total N content in juice increased during the season with values from about 60 to near 100 mg 100 ml^?1 in Navelina and ‘Washington Navel’ and from 60 to about 80 mg 100 ml^?l in ‘Navelate’; amino N increased from 30 to 60 mg 100 ml^?lapproximately in the three varieties. The total N content in rind was quite similar in all cases, with values that decreased with time from 1 to around 0·6 g 100 g^?l dry weight (DW), 50–60% corresponding to the protein N. The main free amino acids in juice and rind at different maturity stages are tabulated. Proline represents at maturity around 50% of the total free amino acids in rind, with values near to 1·5 mmol 100 ml^?l in juice and over 5·0 mmol 100 g^?1 DW in rind. Total protein amino acids in rind decreased during maturation, reaching final values of about 20 mmol 100 g^?1 DW. Differences in composition among the three studied varieties are discussed.     

Chemical evaluation of the nutritive value of the raffia palm fruit (Raphia hookeri)

Investigations were carried out to determine the chemical composition of the fruit of the raffia palm (Raphia hookeri: Family, Palmaceae or Palmae). The peel and pulp (edible portion) were analysed. The effect of boiling on the chemical composition of the pulp was also investigated.The peel contained more moisture (62·4%) than the pulp (38·0%) in terms of wet weight. The protein and ether extract contents of the peel were found to be 3·2% and 1·8% of dry material, respectively. The ash content was 5·5%. Crude fibre gave a very high value of 70·3% for the peel, but the carbohydrate content was low (19·3%).There were decreases in the values of some nutrients after boiling the edible pulp of the fruit. Protein content decreased from 6·1% to 4·4% upon boiling. Ether extract and carbohydrate contents decreased from 11·8% to 11·3% and from 61·4% to 58·8%, respectively. Boiling increased the crude fibre and ash contents of the pulp from 17·7% and 3·0% to 21·2% and 4·3%, respectively. The calorific value decreased from 380·5 kcals to 354·7 kcals.Tannin content was highest of all the toxic substances evaluated. There was a decrease from 597 to $\text{360}\text{mg}\text{100}\text{g}$ on boiling. The peel contained $\text{234}\text{mg}\text{100}\text{g}$ tannins and $\text{24·3}\text{mg}\text{100}\text{g}$ hydrocyanic acid. Boiling the pulp resulted in reduction of the HCN from 12·4 to $\text{9·2}\text{mg}\text{100}\text{g}$, phytic acid from 1·0 to $\text{0·4}\text{mg}\text{100}\text{g}$, and oxalate from 26·4 to $\text{17·6}\text{mg}\text{100}\text{g}$. The peel had more oxalate ($\text{39·6}\text{mg}\text{100}\text{g}$) and cyanide ($\text{24·3}\text{mg}\text{100}\text{g}$) but less phytic acid ($\text{0·6}\text{mg}\text{100}\text{g}$) than the pulp.Ascorbic acid and carotene contents decreased upon cooking the pulp from $\text{63·0}\text{mg}\text{100}\text{g}$ and $\text{33·4 μ}\text{g}\text{100}\text{g}$ to $\text{28·3}\text{mg}\text{100}\text{g}$ and $\text{10·6 μ}\text{g}\text{100}\text{g}$, respectively. The peel had an ascorbic acid content of $\text{37·2}\text{mg}\text{100}\text{g}$ and carotene content of $\text{8·6 μ}\text{g}\text{100}\text{g}$.Calcium, potassium, sodium and phosphorus decreased with cooking, while magnesium, zinc and iron contents were increased. Potassium had the highest level followed by calcium. The pulp had (mg/100 g): K, 1075; Ca, 875; Mg, 315; Zn, 9·6; P, 76·8; and Na, 16. The peel had (mg/100 g): Ca, 250; Mg, 450; K, 700; Na, 8; Zn, 3·5; and P, 37·7. Copper, chromium and cobalt were not detected in the fruit.The results are discussed in terms of the value of the fruit as food for man or animals.     

Japanese barnyard millet (Echinochloa frumentacea): Protein content,quality and SDS–PAGE of protein fractions

Total protein from five varieties of Japanese barnyard millet (Echinochloa frumentacea,) was separated into albumin/globulin, prolamin and glutelin fractions. The protein fractions were examined by sodium dodecylsulphate polyacrylamide gel electrophoresis. Total protein of the varieties ranged from 110·5 to 139·3 mg g^?1 of which 11·3–17·2% was albumin/globulins, 6·8–9·3% prolamins, 7·5–11·6% prolamin–like, 5·9–9·1% glutelin-like and 39·3–54·4% true glutelins. Amino acid analyses of the total protein showed that the varieties had essentially the same ammo acid composition. With the exception of lysine the amino acid levels adequately matched the provisional FAO scoring pattern. The amino acid composition of the protein fractions was also very similar. Electrophoretic analysis showed that the albumin/globulin fraction contained three or four components; the prolamin and glutelin fractions each had five components. The glutelin fraction had higher molecular weight components than the other two fractions.     

Proximate composition,mineral contents,hydrogen cyanide and phytic acid of 5 cassava genotypes

Five cassava genotypes Rayong 5, Kaesetsart 50 (KU50), Rayong 2, Hanatee and KMUL 36-YOO2 (YOO2), were used in this study. Investigations showed that cassava contained 9.2–12.3% moisture, 1.2–1.8% crude protein, 0.1–0.8% crude lipid, 1.5–3.5% crude fibre, 1.3–2.8% ash, 80.1–86.3% carbohydrate, 1406–1465 kJ 100 g⁻¹ DM and 95–135 mg g⁻¹ of phytic acid. Mineral contents were 10.9–39.9, 15.2–32.3 and 9.3–54.1 mg g⁻¹ for Ca, Mg and P, respectively, and 221–328, 4.7–25.8, 1.41–4.25, 0.29–1.73 and 1.2–4.44 mg g⁻¹ for K, Na, Zn, Mn, Cu, and Fe, respectively. HCN content ranged from 8.33 to 28.8 mg HCN/kg dry weight basis. A linear relationship between Ca and P and carbohydrate and energy existed with correlation coefficients of 0.99 and 0.82, respectively. Phytate: total p ranged from 77% to 88% and a linear relationship existed between phytate and total p with a correlation coefficient of 0.975.     

Chemical Composition, Antioxidant Capacity, and Sensory Quality of Pomegranate (Punica granatum L.) Arils and Rind as Affected by Drying Method

The objective of this study was to evaluate the application of: (1) freeze drying, (2) convective drying (50, 60, or 70 °C), (3) vacuum–microwave drying (240, 360, or 480 W), and (4) a combined method of convective pre-drying and vacuum–microwave finish drying in the processing of pomegranate arils and rind. The quality parameters under study included sugars and organic acids, punicalagins and ellagic acid, total polyphenols, total antioxidant activity, and sensory quality. In general, drying led to a reduction in all studied parameters; however, the behavior of arils and rind was different. Vacuum–microwave drying at 240 or 360 W was the best drying treatment for arils, while rind required freeze drying or soft conditions of convective drying (50 °C). Further research is needed to obtain proper results with convective pre-drying and vacuum–microwave finish drying of arils and rind. With proper selection of the drying protocol, high-quality dried arils will be available for consumers; these arils will be characterized by high contents of fructose (25 g 100 g^?1), phytic acid (2.2 g 100 g^?1), punicalagins (0.57 mg g^?1), total polyphenols (1.6 mg eq gallic acid g^?1), high antioxidant capacity (0.6 mg eq Trolox g^?1), and high intensities of garnet color, sweetness, sourness, and fresh pomegranate aroma. Besides, dried rind with very high contents of active compounds (123 mg g^?1 of punicalagins and 108 mg eq gallic acid g^?1) and high antioxidant capacity (26 mg eq Trolox g^?1) will be also available as functional material.     

Effect of heat treatments on the phytic acid content of maize products

Processing of maize (Zea mays L fresh and dry) for the production of various traditional products results in the loss of phytic acid. Fresh mature corn contains less phytic acid (1·71 g kg^?1) than dry corn (7·15–7.60 g kg^?1). The loss of phytic acid varies from 18·1 to 46·7% for fresh maize and from 11·5 to 52·6% for dry maize respectively among the heat treatments given. From a nutritional viewpoint, consumption of maize as chapati and after roasting in a sand bath or on charcoal will improve the availability of minerals.     

Rapid Quantification of Soyasaponins I and βg in Italian Lentils by High-Performance Liquid Chromatography (HPLC)–Tandem Mass Spectrometry (MS/MS)

In this work, an innovative and fast analytical method for the quantification of soyasaponins I and βg in lentils has been developed. Samples were extracted using 70 % aqueous ethanol at room temperature and then injected into a high-performance liquid chromatography–tandem mass spectrometry system. The correlation coefficients of calibration curves of the analyzed compounds were ≥0.9997. The recoveries obtained by spiking the lentil samples with a standard mixture of soyasaponins I and βg at 50 and 100 mg l^?1 were in the range of 96–101 and 98–103 %, respectively. The validated method was applied to the analysis of 30 lentil samples from central Italy. Soyasaponins I and βg were present in these lentils in concentrations that ranged from 54 to 226 mg kg^?1 and from 436 to 1,272 mg kg^?1, respectively. Our data indicated that lentils cultivated in fields at intermediate altitudes (1,142–1,387 m) showed the highest levels of soyasaponins, a finding confirmed by principal component analysis.     

Antioxidant properties,anti-inflammatory effects,and bioactive constituents of the Indian medicinal rice Njavara yellow compared with staple varieties

Polar and non-polar extracts of Njavara yellow rice (NYr) and bran (NYb) were investigated for antioxidant activity, chemical indices, anti-inflammatory effects, and bioactive compounds, of which the results were compared between the 2 staple varieties Uma and Jaya. Methanol extracts of NYb showed significantly (p<0.05) higher antioxidant activity than other varieties with the IC₅₀ values of 97 μg/mL (DPPH^·) and 48 μg/mL (ABTS^·+). NYb showed a higher anti-inflammatory effect and higher chemical indices (6.36 mg, phenolic content; 1.44 mg, flavonoid content; 3.06 mg, proanthocyanidin content; and 15.5 mg, phytate content per gram of dry weight of bran) than NYr and staple varieties. The content of bioactive compounds, oryzanols (659 μg/mL) and tricin (24.58 mg/100 g bran), were higher in NYb than in other varieties. Evaluation of biological activities and quantification of bioactive compounds of Njavara yellow are first pursued herein to corroborate Njavara Ayurveda medicinal use.     

Iron content and availability studies in some Sri Lankan rice varieties

Thirty‐eight rice varieties, grown in Low Country Wet Zone, during Yala (2006) and Maha (2006/2007) seasons were screened for stable high iron rice varieties and were statistically analysed. Iron contents ranged 1.89–3.73 mg 100 g^?1 and varied significantly (P < 0.05) with variety and season. Selected fifteen high iron rice varieties, at degree of polishing 8–10% were analysed for iron, zinc and phytate. High iron contents in endosperm were observed in Suduru Samba (0.47 mg 100 g^?1), Basmati 370 (0.37 mg 100 g^?1), Kalu Heenati (0.42 mg 100 g^?1), Rathu Heenati (0.44 mg 100 g^?1) and Sudu Heenati (0.37 mg 100 g^?1). Phytate contents of polished rice varieties ranged from 200–300 mg 100 g^?1. Large reduction in iron content (84.5–93.6%) was observed in polished rice while the reduction in phytate content (18.9–40.8%) was low. Percentage dialyzability of iron in selected endosperm high iron rice varieties ranged from 1.73 to 8.71. Dialysability of iron in cooked polished rice did not show a relation to the phytate content in raw rice.     

Improvement of Determination of Trace Amounts of Arsenic and Selenium in Slim Coffee Products by HG-ICP-OES

A method for the determination of total inorganic arsenic and selenium in slim instant coffees using hydride generation inductively coupled plasma optical emission spectrometry (HG-ICP-OES) was proposed. Various sample preparation procedures, including the traditional total decomposition by the hot-plate or microwave heating in a HNO₃/H₂O₂ mixture and alternative procedures based on the solubilisation in aqua regia or tetramethyl ammonium hydroxide (TMAH) and the dilution only with water or a low concentrated HNO₃ solution were examined and compared. Corresponding As and Se hydrides were generated in the reaction of an acidified sample solution with the NaBH₄ reductant in the presence of antifoam A. A small sample preparation with aqua regia in an ultrasonic bath followed by the pre-reduction with KI–ascorbic acid in the HCl medium for total As and the boiling with HCl for total Se were found to be optimal. The external calibration using standards treated and measured as the same as samples were applied for the analysis. Limits of detection (LODs) of 0.96 and 0.55 ng ml^?1 were assessed for As and Se, respectively. The precision (as the relative standard deviation [RSD]) was within 1.6–7.1 %. The accuracy of the method was confirmed by the recovery test and the analysis of a standard reference material (non-fat milk powder, SRM 1459). The developed procedure was applied for the analysis of six commercial instant slim coffee products available in the Polish market and it was found that these products contain traces of As (0.114–0.247 μg g^?1) and Se (0.089–0.137 μg g^?1).     

Protein,amino acid,ash and mineral contents in Brassica spp. grown in Northwest Spain

The protein, amino acid, ash, and mineral composition of different Brassica spp. grown in several areas of Galicia (Northwest Spain) were studied. The highest protein values were observed in Galega kales (crude protein: 29.66 g per 100 g) and turnip greens and turnip tops (27.74–31.46 g per 100 g), whereas the leaves showed higher protein contents than the stems. Glutamic acid was the most abundant amino acid present (14.53% in turnip greens to 18.45% in white cabbage). Other amino acids such as arginine, aspartic acid, lysine, alanine and glycine were also observed in higher quantities. The stems contained the same amino acid as the leaves but at a lower level. Furthermore, differences in amino acid contents were observed among varieties. The proportion of essential amino acids was high (41% in leaves of turnip top to 47% in external leaves of oxheart cabbage). The studied varieties are also a good source of some minerals, which include as main element potassium (27.24–37.57 mg g^?1 in whole plants), followed by calcium (4.27–17.48 mg g^?1 in whole plants) and magnesium (1.62–2.92 mg g^?1 in whole plants). Significant differences among varieties and edible portions were found concerning ash and mineral contents.     

Effect of irradiation and germination on selected nutrients of corn

The effect of germination on potential nutrients (mineral matter, protein, lipids, fibre, carbohydrates and total energy) and an antinutrient (phytate) of corn, was studied. The influence of irradiation (5–20 krad) and germination on the vitamin contents (ascorbic acid, riboflavin) was also investigated. Comparison of the coefficients of variability revealed striking differences in the contents of these nutrients as a result of germination. Total mineral matter increased from 1·15% to 1·40%, protein from 9·6% to 14·0%, lipids from 4·36% to 4·60% and fibre from 0·71% to 0·82% whereas phytate decreased from 200 to $\text{105}\text{mg}\text{100}\text{g}$ and carbohydrates from 85·5% to 70·0%. Radiation and germination significantly affected the ascorbic acid and riboflavin contents of corn (p < 0.05). A maximum value of ascorbic acid ($\text{19·4}\text{mg}\text{100}\text{g}$) was observed in the 10 krad treated seeds as compared with $\text{14·3}\text{mg}\text{100}\text{g}$ in the control after 120 h of germination. Similarly, riboflavin increased from an initial value of 1·5 μg/g to 13·1 μg/g in the 20krad sample as compared with 6·0 μg/g in the unirradiated control.     

Development and Optimization of a SERS Method for On-site Determination of Nitrite in Foods and Water

A rapid, sensitive, and selective detection method of nitrite in foods and water was established by surface-enhanced Raman spectroscopy (SERS) based on the diazo reaction of nitrite with p-nitroaniline and 1-naphthylamine in acidic solution. The azo dye (4-(4-nitrophenyldiazenyl)naphthalene-1-aminium, NNA), which was derived from the diazo reaction, was determined by SERS using citrate-coated silver nanoparticles (AgNPs) as SERS substrates. The concentrations of nitrite in samples were finally calculated from the intensities of SERS signals generated by NNA in the testing solutions. By using the present method combined with a portable miniature Raman spectrometer, on-site determination of nitrite could be performed easily and efficiently. The effects of several experimental parameters on the intensity of SERS signals, such as the volume of AgNP solution and the mixing time of AgNPs and NNA, were investigated. The linear range of the method was 0.1–10.0 mg L^?1. The limits of detection (LODs) were 0.01, 0.03, and 0.05 mg L^?1 at 720, 1,459, and 1,609 cm^?1, respectively. The method was applied to the determination of nitrite in real food and water samples, with recoveries in the range of 86.9–103.4 % and relative standard deviations (RSDs) less than 9.64 %.     

Determination of Total Antioxidant Capacity of Rapeseed and Its By-Products by a Novel Cerium Oxide Nanoparticle-Based Spectrophotometric Method

The antioxidant capacity (AC) of rapeseed, white flakes, and meal was determined by the novel cerium oxide nanoparticle-based (CeONP) method and a previously described assay based on the formation of silver nanoparticles (AgNP). Antioxidants present in rapeseed and its by-product extracts reduced cerium(IV) ions to red-purple solutions of cerium oxide nanoparticles at pH 5.6. The influences of time, temperature, pH, and the concentration of the cerium(IV) sulfate solution on cerium oxide nanoparticle generation were estimated. The average AC of the studied extracts of real samples ranged between 1037 and 3012 μmol sinapic acid (SA) 100 g^?1 and 3859–12,534 μmol SA 100 g^?1 for CeONP and AgNP assays, respectively. There is significant, positive correlation between the AC of the examined extracts determined by both analytical methods (r?=?0.8189). Satisfactory values of relative standard deviation (RSD?=?1.2–3.9 %) and recovery (95.8–103.3 %) demonstrate a good precision and accuracy of the novel CeONP method for the AC analysis of rapeseed and its by-products.

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Graphical Abstract Reaction mechanism of cerium ions reduction by sinapic acid was proposed for a new cerium oxide nanoparticle-based (CeONP) method

     

Chemical composition,protein fractionation,essential amino acid potential and antimetabolic constituents of an unconventional legume,Gila bean (Entada phaseoloides Merrill) seed kernel

Physical characteristics of pods and seeds, proximate composition, different protein fractionation, SDS‐PAGE analysis of proteins, amino acid composition, starch content, fatty acid profiles and various antimetabolic substances of Gila bean (Entada phaseoloides Merrill) were studied. The pod length and the number of seeds per pod ranged from 55 to 90 cm and from 5 to 11 respectively. The kernel comprised 66.1% of the seed weight (18.41 ± 1.14 g). The seed kernels contained 256.7 g kg^?1 crude protein, 108.1 g kg^?1 lipid, 27.3 g kg^?1 ash and a high content of carbohydrate (585.7 g kg^?1). The levels of potassium, phosphorus, zinc and iron were similar to those in conventional pulses. Among the different protein fractions of seed kernels, albumins constituted the major storage proteins (69.7%). The kernel proteins were rich in essential amino acids, particularly sulphur‐containing amino acids, and their values appeared to be higher than the FAO/WHO (1990) reference protein for a 2–5‐year‐old growing child and soybean, and comparable to hen egg. Seed kernel lipids contained high levels of unsaturated fatty acids, oleic and linoleic acids, which accounted for 83% of the total fatty acid recovered. The kernel exhibited high trypsin and chymotrypsin inhibitor activities (96.65 mg TI g^?1 and 30.02 CIU mg^?1 sample respectively) in addition to containing phenolics, phytic acid, lectins and oligosaccharides. Another major toxic constituent was identified as a group of triterpenoid saponins (3.21%), which had high haemolytic activity (HeU) against cattle erythrocytes and caused high mortality in fish. The in vitro digestibility of the kernel protein was low (67%). © 2001 Society of Chemical Industry     

Compositional variation in β‐carotene content,carbohydrate and antioxidant enzymes in selected banana cultivars

Banana is one of the most important tropical fruits, and India ranks first in its world production. Banana cultivars rich in provitamin A carotenoids may offer a potential food source for alleviating vitamin A deficiency, particularly in developing countries. With a view to exploit banana peels as a source of valuable components, in the present study, proximate composition, carotenoids, beta‐carotene and some anti‐oxidative enzymes as well as carbohydrate content of selected Indian banana varieties were determined. Karpooravalli cultivar of banana showed the maximum accumulation of carotenoid content in the non‐edible (68 μg g^?1 d.w.) portion of banana, while being the second highest in beta‐carotene content (143.12 μg per 100 g). However, Red Banana ranked highest in total carotenoid contents for pulp (4 μg g^?1 d.w.) and beta‐carotene was estimated to be the highest in the case of peels (241.91 μg per 100 g) and in pulp (117.2 μg per 100 g). Karpooravalli cultivar of banana is also rich in carbohydrate content in terms of total starch (1786.0 μg g^?1 d.w. in peels and 544.85 μg g^?1 d.w. in pulp) and sugars (53.53 μg g^?1 d.w. in peels and 39.05 μg g^?1 d.w. in pulp). The catalase enzyme activity in these peels ranged from 5.66 to 35.57 nmol min^?1 mg^?1 proteins and was found at a higher level in cultivar Poovan, while the ascorbate peroxidase showed the range of 2.25 to 6.22 μmol min^?1 mg^?1 proteins. The peels of cultivars Red Banana and Karpooravalli are rich source of bioactive compounds, such as carotenoids (beta‐carotene), anti‐oxidative enzymes and carbohydrate contents.     

Optimisation of Glucose Biosensors Based on Sol–Gel Entrapment and Prussian Blue-Modified Screen-Printed Electrodes for Real Food Analysis

In this study, we report the construction of amperometric screen-printed glucose biosensors for food analysis by using two procedures for Prussian Blue (PB) deposition and different membranes for enzymatic immobilisation. The comparison between the screen-printed electrodes modified with PB by electrochemical and chemical deposition showed higher analytical performance (detection limit of 1 μM, linear range from 0.5 to 500 μM and a sensitivity of 823 μA mM^?1 cm^?2) when the latter was employed. Then, the immobilisation of glucose oxidase (GOD) by silica sol–gel and polyvinyl alcohol (PVA) hydrogel was performed on electrochemically modified PB electrodes. The electrochemical response of two glucose biosensors was evaluated by flow injection analysis. Biosensors constructed by silica sol–gel entrapment showed a wider linear range (0.005–1 mM) and a detection limit (0.02 mM) that was 10-fold lower than using entrapped GOD in PVA. The selected glucose biosensor showed negligible interference from ascorbic acid when the Nafion membrane was used to cover the PB-modified electrode surface. Additionally, it exhibited an operating lifetime of 8 h under continuous glucose injections ranging from 0.01 to 2 mM. Finally, the biosensor was applied for specific determination of glucose in red and white wines, juices and dried fruit.     

Application of Box–Behnken Design in the Optimization of In Situ Surfactant-Based Solid Phase Extraction Method for Spectrophotometric Determination of Quinoline Yellow in Food and Water Samples

In this work, a simple, rapid and sensitive method using in situ surfactant-based solid phase extraction (ISS-SPE) combined with UV–vis spectrophotometry has been developed for the preconcentration and determination of trace amounts of quinoline yellow in food and water samples. The Box–Behnken design was employed to optimize the extraction efficiency. The variables of interest were pH, surfactant volume, extraction time and NaI volume. In the optimal conditions, the calibration graph was linear in the range of 10.0–750 μg L^?1 with a correlation coefficient of 0.9982. The limit of detection (LOD) was 2.1 μg L^?1, and the preconcentration factor was calculated to be 51.8.