Amino Acid Composition and Its Change in Raw and Granulated Potatoes During Processing

Total amino acids and composition of raw and cooked tubers were determined by gas-liquid and ion-exchange column chromatography. Peeled raw potato, after reaching the end product state, lost 40% of its free amino acid pool. Processing into dehydrated granules by the freeze-thaw process caused only small losses in total amino acids and little change in their composition. There was only a 4.5% destruction of essential amino acids and a total loss of 2.1% of non-essential amino acids, excluding aspartic and glutamic acids which comprised 48% of peeled and sliced potatoes.     

Quality Index, Consumer Acceptability, Bioactive Compounds, and Antioxidant Activity of Fresh-Cut "Ataulfo" Mangoes (Mangifera Indica L.) as Affected by Low-Temperature Storage

ABSTRACT:  To measure bioactive compound losses due to minimal processing, mature green fresh-cut mangoes ( Mangifera indica L.) cv. "Ataulfo" were subjected to an antioxidant treatment and stored at 5 °C during 15 d. Quality index, total phenols, flavonoids, β-carotene, ascorbic acid, vitamin E, and antioxidant activity were measured during the storage period of fruits. Antioxidant capacity was estimated using ORAC_FL, TEAC, and DPPH assays. The dipping treatments with ascorbic acid (AA) + citric acid (CA) + CaCl₂ affected positively quality delaying deterioration of fresh-cut mango as compared with whole fruit. However, dipping treatment affected the consumer preferences of fresh-cut mangoes. The highest vitamin C, β-carotene, and vitamin E losses were observed after 10 d, being similar in whole and fresh-cut mangoes. The antioxidant activity was not significantly affected by storage time. We conclude that fresh-cut mangoes retained their bioactive compound content during storage and their antioxidant and nutritional properties make them a good source of these compounds.     

New Kinetic Approach to the Evolution of Polygalacturonase (EC 3.2.1.15) Activity in a Commercial Enzyme Preparation Under Pulsed Electric Fields

ABSTRACT:  The effect of pulsed electric fields (PEF) on polygalacturonase (PG) activity in an aqueous solution of a commercial enzyme preparation was studied. Monopolar square wave pulses of 4 μs were delivered to the solution, which circulated through tubular chambers with 2 stainless steel electrodes in continuous operation. The electric field intensities ( E ) and treatment time ( t ) ranged within 15 to 38 kV cm⁻¹ and 300 to 1100 μs, respectively. Although important reduction of the PG activity could be achieved (up to 76.5% at E = 38 kV cm⁻¹ and t = 1100 μs), the experimental data showed certain enhancement of PG activity under soft conditions (up to 110.9% at E = 15 kV cm⁻¹ and t = 300 μs). A kinetic mechanism involving 2 consecutive irreversible first-order steps was developed to describe and explain the experimental data. The tested model exhibited high accuracy in respect of the experimental data and the error of the model was lower than 4.4%. The kinetic rate constant of the first ( k ₁) and second step ( k ₂), ratio between the activities of intermediate and native forms of the enzyme (Λ), and other quantities related to the model, were obtained within a Bayesian framework. k ₁ resulted independent of the E applied and considerably greater in magnitude order ( k ₁ mean = 6 μs⁻¹) with respect to k ₂, which was dependent on the applied E (mean values ranged from 489E-6 μs⁻¹ at E = 38 kV cm⁻¹ to 1215E-6 μs⁻¹ at 38 kV cm⁻¹). The dependency of k ₂ toward E was described using an exponential relationship.     

Quantum Corrected Full-Band Cellular Monte Carlo Simulation of AlGaN/GaN HEMTs

A full-band Cellular Monte Carlo (CMC) approach is applied to the simulation of electron transport in AlGaN/GaN HEMTs with quantum corrections included via the effective potential method. The best fit Gaussian parameters of the effective potential method for different Al contents and gate biases are calculated from the equilibrium electron density. The extracted parameters are used for quantum corrections included in the full-band CMC device simulator. The charge set-back from the interface is clearly observed. However, the overall current of the device is close to the classical solution due to the dominance of polarization charge.     

Kinetic Studies During Enzyme Hydrolysis of Potato and Cassava Starches

The hydrolysis of raw potato and cassava starches by bacterial α-amylase depends on the time of action, temperature and on the specific starch involved. The molecular weight of the trade α-amylase (Termamyl 60L), determined by SDS-PAGE, was found to be 55–65 kDa. The properties of α-amylase such as kinetic parameters, inhibition, stability, and thermostability were studied. The constants K_m and maximum reaction rate V_max for α-amylase were fitted to Michaelis-Menten models with these two starches. Differences in response of potato and cassava starches to hydrolysis by Termamyl 60L can explain differences found in K_m and V_max values and inhibition properties.     

Antioxidant activities and bioactive components in some berries

The objective of this study was to evaluate the antioxidant and binding effects of gooseberry, a less-studied berry, and to compare with blueberry and cranberry in the model of interaction with human serum albumin (HSA). The relationship between the scavenging properties of dietary polyphenols of the selected berries and their affinities for HSA were investigated by fluorescence analysis. In order to perform the extraction and identification of the antioxidants present in the samples, different types of extraction solvents were used, such as water, ethyl acetate, and diethyl ether. The polyphenols, tannins, anthocyanins and ascorbic acid contents, and the total antioxidant capacities (TACs) of the berry extracts were assessed by using ESI–MS, FTIR, and radical scavenging assays. The contents of bioactive compounds and the levels of TACs in water extracts differed significantly and were the highest in water extracts in comparison with other extracts in all the investigated berries (P < 0.05). Gooseberry water extracts contained: polyphenols (mg GAE/g DW)—5.37 ± 0.6, tannins (mg CE/g DW)—0.71 ± 0.2, anthocyanins (mg CGE/g DW)—12.0 ± 1.2, ascorbic acid (mg AA/g DW)—5.15 ± 0.5, and TACs (μMTE/g DW) by ABTS and FRAP assays were 15.53 ± 1.6 and 6.51 ± 0.7, respectively. In conclusion, the bioactivity of gooseberry was lower than blueberries and cranberries. The antioxidant and binding properties of gooseberries in comparison with widely consumed blueberries and cranberries can be used as a new source for food supplementation.     

Comparative content of some phytochemicals in Spanish apples,peaches and pears

Dietary fibre, total polyphenols and phenolic acids in Spanish apples, peaches and pears were analysed and compared with their total radical‐trapping antioxidative potential (TRAP). There were no significant differences in the content of dietary fibre among the studied fruits. The content of total polyphenols was 2.4 ± 0.4, 2.1 ± 0.3 and 6.9 ± 0.7 g kg^?1 in peeled fruits and 4.7 ± 0.4, 4.5 ± 0.4 and 11.1 ± 1.2 g kg^?1 in their peels for peaches, pears and apples respectively. The contents of dietary fibre, total polyphenols, caffeic, p‐coumaric and ferulic acids and the TRAP values were significantly (P < 0.05) higher in peels than in peeled fruits. The contents of all studied compounds and the TRAP values were significantly higher in peeled apples and their peel than in peaches and pears. We observed a strong correlation between the contents of total polyphenols and phenolic acids and the total radical‐trapping antioxidative potential in all three fruits. The relatively high content of dietary fibre, the highest contents of total polyphenols, caffeic, p‐coumaric and ferulic acids and the highest value of TRAP make apples preferable among the studied fruits for dietary prevention of atherosclerosis and other diseases. © 2002 Society of Chemical Industry     

Effect of hesperidin and naringin on the plasma lipid profile and plasma antioxidant activity in rats fed a cholesterol‐containing diet

The objective of this study was to compare the influence of hesperidin and naringin, the main flavonones of orange and grapefruit, on plasma lipid profile and antioxidant activity in rats fed a cholesterol‐containing diet. Sixty male Wistar rats were randomly divided into six groups of 10, named Control, Hesperidin, Naringin, Chol, Chol/Hesperidin and Chol/Naringin. The Control group was fed a basal diet (BD) and 1–2 mL of distilled water. To the BD of the other five groups were added 0.1–0.2 mg of hesperidin dissolved in 1–2 mL of distilled water (Hesperidin group), 0.46–0.92 mg of naringin in 1–2 mL of water (Naringin group), 1% of non‐oxidised cholesterol (NOC) and 1–2 mL of water (Chol), 1% of NOC and 0.1–0.2 mg of hesperidin in 1–2 mL of water (Chol/Hesperidin), 1% of NOC and 0.46–0.92 mg of naringin in 1–2 mL of water (Chol/Naringin). After 30 days of the experiment it was found that the diets supplemented with hesperidin and naringin increased the plasma antioxidant activity. In conclusion, diets supplemented with hesperidin and naringin significantly hindered the increase in plasma lipid levels caused by cholesterol feeding. Hesperidin and naringin, bioactive compounds of citrus fruits, are powerful plasma lipid lowering and plasma antioxidant activity increasing flavonones. Copyright © 2007 Society of Chemical Industry     

The Effects of Enzyme Hydrolysis on the Properties of Potato,Cassava and Amaranth Starches

X-ray diffraction method and differential scanning calorimetry were used to study the effects of enzyme hydrolysis on physico-chemical properties of potato, cassava and amaranth starches. Various hydrolysis procedures and different sources of enzymes were employed. The highest percentage of hydrolysis was obtained using the bacterial thermostable α-amylase following by the saccharification with amyloglucosidase. Enzyme treatment showed decrease in the degree of crystallinity of all hydrolyzed starch samples of A-type crystals. B-and C-types were weakened upon enzymatic hydrolysis at 60°C and completely dissappeared at 100°C. The gelatinization endotherm decreased for samples with low degree of crystallization and disappeared in samples with amorphous stage.     

Characterization of blond and Star Ruby (red) Jaffa grapefruits using antioxidant and electrophoretic methods

Antioxidant and electrophoretic methods were used to characterize the quality differences between blond and Star Ruby (red) grapefruits. Dietary fibre, minerals and trace elements, total polyphenols, anthocyanins, flavonoids, phenolic and ascorbic acids were also determined. The antioxidant potential of red grapefruit was significantly higher than that of the blond fruit (P < 0.05) and correlated well with the total polyphenols (R² from 0.8456 to 0.9711). In both the cultivars studied, thirty‐two electrophoretic bands were detected [sodium dodecyl‐polyacrylamide gel eletrophoresis (SDS‐PAGE)]. The main electrophoretic bands occurred between 20 and 43 kDa in both grapefruits with few minor differences between the varieties. Our findings indicate the following (i) red grapefruit is preferable: it has a higher concentration of bioactive compounds and antioxidant potential than the blond; (ii) 1, 1‐diphenyl‐2‐picrylhydrazyl (DPPH) test is a more sensitive method for the determination of antioxidant potential; (iii) there are some minor differences in electrophoretic patterns; (iv) antioxidant and electrophoretic methods are a good combination for characterization of differences of the same citrus fruits.