Effects of electrode materials on the degradation,spectral characteristics,visual colour,and antioxidant capacity of cyanidin-3-glucoside and cyanidin-3-sophoroside during pulsed electric field (PEF) treatment

The effects of three electrode materials – stainless steel (SS), pure titanium (PT), and titanium-based alloy (TA) – on the PEF-induced degradation, spectral characteristics, visual colour, and antioxidant capacity of cyanidin-3-glucoside (Cy-3-glc) and cyanidin-3-sophoroside (Cy-3-soph) were studied. Cy-3-glc and Cy-3-soph were degraded by PEF; SS retained Cy-3-glc and Cy-3-soph the most, while PT and TA led to greater degradation. Cy-3-glc was more susceptible to PEF than Cy-3-soph. The intensity of UV–Vis spectra absorbance at 520 nm decreased, but it increased at 280 and 325 nm after PEF when using the three electrodes. Their lightness (L^∗) exhibited no changes with SS, but showed a significant reduction with PA and TA. Redness (a^∗) significantly decreased with all three electrodes; the yellowness (b^∗) of Cy-3-glc with PA and TA, and of Cy-3-soph with SS, were also significantly reduced. The antioxidant capacity of Cy-3-glc and Cy-3-soph with SS, in contrast to PT and TA, was enhanced after PEF.     

Effects of various sulphuring methods and storage temperatures on the physical and chemical quality of dried apricots

The effects of different sulphuring methods, i.e. sulphuring by “burning the elemental sulphites (BES),” “SO₂ gas from liquified SO₂ tank (SG)” and “dipping into sodium metabisulphite solution (DSM)” on the colour (brown colour formation and carotenoid degradation) and the loss of SO₂ in apricots from Hac?halilo?lu and Kabaa?? varieties stored at 5, 20 and 30 °C for a year were investigated. There were significant effects of variety, sulphuring method and especially storage at 30 °C on the brown colour formation and loss of SO₂ (P < 0.05). As storage temperature–time increased, β-carotene content decreased. Sulphuring methods and variety did not show significant effect on β-carotene content (P > 0.05). The changes in L^∗, b^∗ and C^∗ values were directly associated with β-carotene content and browning values. The most suitable method for all samples, except for Hac?halilo?lu variety stored at 30 °C (BES), is SG, because the samples retained their attractive golden yellow colour during storage.     

Effect of low voltage electrical stimulation on biochemical and quality characteristics of Longissimus thoracis muscle from one-humped Camel (Camelus dromedaries)

The effects of electrical stimulation (90 V) 20 min post mortem on meat quality and muscle fibre types of four age group camels (1–3, 4–6, 7–9, 10–12 years) camels were assessed. Quality of the Longissimus thoracis at 1 and 7 days post mortem ageing was evaluated using shear force, pH, sarcomere length, myofibrillar fragmentation index, expressed juice, cooking loss and L^∗, a^∗, b^∗ colour values. Age of camel and electrical stimulation had a significant effect on meat quality of L. thoracis. Electrical stimulation resulted in a significantly (P < 0.05) more rapid pH fall in muscle during the first 24 h after slaughter. Muscles from electrically-stimulated carcasses had significantly (P < 0.05) lower pH values, longer sarcomeres, lower shear force value, higher expressed juice and myofibrillar fragmentation index than those from non-stimulated ones. Electrically-stimulated meat was significantly (P < 0.05) lighter in colour than non-stimulated based on L^∗ value. Muscles of 1–3 year camels had a significantly (P < 0.05) lower shear force value, and pH, but longer sarcomere, and higher myofibrillar fragmentation index, expressed juice, and lightness colour (L^∗) than those of the 10–12 years camels. The proportions of Type I, Type IIA and Type IIB were 25.0, 41.1 and 33.6%, respectively were found in camel meat. Muscle samples from 1–3 year camels had significantly (P < 0.05) higher Type I and lower Type IIB fibres compared to those from 10–12 year camel samples. These results indicated that age and ES had a significant effect on camel meat quality.     

Analytical application of food dye Sunset Yellow for the rapid kinetic determination of traces of copper(II) by spectrophotometry

A sensitive and rapid kinetic method for trace determination of Cu(II) was developed and validated, based on its catalytic effect on the oxidation of disodium-6-hydroxy-5-[(4-sulphophenyl)azo]-2-naphtalenesulphonic acid (wide used, food colour “Sunset Yellow FCF”, E110, in text selected as SY) by hydrogen peroxide in borate buffer at pH 10.5. The reaction was monitored spectrophotometrically by measuring the decrease in the absorbance of SY at 478.4 nm. The optimum operating conditions regarding concentration of reagents, pH and temperature were established. The calibration curve was linear up to 318 ng mL⁻¹ of Cu(II) and the limit of detection (3σ/S) is 5.0 ng mL⁻¹, and limit of quantification (10σ/S) is 16.67 ng mL⁻¹. The proposed kinetic procedure was successfully applied to monitoring of the concentration of Cu(II) in fruit, wine and milk samples from different areas. The results obtained by the proposed kinetic procedure were compared by those obtained by ICP-OES method, and shown good agreement. The proposed kinetic method could be used for monitoring of quality of drinks or fruit depending on Cu(II) concentration, because of its important role as nutritional element.     

Kinetic model of apple juice enzymatic browning in the presence of cyclodextrins: The use of maltosyl-β-cyclodextrin as secondary antioxidant

Enzymatic browning reactions limit the commercial shelf life of apple juice, so that colour preservation during storage is one of the main objectives of fruit processors. In this paper, the colour of fresh apple juice was evaluated in the presence of different types of cyclodextrins (CDs) (α-CD, β-CD, γ-CD and maltosyl-β-CD), compounds that bind or complex polyphenol oxidase substrates. The effectiveness of CDs as browning inhibitors was determined as the difference between the colours observed in the CD-treated sample and the controls, using the colour space CIE-L^∗, a^∗, b^∗ system. Although the effect of CDs on apple juice enzymatic browning has been studied, the action mechanism involved remains a subject of controversy. In this work, we have kinetically modelled apple juice enzymatic browning in the absence and presence of maltosyl-β-CD. The complexation constant between the mixtures of diphenols present in apple juice and maltosyl-β-CD was calculated (K_c = 4.09 mM⁻¹). Different concentrations of maltosyl-β-CD modified the evolution of lightness (L^∗), total colour (ΔE^∗) and hue angle (H^∗) because of the higher affinity constant it shows for the compounds responsible for apple juice browning than do α-CD, β-CD and γ-CD. Moreover, in this paper we show that maltosyl-β-CD can enhance the ability of ascorbic acid to prevent the enzymatic browning due to the protective effect of maltosyl-β-CD against ascorbic acid oxidation. Hence, maltosyl-β-CD seems to act as a “secondary antioxidant”, reducing apple juice browning and enhancing the naturally occurring antioxidant capacity of a food.     

Carotenoid contents of extruded and non-extruded sweetpotato flours from Papua New Guinea and Australia

Carotenoid contents of extruded and non-extruded flours of Papua New Guinean and Australian sweetpotato cultivars were studied, using spectrophotometry and high performance liquid chromatography (HPLC). The cultivars differed (p < 0.05) in their total carotenoid and β-carotene contents, and the Original Beauregard cultivar had the highest total carotenoid and β-carotene contents among the cultivars. The spectrophotometry (84–1720 μg/g solids) method generally over-estimated the total carotenoid content compared to the more specific HPLC (23–355 μg/g solids) method. Extrusion significantly (p < 0.05) decreased the ΔL^∗ Hunter colour values, while the Δa^∗, Δb^∗, total colour change (ΔE), chroma (CR), and browning indices (BI) increased. With the extruder and screw configuration used, extrusion at 40% moisture and 300 rpm screw speed retained carotenoid maximally at more than 80%. This study reports, for the first time, carotenoids of flours from south Pacific sweetpotato cultivars, and carotenoid retention during extrusion.     

Composition and color stability of carbon monoxide treated dried porcine blood

Color stability of swine blood was studied over 12 weeks of storage in plastic bags, after pH (7.40, 6.70, or 6.00) adjustment, saturation with carbon monoxide (CO) and spray-drying. CO-treated dried blood presented a redder color and higher reflectance between 610 and 700 nm, compared to a brownish-red color and lower reflectance of untreated samples. As indicated by reflectance spectra, blood pH adjustment did not influence (P > 0.05) the initial color of dried blood but influenced (P < 0.05) its color stability (browning index). During storage, CO-treated blood showed a reduction in reflectance percentages as well as in CIE L^∗ and a^∗ values, which was more pronounced in polyethylene (OTR = 4130 cm³/m²/day/atm) packaged samples. After 12 weeks of storage, CO-treated samples packaged in high OTR bags presented color indexes similar to those of the untreated dried samples. CO-treated samples packaged in nylon-polyethylene (OTR = 30–60 cm³/m²/day/atm) bags showed a smaller rate of discoloration and color difference (ΔE^∗) between the CO-treated and untreated samples. Even with some darkening, packaging CO-treated dry blood in low OTR bags still gives an acceptable reddish color after 12 weeks of storage while untreated dry blood has a brownish color just after drying.     

Neriifolin S, a dimeric serine protease from Euphorbia neriifolia Linn.: Purification and biochemical characterisation

A dimeric serine protease Neriifolin S of molecular mass 94 kDa with milk clotting activity has been purified from the latex of Euphorbia neriifolia by anion exchange and size-exclusion chromatography. It hydrolyses peptidyl substrates l-Ala-pNA with highest affinity (K_m of 0.195 mM) and physiological efficiency (K_cat/K_m of 144.5 mM s). Enzyme belongs to the class of neutral proteases with pI value of 6.8, optimal proteolytic activity displayed at pH 9.5 and temperature 45 °C. Its proteolytic activity is strongly stimulated in the presence of Ca⁺² ions and exclusively inhibited by serine protease inhibitors. Enzyme is fairly stable toward chemical denaturants, pH and temperature. The apparent T_m, was found to be 65 °C. Thermal inactivation follow first order kinetics with activation energy (Ea), activation enthalpy (ΔH∗), free energy change (ΔG∗) and entropy (ΔS∗) of 27.54 kJ mol⁻¹, 24.89 kJ mol⁻¹, −82.34 kJ mol⁻¹ and 337.20 J mol⁻¹ K⁻¹.     

Application of computer vision technique for on-line monitoring of shrimp color changes during drying

The effects of drying temperature and drying medium velocity on color change kinetics of shrimp viz. lightness (L^∗), redness (a^∗), yellowness (b^∗), total color difference (ΔE), chroma (CH), hue angle (H°), and browning index (BI) were on-lineally investigated. Drying experiments were carried out on dryer equipped with computer vision systems using hot air drying (HAD) temperatures of 50–90 °C and superheated steam drying (SSD) temperatures of 110–120 °C at drying medium velocities of 1–2 m/s. Zero-, first-order, and fractional conversion models were utilized to describe the color changes of shrimps and the fractional conversion model successfully tracked the experimental data. The results showed that the color parameters were significantly influenced by the studied parameters. Lightness of the samples decreased, while other color parameters increased as drying proceeded. Generally, increasing drying medium temperature decreased L^∗ and H°, whereas increased other color parameters. The color characteristic of the SSD finished products were acceptable than the HAD processed samples. Finally, dimensionless moisture content of shrimps during drying was accurately correlated to the color parameters and drying time using a quadratic regression model. Moisture ratio had strong relationship with the lightness change compared with the redness and yellowness variations.     

Analytical applications of 2,6-diacetylpyridine bis-4-phenyl-3-thiosemicarbazone and determination of Cu(II) in food samples

New synthesized reagent 2,6-diacetylpyridine bis-4-phenyl-3-thiosemicarbazone (2,6-DAPBPTSC) is proposed as a sensitive and selective analytical reagent for the spectrophotometric determination of copper(II) at pH 3.0 to form a yellowish orange colored 1:1 chelate complex. The maximum absorbance was measured at 370 nm. This method obeys Beer’s law in the concentration range 0.63–6.30 g ml⁻¹ and the correlation coefficient of Cu(II)–2,6-DAPBPTSC complex is 0.942, which indicates an adequate linearity between the two variables with good molar absorptivity and Sandell’s sensitivity, 0.847 × 10⁴ l mol⁻¹ cm⁻¹ and 0.0075 g cm⁻², respectively. The instability constant of complex calculated from Asmus′ method is 1.415 × 10⁻⁴ at room temperature. The precision and accuracy of the method is checked with calculation of relative standard deviation (n = 5), 0.777% and the detection limit value is 0.0056 g ml⁻¹. The interfering effect of various cations and anions has also been studied. The method was successfully applied for the determination of Cu(II) in food samples. The performance of present method was evaluated in terms of Student ‘t’ test and Variance ‘f’ test, which is indicates the significance of present method is an inter comparison of the experimental values, using atomic absorption spectrometer (AAS).     

A reappraisal of traditional apple cultivars from Southern Italy as a rich source of phenols with superior antioxidant activity

Few literature data are available on the nutraceutical properties of little widespread local apple cultivars. Such lack of information prevents exploitation of these germplasms for genetic improvement of new cultivars and for the re-evaluation of local agricultural products, which may attract a large share of consumers oriented towards natural food evoking ancient flavours. In this work eight traditional apple cultivars of Southern Italy were analysed in terms of phenolic composition and free radical scavenging activity in comparison with commercial “Annurca” and “Gold Chief® Gold Pink∗” cultivars. HPLC-UV-MS analysis of methanol extracts of the cultivars under examination showed significant differences in phenol distribution within the three main classes of hydroxycinnamates, dihydrochalcones, and flavan-3-ols. Such differences were found to be associated with the antioxidant activities as determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. A good correlation was observed between the percentage of reduced DPPH and the total phenol content (R = 0.79). Among all phenol classes, the flavan-3-ol content showed the highest correlation (R = 0.77). Almost all of the traditional cultivars examined exhibited a much higher phenol content (2- to 7-fold) and hydrogen donor activity (1.5- to 4-fold) than widely consumed cultivars like “Annurca” and “Gold Chief® Gold Pink∗”.     

Effect of sonication on colour,ascorbic acid and yeast inactivation in tomato juice

Power ultrasound is recognised as a potential non-thermal technique to inactivate micro-organisms pertinent to fruit juices. In this study tomato juice was sonicated at different amplitude levels (24.4–61.0 μm) at a constant frequency of 20 kHz for treatment times (2–10 min) and pulse durations of 5 s on and 5 s off. Hunter colour values (L∗, a∗ and b∗), pH, °Brix, titratable acidity, ascorbic acid and yeast inactivation were measured. No significant differences (p < 0.05) in pH, °Brix or titratable acidity were observed. Regression modelling was used to investigate the main effects of amplitude level and treatment time. Prediction models were found to be significant (p < 0.05) with low standard errors and high coefficients of determination (R²). Model predictions for critical quality parameters of Hunter colour values (L∗, a∗ and b∗), ascorbic acid and yeast inactivation were closely correlated with the experimental results obtained.     

Antioxidant capacity,total phenolics,glucosinolates and colour parameters of rapeseed cultivars

The antioxidant capacity of twenty nine rapeseed varieties was determined by using ferric reducing antioxidant power (FRAP) and 2,2′-diphenyl-1-picrylhydrazyl (DPPH) methods. Mean FRAP (3190–6326 μmol Trolox/100 g) and DPPH (3194–6346 μmol Trolox/100 g) values for methanolic extracts of rapeseed cultivars did not differ significantly. Moreover, the total content of phenolics (756–1324 mg sinapic acid/100 g), glucosinolates (4.2–87.5 μmol/g, respectively), erucic acid (0.0–56.1%) and colour parameters of the studied rapeseed cultivars were analysed. Antioxidant capacity determined by FRAP and DPPH methods correlated significantly with total phenolic content (TPC) in rapeseed cultivars (r = 0.9332, 0.9339, p < 0.001). Also, significant, inverse correlations were found between antioxidant capacity, total phenolics and luminosity (L^∗) or red colour intensity (a^∗) of rapeseed cultivars. Principal component analysis (PCA) allowed the rapeseed varieties to be differentiated based on their antioxidant capacities, total amounts of phenolics, glucosinolates, erucic acid and colour parameters.     

Initial evaluation of a field-friendly incubation procedure for the colorimetric assay of cassava linamarase

The Cooke colorimetric assay of cassava linamarase activity is temperature- and time-inflexible, making “real time” monitoring of linamarase activity in remote cassava-processing sites practically impossible. A modified incubation procedure is described, in which the 30 °C linamarase incubation step is terminated through acidification, yielding a stable cyanohydrin solution. Using partially purified linamarase as a “standard extract”, the solution – held for up to 21 days at ambient/refrigeration temperatures before colorimetry – showed reductions of up to 21% compared with the standard Cooke assay. In a separate trial, a strong linear relationship (r² > 0.95) was observed between recorded linamarase activity values and incubation temperature in the 25–40 °C range, indicating that incubation may take place in remote processing sites without a water bath, and resulting data may reliably be adjusted in keeping with the standard 30 °C incubation assay. The novel procedure thus appears to offer a satisfactory “field-friendly” means of assaying linamarase activity.     

Amaranthus hypochondriacus and Amaranthus caudatus germplasm: Characteristics of plants,grain and flours

In the present study, the plant, grain and flour characteristics of 48 Amaranthus hypochondriacus and 11 Amaranthus caudatus lines are reported. A. hypochondriacus grains had a higher thousand kernel weight (0.62–0.88 g), a creamish yellow colour (L∗ = 61.38–68.29, b∗ = 5.26–6.8 and a∗ = 19.71–23.84), whereas A. caudatus grains had a lower thousand kernel weight (0.46–0.70 g) and a reddish-brown colour (L∗ = 47.1–51.2, b∗ = 11.82–14.02 and a∗ = 7.72–13.29). The A. caudatus lines had a higher protein content, fat content and tendency for retrogradation, and lower α-amylase activity as compared to A. hypochondriacus lines. The Amaranthus lines with higher a∗-values and lower thousand kernel weight, L∗- and b∗-values, had a higher fat, crude fibre and protein content. The correlation of fat and crude fibre content with the thousand kernel weight, L∗-, a∗- and b∗-values, was significant. The A. hypochondriacus lines showed higher pasting temperature, and lower peak viscosity, breakdown and setback, as compared to the A. caudatus lines. The result reflected that the lines with higher α-amylase activity showed a lower peak viscosity, breakdown, final viscosity and gel hardness, and a higher pasting temperature.     

Evaluation of the non-enzymatic browning in thermally processed apple juice by front-face fluorescence spectroscopy

Fresh apple juice was heated at 95 °C for 30 and 60 min, and then stored for 6 days for obtaining different extent of non-enzymatic browning. Front-face fluorescence excitation–emission-matrix (EEM) with excitation at 355 and 400 nm and emission ranges of 385–600, and 430–600 nm was used to measure the juice samples. The sign test pointed out an enhanced sensitivity of EEM compared to commonly used browning indicators, such as non-enzymatic browning index (NEBI), color readings in L^∗a^∗b^∗ space, and the concentration of 5-hydroxymethylfurfural (HMF). Using the fluorescence data, the correctness of classifications of fresh juice, heated juice, and stored juice were >85%. Multivariate analyses were applied to study the relations of fluorescence emission spectra and common indicators. For predicting NEBI, b^∗, and HMF, the correlation coefficients were >0.80. Resulting, the spectroscopic analyses of fluorescent neoformed products such as HMF provide a feasible approach to monitor non-enzymatic browning of juice.     

Modelling the effect of water immersion thermal processing on polyacetylene levels and instrumental colour of carrot disks

C₁₇ polyacetylenes are a group of bioactive compounds present in carrots which have recently gained scientific attention due to their cytotoxicity against cancer cells. In common with many bioactive compounds, their levels may be influenced by thermal processes, such as boiling or water immersion. This study investigated the effect of a number of water immersion time/temperature combinations on concentrations of these compounds and attempted to model the changes. Carrot samples were thermally treated by heating in water at temperatures from 50–100 °C and holding times of 2–60 min. Following heating, levels of falcarinol (FaOH), falcarindiol (FaDOH), falcarindiol-3-acetate (FaDOAc) and Hunter colour parameters (L^∗, a^∗, b^∗) were determined. FaOH, FaDOH, FaDOAc levels were significantly reduced at lower temperatures (50–60 °C). In contrast, samples heated at temperatures from 70–100 °C exhibited higher levels of polyacetylenes (p < 0.05) than did raw unprocessed samples. Regression modelling was used to model the effects of temperature and holding time on the levels of the variables measured. Temperature treatment and holding time were found to significantly affect the polyacetylene content of carrot disks. Predicted models were found to be significant (p < 0.05) with high coefficients of determination (R²).     

Spectrophotometric determination of zinc in foods using N-ethyl-3-carbazolecarboxaldehyde-3-thiosemicarbazone: Evaluation of a new analytical reagent

N-ethyl-3-carbazolecarboxaldehyde-3-thiosemicarbazone (ECCT) is proposed as a new sensitive reagent for the extractive spectrophotometric determination of zinc(II). The ECCT forms yellow colored species of zinc(II) at pH range 3.0–5.5 and the complex was extracted into benzene. The Zn(II)–ECCT complex shows maximum absorbance at 420 nm with molar absorptivity and Sandell’s sensitivity being 1.55 × 10⁴ lit mol⁻¹ cm⁻¹ and 4.212 × 10⁻³ μg cm⁻², respectively. The system obeys Beer’s law in the range of 0.4–6.0 mg/l, with an excellent linearity in terms of correlation coefficient value of 0.999. Most of the common metal ions generally found associated with zinc do not interfere. The repeatability of the method was checked by finding relative standard deviation (RSD). The developed method has been successfully employed for the determination of zinc(II) in foods. Various certified reference materials (NIST 1573, NBS 1572 and NIST SRM 8435) have been tested for the determination of zinc for the purpose of validation of the present method.     

Effect of phenolic compounds on the properties of porcine plasma protein-based film

Properties of porcine plasma protein-based film incorporated with tannic acid, caffeic acid and ferulic acid at different concentrations (1–3% (w/w) of protein content) were studied. Film-forming solution (FFS) containing 3% protein (w/v) and 70% glycerol (w/w of protein content) was preheated at 70 °C for 30 min and adjusted pH to 10 followed by the addition of phenols and film casting. Tensile strength (TS) of resulting film increased by 123.3, 194.3 and 19.5% and elongation at break (EAB) increased by 71.1, 86.3 and 10.2%, respectively, compared with the control film, when tannic acid, caffeic acid and ferulic acid at a level of 3% was added. The use of all phenolic compounds slightly increased water vapor permeability (WVP) of resulting films (p < 0.05). The increases in a^∗- and b^∗-values of films were observed as the higher concentrations of tannic acid and caffeic acid were used. This was associated with the lowered transparency of resulting films. FFS containing 3% caffeic acid with prior oxygenation, especially with pH 10, yielded the film with increased TS but lowered EAB (p < 0.05). Oxygenation of FFS was associated with the lower L^∗-value and higher a^∗-value of resulting films. Therefore, phenolic compounds could be used as natural cross-linkers which affected the properties of porcine plasma protein-based film differently.     

Yellow discoloration of the liposome system of cuttlefish (Sepia pharaonis) as influenced by lipid oxidation

Lipid oxidation, discoloration, loss of amine groups and pyrrolization of the liposome systems of cuttlefish (Sepia pharaonis) in the presence of FeCl₃ and ascorbic acid were studied. Thiobarbituric acid-reactive substances (TBARS) and the b^∗-value of cuttlefish liposomes increased with a coincidental decrease in amine groups when the incubation temperatures (0, 4, 25, and 37 °C) and incubation times (0–24 h) were increased (p < 0.05). As lipid oxidation and yellow pigment formation in the cuttlefish liposome proceeded, a loss of amine groups and pyrrolization were also detected. The effects of FeCl₃ and ascorbic acid, at different concentrations, on TBARS production, b^∗-value, loss of amine groups and pyrrolization of cuttlefish liposome were also investigated. Both FeCl₃ and ascorbic acid showed prooxidative effects in cuttlefish liposome in a concentration-dependent manner. Sodium chloride (0–2%) reduced TBARS, b^∗-values and pyrrole compounds. These results suggest a positive correlation between lipid oxidation and the development of yellow pigments in cuttlefish phospholipids.