Extraction and characterisation of pectin methylesterase from black carrot (Daucus carota L.)

This study was carried out to determine some of the biochemical properties of pectin methylesterase (PME) from black carrot. The enzyme showed very high activity in a broad pH range of 6.5–8.5, with the optimum pH occurring at 7.5. The optimum temperature for maximal PME activity was found to be 55 °C. NaCl enhanced PME activity, particularly at 0.2 M. K_m and V_max values for black carrot PME using apple pectin as substrate were found to be 2.14 mg/ml (r² = 0.988) and 3.75 units/ml, respectively. The enzyme was stable between the temperatures of 30–50 °C/5 min whereas it lost nearly all of its activity at 70 °C/5 min. E_a and Z values were found to be 196.8 kJmol⁻¹ (r² = 0.996) and 2.16 °C (r² = 0.995), respectively.     

Influence of technical processing units on polyphenols and antioxidant capacity of carrot (Daucus carrot L.) juice

The effect of three processing units (blanching, enzyme liquefaction, and pasteurisation) on polyphenols and antioxidant activity of carrot juices was investigated. Polyphenols and antioxidant activity of carrot juices varied with different processes. Five polyphenolic acids were identified in fresh carrot juice, and the predominant compound was chlorogenic acid. Compared with fresh carrot juice, blanching and enzyme liquefaction could result in the increase of the total polyphenol content (TPC) and the antioxidant activity in scavenging DPPH free radicals (DPPH) and Fe²⁺-chelating capacity (FC), whereas pasteurisation could result in the decrease of the TPC and the antioxidant activity in DPPH and FC. Meanwhile blanching, enzyme liquefaction, and pasteurisation showed little influence on the antioxidant activity in lipid peroxidation protection. The antioxidant activities in DPPH and FC increased with increasing concentration while no correlation between lipid peroxidation protection and polyphenols concentration. Polyphenols still retained high antioxidant activity after the processes, which have potential health benefits for consumers.     

Effects of temperature,solid content and pH on the stability of black carrot anthocyanins

Anthocyanin stability of black carrots was studied at various solid contents (11, 30, 45 and 64° Brix) and pHs (4.3 and 6.0) during both heating, at 70–90 °C, and storage at 4–37 °C. Monomeric anthocyanin degradation fitted a first-order reaction model. Degradation of monomeric anthocyanins increased with increasing solid content during heating, while it decreased during storage. For example, at pH 4.3, half-life periods for anthocyanins at 30, 45 and 64° Brix were, respectively, 8.4, 6.9 and 5.2 h during heating at 80 °C and 18.7, 30.8 and 35.9 weeks during storage at 20 °C. At 30–64° Brix, increasing pH from 4.3 to 6.0 enhanced the degradation of anthocyanins during heating. The effect of pH on thermal stability of anthocyanins was also studied at six different pHs (2.5–7.0) in citrate-phosphate buffer solutions and significant decrease in anthocyanin stability was observed at pHs above 5.0. Higher activation energies (E_a) were obtained during heating than during storage with increasing solid contents. At 30–64° Brix, E_a values ranged from 68.8 to 95.1 kJ mol⁻¹ during heating and from 62.1 to 86.2 kJ mol⁻¹ during storage. Q₁₀ values at 20–37 °C were as high as 3.1 at 45° Brix and 3.6 at 64° Brix.     

Kinetics of anthocyanin degradation and polymeric colour formation in black carrot juice concentrates during storage

The changes in anthocyanins (ACNs) and polymeric colour of black carrot juice concentrate (BCJC) samples were monitored during storage at ?23, 5 and 20 °C for 319 days and at 30 °C for 53 days. While ACN degradation was fitted to a first‐order reaction model, polymeric colour formation was fitted to a zero‐order reaction model during the storage. Half‐life periods for ACN degradation in BCJCs were 603, 137 and 29 days at 5, 20 and 30 °C, respectively. The reaction rate constants for polymeric colour formation were 0.0207, 0.1435 and 0.5581%/days at 5, 20 and 30 °C, respectively. HPLC‐MS analyses of BCJC showed that cyanidin‐3‐galactoside‐xyloside‐glucoside‐ferulic acid (56%) was the major ACN, followed by cyanidin‐3‐galactoside‐xyloside (19%) and cyanidin‐3‐galactoside‐xyloside‐glucoside‐sinapic acid (10%). Cyanidin‐3‐galactoside‐xyloside‐glucoside‐ferulic acid was the most stable ACN in BCJC at storage temperatures. BCJCs should be kept at sub‐freezing temperatures to minimise ACN degradation.     

Anthocyanin and colour changes during processing of pomegranate (Punica granatum L., cv. Hicaznar) juice from sacs and whole fruit

The effects of clarification and pasteurisation on anthocyanins (ACNs) and the colour of pomegranate juice (PJ) produced from sacs and whole fruits were investigated. Clarification caused a loss of 4% of ACNs in juice from sacs (JFS) and a loss of 19% in juice from whole fruit (JFWF). After pasteurisation, there was an 8–14% and 13–9% loss of ACNs from unclarified and clarified JFS and JFWF samples, respectively. Polymeric colour was very high even in unclarified samples (25–29%). Compared to JFS, higher polymeric colour was formed in JFWF. HPLC analyses of PJ revealed that cyanidin-3,5-diglucoside was the major ACN, followed by cyanidin-3-glucoside and delphinidin-3-glucoside. Cyanidin-3,5-diglucoside showed higher stability to clarification and pasteurisation than cyanidin-3-glucoside in both PJ samples. Cold clarification with only gelatin is recommended for PJ. To prevent excessive ACN loss and the formation of brown colouring, PJ should be subjected to minimal heating.     

Thermal characterization of the anthocyanins from black soybean (Glycine max L.) exposed to thermogravimetry

One anthocyanin compound, cyanin-3-glucoside, was isolated and identified by high performance liquid chromatography tandem mass spectrometry (HPLC_MS/MS) from seed coat of black soybean variety, Heizi to assess its thermal characterization in vitro. The thermal characterization of anthocyanin was studied by thermogravimetry (TG) analysis. The results from the TG curves showed the decomposition of anthocyanin occurred in three stages. Glucose cleaved from the cyanin-3-glucoside occurred in the first stage. Degradation of cyanin and small amounts of cyanin-3-glucoside appeared mainly in the second stage. The sugar in the anthocyanin was decomposed in the third stage. Thermodynamic analysis was applied by free dynamic model. TG-isothermal experiments for the anthocyanins from black soybean seed coats confirmed the correct of the thermodynamic analysis.     

Determination of falcarinol in carrot (Daucus carota L.) genotypes using liquid chromatography/mass spectrometry

A new analytical method for the determination of falcarinol [(Z)-heptadeca-1,9-diene-4,6-diyn-3-ol] in carrot root samples has been developed and validated. The method consists of accelerated solvent extraction (ASE) of lyophilised carrot root samples with ethyl acetate and LC–MS analysis of the extracts. Falcarinol was determined by extracting the main ion species generated in the ESI positive mode, m/z 268 [M+H–H₂O+MeCN]⁺, from the full MS chromatogram. Quantitation was performed using a falcarinol calibration curve (correlation coefficient 0.9975) as an external standard and pelargonic acid vanillylamide as an internal standard. The method showed good precision with interday and intraday variation of less than 4% and high recovery (average recovery rate 97.9%). LOD (S/N = 3) and LOQ (S/N = 10) were 2.5 and 7 ng, respectively. Using this method, 27 different carrot genotypes grown and harvested under the same conditions were analyzed, and falcarinol contents ranging from 0.70 to 4.06 mg/100 g fresh weight were determined.     

The effect of pre-treatment on the anthocyanin and flavonol content of black currant juice (Ribes nigrum L.) in concentration by reverse osmosis

Reverse osmosis process for the concentration of black currant juice was carried using AFC-99 tubular membrane at 30 °C and 45 bar. The contents of selected flavonols and anthocyanins were analyzed after centrifugation; enzyme treatment by Panzym Super E and by Rohapect berry followed by centrifugation; and ultrafiltration black currant juices and juice concentrates. The total soluble solid (TSS) content of the juices increased from the initial 17.6–17.9 °Brix to 24–24.8 °Brix in the case of the centrifuged juice in the concentration process. Similarly, it increased from 14.5–15.5 °Brix to 23.1–23.4 °Brix for the Panzym Super E treated juice, and from 16.1–16.9 °Brix to 22.5–23.1 °Brix for the Rohapect berry treated black currant juices. The ultrafiltered juice had the lowest initial TSS content between 14.1 and 14.9 °Brix and it increased to 22.1–23.1 °Brix. The average permeate fluxes during the concentration process were 7.3 L m⁻² h⁻¹ for the centrifuged juice, 11.9 L m⁻² h⁻¹ for the Panzym Super E treated juice, 9.2 and 13.1 L m⁻² h⁻¹ for the Rohapect berry treated and ultrafiltered juice, respectively. Analysis indicated that the enzymatic treatment resulted in the increase of anthocyanin and flavonol content of the juices. The centrifugation process decreased the amount of anthocyanins and flavonols to some extent. The juice clarified by ultrafiltration had significantly lower concentrations of anthocyanins and flavonols, while the juices treated by Panzym Super E had the highest levels of these flavonoids. This study recommends enzymatic pre-treatment by Panzym Super E, since it improves the permeate flux in reverse osmosis during the concentration process, and results in a juice concentrates highest in anthocyanins and flavonols.     

Thermal degradation kinetics of anthocyanins and visual colour of Urmu mulberry (Morus nigra L.)

Urmu mulberry (Morus nigra L.) juice was concentrated from 15.02 to 45.20 °Brix by rotary vacuum evaporator at 40 °C. The objectives of this study were to determine the titratable acidity, soluble solid content, antioxidant capacity, total monomeric anthocyanins and total phenolic matter in prepared concentrate, to investigate the thermal degradation kinetics of anthocyanins and Hunter colour parameters (L^∗, a^∗, b^∗) and total colour difference (TCD^∗) and to develop a relationship between visual colour and anthocyanin during thermal processing at 60, 70 and 80 °C. Monomeric anthocyanin degradation showed a first order reaction kinetics. The zero order, first order and a combined kinetics model were applied to the changes in Hunter colour parameters (L^∗, a^∗ and b^∗) and total colour difference (TCD^∗). All colour parameters followed an apparent combined kinetics model. The degradation of anthocyanins showed positive correlation with a^∗, b^∗ and L^∗ and negative correlation with TCD^∗.     

Antioxidant capacity and anthocyanin profile of sour cherry (Prunus cerasus L.) juice

The antioxidant capacities, total polyphenolic content and monomeric anthocyanin content of eleven types of sour cherry juice obtained from different varieties of sour cherries were investigated. Antioxidant capacity, total polyphenolic content and monomeric anthocyanin contents of the juices were within the ranges 20.0–37.9 mmol/L, 1510–2550 and 350.0–633.5 mg/L, respectively. The main anthocyanin compound in sour cherry juice was cyanidin-3-glucosylrutinoside at concentrations between 140.3 and 320.9 mg/L. Cyanidin-3-glucosylrutinoside was followed by cyanidin-3-rutinoside within a concentration range of 25.5–85.5 mg/L. Cyanidin-3-sophoroside and cyanidin-3-glucoside contents were relatively low (2.6–21.5 and 2.0–9.9 mg/L). Anthocyanin capacity and total polyphenol content were fairly well correlated (r = 0.742, p < 0.01), whereas the correlation between antioxidant capacity and monomeric anthocyanin content was insignificant (r = 0.423, p > 0.05). The correlation between antioxidant capacity – cya-3-glucosylrutinoside (r = 0.606, p < 0.01) and antioxidant capacity – cya-3-rutinoside (r = 0.628, p < 0.01) was significant.     

The effects of six phenolic acids and tannic acid on colour stability and the anthocyanin content of mulberry juice during refrigerated storage

Six phenolic acids and tannic acid are added to fresh mulberry juice to enhance the colour. Effects of these copigments on colour stability and the anthocyanin content of mulberry juice are investigated while being stored at 4 °C for 30 days. Results suggest that the addition of the copigments markedly increases the maximum absorbance of mulberry juice. Cyanidin-3-glucoside is the major anthocyanin, followed by cyanidin-3-rutinoside. Furthermore, the retention rate of the total anthocyanin, cyanidin-3-rutinoside and cyanidin-3-rutinoside increases after the addition of all copigments. The effect of ferulic acid on the stability of total anthocyanin, cyanidin-3-glucoside and cyanidin-3-rutinoside in mulberry juice is the best, 89.52%, 86.90% and 94.46% respectively (66.56%, 62.58% and 73.60% in the control group). Researchers recommend the addition of ferulic acid, p-coumaric acid and caffeic acid – all of which belong to the hydroxycinnamic acid group, to the mulberry juice to enhance the colour stability and anthocyanin content.     

Investigation of bitterness in carrots (Daucus carota L.) based on quantitative chemical and sensory analyses

Bitterness is considered as an undesirable taste of carrots. Quantitative chemical analysis of potential bitter compounds of different carrot genotypes was combined with sensory analysis in order to identify key compounds likely to be responsible for the bitterness of carrots. Eight carrot genotypes (‘Bolero’, ‘Mello Yello’, ‘Nairobi’, ‘Tornado’, ‘Purple Haze’, ‘Line 1’, ‘Line 2’, and ‘Line 3’) representing extremes in sensory-perceived odour, flavour, and taste. Potential bitter compounds like polyacetylenes, isocoumarins and phenolic acids were quantified in the peel and the corresponding peeled carrot, and their contribution to bitterness in raw carrots was analysed by sensory profiling using multivariate data analysis. Falcarindiol and a di-caffeic acid derivative were highly related to bitterness in contrast to falcarinol and other potential bitter compounds. Falcarindiol and the di-caffeic acid derivative were primarily present in the peel whereas falcarinol was almost evenly distributed in the root. Investigation of bitterness revealed that high sugar content to some extent could mask the bitter perception of carrots. As falcarinol is the most bioactive of the carrot polyacetylenes the results of the present study indicate that there is a basis for improving the health effects of raw carrots without affecting sensory quality.     

Effect of pectinolytic juice production on the extractability and fate of bilberry and black currant anthocyanins

Bilberries (Vaccinium myrtillus L.) and black currants (Ribes nigrum L.), dark blue berries rich in anthocyanins, were processed with an aid of commercial pectinolytic enzyme preparations, and the effect of processing on berry anthocyanins was investigated. The enzyme preparations were dosed based on their polygalacturonase activity from 1 to 100 nkat/g of berry mash. The juice yields were determined by weighing, and anthocyanin analyses were performed with HPLC. The bilberry and black currant juice yields increased significantly in enzyme-aided treatments with comparison to control, even with the lowest (1 nkat/g) polygalacturonase dosage. The anthocyanin yield increased by up to 83% for bilberries and up to 58% for black currants in enzyme-aided treatments as compared to control. The results showed that higher polygalacturonase dosage was needed for black currant to achieve the maximal juice and anthocyanin yields than for bilberries. The stability and the profile of extracted anthocyanins were greatly affected by the glycosidase side activities present in the enzyme preparations, which were able to hydrolyze certain anthocyanins to the corresponding aglycones. In addition, the data indicate that anthocyanidin rutinosides were more easily extracted than those of glucosides, which prevailed over the arabinosides and galactosides. Thus, prior to processing it is important to know the intact anthocyanin structures of the raw material, and the activity profile of the enzyme preparation to obtain optimal anthocyanin extractability and enzyme dosage.     

Yield and quality effects of electroplasmolysis and microwave applications on carrot juice production and storage

Electroplasmolysis as a pretreatment and microwave heating as an alternative to traditional heating were used in carrot juice production and the effects of these electrical methods on juice quality were investigated. Electroplasmolysis and microwave applications were optimized by response surface methodology. Optimum conditions were these: voltage gradient of 22.2 V/cm and treatment time of 60 s for electroplasmolysis, and flow rate of 90 mL/min with power of 900 W for microwave heating. Production of carrot juice was carried out by using these optimum conditions. After production, carrot juice samples were stored for 4 mo at +4 °C and analyses were performed at monthly intervals. As a result of electroplasmolysis, a 9.7% increase in juice yield was obtained. In addition, 100% pectin methylesterase inactivation was found with the microwave heating application. The results showed that the highest values for quality characteristics, such as antioxidant capacity and total pectin, total phenolic, and total carotenoid contents, were obtained with the combined applications of the electrical methods. In addition, these quality characteristics were protected better in the group of combined applications of the electrical methods (electroplasmolysis + microwave) during storage.     

Characterisation of anthocyanins in the black soybean (Glycine max L.) by HPLC-DAD-ESI/MS analysis

The aim of this study was to isolate and identify the anthocyanins in the black seed coated soybean (cv. Cheongja 3, Glycine max (L.) Merr.) using reverse phase C-18 open column chromatography and high-performance liquid chromatography (HPLC) with diode array detection and electro spray ionization/mass spectrometry (DAD-ESI/MS) analysis, respectively. Anthocyanins were extracted from the coat of black soybeans with 1% TFA in methanol, isolated by RP-C-18 column chromatography, and their structures elucidated by 1D and 2D NMR spectroscopy. The isolated anthocyanins were characterised as delphinidin-3-O-glucoside (3), cyanidin-3-O-glucoside (5), petunidin-3-O-glucoside (6), pelargonidin-3-O-glucoside (7) and cyanidin (9). Furthermore, four minor anthocyanins were detected and identified as catechin-cyanidin-3-O-glucoside (1), delphinidin-3-O-galactoside (2), cyanidin-3-O-galactoside (4), and peonidin-3-O-glucoside (8) based on the fragmentation patterns of HPLC-DAD-ESI/MS analysis.     

Effect of carrot (Daucus carota) antifreeze proteins on texture properties of frozen dough and volatile compounds of crumb

The effects of concentrated carrot protein (CCP) containing 15.4% (w/w) carrot (Daucus carota) antifreeze protein on texture properties of frozen dough and volatile compounds of crumb were studied. The sensory quality and texture profile analysis results of bread with CCP supplementation were similar to those of the control. Meanwhile, CCP supplementation brought some beneficial effects in holding the loaf volume. Results of texture property analysis showed that the hardness of dough with CCP supplementation was softer and steadier than that of the control during frozen storage, mainly due to the lower freezable water content. Furthermore, solid phase micro-extraction (SPME)-GC-MS analysis showed CCP supplementation did not give negative influence on volatile compounds of crumb and brought a pleasant aroma felt like Michelia alba DC by trans-caryophyllene simultaneously. In conclusion, CCP could be used as a beneficial additive to frozen dough.     

Anthocyanins and fruit colour in plums (Prunus domestica L.) during ripening

The accumulation of anthocyanins and the evolution of fruit colour were investigated during ripening of Prunus domestica L. Using HPLC, the fruit of the ‘Jojo’, ‘Valor’, ‘?a?anska rodna’ and ‘?a?anska najbolja’ cultivars were quantified for anthocyanins during a 25-day period of ripening (a 33-day period in the case of ‘Jojo’). The major anthocyanin was cyanidin 3-rutinoside which, in ripe fruits, ranged from 4.1 to 23.4 mg/100 g FW (from 52.6% to 73.0%). It was followed by peonidin 3-rutinoside (from 6.5% to 37.9%), cyanidin 3-glucoside (from 1.8% to 18.4%), cyanidin 3-xyloside (from 4.7% to 7.8%) and peonidin 3-glucoside (from 0.0% to 0.4%). The ripening process resulted in a concentration increase of total anthocyanins and changed the ratios amongst the anthocyanins. The colour parameters, L^∗, a^∗, b^∗, chroma and hue angle, of partially ripe plums were higher than those in the ripe fruit, but the CIRG index of partially ripe fruit was always lower than that of ripe fruit. The total anthocyanins were weakly correlated with each of the colour parameters; their relationships varied between cultivars and ripening stage. Correlation coefficients between individual anthocyanins and colour parameters in ripe plums were cultivar-dependent.     

Changes of anthocyanins and hydroxycinnamic acids affecting the skin colour during maturation of sweet cherries (Prunus avium L.)

The content and relative amounts of anthocyanins and hydroxycinnamic acids (HCA) were determined in local sweet cherries (cultivar Petrovka) at 7 stages of maturity, by means of high performance liquid chromatography (HPLC), and compared to instrumentally assessed skin colour of the same sweet cherries. Skin colour of harvested samples was measured using the CIE L^*,a^*,b^* system. The contents of neochlorogenic and 3′-p-coumarylquinnic acids decreased with no significant change in ratio during ripening, except for the first 4 days of maturation, when the ratio changed due to increased content of neochlorogenic acid. The linear increase of total anthocyanins during maturation was observed without the trend of stabilization in the final stages of maturity. The colour change of Petrovka during maturation was influenced by the increase of total anthocyanins, consisting mostly of cyanidin-3-rutinoside and cyanidin-3-glucoside (97-98% of the total). The chroma and L^* values appeared to be optimal indicators of anthocyanin accumulation during maturation, and better than the a^* value and hue angle. The accumulation of anthocyanins from 507.1 to 1150.9 mg of cyanidin-3-rutinoside/kg of fresh weight (FW) during the second half of maturation caused the formation of a new colour cast of Petrovka, which influenced the decrease of redness and colour intensity, as recognized by CIE L^*,a^*,b^* colour space.     

Rheological characteristics of tamarind (Tamarindus indica L.) juice concentrates

The steady-shear and small-amplitude oscillatory rheological properties of tamarind (Tamarindus indica L.) juice concentrate (TJC) were studied in the temperature range of 10-90 °C using a controlled-stress rheometer. Under steady-shear deformation tests, shear stress-shear rate data were adequately fitted to the Herschel-Bulkley and Casson model at lower (10-30 °C) and higher (50−90 °C) temperature range, respectively. The Carreau model was applied to describe the shear-thinning behaviour of the concentrate, and the model parameters estimated empirically showed temperature dependence. Oscillatory shear data of TJC revealed predominating viscous behaviour (G″>G′) at lower frequency range while the elastic modulus predominating over the viscous one (G′>G″) at higher frequency range. The Cox-Merz rule that relates steady shear and dynamic material functions was tested and not followed by most of the temperatures. The specific heat of TJC increased with temperature and the glass transition temperature of the product was found to be −70.74 °C.     

Processing and storage effects on monomeric anthocyanins, percent polymeric color, and antioxidant capacity of processed blueberry products

ABSTRACT:  This study evaluated the effects of processing and 6 mo of storage on total monomeric anthocyanins, percent polymeric color, and antioxidant capacity of blueberries that were canned in syrup (CS), canned in water (CW), pureed, and juiced (clarified and nonclarified). Total monomeric anthocyanins, percent polymeric color, and oxygen radical absorbing capacity (ORAC) assay using fluorescein (ORAC_FL) were determined postprocessing after 1 d, and 1, 3, and 6 mo of storage. Thermal processing resulted in marked losses in total anthocyanins (28% to 59%) and ORAC_FL values (43% to 71%) in all products, with the greatest losses occurring in clarified juices and the least in nonclarified juices. Storage at 25 °C for 6 mo resulted in dramatic losses in total anthocyanins, ranging from 62% in berries CW to 85% in clarified juices. This coincided with marked increases in percent polymeric color values of these products over the 6-mo storage. The ORAC_FL values showed little change during storage, indicating that the formation of polymers compensated for the loss of antioxidant capacity due to anthocyanin degradation. Methods are needed to retain anthocyanins in thermally processed blueberries.