Flavonols, betacyanins content and antioxidant activity of cactus Opuntia macrorhiza fruits

Flavonols, betacyanins content and antioxidant activity of red-purple cactus Opuntia macrorhiza fruits, a promising cactus pear species, were evaluated in comparison to the well known cactus pear fruits of Opuntia ficus-indica. Flavonol profile was evaluated by HPLC-DAD prior to and after enzymatic hydrolysis (glycosides vs. aglycons). In addition betacyanins, responsible for the purple to red color of cactus pear fruits were also estimated and compared to Beta vulgaris ssp. (roots) and red O. ficus-indica fruits. In all cases, cactus fruit pulps showed no flavonols at all. While different derivatives of isorhamnetin glycosides were found in O. ficus-indica fruit's peel, isorhamnetin-3-O-rutinoside was the only compound in O. macrorhiza fruit. Correspondingly, antioxidant activity assays showed a high antioxidant activity of both, O. macrorhiza fruit's peel and pulp. With regard to betacyanins, O. macrorhiza fruit's peel and pulp provide a deep red-purple color, whose average impact is higher compared to red beet (B. vulgaris spp.) and about 8-fold higher than red fruits from O. ficus-indica. Supporting these results, estimation of color attributes (L*, a*, b*, C and H°) showed also a high color impact of both O. macrorhiza fruit's peel and pulp.     

Inhibitory activity of aromadendrin from prickly pear (<Emphasis Type="Italic">Opuntia ficus-indica</Emphasis>) root on aldose reductase and the formation of advanced glycation end products

Prickly pear (Opuntia ficus-indica) is a longdomesticated crop plant of arid and semiarid parts of the world. The efficacy of extracts of prickly pear root for managing diabetes and diabetes complications was evaluated using a variety of in vitro bioassays. The ethyl acetate-soluble fraction was most effective in the prevention of diabetes and its complications via the inhibition of rat lens aldose reductase activity, the formation of advanced glycation end products, and α-glucosidase activity. MS and NMR were used to identify the bioactive compound from the ethyl acetate-soluble fraction as 3,5,7,4′-tetrahydroxyflavanone (aromadendrin).     

Effects of UVB Light,Wounding Stress,and Storage Time on the Accumulation of Betalains,Phenolic Compounds,and Ascorbic Acid in Red Prickly Pear (<Emphasis Type="Italic">Opuntia ficus-indica</Emphasis> cv. Rojo Vigor)

Prickly pear (Opuntia ficus-indica cv. Rojo Vigor) fruit is an excellent source of secondary metabolites with health-promoting properties (i.e., betalains, flavonoids, and ascorbic acid), and thus, it is relevant to find postharvest treatments that increase their concentration. Postharvest abiotic stresses such as wounding and ultraviolet radiation can induce the accumulation of secondary metabolites in different horticultural crops. In the present study, the effect of ultraviolet B (UVB) radiation applied alone or combined with wounding stress on the accumulation of betalains, phenolics, and ascorbic acid in red prickly pear was evaluated. Whole and wounded fruit samples were treated with UVB radiation (6.4 W m^?2) for 0, 15, 90, and 180 min and stored for 24 h at 16 °C. The content of bioactive compounds was evaluated before and after storage. The application of UVB radiation for 15 min was the most adequate treatment to induce the accumulation of bioactive compounds. In this context, UVB radiation (15 min) of the wounded tissue resulted on an immediate accumulation of betalains (33–40%) and ascorbic acid (54–58%) in the pulp and peel of the fruit. Likewise, after storage, the pulp of irradiated whole fruits showed the highest accumulation of phenolics (125.8%) and betalains (49.8%) as compared with the control, whereas the stored wounded tissue treated with UVB presented accumulation of ascorbic acid in the pulp (67.2%) and peel (84.6%). The stressed tissue with enhanced concentration of nutraceuticals could be transformed into functional processed foods or used as raw material for the extraction of compounds with applications in health-related markets.     

Dielectric Properties of Cloudy Apple Juices Relevant to Microwave Pasteurization

Continuous flow microwave heating is an emerging technology that brings advantages to the pasteurization of food products such as fruit juices. In order to correctly design the microwave cavity and applicator tube, knowing the dielectric properties of the product is important. The relative electrical permittivity describes the capacity to store electrical energy, while the dielectric loss factor describes the ability to dissipate energy as heat. The penetration depth of microwaves depends on these properties and on the field frequency. In this work, the dielectric properties and electrical conductivity of cloudy apple juices, obtained from different varieties of apples (Gala, Fuji, Granny Smith, and Red Delicious) and from an industrial plant (Gala), were determined from 500 to 3000 MHz and temperatures between 10 and 90 °C. Penetration depth was also calculated, and all results were correlated with temperature for commercial frequencies of 915 and 2450 MHz. At these frequencies, apple variety showed little influence and the permittivity decreased almost linearly with temperature. The loss factor curves showed a minimum around 40 °C at 915 MHz and were slightly smaller for juices with lower conductivity. At 2450 MHz, the loss factor varied between 7 and 18 with a negative temperature effect, which indicates that thermal runaway should not be a problem. The penetration depth ranged from 33 to 58 mm at 915 MHz and from 9 to 23 mm at 2450 MHz, depending on temperature and variety, which is useful information for the design of applicator tubes.     

Dielectric Properties of Sweet Potato Purees at 915 MHz as Affected by Temperature and Chemical Composition∗

A process for rapid sterilization and aseptic packaging of sweet potato puree using a continuous flow microwave system operating at 915 MHz has been successfully developed. In microwave processing, dielectric properties have a major role in determining the interaction between purees and the electromagnetic energy. The objective of this research was to determine how dielectric properties are affected by temperature and chemical composition of purees derived from thirteen sweet potato cultivars with varying flesh colors. Results indicated that temperature, moisture, sugar and starch content had a pronounced effect (p < 0.001) on dielectric properties measured from 15°C to 145°C at 915 MHz. Dielectric constant decreased with increasing temperature, while dielectric loss factor increased quadratically. Power penetration depth of all cultivars decreased with increasing temperature. Predictive equations were developed for dielectric constant (R²?=?0.82) and dielectric loss factor (R²?=?0.90) as a function of temperature, moisture, sugar, and starch. The predictive equations would be useful in determining the dielectric properties of sweet potato purees for the microwave processing technology.     

Chemical characterization of Opuntia dillenii and Opuntia ficus indica fruits

The chemical compositions (moisture, °Brix, total fibre, protein, fat, ash, pH, acidity, ascorbic acid, total phenolics, Na, K, Ca, Mg, Fe, Cu, Zn, Mn, Ni and Cr) were determined in fruits belonging to two species of prickly pear, Opuntia ficus indica and Opuntia dillenii, from Tenerife Island. The chemical compositions of the two species were clearly different. However, no important differences were observed between orange and green prickly pears within the specie O. ficus indica. An important contribution to the intakes of fibre, ascorbic acid, Mn, Cr and total phenolics is provided by the consumption of prickly pears, particularly from fruits of O. dillenii. Applying factor and/or discriminant analysis, the prickly pear samples were differentiated according to the species, altitude and region of cultivation in the island.     

Fatty acid composition and rheological behaviour of prickly pear seed oils

Prickly pear fruits constituted valuable foodstuff for humans and animals in arid and semi-arid regions. Two species of prickly pear from Tunisia, Opuntia ficus indica and Opuntia stricta, were investigated for fatty acid composition and physicochemical parameters of the seed oil. No significant difference in either physical or chemical parameters was found between the species. The main fatty acids of prickly pear seed oil were C16:0, C18:0, C18:1, C18:2. With an exceptional level of linoleic acid, up to 70%, the content of unsaturated fatty acids was high, at 88.5% and 88.0% for O. ficus indica and O. stricta, respectively.Rheological properties were analysed with changes of temperature and shear stress. Variations of viscosity were measured and the viscoelastic parameters were determined during heating and cooling cycles between 20 and 70 °C. Curves of flow were established with up and down cycles of shear stress at different temperatures. These measures highlighted the presence of large aggregates of crystal fatty acids in both Opuntia crude oils. Shearing and temperature destroyed this structural state and gave birth to an homogeneous stable suspension.The structural state of crude oil was confirmed using a contrast phase microscope, and the particle size distribution was obtained by laser granulometry.     

Effect of pH and temperature on the thermostability of prickly pear (Opuntia ficus‐indica) yellow‐orange pigments

The colour stability of the yellow‐orange pigment (λ_max = 476 nm) of prickly pear (Opuntia ficus‐indica) fruit was determined as a function of temperature and pH. The experiments were carried out at three different temperatures (50, 70 and 90°C) with pigment solutions at pH values ranging from 2–7. The degree of pigment retention decreased with increasing temperature as a function of increasing thermal exposure time with least pigment degradation at pH 5. The reaction rate constants were determined as 0.0062, 0.0383 and 0.1102 min^–1 for a thermal degradation reaction rate of pseudo‐first order. The activation energy was calculated as 65.1 kJ·mol^–1.     

Health-promoting substances and antioxidant properties of Opuntia sp. fruits. Changes in bioactive-compound contents during ripening process

Several Opuntia cactus fruits of different pulp colours from Argentina were studied at their physiological mature states. Analyses of these fruits showed very variable total soluble solid values and ascorbic acid contents ranging from 0.26 to 0.48 mg/g. Total phenolic compounds contents were between 0.54 and 1.2 mg of gallic acid/g, respectively. Purple Opuntia spp., dark purple Opuntia ficus-indica and orange Opuntia megacantha presented the highest levels amongst the samples studied. The antioxidant activity of Opuntia fruits was very variable and presented vitamin C equivalent values (VCEAC) between 0.25 and 0.57 mg/g. Purple Opuntia ficus-indica showed the highest antiradical ability. Besides, the antioxidant activity, ascorbic acid and phenolic compound contents in yellow and orange Opuntia megacantha fruits were monitored in different stages during their ripening process. Concentration changes of betalains and chlorophylls comparing skin and pulp and other physicochemical parameters were also measured in these fruits.     

Effect of Solids Concentration on the Physicochemical and Flow Properties of Cactus Pear Juices of Two Varieties (<Emphasis Type="Italic">Opuntia ficus-indica</Emphasis> and <Emphasis Type="Italic">Opuntia streptacantha</Emphasis>)

Juices from two varieties of cactus pear, a green (Opuntia ficus-indica) and a red (Opuntia streptacantha), were obtained and concentrated by evaporation. Both fruit varieties and their juices at different concentrations were characterized. Green cactus pears had significantly higher amount of pulp than red cactus pears; the peel of O. ficus-indica represented only 38 versus 52 % of the fruit for the O. streptacantha. Both varieties had no significant differences on moisture, density, pH, and titratable acidity, in contrary to soluble solids. Juice was concentrated under vacuum conditions to reach a final concentration of 42, 53–55, and 58–60 °Brix, respectively, and stored under refrigeration (10 °C) during 4 weeks. Physicochemical properties of the pears and juices were determined as fresh items (time zero) and every week for the concentrate juices through storage; similarly, flow parameters were measured at 10 and 25 °C. Concentrate density (1160–1283 kg/m³) was mainly affected by final soluble solids, while pH and acidity were affected differently depending on the variety. Concentrated juices at 42 °Brix were considered with Newtonian behavior with a viscosity of 2–22 mPa s, while those at higher concentrations were of pseudoplastic nature (n < 1.0 and K > 69 mPa sⁿ). Power Law model fitted better the flow behavior than Herschel-Bulkley model of concentrates of both varieties. Temperature, solid concentration, and/or storage time affected the consistency coefficient (K) and flow index (n) depending on the cactus pear variety. Overall, those concentrated juices from O. streptacantha were more stable and exhibited lower apparent viscosity.     

Chemical and biochemical changes in prickly pears with different ripening behaviour

Chemical and biochemical changes were studied in ripening prickly pears from three Opuntia morphospecies with different ripening behaviour: Naranjona (O. ficus-indica), Blanca Cristalina (Opuntia sp.), and Charola (O. streptacantha), of early, intermediate, and late ripening, respectively. At fullyripe stage (commercial maturity), Blanca Cristalina showed the biggest fruits, the hardest texture, and its pulp had the highest protein content. There were no significant differences among morphospecies in pH or total soluble solids in fully ripe fruits. The three species exhibited considerable levels of vitamin C, dietary fibre, and minerals such as calcium, iron, and zinc. Protein expression was analysed in pulp and skin from every species at physiological and commercial maturity. Some proteins appeared at both stages, while many others expressed differentially. This study evaluated prickly pear components important for human nutrition and health, and provided basic information on pricky pear ripening, with a view to its control and to improving shelf life.     

Development of a process for the production of a betalain-based colouring foodstuff from cactus pear

Since no process has yet been established for the production of cactus pear juice, the present work aimed at the development of a betalain-based colouring foodstuff from Opuntia ficus-indica cv. ‘Gialla’ and cv. ‘Rossa’ of two seasons applying unit operations typical for fruit juice production. Complete separation of the peels from the pulp and removal of seeds were achieved by carborundum peeling of the frozen fruits and subsequent passing through a finisher. Furthermore, for improved filtration of cactus pear juice different enzyme preparations were tested to degrade pectic-like substances. To monitor quality changes in the course of processing, juice samples were analysed after each processing step in terms of colour and selected chemical parameters. While lightness (L*) and chroma (C*) increased during processing for both cultivars, hue angle (h°) remained unchanged for the yellow cultivar ‘Gialla’, but a slight shift towards red was observed for the red cultivar ‘Rossa’ after pasteurisation. Unexpectedly, even after repeated thermal treatment neither non-enzymatic browning nor HMF formation was observed in juices from both cultivars.Industrial relevanceCactus pear represents a viable alternative to red beet for food colouring purposes: it neither exhibits negative sensorial impact nor high nitrate levels, but offers a broad colour range. However, no attempt has yet been made to benefit from this potential. The process developed is considered suitable for being scaled up to industrial-scale production thus opening an avenue for large-scale cactus pear fruit processing.     

Temperature-Dependent Dielectric Properties of Raw Cow’s and Goat’s Milk from 10 to 4,500 MHz Relevant to Radio-frequency and Microwave Pasteurization Process

To offer useful information for milk pasteurization with radio-frequency or microwave heating, the dielectric properties (dielectric constant and dielectric loss factor) of raw cow’s milk and goat’s milk were determined over the frequency range of 10–4,500 MHz and temperature range of 25–75 °C by a vector network analyzer and an open-ended coaxial-line probe. The mathematical models describing the relationship between permittivities and temperature were built, and the power penetration depth was investigated. The results showed that both for cow’s milk and goat’s milk, the dielectric constants decreased with an increase of frequency, and the dielectric loss factor decreased with increasing frequency below 1,000 MHz and increased after that. The dielectric constants decreased with increasing temperature at a given frequency. For raw cow’s milk, the dielectric loss factor almost increased with temperature below about 800 MHz, and decreased with temperature above that. For raw goat’s milk, the loss factor decreased with temperature in whole investigated frequency range. Quadratic equations could be used to describe the relationship between permittivities and temperature at interested frequencies with coefficient of determination higher than 0.96. The penetration depth decreased with increasing frequency. Contrasted to frequency, temperature had less effect on penetration depth. Microwave heating at 915 MHz has great potential for raw cow’s milk pasteurization, while radio-frequency heating at 27.12 and 40.68 MHz and microwave heating at 915 MHz can be used for goat’s milk pasteurization.     

Feasibility of aseptic processing of a low-acid multiphase food product (salsa con queso) using a continuous flow microwave system

ABSTRACT:  Aseptic processing of a low-acid multiphase food product using a continuous flow microwave heating system can combine the advantages of an aseptic process along with those of microwave heating. Dielectric properties of 2 different brands of 1 such product ( salsa con queso ) were measured under continuous flow conditions at a temperature range of 20 to 130 °C. At 915 MHz, the dielectric constant ranged from 58.7 at 20 °C to 41.3 at 130 °C with dielectric loss factor ranging from 41.0 at 20°C to 145.5 at 130 °C. The loss tangent at 915 MHz ranged from 0.61 at 20 °C to 3.52 at 130 °C. The temperature profiles at the outlet during processing of salsa con queso in a 5-kW microwave unit showed a narrow temperature distribution between the center and the wall of the tube. The study showed the feasibility of aseptic processing of salsa con queso using a continuous flow microwave system.     

Effect of macerate enzymes on the yield,quality, volatile compounds and rheological property of prickly pear juice

Pectinase and cellulase enzymes were used to investigate efficacy for improving juice yield, stability and quality from prickly pear fruit. Pectinase improved the yield, stable color, color‐assayed as release of anthocyanins or carotinoids and clarity of the juice. A significant increase in the effectiveness of pectinase was observed as the concentration was increased from 0.05 to 0.50% v/w. However, at concentration >0.25% v/w they tended to impart a bitter flavor in the juice. Among three concentrations of pectinase and cellulase, pectinase at 0.50% v/w produced higher yield, a sediment‐free clear juice and high‐quality juice. The results indicated that depectinated clarified prickly pear juice behaves as a Newtonian fluid. It was found that the activation energy (Ea) for viscous flow was in the range of 5.02×10³–20.06×10³ kJ/mol depending on the concentrations of pectinase and cellulase enzyme treatment of prickly pear juice, in contrast to 22.15×10³ kJ/mol in untreated juice. Volatile compound concentrations of twelve compounds were not affected by pectinase and cellulase treatment. Overall the quality of prickly pear juice was better in pectinase‐treated juice compared with untreated and cellulase‐treated juice.     

Purification and characterization of an amylase from Opuntiaficus‐indica seeds

BACKGROUND: In Tunisia, prickly pear fruit grow spontaneously; it is consumed as fresh fruit, juice or jam. When the fruit is used for juice production, the seeds are discarded and go to waste. Our study aimed to extract biomolecules from seeds by producing value‐added products from the fruits. RESULTS: An amylase from Opuntia ficus‐indica seeds was extracted and purified to homogeneity. An increase in specific activity of 113‐fold was observed. The apparent molecular mass of the enzyme is 64 kDa. The optimum pH and temperature for enzyme activity were pH 5 and 60 °C, respectively. Under these conditions, the specific activity is 245.5 U mg^?1. The enzyme was activated by Co²⁺ and Mg²⁺ (relative activity 117% and 113% respectively) at lower ion concentrations. It was strongly inhibited by Mn²⁺ and Fe²⁺. Cu²⁺ inhibited totally the activity of this enzyme, but Ca²⁺ has an inhibitory effect which increases with ion concentration. CONCLUSION: The extracted enzyme belongs to the exo type of amylases and is classified as a β‐cyclodextrin glycosyltransferase since it generates mainly β‐cyclodextrin from starch. It exhibits high thermal stability and a broad range of pH stability, making it a promising prospect for industrial and food applications. Copyright © 2012 Society of Chemical Industry     

Flavonol profile of cactus fruits (Opuntia ficus-indica) enriched cereal-based extrudates: Authenticity and impact of extrusion

In previous studies, it was hypothesized that isorhamnetin glycosides are the dominant flavonol derivatives occurring in the peels and cladodes of cactus Opuntia ficus-indica fruits and might be used as markers for analyzing the authenticity of food products containing (whole) cactus fruits or cladodes. In the present work, use of the whole yellow-orange fruit from cactus O. ficus-indica as an ingredient of rice- and corn-based snacks was evaluated. The impact of extrusion cooking on the flavonol profile was characterized in rice- and corn-based extruded products fortified with a freeze-dried preparation from the whole cactus fruit. HPLC analysis showed that the flavonol profile of cactus O. ficus-indica consisted of five prominent isorhamnetin glycosides with a concentration of 148.9 μg/100 mg dw. In contrast, the rice or corn grits used in the present study did not contain any flavonol at all. The freeze-dried fruit was added in different ratios (0, 2, 6, and 10%) to the rice or corn grits prior to the extrusion process. Analysis of the final extrusion products showed that flavonol profiles from the fortified rice or corn products, even at the lowest level of addition (2%), were similar to the original profile of the fruit before processing. Furthermore, the total flavonol content in extruded products was not significantly affected by extrusion cooking. This study showed that the unique flavonol profile of fruits from cactus O. ficus-indica might serve as a biochemical marker for the evaluation of the authenticity of products made from whole cactus fruit or the fruit's peel.     

Dielectric Properties of Pea Puree at 915 MHz and 2450 MHz as a Function of Temperature

Dielectric properties [dielectric constant (e′) and loss factor (e″)] of 20% (w/w) pea puree with and without fortification of 3.5 mg thiamin/ 100g pea puree at 915 MHz and 2450 MHz were measured from 25 to 125°C by the cavity perturbation techniaue. Thiamin did not affect dielectric properties at ihe concentration studied. The dielectric constant decreased as frequency and temperature increased. The loss factor increased as temperature increased at 915 MHz. However, the relationship between loss factor and temperature was not direct at 2450 MHz due to the contributions of dipolar and ionic losses.     

Dielectric properties of salmon (Oncorhynchus keta) and sturgeon (Acipenser transmontanus) caviar at radio frequency (RF) and microwave (MW) pasteurization frequencies

Radio frequency (RF) and microwave (MW) heating provide an important advantage of more rapid heat penetration in pasteurization processes for heat labile high value foods, which to date, have only been pasteurized by conductive heating. The objectives of this work were to determine the dielectric constant, loss factor and power penetration depth for salmon (0.8% and 2.3% total salt) and sturgeon (0.20 and 3.3% salt) caviars at RF frequency of 27 MHz and MW frequency of 915 MHz (20–80 °C). The dielectric constant (ε′) and dielectric loss factor (ε″) for salmon and sturgeon caviar increased markedly with increasing temperature at 27 MHz but not at 915 MHz. Power penetration depth was higher at 27 MHz compared to 915 MHz, and in unsalted compared to salted roe. Power penetration depth tended to decrease as temperature increased.     

Amino and organic acids of the prickly pear cactus (Opuntia ficus indica L.)

The amino acids of prickly pear (Opuntia ficus indica L.) proteins, free amino acids and nonvolatile organic acids were determined on fresh and lyophilised young pads. The calculated biological value of prickly pear protein was 72.6, relative to egg protein. Trace amounts of malonic, malic and citric acids in material collected at 1800 hours; traces 0.95 and 0.31 mg g^?1, respectively. In similar material analysed at 0600 hours, the concentrations of those acids were 0.36, 9.85, and 1.78 mg g^?1, respectively. Since there was a significant accumulation of the acids during the evening, crassulacean-type metabolism is suggested.