Mónica A. Nazareno

Singlet Molecular Oxygen Quenching Ability of Carotenoids in a Reverse-micelle Membrane Mimetic System¶

The influence of the medium heterogeneity upon the bimolecular rate constants for the physical quenching, kq, and chemical quenching, kr, of singlet molecular oxygen O2(1Δg) by seven natural and three synthetic carotenoids (CAR) with different substituent patterns was studied in a reverse micelle system of sodium bis(2‐ethylhexyl)sulfosuccinate, hexane and water. Because O2(1Δg) was generated inside the water pools of the reverse micelles by photosensitization of the water‐soluble dye rose bengal and the CAR are mainly located in the external hexane pseudophase, the quenching process was interpreted using a pseudophase model for the partition of O2(1Δg) between the water pools and the organic pseudophases. The kq values were mainly dependent on the extent of the double‐bond conjugation of the CAR, as demonstrated by a good empirical relationship between log(kq) and the energy E(S) of the longest wavelength transition π→π* of the CAR. In contrast, the kr values were almost independent of the extent of the double‐bond–conjugated system and about four orders of magnitude lower than kq. However, in all cases, CAR photobleaching was observed with the formation of various oxidation products, depending on the photosensitization time. Chromatographic and spectroscopic product analysis for the reaction products of β‐carotene with O2(1Δg) indicated the formation of the β‐carotene‐5,8‐endoperoxide as the primary oxidation product.

Immobilization of Caffeic Acid on a Polypropylene Film: Synthesis and Antioxidant Properties

The immobilization of caffeic acid (CA) on a polypropylene (PP) film was successfully performed through the covalent binding of the caffeoyl chloride on a modified polymeric surface of PP films grafted with hydroxyethyl methacrylate as monomer (PP-g-HEMA). The different reaction steps were monitored by FT-IR spectroscopy. The synthesized films were characterized by Folin-Ciocalteu method by measuring the available phenolic groups as caffeic acid equivalents linked to the surface. The antioxidant efficiency of the modified polymers was evaluated by typical spectrophometric methods, such as the bleaching of radicals DPPH(•) and ABTS(•+), and the inhibition of the enzymatically induced coupled oxidation of linoleic acid and betacarotene. The available phenolic groups on the modified film presented a good correlation with the antiradical activity toward DPPH(•). Moreover, the polymer synthesized in this work showed a good protective activity against ascorbic acid oxidation in real samples of orange juice.

Variations in Bioactive Substance Contents and Crop Yields of Lettuce (Lactuca sativa L.) Cultivated in Soils with Different Fertilization Treatments

Changes in crop yields and bioactive substance contents were studied in lettuce crop concerning the influence of soil nutritional status as a result of compost and vermicompost additions obtained from different organic substrates. Plant productions and main pigment contents in lettuce were higher in all the fertilized soils than in the untreated soil, with the exception of the one treated with urban solid waste compost. These positive effects correlate with nitrogen level increase in soil. However, the high saline input of this compost prepared from food home wastes interferes in lettuce growth and prevents it from being higher than the control. Marked decreases in lettuce phenolic contents and antiradical activity were found in most of the treatments. Composts and vermicomposts produced through the processing of cattle manures, agro-industrial organic wastes significantly increased lettuce crop yield enriching its pigment contents, although, in some cases, antioxidant value and phenolic levels were reduced.

Microencapsulation of betalains obtained from cactus fruit (Opuntia ficus-indica) by spray drying using cactus cladode mucilage and maltodextrin as encapsulating agents

The microencapsulation of betalains from cactus fruit by spray drying was evaluated as a stabilization strategy for these pigments. The betalains used as active agent were extracted from purple fruits of Opuntia ficus-indica (BE) and encapsulated with maltodextrin and cladode mucilage MD-CM and only with MD. The microcapsulates were characterized by scanning electron microscopy (SEM), thermal analysis (TGA-DSC), tristimulus colorimetry, as well as, their humidity, water activity and dietary fiber content were also determined. The active agent content was measured by UV-Vis spectrophotometry and its composition confirmed by HPLC-ESIMS. A pigment storage stability test was performed at 18 °C and different relative humidities. The addition of CM in the formulation increased the encapsulation efficiency, diminished the moisture content, and allowed to obtain more uniform size and spherical particles, with high dietary fiber content. These microencapsulates are promising functional additive to be used as natural colorant in the food industry.

Effect of different C3-aryl substituents on the antioxidant activity of 4-hydroxycoumarin derivatives.

The antioxidant activity of 4-hydroxycoumarin synthetic derivatives and 4-methylumbelliferone were determined taking 4-hydroxycoumarin as the reference compound. Six 3-aryl-4-hydroxycoumarin derivatives were synthesized from 4-hydroxycoumarin as precursor in order to evaluate changes in their antioxidant properties due to C3-aryl substituent nature. Free radical scavenging capacities of these compounds against two different species DPPH(·) and ABTS(·+) and the protecting ability towards the β-carotene-linoleic acid co-oxidation enzymatically induced by lipoxygenase were measured. In addition, the relationship between the activities of these molecules against DPPH radical and the bond dissociation energy of O-H (BDE) calculated using methods of computational chemistry was evaluated.

Encapsulating betalains from Opuntia ficus-indica fruits by ionic gelation: Pigment chemical stability during storage of beads.

Betalain encapsulation was performed by ionic gelation as a stabilization strategy for these natural pigments. Betalains were extracted from purple cactus fruits and encapsulated in calcium-alginate and in combination of calcium alginate and bovine serum albumin. Beads were characterised by scanning electron microscopy and thermal analysis using differential scanning calorimetry and thermogravimetry. Moisture sorption isotherms were determined. Bead morphology was affected by matrix composition. Pigments storage stability was evaluated at different equilibrium relative humidity and temperatures. Pigment composition of beads was determined by HPLC-MS-MS and degradation products were also analysed after storage; betalamic acid being the major one. Both types of matrices protected the encapsulated pigments, being their storage stability better at low relative humidity than that of the non-encapsulated control material. Antiradical activities of beads were proportional to remaining betalain contents. At high relative humidity, there was no protection and low storage stability was observed in the samples.

Caracterización de acelga fresca de Santiago del Estero (Argentina). Comparación del contenido de nutrientes en hoja y tallo. Evaluación de los carotenoides presentes

An integrated characterization study of Swiss chard grown in Santiago del Estero, Argentina, was carried out. As Swiss chard is a vegetable of important regional consumption, the determination of its basic constituents, minerals and pigments was done to appraise the nutritional value offered by this food in our area. Moisture, ash content, proteins, fats, available carbohydrates, total dietary fiber, chlorophylls and carotenoids were analysed, comparing the leaves and the stems. As to minerals, calcium, magnesium, sodium, manganese, zinc, iron, phosphorous, potassium, and boron were determined. Differences in the concentration of minerals, proteins, fats and fiber between the leaves and the stems were found, as well as the carotenoid content mainly in the leaves. These findings revealed important differences in energy content and provitamin A value, showing that the stem is a usable part of this vegetable to be recommended in diets with low calories.

Extracción de naringina de Citrus paradisi L. estudio comparativo y optimización de técnicas extractivas

The comparative study of the different extractive techniques of naringin was made, using grapefruit peel (Citrus paradisi). The best conditions for previous preparation of the material are the fragmentation of fresh peel and drying through a drying chamber and subsequent fragmentation. For fresh peel it turns to be more convenient the extraction with ethyl alcohol by Soxhlet system (obtaining 26 g/kg of fresh weight), while for dried peel the best results are obtained in the extraction with the mixture ethyl alcohol - water in the proportions 70:30 by maceration (20 g/kg of fresh weight) and reflux (22 g/kg of fresh weight). Evidences of the importance of water in the extraction process were observed. The values of naringin concentration in peel of different varieties of Citrus paradisi of the region of Argentinean North West were determined.

Effect of phenolic compounds on the oxidative stability of ground walnuts and almonds

Walnuts and almonds are mainly constituted by unsaturated fatty acids and, in consequence, are readily prone to oxidation reactions. These nuts are also rich in antioxidant substances such as polyphenols, which are mainly concentrated in the brown skins (BS) or seed coats. This study analyzes the effect of BS phenolic compounds on the oxidative stability of walnuts and almonds. For this reason, peeled and unpeeled ground nuts were comparatively evaluated after thermal treatments as well as after room temperature storage. Furthermore, volatile compound emission due to thermally induced oxidation of the ground nuts was analyzed using HS-SPME-GC-MS. Several secondary oxidation products were identified in the headspace, and volatile product formation was considerably larger in nuts with BS than in peeled ones. Consistently, the former showed higher malondialdehyde levels after heating which indicates a prooxidant effect of BS presence. In order to verify these findings, a water-in-oil microemulsion was used as a model system to assess the role of nut phenolic compounds on lipid oxidation promotion. The hydroperoxide and malondialdehyde content was determined, as a measurement of primary and secondary oxidation enhancement, respectively. A dose dependent prooxidant effect on linoleic acid thermal oxidation was also observed when BS polyphenolic extracts as well as pure phenolic compounds were added.

Lactic Acid Fermentation Improved Textural Behaviour, Phenolic Compounds and Antioxidant Activity of Chia (Salvia hispanica L.) Dough

In this work, autochthonous lactic acid bacteria (LAB) were isolated from chia (Salvia hispanica L.) dough and selected on the basis of the kinetics of acidification and proteolytic activity. Strain no. C8, identified as Lactobacillus plantarum C8, was selected and used as starter to obtain chia sourdough. Lactic acid fermentation increased the organic acid mass fractions (lactic, acetic and phenyl lactic acids to 12.3 g, 1.0 g and 23.8 µg per kg of dough respectively), and antioxidant activities, which increased by approx. 33-40% compared to unfermented chia flour dough. In addition, total phenolic content increased 25% and its composition was strongly modified after 24 h of fermentation by L. plantarum C8. Chlorogenic acid was only found in the fermented dough (2.5 mg/g), while ferulic acid was detected from the beginning of fermentation, being 32% higher in chia sourdough (5.6 mg/g). The use of fermented chia sourdough improved the overall characteristics of white bread, including physical (e.g. reduced hardness and chewiness of the crumb) and antioxidant properties (25% on average), compared to the white bread. These results indicate that the use of chia sourdough could be a promising alternative to improve the technological and antioxidant properties of wheat bread. In addition, this work has shown, for the first time, that lactic acid bacterium is able to ferment chia dough, improving its overall characteristics.