Coralia Osorio

Characterization of the Key Aroma Compounds in Pink Guava (Psidium guajava L.) by Means of Aroma Re-engineering Experiments and Omission Tests

Seventeen aroma-active volatiles, previously identified with high flavor dilution factors in fresh, pink Colombian guavas (Psidium guajava L.), were quantified by stable isotope dilution assays. On the basis of the quantitative data and odor thresholds in water, odor activity values (OAV; ratio of concentration to odor threshold) were calculated. High OAVs were determined for the green, grassy smelling (Z)-3-hexenal and the grapefruit-like smelling 3-sulfanyl-1-hexanol followed by 3-sulfanylhexyl acetate (black currant-like), hexanal (green, grassy), ethyl butanoate (fruity), acetaldehyde (fresh, pungent), trans-4,5-epoxy-(E)-2-decenal (metallic), 4-hydroxy-2,5-dimethyl-3(2H)-furanone (caramel, sweet), cinnamyl alcohol (floral), methyl (2S,3S)-2-hydroxy-3-methylpentanoate (fruity), cinnamyl acetate (floral), methional (cooked potato-like), and 3-hydroxy-4,5-dimethyl-2(5H)-furanone (seasoning-like). Studies on the time course of odorant formation in guava puree or cubes, respectively, showed that (Z)-3-hexenal was hardly present in the intact fruits, but was formed very quickly during crushing. The aroma of fresh guava fruit cubes, which showed a very balanced aroma profile, was successfully mimicked in a reconstitute consisting of 13 odorants in their naturally occurring concentrations. Omission tests, in which single odorants were omitted from the entire aroma reconstitute, revealed (Z)-3-hexenal, 3-sulfanyl-1-hexanol, 4-hydroxy-2,5-dimethyl-3(2H)-furanone, 3-sulfanylhexyl acetate, hexanal, ethyl butanoate, cinnamyl acetate, and methional as the key aroma compounds of pink guavas.

Microencapsulation by spray-drying of anthocyanin pigments from corozo (Bactris guineensis) fruit.

The anthocyanins of Bactris guineensis fruit were isolated with the aid of high-speed countercurrent chromatography (HSCCC) and preparative HPLC, and their chemical structures were elucidated by using spectroscopic methods. Among the identified pigments, cyanidin-3-rutinoside and cyanidin-3-glucoside were characterized as major constituents (87.9%). Peonidin-3-rutinoside, peonidin-3-glucoside, cyanidin-3-(6-O-malonyl)glucoside, and cyanidin-3-sambubioside were present in minor amounts. Four anthocyanin ethanolic extracts (AEEs) were obtained by osmotic dehydration and Soxhlet extraction and physicochemically characterized. The composition of anthocyanins was monitored by HPLC-PDA. The extracts with the highest anthocyanin content were subjected to the spray-drying process with maltodextrin. The so-obtained spray-dried powders were analyzed by scanning electron microscopy (SEM) and found to consist of spherical particles <50 microm in size. The anthocyanin composition was similar to that of the fruit. The microencapsulated powders were analyzed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), revealing that they are quite stable until 100 degrees C. Storage stability tests of microcapsules showed that the release of anthocyanin pigments follows pseudo-first-order kinetics and that the process rate is increased by temperature and humidity. The most suitable conditions for storage were below 37 degrees C and <76% relative humidity, respectively.

Characterization of the Aroma-Active Compounds in Pink Guava (Psidium guajava, L.) by Application of the Aroma Extract Dilution Analysis

The volatiles present in fresh, pink-fleshed Colombian guavas ( Psidium guajava, L.), variety regional rojo, were carefully isolated by solvent extraction followed by solvent-assisted flavor evaporation, and the aroma-active areas in the gas chromatogram were screened by application of the aroma extract dilution analysis. The results of the identification experiments in combination with the FD factors revealed 4-methoxy-2,5-dimethyl-3(2 H)-furanone, 4-hydroxy-2,5-dimethyl-3(2 H)-furanone, 3-sulfanylhexyl acetate, and 3-sulfanyl-1-hexanol followed by 3-hydroxy-4,5-dimethyl-2(5 H)-furanone, ( Z)-3-hexenal, trans-4,5-epoxy-( E)-2-decenal, cinnamyl alcohol, ethyl butanoate, hexanal, methional, and cinnamyl acetate as important aroma contributors. Enantioselective gas chromatography revealed an enantiomeric distribution close to the racemate in 3-sulfanylhexyl acetate as well as in 3-sulfanyl-1-hexanol. In addition, two fruity smelling diastereomeric methyl 2-hydroxy-3-methylpentanoates were identified as the ( R,S)- and the ( S,S)-isomers, whereas the ( S,R)- and ( R,R)-isomers were absent. Seven odorants were identified for the first time in guavas, among them 3-sulfanylhexyl acetate, 3-sulfanyl-1-hexanol, 3-hydroxy-4,5-dimethyl-2(5 H)-furanone, trans-4,5-epoxy-( E)-2-decenal, and methional were the most odor-active.

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.

Thermal and structural study of guava (Psidium guajava L) powders obtained by two dehydration methods

Two food products (powders) were obtained by hot-air drying or lyophilisation methods on the whole guava fruits. The powders were characterised by sensory and thermal analyses (TGA-DSC), infrared spectroscopy (IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Thermal, morphological and structural characterisations showed a similar behaviour for the two solids. TGA-DSC and IR showed the presence of pectin as the main constituent of solids. A semi-crystalline profile was evidenced by XRD, and lamellar/spherical morphologies were observed by SEM. Sensory analyses revealed an aroma highly related to guava. These value-added food products are an alternative to process guava and avoid loss during postharvest handling.

Studies on aroma generation in lulo (Solanum quitoense): enzymatic hydrolysis of glycosides from leaves

Abstract Five C13-norisoprenoid glycosides, isolated from lulo (Solanum quitoense) leaves, were subjected to enzymatic hydrolysis with a commercial glucosidase (emulsin) and also with an enzymatic preparation having glycosidase activity, isolated from lulo fruit pulp. The volatile compounds generated after reaction were characterized by capillary GC and capillary GC–MS. Lulo fruit glycosidases were extracted by ammonium sulfate precipitation at pH 6.5 and subjected to fractionation by hydrophobic interaction chromatography (HIC) on phenyl Sepharose® gel, and some of their properties were determined. As the result of enzymatic hydrolysis with exogenous enzymes (emulsin), glycosides isolated from lulo leaves produced only the aglycone (glycosidically bound volatile); in contrast, enzymatic hydrolysis of glycosides, using endogenous enzymes (lulo fruit glycosidases), generated additional volatile compounds, some recognisable as components of fruit flavour. The role of lulo leaf glycosides as flavour precursors was confirmed.

Chemical and sensory comparison of fresh and dried lulo (Solanum quitoense Lam.) fruit aroma

The odour-active volatile compounds of lulo fruit (Solanum quitoense Lam.) were isolated by solvent extraction followed by solvent-assisted flavour evaporation (SAFE). GC-O and GCMS analyses as well as quantitation by internal standard method showed that (Z)-3-hexenal, ethyl butanoate, 3-sulphanylhexyl acetate, and ethyl hexanoate were key aroma compounds in this fruit. Other odorants with relevance because their contribution (high OAVs) to the overall aroma were 4-hydroxy-2,5-dimethyl-3(2H)-furanone, methyl benzoate, (E)-2-hexenal, and hexanal. Lulo fruit pulp in presence of maltodextrin DE-20 was dried by using four different types of drying methods: hot air-drying (HD), spray drying (SD), lyophilisation (LD), and ultrasonic convective hot air-drying (HUD). LD sample exhibited the highest sensory rank (lulo-like) in comparison with fresh fruit pulp. Hot-air drying processes (HD and HUD) changed adversely the aroma of lulo fruit pulp.

Oxygenated monoterpenoids from badea (Passiflora quadrangularis) fruit pulp

The new monoterpenoids (2E)-2,6-dimethyl-2,5-heptadienoic acid, (2E)-2,6-dimethyl-2,5-heptadienoic acid beta-D-glucopyranosyl ester, (5E)-2,6-dimethyl-5,7-octadiene-2,3-diol, and (3E)-3,7-dimethyl-3-octene-1,2,6,7-tetrol were isolated from the fruit pulp of Passiflora quadrangularis along with the known 2,5-dimethyl-4-hydroxy-3(2H)-furanone beta-D-glucopyranoside.

Chemical studies on curuba (Passiflora mollissima (Kunth) L. H. Bailey) fruit flavour.

The odour-active volatiles of curuba fruit (Passiflora mollissima (Kunth) L. H. Bailey) were isolated by solvent assisted flavour evaporation (SAFE). GC-O and GC-MS analyses identified linalool, hexyl acetate, 1,8-cineole, and butyl acetate as key aroma compounds of this fruit. Other odorants relevant because of their contribution to the overall aroma were: 2-methylpropyl acetate, (Z)-3-hexen-1-ol, and (Z)-3-hexenyl acetate. Sulphur compounds, 3-sulfanylhexyl acetate and methional, were reported here for first time as odour-active volatiles in curuba. By HPLC-ESI-MS analyses of glycosidic mixtures and GC-MS analyses of volatiles released enzymatically with a glucosidase, (Z)-3-hexenyl β-D-glucopyranoside and linalyl β-D-glucopyranoside were identified as aroma precursors in P. mollissima fruit. Thermal treatment of the glycosidic mixture at native pH of fruit gave furanoid cis- and trans-linalool oxides, as well as, α-terpineol, compounds that exhibit flowery odour notes. Biogenic relationships among odour-active volatiles and their glycosidic precursors were also proposed.

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.