Selina Wang

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Metal promoted vinylcyclopropane–cyclopentene rearrangements: Reactions ripe for mechanism-based catalyst design

Journal of Organometallic Chemistry, 2006

This brief review describes experimental and theoretical data relevant to the mechanisms of trans... more This brief review describes experimental and theoretical data relevant to the mechanisms of transition metal promoted vinylcyclopropane-cyclopentene rearrangements. In particular, reactions utilizing Pd(0), Rh(I), and Ni(0) are highlighted and compared to analogous reactions not involving transition metals.

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Low Acrylamide Flatbreads Prepared from Colored Rice Flours and Relationship to Asparagine and Proximate Content of Flours and Flatbreads

Foods, 2021

Acrylamide is a potentially toxic compound present in many plant-based foods, such as coffee, bre... more Acrylamide is a potentially toxic compound present in many plant-based foods, such as coffee, breads, and potato fries, which is reported to have carcinogenic, neurotoxic, and antifertility properties in vivo, suggesting the need to keep the acrylamide content of widely consumed food as low as possible. As pigmented rice contains bioactive phenolic and flavonoid compounds, the objective of this study was to potentially enhance the beneficial properties of flatbreads by evaluating the acrylamide content and proximate composition of 12 novel flatbreads prepared from the following commercial pigmented rice seeds: Black Japonica, Chinese Black, French Camargue, Himalayan Red, Long Grain Brown, Purple Sticky, Short Grain Brown, Wehani, Wild, Indian Brown Basmati, Organic Brown Jasmine, and Organic Jade Pearl. Although acrylamide levels ranged from 4.9 µg/kg in Long Grain Brown to 50.8 µg/kg in Chinese Black, the absolute values were all low (though statistically significantly differences...

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Report: Packaging influences on olive oil quality: A review of the literature

Extra virgin olive oil is a fresh juice extracted from olive fruits. As with other fruit juices, ... more Extra virgin olive oil is a fresh juice extracted from olive fruits. As with other fruit juices, the freshness and flavor quality of olive oil diminish with time, and the rate of deterioration is influenced by packaging type. To maximize shelf stability, the ideal packaging material would prevent light and air penetration, and the oils would be stored in the dark at 16 - 18 degreesC (61 - 64 degreesF). Table 1 indicates how chemical components in olive oil influence the shelf life of the oil.

Low Acrylamide Flatbreads from Colored Corn and Other Flours

Foods, 2021

Dietary acrylamide formed during baking and frying of plant-based foods such as bread and other c... more Dietary acrylamide formed during baking and frying of plant-based foods such as bread and other cereal products, coffee, fried potatoes, and olives is reported to induce genotoxic, carcinogenic, neurotoxic, and antifertility properties in vivo, suggesting the need to keep the acrylamide content low with respect to widely consumed heat-processed food including flatbreads. Due to the fact that pigmented corn flours contain biologically active and health-promoting phenolic and anthocyanin compounds, the objective of this study was to potentially define beneficial properties of flatbread by evaluating the acrylamide content determined by high-performance liquid chromatography/mass spectrometry (HPLC/MS) with a detection limit of 1.8 µg/kg and proximate composition by standard methods of six experimental flatbreads made from two white, two blue, one red, and one yellow corn flours obtained by milling commercial seeds. Acrylamide content was also determined in experimental flatbreads made...

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Pistachio Kernel Composition of ‘Kalehghouchi’, ‘Pete 1’, and ‘Lost Hills’ in California

HortScience, 2020

Moisture and fat content, fatty acid profile, and volatile terpenes were measured for the first t... more Moisture and fat content, fatty acid profile, and volatile terpenes were measured for the first time for ‘Kalehghouchi’, ‘Pete 1’, and ‘Lost Hills’ pistachios grown at two California microclimates: Lost Hills and Parlier. ‘Kalehghouchi’ had the highest moisture content, followed by ‘Pete 1’ and ‘Lost Hills’, respectively. While the moisture content of ‘Kalehghouchi’ was not significantly affected by location, it was lower for ‘Pete 1’ grown at Parlier (40.8 vs. 40.8 g/100 g) and higher for ‘Lost Hill’ grown there (48.2 vs. 45.2 g/100 g). ‘Pete 1’ grown at the Parlier site had a higher fat content compared with ‘Lost Hills’ (47.7 vs. 43.0 g/100 g). ‘Kalehghouchi’ had a lower fat content at Parlier compared with Lost Hills (42.0 vs. 44.9 g/100 g), and ‘Lost Hills’ was unaffected by location. The main fatty acid measured in the pistachio samples was oleic acid (52% to 58%), followed by linoleic (26% to 33%) and palmitic acids (11% to 13%). While oleic acid content of ‘Lost Hills’ and ‘...

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Comparative Effect of Hammer Mill Screen Size and Cell Wall-Degrading Enzymes During Olive Oil Extraction

ACS Omega, 2020

The influence of hammer mill screen size (4.5 and 8.5 mm) and enzyme addition (control and 500 pp... more The influence of hammer mill screen size (4.5 and 8.5 mm) and enzyme addition (control and 500 ppm) on olive fruit cell wall breakdown and its consequences in terms of oil recovery and the phenolic content of olive oil was studied at the laboratory scale for "Arbequina" and "Koroneiki" at two different maturities. Water recovery and water-soluble carbohydrates in olive paste after malaxation were measured as an indicator of cell wall breakdown. Smaller screen size and enzymes increase oil recovery for Arbequina with a maturity index of 1.6 (6.3−6.6%); and for Koroneiki at a maturity index of 0.2 (15.0−38%) and 2.6 (1.3− 4.3%). For both cultivars, the increase in oil recovery is larger in green fruits compared to more ripe fruit. Water recovery and watersoluble carbohydrates increase with small screen size and the enzyme treatments, even when no increment in oil recovery is observed. The water recovery range was 143−239% for Arbequina and 150−262% for Koroneiki; water-soluble carbohydrate range was 1.8−12.7 g/kg for Arbequina and 0.5−5.4 g/kg for Koroneiki. In general, smaller hammer mill screen size and enzymes increase total phenols in the oil, with a larger difference between control and treatment for green fruit than for the ripe fruit. For Arbequina, increases in total phenol content were in the range of 45−60 and 5−20% at maturity index 1.6 and 3.3, respectively. For Koroneiki, the increases were in the range of 31−121 and 7−9% at maturity index 0.2 and 2.6, respectively. Application of cell wall-degrading enzymes improves the cell wall breakdown caused by hammer mill, leading to higher oil recovery and total phenol content. The magnitude of the effect depends on the cultivar and olive fruit maturity.

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Cultivar Determines Fatty Acids and Phenolics Dynamics for Olive Fruit and Oil in Super-High-Density Orchards

Agronomy, 2021

The dynamics of maturation index, water and oil concentrations, and total phenols in olive fruit,... more The dynamics of maturation index, water and oil concentrations, and total phenols in olive fruit, together with fatty acids and total phenols content in olive oil, was studied as a function of time after flowering for super-high-density ‘Arbequina’, ‘Arbosana’ and ‘Koroneiki’ using data collected in three seasons. Oil concentration increased linearly from the middle of August until reaching a plateau by the end of November for all three cultivars, with ‘Koroneiki’ (45.7 g/100 g) and ‘Arbosana’ (45.4 g/100 g) showing higher maximum oil concentration than ‘Arbequina’ (41.8 g/100 g). While total phenols in the fruit decreased linearly during the harvest for all three cultivars, phenolics in oil peaked at 180 days after flowering (400 mg/kg) for ‘Arbequina’ and at 160 days after flowering (600 mg/kg) for ‘Koroneiki’. For ‘Arbosana’, total phenols in oil decreased linearly with a maximum of 400 mg/kg for early harvest oils. Fatty acid dynamics was largely affected by genotype, with ‘Arbe...

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Olive Oil from “Sikitita” under Super‐High‐Density Planting System in California: Impact of Harvest Time and Crop Season

Journal of the American Oil Chemists' Society, 2020

Chemical Compositional Changes in Over-Oxidized Fish Oils

Foods, 2020

A recent study has reported that the administration during gestation of a highly rancid hoki live... more A recent study has reported that the administration during gestation of a highly rancid hoki liver oil, obtained by oxidation through sustained exposure to oxygen gas and incident light for 30 days, causes newborn mortality in rats. This effect was attributed to lipid hydroperoxides formed in the omega-3 long-chain polyunsaturated fatty acid-rich oil, while other chemical changes in the damaged oil were overlooked. In the present study, the oxidation condition employed to damage the hoki liver oil was replicated, and the extreme rancidity was confirmed. A detailed analysis of temporal chemical changes resulting from the sustained oxidative challenge involved measures of eicosapentaenoic acid/docosahexaenoic acid (EPA/DHA) omega-3 oil oxidative quality (peroxide value, para-anisidine value, total oxidation number, acid value, oligomers, antioxidant content, and induction time) as well as changes in fatty acid content, volatiles, isoprostanoids, and oxysterols. The chemical descriptio...

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Ingredient label claim compliance and oxidative quality of EPA/DHA omega-3 retail products in the U.S

Journal of Food Composition and Analysis, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Changes in Chemical Compositions of Olive Oil under Different Heating Temperatures Similar to Home Cooking

Journal of Food Chemistry and Nutrition, 2016

Four olive oils with varying amounts of total phenols were exposed to four different heating cond... more Four olive oils with varying amounts of total phenols were exposed to four different heating conditions. Chemical parameters such as free fatty acid, peroxide values, UV absorbency, total phenols, individual phenols, α-tocopherol, squalene, oleocanthal, fatty acid profile and smoke point were measured before and after heating to evaluate the impact of heating conditions on the oils. We found olive oils have reasonably high smoke point that is suitable for typical home-cooking conditions and fresh olive oil with low FFA and high phenolics are important for the conservation of olive oil quality and health benefits. A larger degree of oxidation occurred as with increase of heating time and temperature, oils with high level of phenols produced less polar compounds than oils with lower levels of phenols, including refined oils. A significant amount of total phenols and individual phenols such as oleocanthal remained after heating at 121 °C for 10 and 20 minutes, most of squalene stay in...

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Near-Infrared (NIR) Spectrometry as a Fast and Reliable Tool for Fat and Moisture Analyses in Olives

ACS Omega, 2018

The evaluation of fat and moisture contents for olive fruits is crucial for both olive growers an... more The evaluation of fat and moisture contents for olive fruits is crucial for both olive growers and olive oil processors. Reference methods, such as Soxhlet extraction, used for fat content determination in olive fruits are time-and solvent-consuming and labor intensive. Near-infrared (NIR) spectroscopy is proposed as a solution toward rapid and nondestructive analyses of olive fruit fat and moisture contents. In the present work, comparative studies of the fat and moisture quantification methods were performed on four cultivars (Arbosana, Arbequina, Chiquitita, and Koroneiki) during six different harvesting time points to determine the potential of NIR as an alternative methodology. The impact of olive paste crushing degree on NIR performance was also investigated using three different grid sizes (4, 6, and 8 mm) on a hammer mill, in addition to a blade crusher. Results indicate a satisfactory correlation between the reference Soxhlet and NIR methods with R 2 = 0.995. A comparison study of moisture content was also done on NIR and the use of conventional oven with the R 2 value of 0.995. The crushing blade produced higher values in both moisture and fat contents in comparison to the hammer mill. The evaluation indicates that when building a chemometric model, all crush sizes and blade sizes should be represented in the model for highest accuracy.

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β-Glucosidase Discovery and Design for the Degradation of Oleuropein

ACS Omega, 2018

Current lye processing for debittering California black table olives produces large amounts of ca... more Current lye processing for debittering California black table olives produces large amounts of caustic wastewater and destroys many of the beneficial phenolic compounds in the fruit. Herein, we propose using enzyme treatment in place of lye, potentially reducing the amount and causticity of wastewater produced. By specifically targeting the bitterness-causing compound, oleuropein, retention of other beneficial phenolics may be possible. A β-glucosidase from Streptomyces sp. was identified from a screen of 22 glycosyl hydrolases to completely degrade oleuropein in 24 h. Computational modeling was performed on this enzyme, and mutation C181A was found to improve the rate of catalysis by 3.2-fold. This mutant was tested in the context of the olive fruit and leaf extract. Degradation was observed in the olive leaf extract but not in the fruit matrix, suggesting that enzyme fruit penetration is a limiting factor. This work discovers and begins the refinement process for an enzyme that has the catalytic properties for debittering olives and provides direction for future engineering efforts required to make a product with commercial value.

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Oleocanthal-rich extra virgin olive oil demonstrates acute anti-platelet effects in healthy men in a randomized trial

Journal of Functional Foods, 2017

The phenolic profiles of extra virgin olive oils (EVOOs) may influence their cardiovascular benef... more The phenolic profiles of extra virgin olive oils (EVOOs) may influence their cardiovascular benefits. In a randomized crossover of acute EVOO intake on platelet function, participants (n=9) consumed 40 mL of EVOO weekly. EVOOs were matched for total phenolic content and were either tyrosol-poor with 1:2 oleacein/oleocanthal (D2 i 0.5), or 2:1 oleacein/oleocanthal (D2 i 2), or predominantly tyrosol (D2 i 0). Ibuprofen provided a platelet inhibition control. Blood was collected pre-and 2 hr post-EVOO intake. D2 i 0.5 and D2 i 2 reduced 1 µg/mL collagen-stimulated maximum platelet aggregation (Pmax), with effects best correlated to oleocanthal intake (R=0.56, P=0.002). Total phenolic intake was independently correlated to eicosanoid production inhibition, suggesting that cyclooxygenase blockade was not responsible for the Pmax inhibition. Five participants exhibited >25% ΔPmax declines with D2 i 0.5 and D2 i 2 intake and plasma metabolomic profiles discriminated subjects by oil responsivity. Platelet responses to acute EVOO intake are associated with oil phenolic composition and may be influenced by diet.

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Impact of industrial hammer mill rotor speed on extraction efficiency and quality of extra virgin olive oil

Food Chemistry, 2018

Crushing is a key step during olive oil extraction. Among commercial crushers, the hammer mill is... more Crushing is a key step during olive oil extraction. Among commercial crushers, the hammer mill is the most widely used due to its robustness and high throughput. In the present work, the impact of hammer mill rotor speed on extraction yield and overall quality of super-high-density Arbosana olive oils were assessed in an industrial facility. Our results show that increasing the rotor speed from 2400 rpm to 3600 rpm led to a rise in oil yield of 1.2%, while conserving quality parameters. Sensory analysis showed more pungency with increased rotation speed, while others attributes were unaffected. Volatile compounds showed little variation with the differences in crusher speed; however, total phenols content, two relevant secoiridoids, and triterpenoids levels increased with rotor speed. Hammer mill rotor speed is a processing variable that can be tuned to increase the extraction efficiency and modulate the chemical composition of extra virgin olive oil.

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Cover Picture: Biomimetic Total Synthesis of Santalin Y (Angew. Chem. Int. Ed. 17/2015)

Angewandte Chemie International Edition, 2015

that the key step is a cascade involving a (3 + 2) cycloaddition and a Friedel-Crafts ring closur... more that the key step is a cascade involving a (3 + 2) cycloaddition and a Friedel-Crafts ring closure which generates the unique oxafenestrane framework of santalin Y and sets its five stereocenters in one operation. The Triberg Falls in the background, located in the Black Forest, are Germany's longest with 163 m.

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Biomimetische Totalsynthese von Santalin Y

Angewandte Chemie, 2015

Eine biomimetische Totalsynthese von Santalin Y, einem strukturell komplexen, jedoch racemischen ... more Eine biomimetische Totalsynthese von Santalin Y, einem strukturell komplexen, jedoch racemischen Naturstoff, wird beschrieben. Ihr Schlüsselschritt ist eine (3+2)-Cycloaddition eines Benzylstilbens an ein "vinyloges Oxidopyrylium", gefolgt von einer intramolekularen Friedel-Crafts-Reaktion. Diese Kaskade erzeugt das einzigartige Oxafenestran-Gerüst des Zielmoleküls und setzt seine fünf Stereozentren in einem einzigen Vorgang. Unsere Arbeit liefert einen schnellen Zugang zu Santalin Y und klärt dessen biosynthetische Beziehung zu anderen aus rotem Sandelholz isolierten Farbstoffen auf. Die strukturelle Vielfalt und Komplexität von Naturstoffen trägt viel zur Faszination bei, die sie seit jeher auf Chemiker ausüben. Metaboliten, die mehrere Stereozentren tragen treten gewçhnlich in enantiomerenreiner oder scalemischer Form auf. Komplexe Naturstoffe, die echte Racemate sind, sind dagegen vergleichsweise selten. Es gibt jedoch einige nennenswerte Ausnahmen, von denen eine kleine Auswahl in Abbildung 1 gezeigt ist. Die Bildung dieser Naturstoffe wird häufig mit pericyclischen Reaktionen in Zusammenhang gebracht, wie beispielsweise Diels-Alder-Reaktionen, die bis zu vier Stereozentren in einem einzigen Schritt aus achiralen Vorprodukten aufbauen kçnnen. Elektrocyclisierungskaskaden oder Cyclisierungen durch ionische Zwischenstufen kçnnen zu ähnlicher oder sogar hçherer Komplexität führen. Das Auftreten solcher Reaktionen in Biosynthesewegen wurde durch eine Vielzahl biomimetischer Synthesen belegt. Klassiker, wie beispielsweise die Synthese von Carpanon [1] und Endiandrinsäure A, [2] wurden kürzlich durch die Synthesen von Rubioncolin B, [3] Exiguamin B [4] und Kingianin A [5] ergänzt. Santalin Y ist ein weiterer komplexer und zugleich racemischer Naturstoff, der im "Roten Sandelholz", dem Kernholz von Pterocarpus santalinus vorkommt (Abbildung 2 A). Die tiefrote Farbe des hochgeschätzten Materials wird durch eine Serie von Benzoxanthenonen, nämlich Santalin A, B und Santarubin A, B [6] bewirkt. Abbildung 1. Komplexe racemische Naturstoffe, die durch biomimetische Synthesen gebildet wurden. Abbildung 2. A) Die Santaline und Santarubine. B) Rçntgenkristallstruktur von Santalin Y (kristallisiert aus Acetonitril) in Draufsicht und Seitenansicht. Einige Wasserstoffatome wurden zur Klarheit entfernt.

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Quantum chemical study of the isomerization of 24-methylenecycloartanol, a potential marker of olive oil refining

Journal of molecular modeling, 2015

Quantum chemical calculations on the isomerization of 24-methylenecycloartanol are described. An ... more

Computer Design of Novel Pesticides Against the Olive Fruit Fly (Bactrocera oleae)

The olive fruit fly Bactrocera oleae targets the fruits of olive trees in the Mediterranean and h... more The olive fruit fly Bactrocera oleae targets the fruits of olive trees in the Mediterranean and has been causing increasing economic harm to Californian growers. Past efforts to combat Bactrocera oleae by limiting the spread of its population have included traps, bait sprays, barrier films, and the release of natural predators, but these methods do little against large populations and many fruit fly generations are now resistant to the chemical compounds used. This study attempts to improve the current pesticides targeting the ecdysone receptor of Bactrocera oleae by comparing current pesticides and then using computer software to build upon them. After several generations of molecules were docked in the enzyme 1R20 (ecdysone receptor for a similar insect, Heliothis virenscens), the novel molecule "icon11conf1c0m2" was found to have a significantly better docking score, based on structural matches and hydrogen bonding, than the best original pesticide RH-2485. If further research is done docking "icon11conf1c0m2" into other insect ecdysone receptors, it could have the potential to serve as another more efficient Insect Growth Regulator. Although the enzyme for Bactrocera oleae was not accessible, the pesticides found by this study can be tailored to it when it becomes available.

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Linking Chemical Parameters to Sensory Panel Results through Neural Networks To Distinguish Olive Oil Quality

Journal of Agricultural and Food Chemistry, 2014

A wide variety of olive oil samples from different origins and olive types has been chemically an... more A wide variety of olive oil samples from different origins and olive types has been chemically analyzed as well as evaluated by trained sensory panelists. Six chemical parameters have been obtained for each sample (free fatty acids, peroxide value, two UV absorption parameters (K232 and K268), 1,2-diacylglycerol content, and pyropheophytins) and linked to their quality using an artificial neural network-based model. Herein, the nonlinear algorithms were used to distinguish olive oil quality. Two different methods were defined to assess the statistical performance of the model (a K-fold cross-validation (K = 6) and three different blind tests), and both of them showed around a 95-96% correct classification rate. These results support that a relationship between the chemical and the sensory analyses exists and that the mathematical tool can potentially be implemented into a device that could be employed for various useful applications.

Selina Wang

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