Selina C. Wang

Prediction of a new pathway to presilphiperfolanol.

Quantum chemical calculations on the conversion of farnesyl diphosphate to presilphiperfolanol are described. On the basis of the results of this theoretical study, we predict a new mechanism for presilphiperfolanol formation that involves the intermediacy of nerolidyl diphosphate and an unusual reaction step in which a 1,2-alkyl shift and a transannular alkene attack are combined into a concerted process.

Theoretical Studies on Synthetic and Biosynthetic Oxidopyrylium-Alkene Cycloadditions: Pericyclic Pathways to Intricarene

Herein we describe quantum chemical calculations (B3LYP) on the intramolecular oxidopyrylium-alkene cycloadditions used in two recently reported total syntheses of (+)-intricarene, and possibly also occurring during its biosynthesis. Using theory, we address (1) the necessity of enzyme intervention if this reaction occurs in Nature and (2) the effects of substituents attached to the oxidopyrylium and alkene groups on the activation barriers for cycloaddition.

In-Depth Assessment of Analytical Methods for Olive Oil Purity, Safety, and Quality Characterization

This paper evaluates the performance of the current analytical methods (standard and widely used otherwise) that are used in olive oil for determining fatty acids, triacylglycerols, mono- and diacylglycerols, waxes, sterols, alkyl esters, erythrodiol and uvaol, tocopherols, pigments, volatiles, and phenols. Other indices that are commonly used, such as free acidity and peroxide value, are also discussed in relation to their actual utility in assessing quality and safety and their possible alternatives. The methods have been grouped on the basis of their applications: (i) purity and authenticity; (ii) sensory quality control; and (iii) unifying methods for different applications. The speed of the analysis, advantages and disadvantages, and multiple quality parameters are assessed. Sample pretreatment, physicochemical and data analysis, and evaluation of the results have been taken into consideration. Solutions based on new chromatographic methods or spectroscopic analysis and their analytical characteristics are also presented.

Membrane-Filtered Olive Mill Wastewater: Quality Assessment of the Dried Phenolic-Rich Fraction.

A current trend in olive mill wastewater (OMWW) management is to not only decrease environmental pollution but also to extract and utilize valuable by-products. Therefore, the objectives of this study were to explore different techniques for drying a phenolic-rich membrane filtration fraction of OMWW and compare the techniques in terms of the dried product quality and feasibility of the process. The OMWW from 2 (3-phase and 2-phase) California mills was subjected to a 2-step membrane filtration process using a novel vibratory system. The reverse osmosis retentate (RO-R) is a phenolic-rich coproduct stream, and the reverse osmosis permeate is a near-pure water stream that could be recycled into the milling process. Spray-, freeze-, and infrared-drying were applied to obtain solid material from the RO-R. Drying of the RO-R was made possible only with addition of 10% maltodextrin as a carrier. The total soluble phenolics in dried RO-R were in the range 0.15 to 0.58 mg gallic acid equivalents/g of dry weight for 2-phase RO-R, and 1.38 to 2.17 mg gallic acid equivalents/g of dry weight for the 3-phase RO-R. Spray-dried RO-R from 3-phase OMWW showed remarkable antioxidant activity. Protocatechuic acid, tyrosol, vanillic acid, and p-coumaric acid were quantified in all dried RO-R, whereas 3-hydroxytyrosol was found in 3-phase dried RO-R. This combination of separation and drying technologies helps to add value and shelf-stability to an olive oil by-product and increase environmental sustainability of its production.

Deep insight into the minor fraction of virgin olive oil by using LC-MS and GC-MS multi-class methodologies

Several analytical methods are available to evaluate virgin olive oil (VOO) minor compounds; however, multi-class methodologies are yet rarely studied. Herewith, LC-MS and GC-MS platforms were used to develop two methods capable of simultaneously determine more than 40 compounds belonging to different VOO minor chemical classes within a single run. A non-selective and highly efficient liquid-liquid extraction protocol was optimized for VOO minor components isolation. The separation and detection conditions were adjusted for determining phenolic and triterpenic compounds, free fatty acids and tocopherols by LC-MS, plus sterols and hydrocarbons by GC-MS. Chromatographic analysis times were 31 and 50u202fmin, respectively. A comparative assessment of both methods in terms of analytical performance, easiness, cost and adequacy to the analysis of each class was carried out. The emergence of this kind of multi-class analytical methodologies greatly increases throughput and reduces cost, while avoiding the complexity and redundancy of single-chemical class determinations.

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

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 2400rpm to 3600rpm 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.

Biosynthesis and Conformational Properties of the Irregular Sesquiterpenoids Isothapsadiene and β-Isothapsenol

A carbocation cyclization/rearrangement mechanism for the biosynthesis of isothapsadiene and β-isothapsenol is shown to be energetically viable on the basis of density functional theory (DFT) calculations. In addition, for both isothapsadiene and β-isothapsenol, variable-temperature NMR experiments reveal two equilibrium conformers that undergo hindered exchange. The identities of these conformers, which are related by a chair-flip, are confirmed by DFT calculations on their structures, energies, 1H and 13C chemical shifts, and interconversion pathways.

Shelf Life of Extra Virgin Olive Oil and Its Prediction Models

Extra virgin olive oil (EVOO), with high unsaturation degree (oleic acid, linoleic acid, and linolenic acid), is prone to oxidation during production and storage even with the presence of abundant antioxidants (e.g., phenolic compounds, alpha-tocopherol, and chlorophyll). The level of oxidation degradation is greatly affected by the EVOO chemical composition (free fatty acids, saturated and unsaturated fat ratio, total phenol content, etc.) and storage conditions (packaging material, oxygen, temperature, and light). With the increasing demand on qualitative acceptability and food safety of an EVOO product, consumers rely heavily on “shelf life” as a good indicator. Hence, it is critical for olive oil producers to provide accurate and practical information on shelf-life prediction. This review analyzes ten shelf-life prediction models that used various parameters and approaches for model establishment. Due to the complexity of chemical interactions between oil phase and environment under real-time storage and rapid accelerated testing conditions, further investigation is needed to scrutinize and minimize the discrepancies between real-time shelf life and predicted shelf life of EVOO products.