Metabolic Flow of C6 Volatile Compounds From LOX-HPL Pathway Based on Airflow During the Post-harvest Process of Oolong Tea

Aroma is an essential quality indicator of oolong tea, a tea derived from the Camellia sinensis L. plant. Carboxylic 6 (C6) acids and their derivative esters are important components of fatty acid (FA)-derived volatiles in oolong tea. However, the formation and regulation mechanism of C6 acid during postharvest processing of oolong tea remains unclear. To gain better insight into the molecular and biochemical mechanisms of C6 compounds in oolong tea, a combined analysis of alcohol dehydrogenase (ADH) activity, CsADH2 key gene expression, and the FA-derived metabolome during postharvest processing of oolong tea was performed for the first time, complemented by CsHIP (hypoxia-induced protein conserved region) gene expression analysis. Volatile fatty acid derivative (VFAD)-targeted metabolomics analysis using headspace solid-phase microextraction–gas chromatography time-of-flight mass spectrometry (HS-SPEM-GC-TOF-MS) showed that the (Z)-3-hexen-1-ol content increased after each turnover, while the hexanoic acid content showed the opposite trend. The results further showed that both the ADH activity and CsADH gene expression level in oxygen-deficit-turnover tea leaves (ODT) were higher than those of oxygen-turnover tea leaves (OT). The C6-alcohol-derived ester content of OT was significantly higher than that of ODT, while C6-acid-derived ester content showed the opposite trend. Furthermore, the HIP gene family was screened and analyzed, showing that ODT treatment significantly promoted the upregulation of CsHIG4 and CsHIG6 gene expression. These results showed that the formation mechanism of oolong tea aroma quality is mediated by airflow in the lipoxygenase–hydroperoxide lyase (LOX-HPL) pathway, which provided a theoretical reference for future quality control in the postharvest processing of oolong tea.

Increase in Fruity Ester Production during Spine Grape Wine Fermentation by Goal-Directed Amino Acid Supplementation

The aim of this work was to enhance the levels of fruity esters in spine grape (Vitis davidii Foёx) wine by goal-directed amino acid supplementation during fermentation. HPLC and GC-MS monitored the amino acids and fruity esters, respectively, during alcoholic fermentation of spine grape and Cabernet Sauvignon grape. HPLC was also used to determine the extracellular metabolites and precursors involved in the synthesis of fruity esters. Alanine, phenylalanine, and isoleucine levels in spine grape were less than those in Cabernet Sauvignon. Pearson correlation between amino acid profile and fruity ester content in the two systems indicated that deficiencies in alanine, phenylalanine, and isoleucine levels might have limited fruity ester production in spine grape wine. Supplementation of these three amino acids based on their levels in Cabernet Sauvignon significantly increased fruity ester content in spine grape wine. Interestingly, goal-directed amino acid supplementation might have led to changes in the distribution of carbon fluxes, which contributed to the increase in fruity ester production.

Response Factor in GC-FID Methyl Ester Analysis in Several Biodiesels: A Comparative Study of the EN 14103:2011 and ABNT 15764:2015 Methods versus a Proposed GC-FID Procedure for Individual Ester Determination

A gas chromatography method with a flame ionization detector enabled by relative response factor was developed to determine the individual and the total content of esters in biodiesel. This method accounts for different response factors of the detector for a homologous series of esters that may be present in biodiesel. In this way, the determination of the total ester content of a reference sample (100.5%) was done with more accuracy by the proposed procedure (100.2%) than by official analytical methods: EN (74.68%) and ABNT (118.2%). Another advantage of the developed method is the possibility of determining individual ester concentrations, which provides information on several important biodiesel properties such as oxidative stability and cold flow properties. The mean absolute error in the determination of the individual ester content was ca. 1.1%.

Study of the Feasibility of Biodiesel Production, from Vegetable Oils and Catalysts of Seafood Residues, in a Batch Hydrogenation Reaction Unit, Assisted by Microwave and Conventional Heating

In this work, it was proposed to study the feasibility of biodiesel production, from residues of vegetable oils used in domestic activities, employing (CaCO3) shells prepared like calcium oxide (CaO) as catalysts, in a batch reaction unit, on bench scale, installed at IPEN-CNEN/SP. This unit is capable of operating with high pressure hydrogen gas (up to 200bar) and high temperature (up to 500°C, using microwave - MW (2.450MHz, with up to 2kW continuous and 8kW pulsed) and conventional heating – (electric) MC. In the tests, the oil load (mL), type and mass of catalyst, with or without hydrogen gas pressure (bar), temperature (°C), reaction time (h), microwave power (W), the speed of the load (rpm) agitation and the conventional heating were evaluated. The analytical determinations of the samples were carried out by means of density, gas chromatography (GC) and X-ray fluorescence. Data were collected in order to be compared with other methodologies, already used in the literature. The purpose of this work was to analyze the efficiency of the use of these types of catalysts and oils in the production of biodiesel, as an alternative technology. The Ca and CaO contents found in the pink shell, before and after the calcination, were 36.2% and 98.8%, respectively. The best result obtained for the density was 0.875182g/cm3, for the test with 4g of calcined shell catalyst and reaction of 1h. As to the methyl ester content, the highest result was 95.33%, in a test with 4g of catalyst and reaction of 3h. In the non-calcined shell test (22.5g), although the amount of mass used was much larger (5% of the oil mass), the ester content was very low, 2.11%.

Alteration of Biodiesel Properties and Automotive Diesel Engine Performance due to Temperature Variation of the Transesterification Process

This study aimed to examine the effects of transesterification reaction temperature on the biodiesel properties and diesel engine performance. Biodiesel properties evaluated in this work included viscosity, density, and methyl ester content. Meanwhile, the diesel engine performance testing comprised the examination of the engine’s torque and power. The research was conducted in several stages, viz. producing biodiesel from fresh cooking oil with variations in transesterification temperature of 45℃, 55℃, and 65℃; testing the characteristics of biodiesel produced; blending biodiesel with petroleum diesel to result in B30 biodiesel fuel; and testing biodiesel fuel (B30) in diesel-engined vehicles. It was revealed that the higher transesterification temperature led to the lower biodiesel viscosity, the decreasing value of biodiesel density values, and the higher methyl ester content. Furthermore, it was also demonstrated that increase of the transesterification temperature resulted in the higher value of torque and power generated. However, compared to the petroleum diesel fuel (B0), biodiesel fuel (B30) exhibited the lower values of the engine’s torque and power. The highest average values of torque and power of B30 fueled diesel-engine were 108.11 Nm and 43.51 kW, respectively, provided by the biodiesel produced at the transesterification reaction temperature of 65℃.of 65℃.

Properties of Biodiesel Purified by Membrane Technology

Membrane technology is the most effective technology in the process of separation and purification because the separation of components can occur to the molecular level. Therefore the application of membrane technology in the biodiesel production process can provide high-purity biodiesel quality. In this research, the process of separating and refining palm oil biodiesel does not use the washing process, but it uses membrane separation technology. The membrane used is the ceramic ultrafiltration membrane 0.02 µm. The purification process was carried out at temperature 70°C and pressure 12 Psi (0.86 bar), flow rate of 39.53 L/min, circulation time of 3 hours with a feed of 10 L. After purification, an obtained biodiesel has physical properties as follows: Purity level 97.63% mass (total ester content) and 97.02% mass (methyl ester content), kinematic viscosity at 40°C is 5.70 (cSt), density 0.86 (g/cm3), acid number 0.45 (mg KOH/g) and the saponification number 206.45 mg KOH/g. The values ​​of the physicochemical properties have met Indonesian National Standard (SNI).

Study of Thermal and Oxidative Stability of Cottonseed Biodiesel

Biodiesel is a renewable fuel with excellent lubricity and biodegradability. However, its use may be compromised by factors that change its characteristics and occur during production, transportation and/or storage. Some of them are associated with biodiesel stability and can affect vehicle performance. The objective of this work was to analyze the main causes of cottonseed oil biodiesel instability due to the storage process, determining some physicochemical properties as kinematic viscosity, acidity index, refractive index, electrical conductivity as well as ester content, mass of precipitate formed and pH. The acidity and kinematic viscosity of biodiesel from cottonseed oil increase with storage time. The latter suggests the occurrence of a partial oxidation of biodiesel with formation of products that increase its viscosity. Gas chromatography results showed that even after thermo-oxidative treatment, biodiesel samples maintained the minimum ester content required by the ANP (Brazilian National Agency of Petroleum, Natural Gas and Biofuels) and unsaturated bonds tends to be preferentially oxidized over other carbon-carbon bonds. There was no significant influence of light exposure (storage in amber and transparent vials) on the ester content, refractive index and mass of precipitate formed. On the other hand, the latter was influenced by the heating time.