Aroma Components in Horticultural Crops: Chemical Diversity and Usage of Metabolic Engineering for Industrial Applications

Plants produce an incredible variety of volatile organic compounds (VOCs) that assist the interactions with their environment, such as attracting pollinating insects and seed dispersers and defense against herbivores, pathogens, and parasites. Furthermore, VOCs have a significant economic impact on crop quality, as well as the beverage, food, perfume, cosmetics and pharmaceuticals industries. These VOCs are mainly classified as terpenoids, benzenoids/phenylpropanes, and fatty acid derivates. Fruits and vegetables are rich in minerals, vitamins, antioxidants, and dietary fiber, while aroma compounds play a major role in flavor and quality management of these horticultural commodities. Subtle shifts in aroma compounds can dramatically alter the flavor and texture of fruits and vegetables, altering their consumer appeal. Rapid innovations in -omics techniques have led to the isolation of genes encoding enzymes involved in the biosynthesis of several volatiles, which has aided to our comprehension of the regulatory molecular pathways involved in VOC production. The present review focuses on the significance of aroma volatiles to the flavor and aroma profile of horticultural crops and addresses the industrial applications of plant-derived volatile terpenoids, particularly in food and beverages, pharmaceuticals, cosmetics, and biofuel industries. Additionally, the methodological constraints and complexities that limit the transition from gene selection to host organisms and from laboratories to practical implementation are discussed, along with metabolic engineering's potential for enhancing terpenoids volatile production at the industrial level.

One-step fabrication of alkali-acid modified three-dimensional magnetic biochar for the determination of pesticides in pigment-rich vegetables

Magnetic biochar was successfully synthesized via a one-step method through simultaneous activation and magnetization with alkali-acid modified citrus peel as the raw material, which could effectively penetrate interfering substances. The characterization analysis showed that the magnetic biochar exhibited high graphitic degree, higher specific surface area and smaller pore diameter, which resulted in superior adsorption performance. The magnetic biochar was used as an adsorbent for the cleanup and extraction of 22 pesticides (consisting of insecticides, fungicides and herbicides) from vegetables and the quantitative detection was completed by gas chromatography-mass spectrometry (GC-MS). The Plackett-Burman experimental design (PBD), central composite design (CCD) and response surface methodology (RSM) were employed to identify significant factors and optimal experimental conditions. Under optimal conditions, the methodological linearity was in the range of 1-100 μg kg-1 with the coefficients of determination ranging from 0.9969-0.9999, while the limits of detection (LODs) and limits of quantification (LOQs) were 0.31-0.91 μg kg-1 and 1.03-3.05 μg kg-1, respectively. The recoveries of the analytes from spiked samples were in the range of 78.1-112.5%. It was confirmed that the method established by using magnetic graphitic biochar as the adsorbent is an efficient pretreatment procedure and could be successfully applied for analysis of food safety.

Activation of grapefruit derived biochar by its peel extracts and its performance for tetracycline removal

A novel adsorbent derived from grapefruit peel (GP) based biochar (GPBC) was synthesized by combined carbonization of GP and subsequent activation by GP extracts. Compared to biochar without extracts activation, the technique granted GPBC-20 (with 1:20 of solid-solution ratio) more abundant surface functional groups, which exerts the adsorbent superior performance for tetracycline (TC) adsorption (37.92 mg/g v.s. 16.64 mg/g). The adsorption kinetics, isotherms and thermodynamics models were further used to evaluate the adsorption behavior of GPBC. The enhanced adsorption was analyzed by characterization of fresh and used GPBC, revealing that the adsorption mechanism was comprised of pore filling, charge interaction and chemical bonding. The comprehensive investigation of using agricultural waste extracts as activator to prepare its raw materials-based adsorbents may be of great significance for enhanced resource utilization.

Returning to Nature for the Design of Sorptive Phases in Solid-Phase Microextraction

Green analytical chemistry principles aim to minimize the negative impact of analytical procedures in the environment, which can be considered both at close (to ensure the safety of the analysts) and global (to conserve our natural resources) levels. These principles suggest, among other guidelines, the reduction/minimization of the sample treatment and the use of renewable sources when possible. The first aspect is largely fulfilled by microextraction, which is considered to be among the greenest sample treatment techniques. The second consideration is attainable if natural products are used as raw materials for the preparation of new extraction phases. This strategy is in line with the change in our production system, which is being gradually moved from a linear model (take–make–dispose) to a circular one (including reusing and recycling as key terms). This article reviews the potential of natural products as sorbents in extraction and microextraction techniques from the synergic perspectives of two research groups working on the topic. The article covers the use of unmodified natural materials and the modified ones (although the latter has a less green character) to draw a general picture of the usefulness of the materials.

Cost-efficient magnetic nanoporous carbon derived from citrus peel for the selective adsorption of seven insecticides

A magnetic solid-phase extraction adsorbent that consisted of citrus peel-derived nanoporous carbon and silica-coated Fe₃ O₄ microspheres (C/SiO₂ @Fe₃ O₄ ) was successfully fabricated by co-precipitation. As a modifier for magnetic microspheres, citrus peel-derived nanoporous carbon was not only economical and renewable for its raw material, but exerted enormous nanosized pore structure, which could directly influence the type of adsorbed analytes. The C/SiO₂ @Fe₃ O₄ also possessed the advantages of Fe₃ O₄ microspheres like superparamagnetism, which could be easily separated magnetically after adsorption. Integrating the superior of biomass-derived nanoporous carbon and Fe₃ O₄ microspheres, the as-prepared C/SiO₂ @Fe₃ O₄ showed high extraction efficiency for target analytes. The obtained material was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and the Brunauer-Emmett-Teller method, which demonstrated that C/SiO₂ @Fe₃ O₄ was successfully synthesized. Under the optimal conditions, the adsorbent was selected for the selective adsorption of seven insecticides before gas chromatography with mass spectrometry detection, and good linearity was obtained in the concentration range of 2-200 μg/kg with the correlation coefficient ranging from 0.9952 to 0.9997. The limits of detection were in the range of 0.03-0.39 μg/kg. The proposed method has been successfully applied to the enrichment and detection of seven insecticides in real vegetable samples.

Analytical method for metabolites involved in biosynthesis of plant volatile compounds

The progress in the successful techniques used for studying metabolites involved in the metabolic routes of plant volatiles is summarized.