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

Abstract

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.

Keywords: horticultural commodities; industrial applications; metabolic engineering; volatile organic compounds.

Figure 1

A volatile diversity of important fruits, vegetables, and flowers.

Figure 2

A visual representation of plant volatiles used in plant biological interaction, pharmaceuticals, cosmetics, the food and flavor industry, and biofuels. Biological interactions include both below- and above-ground interactions. Plant volatiles play an important role in multiple plant off-springs and lifespan by attracting pollinators and mediating various interactions between plants and their surroundings.

Figure 3

Terpenoids biosynthetic pathways and potential target points for large-scale genetic modification of products. Terpenoids are synthesized via mevalonic acid (MVA) and methylerythritol phosphate (MEP) pathways. The MEP pathway occurs in plastids and begins with pyruvate and GA-3P condensation and proceeds through a series of reactions to yield hemiterpenes, monoterpenes, and sesquiterpenes; the MVA pathway, on the other hand, begins with acetyl-CoA condensation and proceeds through a series of chemical reactions that stretch the cytosol, peroxisomes, and endoplasmic reticulum to yield monoterpenes and sesquiterpenes. Abbreviations: GA3P, Glyceraldehyde 3-phosphate; DMAPP, dimethylallyl diphosphate; IPP, isopentenyl diphosphate; TPS, Terpene synthase; FPP, farnesyl diphosphate; GPP, geranyl diphosphate; GGPP, geranyl geranyl diphosphate; ACoA, acetyl-CoA; ER, endoplasmic reticulum; Per, peroxisome; NG sequencing, Next generation sequencing.