Fruits produce a range of volatile compounds that make up their characteristic aromas and contribute to their flavor. Fruit volatile compounds are mainly comprised of esters, alcohols, aldehydes, ketones, lactones, terpenoids and apocarotenoids. Many factors affect volatile composition, including the genetic makeup, degree of maturity, environmental conditions, postharvest handling and storage. There are several pathways involved in volatile biosynthesis starting from lipids, amino acids, terpenoids and carotenoids. Once the basic skeletons are produced via these pathways, the diversity of volatiles is achieved via additional modification reactions such as acylation, methylation, oxidation/reduction and cyclic ring closure. In this paper, we review the composition of fruit aroma, the characteristic aroma compounds of several representative fruits, the factors affecting aroma volatile, and the biosynthetic pathways of volatile aroma compounds. We anticipate that this review would provide some critical information for profound research on fruit aroma components and their manipulation during development and storage.

https://www.mdpi.com/1420-3049/18/7/8200/pdf

Advances in Fruit Aroma Volatile Research

The cytoplasmic membrane of a prokaryotic cell consists of a lipid bilayer or a monolayer that shields the cellular content from the environment. In addition, the membrane contains proteins that are responsible for transport of proteins and metabolites as well as for signalling and energy transduction. Maintenance of the functionality of the membrane during changing environmental conditions relies on the cell’s potential to rapidly adjust the lipid composition of its membrane. Despite the fundamental chemical differences between bacterial ester lipids and archaeal ether lipids, both types are functional under a wide range of environmental conditions. We here provide an overview of archaeal and bacterial strategies of changing the lipid compositions of their membranes. Some molecular adjustments are unique for archaea or bacteria, whereas others are shared between the two domains. Strikingly, shared adjustments were predominantly observed near the growth boundaries of bacteria. Here, we demonstrate that the presence of membrane spanning ether-lipids and methyl branches shows a striking relationship with the growth boundaries of archaea and bacteria.

/pdf/adaptations-of-archaeal-and-bacterial-membranes-to-2zanp9gawq.pdf

Adaptations of archaeal and bacterial membranes to variations in temperature, pH and pressure

Factors influencing levels of phytochemicals in selected fruit and vegetables during pre- and post-harvest food processing operations

The essential oil fraction obtained from the rind of Citrus spp. is rich in chemical compounds of interest for the food and perfume industries, and therefore has been extensively studied during the last decades. In this manuscript, we provide a comprehensive review of the volatile composition of this oil fraction and rind extracts for the 10 most studied Citrus species: C. sinensis (sweet orange), C. reticulata (mandarin), C. paradisi (grapefruit), C. grandis (pummelo), C. limon (lemon), C. medica (citron), C. aurantifolia (lime), C. aurantium (bitter orange), C. bergamia (bergamot orange), and C. junos (yuzu). Forty-nine volatile organic compounds have been reported in all 10 species, most of them terpenoid (90%), although about half of the volatile compounds identified in Citrus peel are non-terpenoid. Over 400 volatiles of different chemical nature have been exclusively described in only one of these species and some of them could be useful as species biomarkers. A hierarchical cluster analysis based on volatile composition arranges these Citrus species in three clusters which essentially mirrors those obtained with genetic information. The first cluster is comprised by C. reticulata, C. grandis, C. sinensis, C. paradisi and C. aurantium, and is mainly characterized by the presence of a larger abundance of non-terpenoid ester and aldehyde compounds than in the other species reviewed. The second cluster is comprised by C. junos, C. medica, C. aurantifolia, and C. bergamia, and is characterized by the prevalence of mono- and sesquiterpene hydrocarbons. Finally, C. limon shows a particular volatile profile with some sulfur monoterpenoids and non-terpenoid esters and aldehydes as part of its main differential peculiarities. A systematic description of the rind volatile composition in each of the species is provided together with a general comparison with those in leaves and blossoms. Additionally, the most widely used techniques for the extraction and analysis of volatile Citrus compounds are also described.

/pdf/volatile-compounds-in-citrus-essential-oils-a-comprehensive-4gfttpkn2f.pdf

Volatile Compounds in Citrus Essential Oils: A Comprehensive Review

Effects of carboxymethyl cellulose and chitosan bilayer edible coating on postharvest quality of citrus fruit.

During the last decade there has been a continuous rise in consumption of fresh easy-to-peel mandarins. However, mandarins are much more perishable than other citrus fruit, mainly due to rapid deterioration in sensory acceptability after harvest. In the current review we discuss the biochemical components involved in forming the unique flavor of mandarins, and how postharvest storage operations influence taste and aroma and consequently consumer sensory acceptability. What we perceive as mandarin flavor is actually the combination of basic taste, aroma and mouth-feel. The taste of mandarins is principally governed by the levels of sugars and acids in the juice sacs and the relative ratios among them, whereas the aroma of mandarins is derived from a mixture of different aroma volatiles, including alcohols, aldehydes, ketones, terpenes/hydrocarbons and esters. During postharvest storage and marketing there is a gradual decrease in mandarin sensory acceptability, which has been attributed to decreases in acidity and typical mandarin flavor, paralleling an accumulation of off-flavor. Biochemical analysis of volatile and non-volatile constituents in mandarin juice demonstrated that these changes in sensory acceptability were concomitant with decreases in acidity and content of terpenes and aldehydes, which provide green, piney and citrus aroma on the one hand, and increases in ethanol fermentation metabolism products and esters on the other, which are likely to cause 'overripe' and off-flavors. Overall, we demonstrate the vast importance of the genetic background, maturity stage at harvest, commercial postharvest operation treatments, including curing, degreening and waxing, and storage duration on mandarin sensory quality.

Taste and aroma of fresh and stored mandarins

Morels are edible mushrooms appreciated worldwide for their savory flavor. Morels have been in use in traditional medicine for centuries, due to their health-related benefits, and current research demonstrated their anti-oxidative and anti-inflammatory bioactivities, in addition to immunostimulatory and anti-tumor properties. In spite of the high demand for morels and their increasing economic importance, their cultivation is limited, and they are either used as wild harvested or fermented in culture, for consumption as a functional food and for food-flavoring. Morel's health benefits were attributed mainly to polysaccharides as the active compounds, and to various phytochemicals, mainly phenolic compounds, tocopherols, ascorbic acid and vitamin D. Morel's nutritional composition was reported, including sugar, amino acid, fatty and organic acid and mineral profile. Information regarding Morel's flavor is limited, and while some of their taste attributes have been described, including the role of u...

True morels (Morchella)-nutritional and phytochemical composition, health benefits and flavor: A review.

Importance of storage temperatures in maintaining flavor and quality of mandarins

Does ethylene degreening affect internal quality of citrus fruit

BACKGROUND: Mandarins suffer from accumulation of off-flavours after harvest. In this study the sensory quality and aroma profile composition of homogenised segments of untreated (control) and wax-coated ‘Mor’ mandarins after 7 days at 20 °C or 3 or 6 weeks of cold storage at 5 °C were examined.



RESULTS: Fruit taste score decreased during storage and following wax coating, and this was attributed to decreases in sourness and mandarin flavour and accumulation of off-flavours. Aroma profiling identified 31 volatiles that decreased by at least 50% during storage and after waxing and thus may be involved in the observed flavour loss. In contrast, 13 volatiles, mostly belonging to ethanol fermentation and fatty acid and amino acid catabolism pathways, significantly increased at least twofold and probably contributed to off-flavour enhancement.



CONCLUSION: The results showed that after harvest there was a progressive decrease in sensory quality of ‘Mor’ mandarins. It is proposed that observed decreases in contents of sesqui- and monoterpenes and short-chain oxygenated fatty acids may contribute to the decrease in mandarin flavour, whereas increases in the contents of ethanol fermentation metabolites and derivates of fatty acid and amino acid catabolism are most likely involved in causing the enhanced sensation of off-flavours. Copyright © 2010 Society of Chemical Industry

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Papers

Taste and aroma of fresh and stored mandarins

True morels (Morchella)-nutritional and phytochemical composition, health benefits and flavor: A review.

Importance of storage temperatures in maintaining flavor and quality of mandarins

Does ethylene degreening affect internal quality of citrus fruit

Effects of wax coatings and postharvest storage on sensory quality and aroma volatile composition of 'Mor' mandarins.