Analysis of grapefruit sulphur volatiles using SPME and pulsed flame photometric detection

Citrus juice off-flavor during different processing and storage: Review of odorants, formation pathways, and analytical techniques

As the most widespread juice produced and consumed globally, citrus juice (mandarin juice, orange juice, and grapefruit juice) is appreciated for its attractive and distinct aroma. While the decrease of characteristic aroma-active compounds and the formation of off-flavor compounds are easy to occur in processing and storage conditions. This review provides a comprehensive literature of recent research and discovery on citrus juice off-flavor, primarily focusing on off-flavor compounds induced during processing and storage (i.e., thermal, storage, light, oxygen, package, fruit maturity, diseases, centrifugal pretreatment, and debittering process), formation pathways (i.e., terpene acid-catalyzed hydration, caramelization reaction, Maillard reaction, Strecker degradation, and other oxidative degradation) of the off-flavor compounds, effective inhibitor pathway to off-flavor (i.e., electrical treatments, high pressure processing, microwave processing, ultrasound processing, and chemical treatment), as well as odor assessment techniques based on molecular sensory science. The possible precursors (terpenes, sulfur-containing amino acids, carbohydrates, carotenoids, vitamins, and phenolic acids) of citrus juice off-flavor are listed and are also proposed. This review intends to unravel the regularities of aroma variations and even off-flavor formation of citrus juice during processing and storage. Future aroma analysis techniques will evolve toward a colorimetric sensor array for odor visualization to obtain a "marker" of off-flavor in citrus juice.

Porphyra yezoensis Sauces Fermented With Lactic Acid Bacteria: Fermentation Properties, Flavor Profile, and Evaluation of Antioxidant Capacity in vitro

The demand for roasted seaweed sandwich (Porphyra yezoensis) product has risen in recent years. The product slicing process has created a huge number of scraps that are not utilized effectively. Three lactic acid bacteria (LAB) strains were used to ferment P. yezoensis sauces in this study, including Lactobacillus fermentum, Lactobacillus casei, Streptococcus thermophilus, and the mixed strains (1:1:1, v/v). The fermentation characteristics, antioxidant capacity in vitro, sensory properties, and flavoring substances of fermented P. yezoensis sauces were analyzed. After 21 days of fermentation, all LAB strains grew well in the P. yezoensis sauces, with protease activity increased to 6.6, 9.24, 5.06, and 5.5 U/mL, respectively. Also, the flavors of P. yezoensis sauces fermented with L. casei and L. fermentum were satisfactory. On this premise, gas chromatography-mass spectrometry (GC-MS) was used to investigate the changes in gustatory compounds in P. yezoensis sauces fermented with L. casei and L. fermentum. In general, 42 and 41 volatile flavor chemicals were identified after the fermentation of L. casei and L. fermentum. Furthermore, the fermented P. yezoensis sauce possessed greater DPPH scavenging activity and ferric-reducing ability power than the unfermented P. yezoensis. Overall, the flavor and taste of P. yezoensis sauce fermented by L. casei was superior.

Occurrence of Marine Ingredients in Fragrance: Update on the State of Knowledge

The fragrance field of perfumes has attracted considerable scientific, industrial, cultural, and civilizational interest. The marine odor is characterized by the specific smell of sea breeze, seashore, algae, and oyster, among others. Marine odor is a more recent fragrance and is considered as one of the green and modern fragrances. The smells reproducing the marine environment are described due to their content of Calone 1951 (7-methyl-2H-1,5-benzodioxepin-3(4H)-one), which is a synthetic compound. In addition to the synthetic group of benzodioxepanes, such as Calone 51 and its derivatives, three other groups of chemical compounds seem to represent the marine smell. The first group includes the polyunsaturated cyclic ((+)-Dictyopterene A) and acyclic (giffordene) hydrocarbons, acting as pheromones. The second group corresponds to polyunsaturated aldehydes, such as the (Z,Z)-3,6-nonadienal, (E,Z)-2,6-nonadienal, which are most likely derived from the degradation of polyunsaturated fatty acids. The third group is represented by small molecules such as sulfur compounds and halogenated phenols which are regarded as the main flavor compounds of many types of seafood. This review exposes, most notably, the knowledge state on the occurrence of marine ingredients in fragrance. We also provide a detailed discussion on several aspects of essential oils, which are the most natural ingredients from various marine sources used in fragrance and cosmetics, including synthetic and natural marine ingredients.

Identification of Light-Induced Key Off-Flavors in Ponkan Mandarin Juice Using MDGC-MS/O and GC-MS/PFPD

Light-induced off-flavor compounds in Ponkan mandarin juice were investigated during its shelf-life by headspace solid-phase microextraction multidimensional gas chromatography-mass spectrometry/olfactometry (MDGC-MS/O) and a GC-MS/pulsed flame photometric detector (GC-MS/PFPD). A total of 34 aroma-active compounds with flavor dilution (FD) factors from 2 to 128 were tentatively identified by aroma extract dilution analysis-MDGC-MS/O. Among them, a light-induced off-flavor compound with a high FD factor, methional (cooked potato), was positively identified in the Ponkan mandarin juice at the end of the shelf-life. In addition, 11 volatile sulfur compounds (VSCs), including 6 screened shelf-markers (variable identification, VID > 0.80), were identified in Ponkan mandarin juice by a sulfur detector (PFPD). Four VSCs exhibited odor activity values exceeding 1. Three VSCs (methanethiol, dimethyl trisulfide, and methional) were confirmed as key light-induced off-flavor compounds in Ponkan mandarin juice based on addition/omission experiments. Furthermore, light irradiation accelerated the degradation of sulfur precursors (methionine and MMS) and the formation of these VSCs leading to an increase in off-flavor intensity.

Determination of exogenous prohibited flavour compounds added in coffee using gas chromatography triple quadrupole tandem massspectrometry and gas chromatography/combustion/isotope ratio mass spectrometry

An analytical method based on gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC-MS/MS) was developed for the simultaneous determination of exogenous prohibited flavour compounds in coffee samples. In addition, gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) was developed to determine the origin of the founded prohibited flavour compound, N-methylpyrrole-2-carboxaldehyde (NMPCA). The good selectivity and sensitivity achieved in multiple reactions monitoring (MRM) mode allowed satisfactory confirmation and quantitation for the flavour compounds. The limits of detection (LODs) and limits of quantitation (LOQs) of these compounds were in the range of 0.0005-5.0 µg/kg and 0.002-16.0 µg/kg, respectively. The coffee samples were extracted with simultaneous distillation extraction (SDE) and NMPCA was analysed on a GC/C/IRMS system. The δ¹³C values of endogenous NMPCA in coffee beans were within a range of -35.0‰ to -31.1‰, whereas exogenous NMPCA was the range from -27.9‰ to -23.9‰. The validation results revealed that the GC-MS/MS method was sensitive and reliable, and the origin of NMPCA can be distinguished by GC/C/IRMS. Finally, this method was successfully applied to coffee samples analysis and NMPCA was found in coffee samples.

Outgoing and potential trends of composition, health benefits, juice production and waste management of the multi-faceted Grapefruit Citrus Χ paradisi: A comprehensive review for maximizing its value

Grapefruit (GF) Citrus Χ paradisi Macfad (F. Rutaceae) is one of the major citrus fruits that encompass a myriad of bioactive chemicals and most unique among citrus fruits. Nevertheless, no study has yet to assess comprehensively its multitudinous constituents, health benefits, and valuable waste products. Hereto, the present review provides an updated comprehensive review on the different aspects of GF, its juice production, waste valorization, enhancement of its byproducts quality, and compared to other citrus fruits. Grapefruit uniqueness among other citrus fruits stands from its unique taste, flavor, and underlying complex chemical composition. Despite limonene abundance in peel oil and grapefruit juice (GFJ) aroma, nootkatone and sulfur compounds are the key determinants of its flavor, whereas flavanones contribute to its bitter taste and in conjunction with limonoids. Different postharvest treatments and juice processing are reviewed and in context to its influence on final product quality and or biological effects. Flavanones, furanocoumarins, and limonoids appear as the most prominent in GF drug interactions affecting its metabolism and or excretion. Valorization of GF peel is overviewed for its utilization as biosrobent, its oil in aromatherapy, limonene as antimicrobial or in cosmetics, fruit pectin for bioethanol production, or as biosorbent, and peel phenolics biotransformation. The present review capitalizes on all of the aforementioned aspects in GF and further explore novel aspects of its juice quality presenting the full potential of this valued multi-faceted citrus fruit.

Characterization of Odor-Active Volatiles in Hawthorn Puree Using Thermal Desorption System Coupled to Gas Chromatography-Mass Spectrometry-Olfactometry and GC-Flame Photometric Detector

The volatile compounds in hawthorn puree obtained from three cultivars (Y1, Crataegus pinnatifida Bunge cv. "Waibahong", Y2, Crataegus pinnatifida Bunge cv. "Damianqiu", and Y3, Crataegus pinnatifida Bunge cv. "Dajinxing") were analyzed by the thermal desorption system coupled to gas chromatography-mass spectrometry-olfactometry and GC-flame photometric detector. In the samples of Y1, Y2, and Y3, 40, 42, and 42 odor-active compounds were, respectively, identified by olfactometry. Methyl 2-methylbutanoate, methyl hexanoate, hexyl isobutanoate, methional, heptanal, and ( Z)-3-hexenyl acetate contributed largely to the characteristic aroma of the three samples. Additionally, the odor activity value (OAV) was used to determine the main compounds and 3-mercaptohexyl acetate (OAV: 10-18), 3-mercapto-2-methylpentanal (OAV: 4-7), methyl 2-methylbutanoate (OAV: 9-21), methyl hexanoate (OAV: 8-16), and 2-pentyl acetate (OAV: 5-12) were considered as the important contributors to the aroma of hawthorn samples.

Characterization of the Major Odor-Active Compounds in Dry Jujube Cultivars by Application of Gas Chromatography-Olfactometry and Odor Activity Value

The volatile compounds of jujube ( Ziziphus jujube Mill.) puree obtained from three cultivars, 'Jinsixiaozao' (Y1), 'Youzao' (Y2), and 'Yuzao' (Y3), were analyzed by gas chromatography-olfactometry (GC-O), gas chromatography-mass spectrometry, gas chromatography-flame photometric detection, and a nitrogen phosphorus detector. The results showed that a total of 37, 37, and 35 odor-active compounds were identified by GC-O in samples of Y1, Y2, and Y3, respectively. In addition, the odor activity value (OAV) was used to determine the important compounds. The results demonstrated that hexanal (OAV of 39-85), ( E)-2-octenal (OAV of 32-70), β-damascenone (OAV of 14-49), ethyl hexanoate (OAV of 22-39), 3-mercaptohexyl acetate (OAV of 17-24), and 2,5-dimethylpyrazine (OAV of 17-22) were key odor-active compounds. It is of great significance to develop high-grade jujube food by determining key odor-active compounds. Furthermore, four volatiles (hexanal, 1-octen-3-ol, 3-mercapohexyl acetate, and benzaldehyde) reduced the overall threshold value by 2.36, 1.01, 1.34, and 1.19, respectively.

Volatile sulfur compounds in tropical fruits

Global production and demand for tropical fruits continues to grow each year as consumers are enticed by the exotic flavors and potential health benefits that these fruits possess. Volatile sulfur compounds (VSCs) are often responsible for the juicy, fresh aroma of tropical fruits. This poses a challenge for analytical chemists to identify these compounds as most often VSCs are found at low concentrations in most tropical fruits. The aim of this review is to discuss the extraction methods, enrichment techniques, and instrumentation utilized to identify and quantify VSCs in natural products. This will be followed by a discussion of the VSCs reported in tropical and subtropical fruits, with particular attention to the odor and taste attributes of each compound. Finally, the biogenesis and enzymatic formation of specific VSCs in tropical fruits will be highlighted along with the contribution each possesses to the aroma of their respective fruit.

Using headspace solid-phase microextraction for comparison of volatile sulphur compounds of fresh plants belonging to families Alliaceae and Brassicaceae

In this study, an optimisation of extraction of sulphur volatile compounds (SVCs) has been performed using Central Composite Design. The conditions of the highest amount of eluated peaks and total peaks area have been treated. Factors such as coating of fiber for SPME (Solid Phase Microextraction), extraction temperature and extraction time have been optimised. The SVCs have shown the optimal extraction using a DVB/CAR/PDMS (divinylbenzene/carboxen/polydimethylsiloxane) fiber at 73 °C during 50 min. Furthermore, a pre-incubation step lasting 20 min at the extraction temperature has been used. In total, 12 samples have been investigated at the mentioned optimal conditions, eight from the Alliaceae and four from the Brassicaceae family. The highest number of SVCs (24) has been identified in the sample of chive. The most frequently identified compound found in 11 of 12 samples has been dimethyl trisulphide.

Identification of muscadine wine sulfur volatiles: pectinase versus skin-contact maceration

Muscadine grapes ( Vitis rotundifolia ) are widely grown in the southern United States, as the more common Vitis vinifera cannot be cultivated due to Pierce's disease. There is interest to determine if certain cultivars can be used for good-quality wine production. This study compared the effect of pectolytic enzyme pretreatment with conventional skin-contact fermentation on Muscadine (Noble, Vitis rotundifolia ) wine major volatiles, aroma active volatiles, and volatile sulfur compounds (VSCs). Volatile composition, aroma activity, and VSCs in the initial juice and wine samples after 3 years were determined by gas chromatography in combination with mass spectrometry (GC-MS), olfactory detection (GC-O), and pulsed flame photometric detection (GC-PFPD). Forty-three nonethanol MS volatiles were common to all samples. Total ion chromatogram (TIC) MS peak area increased 91% in the skin-contact wines from the initial juice but only 24% in the enzyme-treated wine. Thirty-one VSCs were detected. Twenty-four sulfur volatiles were identified by matching their retention characteristics on polar and nonpolar columns with those of standards or MS spectrum matches. Six of these (sulfur dioxide, 1-propanethiol, 3-mercapto-2-pentanone, 3-mercapto-2-butanone, 2,8-epithio-cis-p-menthane, and 1-p-menthene-8-thiol) were reported for the first time in muscadine wine. Five additional VSCs were tentatively identified by matching standardized retention values with literature values, and two remain unidentified. Total sulfur peak areas increased 400% in the skin-contact wine and 560% in the enzyme-treated wine compared to the initial juice. There were 42 aroma-active volatiles in the initial juice, 48 in the skin-contact wine, and 66 in the enzyme-treated wine. Eleven aroma-active volatiles in the skin-contact wine and 16 aroma volatiles in the enzyme-treated wine appear to be due to sulfur volatiles. Pectolytic enzyme-treated wines contained less total volatiles but more sulfur and aroma-active volatiles than the traditional skin-contact wine.