Volatile thiols in coffee: A review on their formation, degradation, assessment and influence on coffee sensory quality

Thiols are among the compounds that have the greatest impact on the flavor of coffee. Due to their extremely low odor thresholds, they have a significant sensory impact even at very low concentrations. Thiols are formed during coffee roasting and are described as the key odorants responsible for the typical 'coffee' and 'roasty' odor notes, greatly influencing the sensory characteristics of coffee. They are particularly reactive and prone to oxidation; their rapid depletion after preparation of a coffee brew and during storage of roasted coffee has been associated with sensory quality decrease and coffee going stale. For these reasons, their determination and insight into their formation and degradation mechanisms could help us to preserve the sensory quality of coffee and to modulate its sensory features. Coffee aroma has been widely studied in recent decades, and it has become evident that the role of certain volatile thiols is paramount. Nevertheless, a limited number of studies have specifically addressed this class of compounds, and several aspects have not yet been satisfactorily elucidated. The aim of this review is to provide an overview of the current state on knowledge about coffee thiols, focusing on their occurrence, determination, sensory impact, formation and evolution in roasted and brewed coffee

Thiols in brewed coffee: assessment by fast derivatization and liquid chromatography high resolution mass spectrometry

In the present paper, we present a simple, reliable, selective and sensitive method for the identification and quantification of volatile thiols at trace levels in coffee brews. A simultaneous derivatization/ extraction procedure followed by liquid chromatography electrospray high-resolution mass spectrometry is proposed and adapted to coffee brew matrix, and the performance of the method is evaluated. The linearity, sensitivity, recovery and both the intra-day and inter-day accuracy were all satisfactory. According to established identification criteria, seven target and nine non-target thiols were identified and quantified in coffee brew samples. Several of them are reported here for the first time in coffee brews, and our results are in agreement with previously reported results for coffee powder analyzed using similar analytical approach

Flash Gas Chromatography in Tandem with Chemometrics: A Rapid Screening Tool for Quality Grades of Virgin Olive Oils

This research aims to develop a classification model based on untargeted elaboration of volatile fraction fingerprints of virgin olive oils (n = 331) analyzed by flash gas chromatography to predict the commercial category of samples (extra virgin olive oil, EVOO; virgin olive oil, VOO; lampante olive oil, LOO). The raw data related to volatile profiles were considered as independent variables, while the quality grades provided by sensory assessment were defined as a reference parameter. This data matrix was elaborated using the linear technique partial least squares-discriminant analysis (PLS-DA), applying, in sequence, two sequential classification models with two categories (EVOO vs. no-EVOO followed by VOO vs. LOO and LOO vs. no-LOO followed by VOO vs. EVOO). The results from this large set of samples provide satisfactory percentages of correctly classified samples, ranging from 72% to 85%, in external validation. This confirms the reliability of this approach in rapid screening of quality grades and that it represents a valid solution for supporting sensory panels, increasing the effciency of the controls, and also applicable to the industrial sector

Revealing adulterated olive oils by triacylglycerol screening methods: Beyond the official method

Official control methods to detect olive oil (OO) adulteration fail to provide satisfactory consumer protection. Thus, faster and more sensitive screening tools are needed to increase their effectiveness. Here, the official method for adulterant detection in OO was compared with three untargeted screening methods based on triacylglycerol analysis using high-throughput (FIA-HESI-HRMS; HT-GC-MS; HPLC-RID) and pattern recognition techniques (PLS-DA). They were assayed on a set of genuine and adulterated samples with a high natural variability (n = 143). The sensitivity of the official method was 1 for high linoleic (HL) blends at ≥2 % but only 0.39 for high oleic (HO) blends at ≥5 %, while specificity was 0.96. The sensitivity of the screening methods in external validation was 0.90-0.99 for the detection of HL and 0.82-0.88 for HO blends. Among them, HT-GC-MS offered the highest sensitivity (0.94) and specificity (0.76), proving to be the most suitable screening tool for OO authentication

Geographical authentication of virgin olive oil by GC-MS sesquiterpene hydrocarbon fingerprint: Scaling down to the verification of PDO compliance

Nowadays, 144 Protected Designations of Origin (PDO) and Protected Geographical Indications (PGI) under the EU quality schemes correspond to extra virgin olive oil (EVOO). As endorsed by the EU Food Fraud Network, PDO/PGI EVOOs are particularly vulnerable to fraudulent practices because of their high economic value. For this reason, the present study aims to develop an instrumental tool to assess the compliance of EVOO with PDO label-declaration using a large sample set (n = 350). As a case study, PDOs from Catalonia were used. Therefore, discriminant analysis based on the sesquiterpene hydrocarbon fingerprint determined by HS-SPME-GC-MS achieved to correctly classify an average of 93.6% of samples among the four Catalan PDOs, leaving unassigned the 6% of the total sampling (external validation results for 3 iterations). On the other hand, the proposed strategy allowed discriminating each Catalan PDO from non-PDO samples produced in different geographical areas with an efficiency between 95% and 99%

Chemical markers to distinguish the homoand heterozygous bitter genotype in sweet almond kernels

Bitterness in almonds is controlled by a single gene (Sk dominant for sweet kernel, sk recessive for bitter kernel) and the proportions of the offspring genotypes (SkSk, Sksk, sksk) depend on the progenitors’ genotype. Currently, the latter is deduced after crossing by recording the phenotype of their descendants through kernel tasting. Chemical markers to early identify parental genotypes related to bitter traits can significantly enhance the efficiency of almond breeding programs. On this basis, volatile metabolites related to almond bitterness were investigated by Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry coupled to univariate and multivariate statistics on 244 homo- and heterozygous samples from 42 different cultivars. This study evidenced the association between sweet almonds’ genotype and some volatile metabolites, in particular benzaldehyde, and provided for the first time chemical markers to discriminate between homo- and heterozygous sweet almond genotypes. Furthermore, a multivariate approach based on independent variables was developed to increase the reliability of almond classification. The Partial Least Square-Discriminant Analysis classification model built with selected volatile metabolites that showed discrimination capacity allowed a 98.0% correct classification. The metabolites identified, in particular benzaldehyde, become suitable markers for the early genotype identification in almonds, while a DNA molecular marker is not yet available.info:eu-repo/semantics/publishedVersio

Profiling versus fingerprinting analysis of sesquiterpene hydrocarbons for the geographical authentication of extra virgin olive oils

The verification of the geographical origin of extra virgin (EVOO) and virgin olive oil (VOO) is crucial to protect consumers from misleading information. Despite the large number of studies performed, specific markers are still not available. The present study aims to evaluate sesquiterpene hydrocarbons (SHs) as markers of EVOO geographical origin and to compare the discrimination efficiency of targeted profiling and fingerprinting approaches. A prospective study was carried out on 82 EVOOs from seven countries, analyzed by Headspace Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry (HS-SPME-GC-MS). Classification models were developed by Partial Least Square-Discriminant Analysis (PLS-DA) and internally validated (leave 10%-out crossvalidation). The percentage of correct classification was higher for the fingerprinting (100%) than for the profiling approach (45.5\u2013100%). These results confirm the suitability of SHs as EVOO geographical markers and establish the fingerprinting as the most efficient approach for the treatment of SH analytical data with this purpose up to date

Chemical Markers to Distinguish the Homo- And Heterozygous Bitter Genotype in Sweet Almond Kernels

Bitterness in almonds is controlled by a single gene (Sk dominant for sweet kernel, sk recessive for bitter kernel) and the proportions of the offspring genotypes (SkSk, Sksk, sksk) depend on the progenitors' genotype. Currently, the latter is deduced after crossing by recording the phenotype of their descendants through kernel tasting. Chemical markers to early identify parental genotypes related to bitter traits can significantly enhance the efficiency of almond breeding programs. On this basis, volatile metabolites related to almond bitterness were investigated by Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry coupled to univariate and multivariate statistics on 244 homo- and heterozygous samples from 42 different cultivars. This study evidenced the association between sweet almonds' genotype and some volatile metabolites, in particular benzaldehyde, and provided for the first time chemical markers to discriminate between homo- and heterozygous sweet almond genotypes. Furthermore, a multivariate approach based on independent variables was developed to increase the reliability of almond classification. The Partial Least Square-Discriminant Analysis classification model built with selected volatile metabolites that showed discrimination capacity allowed a 98.0% correct classification. The metabolites identified, in particular benzaldehyde, become suitable markers for the early genotype identification in almonds, while a DNA molecular marker is not yet available

Bio-Protection as an Alternative to Sulphites: Impact on Chemical and Microbial Characteristics of Red Wines

In wine, one method of limiting the addition of sulphites, a harmful and allergenic agent, is bio-protection. This practice consists of the early addition of microorganisms on grape must before fermentation. Non-Saccharomyces yeasts have been proposed as an interesting alternative to sulphite addition. However, scientific data proving the effectiveness of bio-protection remains sparse. This study provides the first analysis of the chemical and microbiological effects of a Metschnikowia pulcherrima strain inoculated at the beginning of the red winemaking process in three wineries as an alternative to sulphiting. Like sulphiting, bio-protection effectively limited the growth of spoilage microbiota and had no influence on the phenolic compounds protecting musts and wine from oxidation. The bio-protection had no effect on the volatile compounds and the sensory differences were dependent on the experimental sites. However, a non-targeted metabolomic analysis by FTICR-MS highlighted a bio-protection signature

Catalan virgin olive oil Protected Designations of Origin: physicochemical and major sensory attributes

Catalonia, located in the northeast of Spain, comprises five extra virgin oliveoil (EVOO) protected designations of origin (PDOs). Despite the proximitybetween them, these PDOs represent unique pedoclimatic conditions andtraditional olive cultivars that are briefly reviewed in the present manuscript.In addition to the compliance with quality standards fixed by productspecifications, EVOOs show singular and distinctive composition and sensoryprofiles. With the aim to describe the characteristics of Catalan EVOOs, theirsensory and analytical traits are reviewed with the support of data collectedbetween 2009 and 2017 in more than 42 milling facilities from the fiveCatalan PDOs, within the frame of official surveys launched by the CatalanGovernment.Practical Applications: A detailed knowledge of the characteristics ofdifferentiated-quality productions will favor their valorization and protection,improving their image and increasing the consumer confidence. For thisreason, studies to objectively define the characteristics of PDO EVOOs areuseful tools to promote this sector