A comparative study on aromatic profiles of strawberry vinegars obtained using different conditions in the production process

Aroma characterisation of Liu-pao tea based on volatile fingerprint and aroma wheel using SBSE-GC-MS

Liu-pao tea (LPT) has unique aroma characteristics, and is a special microbial fermented tea produced using dark raw tea (LPM) as its raw material. In this study, stir bar sorptive extraction (SBSE) combined with gas chromatography-mass spectrometry (GC-MS) was applied to investigate the volatiles of 16 LPTs and 6 LPMs. Moreover, variations in volatile profiles between LPTs and LPMs were explored. Results showed that a total of 132 volatile compounds were identified from LPTs. The volatile fingerprint was constructed with a similarity ranged from 0.85 to 0.99. Furthermore, twenty-six aroma compounds were selected to depict the molecular aroma wheel of LPT. Multivariate statistical analysis revealed that the contents of 24 aroma compounds changed significantly (P < 0.05) when LPMs were processed into LPTs. These results reveal the volatile profiles of LPTs and aroma composition changes during microbial fermentation process, which might provide chemical basis of the aroma quality of LPT.

Identifying aroma-active compounds in coffee-flavored dairy beverages

Coffee aroma is a complex mixture of volatile compounds. This study characterized the important aroma-active compounds associated with consumer liking in formulated coffee-flavored dairy beverages. Nine coffee-flavored dairy beverages were formulated: low fat-low coffee; medium fat-low coffee; high fat-low coffee; low fat-medium coffee; medium fat-medium coffee; high fat-medium coffee; low fat-high coffee; medium fat-high coffee; and high fat-high coffee. Regular coffee consumers, (n = 231) used a nine-point hedonic scale to rate acceptance of aroma. Volatile compounds were extracted by head space-solid phase micro-extraction (HS-SPME) and analyzed by gas chromatography-mass spectrometry-olfactometry (GC-MS-O) using a modified frequency (MF) approach. Fifty-two aroma-active compounds were detected. Thirty-one aroma-active compounds were considered important compounds with MF-value ≥ 50%. The total number of aroma-active compounds and their intensity were affected because of fat and coffee concentration. Partial least squares regression (PLSR) was performed to determine the relationship between aroma-active compounds and liking. PLSR analysis identified three groups of compounds regarding liking. Twenty-five compounds were associated with positive liking, for example, 2-(methylsulfanylmethyl) furan (coffee like). Sixteen compounds were negatively associated with liking, for example, 2-methoxyphenol (bacon, medicine like). Eleven detected compounds had no association with liking, for example, butane-2,3-dione (butter, fruit like). Practical Application: The result of this study may be applied to formulate coffee-flavored dairy beverages to maximize consumer acceptance and aroma-liking. This study suggested too low coffee concentration is not desirable. Too much fat affects aroma release and/or alters the characteristic coffee flavor which negatively affects consumer acceptance.

Biotechnological Processes in Fruit Vinegar Production

The production of fruit vinegars as a way of making use of fruit by-products is an option widely used by the food industry, since surplus or second quality fruit can be used without compromising the quality of the final product. The acetic nature of vinegars and its subsequent impact on the organoleptic properties of the final product allows almost any type of fruit to be used for its elaboration. A growing number of scientific research studies are being carried out on this matrix, and they are revealing the importance of controlling the processes involved in vinegar elaboration. Thus, in this review, we will deal with the incidence of technological and biotechnological processes on the elaboration of fruit vinegars other than grapes. The preparation and production of the juice for the elaboration of the vinegar by means of different procedures is an essential step for the final quality of the product, among which crushing or pressing are the most employed. The different conditions and processing methods of both alcoholic and acetic fermentation also affect significantly the final characteristics of the vinegar produced. For the alcoholic fermentation, the choice between spontaneous or inoculated procedure, together with the microorganisms present in the process, have special relevance. For the acetic fermentation, the type of acetification system employed (surface or submerged) is one of the most influential factors for the final physicochemical properties of fruit vinegars. Some promising research lines regarding fruit vinegar production are the use of commercial initiators to start the acetic fermentation, the use of thermotolerant bacteria that would allow acetic fermentation to be carried out at higher temperatures, or the use of innovative technologies such as high hydrostatic pressure, ultrasound, microwaves, pulsed electric fields, and so on, to obtain high-quality fruit vinegars.

Vinegar production from <i>Theobroma grandiflorum</i> SCHUM (cupuassu)

<abstract> <p>The tropical fruit cupuassu comes from <italic>Theobroma grandiflorum</italic> (SCHUM), a close relative of cocoa. Cupuassu has a rich yet delicate flavour profile with notes of chocolate, pineapple, passion fruit and other fruits. Here, we produced a cupuassu-fruit wine using a <italic>Saccharomyces cerevisiae</italic> inoculum (and univariate analysis to determine conditions for optimum ethanol production) and then fermented this wine to produce a delicate and unique cupuassu vinegar using acid-acid bacteria. The cupuassu wine was produced by fermentation of juice chaptalized with sucrose, with a final ethanol concentration of 10% (v/v). Acetic-acid fermentations were carried out in both a bubble-column reactor and a mechanically non-aerated reactor (high-surface reactor), producing final concentrations of 4.5 and 3.3% (w/v) acetic acid, respectively. The ethanol- and acetic-acid yields obtained were comparable to those of other fruit wines and fruit vinegars. The cupuassu vinegar retained the rich flavor profile of the cupuassu. We believe that the production of flavorsome products from local plants can have benefits for conservation by promoting ecologically sustainable agriculture and may contribute to cultural identity of Amazon people.</p> </abstract>

Insight into the volatile profiles of four types of dark teas obtained from the same dark raw tea material

Various dark teas are quite different in their volatile profiles, mainly due to the huge differences in the phytochemical profiles of dark raw tea and the diverse post-fermentation processing technologies. In this study, gas chromatography-mass spectrometry (GC-MS), qualitative GC-olfactometry (GC-O), and enantioselective GC-MS coupled with multivariate analysis were applied to characterise the volatile profiles of various dark teas obtained from the same dark raw tea material. A total of 159 volatile compounds were identified by stir bar sorptive extraction (SBSE) combined with GC-MS, and 49 odour-active compounds were identified. Moreover, microbial fermentation could greatly influence the distribution of volatile enantiomers in tea, and six pairs of enantiomers showed great diversity of enantiomeric ratios among various dark teas. These results suggest that post-fermentation processing technologies significantly affect the volatile profiles of various dark teas and provide a theoretical basis for the processing and quality control of dark tea products.

Characterization and Comparison of Aroma Profiles and Aroma-Active Compounds between Traditional and Modern Sichuan Vinegars by Molecular Sensory Science

Aroma profiles and aroma-active compounds of Sichuan vinegar, which is one of the four famous vinegars in China, were systemically analyzed by solvent-assisted flavor evaporation-gas chromatography-mass spectrometry (SAFE-GC-MS) and gas chromatography-olfactometry (GC-O). In addition, descriptive profile analysis, aroma reconstitution, and omission test were used to evaluate and compare the Sichuan modern vinegar (SMV) and Sichuan traditional vinegar (STV). A total of 99 volatile compounds were tentatively identified from the neutral and acidic fractions of both samples. Among them, 77 compounds were positively identified after comparison with their corresponding standards. Forty-two aroma-active compounds were characterized with flavor dilution (FD) factors from 1 to 6561 by aroma extract dilution assay (AEDA)-GC-O, with the highest for 2-hydroxy-3-butanone, butyrolactone, furan-2-carbaldehyde, acetic acid, and 3-oxobutan-2-yl acetate in both STV and SMV samples. Among them, 10 were identified for the first time in vinegar. Moreover, 40 aroma-active compounds were quantitatively determined, and 26 compounds exhibited their odor activity values (OAVs) larger than 1. The reconstituted solutions showed similar aroma profiles to the original samples in their characteristic aromas in terms of fruity, sweet, roasty, spicy, and woody notes but had slight differences in nutty and herbal notes.

Characterization of the aroma profile and key odorants of the Spanish PDO wine vinegars

The aroma profiles of Spanish wine vinegars with Protected Designation of Origin (PDO) were described and compared for the first time by gas chromatography-mass spectrometry-olfactometry (GC-MS-O), odor-active values (OAVs) and quantitative descriptive analysis (QDA). Vinagre de Jerez Reserva (JRE) showed higher percentage of 'grassy-vegetal' impact odorants, while 'spicy' compounds highlighted the Pedro Ximénez category (JPX). Vinagre de Montilla-Moriles Reserva (MRE) had 'buttery-lactic' impact odorants, while 'empyreumatic' and 'sweet' aromas stood out for Pedro Ximénez category (MPX). Vinagre de Condado de Huelva Reserva (CRE) showed a stronger percentage of 'chemical' impact odorants. The key odorants were ethyl propionate, ethyl octanoate, propanoic acid and 4-ethylphenol for JRE, diacetyl and methional/furfural for JPX, acetoin for MRE, ethyl phenylacetate and vanillin for MPX and acetaldehyde diethyl acetal, isobutyl acetate, ethyl isovalerate and guaiacol for CRE. A good relation among the impact odorants and the sensory descriptors was observed.

Sensorial, antioxidant and antimicrobial evaluation of vinegars from surpluses of physalis (Physalis pubescens L.) and red pitahaya (Hylocereus monacanthus)

BACKGROUND

To reduce postharvest losses, substandard fruit and agricultural surpluses can productively be used as raw material for vinegar production. The present study aimed to prepare vinegars from surpluses of physalis (Physalis pubescens L.) and red pitahaya (Hylocereus monacanthus) and then evaluate their sensorial characteristics, antimicrobial activities, total phenolic content (TPC) and total antioxidant capacity by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzo thiazoline-6-sulfonic acid) methods.

RESULTS

Two vinegars were produced by submerged fermentation using physalis and red pitahaya fruits surpluses. Physalis and red pitahaya vinegars had 47 and 45 g L^-1 acetic acid, respectively, and both vinegars contained approximately 1 g L^-1 ethanol. Both vinegars displayed antimicrobial activity against Escherichia coli, Listeria monocytogenes, Staphylococcus aureus and Salmonella enteritidis. The TPC of physalis and red pitahaya vinegar was 0.5638 and 0.3656 g L^-1 g gallic acid L^-1 for physalis and red pitahaya, respectively. A similar antioxidant activity was detected in both the wines and vinegars. The sensorial analysis revealed that the consumers 'like moderately' each vinegar, and citric aroma was noted in the physalis vinegar.

CONCLUSION

In the present study, vinegars with sensorial characteristics approved by consumers were developed using fruit surpluses, adding value through a new product making use of a simple methodology that is both inexpensive and demonstrates a good yield. © 2018 Society of Chemical Industry.

FTIR spectroscopy for prediction of quality parameters and antimicrobial activity of commercial vinegars with chemometrics

BACKGROUND

The aim of this study was to discriminate between commercial apple, rice, balsamic, red-wine, rose, white-wine, grape, and pomegranate vinegars according to their antimicrobial activities, total phenolic contents (TPC), antioxidant activities, and color parameters, and to predict the quality characteristics of vinegars using Fourier transform infrared (FTIR) spectroscopy.

RESULTS

Results showed that the highest TPC (3971.43 ± 25.00) was found in balsamic vinegar whereas the lowest TPC was observed in rice vinegar (14.36 ± 0.16). Antioxidant activities of vinegars were correlated with TPC. Grape-based vinegars exhibited higher antimicrobial activity against Staphylococcus aureus (S. aureus), Escherichia coli (E.coli) and Pseudomonas aeruginosa (P.aeruginosa). However, there were no statistically significant differences among vinegars in terms of antimicrobial activities. According to principal component analysis (PCA) and hierarchical cluster analysis (HCA), vinegars were classified into three groups and each group consisted of vinegars from different raw materials. Prediction models were constructed successfully using partial least squares (PLS) considering whole FTIR spectral data.

CONCLUSION

The results indicated that FTIR could be used as a rapid method to estimate the antimicrobial activities, TPC, color and antioxidant activities of vinegars. © 2018 Society of Chemical Industry.

Effect of fermentation modes on nutritional and volatile compounds of Huyou vinegar

Semi-solid static mode was applied to brew Huyou (Citrus changshanensis) vinegar, called HV-SS, and changes of main nutrients, volatile compounds and antioxidant capacity at different brewing stages, i.e. Huyou puree (HP), Huyou wine (HW) and HV-SS, were investigated. Meanwhile, all these parameters of HV-SS and Huyou vinegar brewed by liquid static mode (HV-LS) were compared. The contents of the main nutrients except for vitamin C (Vc) and reducing sugar increased significantly after fermentation from HP to HV-SS. DPPH radical-scavenging capacity and reducing power of HW was the highest and ABTS⁺ scavenging capacity of HV-SS was the highest. Acids, flavonoids, phenolics and Vc jointly played important roles in the antioxidant capacity of HV-SS. Forty-six aroma compounds were detected in HP and alcohols were the principal components (15 alcohols accounted for 46.2%). During HW fermentation, most of the compounds in HP (d-limonene, hexanal, hexanol and 3-hexen-1-ol) were nearly disappeared, and some new alcohols, esters and alkanes were formed, being the abundant compounds in HW and accounting for 62.99%, 18.44% and 10.52% respectively. There were 51 aroma compounds detected in HV-SS and 10 more than those in HV-LS. The types or contents of esters (22.13%), acids (50.49%) and aldehydes (7.33%) in HV-SS were markedly different from those in HP, HW and HV-LS, giving the unique aroma and good flavor to HV-SS. Therefore, semi-solid static fermentation mode was more suitable for brewing Huyou vinegar on the aspect of balancing the nutrients characteristics and flavor compounds formation.

Comparative study of submerged and surface culture acetification process for orange vinegar

BACKGROUND

The two main acetification methodologies generally employed in the production of vinegar (surface and submerged cultures) were studied and compared for the production of orange vinegar. Polyphenols (UPLC/DAD) and volatiles compounds (SBSE-GC/MS) were considered as the main variables in the comparative study. Sensory characteristics of the obtained vinegars were also evaluated.

RESULTS

Seventeen polyphenols and 24 volatile compounds were determined in the samples during both acetification processes. For phenolic compounds, analysis of variance showed significant higher concentrations when surface culture acetification was employed. However, for the majority of volatile compounds higher contents were observed for submerged culture acetification process, and it was also reflected in the sensory analysis, presenting higher scores for the different descriptors. Multivariate statistical analysis such as principal component analysis demonstrated the possibility of discriminating the samples regarding the type of acetification process. Polyphenols such as apigenin derivative or ferulic acid and volatile compounds such as 4-vinylguaiacol, decanoic acid, nootkatone, trans-geraniol, β-citronellol or α-terpineol, among others, were those compounds that contributed more to the discrimination of the samples.

CONCLUSION

The acetification process employed in the production of orange vinegar has been demonstrated to be very significant for the final characteristics of the vinegar obtained. So it must be carefully controlled to obtain high quality products. © 2017 Society of Chemical Industry.

Sampling methods for the study of volatile profile of PDO wine vinegars. A comparison using multivariate data analysis

High-quality wine vinegars have been registered in Spain under protected designation of origin (PDO): "Vinagre de Jerez", "Vinagre de Condado de Huelva" and "Vinagre de Montilla-Moriles". The raw material, production and aging processes determine their quality and their aromatic composition. Vinegar volatile profile is usually analyzed by gas chromatography-mass spectrometry (GC-MS), being necessary a previous extraction step. Thus, three different sampling methods (Headspace solid phase microextraction "HS-SPME", Headspace stir bar sorptive extraction "HSSE" and Dynamic headspace extraction "DHS") were studied for the analysis of the volatile composition of Spanish PDO wine vinegars. Multivariate curve resolution (MCR) was used to solve chromatographic problems, improving the results obtained. Principal component analysis (PCA) showed that not all the sampling methods were equally suitable for the characterization and differentiation between PDOs and categories, being HSSE the technique that made able the best vinegar characterization.

Comparative assessment of software for non-targeted data analysis in the study of volatile fingerprint changes during storage of a strawberry beverage

Five free software packages were compared to assess their utility for the non-targeted study of changes in the volatile profile during the storage of a novel strawberry beverage. AMDIS coupled to Gavin software turned out to be easy to use, required the minimum handling for subsequent data treatment and its results were the most similar to those obtained by manual integration. However, AMDIS coupled to SpectConnect software provided more information for the study of volatile profile changes during the storage of strawberry beverage. During storage, volatile profile changed producing the differentiation among the strawberry beverage stored at different temperatures, and this difference increases as time passes; these results were also supported by PCA. As expected, it seems that cold temperature is the best way of preservation for this product during long time storage. Variable Importance in the Projection (VIP) and correlation scores pointed out four volatile compounds as potential markers for shelf-life of our strawberry beverage: 2-phenylethyl acetate, decanoic acid, γ-decalactone and furfural.

Application of E-tongue, E-nose, and MS-E-nose for discriminating aged vinegars based on taste and aroma profiles

The combined approach of E-senses was undertaken to discriminate the taste and aroma profiles of aged vinegars, including Chinese Shanxi extra aged vinegar (EX, 5-8 years), Japanese black vinegar (BL, 1-5 years), and Italian balsamic vinegar (BA, 8-25 years). The principal component analysis plot for E-tongue revealed that EX, BL, and BA formed individual groups with clear distinctions. The volatile compounds detected in E-nose based on Kovats indices represented that a major component in all vinegars was matched to acetic acid, which showed a strong relationship with the aging period (R=0.8186-0.9998). The discriminant function analysis plot accompanied by the MS-E-nose indicated that more volatiles were produced during prolonged aging in cereal vinegar, whereas the aging process degraded volatile constituents in fruit vinegar. Categorization with respect to aging years was possible using both E-noses. The approach using E-senses indicated a better discrimination for distinguishing the complex sensory information in aged vinegars.