Post-storage changes of volatile compounds in air- and sun-dried raisins with different packaging materials using HS-SPME with GC/MS

Volatile, Microbial, and Sensory Profiles and Consumer Acceptance of Coffee Cascara Kombuchas

Given the substantial world coffee production, tons of coffee fruit cascara rich in bioactive compounds are discarded annually. Using this by-product to produce potentially healthy and acceptable foods is a sustainable practice that aggregates value to coffee production and may help improve people's lives. This study aimed to elaborate kombuchas from coffee cascara tea, evaluate their microbial profile, and monitor the changes in the volatile profile during fermentation, together with sensory attributes and acceptance by consumers from Rio de Janeiro (n = 113). Arabica coffee cascaras from Brazil and Nicaragua were used to make infusions, to which black tea kombucha, a Symbiotic Culture of Bacteria and Yeasts (SCOBY), and sucrose were added. Fermentation of plain black tea kombucha was also monitored for comparison. The volatile profile was analyzed after 0, 3, 6, and 9 days of fermentation via headspace solid phase microextraction GC-MS. A total of 81 compounds were identified considering all beverages, 59 in coffee cascara kombuchas and 59 in the black tea kombucha, with 37 common compounds for both. An increase mainly in acids and esters occurred during fermentation. Despite the similarity to black tea kombucha, some aldehydes, esters, alcohols, and ketones in coffee cascara kombucha were not identified in black tea kombucha. Potential impact compounds in CC were linalool, decanal, nonanal, octanal, dodecanal, ethanol, 2-ethylhexanol, ethyl acetate, ethyl butyrate, ethyl acetate, β-damascenone, γ-nonalactone, linalool oxide, phenylethyl alcohol, geranyl acetone, phenylacetaldehyde, isoamyl alcohol, acetic acid, octanoic acid, isovaleric acid, ethyl isobutyrate, ethyl hexanoate, and limonene. The mean acceptance scores for cascara kombuchas varied between 5.7 ± 0.53 and 7.4 ± 0.53 on a nine-point hedonic scale, with coffee cascara from three-day Nicaragua kombucha showing the highest score, associated with sweetness and berry, honey, woody, and herbal aromas and flavors. The present results indicate that coffee cascara is a promising by-product for elaboration of fermented beverages, exhibiting exotic and singular fingerprinting that can be explored for applications in the food industry.

EBR and JA regulate aroma substance biosynthesis in 'Ruidu Hongyu' grapevine berries by transcriptome and metabolite combined analysis

Volatile compounds including terpenes, aldehyde, phenol, and alcohol are significantly contributed floral and fruity aromas to the Muscat variety. 'Ruidu Hongyu' grapevine is one of the newly developed grape varieties, and cultivation of this variety has been extended across China due to unique quality traits and taste. In this study, HS-SPME/GC-MS and transcriptome sequencing analysis were performed to evaluate the impact of exogenous 2,4-epibrassinolide (EBR), jasmonic acid (JA), and their signaling inhibitors brassinazole (Brz)/sodium diethyldithiocarbamate (DIECA) on the biosynthesis of aroma substances in 'Ruidu Hongyu' grapevine. According to the results, exogenous BR and JA promoted the accumulation of various aroma substances, including hexenal, 2-hexenal, nerol oxide, vanillin, hotrienol, terpineol, neral, nerol, geraniol, and geranic acid. After EBR and JA treatments, most of the genes responsible for terpene, aldehyde, and alcohol biosynthesis expressed at a higher level than the CK group. Relatively, EBR treatment could not only promote endogenous BR biosynthesis and metabolism but also elevate BR signaling transduction. JA treatment contributed to endogenous JA and MeJA accumulation, as well. Through transcriptome sequencing, a total of 3043, 903, 1470, and 607 DEGs were identified in JA vs. JD, JA vs. CK, BR vs. CK, and BR vs. Brz, respectively. There were more DEGs under both EBR and JA treatments at late fruit ripening stages. The findings of this study increase our understanding regarding aroma substances biosynthesis and endogenous BR/JA metabolism in response to exogenous EBR and JA signals.

Interrogating Raisin Associated Unsaturated Fatty Acid Derived Volatile Compounds Using HS-SPME with GC-MS

This study proposed to investigate the generation mechanism of raisins-derived volatile compounds during unsaturated fatty acids oxidation (UFAO) using a mixture of fatty acids (FAs) and four individual FA at different time intervals (0, 4, 8, 12, 16, and 20 days; 60 °C). During the sun-drying of 'Thompson Seedless' grapes (Vitis vinifera L.), a total of 39 UFAO-derived volatiles were characterized by the GC-MS. Firstly a pH value of 4.2 was optimized to proceed with a raisin drying-like UFAO model reaction. Afterward, GC-MS quantification revealed 45 UFAO-derived volatiles, and the maximum numbers of compounds were identified in the interaction of all FAs (39) following linoleic acid (29), erucic acid (27), oleic acid (25), and linolenic acid (27). Pentanoic acid, (E,E)-2,4-octadienal, and n-decanoic acid were only quantified in all FAs, linoleic acid, and erucic acid, respectively. This study showed that all FAs reactions were found to be responsible for the generation of a greater number of UFAO-derived volatiles with higher concentrations.

Indigenous Lactococcus lactis with Probiotic Properties: Evaluation of Wet, Thermally- and Freeze-Dried Raisins as Supports for Cell Immobilization, Viability and Aromatic Profile in Fresh Curd Cheese

Indigenous Lactococcus lactis enriched raisins were incorporated in fresh curd cheese in wet, thermally dried, and freeze-dried form to produce a novel probiotic dairy product. Symbiotic cheese represents a rising trend in the global market. The viability of L. lactis cells was assessed in the cheeses during storage at 4 °C for 14 days and the effect of the added enriched raisins on physicochemical parameters, microbiological characteristics, and sugar content, aromatic profile, and sensory acceptance of cheeses were evaluated. Immobilized L. lactis cells maintained viability at necessary levels (>6 log cfu/g) during storage and significantly increased the acceptability of cheese. The addition of raisins enhanced the volatile profile of cheeses with 2-furanmethanol, 1-octanol, 3-methylbutanal, 2-methylbutanal, 2-furancarboxaldehyde, 1-(2-furanyl)-ethanone, 5-methyl-2-furancarboxaldehyde. The obtained results are encouraging for the production of novel fresh cheeses with improved sensorial and nutritional characteristics on industrial and/or small industrial scale.

Vinegar Production from Corinthian Currants Finishing Side-Stream: Development and Comparison of Methods Based on Immobilized Acetic Acid Bacteria

Fruit wastes and side-streams can be used for vinegar production to create added value for the agri-food sector and enhance farmer incomes and local economies. In this study, methods for vinegar production by wild and selected acetic acid bacteria (the quick starter Acetobacter aceti and the acid-resistant Komagataeibacter europaeus), free (FC) and immobilized (IC) on a natural cellulosic carrier, are proposed using sweet wine made from the industrial finishing side-stream (FSS) of Corinthian currants as raw material. The results showed all cultures can produce vinegar with 46.65 ± 5.43 g/L acidity, from sweet FSS wine containing 5.08 ± 1.19% alcohol. The effect of immobilization was more obvious in the case of the selected culture, presenting better acetification efficiency, both fresh and after cold storage for 2 months. The vinegars had an antioxidant capacity of 263.5 ± 8.4 and 277.1 ± 6.7 mg/L (as ascorbic acid) and phenolic content 333.1 ± 12.0 and 222.2 ± 2.9 mg/L (as gallic acid) (for FC and IC, respectively). They also had a rich volatilome (140 compounds identified by SPME GC-MS), with higher percentages of esters identified in vinegars made by IC. The results are encouraging for vinegar production with IC of a mixed A. aceti and K. europaeus culture.

Comparison of the microbial community and flavor compounds in fermented mandarin fish (Siniperca chuatsi): Three typical types of Chinese fermented mandarin fish products

Fermented mandarin fish have been receiving attention from consumers due to their nutritional value and specific flavor. Microbial diversity in fermented mandarin fish has an important impact on their flavor and quality. However, little is known about the microbiome and the differences among different products. In this study, the bacterial profiles and flavor compounds in three typical fermented mandarin fish products were investigated and compared, and a correlation network was used to explore the potential relationship between microorganisms and flavor. Bacterial community analysis demonstrated clear differences in microbiota among the HF-, MF-, and OF-fermented mandarin fish products. Psychrilyobacter, Fusobacterium, and Vibrio were the most dominant in the HF-, MF-, and OF-fermented products, respectively. In addition, 14, 12, and 4 flavor substances (relative odor activity value, ROAV ≥ 1) were detected in the muscles from the central dorsal and ventral sides of the three samples, respectively. Several bacteria correlated with the production of important flavor compounds, and three genera (Arcobacter, Psychrilyobacter, and Shewanella) were the primary microorganisms contributing to more than six characteristic flavor compounds in fermented mandarin fish products. Therefore, the study's systematic method allows identificating important microbes and characteristic volatile flavor compounds in fermented mandarin fish and provides new insights into the relationship between microorganisms and flavor.

Drying Treatments Change the Composition of Aromatic Compounds from Fresh to Dried Centennial Seedless Grapes

Raisin aroma is a vital sensory characteristic that determines consumers’ acceptance. Volatile organic compounds (VOCs) in fresh grapes, air-dried (AD), pre-treated air-dried (PAD), sun-dried (SD), and pre-treated sun-dried (PSD) raisins were analyzed, with 99 and 77 free- and bound-form compounds identified in centennial seedless grapes, respectively. The hexenal, (E)-2-hexenal, 1-hexanol, ethyl alcohol, and ethyl acetate in free-form while benzyl alcohol, β-damascenone, gerenic acid in bound-form were the leading compounds. Overall, the concentration of aldehydes, alcohols, esters, acids, terpenoids, ketones, benzene, and phenols were abundant in fresh grapes but pyrazine and furan were identified in raisin. Out of 99 VOCs, 30 compounds had an odour active value above 1. The intensity of green, floral, and fruity aromas were quite higher in fresh grapes followed by AD-raisins, PAD-raisins, SD-raisins, and PSD-raisins. The intense roasted aroma was found in SD-raisins due to 2,6-diethylpyrazine and 3-ethyl-2,5-dimethylpyrazine. Among raisins, the concentration of unsaturated fatty acid oxidized and Maillard reaction volatiles were higher in SD-raisins and mainly contributed green, fruity and floral, and roasted aromas, respectively.

Characterization of volatile compounds in differently coloured Chenopodium quinoa seeds before and after cooking by headspace-gas chromatography-ion mobility spectrometry

Aroma is an important feature of quinoa that influences consumer preferences. Differently coloured quinoa seeds exhibit diverse nutritional characteristics; however, their aromatic profile differences are poorly investigated. The volatile components of 11 quinoa samples were characterized by headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS). A total of 120 peaks were detected, with 61 compounds identified. White quinoa liberated a high concentration of volatiles with grass (n-hexanol) and green ((E)-2-octenal, (E)-2-heptenal, etc.) aromas before and after cooking, respectively. Raw flaxen samples uniquely released a caramel compound (cyclotene) and exhibited several sweet and caramel volatiles (decanal, 5-methyl-furfural, and 2-furfural) after cooking. Additionally, cooked black quinoa exerted more fruity substances (methyl hexanoate and phenylacetaldehyde). Orthogonal partial least square discriminant analysis clearly distinguished the samples before and after cooking and differentiated the seeds into different colours. The results confirm the potential of HS-GC-IMS to evaluate volatiles in quinoa and are meaningful for quinoa consumption.

Combining solid dispersion-based spray drying with cyclodextrin to improve the functionality and mitigate the beany odor of pea protein isolate

The beany flavor of pea protein limits its application in the food industry. This study aimed at addressing this problem by combining the advantages of solid-based spray drying technique and the ability of cyclodextrins (CD) to entrap volatiles. Pea protein isolates (PPI) was extracted by alkaline extraction-isoelectric precipitation, followed by co-spray drying with CD. The resulted PPI-CD showed no major structure changes. HS-SPME-GC-MS coupled to untargeted metabolomics successfully identified 23 aroma compounds that represent the different odorants among PPI-control, physically mixed PPI-CD, and co-spray dried PPI-CD samples. Heat map analysis also showed a remarkable beany odor mitigation effect upon the addition of CD, which was further proved to be due to CD entrapping aroma compounds during spray drying. In the meantime, the functional attributes of PPI-CD were not adversely impacted by the addition of CD.

Characterization and Biological Activities of Seed Oil Extracted from Berberis dasystachya Maxim. by the Supercritical Carbon Dioxide Extraction Method

Characterization of the structure and pharmacological activity of Berberis dasystachya Maxim., a traditional Tibetan medicinal and edible fruit, has not yet been reported. In this study, central composite design (CCD) combined with response surface methodology (RSM) was applied to optimize the extraction conditions of B. dasystachya oil (BDSO) using the supercritical carbon dioxide (SC-CO₂) extraction method, and the results were compared with those obtained by the petroleum ether extraction (PEE) method. The chemical characteristics of BDSO were analyzed, and its antioxidant activity and in vitro cellular viability were studied by DPPH, ABTS, reducing power assay, and MTT assay. The results showed that the maximum yield of 12.54 ± 0.56 g/100 g was obtained at the optimal extraction conditions, which were: pressure, 25.00 MPa; temperature 59.03 °C; and CO₂ flow rate, 2.25 SL/min. The Gas chromatography (GC) analysis results showed that BDSO extracted by the SC-CO₂ method had higher contents of unsaturated fatty acids (85.62%) and polyunsaturated fatty acids (57.90%) than that extracted by the PEE method. The gas chromatography used in conjunction with ion mobility spectrometry (GC-IMS) results showed that the main volatile compounds in BDSO were aldehydes and esters. BDSO also exhibited antioxidant ability in a dose-dependent manner. Moreover, normal and cancer cells incubated with BDSO had survival rates of more than 85%, which indicates that BDSO is not cytotoxic. Based on these results, the BDSO extracted by the SC-CO₂ method could potentially be used in other applications, e.g., those that involve using berries of B. dasystachya.

Impact of Drying Method on the Evaluation of Fatty Acids and Their Derived Volatile Compounds in 'Thompson Seedless' Raisins

Air- and sun-dried raisins from Thompson Seedless (TS) grapes were analyzed under GC/MS to evaluate fatty acids (FAs) and their derived volatile compounds, coming from unsaturated fatty acids oxidation. A total of 16 FAs were identified in TS raisins, including 10 saturated fatty acids (SFAs) and 6 unsaturated fatty acids (USFAs). The contents of C18:0, C15:0, and C16:0 among SFAs and C18:3, C18:2 and C18:1 in USFAs were significantly higher. Furthermore, USFAs such as C16:1 and C20:1 were only identified in air-dried raisins. The principal component analysis showed the increased content of FAs and FA-derived compounds were in air-dried and sun-dried raisins, respectively. Among FA-derived compounds, 2-pentyl furan, 3-octen-2-one, 1-hexanol and heptanoic acid were more potent. This study shows that air-drying is more favorable for the production of fatty acids (SFAs and USFAs), whereas sun-drying is more advantageous in terms of fatty acid-derived volatiles.

The Actual and Potential Aroma of Winemaking Grapes

This review intends to rationalize the knowledge related to the aroma of grapes and to the aroma of wine with specific origin in molecules formed in grapes. The actual flavor of grapes is formed by the few free aroma molecules already found in the pulp and in the skin, plus by those aroma molecules quickly formed by enzymatic/catalytic reactions. The review covers key aroma components of aromatic grapes, raisins and raisinized grapes, and the aroma components responsible from green and vegetal notes. This knowledge is used to explain the flavor properties of neutral grapes. The aroma potential of grape is the consequence of five different systems/pools of specific aroma precursors that during fermentation and/or aging, release wine varietal aroma. In total, 27 relevant wine aroma compounds can be considered that proceed from grape specific precursors. Some of them are immediately formed during fermentation, while some others require long aging time to accumulate. Precursors are glycosides, glutathionyl and cysteinyl conjugates, and other non-volatile molecules.

Changes in the Volatile Components of Candied Kumquats in Different Processing Methodologies with Headspace-Gas Chromatography-Ion Mobility Spectrometry

The effects of two different processing methods on the volatile components of candied kumquats were investigated via headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS). The characteristic volatile fingerprints of fresh kumquats (FKs), vacuum sugaring osmosis combined with hot-air drying kumquats (VS-ADKs), and atmospheric pressure sugaring osmosis combined with hot-air drying kumquats (AS-ADKs) were established using 3D topographic plots. From the fingerprints, 40 signal peaks for 22 compounds were confirmed and quantified in all types of kumquats, namely, two terpenes, four esters, seven aldehydes, three ketones, and six alcohols. 3-Pentanone was identified as the major component of FKs; followed by 1-hexanol and the Z-3-hexen-1-ol dimer. The hexanal dimer, 2-hexen-1-ol, and the ethyl acetate dimer were the major markers of VS-ADKs. Benzaldehyde and furfurol were the prominent constituent parts of AS-ADKs. Compared with that in FKs, the pentanal and dimethyl ketone contents of VS-ADKs and AS-ADKs exhibited a dramatic increase (p < 0.05). By contrast, the change in ethanol dimer tended to decrease (p < 0.05). Principal component analysis (PCA) clearly showed that the samples, which were distributed in a separate space could be well-distinguished. Furthermore, the similarity of different processed kumquats and their corresponding volatile components was demonstrated via heat map clustering analysis. The results confirmed the potential of HS-GC-IMS-based approaches to evaluate processed kumquats with various volatile profiles.