Nutritional and Volatile Characterisation of Milk Inoculated with Thermo-Tolerant Lactobacillus bulgaricus through Adaptive Laboratory Evolution

In this study, thermo-tolerant strain of Lactobacillus bulgaricus (L. bulgaricus) was developed using gradual increase in temperature to induce Adaptive Laboratory Evolution (ALE). Viable colony count of 1.87 ± 0.98 log cfu/mL was achieved at 52 °C, using MRS agar supplemented with 2% lactose. Changes in bacteria morphology were discovered, from rod (control) to filament (52 °C) to cocci after frozen storage (−80 °C). When milk was inoculated with thermo-tolerant L. bulgaricus, lactic acid production was absent, leaving pH at 6.84 ± 0.13. This has caused weakening of the protein network, resulting in high whey separation and lower water-holding capacity (37.1 ± 0.35%) compared to the control (98.10 ± 0.60%). Significantly higher proteolytic activity was observed through free amino acids analysis by LC-MS. Arginine and methionine (237.24 ± 5.94 and 98.83 ± 1.78 µg/100 g, respectively) were found to be 115- and 275-fold higher than the control, contributing to changing the aroma similar to cheese. Further volatile analysis through SPME-GC-MS has confirmed significant increase in cheese-aroma volatiles compared to the control, with increase in diacetyl formation. Further work on DNA profiling, metabolomics and peptidomics will help to answer mechanisms behind the observed changes made in the study.

Data Statistics in Volatile Analysis by Accurate HS-SPME-GC/MS Measurement and Calculation

The volatile flavor compound in oil is an important indicator of quality which is widely used in the industry to assess the commercial value of oil. The volatile compounds of moringa seed oil were investigated by HS-SPME-GC/MS. The results showed that 52 volatile compounds were identified in moringa seed oil, including 12 hydrocarbons (20.66%),3 acids (23.99%),8 alcohols (8.28%),2 esters (2.61%),8 aldehydes (14.58%),2 ketones (0.82%),7 phenols (6.25%) and 10 heterocyclics (8.74%). Due to the low sensory threshold and high relatively content of aldehydes, aldehydes is one of the mainly factors to affect the flavor of moringa seed oil.

PSVI-27 Relationship of volatile compounds and consumer sensory traits from New Zealand grass-fed and American grain-fed beef strip loins varying in marbling level and wet aging time

Cattle diet, marbling and wet aging can affect eating quality and consumer preference of beef. The objective of this study was to assess the relationship of cooked volatile compounds and consumer sensory traits of New Zealand grass-fed strip loin steaks in comparison to US grain-fed strip loin steaks from five different USDA quality grades, wet-aged for 7, 21 and 42 days. Beef strip loins (n = 200; 20 per USDA quality grade/fed cattle type) representing five USDA quality grades (USDA Prime, Top Choice, Low Choice, Select and Standard) and two fed cattle types (New Zealand grass-finished and US grain-finished) were used. Steaks were cooked to a target internal temperature of 71°C and served to consumer panelists (n = 600; 120 per five different cities in the US). Volatile analysis (n = 600) was performed on cooked samples, and quantitation was conducted by an internal standard calibration with authentic standards. Statistical analyses were conducted using the FACTOR procedure of SAS. A principle component analysis (PCA) showed relationships of volatile compounds, treatments, and consumer ratings. PC1 explained 17.17% of the variation and PC2 explained 10.96% of the variation. Consumer flavor liking was most closely associated with ethanol and treatments grass and grain Prime aged 42d. The majority of the alcohols and n-aldehydes were associated with the 7d grain treatments including grain Top Choice, Low Choice and Select. The Maillard derived compounds were grouped together and most associated with grass Top Choice 42d and the consumer attributes. Methional was closest to many grass treatments including grass Top Choice 7d, Low Choice 7d, Standard 7d, Prime 7d and Standard 21d. Although associations were evident between volatile compounds and consumer sensory attributes, they were not strongly related.

Comparison of Automated Extraction Techniques for Volatile Analysis of Whole Milk Powder

Volatile profiling of whole milk powder is valuable for obtaining information on product quality, adulteration, legislation, shelf life, and aroma. For routine analysis, automated solventless volatile extraction techniques are favored due their simplicity and versatility, however no single extraction technique can provide a complete volatile profile due to inherent chemical bias. This study was undertaken to compare and contrast the performance of headspace solid phase microextraction, thermal desorption, and HiSorb (a sorptive extraction technique in both headspace and direct immersion modes) for the volatile analysis of whole milk powder by gas chromatography mass spectrometry. Overall, 85 unique volatiles were recovered and identified, with 80 extracted and identified using a non-polar gas chromatography column, compared to 54 extracted, and identified using a polar gas chromatography column. The impact of salting out was minimal in comparison to gas chromatography column polarity and the differences between the extraction techniques. HiSorb extracted the most and greatest abundance of volatiles, but was heavily influenced by the number and volume of lactones extracted in comparison to the other techniques. HiSorb extracted significantly more volatiles by direct immersion than by headspace. The differences in volatile selectivity was evident between the techniques and highlights the importance of using multiple extraction techniques in order to obtain a more complete volatile profile. This study provides valuable information on the volatile composition of whole milk powder and on differences between extraction techniques under different conditions, which can be extrapolated to other food and beverages.

Identifying volatile in vitro biomarkers for oral bacteria with proton-transfer-reaction mass spectrometry and gas chromatography–mass spectrometry

We have measured the volatile fingerprints of four pathogenic oral bacteria connected to periodontal disease and dental abscess: Porphyromonas gingivalis (three separate strains), Prevotella intermedia, Prevotella nigrescens and Tannerella forsythia. Volatile fingerprints were measured in vitro from the headspace gas of the bacteria cultured on agar. Concrete identification of new and previously reported bacterial volatiles were performed by a combination of solid phase microextraction (SPME) and offline gas chromatography–mass spectrometry (GC–MS). We also studied the effect of the reduced electric field strength (E/N) on the fragmentation patterns of bacterial volatiles in online proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS). We aimed to discover possible new biomarkers for the studied oral bacteria, as well as to validate the combination of GC–MS and PTR-MS for volatile analysis. Some of the most promising compounds produced include: 1-Methyl-1,2,3,4-tetrahydroisoquinoline (1MeTIQ), indole, and a cascade of sulphur compounds, such as methanethiol, dimethyl disulphide (DMDS) and dimethyl trisulphide (DMTS). We also found that several compounds, especially alcohols, aldehydes and esters, fragment significantly with the PTR-MS method, when high E/N values are used. We conclude that the studied oral bacteria can be separated by their volatile fingerprints in vitro, which could have importance in clinical and laboratory environments. In addition, using softer ionization conditions can improve the performance of the PTR-MS method in the volatile analysis of certain compounds.

Seeing the Forest through the (Phylogenetic) Trees: Functional Characterisation of Grapevine Terpene Synthase (VviTPS) Paralogues and Orthologues

Gene families involved in specialised metabolism play a key role in a myriad of ecophysiological and biochemical functions. The Vitis vinifera sesquiterpene synthases represent the largest subfamily of grapevine terpene synthase (VviTPS) genes and are important volatile metabolites for wine flavour and aroma, as well as ecophysiological interactions. The functional characterisation of VviTPS genes is complicated by a reliance on a single reference genome that greatly underrepresents this large gene family, exacerbated by extensive duplications and paralogy. The recent release of multiple phased diploid grapevine genomes, as well as extensive whole-genome resequencing efforts, provide a wealth of new sequence information that can be utilised to overcome the limitations of the reference genome. A large cluster of sesquiterpene synthases, localised to chromosome 18, was explored by means of comparative sequence analyses using the publicly available grapevine reference genome, three PacBio phased diploid genomes and whole-genome resequencing data from multiple genotypes. Two genes, VviTPS04 and -10, were identified as putative paralogues and/or allelic variants. Subsequent gene isolation from multiple grapevine genotypes and characterisation by means of a heterologous in planta expression and volatile analysis resulted in the identification of genotype-specific structural variations and polymorphisms that impact the gene function. These results present novel insight into how grapevine domestication likely shaped the VviTPS landscape to result in genotype-specific functions.

Characterization of the Aroma Profile and Main Key Odorants of Espresso Coffee

Espresso coffee (EC) is a common coffee preparation technique that nowadays is broadly widespread all over the globe. Its popularity is in part attributed to the intense aroma and pleasant flavor. Many researchers have studied and reviewed the aroma of the coffee, but there is a lack of specific review focused on EC aroma profile even if it is intensively investigated. Thus, the objective of the current review was to summarize the aroma profile of EC and how different preparation variables can affect EC flavor. Moreover, a collection of diverse analytical procedures for volatile analysis was also reported. The findings of this survey showed that the volatile fraction of EC is extremely complex, but just some compounds are responsible for the characteristic aroma of the coffee, such as some aldehyde, ketones, furanones, furans, sulfur compounds, pyrazines, etc. In addition, during preparation, some variables, e.g., temperature and pressure of water, granulometry of the coffee particle, and brew ratio, can also modify the aroma profile of this beverage, and therefore its quality. A better understanding of the aroma fraction of EC and how the preparation variables should be adjusted according to desired EC would assist coffee workers in obtaining a higher quality product.

Egyptian kishk as a fortificant: Impact on the quality of biscuit

Introduction. Biscuit is a mass-consumption product worldwide. As biscuit contains low amount of protein, it can be fortified with protein-containing raw materials. In the present work, we fortified biscuit with kishk, an Egyptian dairy product, and evaluated changes in its physicochemical properties and volatile compounds. Study objects and methods. We analyzed biscuit from wheat flour (control sample) and biscuit form wheat flour with 10, 20, 30, 40, and 50% of kishk (experimental samples). The experiments were carried out by using standard methods. Results and discussion. The fortified biscuit samples showed higher lightness (L*) values than control. The antioxidant activity in the biscuit increased with the increasing amount of kishk. Aldehydes were the main volatile compounds in all the biscuit samples, followed by sulfur-containing compounds and alcohols. The predominant aldehyde was benzldehyde. However, kishk in amounts more than 20% affected adversely the aroma, taste and texture, as well as volatile compounds of the biscuits. Both the control and fortified with kishk biscuits contained an increased amount of total phenolic compounds. Based on sensory evaluation and volatile analysis, the most acceptable amount of kishk for fortification of biscuit was 10%. Conclusion. Fortification of biscuit with Egyptian kishk enhanced its protein, fat and fiber, as well as antioxidant activity at all levels of fortification with no significant effect on appearance and color. Further studies are needed to evaluate storage conditions and shelf life of biscuits with kishk.

Cytokinin but not gibberellin application had major impact on the phenylpropanoid pathway in grape

Cytokinin and gibberellic acid (GA) are growth regulators used to increase berry size in seedless grapes and it is of interest to understand their effects on the phenylpropanoid pathway and on ripening processes. GA3 and synthetic cytokinin forchlorfenuron (N-(2-chloro-4-pyridyl)-N′-phenylurea, CPPU) and their combination were applied to 6 mm diameter fruitlets of ‘Sable Seedless’, and berries were sampled 51 and 70 days (d) following application. All treatments increased berry size and delayed sugar accumulation and acid degradation with a stronger effect of CPPU. CPPU, but not GA, reduced berry color and the levels of anthocyanins. While CPPU reduced the levels of anthocyanins by more than 50%, the combined treatment of GA+CPPU reduced the levels by about 25% at 51 d. CPPU treatment had minor effects on flavonols content but increased the levels of monomeric flavan-3-ols by more than two-fold. Phloroglucinol analysis using HPLC showed that proanthocyanidin content was significantly increased by CPPU, whereas mean degree of polymerization was reduced from 26 to 19. Volatile analysis by GC-MS showed changes in composition with CPPU or GA treatment with potential impact on flavor. RNA-seq analysis showed that GA had a minor overall effect on the transcriptome whereas CPPU had pronounced effects on gene expression at both 51 and 70 d. Comparing the control and CPPU at similar Brix of ca. 19.7°, a reduced expression of stilbene synthases (STSs) including their regulators MYB14 and MYB15, and other phenylpropanoid-related genes was observed in CPPU-treated grapes. Overall, our study shows that CPPU had a major influence on the phenylpropanoid pathway and affected multiple ripening-related processes.