Evaluation of process involved in the production of aromatic compounds in Gram-negative bacteria isolated from vanilla (Vanilla planifolia ex. Andrews) beans

Influence of Traditional Vanilla Curing on Its Physicochemical Properties and Aromatic Profile

Vanilla is native to Mexico and has social-cultural and economic importance. It is sensory characteristics are developed during the curing process, which is associated with the region where it is carried out since the know-how of each locality is involved. In this sense, this work aimed to evaluate the influence of the curing process. Four different processes from four regions (SJA, SLP, CQ and EPM) were considered, taking into account two curing conditions. Additionally, sample control was considered. The moisture content, protein, ether extract, ash and pH were analyzed. The aromatic profile was evaluated by the RATA methodology and liking level. Except for ash content, the process influenced the other physicochemical parameters. The moisture contents of SLP and CQ samples from Period 1, as well as SLP samples from Period 2, comply with the current Mexican Standard. SJA vanilla was "slightly" accepted in both periods, surpassing the control sample. In contrast, the CQ sample was the least preferred. Thirty-five aromatic descriptors were generated. At the sensory level, a clear separation of vanillas was observed according to the type of curing. The attributes described included caramel, dry fruit, fruity, honey, maltol, rancid, sweet, tree bark, vanilla and ashes, which boosted the liking level. On the other hand, the descriptors chemical, moisture, dairy, spicy, wood and lipids had a negative effect, proving that these factors can alter the aromatic balance, giving an unpleasant smell and reducing preference. It was confirmed that the curing process influences physicochemical parameters, the aromatic profile and the liking level. However, it would be necessary to consider other variables.

Evolution of microbial community and the volatilome of fresh-cut chili pepper during storage under different temperature conditions: Correlation of microbiota and volatile organic compounds

The effect of temperature conditions on the evolution of microbial communities and volatile organic compounds (VOCs) in fresh-cut chili peppers during storage was investigated. Results showed that Proteobacteria and Actinobacteriota were the dominant phyla in fresh-cut chili peppers. During storage, bacterial communities changed more dramatically than fungi. Different temperature conditions significantly affected the shift of bacteria at the genus level. At the beginning of storage, Rhodococcus, Pantoea, and Pseudomonas dominated the bacteria. However, on day 8, Pantoea and Enterobacter became the predominant genera at 5 °C and high temperatures (10, 15 °C, dynamic temperature), respectively. No significant variability in bacterial species was observed between different batches. Additionally, 140 VOCs were determined in fresh-cut chili peppers. Twenty-two VOCs were screened and could be recommended as potential spoilage markers. Based on Spearman's correlation analysis results, Enterobacter and Enterococcus were the most positive microorganisms correlated with spoilage markers.

The isolation and identification of Bacillus velezensis ZN-S10 from vanilla (V. planifolia), and the microbial distribution after the curing process

The market value of vanilla beans (Vanilla planifolia) is constantly increasing due to their natural aroma and flavor properties that improve after a curing process, where bacteria colonization plays a critical role. However, a few publications suggest that bacteria play a role in the curing process. Hence, this study aimed to isolate Bacillus sp. that could be used for fermenting V. planifolia while analyzing their role in the curing process. Bacillus velezensis ZN-S10 identified with 16S rRNA sequencing was isolated from conventionally cured V. planifolia beans. A bacteria culture solution of B. velezensis ZN-S10 (1 mL of 1 × 107 CFU mL-1) was then coated on 1 kg of non-cured vanilla pods that was found to ferment and colonize vanilla. PCA results revealed distinguished bacterial communities of fermented vanilla and the control group, suggesting colonization of vanilla. Phylogenetic analysis showed that ZN-S10 was the dominant Bacillus genus member and narrowly correlated to B. velezensis EM-1 and B. velezensis PMC206-1, with 78% and 73% similarity, respectively. The bacterial taxonomic profiling of cured V. planifolia had a significant relative abundance of Firmicutes, Proteobacteria, Cyanobacteria, Planctomycetes, and Bacteroidetes phyla according to the predominance. Firmicutes accounted for 55% of the total bacterial sequences, suggesting their colonization and effective fermentation roles in curing vanilla.

Preparation and evaluation of polyphenol derivatives as potent antifouling agents: addition of a side chain affects the biological activity of polyphenols

In this study, eight polyphenol derivatives were prepared to serve as green antifoulants. Polyphenol derivatives, which can hinder the growth of bacteria and algae and decrease the adhesion of some marine organisms, showed good AF activity; in particular, the activities of these derivatives were much higher than those of the corresponding polyphenols. The antibacterial rates of the products (20 μg ml^-1) exceeded 88%. Moreover, the anti-algal rates of compounds a3, b1, b2, b3 and b4 (15 μg ml^-1) were over 57% at 240 h, but these compounds showed low toxicity, and the 120 h EC₅₀ values were > 6.60 μg ml^-1. In addition, there were fewer marine microorganisms on the test panel than on the control. The above results show that some polyphenol derivatives possess relatively high antibacterial, anti-algal, and AF activity; more notably, the addition of chlorine atoms and amide groups can further increase the activity of these derivatives.

Mexican Sage (Salvia officinalis) Extraction Using Factorial Design and Its Effect on Chemical and Antibacterial Properties

The essential oils (EOs) extracted by hydrodistillation (HYDRO) and steam distillation (SD) from Mexican Salvia officinalis L were analyzed for yield, chemical composition (GC-MS), particle morphology (SEM), antioxidant activity (ABTS), and antibacterial activity against Enterobacter agglomerans, Citrobacter freundii, Salmonella sp, E. coli, and Pseudomonas aeruginosa. The influence of the factors (method, quantity, and sample) was evaluated using a 23 full factorial design, Pareto chart, normal probability plot, main effects, and interaction plots in variance analysis on yield and antioxidant activity. The quantity, methods, sample, and the methods × sample and methods × quantity interactions were the most significant factors on yield (%). The sample, methods, and quantity × sample interaction were significant for antioxidant activity. EO yields were between 0.35 and 1.27 (% w/w), and the highest value was obtained by the HYDRO method using 50 g of whole sage leaves. The antioxidant activity values were in the range of 2.35 to 3.44 mg Trolox equivalent/g. Camphor, limonene, camphene, and caryophyllene were the main compounds identified. Micrographs of sage leaves showed relevant changes in the structure after extraction. The antibacterial activity was confirmed with the inhibition diameter and inhibition percentage of all bacteria, and P. aeruginosa was the most resistant bacteria. Finally, S. officinalis EO potentials can be considered an alternative natural preservative for the food and pharmaceutical industries.