Antibacterial Mechanism of 3-Carene against the Meat Spoilage Bacterium Pseudomonas lundensis and Its Application in Pork during Refrigerated Storage

The Antibacterial Activity and Mechanisms of a Mixed Bio-Preservative on the Bacillus Stains in Crab Roe Sauce

Crab roe sauce (CRS) is prone to spoilage due to microbial contamination. Therefore, this study aimed to investigate the inhibitory effects and mechanisms of a mixed bio-preservative (0.025% ε-polylysine hydrochloride (ε-PL) + 0.01% nisin (NS) + 0.01% tea polyphenols (TPs)) on the specific spoilage bacteria (SSB) in CRS. First, the SSB in CRS were isolated and identified by 16S rRNA sequencing. Two isolates were selected as representative strains based on their enzymatic spoilage potential and spoilage capability in CRS. By comparing the inhibition zones, ε-PL, NS, and TPs were selected from five conventional bio-preservatives (ε-PL, NS, TPs, grape seed extract (GSE), and rosemary extract (RE)) to prepare the mixed bio-preservative. The results showed that the minimum inhibitory concentration (MIC) of the mixed bio-preservative against Bacillus pumilus and Bacillus subtilis was 56.3 µg/mL. The growth curves and cell viability tests revealed that the mixed bio-preservative reduced the viability of both strains. The conductivity, alkaline phosphatase activity, and nucleic acid and soluble protein leakage indicated that the mixed bio-preservative disrupted the integrity of the cell walls and membranes of the two isolates in a concentration-dependent manner. Scanning electron microscopy further confirmed the damage to the cell membranes of the two isolates by the mixed bio-preservative. Overall, the mixed bio-preservative exhibited excellently inhibitory effects on the SSB and could be a promising method for the preservation of CRS.

Development of Volatile Compounds in Raw Fermented Sausages with Reduced Nitrogen Compounds-The Effect of Tomato Pomace Addition

The aim of this study was to assess the impact of tomato pomace (TP) on the content of volatile compounds and L-carnitine and the sensory characteristics of raw fermented sausages produced with reduced nitrite. The produced sausages were divided into three experimental groups: control sample, sample with 1.5% addition of freeze-dried tomato pomace, and sample with 2.5% addition of TP. The results showed that the addition of tomato pomace significantly affected the quality of raw fermented sausages. Lower L-carnitine content was observed in samples with TP. The main groups of volatile compounds identified in fermented sausages were alcohols, aldehydes, hydrocarbons, and ketones. The addition of TP influenced the smell and taste of the sausages, which were characterized by a more intense tomato taste and smell and more intense red color compared to the control sample. Despite the influence of TP addition on some sensory features, the products were characterized by a high score of overall quality of over 7 c.u. on a 10-point scale, similar to the control sausage.

Unraveling the effective inhibition of α-terpinol and terpene-4-ol against Aspergillus carbonarius: Antifungal mechanism, ochratoxin A biosynthesis inhibition and degradation perspectives

Aspergillus carbonarius, a common food-contaminating fungus, produces ochratoxin A (OTA) and poses a risk to human health. This study aimed to assess the inhibitory activity of tea tree essential oil and its main components, Terpene-4-ol (T4), α-terpineol (αS), and 3-carene (3C) against A. carbonarius. The study showed αS and T4 were the main antifungal components of tea tree essential oil, which primarily inhibit A. carbonarius growth through cell membrane disruption, reducing antioxidant enzyme activities (catalase, peroxidase, superoxide dismutase) and interrupting the tricarboxylic acid cycle. Furthermore, αS and T4 interacted with enzymes related to OTA biosynthesis. Molecular docking and molecular dynamics show that they bound mainly to P450 with a minimum binding energy of -7.232 kcal/mol, we infered that blocking the synthesis of OTA precursor OTβ. Our hypothesis was preliminarily verified by the detection of key substances in the OTA synthesis pathway. The results of UHPLC-QTOF-MS2 analysis demonstrated that T4 achieved a degradation rate of 43 % for OTA, while αS reached 29.6 %, resulting in final breakdown products such as OTα and phenylalanine. These results indicated that α-terpinol and Terpene-4-ol have the potential to be used as naturally safe and efficient preservatives or active packaging to prevent OTA contamination.

Evaluation of biocontrol efficacy of rhizosphere Pseudomonas aeruginosa for management of Phytophthora capsici of pepper

A significant population of biocontrol microorganisms resides in the rhizosphere of plants, which can be utilized for plant disease control. To explore the potential of rhizosphere soil microorganisms as biocontrol agents against pepper blight, a bacterial strain Pa608 was screened from rhizosphere soil of pepper and identified as Pseudomonas aeruginosa through morphological characteristics and 16S rRNA sequences. The result showed that the strain Pa608 demonstrated antagonistic activity against Phytophthora capsici, effectively suppressing mycelial growth. The potted experiment showed a high control efficacy of 88.0%. Remarkably, the strain Pa608 also reduced the disease index of pepper blight in the field, resulting in control efficiencies of 74.9%. Moreover, the strain Pa608 also enhanced pepper plant height and yield. GC-MS analysis revealed the production of numerous secondary metabolites by the strain Pa608, with α-pinene displaying potent anti-oomycete activity by inhibiting P. capsici growth. In conclusion, P. aeruginosa Pa608 exhibited high biocontrol activity against P. capsici and can be utilized for the management of P. capsici in pepper cultivation.

Sodium alginate emulsion loaded with linalool: Preparation, characterization and antibacterial mechanism against Shigella sonnei

This study aimed to prepare sodium alginate-linalool emulsion (SA-LE) to overcome the low solubility of linalool and explore its inhibitory activity against Shigella sonnei. The results indicated that linalool significantly reduced the interfacial tension between SA and oil phase (p < 0.05). Droplet sizes of fresh emulsions were uniform with sizes from 2.54 to 2.58 μm. The ζ-potential was between -23.94 and -25.03 mV, and the viscosity distribution was 973.62 to 981.03 mPa·s at pH 5-8 (near neutral pH) without significant difference. In addition, linalool could be effectively released from SA-LE in accordance with the Peppas-Sahlin model, mainly described by Fickian diffusion. In particular, SA-LE can inhibit S. sonnei with a minimum inhibitory concentration of 3 mL/L, which was lower than free linalool. The mechanism can be described as damaging the membrane structure and inhibiting respiratory metabolism accompanied by oxidative stress based on FESEM, SDH activity, ATP and ROS content. These results suggest that SA is an effective encapsulation strategy to enhance the stability of linalool and its inhibitory effect on S. sonnei at near neutral pH. Moreover, the prepared SA-LE has the potential to be developed as a natural antibacterial agent to address the growing food safety challenges.

Comparative Analysis of the Floral Fragrance Compounds of Panax notoginseng Flowers under the Panax notoginseng-pinus Agroforestry System Using SPME-GC-MS

Panax notoginseng is a medicinal plant in China, the flowers of which have high medicinal value. To study the differences in the floral fragrance compounds of P. notoginseng flowers (bionic wild cultivation) from the forests of Yunnan Province, the floral fragrance compounds from four varieties of P. notoginseng flowers (four-forked seven leaves, three-forked seven leaves, four-forked five–seven leaves, and three-forked five–six leaves) were compared and analyzed via headspace solid phase microextraction combined with gas chromatography–mass spectrometry methods. A total of 53 floral fragrance compounds from the P. notoginseng flowers were divided into eight categories, mainly consisting of terpenes, alkynes, aromatic hydrocarbons, and alcohols. Moreover, high contents of 3-carene, germacrene D, (−)-α-gurjunene, valencene, (+)-γ-gurjunene, menogene, and aromandendrene were identified from the flowers of different P. notoginseng varieties. Interestingly, floral fragrance compounds such as 3-carene, valencene, aromandendrene, menogene, and (+)-γ-gurjunene were first reported in the flowers of P. notoginseng. Cluster analysis showed that P. notoginseng with four-forked and three-forked leaves clustered into two subgroups, respectively. In addition, principal component analysis showed that (+)-γ-gurjunene, (+)-calarene, copaene, 1,8,12-bisabolatriene, γ-elemene, (–)-aristolene, caryophyllene, 3-carenes, and 2,6-dimethyl-1,3,6-heptatriene can be used to distinguish the floral fragrance components of four P. notoginseng flower species. This study provides a theoretical basis for elucidating the floral fragrance compounds emitted from the flowers of different P. notoginseng varieties in an agroforestry system.