Metabolomics approach for determining potential metabolites correlated with sensory attributes of Melaleuca cajuputi essential oil, a promising flavor ingredient

Histopathological Alterations in Gills, Liver and Kidney of African Catfish (Clarias gariepinus, Burchell 1822) Exposed to Melaleuca cajuputi Extract

This study evaluated the histopathological changes in the gill, liver and kidney of African catfish (Clarias gariepinus) intoxicated with a sub-lethal dose of Melaleuca cajuputi leaves extract (MCLE) for 96 h. The acute toxicity test has been determined previously with a value of 96-h LC50 = 127 mg/L, hence the selection of sub-lethal ranges from 60 mg/L to 160 mg/L of MCLE. Degenerative alterations were prominent in all tested organs, particularly after exposure to a high concentration of MCLE. Gill exhibited haemorrhage, epithelial lifting, lamellar disorganisation, and necrosis after exposure to a high MCLE concentration. Alterations in the liver include congestion, hydropic degeneration, and vacuolation, whereas lesions in the kidney were pyknosis, vacuolation, hydropic degeneration, and tubular necrosis. The obtained data showed that the organs experienced severe changes proportional to the increase in MCLE concentration. In addition, fish exposed to higher concentrations than the LC50 value experienced irreversible lesions. The present study suggests that the use of MCLE below the LC50 is recommended to avoid severe alterations to organs, particularly in African catfish. This study demonstrated that the use of MCLE above the LC50 promotes severe damage to the gills, liver and kidney of African catfish. However, further investigations are needed to define the causing-mechanisms underlying these effects.

Identification and Analysis of Metabolites That Contribute to the Formation of Distinctive Flavour Components of Laoxianghuang

In addition to volatile compounds, metabolites also have a great effect on the flavour of food. Fresh finger citron cannot be eaten directly because of its spicy and bitter taste, so it is made into a preserved fruit product known as Laoxianghuang (LXH). To investigate the metabolites that have an effect on the flavour of LXH, untargeted metabolomics was performed using an ultrahigh-performance liquid chromatography with tandem mass spectrometry (UPLC-MS/MS), and the metabolites of the Laoxianghuang samples from different locations in the Chaoshan area were compared and analysed. A total of 756 metabolites were identified and distinct differences were revealed among the different Laoxianghuang samples. A total of 33 differential metabolites with the most significant changes were screened through further multivariate analytical steps, and each group of samples had unique metabolites. For instance, pomolic acid had the highest content in the JG sample, while L-glycyl-L-isoleucine was rich in the QS sample. Moreover, flavonoid metabolites made the greatest contribution to the unique flavour of Laoxianghuang. The metabolic pathways involved are the biosynthetic pathways of flavonoids, isoflavonoids, flavones, and flavonols. This study can provide some creative information for distinguishing the quality differences of Laoxianghuang from the perspective of metabolites and offer preliminary theoretical support to characterise the formation of flavour substances in Laoxianghuang.

Metabolomic investigation of differences in components and taste between hon-mirin and mirin-like-seasoning

Hon-mirin (HM) is a traditional Japanese brewed seasoning used to confer sweetness and koku. Mirin-like-seasoning (MLS) is a less-expensive alternative to HM because it is not subjected to liquor tax in Japan. In this study, components and taste qualities of HM and MLS were compared by gas chromatography/mass spectrometry (GC/MS)-based metabolomics and a sensory evaluation. GC/MS analyses of foods with high sugar content are limited by contamination of the ion source and difficulty in detecting other compounds. To resolve this issue, solid-phase analytical derivatization (SPAD), in which the extraction and derivatization of analytes can be conducted in a single step, was applied as a novel sample preparation method in this study. The effect of sugar was removed by the specific absorption, derivatization, and elution of ionic compounds, such as amino acids and organic acids, with ion-exchange solid-phases. The SPAD method application enabled the detection of 15 amino acids and 14 organic acids using ion-exchange solid-phases by performing GC/MS analysis twice. These ionic compounds were not detected in mirin using conventional sample preparation. HM samples had a higher amino acid content and a lower sugar content than those of MLS samples. Furthermore, differences in sweetness and koku between HM and MLS were observed in a sensory evaluation. This is the first GC/MS-based metabolomics analysis of mirin using the SPAD method; our results provide insight into the differences between HM and MLS.

Changes in volatiles and aroma profile of andaliman (Zanthoxylum acanthopodium DC.) upon various drying techniques

Andaliman is a highly perishable Indonesian spice that could be preserved by drying. As the drying influence on andaliman volatiles and aroma profile has not been reported, this study aimed to determine the impact of five drying processes on them and the critical volatiles correlated with favorable aroma attributes. Limonene, geranial, α-pinene, sabinene, β-myrcene, (E)-2-hexenal tended to decrease while geranyl acetate, citronellal, neral tended to increase upon drying. Limonene, andaliman major volatiles, was lost considerably from 28093 µg/g solids (fresh) to 19299-21857 µg/g solids (dried). Drying significantly altered citrus, orange peel, green, warm, and lime leaf aroma. Citronellal, limonene, (Z)-β-ocimene, (E)-β-ocimene, β-citronellol, sabinene, and geranial, played substantial roles in andaliman sensory acceptability due to significant correlation to the favorable aroma attributes (citrus, orange peel, acidic). Oven drying was proposed as the ideal drying method because of its short duration, low water activity, superior overall liking, and high volatile content.

Cajuputs candy impairs Candida albicans and Streptococcus mutans mixed biofilm formation in vitro

Background: Cajuputs candy (CC), an Indonesian functional food, utilizes the bioactivity of Melaleuca cajuputi essential oil (MCEO) to maintain oral cavity health. Synergistic interaction between Candida albicans and Streptococcus mutans is a crucial step in the pathogenesis of early childhood caries. Our recent study revealed several alternative MCEOs as the main flavors in CC. The capacity of CC to interfere with the fungus-bacterium relationship remains unknown. This study aimed to evaluate CC efficacy to impair biofilm formation by these dual cariogenic microbes.

Methods: The inhibition capacity of CC against mixed-biofilm comprising C. albicans and S. mutans was assessed by quantitative (crystal violet assay, tetrazolium salt [MTT] assay, colony forming unit/mL counting, biofilm-related gene expression) and qualitative analysis (light microscopy and scanning electron microscopy).

Result: Both biofilm-biomass and viable cells were significantly reduced in the presence of CC. Scanning electron microscopy imaging confirmed this inhibition capacity, demonstrating morphology alteration of C. albicans, along with reduced microcolonies of S. mutans in the biofilm mass. This finding was related to the transcription level of selected biofilm-associated genes, expressed either by C. albicans or S. mutans. Based on qPCR results, CC could interfere with the transition of C. albicans yeast form to the hyphal form, while it suppressed insoluble glucan production by S. mutans. G2 derived from Mojokerto MCEO showed the greatest inhibition activity on the relationship between these cross-kingdom oral microorganisms (p < 0.05).

Conclusion: In general, all CC formulas showed biofilm inhibition capacity. Candy derived from Mojokerto MCEO showed the greatest capacity to maintain the yeast form of C. albicans and to inhibit extracellular polysaccharide production by S. mutans. Therefore, the development of dual-species biofilms can be impaired effectively by the CC tested.