Microbial communities and key strains associated to banana spoilages through cultural plating and metagenomic analysis

This research investigated microbial communities associated to bananas spoilage by cultural plating and metagenomic analysis. Bananas were collected from three different sources including exported farm, domestic organic farm and marketed bananas. Bacteria and fungi on fresh through spoiled banana surfaces were determined. It was found that microbial communities observed from both methods were significantly different. Microbial communities on fresh and spoiled bananas observed from each method were relatively different. From cultural plating, bacteria observed on almost fresh bananas and spoilage, from export, domestic farms and wholesale fruits market, was Enterobacter ludwigii. Fungus, Penicillium citrinum was mainly observed from all fresh and spoiled bananas from marketed fruits. Aspergillus inflatus was mainly observed on spoiled bananas collected from export farm but was not found in domestic farm and marketed fruits. From metagenomics analysis, the most abundant bacteria on fresh and spoiled banana surface was Enterobacteriacae and Pantoea, respctively. Moesziomyces made up the largest division in both fresh and spoiled bananas. Information obtained also demonstrated that geographical factors had less impact on microbial flora associated to fruit spoilage. There was no specific microbial community pattern observed on banana collected from farms. Similar microbial profiles associated to the spoilage of banana collected form market were observed. Thus, data obtained could reinforce the importance of analytical methods for studies on the microbial ecology of banana and highlight the need for more detailed examination of this variable and its importance in post-harvest management

Potential application of immobilized Bacillus subtilis (P5-6) as bio-protective culture against Staphylococcus aureus in acidic and salted food model

This research aimed to apply bacteriocin producing strain Bacillus subtilis (P5-6) as protective culture against Staphylococcus aureus in bamboo shoot pickle. Expression of genes associated with bacteriocin activity of the B. subtilis (P5-6) was investigated. Only subtilin gene expressions were observed along with housekeeping gene BA-rpoB when co-cultured with S. aureus. B. subtilis (P5-6) protective culture was made in a simple form as dried mango pieces containing 2.5 mg/g salt with viable count at 6.25 log CFU/g and water activity (aw) at 0.49, respectively. The Protective culture was made by immobilizing cells and culture of P5-6 in freeze-dried mango pieces and drying with two-step drying process. The Minimum Inhibitory Concentration (MIC) of the protective culture was 20 AU/mg and Minimum Bactericidal Concentration (MBC) at 80 AU/mg. When applied as bio-preservative in bamboo shoot pickle, the protective culture significantly (p<0.05) reduced the level of S. aureus contamination and had no impact on this food properties. This study demonstrated the potential of P5-6 in this simple protective culture form in controlling the growth of S. aureus, therefore it could be a potential for further development as bio-preservative to enhanced safety of food products

Influence of Different Types, Utilization Times, and Volumes of Aging Barrels on the Metabolite Profile of Red Wine Revealed by ¹H-NMR Metabolomics Approach

It is well recognized that the aging process is a critical step in winemaking because it induces substantial chemical changes linked to the organoleptic properties and stability of the finished wines. Therefore, this study aimed to investigate the influence of different types, utilization times, and volumes of aging barrels on the metabolite profile of red wines, produced from Thai-grown Shiraz grapes, using a non-targeted proton nuclear magnetic resonance (1H-NMR) metabolomics approach. As a result, 37 non-volatile polar metabolites including alcohols, amino acids, organic acids, carbohydrates and low-molecular-weight phenolics were identified. Chemometric analysis allowed the discrimination of wine metabolite profiles associated with different types of aging containers (oak barrels vs. stainless-steel tanks), as well as the utilization times (2, 6 and >10 years old) and volumes (225, 500 and 2000 L) of the wooden barrels employed. Significant variations in the concentration of formate, fumarate, pyruvate, succinate, citrate, gallate, acetate, tyrosine, phenylalanine, histidine, γ-aminobutyrate, methionine and choline were statistically suggested as indicators accountable for the discrimination of samples aged under different conditions. These feature biomarkers could be applied to manipulate the use of aging containers to achieve the desired wine maturation profiles