Silver nanoparticles (AgNPs) used in this study were synthesized using pu-erh tea leaves extract with particle size of 4.06 nm. The antibacterial activity of green synthesized AgNPs against a diverse range of Gram-negative foodborne pathogens was determined using disk diffusion method, resazurin microtitre-plate assay (minimum inhibitory concentration, MIC), and minimum bactericidal concentration test (MBC). The MIC and MBC of AgNPs against Escherichia coli, Klebsiella pneumoniae, Salmonella Typhimurium, and Salmonella Enteritidis were 7.8, 3.9, 3.9, 3.9 and 7.8, 3.9, 7.8, 3.9 μg/mL, respectively. Time-kill curves were used to evaluate the concentration between MIC and bactericidal activity of AgNPs at concentrations ranging from 0×MIC to 8×MIC. The killing activity of AgNPs was fast acting against all the Gram-negative bacteria tested; the reduction in the number of CFU mL-1 was >3 Log10 units (99.9%) in 1–2 h. This study indicates that AgNPs exhibit a strong antimicrobial activity and thus might be developed as a new type of antimicrobial agents for the treatment of bacterial infection including multidrug resistant bacterial infection.
Pomegranate (Punica granatum L.) peel powder was incorporated into fish gelatin film -forming solution (FFS) to develop an active packaging film. The physical, mechanical, antioxidant and antimicrobial properties of the films were investigated. Fish gelatin film without pomegranate peel powder (PPP) was used as the control film. The water vapor permeability (WVP) of the fish gelatin films increased as the content of incorporated PPP increased. However, films with higher PPP contents exhibited higher tensile strengths (TS values), which ranged from 7.48 to 8.02 MPa. PPP significantly (p < 0.05) improved the antioxidant properties of the films in both DPPH and ABTS radical-scavenging activity tests. The film's antimicrobial activities also increased significantly (p < 0.05) after the incorporation of PPP. Staphylococcus aureus (S. aureus) was found to be the most sensitive bacterium to the active film, followed by Listeria monocytogenes (L.monocytogenes) and Escherichia coli (E. coli). The largest inhibition zone (7.00 mm) was observed for S. aureus around the film incorporated with 5% (w/w) PPP. These results revealed that fish gelatin containing PPP has great potential as an active film with antioxidant and antimicrobial properties, and thus it can help maintain the quality and prolong the shelf life of food products.
Bee bread is the bee-collected pollen with the mixture of honey and bee salivary enzymes, stored inside the bee hive. Malaysia has limited information on bee bread collected by the stingless bee Heterotrigona itama. Therefore, this study aims to determine the botanical origin and nutritional values of bee bread from H. itama. Melissopalynological analysis was performed using scanning electron microscopy (SEM) to determine the bee bread’s botanical origin. The proximate analysis, water activity, sugar profile, amino acid profile, vitamin C content, mineral content, and heavy metal content of the bee bread were analyzed. From the results obtained, Bidens pilosa was found in bee bread from all sampling locations. Bee bread contained high protein (21.70–23.33%) and carbohydrate (57.06–58.89%) contents. Glucose was the predominant sugar found (average 11.499 g/100 g). Eight essential amino acids were quantified, and arginine was detected the highest. The major mineral element in the bee bread was potassium (average 6705.9 mg/kg), followed by phosphorus and magnesium. Toxic metals such as lead, mercury, cadmium, and arsenic were detected but within the safe limits permitted in food. The data obtained contribute towards expanding the knowledge on the nutritional information specifically for H. itama bee bread in Malaysia.
Aflatoxin contamination in foods is a global concern as they are carcinogenic, teratogenic and mutagenic compounds. The aflatoxin-producing fungi, mainly from the Aspergillus section Flavi, are ubiquitous in nature and readily contaminate various food commodities, thereby affecting human’s health. The incidence of aflatoxigenic Aspergillus spp. and aflatoxins in various types of food, especially raw peanuts and peanut-based products along the supply chain has been a concern particularly in countries having tropical and sub-tropical climate, including Malaysia. These climatic conditions naturally support the growth of Aspergillus section Flavi, especially A. flavus, particularly when raw peanuts and peanut-based products are stored under inappropriate conditions. Peanut supply chain generally consists of several major stakeholders which include the producers, collectors, exporters, importers, manufacturers, retailers and finally, the consumers. A thorough examination of the processes along the supply chain reveals that Aspergillus section Flavi and aflatoxins could occur at any step along the chain, from farm to table. Thus, this review aims to give an overview on the prevalence of Aspergillus section Flavi and the occurrence of aflatoxins in raw peanuts and peanut-based products, the impact of aflatoxins on global trade, and aflatoxin management in peanuts with a special focus on peanut supply chain in Malaysia. Furthermore, aflatoxin detection and quantification methods as well as the identification of Aspergillus section Flavi are also reviewed herein. This review could help to shed light to the researchers, peanut stakeholders and consumers on the risk of aflatoxin contamination in peanuts along the supply chain.
Peanuts are widely consumed as the main ingredient in many local dishes in Malaysia. However, the tropical climate in Malaysia (high temperature and humidity) favours the growth of fungi from Aspergillus section Flavi, especially during storage. Most of the species from this section, such as A. flavus, A. parasiticus and A. nomius, are natural producers of aflatoxins. Precise identification of local isolates and information regarding their ability to produce aflatoxins are very important to evaluate the safety of food marketed in Malaysia. Therefore, this study aimed to identify and characterize the aflatoxigenic and non-aflatoxigenic strains of Aspergillus section Flavi in peanuts and peanut-based products. A polyphasic approach, consisting of morphological and chemical characterizations was applied to 128 isolates originating from raw peanuts and peanut-based products. On the basis of morphological characters, 127 positively identified as Aspergillus flavus, and the other as A. nomius. Chemical characterization revealed six chemotype profiles which indicates diversity of toxigenic potential. About 58.6%, 68.5%, and 100% of the isolates are positive for aflatoxins, cyclopiazonic acid and aspergillic acid productions respectively. The majority of the isolates originating from raw peanut samples (64.8%) were aflatoxigenic, while those from peanut-based products were less toxigenic (39.1%). The precise identification of these species may help in developing control strategies for aflatoxigenic fungi and aflatoxin contamination in peanuts, especially during storage. These findings also highlight the possibility of the co-occurrence of other toxins, which could increase the potential toxic effects of peanuts.
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