Chemical and Microbiological Hazards of Dried Fishes in Bangladesh: A Food Safety Concern

Food safety along with nutrition is an important issue in the present word. Only nutritionally safe food can ensure a healthy balanced diet to consumers. Dried fish is a popular processed fishery product not only in our country, but also in many countries of the world. It is a very good source of dietary protein, lipid and minerals necessary for a healthy body. The consumers of dried fish in national and international level are losing their interest to buy dried fish due to poor quality and safety of the products. Therefore, we reviewed the state of knowledge regarding the contamination level of dried fish by heavy metals, harmful pesticides, amount of lipid oxidation, and microbial quantity and quality from several districts in Bangladesh. The data reviewed in this article revealed that several dried fishes contaminated with excess amount of heavy metals (Pb, Cd, Cr etc.), pesticide residue (dichlorodiphenyltrichloroethane, heptachlor, endrin, aldrin, dieldrin), higher degree of lipid oxidation, excess amount of total plate count and presence of highly pathogenic E. coli, Salmonella sp. Vibrio sp. were found in few dried fish that may cause substantial human health hazard after consumption. The possible factors of these hazards are traditional drying, use of illegal pesticides with higher dose, lack of maintaining proper hygiene, sanitation, packaging, storage, distribution as well as water pollution. These findings will be helpful to develop an effective quality control and assurance program for producing safe dried fishery products for domestic consumption as well as earning foreign currency.

Effect of super-chilling storage on maintenance of quality and freshness of the Pacific oyster(Crassostrea gigas)

The quality changes of shelled Pacific oysters(Crassostrea gigas)were examined in relation to the effects of superchilling storage at-1 C for 28 d by measuring changes in biochemical properties(microbial analysis,adenosine triphosphate(ATP)-related compounds,pH,free amino acids)and sensory evaluations in this study.The results indicated that microorganism growth was significantly inhibited during superchilling storage.Adenosine diphosphate(ADP)and adenosine monophosphate(AMP)accumulated while ATP rapidly decreased in the adductor muscle.ATP and ADP were the primary components in the other 3 tissues including mantle,gill,and body trunk of oysters,and they remained relatively stable over time.The pH and adenylate energy charge in the adductor muscle could be utilized as freshness indicators for shelled oysters.However,there were no significant differences(P>0.05)among the free amino acids during whole storage.According to the sensory evalu-ations,oysters could be alive and tolerated up to 21 d at-1℃storage.The study demonstrated that superchilling storage at-1℃could better maintain the eating quality of shelled oysters and the shelf life was extended to 21 d.

Effects of flash-boil shucking on biochemical,sensorial and ultrastructural properties of Yesso Scallop(Mizuhopecten yessoensis)adductor muscle during refrigeration

Scallop adductor muscle has great popularity for raw consumption in Japan,but conventionally shucking live scallops with high vitality by knife requires skill and is time-consuming.Flash-boil shucking is a convenient shucking method in sushi restaurants for live scallops.However,the effects of this treatment on the quality of its main edible part,the adductor muscle,are not clear.This study was conducted to investigate the impact of flash-boil shucking on the quality of raw-edible scallop adductor muscle,focusing on flavor-enhancing components and ultrastructure.Thermal treatment could contribute to the formation of flavor-enhancing nucleotides in the external layer of the adductor muscle.Adenosine monophosphate content increased with the boiling time,which significantly increased to 1.47±0.42μmol/g in the 30 s-boiled group compared with 0.38±0.13μmol/g in the control group(p<0.05).The rapid adenosine monophosphate accumulation after boiling resulted in a faster accumulation of inosine and hypoxanthine during subsequent refrigeration,which could bring bitterness to aquatic products.Flash-boil shucking had no discernible effect on the proportion of free amino acids relevant to the flavor of scallop adductor muscle,despite the possibility of a reduction in total free amino acids.The external layer of the scallop adductor muscle could be hardened after flash-boil shucking.At the ultrastructural level,muscle fibers tend to aggregate transversely and contract longitudinally depending on the heating time.Flash-boil shucking is ideal for consuming the raw-edible scallop adductor muscle promptly.Flash-boil shucking treatment is recommended for households,restaurants,and small factories for treating scallops with high vitality.

Evolutionary relationship of three mitten crabs(Eriocheir sp)revealed by mitogenome and 5S ribosomal DNA analysis

To reveal the evolutionary relationship of three mitten crabs(Eriocheir sinensis,E.hepuensis,and E.japonica),complete mitogenomes and nuclear 5S rDNA sequences were analyzed.Sequencing revealed that the mitogenomes analyzed shared conserved organization of the coding and non-coding regions but genetic variation was identified.Among the three mitten crabs distinct tandem repeats were identified in the mitochondrial D-loop region.The 5S gene(5S rDNA)sequence was highly conserved across the three species,whereas non-transcribed spacer(NTS)region exhibit high levels of variation including insertions,deletions and point mutations.Cluster analysis suggested that the three mitten crabs had their own independent 5S rDNA sequence variation and evolutionary pattern.Both mitogenome and 5S rDNA sequence analysis revealed significant genetic variation across the mitten crabs species.Phylogenetic analysis using mitogenome and 5S rDNA sequences demonstrated that E.japonica was relatively more distant from E.sinensis and E.hepuensis.This study extended our previous knowledge and confirmed that the three mitten crabs are likely to be genetically differentiated species.In addition,our study also provided insights into the conservation of pure natural resources of E.sinensis,an important aquaculture species.

Inhibition of citral nanoemulsion to growth,spoilage ability and Al-2/luxS quorum sensing system of Shewanella putrefaciens CN-32:a study on bacteriostasis from in vitro culture and gene expression analysis

Objectives:The bacteriostatic effects of a citral nanoemulsion against Shewanella putrefaciens CN-32(SHP CN-32)were investigated using in vitro culture and gene expression analysis,forbuilding a potential application in spoilage microorganism control and aquatic products quality maintenance.Materials and Methods:SHP CN-32 was treated by prepared citral nanoemulsion when the minimal inhibitory concentration(MIC)was verified.The growth curve,membrane integrity,scanning electron microscope(SEM)observation,biofilm formation and quorum sensing(QS)signaling molecule Al-2 content were evaluated in different MIC treatment groups(0 to 1.00 MIC).The gene expression status of SHP CN-32 in O and 0.50 MIC groups were compared using transcriptome sequencing and quantitative polymerase chain reaction(PCR).Results:The in vitro culture revealed that the citral nanoemulsion could inhibit the growth of SHP CN-32 with MIC of approximately 200μg/mL.Images of membrane integrity.SEM and biofilm formation suggested significant biological structure damage in bacteria after treatment.Meanwhile,the Qs signaling molecule Al-2 content showed a decline with increasing treatment concentration.Transcriptome sequencing and quantitative PCR revealed that the majority genes related diversified functional metabolic pathways of SHP CN-32 were downregulated at varying degree.Conclusion:A significant bacteriostasis of citral nanoemulsion against SHP CN-32 was verified via the results of growth inhibition,structural destruction,signal molecular decrease and gene expression downregulation of strains.These synergies significantly affect the characteristic expression of SHP CN-32,revealing the application potential as bacteriostat,QS inhibitor and preservative in aquatic products.