Effect of salting time on formaldehyde content of dried salted Indo-Pacific mackerel

This paper reports an analysis of formaldehyde in dried salted short mackerel (Rastrelliger brachysoma) which was intentionally added with formaldehyde compared to those that was not. The purpose was to see whether salting could cover up the illegal use of formaldehyde. Mackerel was obtained from one day fishing landed at Karangantu Fishing Port, Serang-West Java. The fish was transported in ice by road (3 hours) to the laboratory in Jakarta, and divided into two groups upon arrival. One group was soaked in 3% (w/v) formaldehyde solution for 30 minutes, while another group was not (control treatment). They were then salted in saturated brine for 12 and 24 hours at ambient temperature and sun dried subsequently to 40% moisture content or less. The formaldehyde content of raw materials was in the range of 1.4-1.7 ppm, indicating that natural formaldehyde was present in the fish. Soaking in 3% formaldehyde solution for 30 minutes significantly increased fish formaldehyde content from 1.4-1.7 to 154-157 ppm, and decreased to 42.3-58.1 after 24 and 12h salting which then dropped to 25.0-35.9 ppm after drying, respectively. Those of control showed a slight decrease after salting and increase after drying, i.e. 2.7-3.4% in the final products. This results indicate that salting could not disguise the illegal use of formaldehyde to preserve raw materials, however small amount of formaldehyde in dried salted fish could be regarded natural formaldehyde of the fish.

Preventing extinction in Rastrelliger brachysoma using an impulsive mathematical model

<abstract><p>In this paper, we proposed a mathematical model of the population density of Indo-Pacific mackerel (<italic>Rastrelliger brachysoma</italic>) and the population density of small fishes based on the impulsive fishery. The model also considers the effects of the toxic environment that is the major problem in the water. The developed impulsive mathematical model was analyzed theoretically in terms of existence and uniqueness, positivity, and upper bound of the solution. The obtained solution has a periodic behavior that is suitable for the fishery. Moreover, the stability, permanence, and positive of the periodic solution are investigated. Then, we obtain the parameter conditions of the model for which Indo-Pacific mackerel conservation might be expected. Numerical results were also investigated to confirm our theoretical results. The results represent the periodic behavior of the population density of the Indo-Pacific mackerel and small fishes. The outcomes showed that the duration and quantity of fisheries were the keys to prevent the extinction of Indo-Pacific mackerel.</p></abstract>

Occurrence of Virulence Factors and Antibiotic and Heavy Metal Resistance in Vibrio parahaemolyticus Isolated from Pacific Mackerel at Markets in Zhejiang, China

ABSTRACT Vibrio parahaemolyticus is a widespread bacterium in the marine environment and is one of the leading causes of food-derived bacterial poisoning in humans worldwide. The main objective of this study was to determine the prevalence, virulence factors, and antibiotic and heavy metal resistance profiles of V. parahaemolyticus in Pacific mackerel (Pneumatophorus japonicus) from different markets in Zhejiang Province, People's Republic of China. In total, 112 (31.11%) V. parahaemolyticus isolates were identified from 360 Pacific mackerel samples, with an extremely low occurrence of the virulence genes trh (1.79%, 2 of 112) and tdh (0%, 0 of 112). Antibiotic resistance testing revealed that most isolates showed resistance to ampicillin (96.43%, 108 of 112) and streptomycin (90.18%, 101 of 112), whereas all strains were sensitive to kanamycin, florfenicol, cefamandole, and trimethoprim-sulfamethoxazole. Furthermore, 46.43% (52 of 112) of isolates, which had 12 different phenotypes, were classified as multidrug resistant. In addition, the multiple antibiotic resistance index values of isolates were between 0.05 and 0.63, and the maximum multiple antibiotic resistance index was attributed to two isolates that exhibited resistance to 12 antibiotics. Heavy metal resistance patterns were similar among the six different markets. The majority of isolates showed resistance to Cd2+ (78.57%) and Pb2+ (51.79%), and fewer were resistant to Cu2+ (37.50%), Zn2+ (25.00%), Co2+ (9.82%), Ni2+ (6.25%), and Mn2+ (4.46%). No isolates were resistant to Cr3+. In total, 22.32% (25 of 112) of strains were multiheavy metal resistant. Furthermore, multidrug resistance and multiheavy metal resistance were found to be positively correlated in the V. parahaemolyticus strains by using Pearson's correlation analysis (P = 0.008; R = 0.925). This information will contribute to the monitoring of variations in the antibiotic and heavy metal resistance profiles of V. parahaemolyticus strains from seafood and provide insight into the appropriate use of antibiotics and the safe consumption of seafood. HIGHLIGHTS