Qi He

Quality Evaluation Focusing on Tissue Fractal Dimension and Chemical Changes for Frozen Tilapia with Treatment by Tangerine Peel Extract

This work aimed to establish an effective approach to evaluate the quality of frozen fish, focusing on changes in fish tissue structure and chemical composition during storage. Fresh tilapia samples were treated by coating with tangerine peel (TP) extract and then stored at −4, −8 and −18 °C, respectively, for 40 days. The frozen fish tissues were analyzed for structural and chemical changes. Fractal dimension, which quantifies the porous structure formed in the tissue samples, texture properties including hardness and springiness, and moisture content and water activity all decreased during the storage, while the extents of lipid oxidation, measured as peroxide value and thiobarbituric acid concentration, and protein degradation, monitored with total volatile basic nitrogen and trichloroacetic acid soluble peptides, increased. The change rates of these parameters decreased with decreasing the storage temperature and by applying TP extract. A model was developed for predicting fractal dimension, which indicated the quality of preserved tilapia and thus can be used to predict the shelf life under different storage temperatures. The results demonstrated that TP extract could extend the shelf life of frozen tilapia by 35–45% by inhibiting changes in tissue structure, moisture loss, lipid oxidation and protein degradation during frozen storage.

Chemical composition and acaricidal activity of Arisaema anurans essential oil and its major constituents against Rhipicephalus microplus (Acari: Ixodidae)

This study aimed to determine the composition of essential oils from Arisaema anurans and to evaluate the acaricidal activity of the oil and its major components on the cattle tick Rhipicephalus microplus. The essential oil was characterized by high-level oxygenated terpenes and phenylpropanoids. Its major chemical compounds were found to be asarone (11.08%), cubenol (8.43%), guaiol (4.73%), eugenol (3.46%), linalool (3.41%), and α-bisabolol (3.29%). Adult immersion test revealed that the oil, asarone, and cubenol at 1.60% concentration presented oviposition reduction percentages of 36.3%, 44.2%, and 17.7%; hatching reductions percentages of 40.8%, 51.0%, and 35.1%; and final efficacy percentages of 65.0%, 73.2%, and 49.6%, respectively. Dose-dependent egg hatching inhibition activities were exhibited by the oil, asarone, and cubenol, with LC50 values (in w/v) of 0.174%, 0.180%, and 0.381%, respectively. Larval immersion test further revealed considerable larvicidal activities against R. microplus of the oil, asarone, and cubenol, with LC50 values of 0.147%, 0.115%, and 0.338%, respectively. Biochemical assay of the homogenate of R. microplus revealed multiple mechanisms of acaricidal activity of A. anurans essential oil.

A novel superchilling storage - ice glazing (SS-IG) approach using biopolymer-based composite hydrogel to delay microbiological spoilage and organic oxidation of preserved tilapia: Chitosan-catechin layers for tilapia storage

BACKGROUND Most aquatic products are highly susceptible to deterioration and microbial spoilage during storage. Cold storage is a frequently used method to preserve them. However, products preserved by traditional frozen method are prone to suffer damage. This can significantly impair the quality of the products. To solve the problem, this work established a novel superchilling storage-ice glazing (SS-IG) approach using chitosan-catechin composite material. It can maximize the postmortem quality of preserved products during storage, avoiding damage. RESULTS During storage at -1.5 ± 0.2 °C for 25 days, the SS-IG approach using 5 g L-1 chitosan and 1∼3 g L-1 catechin as IG layers can effectively enhance the postmortem quality of preserved tilapia fillets. The sensory qualities of these fillets were effectively maintained. The microbial counts in these fillets were strongly suppressed. Oxidative rancidity in these fillets was observably inhibited. Less biogenic amine was produced in these fillets. CONCLUSION The results indicated that the SS-IG with chitosan-catechin composite-ice glazing layers can be effective in maintaining the postmortem quality of tilapia fillets. This will have a wide potential application.