The influence of additives on frozen snakehead fish surimi and the application of transglutaminase to fish cakes.

BACKGROUND: The co-product of cultured snakehead fish protein extraction is an abundant source of myofi- brillar protein, with the potential for application in the processing of frozen snakehead fish surimi. The objective of this study was to determine the influence of additives and incubation time on the quality of surimi and surimi-based products. METHODS: Cryoprotectant (a mixture of sucrose and sorbitol at a ratio of 1:1 changed from 2% to 4%), in combination with sodium tripolyphosphate (0.1, 0.15, 0.2 and 0.25%), was added to surimi during its preparation. In addition, the study also investigated the ratio of transglutaminase supplementation (0.5, 0.7 and 0.9%) and incubation time (2, 4 and 6 h) in the processing of high-quality fried fish cakes from frozen snakehead fish surimi. RESULTS: The results showed that, a combination of 3% cryoprotectant and 0.2% sodium tripolyphosphate helped maintain the quality of snakehead fish surimi after frozen storage. In the processing of fried fish cakes from frozen snakehead fish surimi, the addition of 0.7% transglutaminase (0.28 U/g surimi) with 4 h incubation significantly improved the gel properties of the product. CONCLUSIONS: It is necessary to have appropriate additives and incubation time in the processing of surimi and surimi-based products from the co-product of cultured snakehead fish protein extraction.

MICROWAVE-ASSISTED EXTRACTION OF PHENOLIC COMPOUNDS FROM POLYGONUM MULTIFLORUM THUNB. ROOTS.

BACKGROUND: The aim of this study was to determine the best extraction conditions for total phenolic content (TPC) and antioxidant capacity (AC) of Polygonum multiflorum Thunb. root using microwave-assisted extraction (MAE). METHODS: The raw material used was Polygonum multiflorum Thunb. root powder. Five factors such as solvent type, solvent concentrations, solvent/material ratio, extraction time and microwave power were studied; TPC and AC values were determined by the Folin-Ciocalteu method and DPPH free radical scavenging activity measurement, respectively. In addition, studies involved assaying the HPLC test of extracts and SEM of samples. RESULTS: Optimal results pointed to acetone as the solvent, acetone concentration of 60%, solvent/material ratio of 40/1 (v/w), extraction time of 5 mins and microwave power of 127 W. TPC and AC obtained were approximates 44.3 ±0.13 mg GAE/g DW and 341.26 ±1.54 µmol TE/g DW, respectively. The effect of microwaving on the cell destruction of Polygonum multiflorum Thunb. root was observed by scanning electron microscopy (SEM). Some phenolic compounds were determined by the HPLC method, for instance, gallic acid, catechin and resveratrol. CONCLUSIONS: These factors significantly affected TPC and AC. We can use acetone as a solvent with microwave-assisted extraction to achieve the best result.