| Sargassum fusiforme(Harvey) Setchell, a kind of important economic marine algae, is rich in nutrition and has a strong effect on health care. However, unfavorable color deterioration are easily occurred during the processing and storage of Sargassum fusiforme products, which seriously restricts its economic growth by affecting the sensory quality of products and reduced the purchase desire of consumers. So it’s important and necessary to resolve the problems and keep good color quality during the process. In this paper, both color changes and physicochemical properties of Sargassum fusiforme were studied, appropriate and effective methods were explored to inhibit the browning, and the processing technology was optimized. It’s of great significance to improve the products quality and to promote the development of deep processing industry of Sargassum fusiforme.Firstly, the main nutritional components of Sargassum fusiforme were analyzed. The contents of crude protein and crude fat were 17.17, 1.03 g/100 g dry weight(DW), respectively. The content of carbohydrates was high, accounting for 58.77% of the dry weight. Sargassum fusiforme was rich in chlorophylls and total carotenoids, and the contents of total phenolic and ascorbic acid were 2.33 g/100 g DW and 19.03 mg/100 g DW, respectively. The pigments in Sargassum fusiforme were separated by thin-layer chromatography(TLC), and results showed that the major carotenoids included β- carotene, fucoxanthin, diatoxanthin, and neofucoxanthin.Secondly, different temperature-time combinations were applied to heat Sargassum fusiforme, and the color was modeled by a kinetic mechanism and analyzed using non-linear regression. Results showed that, the higher the temperature of blanching, the higher increase in hue value, but at the same time, the sooner the value started to decay. The reaction rate constants kd and kc increased with the temperature increasing, and the obtained regression coefficients R2 adj were acceptably high(>90%). The polyphenol oxidase(PPO) residual activity, CIE color parameters, contents of total phenolic and ascorbic acid were determined to study the effect of blanching on the color and nutritional quality of Sargassum fusiforme. Results showed that, the relative residual activity of PPO decreased rapidly with time, and reached to 11.32% when blanched for 60 s. The color changed significantly during blanching. Negative a* values were detected and hue values were above 90 at the early periods of blanching(< 60 s), which indicated an obvious green color. However, it gradually changed into brown when the blanching time was longer than 60 s. The contents of total phenolic, ascorbic acid, chlorophylls and total carotenoids reduced by 28.40%~42.79%, 47.14%~ 64.76%, 40.17%~59.97% and 36.44%~54.68%, respectively. Blanching treatment led to a shift of the maximum absorption peak of chlorophylls and carotenoids, and the absorbance decreased gradually with the treatment time. In general, the best blanching treatment of Sargassum fusiforme was to be blanched in boiling water for 60 s.Next, in order to obtain Sargassum fusiforme products with good quality, effect of different soaking solution on the color was studied, and the p H value and sterilization process were improved. Results showed that, blanched Sargassum fusiforme had a higher score of visual color when it had been soaked by Na2CO3 solution. The p H value of the product was maintained at about 4.46 ± 0.05, when the content of lactic acid and sugar were 0.62% and 3.72%, respectively. Under this condition, the products could meet the requirements of commercial sterilization by sterilizing in 96~100℃ hot water for 15 min, and the color and taste were also improved.Finally, the browning of Sargassum fusiforme during storage was studied, effect of different storage temperatures and packaging materials on browning degree was investigated, and changes in the content of ascorbic acid, total phenolic and reducing sugar were analyzed. Results showed that the browning degree increased slowly with time when stored at 4℃ and reduced by 10.47% when packaged with aluminum foil bag. After having stored 28 days at 45℃, the content of ascorbic acid, total phenolic and reducing sugar decreased by 37.36%, 43.81% and 13.13%, respectively. Changes in content of ascorbic acid and total phenolic showed a significant negative correlation with browning degree. Effect of different Na2S2O5 concentrations and oxidant solution on the color of products was studied. Results showed that, the browning degree of products decreased by 44.22% after 28 days storage at 45℃, when the sample was treated with 0.02% Na2S2O5 solution for 30 min. The color of Sargassum fusiforme products is better when the sample was treated by a mixed solution of 30%H2O2:NH3?H2O:H2O = 2:0.1:8, with the ratio of materials to solution being1:5 and the treatment time of 2 h. |
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