Structure break was found in shearing process of static prepared low‐sugar apple jam, which is a thixotropic and shear‐thinning fluid. In order to investigated this jam, a new nonlinear regression method of Herschel–Bulkley (H‐B) model without measuring yield stress was set up using R2 as optimizing criterion, and compared with Casson model. Dynamic yield stress was calculated using the regression of downward curve. Casson model was found fit in high shear rate (in one case, R2 0.9986, still lower than H‐B model, 0.9997). Break stress (from 113 to 497 Pa) could be largely increased by soluble solid concentration rising, and dynamic yield stress of H‐B model changed from 0.004 to 20.75 Pa, mainly depending on sugar and soluble solid concentration. Consistency index (24.50–102.3 Pa·sn) was increased with adding soluble solid and decreased with adding sugar. Flow behavior index (0.229–0.363) was increased evidently with adding pectin and sugar. Practical Applications The low‐sugar jams are more nutrition‐reasonable since they generally provide fewer calories, now short of deep research. Rheological properties are of great significance for processed food fluids. Traditional steady‐state test was applied widely in rheologic study of food fluids. However, information under flow curves could not be explored in detail because definition of yield stress was confused for a long time and the most common model of fluid, Herschel–Bulkley model, lacked suitable regression method. Additionally, upward curve was often ignored. In this work, a new simple nonlinear regression of Herschel–Bulkley model was set up without measuring yield stress investigated. Then the influences of ingredients on rheologic properties of low‐sugar apple jam could be investigated in detail. It is expected that the new method and observation would be applied by other rheologic researchers, and it is useful for finding relationships between mouth feel and indexes of Herschel–Bulkley model.
To systematically study multi-stage countercurrent process for Antarctic krill protein extracting and to optimize the multi-stage countercurrent technology, the solubility of Antarctic krill proteins after multi-step dissolution was explored firstly; multi-step extraction was investigated; and then multi-stage countercurrent system for protein extraction was carried out. In single step extraction, krill-to-water ratio and pH were chosen as 1:10 and 12.5 respectively, in order to extract more protein. In the multi-step dissolution process, the protein solubility of aqueous solution at pH 12.5 was 33.0 ± 0.8 mg/mL. Multi-step cross-flow processing testified the feasibility of multi-stage countercurrent assumption. Three-stage countercurrent method using krill-to-water ratio 1:10 extracted, 95.1 ± 0.6% protein from krill, where almost the same water as previous works. The total recovery yield of 67.9 ± 1.6% was achieved after precipitation at pH 4.5.
Commercial scale production of natural astaxanthin is currently conducted through cultivation of the green alga Haematococcus pluvialis. This study comprehensively investigated the impact of seven different light spectra on the growth, morphology and photosynthesis of H. pluvialis vegetative cells. Further, the lipidomes of vegetative H. pluvialis grown under various light spectra were qualitatively and quantitatively analyzed using liquid chromatography/mass spectrometry (LC/MS). The results showed the existence of blue light—alone or with red light—promoted cell division, while pure red light or white light enabled increased cell sizes, cellular pigment, starch and lipid contents, and biomass production. Although the photosynthetic performance of H. pluvialis measured as chlorophyll a fluorescence was not significantly affected by light spectra, the lipid profiles, particularly chloroplast membrane lipids, showed remarkable changes with light spectra. The contents of most lipid species in the blue/red light 1/2 group, which showed the fastest cell division, remained at a moderate level compared with those under other light spectra, indicating the fastest dividing cells were featured by a fine-tuned lipid profile. From biotechnical perspective, this comprehensive study can provide insights into the development of appropriate light regimes to promote the cell density or biomass of H. pluvialis mass culture.
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