| Global fishery production results in more than 20 MT leftovers being wasted or discarded annually. Fish bone is the main solid by-product from fillet and surimi processing, accounting for 8-10% of total fish weight. Fish bone is rich in minerals. It is a source of low priced calcium compounds with high bioavailability. However, the majority of fish bone has been used for production of fish meal, which possesses low economic value. As so far, functional products made from fish bone with micro size, such as fish bone powder and fish bone paste, have been extensively reported. While, the information regarding NFB cannot be reached.In this study, NFB was prepared using media milling and characterized. Gelation properties of surimi made from different fish species as affected by addition of NFB were investigated. The mechanism of NFB on gel textural improvement of fish actomyosin was explored. It was anticipated to offer theoretical foundation and parameters for utilization of NFB into surimi food. The results were as follows:1. Nano fish bone powder(NFBP) made from silver carp was prepared using dry media milling. The characteristics of NFBP were investigated by LDS, FT-IR, SEM, EDS and ICP. The size and specific surface area of NFBP particle were significantly(p<0.05) affected by rotation speed, media/powder weight ratio, media diameter and milling time. The suitable milling conditions were determinded to be rotation speed at 400 rpm, ratio of media to fish bone powder at 4:1, media diameter of 2 mm and 2.5 h of milling time. Under the suitable milling conditions, the partical size of fish bone powder distrbuted in a range from 0.113 to 14.5 μm, and the total volumetric percentage of fish bone powder following in the nanometer size range was 40.64%. The average particle size and specific surface area were 1.75 μm and 7.75 m2/g, respectively. SEM result confirmed that the particle became smaller and more uniform after milling treatment. Ash(63.71%) and protein(20.52%) were the main components of NFBP, and the total calcium content was determined to be 236.90 mg/g in the dried NFBP. As NFBP particle size decreased, calcium solubility significantly increased(p<0.05), calcium content on the surface layer decreased, but the chemical compositions and structure did not change.2. NFB was prepared using high-energy wet media milling. The characteristics of NFB including particle size distribution, morphology, elemental composition, ZETA potential, calcium ion concentration and chemical structure were investigated. The suitable operational parameters of milling were determined to be 0.5 mm beads diameter, agitation speed at 3000 rpm and a filling ratio of 85%. Under these conditions, fish bone particles were downsized to nanometer scale within 2 h of milling and reached the minimum average size of 115.3 nm after 6 h of miling. NFB particles showed polyhedron crystal morphology. Milling did not change the chemical structure of NFB. NFB particles were negative charged and the absolute ZETA potential value significantly increased(p<0.05) as the particle size decreased. Atomic proportion of calcium in the NFB particles decreased(p<0.05) after milling and calcium ion concentration in the NFB suspension increased(p<0.05), indicating calcium was steadily released from the particles to the suspension.3. Gelation properties of Alaska pollock surimi as affected by addition of nanoscaled fish bone(NFB) at different levels(280 nm, 0, 0.1, 0.25, 0.5, 1 and 2%) were investigated. Breaking force and penetration distance of surimi gels after setting increased significantly(p<0.05) as NFB concentration increased up to 1%. The first peak temperature and value of G’, which is known to relate to the unfolding and aggregation of LMM, increased as NFB concentration increased. In addition, 1% NFB treatment demonstrated the highest G’ after gelation was completed. The activity of endogenous TGase in Alaska pollock surimi increased(p<0.05) as NFB calcium concentration increased. The intensity of MHCXL also increased as NFB concentration increased indicating the formation of more ε-(γ-glutamyl) lysine covalent bond by endogenous TGase and calcium ions from NFB.4. Textural and rheological properties of Pacific whiting surimi were investigated at various heating rates with the use of NFB and calcium chloride. Addition of NFB and slow heating improved gel strength significantly(p<0.05). Activity of endogenous TGase was markedly(p<0.05) induced by both NFB calcium and calcium chloride, showing an optimal temperature at 30 °C. Initial G’ increased as NFB calcium concentration increased and the same trend was maintained throughout the temperature sweep. Rheograms with temperature sweep at slow heating(1 °C/min) exhibited two peaks at 35 °C and 70 °C. However, no peak was observed during temperature sweep from 20 to 90 °C at fast heating(20 °C/min). Protein patterns of surimi gels were affected by both heating rate and NFB calcium concentration. Under slow heating, MHC intensity decreased with NFB calcium concentration, indicating formation of ε-(γ-glutamyl) lysine cross-links by TGase and NFB calcium ion.5. Properties of silver carp surimi gels prepared with two thermal treatments as affected by addition of fish bone at different particle size(22, 0.48, 0.30, 0.18 and 0.12 μm) were investigated. Breaking force and penetration distance of gels after setting significantly(p<0.05) increased as fish bone particle size decreased. While the textural values of directly cooked gel were not affected by the particle size(p>0.05). Water holding capacity and whiteness of gels also increased(p<0.05) with the decreasing of the added fish bone particle size. SEM results revealed that NFB particles(<0.5 μm) were capable of being imbedded in the gel matrices without disrupting the myofibrillar gel network. As particle size decreased, more calcium ion was released(p<0.05) from the fish bone, which increased the activity of endogenous TGase(p<0.05), resulting in formation of more MHCXL in the surimi gel.6. Properties of AM gels, such as gel strength, chemical bonds, microstructure and conformation, as affected by Ca Cl2, NFB, Hydroxyapatite(HAP) and collagen(CLG), were comparatively studied. Calcium concentrations in the control, Ca Cl2, NFB, HAP and HAP & CLG mixtures were 0.01, 15.00, 15.34, 6.60 and 6.40 mmol/L, respectively. Average particle size of NFB and HAP was not significantly different(p>0.05). Breaking force of NFB gel was not significantly(p>0.05) different with that of Ca Cl2 gel, while significantly(p<0.05) higher than that of control sample, HAP and HAP & CLG gels. Hydrophobic interaction, disulfide bond, microstructure and conformation of AM gels with 5 different mixures were not significantly(p>0.05) different. As shown in SDSPAGE gels, intensities of MHC2 band in Ca Cl2 and NFB samples were significantly higher than that of canotrl, HAP and HAP & CLG samples. Results confirmed the mechanism of NFB improving gel texture were attribute to calcium ion released from NFB, which activated TGase and catalyzed the formation of more MHC2. |
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