Effects Of Inorganic Salts On Gel Performance Of Fish Scale Gelatin

Gelatin is mainly obtained from the partial hydrolysis of collagen of animal skin,connective tissue, and skeleton. It is a unique commercial colloid, which is widelyapplied in food industry due to its special functional characteristics. The gelatin in themarket is mainly extracted from mammal animals’ tissue and organ, but raw materialsare limited, processing technology is complicated, and the cost of production is a littlehigh, so this kind of gelatin cannot accomplish the demands of widened market. Onthe other hand, fish scale contains a large amount of collagen, it can be used to extractgelatin, and the fish scale gelatin would replace the mammal animal gelatinpromisingly. On the other hand, the output of aquatic products is quite large in China,the utilization of byproducts from aquatic products is very helpful to environmentprotection and economic development. Gel property is the most widely usedproperties of gelatin, it includes gel strength, melting temperature and gellingtemperature, etc. Compared with mammal gelatin, the main defect of fish scalegelatin is its lower melting temperature. If this property could be improved suitably,the application of fish scale gelatin would be greatly promoted in the market.Based on this train of thought, this paper separately investigated the effects ofdifferent processing conditions on gel strength and melting temperature, and foundthe most significant factor on the aim of improving its melting point, theninvestigated the structural, rheological and thermodynamic change on cooling andheating process of the fish scale gelatin with better gel properties, primarily discussedthe gel mechanism of fish scale gelatin.This paper carried a series of experiments, and the results were as follows:1. Effects of different factors on fish scale gelatin gel performance: Effects of pH,species and concentration of inorganic salts, heating temperature and time on fishscale gelatin gel strength and melting temperature were studied, the resultsindicated that pH and inorganic salts had significant influence on fish scalegelatin gel strength and melting temperature, while the influence of heating temperature and heating time was relatively small. Synthetic study of pH andinorganic salts on fish scale gelatin gel strength and melting temperature showedthat in different pH saline solution, the addition of salts reduced gel strength,K2SO4,(NH4)2SO4and KH2PO4increased melting temperature of fish scalegelatin, while KCl and MgCl2had negative effects. The gel performance of fishscale gelatin was best when pH was9.2. Structure of fish scale gelatin in different saline solution: Structure of fish scalegelatin with different salts in pH=9was studied, the addition of KCl, MgCl2,K2SO4,(NH4)2SO4and KH2PO4disrupted the network structure of gel, theordered structure was broken, content of α-chain and β-chain was decreased, therandom coil and β-turn in dried samples was lower, the original triple helixstructure of fish scale gelatin disappeared, the apparent morphology structure wasmore loose and hole of network structure was larger, KCl and MgCl2made theparticle size of gelatin larger and distribution of particle size more concentrated,which was related with its lower melting temperature, K2SO4,(NH4)2SO4andKH2PO4made the particle size of gelatin smaller and distribution of particle sizemore dispersive, which was related with its higher melting temperature.3. The rheology effects of salts on fish scale gelatin in gelling-melting transition:When fish scale gelatin was completely melted, the storage modulus and lossmodulus as very low, the gelatin solution transformed to gel with decreasingtemperature, the storage modulus and loss modulus increased. During thetransition process, both of storage modulus and loss modulus was increaseddramatically, and then gradually flattened out. The addition of five kinds of saltsdecreased the storage modulus and loss modulus of gelatin due to the disruptionof its order structure.4. The thermology effects of salts on fish scale gelatin in gelling-melting transition:The heat flow of fish scale gelatin decreased and then increased duringgelling-melting transition, which showed a concave peak, while in the oppositetransition from melting-gelling process, heat flow increased first and thendecreased, which showed a raised peak. The addition of five kinds of saltsreduced enthalpy of fish scale gelatin, which was also related with the disruption of ordered structure.