| ι-Carrageenan(ι-C)is a linear,anionic sulfated polysaccharides extracted from Eucheuma spinosum.It has shown excellent bioactivites such as inhibitory activity against rhinovirus and influenza virus,and is also a good raw material for preparing edible film.The two sulfuric groups make it less susceptible to monovalent cations to form gels,therefore the performance as thickening stabilizers is better than that ofκ-carrageenan and this broadens its application in the food industry.In general,the use of ι-C in food and pharmaceutical industries has being increased owing to their complex forming ability with other hydrocolloids and proteins.However,ι-C in China depends on importation for the moment.In this study,the traditional extraction process was optimized to obtain high viscosity ι-C and its basic properties were compared with the commercial ι-C.In addition,the obtained high viscosity ι-C was combined with soybean protein isolate(SPI)to form a hybrid system to investigate its forming properties and smulsifying properties.After that,the hybrid system was further used to develop a novel ι-C-SPI ice cream.The results of are as follows:(1)Extraction of the high viscosity ι-C:to improve the viscosity and yield of ι-C from Eucheuma spinosum,the KOH soaking time,cooking temperature,and cooking time were optimized at the conditions of retaining a certain gel strength and sulfuric groups.Based on the single factor experiment,the Box-Behnken center combination test was applied and the optimum extraction conditions were as folloes:KOH soaking temperature 48℃,cooking temperature 93℃,and cooking time was 3h.Uder this optimal process conditions,the yield was 29.43 ±1.15%and the viscosity of the extracted ι-C was 205.4±6.37 mPa-s,which was 3.31 times higher than the commercial one.In addition,the sulfuric group content in the high viscosity ι-C was 27.78 ± 0.58%,and the gel strength was 82.56±2.41 g/cm2.Overall,the optimum condition showed a higher yield and a better viscosity.(2)Physico-chemical properties of the high viscosity ι-C:the physico-chemical characteristics of the obtained high viscosity ι-C and the commercial ι-C were.compared by Fourier transform infrared(FT-IR)spectroscopy and rheometer.FT-IR showed that the infrared spectrum of the high viscosity ι-C is almost consistent with the commercial ι-C.Both of them showed the four characteristic peaks ofι-C,indicating the specific sulfate groups of ι-C were retained.The static rheological properties showed that both the obtained ι-C and commercial one possess the shear thinning properties,and their change trends are similar,indicting a typical non-Newtonian fluid.The dynamic rheological properties showed that the area of thixotropic loop of the high viscosity ι-C was less than the commercial one.The composite modulus(G*)of the two was in the linear range in the oscillation strain range of 0.4%-1.0%.With the increasing of the oscillation frequency,the change trend of the high viscosity ι-C in storage modulus(G’)and loss modulus(G")is similar to the commercial one.The temperature scanning results showed that the solidification point(56℃)and the melting point(56℃)of the high viscosity i-C are significantly higher than that of the commercial one(both are 32℃),indicating a better gel properties of the obtained high viscosity ι-C.(3)The foaming properties and emulsifying properties of the high viscosity ι-C and SPI hybrid system:the increasing of SPI did not significantly affect the foaming properties of the hybrid system,but it has a significant effect on the emulsifying properties.However,the increasing of the high viscosity ι-C improved both the foaming properties and emulsifying properties.At pH 4-5,the foaming properties and the emulsifying properties are the lowest,while the emulsification stability is the highest.At pH 7-8,the emulsification is the highest,while the emulsification stability is the lowest,indicating an opposite trend.NaCl did not significantly affect the foaming properties and emulsification,but it significantly affected the emulsification stability of the hybrid system.However,CaCl2 significantly delined the foaming properties but improved the emulsifying properties.In addition,a decline trend was observed in the foaming properties and emulsifying properties with the increasing in temperature.(4)The application of the high viscosity ι-C:we developed a novel ice cream containing ι-C and SPI and compared it with commercial SPI ice cream.The results showed that the novel ι-C ice cream possessed a better quality with a normal expansion rate,a better anti-melting ratio and a less hardness.This should be mainly due to the more exquisite bubble in the hybrid system of ι-C and SPI. |
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