Research On The Processing Technology And Storage Stablity Of Cloudy Taro Beverage

Taro is rich in nutrition, it contains various amino acids, vitamin and mineral elements and posses the characteristics of low fat, high starch and high dietary fiber. Taro is a good food resource and it is plenty in China, the processing of taro is of low level and it is mainly sold as fresh vegetables at present. Therefore, our present work was undertaken to convert taro to new food products such as cloudy taro beverage through the application of high pressure homogenization techniques and the addition of composite stabilizer. The main research methods and results were as below:(1) Our present work evaluates the rheological properties of taro pulps at different concentrations (10%～30%). Static rheological tests showed that taro pulp has shear thinning properties, it was a pseudoplastic non-Newtonian fluid and could be fitted by Herschel-Bulkley model. Dynamic rheological tests showed that taro pulp had weak gel-like properties.(2) The effect of homogenization pressure (0～60 MPa), homogenization times (0～4 times) and homogenization temperature (20～80℃) on the suspension stability of taro pulp were investigated. The test results showed that the increase of homogenization pressure (0～30 MPa) and homogenization temperature (20～50℃) increased the suspension stability of taro pulp. However, when the homogenization pressure or temperature was higher than 40 MPa or 50℃, this would produced a destabilization of taro pulp thus causing an obvious phase separation (sedimentation and creaming). Moreover, when the homogenization times were higher than 1 cycle, this would caused a phase separation (creaming). Therefore, taro pulp homogenized at 30 MPa,50℃ and 1 cycle has the highest suspension stability.(3) To obtain the optimal composite stabilizer of cloudy taro beverage, the effect of different hydrocolloids Xanthan gum, CMC, Gellan gum, Carrageenan, Pectin, Sodium alginate and emulsifiers Sucrose fatty, Monoglyceride and Polyglyceryl fatty acid ester on the suspension stability of taro pulp were investigated. On the basis of single factor experiments, the orthogonal experiment results showed that the optimal composite stabilizer were Xanthan gum 0.10%, CMC 0.10%, Gellan gum 0.025%, Polyglyceryl fatty acid ester 0.08%, and the optimal homogenization process conditions were 35 MPa,55℃ and 1 cycle.(4) The effect of UHT (135℃,5S), boiling water sterilization (100℃,30min) and high pressure steam sterilization (121℃,15min) on the stability of cloudy taro beverage were investigated. The test results showed that the three kinds of sterilization process can make cloudy taro beverage achieve the commercial sterility requirements; Compared with other sterilization methods, UHT sterilization process has the minimum effect on the textural and rheological properties of taro beverage, and farthest keep the color and suspension stability of cloudy taro beverage.(5) Our present work evaluates the quality and microbial indicators of lab-made cloudy taro beverage. The results showed that:cloudy taro beverage was of bright white color and nice smell and delicious taste, and it was a stable and uniform emulsion, which has no sedimentation and separation. Furthermore, taro beverage was abundant in protein and dietary fiber, the microbial indicators of taro beverage meet the requirements of GB/T4789.21.(6) Our present work investigates the rheological properties, Zeta potential, centrifugal sedimentation rate, color, soluble solids content and pH changes of cloudy taro beverage during the storage under different temperature 5℃,20℃ and 37 ℃. The results showed that:after 6 month storage at 5℃, the Firmness, Cohesiveness and Viscosity coefficient of taro beverage has increased, while the Consistency of beverage has decreased; Meanwhile, the Firmness, Consistency, Cohesiveness and Viscosity coefficient of taro beverage has decreased after 6 month storage at 20℃ and 37℃. The increase of storage temperature increased the mean particle size and L, a,b value change of taro beverage, while the higher the temperature, the higher the mean particle size, the greater the degree of browning. The Zeta potential value and centrifugal sedimentation rate of taro beverage increased with the increase of storage time, while the pH and soluble solids content decreased slowly.(7) Our present work evaluates the sensory state of cloudy taro beverage after 6 month storage at different temperature 5℃,20℃ and 37℃. The results showed that:taro beverage stored at 5℃ showed the best sensory state, it was of bright color, uniform texture, delicious taste and rich taro flavor, and it was a stable suspension, which has no sedimentation and separation.