| The key technologies of osmotic dehydration combined with fluidized bed drying of lowbush blueberries (Vaccinium angustifolium ) were studied.The lowbush blueberry (wild blueberry) plant is origin from North America. Recently many provinces and cities in China have been transplanted and cultured blueberry. The development prospects of blueberry industry in China will be all right.Osmotic dehydration is widely used for the partial removal of water from plant tissues by immersion in a hypertonic solution. It is a minima) process, carried out at relatively low process temperature without phase change. The osmotic dehydration provides advantages over conventional dehydration processes, including nutritional properties, color, flavor and aroma retention and substantial energy savings. Recently osmotic dehydration process has been received more attention by the food process industry in the world. Osmotic dehydration generally will not give a product of sufficiently low moisture content for it to be considered shelf-stable. Consequently an osmotically treated product if further processed (generally by air-, freeze-, or vacuum drying methods) to be shelf-stable, or the process is used as a pretreatment for canning, freezing, and minimal processing.The study showed that the moisture content and the water activity decreased with long duration of osmotic process, and fell down with increasing osmotic dehydrating temperature. But the decrease speed of the moisture content and the water activity in high fructose corn syrup was more quickly than in sucrose solution under three different osmotic dehydration temperatures.The moisture content of osmo-dehydrated blueberries versus osmotic dehydration time in 70±1°Brix high fructose corn syrup under different temperature was a positive linear relationship. It means that the higher of osmotic dehydrating temperature, the less of the moisture content of lowbush blueberries will be. The absolute values of slope augmented with increasing osmotic dehydrating time. The correlative coefficients of linear were 0.9626, 0.9696 and 0.9576, respectively.The moisture content of osmo-dehydrated blueberries versus osmotic dehydration time in 70±1°Brix sucrose solution at 45 ℃, 55 ℃ and 65 ℃ was a positive linear relationship. The absolute values of slope increased with increasing osmotic dehydrating time. The correlative coefficients of linear were 0.9815,0.941 and 0.9228, respectively.The water activity of osmo-dehydrated blueberries versus osmotic dehydration time in 70±l°Brix high fructose corn syrup under different temperature was a positive linear relationship. It means that the higher of osmotic dehydrating temperature, the less of the water activity of lowbush blueberries will be. The absolute values of slope increased with increasing osmotic dehydrating time.The correlative coefficients of linear were 0.9700,0.9827 and 0.97946, respectively.The water activity of osmo-dehydrated blueberries versus osmotic dehydrating time in 70±l°Brix sucrose solution at 45℃, 55℃ and 65℃ was also a positive linear relationship. The absolute values of slope of linear increased with increasing osmotic dehydrating time. The correlative coefficients of linear were 0.9565,0.9739 and 0.9732 respectively.The study showed that osmotic dehydrating temperature influenced moisture loss and solids gain of lowbush blueberries during osmotic dehydration with 70±l°Brix high fructose corn syrup or sucrose solution. The moisture loss (%ML) increased with increasing osmotic dehydrating temperature in 70±l°Brix high fructose corn syrup. It augmented rapidly in three hours, and it increased slowly and was close to limited value after three hours.The solid gain (%SG) augmented also with increasing osmotic dehydrating temperature in 70±l°Brix high fructose corn syrup. It increased linear in three hours, and it increased slowly and approach to limited value after three hours.The research detected that the solid gain in 65 ℃ was more significantly different than in 55"C and in 45 ℃. The solid gain in 45 ℃ and in 55 ℃ was not significantly different between 5 and 8 hours.According to the diffusion model, the effective moisture diffusivity (Dm) of blueberries during osmotic dehydration with 70±l°Brix high fructose corn syrup at 45℃, 55℃ and 65"C"were respectively 4.0916 x 10'10 m2/s, 5.2097 x 10"10 m2/s, 5.2366 x 10"10 m2/s. The correlative coefficients were 0.9369, 0.9203, 0.9742, respectively. The effective moisture diffusivity (Dm) of blueberries during osmotic dehydration with"70±l°Brix high fructose corn syrup at 45℃, 55^0 and 65'C were calculated by using diffusion model. They were 4.0916 x 10'10 m2/s, 5.2097 x 10'10 m2/s, 5.2366 x 10'10 m2/s, respectively. The correlative coefficients were 0.9667, 0.9652, 0.9546, respectively. The effective moisture diffusivity (Dm) of blueberries in high fructose corn syrup and in sucrose solution increased with increasing temperature. But the effective moisture diffusivity was bigger in high fructose corn syrup than in sucrose solution.The effective solids diffusivity (Ds) of blueberries during osmotic dehydration with 70±l°Brix high fructose cornsyrup at 45℃, 55'C and 65℃ were respectively 2.7740 x 10'10 m2/s, 3.6628 x 10'10 m2/s and 3.6915 x 10"10 m2/s. The correlative coefficients were 0.9057, 0.9518 and 0.96650 respectively. The effective solids diffusivity (Ds) of blueberries also showed increasing trend with temperature. The effective solids diffusivity (Ds) of lowbush blueberries during osmotic dehydration with 70±l°Brix sucrose solution at 45'C, 55'C and 65'C were respectively 1.3163 x 10'10 m2/s, 2.0814 x 1010 m2/s and 2.6915 x 1010 m2/s. The correlative coefficients were 0.9886,0.9778,0.9707, respectively. The effective solids diffusivity in high fructose corn syrup and in sucrose solution waslower than the effective moisture diffusivity under the same condition. And the effective solids diffusivity in high fructose corn syrup was higher than in sucrose solution under the same condition. The viscosity of high fructose corn syrup decreased with increasing temperature. The viscosity of high fructose corn syrup declined linear from 25*C to 50°C. The viscosity of high fructose descended slowly above 65*C and approached limited value.The average volume ratio of the osmo-dehydrated lowbush blueberries in the 70°Brix high fructose corn syrup osmotic solution decreased lightly with increasing temperature during the osmotic dehydration process. However, the relative density of osmo-dehydrated lowbush blueberries in the 70°Brix high fructose syrup osmotic solution increased lightly with increasing temperature during the osmotic dehydration process.Osmotic dehydration at vacuum pressure and pulsed vacuum was firstly applied to osmotic dehydration of lowbush blueberries. The moisture content of lowbush blueberries during osmotic dehydration at vacuum pressure fell down quickly. Osmotic dehydration at pulsed vacuum osmotic dehydration at atmosphere pressure.The effective moisture diffusivity (Dm) of lowbush blueberries during osmotic dehydration at vacuum pressure, at pulsed vacuum and at atmosphere pressure with 70±l°Brix high fructose corn syrup at 50'C were respectively 1.6777><10"9 m2/s, 1.3629xlO'9 m2/s and 0.5679*10"9 m2/s. The correlative coefficients were 0.9108,0.9243 and 0.9748, respectively.According to the value of effective moisture diffusivity, the effective moisture diffusivity could be arranged as following : VOD>PVOD>AODThe effective solids diffusivity (Ds) of lowbush blueberries during osmotic dehydration at vacuum pressure, at pulsed vacuum and at atmosphere pressure with 70±l°Brix high fructose corn syrup at 50'C were 9.1705x10"'° m2/s, 6.3919x10"'° m2/s and 5.1007><10'10 m2/s, respectively. The correlative coefficients were 0.9266, 0.984 and 0.9873, respectively.According to the value of effective solids diffusivity, the effective moisture diffusivity could be arranged as following : VOD>PVOD>AODThe moisture loss of blueberries increased with increasing temperature and drying time in the fluidized bed dryer. And the water content and the water activity of blueberries decreased with increasing temperature and drying time in the fluidized bed dryer.The effective moisture diffusivity under different conditions increased with increasing temperature in the fluidized bed dryer. The effective moisture diffusivity (Dm) of osmo-fluidized bed dehydrated blueberries at 50, 60*C, 70, 80^, 90*C were 0.7532x10''° m2/s, 0.8348* 10'l0rn2/s, 1.5122xlO'10 m2/s, 2.6589x10''° m2/s and 3.6737x10''° m2/s, respectively. The correlative coefficients were 0.9435,0.9782, 0.9836,0.9899,0.9495, respectively.The firmness of blueberries increased with increasing temperature and drying time of the fluidized bed dryer.The study revealed that osmotic dehydrating temperature influenced the content of vitamin C of lowbush blueberries during osmotic dehydration with 70±l°Brix high fructose corn syrup. The vitamin C reduction at 65*C was largest, and the vitamin C reduction at 45°C was lowest. The vitamin C reduction was more significantly different under three different temperature. The content of vitamin C after 180 minutes osmotic dehydration at 45°C, 55°C and 65°C with 70±PBrix high fructose corn syrup were 11.17±0.45mg/100g, 9.07±0.25mg/100g, and 7.38±0.36 mg/lOOg, respectively.The content of anthocyanin during osmotic dehydration at 45°C,55°C and 65°C with 70±l°Brix high fructose corn syrup decreased with increasing immersion time. The absolute values of slope of linear of anthocyanin augmented with increasing osmotic dehydrating temperature. The correlative coefficients were 0.9845,0.9746 and 0.9744, respectively.The anthocyanin of blueberries in high fructose corn syrup and in sucrose solution at 45 °C, 55°Cand 65 °C decreased gradually with increasing immersion time. The absolute values of slope of linear of anthocyanin in high fructose corn syrup augmented with increasing osmotic dehydrating temperature. The correlative coefficients of were 0.9845, 0.9746 and 0.9744, respectively. The absolute values of siope of linear of anthocyanin in sucrose solution increased with increasing osmotic dehydrating temperature. The correlative coefficients of were 0.9889, 0.9788 and 0.9891.The finding from this study suggests that the kinetic model of anthocyanin of blueberries degradation during osmotic dehydration in high fructose corn syrup accorded with first-order kinetic model.The Luminosity (L*) and the Chroma (C*) of blueberries during osmotic dehydration at 45 °C, 55 *C and 65 °C with 70±l°Brix high fructose corn syrup decreased lightly in 60 minutes immersion. After 60 minutes immersion, the Luminosity (L*) and the Chroma (C*) increased.The stability of the anthocyanin of osmo-fiuidized bed dehydrated lowbush blueberries at the storage time was studied. The result showed that the anthocyanin of osmo-fluidized bed dehydrated at 5±1 'Cwas more stable than at 22±1'C. The anthocyanin content of osmo-fluidized bed dehydrated at 5±1*C and 22±TC. after 60 days storage in the dark were 86.76% and 72.47%, respectively. The dry blueberries would storage at low temperature.The anthocyanin content of osmo-fluidized bed dried blueberries on the light decreased rapidly. The anthocyanin content of dry blueberries declined from 100% to 46.40±2.62% in 40 days. It decreased slowly after 40 days. It was 35.37±1.67% at 60 days. However, the anthocyanin content of dry blueberries decreased slowly in the dark. It remained 72.47±2.50%. The dry blueberries would...
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