Investigation was carried out to study kinetics of moisture loss, oil uptake and tristimulus colour during deep fat frying of Gethi (Dioscorea kamoonensis kunth) strips. Deep fat frying of Gethi strips of size 6 × 6 × 40 mm was carried out in a laboratory scale fryer at different temperatures ranging from 120 to 180 °C. The investigation showed that the moisture loss and oil uptake followed the first order kinetics equation (r > 0.95, p < 0.05). The kinetic coefficients for moisture loss and oil uptake increased significantly (p < 0.05) with temperature from 0.166 to 0.889 min(-1) and 0.139 to 0.430 min(-1) respectively. The temperature dependency of rate constants for moisture loss and oil uptake values was described using Arrhenius equation (r > 0.99, p < 0.01). The activation energies for moisture loss and oil uptake were found to be 41.53 KJ/mol and 27.12 KJ/mol respectively. The hunter colour parameters were significantly affected by frying temperature and frying time. The hunter lightness (L) value increased with respect to frying time initially, followed by decline and same trend was observed at higher temperatures of frying with elevated rate, whereas hunter redness (a) value increased significantly (p < 0.01) with time as well as temperature of frying and obeyed zero order rate equation. The temperature dependency kinetic coefficients of Hunter (a) value were described by Arrhenius equation and the energy of activation for change in hunter redness was found to be 42.41 KJ/mol (r > 0.99, p < 0.01). The other hunter colour parameters such as chroma, hue angle and total colour difference were markedly affected by frying temperature as well as frying time.

Rheological behaviour of enzyme clarified sapota (Achras sapota L.) juice at different temperatures (10 to 85°C) and total soluble solid content (10.2 to 55.6°brix) corresponding to a water activity (a w ) (0.986 to 0.865) was studied using controlled stress rheometer by coaxial cylinders attachment. The rheological parameter shear stress (Pa) was measured upto a shear rate of 1,000 s . The investigation showed that the enzyme clarified sapota juice and its concentrates behaved like a Newtonian liquid and the viscosity (η) values were in the range 4.340 to 56.418 mPa s depending upon temperature and concentration studied. The temperature dependency of viscosity of enzyme clarified sapota juice was described by Arrhenius equation (r >0.94) and activation energy (E a ) for viscous flow was in the range 5.218 to 25.439 KJ/mol depending upon concentration. The effect of total soluble solid content on flow activation energy was described by exponential relationship (r > 0.95, rmse% <13.5, p <0.01) and that of water activity was described by power law relation (r >0.99, rmse% <5.80, p <0.01). The effect of total soluble solid content on viscosity of enzyme clarified sapota juice followed second order exponential type relationship (r >0.99, rmse%<3.53) at the temperature used. The effect of water activity on viscosity of enzyme clarified sapota juice followed power law equation (r >0.98, rmse%< 4.38). A single equation representing combined effect of temperature and total soluble solid content/water activity on viscosity of enzyme clarified sapota was established.

The effect of pH, sucrose and ammonium sulphate concentrations on the production of nata-de-coco, a form of bacterial cellulose, by Acetobacter xylinum was studied. Comparisons for physical properties like thickness, wet weight, water-holding capacity (WHC), moisture content and hardness, a textural parameter were done on nata-de-coco grown in tender coconut water medium supplemented with varying concentrations of sucrose and ammonium sulphate at different pH values. The results were analysed by fitting a second-order polynomial regression equation. Response surface methodology was used to study the effect of the three variables. The study showed that A. xylinum could effectively use sucrose as the sole carbon source in coconut water medium and that cellulose production was more dependent on pH than either sucrose or ammonium sulphate concentrations. Maximum thickness of nata was obtained at pH 4.0 with 10% sucrose and 0.5% ammonium sulphate concentrations. These conditions also produced good quality nata-de-coco with a smooth surface and soft chewy texture. The study will enable efficient utilization of coconut water, a hitherto wasted byproduct of coconut industry and will also provide a new product dimension to the aggrieved coconut farmers who are not getting the right price for their product.

Manjunatha S.S., Raju P.S., Bawa A.S. (2012): Modelling the rheological behaviour of enzyme clarified lime (Citrus aurantifolia L.) juice concentrate. Czech J. Food Sci., 30: 456-466.The rheological behaviour of enzyme clarified Lime (Citrus aurontifolia L.) juice was studied as a function of the total soluble solid (TSS) content (7.3-55.7°Brix), corresponding water activity (a w ) (0.985-0.831) at different temperatures o C) using co-axial controlled stress rheometer. The rheological parameter shear stress was measured up to the shear rate of 600 s -1 . The investigation showed that the enzyme clarified lime juice and its concentrate behaved like a Newtonian fluid with the viscosity (η) being in the range 3.964 to 50.290 mPa s depending upon the concentration and temperature used. The temperature dependency on the viscosity of lime juice was described by Arrhenius equation (r > 0.99) and the activation energy (E a ) of viscous flow was in the range 4.151 to 26.050 kJ/mol depending upon the total soluble solids content. The effect of total soluble solid content on the flow activation energy was described by exponential type equation (r > 0.98) and that of water activity was described by both the power law and exponential equations (r > 0.99). The effect of total soluble solid content on the viscosity of lime juice followed the second order exponential equation (r > 0.99) at the temperature used. The effect of water activity on the viscosity was described by both the power law and exponential type relationship (r > 0.97). The equations relating to the combined effect of temperature and total soluble solids content/water activity on the viscosity of enzyme clarified lime juice were established.

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