H. Das

Effect of maltodextrin, glycerol monostearate and tricalcium phosphate on vacuum dried mango powder properties

Abstract Vacuum drying of mango pulp was carried out at various levels of maltodextrin (MD) ranging between 0.25 and 0.65 kg per kg of mango solid. Glycerol monostearate (GMS) and tricalcium phosphate (TCP) were added at the levels varying between 0.01 and 0.02 kg per kg of mango solid. MD was used to eliminate the stickiness of the mango powder and to get less hygroscopic powder. GMS was used as foam stabilizer and TCP as anticaking agents respectively. Hygroscopicity, degree of caking, dispersibility, flowability, sticky point temperature of the dry powder at 5% (db) moisture content and overall color difference between the reconstituted powder and the pulp were found out. Based on these properties of mango powder, an optimum feed mix composition of 0.43–0.57 kg MD per kg of mango solids was obtained. The optimum requirement for the TCP and GMS were found to be 0.015 kg per kg of mango solid.

Effect of extrusion process variables on in-vitro protein digestibility of fish-wheat flour blends

Abstract The effects of extrusion process variables (feed ratio, length to diameter ratio of the extruder, temperature of extrusion and screw speed) on in-vitro protein digestibility (PD) of extrudates, comprising minced fish and wheat flour, were studied. Extrusion was carried out with a developed variable length single screw cooking extruder and moisture content of the extruder feed was 35%. The extrudates showed slight increases in PD values due to extrusion. Statistical analysis using analysis of variance (ANOVA) technique showed that, among the process variables, only the effect of feed ratio and temperature of extrusion were significant (P ≤ 0·05). A first order regression equation relating PD and the process variables was also developed.

Rheological behaviour during extrusion of blends of minced fish and wheat flour

Abstract The effect of the extrusion process variables, such as length/diameter ( L D ) ratio of the extruder, feed ratio (ratio of the solids of fish and wheat flour), temperature of extrusion, and screw speed on the rheological behaviour of blends of partially dried low-cost minced fish and wheat flour were studied. A single-screw, variable-length extrusion cooker, with a barrel bore of 25 mm was developed for this purpose. Pseudoplastic behaviour was observed during extrusion. The shear rate-shear stress data can be fitted (r ≥ 0·93, p ≤ 0·01) to the power-law model. The L D ratio of the extruder affects the rheological behaviour of the food dough during extrusion, and hence, the L D ratio should also be considered as a process variable. A simple mathematical model to predict the rheological properties such as the consistency coefficient, flow behaviour index, and apparent viscosity of blends during extrusion, was proposed.

Effect of roasting process variables on in-vitro protein digestibility of bengalgram, maize and soybean.

Abstract The effect of roasting process variables (temperature and time of roasting) on in-vitro protein digestibility of roasted and ground bengalgram, maize and soybean were studied. Roasting resulted in a slight increase in the PD value. Statistical analysis using an analysis of variance technique showed that the effect of time of roasting on the PD value of bengalgram and maize was more than that of temperature of roasting. An opposite trend was observed in the case of soybean.

Performance evaluation of a thin film scraped surface evaporator for concentration of tomato pulp

Abstract A thin film scraped surface evaporator (TFSSE), similar to that of Luwas model was developed for concentration of fruit juices and pulps. The main body of the evaporator was 1.4 m high and 0.22 m in diameter. The TFSSE was evaluated for the effect of steam temperature, rotor speed and feed flow rate on water evaporation rate and overall heat transfer coefficient with water and tomato pulp as feed liquids. For water as the feed, the overall heat transfer coefficient and evaporation rate ranged within 476.9–939 W m −2 °C −1 and 14.7–30.7 kg h −1 , respectively. For tomato pulp, overall heat transfer coefficient, evaporation rate and final concentration (from 5.9% TS initial concentration) were varied between 625.6–910.9 W m −2 °C −1 , 13.22–33.72 kg h −1 and 8.02–19.21% TS, respectively. The range of operating parameters were: feed flow rate 40.8–51.0 kg h −1 , steam temperature 65–80°C and rotor speed 355 rev min −1 . The optimum process parameters for the concentration of tomato pulp at 355 rev min −1 rotor speed were found to be 40.3 kg h −1 feed flow rate and 73°C steam temperature. The optimum process parameters could give 840 W m −2 °C −1 overall heat transfer coefficient, 27 kg h −1 evaporation rate and 18% total solids. At 75°C steam temperature and 45.86 kg h −1 feed rate, the ascorbic acid and colour of tomato pulp were marginally affected.

Effect of extrusion process variables on the product texture of blends of minced fish and wheat flour

Abstract The effect of the extrusion process variables, such as length/ (L/D) ratio of the extruder, feed ratio (ratio of the solids of fish and wheat flour), temperature of extrusion, and screw speed, on the product texture, obtained by extrusion of blends of partially dried low-cost minced fish and wheat flour, were studied. A single-screw variable-length cooking extruder, with a barrel bore of 25 mm, was developed for this purpose. The heat stability of the cooked extruded rods in boiling water was assessed. The texture parameters (hardness, springiness and cohesiveness) of the cooked rods were determined and were compared with those of cooked fish, with the objective of developing a fish analogue by means of extrusion cooking. Among the process variables, an increase in L/D ratio or feed ratio increased these texture parameters; the effects of temperature of extrusion and screw speed on the texture parameters were complex in nature.

Process Modelling on a Novel Grain Roaster

Abstract A manually operated device for roasting and puffing grains by using hot sand was developed. By means of a built-in sieve, the roasted grain could be removed while retaining hot.sand within the device. The moisture diffusivity in bengalgram during roasting was estimated to be 10 × 10 −9 m 2 s −1 and the overall heat-transfer coefficient for the heating of sand with a liquefied petroleum gas was 12 W m −2 K −1 . The temperatures of the sand and the grain and sand mixture were determined by using a lumped-heat-capacity model. The grain and sand temperature at the end of roasting as predicted from the model was between 207 and 222°C, while the measured values were from 201 to 205°C. The roaster could roast 4·2–4·9 kg h −1 of bengalgram while our model predicted 4·4–5·3 kg h −1 .