M. LeMaguer

Water Sorption Properties of Yellow Globe Onion (Allium cepa L.)

Abstract Sorption isotherms of water vapor on dehydrated yellow globe onion have been obtained at 10, 30, and 45°C. B.E.T. monolayers, heats of sorption and surface areas were calculated from the isotherms. By using the surface areas obtained from the B.E.T. analysis an attempt was made to calculate thermodynamic functions such as molar entropy, and equilibrium heat of sorption. Isosteric heat of the water absorption and desorption were obtained by applying the Clausius-Clayperon equation.

Headspace Sampling Procedures for Onion (Allium cepa L.) Aroma Assessment

Abstract In order to study the effect of nutrition, irrigation, variety and dehydration on onion flavor strength, analytical procedures based on headspace sampling of volatiles were evaluated. A procedure using a porous polymer, Tenax–GC; to concentrate the headspace volatiles by trapping followed by gas chromatography with or without a liquid phase column was found to be most suitable. Reproducibility of the results required standardization of the sampling procedure. Of major importance were the extent of sample disintegration, incubation temperature, timing and the rehydration ratio of dehydrated samples. Quantitative data for the volatiles of fresh onion slices were also provided and compared with those dehydrated by a pilot–scale process.

Heat-transfer correlation for upward liquid film heat transfer with phase change : application in the optimization and design of evaporators

Abstract Data obtained previously with a climbing film evaporator (Bourgois and LeMaguer, 1983b) are used to correlate the liquid film heat-transfer coefficient as a function of the local Reynolds number, the Prandtl number and the ratio of the velocity of the vapour phase to the liquid phase. The correlation is then used to optimize the industrial evaporator described in part III (Bourgois and LeMaguer, 1984) and to show how it can be used for evaporator design purposes.

Influence of the Moisture Content on the Rate of Rehydration of Potato Granules

Abstract Three types of potato granules were studied for their ability to reabsorb water. The initial water content was shown to be a critical factor. Any value of the water content below 5.23% led to a marked increase in the rate of rehydration. Above this value no variation was observed. For processing and storage reasons a value of 8% is proposed which would satisfy both requirements of product stability and low rehydration rate required for the making of good quality french fries.