Study of some factors affecting intensity/time characteristics of sweetness

Intensity/time plots of sweetness produced by d-glucose, d-fructose and sucrose at concentrations ranging from 2.3 to 9.2% (w/v) were recorded for solutions at 15, 22 and 35°C. The intensity ( I) and persistence ( P) power functions were applied to the results obtained with a potentiometer connected to a chart recorder similar to the sensory measurement unit recording flux (SMURF) device. Increasing the concentration of assessed samples leads to an increase of perceived intensity with a tendency to show a compression for d-fructose and sucrose and an expansion for d-glucose. Persistence increases linearly as a function of concentration for the three sugars. Only very slight modification of intensity and persistence are observed when the temperature is varied from 15 to 35°C. Intensity/time plots were also recorded at 22°C for solutions containing 5% sucrose or equisweet concentrations of d-glucose or d-fructose brought to apparent viscosities of 5, 15, 25 and 35 mPa s by addition of maltodextrins. It was found that the sweetness intensity decreases as viscosity increases for d-fructose and sucrose solutions whereas it remains constant for d-glucose. The persistence remains almost constant for the three sugars when the viscosity is varied. The effect of temperature on viscosity coefficients and hydration numbers is measured for the three sugars. A decrease in intrinsic viscosity [η], B-coefficients and hydration numbers is observed with increasing temperature whilst the apparent specific volume is increased. From the Raman spectra of water and aqueous solutions of sugars, it may be concluded that increasing the temperature leads to a lowering of the rigidity of the hydrogen bonded clusters and an increase in mobility of H 2O molecules. The increase in the size of the sugars derived from apparent specific volume (V̄ 2°) values reduces their accessibility to the receptor site. This effect is minimised as regards the perceived sweetness by the increased mobility of water. The effects of concentration, temperature and viscosity on the intensity and persistence of the sweet taste of d-glucose, d-fructose and sucrose, together with their physicochemical properties in dilute solution, suggest that the accessibility of the sweet molecule to the receptor is an important step in the taste chemoreception. This step is followed by a biochemical phenomenon involving opening of ion channels which is sensitive to the mobility of water around the site and the sweetener.