An Explanation of the Increased Efficiency of Gelatin in Ice Cream Mix When Initially Aged at 68° F

Abstract

Summary 1. Optical rotation of a 1 per cent gelatin solution was determined at various intervals of time until equilibrium was practically reached, when the following temperatures were used: 34.5°, 50°, 68°, 86°, 104° and 140° F. The optical rotation decreased as the temperature was raised. Aging at and above 104° F. did not change the optical rotation, while holding at temperatures below 104° F. increased optical rotation. The greatest change occurred during the first two hours of aging. The time required for reaching optical equilibrium increased as the temperature was lowered. 2. Initially aging a 1 per cent gelatin solution for 4 hours at a temperature range of 50° to 122° F., followed by aging at a low temperature, did not affect, after 24 and 48 hours of aging, the optical rotation when compared with aging at the low temperature (34.5° F.) only. The initial aging temperature of 254° F. decreased the optical rotation, perhaps because of a partial hydrolysis of the gelatin. 3. One per cent gelatin solutions were held at 50°, 68°, and 86° F. until optical equilibrium was attained, then cooled to 34.5° and held at this temperature until optical equilibrium was again attained. The long high initial aging temperatures had no significant effect upon the final optical rotation values when compared with aging at 34.5° F. only. All of the gelatin solutions reached optical equilibrium at 34.5° F. after approximately 2 days. 4. The optical rotation of a gelatin solution initially aged at 68° F. for four hours caught up with the control (aged only at 38° F.) at approximately the eighth hour of total aging time, but did not surpass the control upon further aging. 5. Mild agitation of the gelatin solution while at the higher initial aging temperature (68° F.) had no significant effect on optical rotation. 6. The light-scattering ability of a 1 per cent gelatin solution was lower at 68° F. than at 38° F. 7. Initially aging a 1 per cent gelatin solution for 4 hours at 68° F., followed by aging at a low temperature, increased the light-scattering ability when compared with aging at the low temperature (38° F.) only. 8. The gelatin solution initially aged at a high temperature surpassed the control (aged at 38° F. only) in Tyndall intensity immediately after cooling from 68° F. to 38° F. 9. The high initial aging temperature of 68° F. had no significant effect on the velocity of the hydrogen ion through the gelatin gel when compared with an aging temperature of 38° F. only. 10. The high initial aging temperature of 68° F. slightly decreased the velocity of chromate ions through the gelatin gel, when compared with an aging temperature of 38° F. only. 11. The high initial aging temperature of 68° F. slightly increased the protective action of gelatin, when compared with an aging temperature of 38° F. only. 12. Agitation of the gelatin solution while at the high initial aging temperature of 68° F. increased the basic viscosity when compared with an unagitated solution.